The Home Machinist!

Does anyone have an idea on how to remove a 3/64" diameter drill tip, about 1/8" long, from 360 brass? Or a shop that can do it? There are shops around here that offer spark erosion removal services. But, they only go down to 1/8" diameter or a #5 screw.

Dave

if I recall ,there are several other post's on how to do this, I removed a broken tap using acid (battery) from a brass casting. Worked very well, took 2 days, acid was cut with water, casting is now finished pump( water).

Here's the thread you want to read:

http://www.chaski.org/homemachinist/vie ... al#p203721

I used this method to remove a broken 3-48 tap in a piece of stainless. It takes a while, but, it worked and I saved the part!

David

I believe that you can use alum (hydrated double sulfate of aluminum and potassium) available at the grocery store. It will attack steel but not brass. I believe I have used it in the past to remove a broken tap. Google "using alum to remove a broken tap".

Thanks for the tips. I knew that it there was anybody who knew about removing broken taps or drills it would be the Chaski bunch. Ha! Ha! Anyway I'll try the alum technique. I wonder if layout dye would be a viable barrier to the alum solution to prevent discoloration.

Dave

daves1459 wrote: ↑Wed Sep 19, 2018 8:41 pm .... I wonder if layout dye would be a viable barrier to the alum solution to prevent discoloration.

Dave

perhaps something sturdier ... Lacquer, nail polish [don't tell the wife ] ?

I've used alum to dissolve a broken tap in a brass part for a pump I was building. I put the part in a small crock pot with water and alum and left it on low for a couple days. The tap turned to mush and washed right out of the hole.

I found alum at WalMart (but not at Publix or Kroger).

I have used the Alum trick also, the trick is to keep it heated, It is also helpful to keep picking at the tap with an old scribe. it seemed to work better for me.

FWIW: I use white vinegar with a 'pinch' of salt tossed in.

if all else fails and it is an important ($$$) part -> find someone with an EDM DRILL.

You've got lots of options, as there are many things out there that will eat away at the steel but not the brass.
We used to hang onto broken carbide drills and end mills at our machine shop, as we found that a single relief could be ground into the end and at high speed in the mill it could be plunged into the hole and it would cut through the HSS broken off in a part.
With a #3 thread through, chemical disolving would be the best bet.

It works! The alum in hot water did an excellent job of removing two broken 3/64" drills stuck in the brass cab door of my NYC&HR 999 project. The door is 1/4" thick x aprox. 2" wide x aprox 7" long. I broke two 0-80 tap drills for one of the doll house hinges I using to attach the door. I put about an inch of water in glass bread loaf baking dish and dissolved about one pound of alum. I painted the door with everyday Krylon rattle can paint masking the hinge seat with the two broken drills. When dry rested the door on two 1/4" scrap brass bars in the alum rich solution, covered the dish with aluminum foil, rested a piece of flat steel on the foil and put the whole lot on a counter top toaster oven. A chemist friend told me the rich alum solution raised the water boiling temperature by 10 to 20 degrees so I set the thermostat at 220F. I'm not sure how long it took to dissolve the drilsl. I cycled the mixture at 220F for 30 hours over a three day period turning the oven off over night. Upon inspection after the 30 hours I found the drills to be gone. The process is amazing and didn't dimensionally affect the door including the other four 0-80 tapped holes for the other hinges. I found a few things interesting:
1. I could dissolve one pound of alum in an inch of water in the load dish.
2. When hot the solution looks like aeriated tap water. When cooled to room temperature the solution solidifies to soft solid mass that resembles the paraffin wax my Mom used to seal her preserves when I was a youngster.
3. When clean steel is in the solution it fizzes like an AlkaSeltzer. The least little oxide or other coating and the chemical reaction stops.
4. The painting of the door was a waste of time. The Krylon may be porous as the door still discolored. But, the discoloration was minimal and easily removed with 320 grit emery cloth.
5. I wonder if the solidified solution can be stored and reused at a later date? Or will it corrode or foam or grow mushrooms or something.

Dave

The solution will keep pretty much forever.