On-size bearing holes with a drill press

Not every team has a milling machine, so we experimented with various tools to make bearing holes with a drill press. We found some things that definitely don’t work, and one that works great. Here’s Triple Helix Tech Tip #1: making bearing holes with a drill press.

This is good stuff! I’ve been wondering forever what the best annular cutters are to use, and how accurate they are. Good to hear that it gives such great results!
Somewhat sad about the step drill- I’ll have to inspect 1072’s later to see if the size is correct.

EDIT: That annular cutter does look pretty expensive, at $80 for the shank/shell combo. Is there source other than MSC that people have had good results from?

We have used an annular cutter like this and a 3/4" drill chuck in the past.

Like that, or that one exactly? I want to know what brand to buy, mainly.

We’ve used that one with good success. Don’t lose the center pin!

I have used a modified spade bit with much success over the year before 1678 had nice things. I modified this bit in 2010 and we still have it and it still works, but requires a drill press and can only do 1/8" thick aluminum.

What were your modifications?

Given that it’s marked as 1 1/8 (inches), or 1.125, and the caliper is showing 1.1215 inches, I would say he shaved off .00175" from each side. Might have been targeting .002" from each side.

Before and after

Brought the sides in a little at a time on a grinding wheel until the fit was as desired. The teeth had severe relief ground in as best as I could, this reduces cutting force and chatter.

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I figure it’s shaved down in diameter, but would it cut aluminum with its standard cutting edge?

We (7013) cut a number of bearing holes with a harbor freight (Canadian tire but same thing) step drill. Surprisingly they turned out as a slight press fit! As in the picture the bits are right on size, 1.125, maybe a bit less. With a rigid drill press I’ve found they work quite well. Maybe the style used in the video (I tend to see them as Irwin branded) don’t work quite as well?

More good work from Triple Helix, Thanks.

Teams should also be aware of some other possible causes for holes being oversize, beyond tooling. The drill press itself may be an issue, perhaps due to a loose spindle, chuck or table. Another issue to consider is clamping, is your work piece held in a rigid manner? When drilling beyond the edge of the vise, flex in the work piece can be a big issue. Consider adding fixed support from below to avoid deflection. Making sure the tooling will clear the support as it passes through the work piece.

Those are awesome cutters, we use them frequently at work.

Has anyone experimented with the VEXpro reamer?

This is great stuff…it would be nice to expand on this maybe partner with low resource teams and do a full guide. I know for us at least it seems material wall thickness plays a part in our hole outcome as well as using cutting oils. Also gonna check our irwin step drill bit now for size.

We got one this past year, and it has worked pretty great for us. It provides a nice slip fit probably slightly looser than the Annular cutters mentioned above.
Takes a couple tries to get good at it with a hand drill, and the hole you are reaming needs to be fairly uniform (ie. it isn’t going to fix a mangled lopsided hole made with a bad bit / drill press).

Great stuff.

Getting the hole size close enough to correct is important. So is having the holes on either side of the tube line up correctly. Drilling through both sides of the tube will cause the holes to align only if the tube is being held perfectly perpendicular to the axis of the drill bit. If the axis of the cutting tool is 1 degree off from being perpendicular, the centers of the holes on either side will be misaligned by around 0.017". This may make it difficult to push a shaft through a pair of bearings installed in the two sides of the tube.

Many of the drill presses I have seen teams using have tables off perpendicular by more than 1 degree. Also, many drill press tables are not very rigid so when someone is forcing a dull drill bit through the material, the table can be seen flexing by several degrees.

Lastly, proper workholding needs to be exercised. Todd can be seen clamping to tube in a substantial vise that is probably firmly secured to the table. Holding a tube on the table by hand will probably not be good enough for applications like this.

Yes it does cut without modification, but it only works well on thin aluminum without the gullet modification because it has to cut the entire hole diameter at once past about 1/16th of an inch.

If the workpiece is tilted, the shaft will still pass through two bearing cleanly- just at a 1* angle from the normal.

Only if the bearing permits the shaft to pass thru the bearing at a 1deg angle. That may not always be the case, especially if you’re using structural hex as hex shaft.

Has anyone done a comparison to using a 1.125" knockout punch?