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Frank Downey
07-05-2009, 09:37 AM
where can I find a chart that tell me how much tolerance I need to allow for fitting bearings to a shaft that I will turn?The problem is I don't have the bearings in and I have to go ahead and spin the shaft.The shaft is 4140 carbon and the beaings are 3/4" pillow block bearings.Or what do you guys usually allow for such fit?RPMS will run 950rpms with meduim load

oldtiffie
07-05-2009, 09:45 AM
These (in metric) - from a previous thread - might help:

http://i200.photobucket.com/albums/aa294/oldtiffie/Tolerancing/Caliper_accuracy1.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Tolerancing/Caliper_accuracy2.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Tolerancing/Caliper_accuracy3.jpg

motorworks
07-05-2009, 10:53 AM
Bearing fits,
Housing and shaft:
http://www.conweb.com/tblefile/bearfta.shtml

Frank Downey
07-05-2009, 11:57 AM
you guys rock thank you for the info.

wierdscience
07-05-2009, 12:12 PM
You said "pillow block",they have setscrews or eccentric collars for a reason.They are made to be a slip fit,or in your application .750+.000/-.001"

Timleech
07-05-2009, 12:17 PM
My RHP manual for their Self-Lube ball bearings (pillow blocks etc) gives shaft limits of +0.000 to -0.002" for what they call 'low speeds', in this case up to 1700 rpm.
up to 4200 rpm on a 3/4" shaft it's +0.0000 to -0.0008"

Tim

motorworks
07-05-2009, 12:26 PM
Sorry
The chart above was for deep groove ball bearings. Keep it on just in case. For pillow blocks: Infor from "dodge bearings"

ENGINEERING/TECHNICAL

Shafting:

Standard Shafting-Table 17 indicates standard
shafting is cold drawn in the smaller sizes and turned
and polished in the larger diameters. It has a smooth
surface, is commercially straight and is readily
machinable; suitable and recommended for general
power transmission and material handling service.
Special Shafting-While standard shafting is suitable
for most installations, special shafting is sometimes
required for certain chemical, temperature or physical
requirements. Such materials as high carbon steel, alloy
steel, stainless steel, brass, Monel metal, etc., can be
furnished plain or heat treated. Stepped, flanged, hollow
or other special forms are available.
Special shafting should be avoided in favor of standard
shafting wherever possible because special shafting
is usually considerably more expensive and requires a
greater length of time to obtain, which is an especially
important consideration should quick replacement ever
become necessary.
Ordering Shafting-Standard shafting can be obtained
from most supply houses and dealers who handle
power transmission material.
Turning Down Shaft Ends-When necessary to turn
down shaft ends, use as large a fillet as possible to
keep the stress concentration to a minimum. The
radius of this fillet should preferably be not less than
the difference in the two diameters joined by the fillet.
The fillet should be finished and polished as smoothly
as possible to avoid scratches which might start cracks
and lead to failure of the shaft by fatigue.

Table 17: Typical Commercial Shaft Tolerances

Shaft Size Plus Minus
Up to 1-1/2 .000 .002
Over 1-1/2 to 2-1/2 .000 .003
Over 2-1/2 to 4 .000 .004
Over 4 to 6 .000 .005
Over 6 to 8 .000 .006
Over 8 to 9 .000 .007
Over 9 .000 .008


Table 18 lists the recommended tolerances for all setscrew locking,
eccentric locking and D-LOK locking ball and roller bearings
Table 19: Shaft Tolerances:

Shaft Size Tolerance, Inches:

Up to 1-1/2 +.000 -.002
1-9/16 to 2-1/2 +.000 -.003
2-5/8 to 4 +.000 -.004
4-3/16 to 6 +.000 -.005
6-7/16 and above +.000 -.006