Bit broke off in lower

[calwoodbutcher]

1/8 inch bit broke off while milling an 80. About 1/2 inch of the bit broke off about 3/4 inch deep. What do I do now? Drilled next to it but can't get that sucker out. I should have gone to the trouble to get out the good bits but it's only aluminum. Damn chyna junk.

[hermosabeach]

Well it is a serialized Lower... right?

I seem to recall Feds don/t allow others to help with home builds...

Is there room to mill around the broken bit? Is it broken off flush?

Pictures?

What type of Mill?

Can you flip the piece 180 Degrees- Mill down to the broken bit from the other side and punch out

https://oag.ca.gov/system/files/attachments/press-docs/consumer-alert.pdf

[ar15barrels]

1/8 inch bit broke off while milling an 80.
About 1/2 inch of the bit broke off about 3/4 inch deep.
What do I do now?
Drilled next to it but can't get that sucker out.

A drill bit?
A router bit?
A screwdreiver bit?

Without specifics, there's no way to say the easy way to attack the problem.
An EDM will plunge straight down into it no matter what bit it was but it's probably cheaper to just buy another lower and try again.
Maybe use some and clear the chips better next time so you don't stick another piece of tool steel in your aluminum blanks.

[bohoki]

a pic would help why a 1/8 bit?

[Lonestargrizzly]

That sucks!
Hope you bought a 3 pack!

[ar15barrels]

a pic would help why a 1/8 bit?

Probably one of these kinds of jigs that uses a whole bunch of drilled holes to remove most of the material:



You drill the small holes, then drill the bigger holes and then finally use a router to finish the pockets.

[calwoodbutcher]

A drill bit?
A router bit?
A screwdreiver bit?

Without specifics, there's no way to say the easy way to attack the problem.
An EDM will plunge straight down into it no matter what bit it was but it's probably cheaper to just buy another lower and try again.
Maybe use some and clear the chips better next time so you don't stick another piece of tool steel in your aluminum blanks.

Drill bit. Yes it is serialized and logo engraved as well. Ain't gonna trash it. I was using aluminum cutting fluid and clearing chips (apparently not enough). I am thinking of cutting away the material around it with an end mill after drilling the closest 3/8 holes.

[ar15barrels]

Drill bit. Yes it is serialized and logo engraved as well. Ain't gonna trash it. I was using aluminum cutting fluid and clearing chips (apparently not enough). I am thinking of cutting away the material around it with an end mill after drilling the closest 3/8 holes.

If you clear all the material around it until you are within 0.010" or so (don't run another drill bit or the endmill into the broken drill bit!), you can take a punch to the drill bit and break open the cavity that the drill bit is in and knock it out to the side.
Make sure you get ALL of the remaining pieces of bit out before you mill through that section because a piece of drill bit will trash an endmill.

[calwoodbutcher]

Thanks Randall. I will take my time. Haste most assuredly got me in this mess.

[bergmen]

There used to be an acid etch product that will only attack steel and leave the aluminum alone. I used to use this when I was in manufacturing to remove broken thread forming screws and broke taps. It will remove any finish you have (in my case black anodizing) but the broken part will eventually float out.

I would check with machine tool outfits (call around, you will find someone who knows exactly what I am taking about).

Dan

[calwoodbutcher]

Managed to drift that junk o bit out with a punch. Came out in pieces but it is all gone. Thanks again Randall.

[sonofeugene]

What are you using to mill the lower? A proper milling machine, I hope. Though I kind of doubt it because you broke a drill bit.

Why people don't use a proper tool for the job boggles my mind.

[pacrat]

What are you using to mill the lower? A proper milling machine, I hope. Though I kind of doubt it because you broke a drill bit.

Why people don't use a proper tool for the job boggles my mind.

If someone is using a fixture like that shown by Randall. A drill press, or even a properly used hand drill. In conjunction with a router is "a proper tool for the job".

A "proper milling machine" is certainly no guarantee of undamaged tooling.

[calwoodbutcher]

Thanks Pacrat. Not all of us can afford "a proper milling machine". Lowers done with the jig method function perfectly fine. Ask the thousands of people that have used them. Done here for now.

[xsefan]

Mini mill works great for a bunch of stuff. 80% arms ez 3 is half the price of a mini mill. Drilling and taping an 870 is the reason I bought the mini mill. Now I use it for all kids of stuff. I have even done some non gun stuff for people and made some money back