Weld Seam

[Wargo]

I'm working on an 8"x8" piece of A500 rectangular tube stock, and one of the features is a 14mm hole that falls right on the weld seam. I drilled a pilot hole and then came in with an endmill to interpolate the hole to size. The drill missed the seam, but when the endmill came in and touched the seam, it just destroyed my tool. Now my piece is work hardened... 

My question is, how do I make this hole without busting endmills? I'm afraid that if I run a 14mm drill through it'll chip once it hits the seam.

[Leon82]

 

How is your approach circle Mill dynamic?

I would try ramp cuts.

[Wargo]

8 minutes ago, Leon82 said:

 

How is your approach circle Mill dynamic?

I would try ramp cuts.

I tried helical boring. It worked fine for the other holes, just not the seam. The endmill was a bit worn to begin with, so I'm hoping that if I throw in a fresh carbide EM it'll do the trick. But, my work hardened hole is still an issue.