Today in the shop "Making 3/4" holes in to 20mm"

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reible
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Today in the shop "Making 3/4" holes in to 20mm"

Post by reible »

I do not recall the who or the when but I got this idea from somewhere. Wish I could give credit.

Let start with what is happening. You have a nice 3/4" hole. Thing is you wished it were say 20mm. As you may know 3/4" is smaller then 20mm so it clearly can be done, right?

Say this is your hole:
hole1.jpg
hole1.jpg (181.86 KiB) Viewed 2268 times
The bit you want to use looks like this compared to the hole.
hole2.jpg
hole2.jpg (221.88 KiB) Viewed 2268 times
You could take various routes to do the drilling but today we will look at using a step drill. In this case I happen to have a 20mm spiral groove version.
hole3.jpg
hole3.jpg (128.88 KiB) Viewed 2268 times
By design the bit is self centering and has a chamber to help get it started. As a result you can get a hole that looks like this:
hole4.jpg
hole4.jpg (187.97 KiB) Viewed 2268 times
Now the bit has a nice place to start as shown here:
hole5.jpg
hole5.jpg (191.73 KiB) Viewed 2268 times
This is of course not the only way to do this but it sure works slick.

Ed
{Knight of the Shopsmith} [Hero's don't wear capes, they wear dog tags]
AEA
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Re: Today in the shop "Making 3/4" holes in to 20mm"

Post by AEA »

Nice. That is much easier than anything I've used so far.
I almost want to drill too small of a hole just to try it out. :)
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dusty
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Re: Today in the shop "Making 3/4" holes in to 20mm"

Post by dusty »

I depend a lot on my step drills but now I need to go get another one. I want to have a metric in my tool box.

Thanks Ed.
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Dusty
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daveg
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Re: Today in the shop "Making 3/4" holes in to 20mm"

Post by daveg »

Great tip.
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