Need Help!- Bored Hole Overcut for Slip Fit

[Adamj12b]

I am working on a simple shaft coupler for connecting a large electric motor to another shaft. I need to bore the coupler to slide nicely over the motor shaft. My problem is I do not have the motor in my possession to just machine it to fit. All I have is the drawing of the motor. http://www.go-ev.com/images/003_09_0...ng_Drawing.jpg The sheet shows the DE end shaft diameter between 1.245 to 1.250.

So what I am looking for now is an idea of how manu thousandths I should over bore the hole for a nice fit. I will broach it with a .250" wide by .125" deep keyway for locking to the shaft. I will add a set screw to the back side of the key to create clamping force on the key face.

Any ideas?

-Adam

[Shane123]

.005 is plenty for a nice bearing sliding fit for shafts, as well as couplers. so at 1.255" +.000 -.003 should be good.

[Adamj12b]

Originally Posted by Shane123 .005 is plenty for a nice bearing sliding fit for shafts, as well as couplers. so at 1.255" +.000 -.003 should be good.

Shane123,

Thank You. That was the answer I was looking for. I was thinking like .003 to .004 would be good, but wasnt sure.

-Adam

[Shane123]

.003 would be fine, as long as your part is true. i like .005 but less is better if you have chance of wear.

[pauluk]

Hi
To me there would seem to be a mistake on the drawing. If you look at the shaft at the other end of the motor it is dimensioned as 0.8750 to 0.8745 or in other world a 0.0005 span, which is what I would expect to see on a motor shaft. The 0.005 tolerance is excessive and means that a nice sliding fit can not be guaranteed. If you then take in the 0.003 clearance suggested you could end up with a 0.008 rattle fit rather than a slip fit. I would suggest that the size on the drawing should read 1.250 – 1.2495. I would aim for 1.250 -0.000 +0.0005 or +0.001 at most, on the bore which would give you a transition fit

Regards
Paul

[mactec54]

Adamj12b

It should be between .0002/.0005 over the max shaft dia, not + .003/.005 that would be way to loose

[DareBee]

I agree with Pauluk.

We do most couplings to a press or shrink fit (depending on size).

[RICHARD ZASTROW]

DITTO

Dick Z