Table, Distribution, Spacing, Blank: What Each Frame in a Round Separator Actually Does

Most separator content treats the machine as a motor, a screen and a lid. In reality the body is a stack of steel rings, each one a different part with a different job, and the parts catalog names are close enough to each other that buyers routinely order the wrong one. "Distribution frame," "spacing frame" and "table frame" sound like three ways of saying "the round thing the screen sits in." They aren't.

This is the guide to what each frame does, where it sits, and how to spec the right one — for Sweco, Kason, Midwestern, Russell Finex and other round separators. To go straight to the parts, browse frames and covers. (Our brand pages for Sweco, Kason, Midwestern and Russell Finex cover screens — which, as the next section explains, are a different part from the body frames this article is about.)

Frames at a glance

Every standard frame we stock, and where each one sits. Prices are on the product pages — follow the link for current pricing and availability. Custom heights, 40" diameters, 316 stainless and alternate finishes are quoted; email support@screenerking.com or call 866-265-1575.

A 60" scalping frame with an oversized 8" × 16" outspout is also available, built in 304 stainless.

Adding a deck? Budget the frame, not just the screen. A deck addition is four line items: the screen, a distribution frame, a gasket and a clamp ring. The frame is the one people leave out of the quote, and it is substantially more expensive than the spacing frame someone might order by mistake — check both product pages side by side before you budget. Screen cost depends on mesh and construction; get in touch and we'll price the whole addition in one go.

Only running one deck and just need a screen? The measure-and-order guide is the shorter read. Frames are the structure around the screen, not the screen itself.

Two different parts are both called "frames"

This is the root of most of the confusion, so it goes first.

When a supplier quotes you a "60-inch frame" for four figures and you were expecting a few hundred dollars, this is why: you asked about one part and got priced on the other. Screens are consumables you reorder; body frames are capital parts you buy once, or once per configuration change.

On most round separators the frames hold together the way the rest of the body does: each joint is squeezed shut from the outside by a clamp ring, with a gasket at each mating face, and nothing bolts vertically through the stack. Not universal, though — some designs bolt the lower frame to the table assembly specifically so it can't rotate and wear the flanges, and conversion kits exist to switch a clamp-mounted lower frame to the bolted style. Check your own machine before assuming.

Either way, every level you add multiplies the sealing faces. A screen dropped between two body frames presents two gasketed interfaces, not one, plus the clamp rings to go with them — which matters when you're pricing a deck addition, and matters a great deal more when you're chasing a leak.

The stack, bottom to top

Sweco's labeled cutaway of a Vibro-Energy round separator names the body components as: table frame, screen cloth, spacing frame, clamp ring, center tie-down, oversize discharge spout, undersize discharge spout, discharge dome — sitting on springs above the motion generator and base. Note that the cutaway shows a single-deck machine, which is why no distribution frame appears in it; the multi-deck ordering below comes from the positional definitions used across the parts catalogs.

Assembled, a machine runs in this order from the floor up:

1. Base and motion generator — the motor and eccentric weights that drive everything. Covered in adjusting eccentric weights.
2. Springs — isolate the vibrating body from the base. See springs vs. rubber mounts.
3. Table frame — the bottom of the body. Collects whatever passed every screen and discharges it.
4. Bottom screen — on a sizing stack, the finest mesh in the machine.
5. Distribution frame — only on multi-deck machines, one between each pair of screens.
6. Next screen up — on a sizing stack, coarser than the one below it. (Not universal: relief and series arrangements can run the same mesh on two decks, and scalping duty inverts the assumption.)
7. Spacing frame — above the top screen.
8. Cover — domed stainless, rigid clear plastic, or a flexible clear cover, with the feed inlet.

A ball tray, where fitted, is an extra shallow frame that sits directly under the screen it serves — so it adds a level to the stack without adding a separation.

A single-deck machine skips step 5 entirely: table frame, screen, spacing frame, cover. That's it. A real-world example — the parts list for a used 60" Sweco classic unit specifies exactly one 8" table frame and one 8" spacing frame, each with a 6" × 8" discharge spout and a clamp ring, plus one 35-mesh screen and a 60" domed cover assembly. One screen, two body frames.

Add a deck and you insert a screen and a distribution frame. That's the part people forget to quote.

How many decks can you run? Sweco's literature states that "as many as four screen decks can be incorporated in one SWECO Separator, providing simultaneous separation into five fractions." Four screens, five discharge points. If you're weighing that decision, start with how to select the number of decks and single-deck vs. multi-deck.

Three things to know before you stack tall.

Frames are vibrating mass, and that changes the machine's tuning. This is the one most often missed, and it's well documented. The OEM's published weights for a 60" machine run about 750 lb as a single-deck build and roughly 1,150 lb at five body frames — and the heaviest configuration in the table is 1,660 lb. Amplitude at a fixed eccentric-weight setting falls as vibrating mass rises, which is why the OEM says outright that fitting a heavier bottom frame means "greater horizontal and vertical amplitudes are required due to the added weight." Adding a deck is not a bolt-on: re-check your eccentric weight settings afterward, and on tall stacks confirm spring and motor capacity with us. A plant that adds a deck, sees amplitude drop on every deck, and never touches the weights will wrongly conclude the frame was the wrong part.

That added mass is also the published reason the deck count tops out where it does. A granted patent in the vibrating-separator field states it plainly — that absent a larger-than-normal motion generator, "the mass of the decks make more than three or four decks prohibitive." Note the limit is conditional on drive power rather than absolute, and the patent covers box-shaped shaker bodies as well as round ones.

Motion is not identical on every deck. The body vibrates about its center of mass, with the top weight driving horizontal motion and the lower weight tilting the machine — both of which the OEM documents. What follows from that is not documented: no manufacturer publishes deck-by-deck amplitude, and no source we could find states which deck of a tall stack performs best or why. So take the next sentence as ScreenerKing's field experience and nothing more. If you're planning a fourth deck and expecting it to carry a heavy oversize load up top, expect it to be the weakest performer in the machine. We won't dress that up with a mechanism — the honest reading is that the top deck also takes the entire feed, unstratified and at impact, which is a simpler explanation than anything to do with motion geometry. Either way, plan conservatively for the top deck and confirm on your own material.

Every frame you add is another gasketed joint. More decks means more sealing faces, and each is a chance for material to bypass a screen instead of passing through it. That's the real argument against over-stacking — not cost, but the fact that bypass is invisible until you assay your fractions. More decks buys you more fractions; it does not buy you more throughput.

Read your frame stack off the model number

This is the single most useful thing on this page, and almost nobody knows it.

On Sweco-style round separators the model number is not an arbitrary SKU. Its fields decode, in order, as separator model → unit diameter → construction material → table frame height → additional frame heights. The material code is the letter sitting between the diameter and the heights, and Sweco's published key is explicit: "C" designates Carbon Steel, "S" designates 304 Stainless Steel, "Y" designates 316L Stainless Steel and "K" designates special material.

So MX48S8886 reads:

Read the trailing numbers as a sequence of heights, not as individual digits. This is where it's easy to go wrong. Frame heights come from a small set of standard values — the heights appearing across the OEM's published dimension tables are 3, 4, 5, 6, 8, 10 and 12 inches, with 12" showing up only on the largest (72") units. Taller frames exist as build-to-order items but do not appear in the standard tables.

There is no 1-inch frame. That single fact is the whole disambiguation rule: a 1 is never a frame by itself, so it always begins a two-digit height — 10 or 12 in the published tables.

You can prove it straight off the OEM's own 60" dimension table, without taking anyone's word for it:

810 is listed as a two-frame machine. And _8106 and _888 carry the same overall height and the same weight, because both are three-frame stacks totalling 24 inches. If the digits were read individually, none of that would line up. The heights sum; the characters don't count.

A note on the material letter: the four-code key above (C / S / Y / K) is what the OEM publishes today. If your tag carries a letter that doesn't fit it, you may be reading an older or a special-order code set — send us the tag and we'll work it out.

Which means counting characters will mislead you. MX60S810 is a two-frame machine — an 8" table frame and a 10" frame above it — not three. The pattern holds across the whole table: overall height tracks the summed frame inches plus a constant that steps with frame count, and every published 60" configuration fits it.

What this buys you: before you measure anything or call anyone, the nameplate tells you your table frame height and the height of every frame above it. That's most of a frame order. On a straight sizing stack it also implies the deck count, since n body frames bracket n−1 screens — but don't lean on that, because a ball tray or a blank frame sits in the stack without adding a separation. Confirm decks by looking.

Heights also vary by machine size: roughly 3" and 5" on 18" units, 4" and 6" on 24" units, 6" on 30" units, 6" and 8" on 40" and 48" units, and on 60" units an 8" table frame with 6", 8" or 10" frames above it.

Two caveats. Different manufacturers and machine generations use different tagging conventions, so this decodes Sweco-style tags and not every nameplate you'll meet. And the OEM defers to a certified drawing over general catalog data for any specific machine — published dimensions are described as estimates. So treat the tag as a fast, reliable starting point and confirm against your drawing before you cut a purchase order. Not sure which family you have? How to identify your screener model walks it through.

Table frame — the bottom, and the tangential discharge

The table frame is the bottom frame of the body, and it attaches directly to the motor table. Everything else stacks on it. Its job is to catch the undersize that made it through every screen in the machine and route it out.

Because it's the floor of the machine, it carries the features nothing above it needs: the undersize discharge spout, a welded nut at the center for the screen tie-down on most sizes, and a discharge dome.

The dome is the detail worth knowing. A table frame is not a flat pan with a slope. The raised internal flange directs material toward the perimeter and creates a cavity that clears the motion generator's top weight spinning just underneath. Final undersize collects in the annular trough around that dome and sweeps to the spout. That's why you can't substitute a plain blank frame at the bottom of a machine — there's a moving counterweight to house.

Why "tangential" discharge. On a round separator, material does not fall straight down and it does not travel radially outward in a straight line. It spirals. Sweco's description of the mechanism explains every discharge decision on the machine: the separator "vibrates about its center of mass," and "rotation of the top weight creates vibration in the horizontal plane, which causes material to move across the screen cloth to the periphery. The lower weight acts to tilt the machine, causing vibration in the vertical and tangential planes."

So material arriving at the wall has two velocity components: radial (outward) and tangential (around the circumference). The spout sits at the periphery because that is where the outward spiral delivers oversize. What actually drives material into the spout is the radial component — the outward push — and the OEM's own lead-angle guidance shows what happens when you lose it, which is the next point.

But tangential is not automatically the right answer, and it's worth being straight about that. Material still needs some residual radial push to get into the spout. Sweco's own field guidance — a technical article by one of their service representatives — makes the point sharply: as lead angle increases from zero, radial displacement diminishes while tangential motion grows, and at a 60° lead setting the material "appears to travel only tangentially" and "will not readily discharge from the spouts at this setting." Tangential discharge suits a machine where the spiral is doing the transport. Where gravity and a steep slope are doing the transport instead — which is exactly the scalping case below — a straight radial spout is the shorter, steeper path and can be made far larger. Same reason a floor drain isn't installed sideways.

The lead angle is what sets how tight that spiral is. On Sweco's published scale: at 0° lead "material is thrown straight and gives insufficient separation"; at 15° "material begins to spiral"; at 35° you get "maximum efficient screening pattern"; and at 90° the machine "keeps oversize material from being discharged and assists in receiving maximum throughput of minus material which tends to 'ball'." That last one is worth reading twice — 90° is not a fault condition, it is a deliberate technique for material that balls up. Same machine, same frames, completely different residence time. Scales are manufacturer-specific, so read the angles against your own machine's documentation.

ScreenerKing's Table Frame – Tangential Discharge is built in 304 stainless with 316 optional, a 2B finish with continuous welds, a raised internal flange and a welded center nut, in 18" through 60". Center nut is included on 48" and 60" and optional on the smaller sizes. Extra outspouts, extended arms and seamless welds are available as custom options. If your discharge has to land somewhere the standard spout doesn't reach, the extended, oversized discharge table frame is the quoted-custom route.

Distribution frame — the one whose name misleads you

If you read one section, read this one. "Distribution frame" sounds like it distributes the incoming feed across the top screen. It does not. It sits between two screens, and its job is to re-center material that has already passed through the screen above it. Feed-side spreading is a different part class entirely — the OEM's wet-feed part is a velocity reducer, mounted at the inlet and isolated from the vibrating stack, and the patent literature treats inlet distributors as their own device family.

One naming note before we go further, because it matters when you're reading a quote: "distribution frame" is aftermarket vocabulary. Sweco's own parts lists call every body frame above the table frame a "spacing frame," regardless of what it does. The parts suppliers who stock these — and we are one — use "distribution frame" for the funnelled version because the machine builders never gave it a separate name. The part is real and so is the distinction; the label just isn't the manufacturer's.

Here's why that's necessary, and it follows directly from the spiral motion described above. A round separator screens material by making it travel — fed at the center, spiralling outward to the rim. That radial path is the deck's screening capacity.

Now think about what reaches deck two. Material passes through the top screen wherever it happens to be along that outward journey — so it arrives at the deck below spread across every radius, and a good share of it well out toward the rim. Drop it straight down and each parcel begins its traverse on the lower screen at whatever radius it fell through, which on average is a good way through the path it needed. The material that fell near the perimeter has almost no screening path left at all, and the portion that lands near that deck's discharge can short-circuit straight out.

A distribution frame fixes that. Instead of an open ring, it has an internal funnel — a sloped inner floor that falls away to an opening at the center. Material passing the upper screen lands on that slope anywhere around the circumference, slides inward, and is delivered through the center hole onto the middle of the deck below, where it starts a fresh full-radius spiral.

That mechanism is not folklore. A granted Sweco patent from 1969, describing how to add decks to a round separator, specifies an inverted pan fitted beneath an added screen "to essentially provide a feed funnel such that material passing through this additional screen is fed through the opening in this latter pan to the center of" the screen below. Different words, same part, same job.

That restored path length on every deck below the first is a large part of why a multi-deck round separator separates as well as it does. Leave the distribution frames out and the lower decks get worked mostly around their edges.

Other builders reach the same conclusion under different names. Galaxy Sivtek sells the inter-deck part as a "transfer chute" or "feed tray," describing it in almost exactly these terms: it "centralizes the material and passes it to another deck." Same physics, different vocabulary. Expect naming to shift by builder as well as by market — Gough calls the ring hardware "deck rims," Farleygreene calls the equivalent section a "gallery," while Russell Finex uses "frame" much as the US builders do. "Deck," for the screening level itself, is universal.

Distribution frames typically come with a discharge spout for that deck's oversize, a small inspection port with a plug, and a nut for the center tension device. ScreenerKing's Distribution Frame is 304 stainless with a bead-blast matte finish and the sloped inner flange, in 18" through 60", with the center nut included on 48" and 60" and optional below that. Welded seams, discharge extensions and 40" sizes are custom options.

The practical consequence: when you go from one deck to two, you are buying a screen, a distribution frame, a gasket and a clamp ring — not just a screen. Budget for the frame. And if you already run multi-deck and one deck is mysteriously under-performing while the others are fine, look at whether that deck's distribution frame is the right part, seated correctly, and not packed with material in the funnel. For the screen-ordering side of a stack, see ordering the right screen for each deck.

Spacing frame — freeboard above the top screen

A spacing frame normally goes above the top screen — which is exactly where most people don't expect it — and it does two jobs at once.

Job one: it's the top deck's outlet. A spacing frame comes standard with a discharge spout, and that spout is where the top screen's oversize leaves the machine. It isn't a passive spacer.

Job two: freeboard. The height buys you room above the mesh:

• Containment. Material fed onto a screen bounces and forms a moving bed. Without room above the mesh, feed slops toward the rim and over the edge of the top deck instead of being screened.
• Bed depth headroom. Higher feed rates mean deeper material beds. A taller spacing frame lets you run a heavier load without the bed crowding the cover.
• Access. The spacing frame is the gap you reach through to get at the top screen and the tie-down.

ScreenerKing's Spacing Frame is a plain cylindrical body ring — no dome, no sloped inner flange, a full open bore, because nothing needs redirecting above the top screen — in 304 stainless with 316 optional, heights from 4" to 12", in 18" through 60". Custom heights, 316 and a 40" diameter are available.

Where each fraction actually leaves. Once you know which frame carries which spout, a multi-deck machine stops being mysterious. On a two-deck build the three outlets map like this:

Add a deck and you add a distribution frame, which adds its own spout and its own fraction. That's the "four decks, five fractions" arithmetic in physical form.

The spacing-vs-distribution mistake, stated plainly: both are rings that add height, both cost four figures in the big sizes, and their names give you no hint which is which. Buy on function, not position alone: if the material arriving at that level needs to be put back in the middle of the screen below, you need the funnel — that's a distribution frame. If it just needs headroom and an outlet, the open ring does it.

One honest complication: plain spacing frames are used between decks in some builds, where the material genuinely doesn't need re-centering. And the OEM model-number key muddies it further by calling every non-table body frame a "spacing-frame" regardless of position — so a four-deck tag lists four "spacing frames" even though several of those positions are doing distribution work. Don't infer the part from the word on a tag or a quote; confirm what's physically in the machine and what that level has to do. If you're not sure, email photos to support@screenerking.com.

Blank frame and the ball tray

A blank frame is the plainest part in the catalog: no mesh, no discharge spout, no dome, no inspection port. Just a ring.

Two very different uses:

As a spacer or dead section. Sometimes you need height, or you need to fill a position in a stack, without adding a discharge. A blank frame does that at a fraction of a spouted frame's cost — compare our Blank Frame (no outspout) against a spacing frame of the same diameter.

As a ball tray. This is the one worth knowing. ScreenerKing's 2"-height blank frames are specifically the ball tray versions, at every diameter from 18" to 60". And the 2" height is not arbitrary — the OEM description of the arrangement is precise about it: "a coarse screen is mounted two inches below the sizing screen," elastomeric balls sit on that coarse screen, and the separator's vibration "bounces the balls against the underside of the screen cloth of the working mesh, dislodging any near-size particles." That's the most common mechanical answer to blinding, using de-blinding balls.

Note that the balls go below the working screen and strike it from underneath — not on top of it. And budget the height: a ball tray is an extra frame in the stack, so the machine gets taller by that frame's height plus its gasketed joint. Our 2" ball tray blanks are the relevant number for planning headroom.

If you want the whole assembly rather than the bare ring, the Ball Tray Assembly Kit ships as a stainless frame with a coarse 4-mesh support and the balls, in 18" through 60", with ball counts from roughly 30 to 300 depending on diameter. Mounting hardware is included on the 48" and 60" kits; tie-down hardware is separate. Note the two option pairs, because they're easy to get wrong: epoxy-bonded versus welded support mesh, and with or without a center hole — you need the center hole if the machine uses a center tie-down through that position.

Two distinctions people collapse and shouldn't:

• Ball tray support mesh is not a backing screen — tell them apart by the gap. The 4-mesh carrier in a ball tray sits about two inches below the working mesh, and that gap is the whole point: it's the space the balls travel in. A backing or support screen lies directly against the working mesh with no gap at all, purely to stop fine wire from sagging. There is a third case that sits between them — a self-cleaning "sandwich" screen, where a coarse mesh is bonded to the same tension ring with only a small gap holding balls or sliders — so the useful question is how much gap, not whether there is one. Vendors also disagree on the words: some call the ball carrier a "back-up mesh," which is the opposite of how others use the term. If you're ordering, describe the gap rather than trusting the name. ScreenerKing's own standard backing mesh is around 18 mesh.
• Balls are for coarser cuts, and there's a named failure mode if you push them fine. Kason's technical literature puts the boundary plainly: balls are "particularly useful for dislodging material in screen media coarser than 30- or 40-mesh," and "with finer meshes, the balls' high impact momentum tends to stretch the wire" — a screen-life problem, not just an efficiency one. Treat that as one manufacturer's guidance rather than an industry-wide cutoff; published recommendations vary, and Kason itself puts sliders at finer than 14-mesh, so there is real overlap where either will work. On sticky powders, ultrasonic deblinding is the gentler route. How deblinding systems work covers the full comparison.
• Balls may not clean the whole screen evenly. The same spiral motion that moves product acts on the balls too, and in our experience they tend to work the outer area harder than the center. We haven't found a manufacturer who publishes this, so treat it as a field observation — but it's worth checking your own screen for a wear pattern before assuming a ball tray solves blinding everywhere on the deck.

Scalping table frame — why it's so much bigger

A high-volume scalping table frame looks disproportionate next to a standard one: 15" tall on 48" and 60" machines where a standard table frame is 8" to 10", with an oversized radius outspout and a sloped bottom panel. The price steps up accordingly. Here's the logic, and it's counterintuitive.

Scalping is defined in the manufacturer's own literature as "removal of a small quantity of undesirable oversize particles in a high-throughput process" — protecting downstream equipment by pulling out lumps, tramp material and debris. Typical duty includes powdered milk, cereals and grains, sugar, instant coffee granules, chocolate powder, soybean flour, borax, abrasives, carbon black, metal powders and sand.

Read that definition carefully. In scalping, almost everything passes the screen. The oversize you're rejecting is the small fraction; the product is the bulk that goes through. Which means the capacity bottleneck in a scalper is not the oversize spout at the top — it's the undersize path out the bottom. Every pound of product in the process has to get through the table frame and out its discharge.

And this is not just reasoning — the OEM publishes the numbers. For a 48" separator with an 8"-diameter discharge spout running free-flowing material, a Sweco regional sales manager gives the capacities as roughly 2 cu ft/min of oversize off the top screen, 4 cu ft/min of undersize through a standard table frame, and — swapping only that bottom frame — about 9 cu ft/min of undersize through a scalping frame. Same machine, same screen, same motor. Changing that one frame more than doubles what the bottom of the machine can discharge. Read it precisely: these are discharge capacities, so the frame swap lifts the bottleneck at the outlet — it does not raise what the screen itself can separate, and oversize off the top deck stays where it was. The accompanying warning is the whole point of this section: however fast you can convey material across the screen, "it means nothing if the discharge spout isn't large enough to handle the capacity."

So if a scalper is backing up, the frame is a real candidate — not an upsell.

That is what the extra size buys, and each feature answers a different part of the problem:

• A bigger outspout so the product stream isn't choked at the exit. The 60" oversized version's outspout is an 8" wide × 16" long oval — several times the open area of a standard round spout.
• A sloped bottom panel so that volume actually drains to the spout under gravity instead of pooling or bridging. At high rates you can't rely on the spiral to sweep the pan; you need a fall line.
• A radius-oriented (radial) outspout rather than a tangential one — the shortest, steepest, straightest path out, and the geometry that lets you make the opening much bigger. This is the design trade-off flagged earlier: tangential wins when the spiral is doing the transport, radial wins when a steep slope is.
• The height to fit both the fall line and a 16"-long opening. You cannot package a steep slope and an oval that size inside a 6½" ring.
• Welded reinforcements because single-deck scalping means coarse, often heavy oversize hitting the pan at full rate.

(The capacity figures above are the OEM's, for the stated 48"/8"-spout free-flowing case, and the steep-sloped discharge is the OEM's stated design intent. The rest of the geometry reasoning — the radial spout orientation, the enlarged opening, the 15" height and the welded reinforcements — is ours; nobody publishes a "why 15 inches" note. Confirm sizing for your specific tonnage with us.)

The OEM describes the same part in the same terms: the bottom frame "is modified into what is termed a 'scalping frame' which provides a steep-sloped discharge to facilitate the material exiting the separator" — and adds a consequence worth planning for, that greater horizontal and vertical amplitudes are required due to the added weight of the scalping frame. Fitting one is not a bolt-on; budget time to re-tune the weights.

A simpler alternative to know about: if your problem is purely a high volume of undersize and you don't need the full scalping frame, Midwestern Industries offers a diverter-style frame described as useful "when dealing with a high volume of undersize," angling material directly to the downspout for quick discharge. Worth asking about before you buy the biggest part in the catalog.

ScreenerKing's High-Volume Scalping Table Frame comes in 30", 48" and 60" — 6½" tall on the 30", 15" on the 48" and 60" — in steel with welded reinforcements. There's also a 60" version with an oversized outspout, and the two 60" options carry different SKUs for the two discharge sizes, so specify which you need when you order.

On the material, and be careful here: the standard scalping frames are steel with welded reinforcements rather than stainless. For heavy, abrasive, dry, non-sanitary duty — sand, aggregates, abrasives — that's a deliberate trade of corrosion resistance for structural mass and cost, and the OEM makes the same choice, specifying carbon steel on its own scalper units. But the two 60" options differ: the oversized-outspout version is built in 304 stainless with welded reinforcements. So "the scalping frame is steel" is not a blanket truth in our own catalog — check the specific SKU. The honest rule is steel where the duty is dry and abrasive, stainless where the product or the washdown demands it.

The center nut and the tie-down

The welded center nut exists for one part: the screen tie-down. A threaded stud screws down into that nut, rises up through the screen's center, and a body or cap threads on above to clamp the screen's center down — holding it and setting its center height. 5/8"–11 is the standard thread across our tie-down assemblies, which is why the nut is a stocked frame feature rather than a custom add. Machine-side threads are not universal, though — the OEM's own parts lists show 3/8" studs on the smaller units and 5/8" from roughly 40" up, so check yours before ordering.

Here is the rule that saves a reorder, and it follows straight from that geometry: the welded center nut appears on exactly the frames that sit directly beneath a screen deck. That means the table frame (beneath the bottom screen) and the distribution frame (beneath the upper screen). Blank frames and spacing frames don't have one and don't need one — nothing anchors to them.

So if you're building out a multi-deck stack and you order a distribution frame without the center nut, you've just made the deck above it impossible to tie down. Watch the size, too: the nut is standard on 48" and 60" frames and optional on 18", 24" and 30". On the smaller machines it is something you have to ask for.

The tool-free version of the tie-down is described by the OEM as giving "the ability to tension the screen from the top," changing a screen "in a fraction of the time," rated to 220°F and built of food-grade nylon — which matches the two options in our catalog: a stainless steel tie-down assembly in 304 with optional neoprene cushion washers, and a tool-less tie-down assembly in food-safe nylon and 304 with a cone-shaped top that installs by hand. To size a stud, measure from the welded nut to the top surface of the screen and add two inches — that result is the maximum length you should order, so choose a stud at or below it.

Sequence matters, and it's the opposite of what feels natural. If your machine uses a center tie-down — plenty run without one — tighten the clamp ring first, then set the center. The OEM's manual carries it as a formal caution — "Always tighten clamp ring before tightening center tie-down assembly" — and a second manufacturer publishes the same sequence, noting that tightening the ring first is what keeps tension equal along every radius of the cloth. The mechanical logic: clamping the perimeter first fixes the screen's outer edge so the tie-down then tensions the cloth into its dished shape. Set the center first and you draw cloth inward, then lock the resulting slack in place with the ring. The OEM separately documents a loose or improperly secured clamp ring as a cause of screen fatigue, which is the failure you're avoiding. Full detail in the clamp ring guide, including torque by hardware diameter. Values vary sharply even within one manufacturer's range — Sweco specifies 5 ft-lb on an 18" ring and 32 ft-lb from 24" up — so use your own machine's manual for the number rather than a figure from the internet.

One terminology note, because technical buyers catch it: a "wagon wheel" is a screen built with an integral spoked support — used on fine mesh and larger diameters where dense material needs backing — not the center tie-down. Different parts entirely.

Materials, finish and sanitary service

Most separator body frames are built in 304 stainless — the OEM model code uses S for 304, with carbon steel and 316L as the named alternatives. 304 is the usual standard; 316 is the upgrade, and the clearest reason to specify it is chloride exposure, where the molybdenum content does real work. Note that builders generally don't publish a frame finish at all; where they do, it's a polish spec for sanitary duty. Plate arrives from the mill as 2B, and on a general-purpose frame that's what you get unless a polish is specified. Our 304 vs. 316 vs. T430 and 304 vs. 316 vs. duplex guides cover the decision properly.

Worth knowing: the manufacturer's model number encodes material choice directly — C for carbon steel, S for 304, Y for 316L, K for special material — so the alloy of your existing frames is readable off the tag alongside their heights. Note the OEM code specifies 316L rather than plain 316, and the reason is the weld, not the product. 316 and 316L are chemically identical apart from carbon; the low-carbon grade resists sensitization in the heat-affected zone, which is exactly where a continuously welded frame is vulnerable. If your concern is product contamination rather than weld corrosion, the lever is surface finish, not the L suffix. Stabilized grades such as 321, 347 and 316Ti solve the same weld problem a different way, and L grades carry slightly lower code allowables — rarely binding on a frame, but real.

What 2B actually means. The industry finish standards define 2B by its manufacturing route rather than by a measurable surface number: cold rolled, annealed, pickled or descaled, then given a final light cold-rolled pass on polished rolls, producing a smooth, moderately reflective general-purpose finish. Two consequences worth carrying into a purchase:

• 2B is a mill finish, not a polish — it's how the steel arrives, produced at the mill and not something you can match after fabrication. That's why it's the economical standard for frames rather than a downgrade.
• There is no official Ra value for 2B. The finish standard gives roughness figures for only two of its finishes — No. 3 and No. 4, at "up to" 40 and 25 µin respectively — and even those come with a warning that readings vary by instrument, lab and operator, and that the standard's finish descriptions are "not meant to be restrictive or to be used as a basis for rejection." Nothing is assigned to 2B at all. So if a spec sheet quotes you a precise Ra "for 2B," that's the fabricator's measurement, not a standard's requirement — and if you need a roughness ceiling, it has to be written into the purchase order.

And here's the part that matters if you're in food or dairy: USDA's sanitary design guidelines accept a 2B mill finish on stainless sheet as being as smooth as or smoother than a polished No. 4 finish, with no further finishing required, provided it's free of defects like pits, scratches, chips or flakes in the final fabricated form. The widely used product-contact ceiling across the 3-A, USDA and European hygiene frameworks is 32 µin (0.8 µm) Ra, and mill cold-rolled surfaces generally sit inside it. So you do not automatically need a polished frame to satisfy product-contact smoothness — though a sanitary auditor will expect it verified, not assumed. Note that builders offering a dedicated sanitary machine go further: Sweco's sanitary separator is 304 polished to a #4 finish on product-contact surfaces with a crevice-free interior and radius corner spouts, and Kason's ultra-sanitary units use radius-cornered spouts, continuous ground and polished welds and a crevice-free interior — though Kason specifies "a sanitary finish" rather than a number. Crevice-free construction is near-universal in that class; a stated #4 is not.

But there's a catch worth knowing before you specify a heavy-gauge frame. The same guidance notes that 2B on stainless plate (over 3 mm) and on bar stock is usually not as smooth as 2B on sheet, because it gets less cold rolling — and is therefore unacceptable for product-contact surfaces without additional surface preparation. A frame built heavier for strength can fail on exactly the sections that make it strong. If you're buying reinforced frames for sanitary duty, ask how the heavy sections are finished.

On bead blast, straight: bead blasting is a peening operation, not a smoothing one — it leaves a matte, textured surface rather than a polished one, and it is generally rougher than the 2B mill surface it starts from. We'd flag that we could not find measured Ra data comparing the two directly, and blast roughness swings widely with bead size and pressure, so treat this as a description of the process rather than a number. What is published is the regulatory position, and it is specific: USDA permits glass beading on product-contact surfaces only case-by-case, only where it serves a functional purpose such as product release, and to a maximum of 125 µin Ra (3.18 µm). Crucially, the same clause requires the surface be prepared to at least 32 µin Ra before the beading is applied — so beading is a treatment layered on top of a compliant surface, not an alternative to achieving one.

So treat the bead-blast matte on our distribution frames as a uniform low-glare appearance finish that hides handling marks — not as a sanitary upgrade over 2B. Where blasting is specified on stainless, glass or ceramic media is used rather than steel shot, and stainless work is kept away from carbon-steel work, because the risk being managed is free iron embedding in the surface. That said, this is not a problem in most real installations, and the guidance is explicit about why: USDA states that stainless equipment frames and exterior non-product surfaces may be glass beaded if desired. Bead blasting frame weldments is ordinary practice in this industry, sometimes done specifically to avoid cross-contamination. The distinction that matters is product contact: on a true product-contact surface under a sanitary standard, glass beading is permitted only case-by-case for a functional reason, defect-free 2B sheet is the more defensible spec, and a bead-blast surface is the one you should expect to have to verify.

Welds. This is where a spec line earns its keep, and the sanitary frameworks are unusually blunt about it. USDA's requirement for product-contact surfaces is that permanent joints "shall be continuously welded, ground, and polished to a 32 µin. (0.8 µm) Ra finish which is free of pits, folds, crevices or projections." European hygiene guidance says the same in different words — permanent metal-to-metal product-contact joints must be continuously welded and free of imperfections, direct metal-to-metal joints other than welding should be avoided because they harbour soil and micro-organisms, and internal corners want a generous radius rather than a sharp angle. On a product-contact surface, a skip or stitch weld does not satisfy either.

Frames are the exception, and it's worth knowing before someone quotes you a premium you don't need. USDA treats non-product-contact surfaces separately, and names our subject directly: non-product contact surfaces "including frame assemblies" must be free of pockets and crevices and readily cleanable, and while continuous welding achieves that, "skip or strip welding may be employed provided that intervening crevices are suitably sealed or caulked" — with the caution that such sealing is usually only a temporary measure needing periodic maintenance. So a continuously welded frame is the more defensible spec, but a skip-welded non-contact frame is not automatically non-compliant.

The reason is mechanical, not bureaucratic: a skip weld leaves a crevice that is by definition not sealed, so product gets in and cleaning solution doesn't reliably reach it — a shadow area that survives clean-down, and a classic crevice-corrosion site besides. Continuous welding plus grinding removes the crevice and brings the joint back to the smoothness of the parent sheet. Both our table frames and distribution frames offer continuous or seamless weld options for exactly this reason. It's also why welded reinforcements deserve a second thought in sanitary service: every added rib is more weld length that has to be finished, and the spout-to-frame weld is a known fatigue site as well as a hygiene one.

On wording, because it matters to a QA auditor: the precise claim for a food-contact material names its citation rather than waving at "FDA-approved." FDA does approve food additives, including substances that migrate to food from food-contact articles — but it approves substances for specified uses, not finished equipment. There is no FDA approval of a separator, a frame or a spare part, so "FDA-approved gaskets" is the wrong shape of claim even though "approve" is the right verb for the underlying substance.

For most of the rubber in a separator — gaskets and elastomer de-blinding balls in natural rubber, silicone, EPDM or Viton — the governing regulation is 21 CFR 177.2600, "Rubber articles intended for repeated use," which works by listing permitted composition substances and capping total extractives. Three caveats worth carrying: nitrile routes additionally to 21 CFR 180.22; PTFE balls fall under 21 CFR 177.1550, not 177.2600; and polyurethane balls sit under 177.2600 only if built from the two specific MDI-based resins it names, with the broader polyurethane section authorizing dry-food contact only.

One practical note that applies to most of our customers: 177.2600 exempts dry-food service from extractives testing altogether, holding those articles to good manufacturing practice instead. If you're screening dry powder, the extractives numbers aren't the test your material has to pass.

For pharma, food-safety and QA buyers: if your quality system needs material documentation, raise it with the quote rather than after delivery — what can be supplied depends on the mill run and the specific part, so it needs confirming before you order rather than assuming.

What goes wrong

For anything that isn't clearly a frame issue, work through troubleshooting vibratory screening problems and screener not separating properly first.

How to order the right frame

Five things pin down a frame order:

1. Diameter — 18", 24", 30", 48", 60" standard; 40" available on several frames as a custom size.
2. Which frame type — table, distribution, spacing, blank, or scalping table. Position in the stack decides this, per the sections above.
3. Height — read it off your model number if you're matching existing frames, remembering that the trailing numbers are heights, not single digits. Spacing frames run 4"–12".
4. Material — 304 standard, 316 for sanitary or corrosive duty, steel for heavy abrasive scalping.
5. Discharge and center nut — spout size and orientation, extra outspouts or extended arms if the standard reach doesn't fit your layout, and whether you need the welded center nut (included on 48"/60", optional below). Remember the rule: any frame sitting directly beneath a screen needs that nut.

One thing to plan for that isn't a part number: if you're adding a frame rather than replacing one, the machine gets heavier and its tuning changes. Re-check the eccentric weight settings after the rebuild, and talk to us about spring and motor capacity before you commit to a tall stack.

Frames are on the site and priced — browse frames and covers. Non-standard heights, 40" diameters, seamless welds and extended discharges are quoted as options on the individual frame pages; the custom frames collection holds the built-to-order items. For anything outside the standard grid, request a quote or call 866-265-1575. Most common sizes build fast — call for a firm date and rush options if you have a line down.

Not sure which frame you're holding? Email photos with your nameplate model to support@screenerking.com and we'll identify it. Photos first; ship the part only if the pictures are inconclusive.

And while the machine is open: if the screens coming out of that stack are worn, we remesh existing rings. Rescreening turns your old screen into your next shelf spare, which is how well-run plants avoid the next line-down — keep a spare, swap it the moment one fails, send the pulled one out to be remeshed so it becomes the next spare.

Frequently asked questions

What is the difference between a spacing frame and a distribution frame?

Internal shape, and normally position. A distribution frame has a sloped inner funnel with a center opening that re-centers material passing down from the screen above, so it lands in the middle of the next deck instead of out near the rim; it normally sits between two screens. A spacing frame is a plain open ring with a discharge spout, normally above the top screen, providing freeboard and the top deck's outlet. Buy on the function that position has to perform — plain spacing frames are sometimes used between decks where nothing needs re-centering, and the OEM model number confusingly labels every non-table frame a "spacing frame."

How do I know how many frames my separator has?

Read the model number, but read the trailing numbers as heights, not as single digits. Frame heights come from a fixed set — 3, 4, 5, 6, 8, 10 and 12 inches in the published tables — and because there are no 1-inch frames, any "1" begins a 10 or a 12. So MX48S8886 is an 8" table frame plus 8", 8" and 6" frames — four frames — while MX60S810 is only two frames, an 8" table frame and a 10" frame. Confirm against your unit's certified drawing before ordering, since published dimensions are estimates.

Do I need a distribution frame to add a second deck?

On a standard sizing build, yes. Adding a deck means a screen, a distribution frame, gaskets and a clamp ring — the frame is the part most often left out of the budget. Without the funnel, material passing the upper screen begins its travel on the lower screen at whatever radius it fell through, losing much of the screening path, and the portion landing near that deck's discharge can leave with very little screening. Also plan to re-check your eccentric weight settings afterward, because the added frame mass changes the machine's amplitude.

What is a blank frame used for?

Two things: as an inexpensive spacer or dead section where you need height but no discharge, and — in the shallow 2" heights — as the ball tray frame, creating the roughly two-inch cavity beneath the screen where de-blinding balls bounce against the mesh from underneath. A blank frame has no mesh, no spout, no dome and no inspection port, so a ball tray still needs its coarse support mesh and balls added, or buy the assembly kit.

Why is a high-volume scalping table frame so much taller than a standard one?

Because in scalping nearly all the feed passes the screen, so the bottleneck is the undersize path out the bottom rather than the oversize spout. The OEM's own figures for a 48" separator with an 8" spout on free-flowing material make the point: about 4 cu ft/min of undersize through a standard table frame versus about 9 cu ft/min through a scalping frame. The extra height, the oversized radial outspout and the sloped bottom panel exist to move that throughput out without choking. It is sized for throughput, not for rejects — and because it is heavier, expect to re-tune the eccentric weights after fitting one.

Are separator frames stainless steel?

Standard body frames are 304 stainless with a 2B finish, with 316 available for sanitary or corrosive service and 316L where ultra-low contamination matters. Heavy abrasive scalping frames are built in steel with welded reinforcements, trading corrosion resistance for structural mass — not the right choice for food or pharma duty. If your quality system needs material documentation, ask for it with the quote.

Can I put a frame from a different brand of separator on my machine?

Frames are built to fit specific diameters and body architectures, so it depends on the machine, not on the badge. We build frames to fit Sweco, Kason, Midwestern, Russell Finex and other round separators — send your nameplate model and photos and we'll confirm fit before you buy. See brand compatibility.

Order frames and covers

Table, distribution, spacing, blank and scalping table frames in 18" through 60", 304 or 316 stainless, standard or custom heights, with the discharge configuration your layout actually needs.

• Frames & covers — priced and available online, with current pricing on each product page
• Custom frames — built-to-order items; 40" diameters, non-standard heights, seamless welds and extended discharges are also quoted as options on the standard frame pages
• Request a quote or call 866-265-1575

Built to fit your machine, or we make it right.