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Do I need a J drill or what?

My 7mm holes in Delrin are too tight ...

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Mick B125/06/2023 13:52:17
2444 forum posts
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I've usually found holes drilled in acetal seem to pull in, as if the material deformed elastically as the drill went through, then contracted on withdrawal.

I'd go for the 0,1mm increments too. Could try using a larger centre drill first, to leave a lead-in taper, though it might be a bit late to be suggesting that now.frown

As others've said, unless you've measured the leads carefully, you might not know whether they're as round, straight, parallel and to size as the hole is.

peak425/06/2023 20:47:02
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Posted by DC31k on 24/06/2023 17:40:15:

Leave the delrin in the freezer overnight. Drill through it with the 7mm bit tomorrow morning.

I would imagine that the problem lies with the leads, rather than the Delrin.
Most HT lids I've used as slightly squashy, so are likely to bunch up on being pushed into a hole.
Maybe put the leads in the freezer, instead of the Delrin, to stiffen it up a bit, or make a thin tubular guide out of shimstock or a soft drinks can.
Squash that around the lead, with a bit of lube, insert into hole, and remove the metal bit.

Bill

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