Today's mission: recover from my most recent broken drill fiasco (described in some detail back in
post #161).
This time, rather than painstakingly doinking around with a 1/16" end mill (that I'd likely break) to mill around the bit, I decided to go with the concept that that Tim used to remove his broken center (
see that thread here). I made the basic tool from a piece of 1/4" W-1. I drilled a center hole about 20 thou bigger than the actual size of the drill bit so I didn't have to be perfectly aligned and turned the outside down to 5/32". All I needed was to leave a hole small enough I could make 1/4-20 threads in it. But I wanted it big enough it wasn't likely to break!
So after a simple turning exercise, I took my donut drill blank to the mill to make some teeth. I did this following other people's examples. I decided to go with 4 teeth, though I think that only one did most of the work.
Here's a close-up shot. I used the square collet block to cut 4 theeth.
After cleaning them up a bit, I used a file to make a little relief behind each tooth, then I heat treated it. Here it is, post quench:
I knocked the scale off of it then tempered it (as best I could anyway), then did a little careful honing. It almost looks dangerous!
Low and behold, it actually cut!
Not super well, mind you, but good enough. And since there was very little room for chips in the end of the tool I had to clear chips quite often, once the teeth got burried.
Here we are all done. the plug is sitting right next to the hole. The plug was stuck in the end of the donut drill and I had to knock it out.
Then I made up a short 1/4"-20 plug and preped for silver soldering. The white stuff is flux. Though the tube looks quite filthy here, the area around the hole (under the flux) is actually bright shiny clean metal.
I screwed it in, dabbed a bit more flux on, and put a circle of silver solder around the plug. This soldering job went MUCH better than my last. I was able to heat it from the bottom so that the top didn't oxidize so much. I think this was a great help. It was cool to watch the solder suddenly melt and suck into the seam.
Its sitting out in the shop cooling now. Next I'll file down the plug and drill the hole right this time!
I tell you, making that little donut drill tool and seeing it work was more fun than it had any right to be! That was pretty fun!
Thanks for your watching,
Kim
