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Thread: Old drill bits as lathe cutters?
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9th July 2014, 02:00 PM #1Senior Member
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Old drill bits as lathe cutters?
Hey guys,
I've ruined a few good sets of HSS drill bits. Being the type to never throw anything away, I as wondering if I could grind the bigger ones down to a square tip and use it on the lathe. I'm sure this has been done before, but is it ok to do?
Cheers
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9th July 2014, 02:11 PM #2Mechanical Butcher
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If you mean the shank part that goes into a chuck, this isn't hard enough.
You might be able to harden it.
I saw a twist drill modified to use in a CNC machine, cutting serrations on the end of shafts. But that was the hard end doing the cutting.
Jordan
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9th July 2014, 02:16 PM #3
It certainly is. They are used for many similar cutters. The shank is not hard. This can be used to advantage. For home made boring bars and the like, round hss can be better as it will fit in drilled holes. Never throw away broken or worn hss.
Dean
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10th July 2014, 12:12 AM #4Senior Member
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10th July 2014, 01:21 AM #5
Hi Guys,
I agree ! Never throw away broken bit of HSS or carbide for that matter. I use 3 mm shank carbide drills and milling cutters for various jobs. These things break if you look at them the wrong way ! But the 3 mm shafts being solid carbide, they make great boring bar bits and grooving tools. A green or diamond wheel is needed to shape them though.
The drill shanks can be hardened by heating them up until they cease to be magnetic and then dropping them into a tin of old oil.Best Regards:
BaronJ.
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10th July 2014, 10:47 AM #6Mechanical Butcher
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I can't visualise a re-purposed drill bit being used as a boring bar.
Anyone got a photo?
Jordan
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10th July 2014, 11:46 AM #7
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10th July 2014, 02:44 PM #8Mechanical Butcher
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Thanks Dean,
So, the unfluted portion of the drill bit is used?
But that's not hard, so I'm still confused.
Jordan
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10th July 2014, 03:10 PM #9Senior Member
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No, The fluted part is ground down.. Like this .
boringbar.jpg
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10th July 2014, 03:28 PM #10
There is also a small part of the drill shank that is hard and any unusable HSS tool can be used. I have a planer blade about 400mm x 100mm x 12mm. I should have 2 of them, 1 broken. They came from a timber mill. I have cut off a piece and made a lathe tool from it.
Dean
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10th July 2014, 05:17 PM #11Mechanical Butcher
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11th July 2014, 08:39 AM #12
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11th July 2014, 10:38 AM #13Mechanical Butcher
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I guess you give it a bit of a heat treatment, to make it hard?
From what I read, HSS isn't as easy to harden in the home workshop as carbon steel.
I accidentally used some HSS to make a tool to undo a special nut. I thought I was brazing on some mild steel. When I tried to then turn it in the lathe, I discovered that the stuff had become glass hard.
Jordan
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11th July 2014, 11:09 AM #14
In my case and also as far as I aware all the others, it is the hard sections being used for the cutting surface. The soft section is simply used for clamping purposes, if it works out that way. It does not matter tho. Use it however it seems to work best. The point is, in my opinion to make use of free HSS quickly and easily.
Dean
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12th July 2014, 12:21 AM #15
Hi Jordan,
With things like drill shanks, silver steel or gauge plate, the trick is to get the part that you want to use as a cutter sufficiently hot enough that a magnet no longer attracts it, then to rapidly quench it. Usually in oil or sometimes water. As you have discovered it becomes glass hard. Often it's too hard and will chip or break easily, so you have to let it down by tempering. Often its just a matter of heating up to a much lower temperature and cooling it down more slowly.
I've had cheap drills that have been so hard that the cutting edges simply chip off making them useless ! They are also hard to sharpen because you just can't get a good edge. Some carbon steel tools are like that as well.Best Regards:
BaronJ.
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