Subject: Note the extended point set screws
From: rotaryeng
Date: 8/25/2014, 7:39 PM
To: AA-1-Me


   Note the extended point set screws are better and easier to machine than splines. All back lash is eliminated.

Paul Lamar


Hi Paul, can you give an overview on the " Note the extended point set screws are better and easier to machine than splines. All back lash is eliminated." I am not familar on this topic.

Thanks, Steve Carlisle

A spline (properly machined)  is proud of diameter 1.
The inner shaft is the  highest stressed part. So for max strength it should be as large as possible.  There is a shear stress concentration at the start of the spline and near  the root of the spline.

You can make the shaft larger diameter  with thinner wall say diameter 2 if you use set screws. The shear stress is then distributed over the number of screws you use.

Of course it  much much easier to machine with no broach or mill required. Especially the female part. I know no way of doing a female spline  with out a shaper or broach.

Just a drill press and taps are all that is required for extended point set screws .

Tightening down the set screws removes all slop and back lash.


BTW always sign your last name as we have many Steves on here :)

Paul Lamar


Okay Paul, where in Tracy,s re-drive would you be able to use those screws .

Steve Carlisle


 Do I detect a  doubting  Steve ? :)

Since the pin fixing the input shaft to the sun gear failed twice THAT IS WHERE THEY ARE SORELY NEEDED :) You will need 8 or 12-- 3/8-24.

Paul Lamar

Hi Paul,
   To use set screws to fix the primary shaft into the (hardened) sun gear, how
does one drill and tap that hardened gear ?
   Chris.

Get it normalized. Send the parts to me as we have a heat treater here in Ventura.
You can then get it hardened again.  Or try normalizing just the aft end with a torch.

I was able to cut the un-needed teeth off with a carbide
lathe tool. It is probably only case hardened so a good tap may still work.
Give it a try. I was able to drill it as well without normalizing.

Another way  to get the un-needed teeth off is mount a small bench grinder on your lathe
cross slide.

Paul Lamar

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