Re: [CAD_CAM_EDM_DRO] NEMA 34 motor mounting question

On Friday 10 January 2003 10:38 pm, you wrote:

> 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 !

It's .03" larger than the O.D. of the screw, which for a #10 is pretty
sloppy. It's just about perfect for an M5 screw... You'll probably want to
stick with #10s and thick washers though, because the screws aren't meant to
locate the motor's position, they just fasten it to its mount. The reason
they're sloppy is so that the screws _don't_ bind against the I.D. of the
hole and influence the mounting position.

Here's a sketch of the basic dimensions:
http://www.qcontrol.com/images/34Nframe.gif

> 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.
>
> 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.... May be to
> make more work for machine shops !

The .06" high raised boss is the feature that's used to locate the mounting
position, it's concentric to the motor's shaft. Your motor mount should have
a 2-7/8" diameter pocket at least 1/16" deep (can be a through hole) into
which the locating boss extends. For some applications where the motor has to
move to adjust belt tension, you can use a 2-7/8" wide slot (and slotted
holes for the mounting screws).

> Thanks for any help...
> Hans W

If it's any help, you're welcome,
Matt