Bearing press fit in a 3D print: hole sizes for common bearings

Draw the bearing seat 0.10 mm (0.004 in) under the bearing’s outside diameter, then add however much your printer’s holes come out small. For a 608 that is a 21.90 mm bore. The table below gives the bore for each common bearing, with every size taken from the makers’ catalogs.

What hole size do you need to press fit a bearing into a 3D print?

A press-fit bearing needs a printed bore 0.10 mm smaller than the bearing’s outside diameter (OD), or 0.05 mm of interference per side: 21.90 mm for a 608, 15.90 mm for a 625 and 25.90 mm for a 6000. Add however much your printer’s holes come out undersize, then confirm the fit on a test ring.

bore = D - 0.10 mm        D = the bearing's outside diameter
     + how much your holes print small (designed minus measured)

This is the press fit from the tolerance calculator: -0.05 mm per side with the interference put on the hole. The bearing side of the fit is already exact. SKF holds a 608’s outside diameter to 0 to -0.008 mm, so nearly all the error is in the print. Ball bearing boundary dimensions follow ISO 15, so a 608 from any maker is 8 × 22 × 7 mm.

Bearing	Bore × OD × width	Bore to model	Lip bore, at most
623	3 × 10 × 4 mm	9.90 mm	8.8 mm
624	4 × 13 × 5 mm	12.90 mm	11.2 mm
625	5 × 16 × 5 mm	15.90 mm	13.6 mm
688 (SKF 618/8)	8 × 16 × 4 mm	15.90 mm	14.6 mm
608	8 × 22 × 7 mm	21.90 mm	20 mm
6800 (SKF 61800)	10 × 19 × 5 mm	18.90 mm	17 mm
6900 (SKF 61900)	10 × 22 × 6 mm	21.90 mm	20 mm
6000	10 × 26 × 8 mm	25.90 mm	24 mm
6001	12 × 28 × 8 mm	27.90 mm	26 mm
6002	15 × 32 × 9 mm	31.90 mm	30 mm

Sizes and lip bores are from SKF’s product pages, and NSK lists its 6800 and 6900 at the same sizes. SKF’s 688-size bearing, the 618/8, is 4 mm wide. Pacamor Kubar’s shielded S688ZZ is 5 mm wide, so measure yours before you set the pocket depth.

Where the 0.10 mm comes from

• A press-fit study on 6000-2RS bearings. Researchers at the University of Kragujevac (Milenković et al., 2025) printed PETG (glycol-modified polyethylene terephthalate) seats 0.1 and 0.2 mm under the 26 mm OD on a Bambu Lab X1E. The 0.1 mm seat took about 200 N (45 lbf) to press in and 225 N to pull out. The 0.2 mm seat took about 450 N (100 lbf) in and 415 N out. Both housings kept their size through five press-and-pull cycles, and the authors call 0.1 mm “optimal” for parts that will come apart again.
• The printer’s own error. Those seats measured 25.86 and 25.78 mm, so that X1E printed both holes 0.02 to 0.04 mm small. A printer whose holes come out 0.10 mm small needs that 0.10 mm added back.
• Sovol’s starting value. Sovol, a printer maker, gives 0.05 to 0.10 mm of interference per side as the usual start for a bearing pocket and says a test coupon overrides any table.

An earlier Kragujevac test on a Creality Ender 3, also in PETG, needed up to 583 N (131 lbf) to press a 13 mm bearing into a seat drawn 0.2 mm undersize. Tighter seats cost force fast, so start at 0.10 mm.

When to go tighter or looser

It depends on whether the outer ring turns relative to the load. SKF says a ring under a rotating load creeps on a loose seat and wears it, so that ring needs an interference fit. A ring under a stationary load “does not need to have an interference fit.” JTEKT (Koyo) names pulleys and running wheels on a stationary shaft as the case where the housing needs interference.

• Printed pulley, wheel or spool hub turning on a fixed bolt: the outer ring turns with the print. Keep the full 0.10 mm.
• Printed frame holding a bearing for a spinning shaft: the outer ring stays put. A bore at the outside diameter itself (22.00 mm for a 608) is enough, and the bearing comes out again more easily. Hold it axially with a lip or a cap.

Print a test ring first

Print one short ring with three seats: D - 0.20, D - 0.10 and D. Use the same filament, layer height and orientation as the real part. Sovol says to set slicer hole compensation to zero for the coupon, or you measure the compensation instead of the printer. Keep the seat that takes the bearing under vise pressure and still lets it spin freely.

What size hole for a press fit bushing or LM8UU?

Draw a bushing’s bore at its nominal outside diameter, not under it, because the maker builds the interference into the bushing. An LM8UU linear bearing gets no interference.

Part	Bore × OD × length	Bore to model	What holds it
LM8UU linear bearing (THK LM 8 UU)	8 × 15 × 24 mm	15.00 mm	a clip, end stop or zip tie
igus iglidur G GSM-0810-08 bushing	8 × 10 × 8 mm	10.00 mm	the press fit
SKF PSM 081208 A51 sintered bronze bushing	8 × 12 × 8 mm	12.00 mm	the press fit

• igus iglidur bushings: igus makes the outside 0.1 to 0.25 mm larger than a housing bore drawn at the nominal size. That bore is ISO tolerance class H7, which at 10 mm allows 0 to 0.015 mm oversize. The bushing’s inner diameter reaches its tolerance only once pressed in. Calipers on an unpressed bushing read the oversize figure, so draw from the catalog’s 10 mm.
• When the shaft rattles in a pressed bushing: igus lists a soft housing “widened by the bearing during press-fitting” among the causes. The plastic gave way, so reprint the seat 0.10 mm smaller.
• Sintered bronze bushings: SKF gives an H7 housing and an h8 shaft for the PSM 081208 A51, so the bore is drawn at 12.00 mm.
• LM8UU: THK recommends a loose fit (H7) for its linear bushings, and a transition fit (J7, which can come out slightly tight or slightly loose) only when less clearance is needed. It says “do not rely only on a press fit” and warns that even a set screw pressing on the outer sleeve deforms it. Draw a 15.00 mm seat and correct it for holes printing small. Hold the bearing with a clip, an end stop or a zip tie, where THK uses snap rings or stopper plates.

What size shaft goes through a 3D printed bearing assembly?

A shaft that stays still can slide through the bearing; a shaft that spins with the inner ring needs a press fit. Take a 608, whose 8 mm bore SKF holds to 0 to -0.007 mm.

• A steel shaft that stays still: an idler on a fixed bolt has a stationary inner ring, and JTEKT’s fit table accepts a clearance fit there. An M8 bolt measures 7.760 to 7.972 mm over its threads (the standard 6g bolt tolerance in ASME B1.13M), so it sits 0.02 to 0.24 mm loose in the bore.
• A shaft that spins with the inner ring under a fixed load: the inner ring needs interference on the shaft (SKF and JTEKT), as on a motor shaft.
• A printed shaft: in the tolerance calculator, pick the press fit and put it on “The pin”. It returns an 8.10 mm shaft for the 8 mm bore. Subtract however much your printed pins come out large.

SKF mounts the ring with the tighter fit first. If one bearing must go onto the shaft and into the housing in one push, SKF applies the force equally to both rings.

Does a printed bearing seat need a lip or shoulder?

Yes, if anything can push the bearing along its axis. Sovol notes that a press fit resists turning but does not locate the bearing axially, so a shoulder, lip or clamp does that job.

• Pocket depth: the bearing’s width, 7 mm for a 608, with the lip at the bottom or a cap on top.
• Lip bore: no larger than the “lip bore, at most” column. That is SKF’s maximum housing abutment diameter (Da max), so the lip bears on the outer ring and clears the inner ring.
• Inside corner: keep it sharp. SKF allows at most a 0.3 mm fillet for a 608, so the ring sits flat on the lip instead of riding up a rounded corner.
• Entrance chamfer: Sovol starts at 0.3 to 0.5 mm, and igus asks for a chamfered, deburred bore. The chamfer helps the bearing start square and clears elephant’s foot when the opening faces the bed.
• Orientation: print the bore’s axis vertical. Stanford’s Lab64 rules say holes printed that way are continuous on each layer. A horizontal axis comes out less round and usually needs supports inside the seat.

Why does a bearing feel stiff after pressing it into a print?

The seat squeezes the outer ring. SKF says an interference fit compresses the outer ring and reduces the bearing’s internal clearance, the small play between balls and rings that a bearing needs to run freely. Plastic is far softer than the steel ring, so the print absorbs most of a 0.10 mm interference. Draw much tighter, or leave a high spot in the bore, and the steel takes the load.

Printed bores have high spots. SKF wants a ring supported around its whole circumference, on a seat “uninterrupted by grooves, holes or other features.” It also warns against distortion from uneven wall thickness. A printed seat has a layer seam, flat facets from the mesh and sometimes a screw hole breaking through. Keep the wall even, and move the seam off the bore where the slicer allows.

Two more causes:

• A crooked bearing. SKF puts the permissible misalignment of a single deep groove ball bearing at about 2 to 10 minutes of arc. Past that, the added noise and shorter life become noticeable. A bearing pressed in at an angle is misaligned from the start.
• Thin rings. A 6800 has the same 10 mm bore as a 6000 but a 19 mm outside diameter instead of 26 mm, so its rings are much thinner. Check that it spins freely before you go tighter than 0.10 mm.

How do you press a bearing into a 3D printed part?

Push on the outer ring only, square, with a vise or a press.

1. Clear strings and blobs from the bore, then start the bearing square by hand on the chamfer.
2. Put a socket or a flat plate on the bearing that touches the outer ring only, as Sovol advises. SKF says never to apply mounting force through the rolling elements and never to strike the rings, cage or seals directly with a hard object.
3. Squeeze it in slowly with a bench vise or an arbor press until it sits on the lip. A 26 mm bearing at 0.10 mm of interference took about 200 N (45 lbf) in the Kragujevac test.
4. Spin it by hand. It should turn freely with no gritty feel.

What if the bearing is loose or too tight?

Loose (it spins in the seat or drops out):

• Run a drop of cyanoacrylate (CA) glue around the bore wall, not over the bearing, so none wicks past the seals. igus has had good results with instant adhesives such as Loctite 401 on its bushings, but treats glue as support for a press fit, not a substitute.
• Reprint the seat 0.10 mm smaller on the diameter, the step the Kragujevac studies used.
• To correct every hole without editing the model, use the slicer offset from the hole compensation calculator.
• A seat that loosens only in use, near a motor or heater, is running warm. Sovol notes that printed plastic softens as it nears its heat deflection temperature, so move up to a higher-temperature filament.

Too tight (it won’t start, cracks the wall, or binds once in):

• Drill or ream out the seat. Lab64 notes that holes can be drilled after printing for higher accuracy.
• Measure the printed hole, enter the shortfall in “Holes print smaller by” in the tolerance calculator, and reprint. The dimensional accuracy guide covers measuring holes.
• If only the first layers are tight, that is elephant’s foot. Chamfer the mouth.
• If the bearing went in but turns stiffly, the interference is squeezing the outer ring. Open the pocket by 0.05 mm per side and reprint.