[KEENANDOG1]

BEST WAY TO MILL OUT BROKEN TAP. I HAVE BEEN USING G73 WITH Q.002 WITH K.006 AT 6000 RPM AND A FEED OF 1.0. WAS WONDERING IF HELIXING WOULD BE BETTER OR DIFFERNT SPEEDS AND FEEDS IN MY G73. ON A BRIDGEPORT I RUN RPM AS FAST AS I CAN, PUT SOME TENSION ON THE QUIL LOCK AND G73 BY HAND WITH NO COOLANT AND A CARBIDE END MILL. BUT HAVE BEEN STRUGGLING ON MY HASS MILL BURNING UP MORE CARBIDE END MILLS TO GET THE JOB DONE. MAYBE I SHOULD TRY IT DRY WITH AIR LIKE ON THE BRIDGPORT. ANY SUGGESTION WOULD BE APPRECIATED....

[pakman]

This may sound a little rough and tough but has never failed for me hundreds of times if you have a stuck tap under 3/8 use a 1/16th larger nut 1/8th over on 1/2in dia and above. Place the nut over the hole the tap is stuck in it dose not matter if it is 1/8th below the surface then use a mig welder pointing the wire as close to centre and parallel to the tap and pull the trigger Welder setting is easy on a scrape piece of plate try to fill the nut in 2 to 3 go"s with out melting the nuts six sides you will need a fairly hi heat setting and a low wire speed It can take 3 to 4 tries the first try usually the shattered end is removed ,the 2nd removes the contaminants ,Oil Tapping compound, ect 3rd/4th time out she comes keeping in mind to work the nut mounted tap back and forth in 1/24 turns until loose I could explain the dynamics and why the nut dose not weld to the housing but who cares it works but be advised that this has only a 70% success rate when the housing is aluminium ! on other metals Brass Steel copper A V8 cummins crank shaft where the harmonic balancer is fitted while still mounted in the truck BE Brave

[txcncman]

Quit breaking taps.

Mill it out by hand so you can "feel" it.

Or, just keep doing what you are doing. Costing yourself time and money.

[KEENANDOG1]

thanks for the suggestions, the only bridgeport was being used and it wasnt my broken tap. it was a customer that brought it in with a tap broken in a threaded insert in a special aluminum die. also everyone in the shop brings their broken tap parts to me to fix them. this morning i changed my Q to .oo1 my K to .003 and my feed to .7 and it worked perfect the first time without ruining the origanal threads for the insert. replaced the insert and was good as new with out scaring the part at all. might just be lucky but it worked...

[txcncman]

Cha ching! Since it was a customer, you were making money.

[daedalus0x1a4]

if you have access to a small edm machine you can burn through the shank of the tap and then shatter the rest.

most of the time i will take an endmill that is close to the minor diameter of the thread and use a bridgeport to plunge the mill in to the tap. i will use a carbide drill if i can because the tip will chip before the tool fails completely.

using an nc machine is not the way i prefer to remove taps but if you must i would center an endmill or drill on the hole and use a simple drill cycle (g81). try around 120 SFM for a carbide endmill, 40 SFM for a carbide drill, and 60 SFM for a HSS endmill; run through it .0008" - .0015" per revolution especially with a drill because it takes pressure to cut material as hard as treated tool steel.

i advise against using coolant unless it is through-tool and recommend air to clear the chips from the tap because if they enter the cut they will damage the tool.

some people will try to tell you that you can put vise grips or channel locks and twist the tap out of the hole but i havent met success using that method.

sometimes you can take a punch and shatter what is left of the tap after you put a smaller diameter hole in it without effecting the hole much.

but my favorite way is to use a left handed drill because once it starts to catch on the tap it usually twists right out of the hole. if the hole is through you can stick a right handed drill through the back of the hole to have the same effect.

[SumDumPhuckr]

These have worked for me!

http://www2.coromant.sandvik.com/cor...1/main_e_7.pdf

SDP