Drill first, weld after?

Whoops. While fabricating a new track bar brace (had to throw out the old one as it didn't fit with the V8), I accidentally welded the frame side mount BEFORE drilling the mounting holes *sigh*. Now the plate is heat treated and the bits that had no problem drilling the previously mild steel, won't even dent it. Is there some witchcraft I might employ to get these two 1/2" holes drilled, or do I have to build a whole new mount?

Sounds weird to me I've never heard of that happening. Why not just weld the brace and forget about bolts?

I've been welding, for a living, for about 8 years now and have never heard of this happening. Sounds to me like your bit needs sharpened.

If it was mild steel, it still is. If it was A2 tool steel, you will need a sharper drill bit.

BNJeepsta said:

I've been welding, for a living, for about 8 years now and have never heard of this happening. Sounds to me like your bit needs sharpened.

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This....get a new bit or sharpen the one you're trying to use. I also can't stress enough proper drill RPM for the bit size you're using and material you're drilling. I see people all the time complaining about their bits wearing out or drilling triangular holes while trying to use something like a 3/4" bit at 1,000 RPM lol

Muhdunno. Destroyed 5 or 6 bits instantly trying to drill that plate. Barely any pressure at all. Tried another bit on another chunk of unheated plate, and went through like butter. Used the same bit on the heated stuff, and toast again instantly.
Built a new mount and all the holes drilled fine. Dunno wtf but this happens every time I weld something real hot. It's a small mount, but all 1/4" thick, so the heat gets through everything, and then none of my bits work. Also tried a brand new $25 carbide bit (9/32") and it was dull almost just as fast. Sharpened it back up and drilled 4 more holes through some more 1/4" plate, then dulled it again as soon as it got near the heated plate.

Sounds like work hardened material, not heat treated.

Same metal cut from the same plate. I'm not arguing that I'm right or anyone is wrong, just trying to make clear what is happening.
Mild steel, weld it (edges) real hot, let it cool, can no longer be drilled by any substance known to man (or at least known to me). Doesn't matter if I'm trying to drill the weld or anywhere else on the plate. Same result every time.
Same steel from the same flat bar, cut another chunk off, drills fine. Get it real hot with the welder, let it cool, can no longer drill. I'm sure there's a good metallurgical reason for this.

Also, using the same drill press, the same drill bits, same speed, same press pressure. This is completely repeatable every time.

Georgia Mike said:

This....get a new bit or sharpen the one you're trying to use. I also can't stress enough proper drill RPM for the bit size you're using and material you're drilling. I see people all the time complaining about their bits wearing out or drilling triangular holes while trying to use something like a 3/4" bit at 1,000 RPM lol

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ALL drill bit holes are off-round. The pro's, and people who fallow the pro's, undersize their holes, then ream it to final dimensions.

As far as busting out the drill speed chart for every hole... you have fun with that!

xcm said:

ALL drill bit holes are off-round. The pro's, and people who fallow the pro's, undersize their holes, then ream it to final dimensions.

As far as busting out the drill speed chart for every hole... you have fun with that!

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Yes I realize this. I'm a machinist, after all. I was making a generalized comment as to why some people have issues. And you don't need to bust out anything to calculate exact feeds and speeds, but some common sense goes a long way.

If you have an O/A rig and a rosebud, or even a MAPP torch, try annealing it. Heat it red-hot and let it cool as slowly as possible. Depending on the mass of the material that needs to be annealed, it may cool too quickly to work out though.

blistovmhz said:

Also tried a brand new $25 carbide bit (9/32") and it was dull almost just as fast. Sharpened it back up and drilled 4 more holes through some more 1/4" plate, then dulled it again as soon as it got near the heated plate.

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Know anybody with a 7mm Magnum?

:gee:

blistovmhz said:

Same metal cut from the same plate. I'm not arguing that I'm right or anyone is wrong, just trying to make clear what is happening.
Mild steel, weld it (edges) real hot, let it cool, can no longer be drilled by any substance known to man (or at least known to me). Doesn't matter if I'm trying to drill the weld or anywhere else on the plate. Same result every time.
Same steel from the same flat bar, cut another chunk off, drills fine. Get it real hot with the welder, let it cool, can no longer drill. I'm sure there's a good metallurgical reason for this.

Also, using the same drill press, the same drill bits, same speed, same press pressure. This is completely repeatable every time.

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Not sure what you're doing, but I've never had that issue, and I have even welded up holes and re-drilled them....just make sure you have a sharp bit and take your time.

If drilling weld, it also helps to hit it with a grinder first so the bit hits fresh metal.

And maybe don't weld so hot ???????

Work your way up to a 1/2" bit.

Easy peasy.

Really not sure how it seems no one is really hearing what I'm saying....

I do two identical holes. One on the part that has been welded hot, and one that has not. Same size bits from same manufacturer. Tried several different make bits in several different sizes. Never have a problem with the regular mild steel, but as soon as it gets real hot and I try again, i don't own a bit that'll go through it.

The first **** up, I was drilling a pilot hole with 9/32 on the lower part of the mount before I welded it all together. Like butter. Stepped up to 1/4", then 1/2". All butter.
Forgot to drill the frame side mounting holes before welding the mount together. Let it cool down (ambient) and threw it on the **** press with the same 9/32 bit. Both hole locations are smooth with no weld slag. Bit barely dented it. Threw in another brand new 9/32 and tried the other hole. Again, barely a dent. Tried a brand new carbide 9/32 bit, nothing. Threw a new chunk of the same plate the mount was cut from, up onto the press, and every one of the 9/32 bits went like butter.

I am absolutely sure that I've ruled out any possible issues with the bits, or drilling process. It's the workpiece that's ****ed up, and I seem to do this ... somewhat often (every time I have to make mounts out of 1/4", where the weld seams are close to the material that will need to be drilled).

blistovmhz said:

Really not sure how it seems no one is really hearing what I'm saying....

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No...we hear what you are saying....

But you don't seem to realize what we are telling you......

No one else seems to have this problem.....so you must have some whammy dyne super dooper welder that hardens the metal as it welds.

(sure the drill press is spinning the right way ?? :roflmao

Got no ideas for ya........

blistovmhz said:

Whoops. While fabricating a new track bar brace (had to throw out the old one as it didn't fit with the V8), I accidentally welded the frame side mount BEFORE drilling the mounting holes *sigh*. Now the plate is heat treated and the bits that had no problem drilling the previously mild steel, won't even dent it. Is there some witchcraft I might employ to get these two 1/2" holes drilled, or do I have to build a whole new mount?

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You have half of the answer already. Now, to anneal the piece and move on.

https://en.wikipedia.org/wiki/Heat_treating

Odd thing is, I learned of this in high school metal shop, and my Dad's workshop, way back in the '70s. None of these high-faloutin' welders understand the pretty colors emanating from their weld area?

Hypoid said:

You have half of the answer already. Now, to anneal the piece and move on.

https://en.wikipedia.org/wiki/Heat_treating

Odd thing is, I learned of this in high school metal shop, and my Dad's workshop, way back in the '70s. None of these high-faloutin' welders understand the pretty colors emanating from their weld area?

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That's sorta what I was GUESSING, but I haven't really delved into metallurgy at all. Either way, problem solved (by making a new bracket).

blistovmhz said:

That's sorta what I was GUESSING, but I haven't really delved into metallurgy at all. Either way, problem solved (by making a new bracket).

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All heat treatment for basic steel depends on how hot it gets and how rapid or slowly it cools. High strength and low ductile metal is cooled very rapidly, or quenched in water or oil. Sometimes it will be reheated after it is quenched to enhance the strength.

MIG welding could get you close to some of that heat but I doubt you got anywhere close enough then cooled rapidly. The plate probably would have noticeably warped.

Live and learn arty:

Cobalt drill bits FTW eff the HSS bits.