Posted by Anton Abaya at 1/26/2001 12:39 AM EST
Coach on team #419, Rambots, from UMass Boston / BC High and NONE AT THE MOMENT!
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In Reply to: thanks ken...
Posted by Anton Abaya on 1/26/2001 12:36 AM EST:
: : : I don't think the coupler has any set screws... (none that I would consider set screws) It's threaded and has 4 screws along the side to clamp it down over the drive shaft and whatever you're driving, as a compression type fitting rather than set screwing.
: :
: : Ok, so the drill motor coupling can be seen as two part: the first half attaching to the output shaft of the drill motor gear assembly, and the second half attaching to a 3/8" shaft. Both halves each have two #6-32 UNC-28 set screws on the side for tightening the whole coulping so it will grip harder on the drill output shaft as well as the 3/8" shaft.
: : Now the difference between the two halves is that:
: : the first half (for drill motor gear assembly) is threaded internally so it can be screwed on, with a 1/16" hole on the side for a spring pin to prevent the coupling from unscrewing.
: : the second half (for a 3/8" shaft) is smooth internally (not threaded), NO 1/16" hole on the side, and a 1/8" keyway so you can make a identical keyway on a 3/8" shaft and use keystock to lock that shaft with the coupling.
: : Now, what Andy suggested is a modification on the first half, where you use a lock washer to grip the coupling tightly on the motor output shaft (same way lock washers lock nuts on a bolt), and enlarge the 1/16" pin hole, tap the hole, and use a #8-32 screw (which to my knowledge we count that as set screw) instead of a pin to prevent the coupling from unscrewing. Since the lock washer is always locking the coupling pretty hard, there won't be as much stress on the #8-32 screw, therefore it worked nicely.
: : As for the other half, I am not sure how strong are the two #6-32 UNC-28 set screw on the side, but on theory they can be tighten so the 3/8" shaft won't slip out, while the key prevents that 3/8" shaft from spinning freely. But you would want to support both side of that 3/8" shaft anyway because of the side load if you are putting a sprocket on it to drive a drive train. In the process of supporting the shaft on both side and/or mounting a sprocket on the shaft you can figure out a way of making sure that shaft won't slide out of the motor coupling...
:
: the summary actually helped..
also... as a note, we did everything above except tap hole to fit in a set screw... we figured it did not need it, but if you guys suggest it, i'll see what our machinist thinks of it...
the shaft end of things is the confusion to us and we are just going to drive on it and just tighten those set screws as much as possible and see what happens. we do not expect to have problems, but we'll see what happens anyway.
thanks for the info...
-anton
"Set Screws are those babies that make funny noises."