set screw size ?

[Hal]

I need to couple a sewing machine motor's shaft to another shaft.
Both are 1/4"Ø.
Is there a chart or rule of thumb showing the "standard"
size set screw to use on a certain Ø shaft ?

Hal

 

[Metal Butcher]

I need to couple a sewing machine motor's shaft to another shaft.
Both are 1/4"Ø.
Is there a chart or rule of thumb showing the "standard"
size set screw to use on a certain Ø shaft ?

Hal

I don't know if there is a chart nor do I have one.

If It was my project a 4-40 or a 5-40 would be my choice. 6-40 seems a bit big and the threads seem to coarse. But this would depend on how big in diameter your coupler will be.

Given the power of a sewing machine motor, flats or drilled dimples for the set screws would be a good idea.

Another option is a coupler pined with small tapered pins. These are used occasionally on machines like lathes. On my lathe the lead screw is pined to the gear box shaft.

Someone with more experience will be along to add to what I've said.

-MB

 

[Maryak]

Hal,

The definitive answer from Machinerys Handbook:-

P=(DNd^2.3)/50

P = Horsepower
D = Shaft dia.
N = rpm
d = set screw dia.

I've found that between 1/2 and 1/4 of shaft dia is about right for a single set screw. With lots of torque smaller multiple set screws are better if there's sufficient length to fit them in.

Best Regards
Bob

 

[tel]

I've found that between 1/2 and 1/4 of shaft dia is about right for a single set screw. With lots of torque smaller multiple set screws are better if there's sufficient length to fit them in.

Best Regards
Bob

;D I use 1/3 of Dia as a general rule of thumb. (D/3 Marv?)

 

[Mainer]

Two setscrews at 90 degrees to each other work well to prevent any slight movement between the parts.

Flats on the shaft give space for any burrs caused by the setscrews, so they won't interfere with disassembly later.