A question on milling over a broken HSS tap in 1018

I have a question on what would be the best approach to face mill over a 1018 steel part that has a broken HSS tap in it. The part is .7" wide.
I am making a drilling jig and broke a HSS 1/4"-20 hand tap in the top. See photo attached.
I would to take the top of this part down another 1/2" and that would require taking the imbedded broken tap down as well since it is thoroughly imbedded.
If I use an old 1/2" HSS end mill to do this, would it work or would I completely trash the endmill? I have an old 1/2" endmill that I would use. Surface just needs to be flat but not precision like the rest of the part.
I also have a Tormach center cut insert end mill I could use but don't want to trash my good inserts unless they would survive the operation.
Any thoughts would be appreciated.
Thanks!

A HSS tap will destroy any other HSS tool. A carbide tool will cut through it, though it may get damaged some in the process. I've used carbide endmills to drill out broken taps.

Regards,
Ray L.

I drilled out a 10-32 tap recently with a smaller carbide spotting drill, everything needs to be very rigid, I did it in the old Bridgeport with the table locked down and fed the spindle down by hand.
It has to be fed slowly.I used a vacuum to keep the hole cleaned out as the debris can chip or break the carbide drill.

Trying to machine over a broken tap will trash a HSS endmill, carbide would be better but you may chip it if the tap moves in the cutting process, broken taps have never been an easy task for me period!

I saw one removed perfectly with an EDM sinker using a copper tube as the anode! I would have never believed it except I was standing there as the guy did it!

Been there, got the t-shirt:) Luckily I have someone with a sparker close by for my get-out-of-jail-free card on anything critical.
However, when I can't get access to this I have a selection of small used carbide end mills - around 3mm/4mm/5mm - which I will use to mill the tap out with by light vertical plunging.

Whatever you do don't even think about trying to cut through with another HSS tool, or even approaching side-on with carbide - careful plunging is the only way to go.

And on a final note, don't forget that taps are consumables and get blunt as well, and IMHO this is usually when and why they break like that. Seen too many old taps break off because people forget about this. Always keep a spare and when you feel it getting tight then it's probably time to change it.

Thanks for all the posts
Sounds like surgically removing the old tap with a carbide tool before milling down is the way to go
Thanks

Attachment 253434

As others have mentioned a carbide end mill would do the job.

You should also be able to break the tap up a bit more. Try a few well placed blows with a center punch and hammer. You might not get all of it out but you should be able to remove a few more chips. If you get really lucky you might get the tap turning.

Here is a simple DIY edm: https://pico-systems.com/edm.html. The usual electrical safety precautions apply...

bob

Quote:

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Originally Posted by newman55598

Attachment 253434

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That is fine for a steel tap in aluminum but not so great for a steel tap in steel...

bob

I use an old ball end mill, i your case use a 3/16 write a drill program g73 and have Q at .002 or .003 and i use air on it. then i pick out all the left over pieces the best i can with a pick, then i chase the tread with an old tap working it slowly because there are chucks of the old tap in the threads

center punch and a hammer, hand taps are normally 4 flute that small and bust up easy,,, mill a little bust a little , repeat.

The tap looks like it has flutes. You might try a Walton tap extractor. Remove Broken Taps with Walton Tap Extractors

Don Clement

You could mill around it then grind or surface grind off the nub.

Quote:

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Originally Posted by rowbare

That is fine for a steel tap in aluminum but not so great for a steel tap in steel...

bob

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Sorry missed the line with the 1018 steel.

mill around it then try and remove it.
hss em well that will die quickly carbide good chance it will chip.

Any progress on the broken tap removal??

Thanks for everyone's invaluable advice.
I learned quite a few good strategies
I didn't have a carbide tool I wanted to sacrifice so I did a work-around and was able to attach to the side of the block instead of on top.
Thanks again for all the input

That's one of the biggest advantages of being the part designer as well as the machinist - screwups just need a few minutes in CAD to resolve the problem.