Hub mounting

[rock_breaker]

I am trying to make an indexer by using a 1:40 worm gear assembly salvaged from an industrial application. My question is will a socket set screw against the 7/8" shaft hold a hub from lateral movement? I have made a hub ID to accomodate the 7/8" shaft and the OD 1-1/2" X 8 thread for mounting chucks from my lathe. I Included a 1" wide X 3-1/4" diameter shoulder to mount a clamp and possibly an indexing scale.

I have seen setscrew applications where the screw goes against a key in the shaft, also a flat milled in the shaft. The hub has a keyway so either application is possible. I have also thought about drilling a shallow hole into the shaft to receive a stub machined onto the end of the set screw. The small hole seems to be the logical method but will it significantly decrease the strength of the shaft?

Any help will be greatly appreciated.

Ray

 

[Tony Wells]

Ultimately, a shared key will be stronger, but unless you have the means to cut it in both, that's not an option for you at this point. The load from cutting will attempt to spin the hub, so shear is the main concern. I'd much rather have a "pin" than just a set screw. Either buy a dog (or half-dog) point set screw, and put a hole in the shaft to match it. It won't take much depth to achieve acceptable shear strength, so the shaft won't really suffer. If this is a permanent installation, after tightening the set screw, check the runout, both radial and lateral, of your hub or threaded sub-spindle. Chances are pretty good that you will want to skim cut the registers after mounting.

 

[dickr]

If it's a permanent lock I'd put a 2nd set screw on top of the 1st set screw. Also when you drill for your tapped hole have your shaft mounted and drill it in position. You get much closer location. Of coarse I'm not sure if I understand your explanation. Pictures would help a bunch. I know easier said than done. could you drill in to both so a pin would fit half in each part. Say a 1/4"dia. drill with half in each part or even a 1/4-20 thread the same way.
Now is that all gibberish:biggrin::biggrin: Sorry if I wasted your time but it keeps me from being idle.
dickr

 

[rock_breaker]

Thanks Carl and DickR,

Not knowing how to send pictures sucks, especially now. The hub and shaft will be drilled as one unit, a pilot hole then the "tap" hole. The difficulty ecountered will likely determine the securing method.

I hear you on facing the registers, The output shaft holding a 5" three jaw chuck had .002" runout during a test without securing the hub to the shaft. If 1/4 X 20 threads were put in the shaft and hub and the bolt were jammed into the shaft would that let the hub "float" as opposed to being forced to one side of the bore? I had to use light oil to get the hub on the first time, it slides freely now but I do not feel any play. Will put the DTI on it tomorrow.

Again thanks for the solution to a knotty problem.

Ray