Old drill bits as lathe cutters?

[oohsam]

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

[nadroj]

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

[Oldneweng]

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

[oohsam]

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

Perfect!!
I knew the shanks are not HSS hard, but yes, I was thinking boring bars or bits that go into homemade holders.
I will play around with the grinder.

Cheers.

[BaronJ]

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.

[nadroj]

I can't visualise a re-purposed drill bit being used as a boring bar.
Anyone got a photo?

Jordan

[Oldneweng]

I can't visualise a re-purposed drill bit being used as a boring bar.
Anyone got a photo?

Jordan

We were talking about a cutting tip to fit into a boring bar Jordan. Homemade boring bar with a drilled hole for the cutter.

Dean

[nadroj]

Thanks Dean,

So, the unfluted portion of the drill bit is used?
But that's not hard, so I'm still confused.

Jordan

[oohsam]

Thanks Dean,

So, the unfluted portion of the drill bit is used?
But that's not hard, so I'm still confused.

Jordan

No, The fluted part is ground down.. Like this .

319160

[Oldneweng]

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

[nadroj]

No, The fluted part is ground down..


OK, it's just where the shank joins the flutes.
I guess it's easy enough to figure out where the "softness" ends, with a file.

Thanks,
Jordan

[BaronJ]

I can't visualise a re-purposed drill bit being used as a boring bar.
Anyone got a photo?

Jordan

No pictures, but I've re-shaped the end of drills as cutters for all sorts of applications, from flycutting to punches for making brass washers. It's tool steel ! Just shape it to do the job in hand.

[nadroj]

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

[Oldneweng]

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

[BaronJ]

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

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.

[nadroj]

It's annoying when I buy a cheap tool that looks the goods, only to find it's been hardened but not tempered.
I had a "Dixon" (copy of Dickson) tool holder smash like glass. Heck, it probably didn't even need to be hardened.

Jordan

[BaronJ]

It's annoying when I buy a cheap tool that looks the goods, only to find it's been hardened but not tempered.
I had a "Dixon" (copy of Dickson) tool holder smash like glass. Heck, it probably didn't even need to be hardened.

Jordan

Hi Jordan,

That must have been frustrating ! I hope the supplier replaced it or refunded you. The price of those things, I would have been most upset.