What drill bit for spot welds?

[HOWDY69]

I know I have seen posts about a good drill bit to use for drilling out spot welds but I can not find the post. What do you folks use?

[theogre5150]

They actually make a special bit for drilling out spot welds. Not sure where to tell you to look for one. Try northerntool.com.

[fordman]

mac has one also. but kieth said they werent much good that another drill bit worked just as good for him.

[theogre5150]

I just used a regular drill bit. Took my time with it and it worked just fine.

[heep70]

I use spotweld bits. Get one that is a tad bit bigger in dia then then weld. The weld itself is harder and will eat the bit.

[Whoaaanelly]

Eastwood sells spotweld bits, but I've been making mine for years. Take a decent 5/16" drill bit and using your bench grinder and a LOT OF WATER and grind the bit in reverse of the way you normally would, but leave a center part of the bit as a guide. I know, you're going "What?" I learned this when I apprenticed in the tool shop 25 some-odd years ago, but it's the same bit used for drilling perfect round holes in sheetmetal. I'll sketch what I'm talking about and edit this post so you can see what I'm talking about. Essentially, if you keep the drill cool while grinding it, it'll hold it temper.



This is similar to what you'll see for drilling wood, but it's different a little. I drew this in Photoshop from memory, but I think I should take a picture of one I've done. The center part in this sketch is way to big.

[fordman]

a left handed drill bit?

[Whoaaanelly]

Doesn't need to be to drill spot welds.

[Banjo]

as mentioned, they do make a special spot weld cutter, I have one, but forget who makes. Center point is kinda like metal spike on an old metal compass like we used in school and it has little round saw tooth band around exterior. You drill a small pilot hole (real small) and poke this sharp metal center "locator" in the small hole and this round toothed band spins in circle and makes hole, removing the spot weld. Ok, it just came to my old mind, it's made by Blair I think. Maybe they'd have at auto body supply house??

[foghorn]

I always prefered to use aircraft bits they have the hardest steel i have found drill first with a bit about 1/8 in size then i like to use a bit big enough to cut the top layer example 3/8 and not go all the way through. kinda like making a counter sunk hole for a screw head. Lots of times you will see it brake loose while drilling. If not just take a flat blade screw driver and pry a little 99% of the time they will come loose. The smaller the hole you make the less weld you have to do also.




Foggy

[Whoaaanelly]

I don't ever drill a pilot hole with the bits I grind. I know I still need to take a picture of one, but they only take the top layer of metal off and you can easily see when you pop through to the second layer. Leaves a perfect recess to spot weld (I use my MIG and just pull the trigger to fill it back up). A little grinding and it's just like factory.

OK... I'll have a picture posted tomorrow.