Anybody welded on a core bit shank?

[Hersheyfarm]

I have an old spline drive core bit. Milwaukee. My current rotary hammer is sds max. Thinking about buying a cheap sds bit from harbor freight and welding it on. I have no ideal what metal it is. Hard stuff. The shank is not replaceable on this one. Any advise?

 

[5030]

Runout as well as destroying the heat treat will be an issue

 

[Root Cause]

Most bits in a machine shop are made of M2 commonly known as high-speed steel or HSS.
My experience is mostly TIG welding. Stainless sticks to almost anything.

My guess is that you won't be happy with the result as keeping both pieces aligned will be difficult.
I might spend my time looking for another solution but if you know someone with a lathe, you can chuck both pieces in the headstock and tailstock while you weld. Hopefully someone has a better idea but that's all I got. Good luck.

 

[5030]

you can chuck both pieces in the headstock and tailstock while you weld.

That can be detrimental to the lathe as the current flowing can cause grief with bearings and other stuff.

 

[mrmikey]

I've cut the shank off a smaller SDS bit and welded it to a larger oddball brand bitt. Used tig and ss rod, it held for the two holes we had to do. Only reason I did it was it was a 1/2 hour drive to town to buy a $$$$ bitt for two holes.

 

[2manyrocks]

odds of ruining what you have seen pretty high. Is there some kind of conversion adapter available?

 

[ROUSTABOUT]

That can be detrimental to the lathe as the current flowing can cause grief with bearings and other stuff.

Not if grounded right.

 

[5030]

Unless you have a rotatable ground clamp, I'd refrain from doing it. Not my deal so I don't much care actually. Never happen on any lathe I own.

 

[Hersheyfarm]

odds of ruining what you have seen pretty high. Is there some kind of conversion adapter available?

Actually there is. just ordered a Milwaukee one. Cheapest I found..$130. Have other bits to use it on. So we will put welding it on hold. I’ve already wrote off all these spline bits, so if this adapter holds up it could be a win. If not, we weld. I ain’t scared.

 

[Root Cause]

That can be detrimental to the lathe as the current flowing can cause grief with bearings and other stuff.

Maybe on some small lathe but they endure heat. As for grief, I guess you are saying side pressure but that is exactly what a lathe tool does- apply side pressure. If someone has a $200 mini lathe you may well have a point. My experience is with Leblond and Clausing lathes up to 25 hp and doubt 2 more generations can kill them. After going down this useless rabbit hole, the result is that doing this at all may not yield what the op needs.

 

[4570Man]

Unless you have a rotatable ground clamp, I'd refrain from doing it. Not my deal so I don't much care actually. Never happen on any lathe I own.

If it’s a newer lathe with digital instruments I agree it’s a bad idea. If it’s an older lathe without that stuff protect the bed from splatter and weld away. And put the ground clamp on the work piece.

 

[chim]

First thought I had was to cut the shanks and turn them to match the ID of a sleeve they'd both terminate in and weld the sleeve to the shanks. Don't know if it'd work or not, but it would help align the pieces.

 

[jwmorris]

I haven’t done any hammer bits but I have lengthened a lot of drill bits over the years. Have a number of fixtures for the task. Of course it’s easiest if the two pieces are the same diameter but it’s not a deal breaker if they are not.

 

[davisjt1977]

Actually there is. just ordered a Milwaukee one. Cheapest I found..$130. Have other bits to use it on. So we will put welding it on hold. I’ve already wrote off all these spline bits, so if this adapter holds up it could be a win. If not, we weld. I ain’t scared.

It is "I ain't skeered". (I think)

 

[Raul-02]

I have an old spline drive core bit. Milwaukee. My current rotary hammer is sds max. Thinking about buying a cheap sds bit from harbor freight and welding it on. I have no ideal what metal it is. Hard stuff. The shank is not replaceable on this one. Any advise?

If the bit is made from high speed steel ( any of the M grades) you can weld the living **** out of it and it'll be just fine; losing no hardness. Same with carbide. You can braze carbide and it suffers no harm.
If it's not HSS then you prolly didn't want to put it in your hammer drill anyway.

 

[TGM5040]

It would probably be easier to buy a spline drive to sds max adapter....

 

[yomax4]

Not sure how well it will work but there are Nickel Silver oxy-fuel rods "designed to extend hammer drill bits". Alignment would likely be critical. I've sold them in the past but never put them to the test for that purpose. Harris 14 and Weldcote Nickel Silver. Eutectic has one as well. Cool stuff that flows so thick you can braze overhead. I used to build small deer antlers with the stuff at shows.

 

[Hersheyfarm]

I got the Milwaukee adapter. It will work but adds a lot of length. One of my core bits already has a very long shank. I bet it adds another 8”.

 

[Tinhack]

I used to make special shapes out of drill rod then weld them to air hammer or power hammer shanks. I tried welding then re-heat treating after welding, but they always broke at the weld junction. Probably due to the high carbon content. That is, until I preheated both parts to yellow-hot before welding. I put a small tack weld(s) to hold them in place then heated. Weld them while yellow-hot. Let it cool before heat treating.