A press fit means the shaft is larger than the hole. You need force to push them together. FN (Force/Shrink) fits are press fits. The interference holds the parts in place without fasteners. Use them for bearings, pins, and permanent assemblies.

Tolerance Fit Chart: ANSI B4.1 & ISO 286 (Free PDF)

Q: What is a transition fit?

A transition fit can result in either slight clearance or slight interference. LT (Locational Transition) fits are transition fits. They give accurate location without being a full press fit. Use them for alignment pins and locating features.

Quick Answer: What Is a Tolerance Fit?

A tolerance fit is the amount of clearance or interference between a hole and a shaft of the same nominal size. The hole and shaft each get their own tolerance band, and the gap or overlap between them sets how the parts go together. Fits are used to size bearings, pins, bushings, dowels and shafts so they slide, locate or stay pressed in place.

This chart uses ANSI B4.1 preferred limits and fits to list: hole tolerance, shaft tolerance, minimum clearance or interference, and maximum clearance or interference. Inputs include nominal size (0.5″ to 3.0″) and fit class (RC, LC, LT, LN and FN).

Typical values at 1.0″: RC4 running ±0.0006–0.0020″ clearance | LC2 locational 0–0.0010″ clearance | LT1 transition −0.0002–0.0008″ | FN2 medium drive 0.0003–0.0013″ interference | FN4 force 0.0013–0.0023″ interference.

ISO 286 Preferred Fits at 25 mm (Hole Basis)

Metric drawings specify fits as an ISO 286 hole and shaft pair such as H7/g6. The ten preferred hole-basis fits below run from loose running to force fit. Values are in micrometres for a 25 mm nominal size; for any other size, the ISO limits and fits calculator gives the exact limits.

Fit	Name	Type	Hole limits (µm)	Shaft limits (µm)	Result at 25 mm (µm)
H11/c11	Loose running	Clearance	0 / +130	−110 / −240	+110 to +370 clearance
H9/d9	Free running	Clearance	0 / +52	−65 / −117	+65 to +169 clearance
H8/f7	Close running	Clearance	0 / +33	−20 / −41	+20 to +74 clearance
H7/g6	Sliding	Clearance	0 / +21	−7 / −20	+7 to +41 clearance
H7/h6	Locational clearance	Clearance	0 / +21	0 / −13	0 to +34 clearance
H7/k6	Locational transition	Transition	0 / +21	+2 / +15	15 interference to 19 clearance
H7/n6	Locational transition, tighter	Transition	0 / +21	+15 / +28	28 interference to 6 clearance
H7/p6	Locational interference	Interference	0 / +21	+22 / +35	1 to 35 interference
H7/s6	Medium drive	Interference	0 / +21	+35 / +48	14 to 48 interference
H7/u6	Force	Interference	0 / +21	+48 / +61	27 to 61 interference

Hole basis means the hole is always H (zero lower deviation) and the shaft sets the fit. H7/g6 is the everyday sliding fit for dowels and shafts in bores, H7/h6 the locational fit for parts that assemble by hand, H7/p6 the standard light press fit and H7/s6 the press fit for parts that transmit torque. The press fit calculator turns an interference into assembly force and stress.

Nominal Size (in) ▲	Fit Type ▲	Hole Tolerance ▲	Shaft Tolerance ▲	Min Clear./Interf. ▲	Max Clear./Interf. ▲
0.5"	RC1 (Close sliding)	+0.0000 / +0.0004	-0.0002 / -0.0004	+0.0002	+0.0008
0.5"	RC4 (Running)	+0.0000 / +0.0007	-0.0005 / -0.0010	+0.0005	+0.0017
0.5"	RC7 (Free running)	+0.0000 / +0.0012	-0.0010 / -0.0019	+0.0010	+0.0031
0.5"	LC2 (Locational)	+0.0000 / +0.0004	-0.0000 / -0.0004	+0.0000	+0.0008
1.0"	RC1 (Close sliding)	+0.0000 / +0.0005	-0.0003 / -0.0005	+0.0003	+0.0010
1.0"	RC4 (Running)	+0.0000 / +0.0008	-0.0006 / -0.0012	+0.0006	+0.0020
1.0"	RC7 (Free running)	+0.0000 / +0.0014	-0.0012 / -0.0023	+0.0012	+0.0037
1.0"	LC2 (Locational)	+0.0000 / +0.0005	-0.0000 / -0.0005	+0.0000	+0.0010
2.0"	RC1 (Close sliding)	+0.0000 / +0.0006	-0.0003 / -0.0006	+0.0003	+0.0012
2.0"	RC4 (Running)	+0.0000 / +0.0010	-0.0007 / -0.0014	+0.0007	+0.0024
2.0"	RC7 (Free running)	+0.0000 / +0.0016	-0.0014 / -0.0027	+0.0014	+0.0043
3.0"	RC4 (Running)	+0.0000 / +0.0012	-0.0008 / -0.0016	+0.0008	+0.0028
0.5"	LT1 (Locational trans.)	+0.0000 / +0.0004	+0.0002 / -0.0002	-0.0002	+0.0006
0.5"	LT3 (Locational trans.)	+0.0000 / +0.0006	+0.0004 / -0.0002	-0.0004	+0.0008
1.0"	LT1 (Locational trans.)	+0.0000 / +0.0005	+0.0002 / -0.0003	-0.0002	+0.0008
1.0"	LT3 (Locational trans.)	+0.0000 / +0.0007	+0.0005 / -0.0002	-0.0005	+0.0009
2.0"	LT1 (Locational trans.)	+0.0000 / +0.0006	+0.0003 / -0.0003	-0.0003	+0.0009
3.0"	LT1 (Locational trans.)	+0.0000 / +0.0007	+0.0003 / -0.0004	-0.0003	+0.0011
0.5"	LN2 (Locational interf.)	+0.0000 / +0.0004	+0.0006 / +0.0002	-0.0006	+0.0002
0.5"	FN2 (Medium drive)	+0.0000 / +0.0004	+0.0010 / +0.0006	-0.0010	-0.0002
1.0"	FN2 (Medium drive)	+0.0000 / +0.0005	+0.0013 / +0.0008	-0.0013	-0.0003
1.0"	FN4 (Force fit)	+0.0000 / +0.0005	+0.0023 / +0.0018	-0.0023	-0.0013
2.0"	FN2 (Medium drive)	+0.0000 / +0.0006	+0.0017 / +0.0011	-0.0017	-0.0005
3.0"	FN2 (Medium drive)	+0.0000 / +0.0007	+0.0020 / +0.0013	-0.0020	-0.0006

No fits match your search. Try a different term or filter.

Notes on This Chart

Tolerances follow ANSI B4.1 standard for preferred limits and fits.
Positive clearance means the hole is larger. Negative means interference (shaft is larger).
RC = Running/Clearance. LC = Locational Clearance. LT = Locational Transition. LN = Locational Interference. FN = Force/Shrink.
Always verify fit calculations with your specific nominal size range in the full ANSI tables.

ANSI B4.1 Fit Classes Explained

The chart above lists limits for the nine classes used most. ANSI B4.1 defines 34 classes in five families. This guide covers all of them: what each one is for and the nearest ISO 286 preferred fit when a metric drawing has to match an inch design. The ISO column is a working equivalent, not an exact conversion; the two standards use different size steps and grades.

Class	Name	What it gives you	Typical use	Nearest ISO 286 fit
RC1	Close sliding	Accurate location with no perceptible play; parts move with light hand pressure	Precision slides, gauge pins	H7/g6 (RC1 is tighter)
RC2	Sliding	Parts move and turn easily but are not meant to run freely; may seize with temperature	Lathe tailstock spindles, indexing plungers	H7/g6
RC3	Precision running	Precision running at slow speed and light journal pressure; not for temperature swings	Precision instrument bearings	H8/f7 (RC3 is tighter)
RC4	Close running	Accurate machinery with moderate speed and pressure; the most common running fit	Machine tool spindles, gear pumps	H8/f7
RC5, RC6	Medium running	Higher running speeds, heavier journal pressure, or both	Engine journals, general shafts in bushings	H9/d9 (slightly tighter)
RC7	Free running	Where accuracy is not essential, or with large temperature variation	Agricultural and conveyor shafts	H9/d9
RC8, RC9	Loose running	Commercial-grade shafting and bores with wide tolerances	Hinge pins, loose pivots, cold-rolled stock in bushings	H11/c11
LC1 to LC3	Locational clearance, snug	Parts assemble by hand and locate accurately; little or no clearance	Dowel-located covers, gauge locating pins	H7/h6
LC4 to LC7	Locational clearance, medium	Freer assembly with easy clearance for alignment	Bolted flanges, pulley hubs on keyed shafts	H8/f7 to H9/d9
LC8 to LC11	Locational clearance, loose	Large clearance where location is approximate	Guards, frames, loose spacers	H11/c11
LT1, LT2	Locational transition, light	Slight clearance or slight interference; parts tap together	Light press of small bearings, locating bosses	H7/k6 (LT1 is looser)
LT3, LT4	Locational transition, medium	More interference than clearance; mallet assembly	Gear and coupling hubs on keyed shafts	H7/k6
LT5, LT6	Locational transition, heavy	Mostly interference; press assembly, still removable	Bearing outer rings in housings	H7/n6
LN1	Locational interference, light	Accurate location with light interference; transmits little or no load	Bushings in housings	H7/n6
LN2	Locational interference, medium	Rigid location; parts can still be pressed apart	Dowel pins, bearing inner rings	H7/p6
LN3	Locational interference, heavy	Heavier interference for rigid alignment	Heavy bushings, locating sleeves	H7/p6 to H7/s6
FN1	Light drive	Light assembly pressure; permanent assembly of thin sections or long fits	Sleeves in thin housings, light-duty pins	H7/p6
FN2	Medium drive	Ordinary steel parts; shrink fits on light sections; the most common press fit	Gears, pulleys, bearing races on shafts	H7/s6
FN3	Heavy drive	Heavier steel parts; shrink fits in medium sections	Flywheel hubs, crank pins	H7/s6 to H7/u6
FN4, FN5	Force and shrink	Highly stressed parts, or shrink fits where press forces are impractical	Wheel centers on axles, heavy couplings	H7/u6 (FN5 is heavier)

How to choose: if the parts must rotate or slide, start in RC and go up a class for each of speed, load and temperature range. If they only need to line up and come apart, use LC. If they must stay put under light load, LT or LN. If they transmit torque or must never move, use FN and run the numbers in the press fit calculator so the hub does not yield.

Frequently Asked Questions

What is the ISO equivalent of an RC4 fit?

H8/f7, the ISO 286 close running fit. At 25 mm it gives 20 to 74 µm of clearance, close to the 0.0006 to 0.0020 in an RC4 gives at 1 in. RC7 free running corresponds to H9/d9 and RC9 loose running to H11/c11. The match is approximate because the two standards use different size steps.

What is the difference between H7/g6 and H7/p6?

H7/g6 is a sliding clearance fit: at 25 mm the shaft is 7 to 41 µm smaller than the hole, so it slides and turns by hand. H7/p6 is a locational interference fit: the shaft is 1 to 35 µm larger than the hole and must be pressed in. The hole is the same H7 in both; only the shaft tolerance changes.

What is an FN2 fit?

FN2 is the ANSI B4.1 medium drive fit, the most common press fit for ordinary steel parts such as gears, pulleys and bearing races on shafts. At 1 in nominal it gives 0.0003 to 0.0013 in of interference. The ISO equivalent is H7/s6. Use the press fit calculator to check assembly force and hub stress.

What is a clearance fit?

A clearance fit means the hole is always larger than the shaft. The parts slide or rotate freely. RC and LC are clearance fits. Use them for shafts that need to spin or slide.

What is a press fit?

A press fit means the shaft is larger than the hole. You need force to push them together. FN fits are press fits. The interference holds the parts in place without fasteners. Use them for bearings, pins, and permanent assemblies.

What is a transition fit?

A transition fit can result in slight clearance or slight interference. LT fits are transition fits. They give accurate location without a full press. Use them for alignment pins and locating features.

How do I choose the right fit class?

Start with the function. If parts must spin freely, use RC. If parts must stay put, use FN. If you need accurate location with easy assembly, use LC or LT. Tighter fits cost more to machine. Only use tight fits where the design requires them.

Tolerance Fit Chart

Quick Answer: What Is a Tolerance Fit?

ISO 286 Preferred Fits at 25 mm (Hole Basis)

Visual Boundary Scale

Select a Fit Class

Notes on This Chart

ANSI B4.1 Fit Classes Explained

Frequently Asked Questions

Fits & Tolerances Reference Series

More Resources

Need Precision Cylindrical Fits Machined to Tight Tolerances?

Tolerance Fit Chart

Quick Answer: What Is a Tolerance Fit?

ISO 286 Preferred Fits at 25 mm (Hole Basis)

Visual Boundary Scale

Select a Fit Class

Notes on This Chart

ANSI B4.1 Fit Classes Explained

Frequently Asked Questions

Fits & Tolerances Reference Series

Related Resources

ISO 2768 Tolerance Chart | General Tolerances for Linear & Angular

Press Fit Calculator | Interference Fit Stress & Force

Hole Tolerance Calculator | Fit Class & Size Limits

More Resources

Need Precision Cylindrical Fits Machined to Tight Tolerances?

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