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Boring out a threaded rod

Posted by Kyle Corbitt 
Boring out a threaded rod
August 05, 2008 03:45AM
I thought I'd crowdsource a dilemma I've been having.

For my high-temp extruder I've been trying to bore a 3mm hole through a 1/4" threaded rod. There's not much clearance, so the hole has to be exactly straight on with the bolt. I've tried several methods of trying to keep the bolt straight on with my drill press, including clamping it in a vice (wasn't quite vertical), drilling a 1/4" hole in a block of wood as a sort of jig (too loose) and tapping a hole in a piece of 1/4" aluminum and screwing it in to that (again, too loose).

I may try to procure a 3cm-thick hunk of steel, drill a hole in that, and tap it. I hope that that will be a rigid enough mounting arrangement for the threaded rod, but before I go to that length (I have to find a big hunk of steel first!) I'm hoping someone out there has a better idea!
Re: Boring out a threaded rod
August 05, 2008 04:24AM
Afghan lathe [people.bath.ac.uk]?

If you're going to thread the rod yourself anyway, you should probably get one that's already hollow, if possible (I think Nop said something to this effect, also related to a high temp extruder). A rod with a large enough OD and a small enough ID might not be available (note that the ID could be less than 3mm, and you could then more easily drill your 3mm hole in it, using the existing hole as a pilot), though, but if you could find something like that, it would probably make it a bit easier.

But, as far as I know, this is partly what a lathe is for, right?

Edited 1 time(s). Last edit at 08/05/2008 04:26AM by Joshua Merchant.
Re: Boring out a threaded rod
August 05, 2008 08:36AM
Purchase a 1/4-20 threaded coupler, usually available from the same place you get 1/4-20 threaded rod. It's a very long hex nut for connecting two pieces of threaded rod. Mount that in the drill press vice so the 3mm drill does down the center of the hole. Clamp down the vice. Put your threaded rod into the coupler and lock it down with a 1/4-20 hex nut. Drill the hole.
Re: Boring out a threaded rod
August 05, 2008 08:37AM
Yes the important thing is that you have to spin the workpiece around the drill bit rather than the otherway round. That is the difference between a lathe and a drill press.

I am lucky enough to have a small lathe, but even then I do not find it easy to get the hole exactly central because my lathe is a bit too small: [hydraraptor.blogspot.com]

IHMO, it is much easier to find a tube with the right ID and OD and tap it rather than starting with a thread and boring it.

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