On 2010-08-11, Gunner Asch wrote:
Ive made 6 pairs of spacers...between a driven shaft (both ends) and a
bearing race and each and every time, Ive gotten the OD wrong.
Each and every time..tap on the bearing race..and the ******* slides on.

How the hell does one calculate such a thingy?

This was off a pumping unit gearbox..and the people are starting to look
at me like im an utter bumpkin...which it looks like I am...sigh.

The ID was to have a .002" interference fit..and I accomplished this
with no issues. I machined the OD to be .003 larger than the ID of the
bearing race....and once the bearing race was tapped a couple times..the
damned thing slid on with a tad bit more than hand pressure. Easy with a
small block of wood.

Blink blink....

Anyone got any ideas/help/calcs that would fill in this blank space in
my knowlege?

First off -- how big is the OD? The amount of oversize for an
interference fit is a function of diameter.

According to _Machinery's Handbook_:

"Allowance for forced fits -- the allowance per inch of diameter
usually ranges from 0.001" to 0.0025", 0.0015" being a fair
average. Ordinarily the allowance per inch decreases as the
diameter increases, thus the total allowance for a diameter of 2
inches might be 0.004", whereas for a diameter of 8 inches, the
total allowance might not be over 0.009" or 0.010"

In following pages, there are formulas and tables for
calculating desired fits based on among other things the OD of the part
containing the hole to fit.

This is what Ive been machineing parts for...

http://www.datinternational.ca/product.php?punits

Im going to have to get the Clausing 15" lathe running..the Hardinge
HLV-H...is way way too small for most of the work.

This suggests that it is a fairly hefty chunk of steel. So,
aside from the diameter -- are you using coolant? Without it, consider
the expansion while you are machining (from the heating). You may be
hitting the diameter when hot -- but when it cools down, it shrinks
enough to make a difference. If you don't have coolant, the solution is
to turn it to a bit oversized, go to bed, and the next morning measure
it and skim off just enough to make your intended dimension.

I installed a Axelson 20x120 lathe in their shop...but they dont have
3ph yet..or anytime soon...sigh....

Rotary converter time? How many HP does that lathe need?

Enjoy,
DoN.

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