# Can a spot welder be used for spot annealing hard steel for drilling?



## gunsmither (Aug 20, 2022)

I would like to be able to spot anneal both jaws of a small Visegrip type plier to drill a 1/16" hole to use a drive nail to secure an aluminum insert to the pliers.
Currently I am annealing the entire jaw, which works fine, but a spot anneal would be much faster I believe, as only a small area needs to be softened.

Curious if anyone here has ever used a spot welder to anneal hardened steel for drilling a small hole? Or is it even doable with a powerful enough spotter?
Any experienced ideas, help, suggestions, etc. welcome.

Thanks for looking! Joe


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## extropic (Aug 20, 2022)

Interesting idea Joe. If the spot welder in question has enough juice to weld material equal to (or greater than) the jaw thickness, I don't see why it's not worth a try.

If you try to get by with a lesser spot welder it had better be protected by a thermal overload device.

How thick are the jaws you're talking about? Are the OEM jaws through hard or case hard?


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## brino (Aug 20, 2022)

Perhaps another method of spot annealing........

I posted one here:
https://www.hobby-machinist.com/threads/spot-annealing.78098/post-662749

...and this response said it worked:
https://www.hobby-machinist.com/threads/spot-annealing.78098/post-664896

Brian


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## RJSakowski (Aug 20, 2022)

Annealing requires the temperature to drop slowly.  I would expect that a spot welder wouldn't allow that time.  If you adjusted the current to avoid taking the spot to a temperature below the hardening temperature, you could probably draw the temper sufficiently  to soften the spot enough to drill with repeated shots.

I have successfully drilled small holes in hardened steel using carbide p.c. drills.


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## gunsmither (Aug 20, 2022)

RJSakowski said:


> Annealing requires the temperature to drop slowly.  I would expect that a spot welder wouldn't allow that time.  If you adjusted the current to avoid taking the spot to a temperature below the hardening temperature, you could probably draw the temper sufficiently  to soften the spot enough to drill with repeated shots.
> 
> I have successfully drilled small holes in hardened steel using carbide p.c. drills.


Thanks RJ. If a large enough spot welder would get the metal to a dark blue color, it would drill just fine most likely. The plier jaws are about
5/16" thick. I have used small solid carbide drills many times in case hardened and thru hardened gun parts, and on these pliers, but the jaws still need to be softened for the drive nail to dig in. When annealed, I have also drilled and tapped for 2/56 binder head screws in my CNC mill, but thats too slow a process.


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## gunsmither (Aug 20, 2022)

extropic said:


> Interesting idea Joe. If the spot welder in question has enough juice to weld material equal to (or greater than) the jaw thickness, I don't see why it's not worth a try.
> 
> If you try to get by with a lesser spot welder it had better be protected by a thermal overload device.
> 
> How thick are the jaws you're talking about? Are the OEM jaws through hard or case hard?


Thanks extropic. The jaws are about 5/16" thick at the point where the drive nail goes in. The jaws seem to be thru hardened powdered metal, as they drill almost like cast iron with little bitty chips. Currently I'm using a hand held Venom HP Induction Heater to heat the jaws up dull red and allow them to cool. Works great, but messy from residual oil burn off. I believe it will take a pretty hefty spotter to do the job. Only needs to go to a dark bluish color to soften enough.


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## Flyinfool (Aug 20, 2022)

I once had to drill and tap 4 holes through hardened steel. HSS and Cobald drills did not even scratch the surface. I had to use a solid carbide drill to drill the holes. Then before tapping I put an old drill bit shank of the proper size into the hole and heated the drill to bright red with a tourch. I kept the heat there for about 10 minutes and then slowly reduced the heating of the bit to allow the surface of the hole to cool slowly and hopefully anealing it. I assume it worked since I had no issue tapping the 4 holes with a quality HSS tap.


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## gunsmither (Aug 20, 2022)

brino said:


> Perhaps another method of spot annealing........
> 
> I posted one here:
> https://www.hobby-machinist.com/threads/spot-annealing.78098/post-662749
> ...


Thanks for the links brino. Very interesting ideas. I have repointed many different firing pins using carbide drills to drill into the main body, usually
without annealing, just cutting off the broken end. I then used a close fitting piece of pre-hardened spring steel rod from a Brownells kit. I cut the
new pin tip a bit long, then fit to the bolt for precise length of .055" sticking out beyond bolt face if I recall, and round out the tip and polish it. Secured the new tip with RED Loctite. Never had one fail that I know off. Used to solder them until I tried the Red LT, it is amazing stuff.


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## gunsmither (Aug 20, 2022)

Flyinfool said:


> I once had to drill and tap 4 holes through hardened steel. HSS and Cobald drills did not even scratch the surface. I had to use a solid carbide drill to drill the holes. Then before tapping I put an old drill bit shank of the proper size into the hole and heated the drill to bright red with a tourch. I kept the heat there for about 10 minutes and then slowly reduced the heating of the bit to allow the surface of the hole to cool slowly and hopefully anealing it. I assume it worked since I had no issue tapping the 4 holes with a quality HSS tap.


Thanks Flyinfool. I have used this method to spot anneal case hardened bolt action military rifle receivers. Works great!


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## Flyinfool (Aug 20, 2022)

gunsmither said:


> Thanks Flyinfool. I have used this method to spot anneal case hardened bolt action military rifle receivers. Works great!


HA!!!  That is also what I used this method on for scope mounts. But this Swedish M96 felt like it was hardened through not just case.


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