Snug fit 1/4" aluminum rod in a 1/4" hole

[Kesh Ikuma]

I want to make a rotatable/detachable wooden knob to a 1/4" aluminum rod. The hole on the knob is about 7/8" or so. I drilled 1/4" hole, hoping that the run-out of my drill press/bit would create a snug fit hole. But it turned out really tight. (I guess this is great news for me in a normal circumstance.)

Do you have any advice as to how to slightly oversize the hole or to skim the rod diameter by a hair?

I've tried:

- Using every 1/4" drill bit I have
- Chuck the rod and sand/file while turning.

Neither made enough difference. Any tip would be much appreciated!

Thanks,
Kesh

(P.S., I haven't been here in a few years, but glad to see it still active!)

[Richard Coers]

Use a 7mm drill (1/4" is 6.35mm), or F drill bit which is .257 or G drill which is .261

[Kesh Ikuma]

Use a 7mm drill (1/4" is 6.35mm), or F drill bit which is .257 or G drill which is .261

Ah, that's a good idea. Glad I've been turning some pens recently :-) I'll give it a try tomorrow. Thanks! -Kesh

[stevo wis]

I want to make a rotatable/detachable wooden knob to a 1/4" aluminum rod. The hole on the knob is about 7/8" or so. I drilled 1/4" hole, hoping that the run-out of my drill press/bit would create a snug fit hole. But it turned out really tight. (I guess this is great news for me in a normal circumstance.)

Do you have any advice as to how to slightly oversize the hole or to skim the rod diameter by a hair?

I've tried:

- Using every 1/4" drill bit I have
- Chuck the rod and sand/file while turning.

Neither made enough difference. Any tip would be much appreciated!

Thanks,
Kesh

(P.S., I haven't been here in a few years, but glad to see it still active!)


You could put the rod in a freezer before you slip it in.

[Doug Garson]

Or maybe try putting the aluminum shaft in the freezer for an hour before inserting it.

Looks like Stevo beat me to it.:cool: Great minds think alike.

[Bill Dufour]

A 1/4 rod into a 7/8 hole is a very loose fit you will need to glue it in.
Bill D

[Kesh Ikuma]

You could put the rod in a freezer before you slip it in.

Will it not bind once it warms back up?

I need the knob to be rotatable w/out too much force. I guess I can try and see what happens

[Kesh Ikuma]

Yes indeed, but I meant that the depth of the hole is 7/8". Sorry for the confusion.

[Doug Garson]

Will it not bind once it warms back up?

I need the knob to be rotatable w/out too much force. I guess I can try and see what happens
How do you propose to keep the wooden knob from falling off? Maybe you should elaborate on what you are trying to do and why. Is this a one off application? If you just want the knob to easily rotate and slide on and off the rod, just drill an oversized hole or sand the rod down until you get the fit you want.

[Cameron Wood]

Chucking the rod in a drill press or even a portable drill and filing should work with little effort. what speed did you use?

[Bill Dufour]

Put the drill loosely in the chuck. Slip a small strip of paper between one chuck jaw and the drill bit. Tighten and drill normally. Add more and thicker paper as needed to get enough offset for the diameter needed.
Note the work has to be clamped firmly or thew bit will walk the work around instead of making the hole larger.
Bill D

[Kesh Ikuma]

Ah, that's a good idea. Glad I've been turning some pens recently :-) I'll give it a try tomorrow. Thanks! -Kesh

7mm is too large for a snug fit, unfortunately.

[Kesh Ikuma]

How do you propose to keep the wooden knob from falling off? Maybe you should elaborate on what you are trying to do and why.

The knob is not actually a knob. Instead they (4 of them) will act as the bottom ridge for a cookbook stand that I'm building. A couple of them have a little wing which can be rotated to hold the pages, thus need to rotate. So, they will be positioned at an angle with the book weight on them, thus no need to worry about them falling off.


Is this a one off application?

Yes, It's a wife request.


If you just want the knob to easily rotate and slide on and off the rod, just drill an oversized hole or sand the rod down until you get the fit you want.

Yeah, sanding seems to be the way to go... I guess it'd be smarter if I use wooden dowels instead of aluminum, but sanding may be quicker than me trying a bunch on lathe to get them all fit...
Yes, it is.

As I wrote this, I realize that I could also use 5/16" threaded rods and tap the thread on the knobs. Thanks for helping me brainstorm!

[Kesh Ikuma]

I had it on my lathe at 1000 rpm. My file is a cheapo boxstore one, and it seems to varnish more than filing...

[Kesh Ikuma]

Put the drill loosely in the chuck. Slip a small strip of paper between one chuck jaw and the drill bit. Tighten and drill normally. Add more and thicker paper as needed to get enough offset for the diameter needed.
Note the work has to be clamped firmly or thew bit will walk the work around instead of making the hole larger.
Bill D

That's a brilliant idea although the clamping tip truly is the key. I gave it a try tonight with a test walnut piece on a metal vise but there is just enough wiggle on my drill press for it to not widen the hole. I could see the bit wobble, so I'll likely try it again tomorrow to tighten up the clamping a bit more than I tried earlier tonight.

[Bill Dufour]

If the hole was 1/2" or bigger I would say use a boring head. If it is a through hole they make adjustable reamers as well.
BilL D

https://www.amazon.com/Boring-Head-Shank-Carbide-Milling/dp/B07ZFJFC7Q/ref=sr_1_31?crid=26M4GDALRWEF4&keywords=boring+head+straight+shank&qid=1702445737&sprefix=boring+head+straght+shank%2Caps%2C148&sr=8-31

https://www.amazon.com/findmall-11Pcs-Adjustable-Reamers-H4-H14/dp/B09XX89FK8/ref=sr_1_2_sspa?crid=19INDXNA8GG94&keywords=adjustable+reamer&qid=1702445847&s=hi&sprefix=adjustable+reamer%2Ctools%2C146&sr=1-2-spons&ufe=app_do%3Aamzn1.fos.17d9e15d-4e43-4581-b373-0e5c1a776d5d&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1