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Unread 14-12-2011, 17:29
sanddrag sanddrag is offline
On to my 16th year in FRC
FRC #0696 (Circuit Breakers)
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Join Date: Jul 2002
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Re: Press Fit

For Loctite, 680 is good stuff. It's the green gap filling formula. I wouldn't necessarily use it to hold a gear to a shaft rotationally for instance, but man, that stuff does not budge once cured. I once glued a steel gear to a steel shaft with it and it took about 5 minutes with a propane torch, a vise, and the biggest pair of channel-locks I had to get them apart. Good for holding in bearings when you mess up the press fit tolerance.

I remember Mike from 233 telling me he would have gearbox plates waterjetted with the bearing holes a little undersized and simply run a reamer through them on a bridgeport while letting the plate "float" on the table. I was surprised they could hold an accurate enough center distance that way but apparently it works.

A 1 1/8" silver and demming drill will not make a 1.125 hole, nor will it make a round hole, especially in 1/4" just due to the size of it. The tip of the drill is more than 1/4" tall. You can do it, and it will work, but the hole won't be great. You'll be lucky if it ends up 1.127 which is a bit sloppy. You'll have to run down somewhere around 250 RPM too.

If you're working on a manual mill I suppose you could drill and ream. Do something like drill 27/32 or 55/64 for the 7/8" OD bearing and then ream to .875ish and likewise (a 64th or a 32nd undersize) for the 1.125 bearing. They make reamers that are .0005 undersize.

You perhaps could try something like a TCT hole cutter to do it all in one shot. I don't have experience with them though. I'm guessing your results would be better with a reamer.
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Teacher/Engineer/Machinist - Team 696 Circuit Breakers, 2011 - Present
Mentor/Engineer/Machinist, Team 968 RAWC, 2007-2010
Technical Mentor, Team 696 Circuit Breakers, 2005-2007
Student Mechanical Leader and Driver, Team 696 Circuit Breakers, 2002-2004

Last edited by sanddrag : 14-12-2011 at 17:32.
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