Now What?

[MrWhoopee]

Plunging a 4mm carbide endmill into some semi-hard material (Rc44-48), it suddenly snapped off flush. Now what? I could have just scrapped the piece, but I don't give up that easily. Fortunately, I had access to the opposite side, so I grabbed another 4mm endmill and started in. I wasn't sure how deep the broken piece was, and I knew if I made contact I would lose a second carbide endmill in the bargain. I fed very gently down, retracting and blowing the chips frequently, looking for any sign of something at the bottom of the hole. Then I took a pin punch and a big hammer to it. Back to the mill and plunge another thirty or so, then more punch and hammer. Lather, rinse, repeat. After 6 or 7 cycles, the stub of the broken EM fell out. I was able to pick out the remaining pieces and finish the hole. Sometimes you get lucky.

 

[jwmay]

This was better than a movie! If only there had been a beautiful but contrary woman with cutting wit and a motorcycle to round it out.

 

[cathead]

Good job! I can relate to your post completely. I remember hard times in the shop drilling out
broken taps with a carbide end mill and finally winning and getting to finish the piece I was working on.
It's all part of the game. Yesterday I was making a small part using a piece of a chain saw file and was
on pins and needles wondering if I was going to break the carbide mgmn 150 insert. I had to diamond
file the insert several times to get the job done. When you hear the insert screaming in pain, you know to
back off and resharpen.

 

[jwmay]

I spent three days hiding from a broken off stud in an aluminum threaded hole. Sadly, my tale didn’t end as happily as yours. Nuff said.

 

[RaisedByWolves]

I spent three days hiding from a broken off stud in an aluminum threaded hole. Sadly, my tale didn’t end as happily as yours. Nuff said.

I broke a 2mm tap in a tiny aluminum helicopter part I had about 10hrs worth of work into.

Literally the last step and I underestimated how long the mill spindle would coast with only that tiny tap for resistance.

Used a solution of alum powder dissolved in battery acid and heated slightly.

It took two days as the tap was buried to the hilt preventing good flow of the solution, and I had no way to keep the heat on other than when I was watching it.

Part turned out beautiful and I’ve used this method several times.


This was another heli part I used this method to salvage. This was a screw that I needed to use to cut its own thread into a very thin aluminum motor mount.

This time I used more heat and had it out in a couple hours. I used this video as a demonstration for someone on an RC heli group as proof it would not harm the part, just eat the steel screw.


Some older and historically valuable Heli’s are literally made out of unobtainum as they were manufactured in the early 70s and the company’s long defunct.


This part in the video had 1.5mm walls and a 2mm base milled out of a solid block of 7075 using jigs and special cutters. Probably 1” wide and .800 from side to side. Again, probably 6-8hrs of work.