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Regrinding broken taps into punches

Myrmidon

Cast Iron
Joined
May 5, 2010
Location
Wisconsin
There was a really good thread I read on here, found on accident about this topic. I can't find it, so excuse me, but I really would like to get some thoughts on this or be directed by someone who's search skills exceed mine to where the information is.

I am going to be making some pin punches, center punches, and taper punches from various extended length taps. Now I have been torch tempering the struck end so they don't let loose and give me a tool steel money shot.

I was wondering what color temper and corresponding Rockwell hardness I should get the struck end too for safe use?

Any advice would be fantastic,.I am currently getting the end deep blue/purple after holding it at cherry for a minute or two and letting it air harden.

I can sort of file the end on some. Wondering if that's good enough and I am over thinking it or not.

Thanks guys.
 
Heat treatment of high speed steels is completely different from carbon steels. This is a bad idea. Make your punches from carbon steel, preferably a known alloy with instructions from the manufacturer.
 
Alright that's a fair assessment given what else I've read on heat treating HSS, outside of a controlled setting.

But then I still am wondering how hard should the end of a punch be? Full Soft? Or should it be hard, just not as hard as the tip?
 
Agreed, bad idea. Also just heating the struck end is probably not enough. Both ends take punishment.
In my misguided youth I tried grinding punches taken out of service from cold heading machines. They worked great right up till the point one let go and put a bit of shrapnel in my finger.
 
If you don't want to toss good steel, consider making scribers or engravers. HSS is suitable for both. I often use a simple conical point in HSS to cut lines in dials, etc. I just put it in a collet in the mill and slide the part under using X-Y. HSS is also useable as-is for custom broaches and tool bits. I agree with the others, punches are going to be a disapointment.
 
I agree with all the above. I tried making gravers (small chisels) out of some 15 yrs ago. I still have a shrapnel scare on my hand from one. I make spring pin punches from S7 with decent results. The right material is cheaper than the wasted time and stitches. I tried being cheap and repurpose/diy stuff for a long time. I just wound up with a lot of wasted time and piles of worthless crap. When I make my own tools it’s because I can’t find anything to fit my standards.
 
I've re-purposed so many small round tools over the years the count must be many dozens. An example would be when a small screw gets busted off flush or slightly below, like insert screws and insert clamp screws. I usually grab any small 1/8" shank HSS left over from a small end mill and grind a chisel end on the broken end, this is used to tap at an angle to unscrew the screw after a drop or so of Kroil.
Those Starrett pin punches are made of med/high carbon, so when the 1/16" punch bends or breaks they make great screw tickling chisels, get the end red and quench in water, temper to suit., then grind the chisel end.
It helps to use a 10X loupe, and of course for 10-32 through 4-40 screws a tiny ball peen is all that's needed.

One thing that gripes me is when someone breaks a HSS tap or drill off and I draw the straw to remove it. Who uses carbon drills and taps anymore? They were great for that though because you can draw the temper out and drill them out with any old HSS drill, especially left hand drills.

they don't let loose and give me a tool steel money shot.
Is that referring to the money to emergency rooms to remove shrapnel out of the eye?
 
Another good use for broken taps, like Gordon's conical point to cut dials, I use the point to locate intersecting lines to drill. Then use the same point to mark the work with a bit of down pressure on the quill. Works similar to a spotting drill for small bores.
 
make punches from S-2 or A-2 or whatever . retarded to try to heat treat
broken taps .

if it has to be done... just grind the broken tools to shape in the first place,
and don't pretend to know how to re-heat-treat the mystery fucking thing.

better off that way .

remember some old fuck attempting to "retemper " some piece of junk screwdriver
by "quenching' it after he burnt the piss outta' it on a bench grinder....?

it never worked.
 
If you hit a hard punch with a hard hammer is when things can go bad. The common thing is to have a hard hammer and soften the struck end of the punch, like OP is wanting. The other way, I believe stone carvers used to or maybe still do is use hard punches (hard on struck end as well as working end) and a "soft" hammer made of steel. I think the soft hammer sticks better to end of the punch than the hard hammer/soft punch. Not saying one way or the other about reworking HSS....
 
If you hit a hard punch with a hard hammer is when things can go bad. The common thing is to have a hard hammer and soften the struck end of the punch, like OP is wanting. The other way, I believe stone carvers used to or maybe still do is use hard punches (hard on struck end as well as working end) and a "soft" hammer made of steel. I think the soft hammer sticks better to end of the punch than the hard hammer/soft punch. Not saying one way or the other about reworking HSS....


Yeh that's pretty much what I've been doing for center punches, I just temper the end that gets struck so I can file it. Though based on the consensus that's a bad idea I am going to just make new center punches, and the punches I was going to make from O1 or something.

I'd rather not lose an eye or whatever.
 
Yeah... BAD IDEA!! PLEASE DON"T DO IT!
When I was an apprentice another apprentice and myself were working alone on a Saturday morning to try get in as much overtime as possible. His workbench was close to the kettle so I walked past him to make some coffee. He had ground a broken tap into a centre punch and tried to heat treat it himself. This same punch he struck into a part as I walked past... a tiny piece of HSS came off it and hit me directly on (my damn bad luck that day) the main vein, the one you would donate with, on my arm. I have never seen a thin stream of blood shoot that far before. Before I realised what had happened I had squirted blood all over the place.

Anyways, tried our best to patch it up with the first aid kit and he drove me to hospital. By this time I was already feeling a bit woozy. At first the doc didn't believe us and thought that we had tried to inject ourselves with something (could have been our scruffy overalls, safety boots and 19 year old baby faces). After getting the bleeding to stop I( was sent for X-rays to see if it was still in there, and the damn thing was. They had to knock me out to remove it because it was so tiny.
 
I got my lesson using an old end mill to push a pin out of a shaft. No damage done but it showed me the potential for high impact flying steel.

Don't do it !!
 
Here is info on hammers from a stonecarver site:

The hammer on the far left is designed for use on granite and has a hardened steel head. It is used with chisels with untempered ends and will cause the chisel to mushroom over. To the right of it is a lump hammer with a soft steel head. It can be used with chisels that have tempered ends, and in this combination, the hammer head will mushroom over. Never use a hardened hammer with a hardened steel chisel end. Striking too hard with this combination could cause metal fragments to fly off the end of the chisel like shrapnel.

Other info there on chisels etc:
Stone Carving Tools
 
I have had good success using broken tap or endmill as a center punch. The way I do it is to press fit it into a piece of mild steel, so the hard stuff is an insert of sorts. You can hammer on the punch without fear of it shattering but still take advantage of the hard steel tip. It was my first boss as an apprentice who put me onto this idea.
 
This sounds like a good way to lacerate your hand when the tap shatters. Make your punches out of S7, harden and draw back to around Rc57, and use a copper hammer.
 








 
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