Author Topic: Anyone repair a hammer drill spade or chisel bit?  (Read 2797 times)

Offline Linteiev

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Anyone repair a hammer drill spade or chisel bit?
« on: November 28, 2019, 01:19:38 pm »
I'm looking at a spade bit for an SDS Max hammer drill that snapped clean in half within a few minutes of use, it's already been replaced but I've been considering welding it back together and then try to break it through use just for the giggles. I have a few ideas of what I would do but wanted to see if anyone else has met with success or failure with a similar repair.
« Last Edit: December 09, 2019, 11:06:43 am by Linteiev »

Offline RichColvin

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Re: Anyone repair a hammer drill spade or chisel bit?
« Reply #1 on: November 29, 2019, 12:13:41 am »
I recommend against that.  I can not believe it will come out good. 

Kind regards,
Rich Colvin - a reference guide for sharpening

You are born weak & frail, and you die weak & frail.  What you do between those is up to you.

Offline Mackdan

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Re: Anyone repair a hammer drill spade or chisel bit?
« Reply #2 on: December 17, 2019, 04:57:35 pm »
If you have the time and energy to try welding this back together, try it. The only thing you might loose is your time and the cost of a welding rod. Arc welding will probably have the highest chance of success if you can get a good welding rod match. You see arc welding in the field for the repair of bulldozer blades and backhoe shovels all the time. Same basic steel arrangement- The body of the drill should be a "tough" steel to deal with the loads of drilling. The front cutting edges should be hardened steel to deal with hitting the concrete. So you should be able to weld the body of the bit together with more success. But welding produces harder material in general which is brittle, so the bit will likely break at the weld in the future. You can increase your success by changing the steel in the weld zone with follow up heat and cool. But local to the weld zone, not the hardened tip. Heating and cooling the tip will soften that steel and make the bit dull very fast. What exactly is needed is anybody's guess. You would really need to talk to a materials engineer who is versed in steel to find the right temperature to heat to (which is the key), then cool fast in water.
Alternately You can try hammering the weld with a ball peen to toughen it and reduce some of the stresses. Which is part of the arc welding cleanup, so that's another reason to use arc welding.
FYI, this is my 1st post on the forum. But I have a BSEE, and one materials engineering course, and my brother has a MSME in materials, so I do know a little about the subject.
« Last Edit: December 17, 2019, 06:39:52 pm by Mackdan »