Drilling welded stuff

[FinnFlyer]

One of previous builders had drilled the pivot and push tube holes in the elevator horn (Wd-405R weldment) 1/8 to 3/16" off. So I figured I'd just weld them shut and drill new holes in the proper positions.

Easy enough to weld them shut with oxy/acetylene Henrob torch.

But I'm having a heck of a time drilling the new holes. Dulls my bits without making any real progress.

Is it just because I have crappy bits or is that a common problem?

I'm thinking about ordering carbide bits. How many pounds of pressure do I need to apply on 1/16" bit? 3/32" bit? 1/8" bit? 3/16" bit?

Finn

[JonJay]

It should drill just like it did to start with. It is possible that you didn’t have your torch set for a neutral or non carborizing flame. Also, I am not sure but assume the steel is 4130, but unlike mild steel, it can be heat treated and hence, hardened. If you simply welded it, and let it cool in free air, it shouldn’t harden.

I do not believe Vans heat treats this part. I know many have successfully welded and redrilled these parts. However, you may wish to check the plans for material type and if there are any post fab treatment or call Vans.

[jrs14855]

You have probably air hardened the part. Heat the filled area to cherry red, then very slowly back the torch away until the area is no longer red. I have good luck with the so called titanium drill bits from Lowes. I would start out with a 3/32. Some lubricant may help.

[FinnFlyer]

Originally Posted by JonJay

It should drill just like it did to start with. It is possible that you didn?t have your torch set for a neutral or non carborizing flame. Also, I am not sure but assume the steel is 4130, but unlike mild steel, it can be heat treated and hence, hardened. If you simply welded it, and let it cool in free air, it shouldn?t harden.

I do not believe Vans heat treats this part. I know many have successfully welded and redrilled these parts. However, you may wish to check the plans for material type and if there are any post fab treatment or call Vans.

It's 4130. No special treatment specified.
I was worried about heat spreading to the alum it's riveted to so I did squelch it with a wet rag. Would reheating it to a deep red and letting it cool naturally bring it back to it's original hardness?

Finn

[Ted RV8]

Rapid cooling with a wet rag hardened it.

[BillL]

Originally Posted by jrs14855

You have probably air hardened the part. Heat the filled area to cherry red, then very slowly back the torch away until the area is no longer red. I have good luck with the so called titanium drill bits from Lowes. I would start out with a 3/32. Some lubricant may help.

+1 Absolutely correct. Just heat red and let cool slowly and you will be fine. I TIGed some holes with a copper backing and it was hard as a rock!!! The cobalt drill bit would not touch it, even with lots of pressure on the drill press. After annealing, just like normal with the same bit.

[FinnFlyer]

Thank you all. I'll try that tomorrow.

Finn

[N941WR]

You can put a wet rag on the aluminum but as mentioned, when you hit it with the weldment with the rag you hardened it. This also makes the steal very brittle. By heating it and letting it cool, as described above, you will return it to its "normal" condition.

[FinnFlyer]

I annealed it and was able to drill the holes. Still somewhat hard to drill. Either bad bits or didn't get it quite hot enough.

Finn

[snopercod]

I had to drill several hundred holes in some cold-rolled 304 stainless steel bars. My machinist friend turned me on to Gurhing screw machine drill bits. I bought them from www.mscdirect.com and they did an amazingly good job. I highly recommend them for drilling tough materials. $13 each, but darn well worth it. The particular ones I bought were.

Guhring - 13/64" Diam, 130? Point, Right Hand Cut, Parabolic Flute, Screw Machine Length Drill Bit - Cobalt, TiN Finish, 26mm Flute Length, 62mm OAL, Straight Shank