Press Fit

[Brandon Holley]

Originally Posted by JamesCH95

My opinion is that for 1/4" and thinner you'd be better off with a good quality step drill, hole cutter, and/or reamer, depending on what sort of fit you wanted. I don't like how big drill bits like that are not very forgiving. They can make 'triangle holes' and catch big burrs and spin parts when they're used in thin material.

I'll echo this as well. Bearing holes are always going to be the same sizes, 0.875", 1.125", etc. Investing in a couple of reamers that only do that job will last the team forever, and give you accurate, repeatable results.

-Brando

[sanddrag]

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.