Re: [CAD_CAM_EDM_DRO] NEMA 34 motor mounting question

In a message dated 1/10/2003 9:40:55 PM Central Standard Time, xyz@...
writes:

> I about to mount a NEMA 34 motor, it has a square front plate with four
> equally space mounting holes. The hole diameter is 0.218 which seems
> sloppy for 10-32 and too tight for 12-32. I feel like I should be using
> 12-32. Is it normal to expect the end user to drill these mounting hole to
> suit !<< NO!

I have mounted a dozen of them, so I feel arrogantly adequate in answering
you: Sloppy? How accurate a BC can you drill, when you drill/tap for the
screws? That "slop" is for a very every-day practical reason! Human
Frailty! They are for #10 cap-screws! Use of burrs is allowed, if you feel
necessary.

>
> Next question:
> The front mounting plate is not complete flat, it has a raised portion
> (0.06") and round (2.872 diameter) . When I mount this to a plate I will
> have to remove that same amount of metal ( and a little extra) to ensure
> the motor is bolted flat to the mounting plate.<<

NO! Doncha DARE! Read on . . .

>
> What is the purpose of round raised portion! To me it would be better if
> front was flat ? I expect there is a good reason for this strange
> arrangement....<<

Whew, I am struggling to remain civil! That "raised portion" is called a
"boss" and it is there for a NECESSARY reason: It is to
CONCENTRICALLY-LOCATE the motor when you mount it. This is necessary because
of those "sloppy" screw-holes, doncha know! This is the way precision
machinery is done! Screws are NOT dowels!

You must bore a relief 2-7/8" dia. x 0.07" to 0.1" deep. And then four 10-32
tapped holes around that on 2.75" centers. Always de-bur and "dry-fit" the
piece in such a relief to make sure it "goes", and clean it all free of
swarf, set the motor in, spin-in four 10-32 SHCS with small burrs or split
lockwashers, and snug 'em one at the time until all-four "touching" before
you begin to torque 'em down!





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