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I am designing a little project for myself and i started to think of the ideal or proper way to use both set screws and keyways. I've seen set screws against the keyway in some applications, others one is at 90 degress to the other, and others i've seen them 180 degress apart. What is the standard and are there any strengths to one method over another? THanks
I throw in another option, because set screws tend to damage the finish of the axle. I try to use axles with shoulders and a key. Then a screw and a ring to tighten the whatever against the shoulder. Normally torque transfer is then by friction, the key does the overload, and with normal tolerances there is no movement. Another option are tapered (keyless & setscrewless) hubs like these:
http://www.maedler.de/katalog_de/kat..._a01b36c04.htm
Carel
edit: learned to edit, link added.
Last edited by Carel; 04-04-2006 at 05:09 PM. Reason: link added
I like the setscrew on top of the key. This helps alleviate shaft damage, which in turn, marrs the bore of the hub when you go to remove it.
Also, most keyways and keys are assembled with a wee bit of clearance, so the setscrew on top of the key will help stablize the key.
I like what Carel said above, if that is possible to do.
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
I use something similar to Carel's example whenever possible called a Spieth coupling. Same problem as Carel's though. In order to tighten the coupling, you must be able to get at the end. Quite often you can not. EX. C-face motor attached to gearbox without enough clearance for even a shortened Allen wrench. When ever I can use the Spieth couplings, I do.
DZASTR
Proper set screw design is to use 2.
1 on the key and 1 90 degrees to the first.
2 screws 180 apart create a potential "rocking" issue due to the fact that the hub has clearance to fit over the shaft.
The set screws are like pivot points.
www.integratedmechanical.ca
one option, if you dont want to damage the axle is to drop in a lead BB gun pellet and use flat setscrews, I´m voting for 180degrees from the key.
This is what I was told years ago. But I could never get a good answer to the question why not 120 degrees apart so you get symmetric threeway contact.Originally Posted by DareBee
I did a quick action = reaction drawing, which rules out the 180 deg. screws too. We put the first screw at 0 deg., reaction point = 180 deg. Second screw at 90 deg. , reaction point = 270 degree. pressure points: 0 - 90 - 180 - 270.
Now 120 degree spacing: first screw at 0 deg., reaction point 180 deg. second screw at 120 deg., reaction point 300 deg. Pressure point 0 - 120 - 180 - 300, uneven division.
180 degree spacing is a reaction between the 2 screws, so one axle will not be supported.
Carel
The reaction points are (imo) meaningless theoreticals, since the actual physical situation is a tangent inscribed circle and there can be only one point of tangency.
120 degree will balance the load around the shaft, 90 doesn't since it works out to actual load points at 0, 90, 225.
(just to be contrary)
Tiger
White Tiger: I think we must compromise at screws drilled at random, because 0-90 is meaningless theoretical. I take the stand that 0-120 is way to difficult for the man who must drill the holes. Geometry involved: out of here! I settle at outdesigning setscrews, they get loose in the end.
Carel
LOL. nice riposte
Tiger
You are correct; and when they used to get loose in the sawmill I did weekend maintenance at the night shift millrights (I use the term loosely) would weld the sprocket to the shaft!!!!!! Still I shouldn't complain 20 or more hours (which paid anything up to 50 hours depending on the balance of single, double, and triple time) each weekend fixing this sort of c*** put me through university debt free.
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