Two broken taps

autonoz

autonoz

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Well I am making a ball turning jig, using Steve Bedair's design. Everything was finished except for the carbide insert holder. Drill a #43 hole and used a 4-40 tap. Two times I have tried and two times I have broke the tap inside the hole. Now I have to make a whole to holder and still hope I can tap the hole. I am putting the tap in my mini mill with a drill chuck and turning it by hand, backing it out regularly, keeping it lubricated, but it snaps without warning. Irwin taps, so they are decent. Any suggestions?
 
What material is the insert holder made from and what are you using for lube? On small taps I only start them a few threads with a drill chuck and then use a tap handle so I can get a better feel of how much torque I'm applying.
 
Old Machinist has a good point, and would go that route. Myself, I havnt had much luck with that brand of tap, and suggest trying a different brand. Ive had Irwin taps snap like that without warning when tapping 1/4 x20 holes. Is your job a blind, or through hole? If blind, maybe back out more often, and use the shop vac to clean the chips out. Maybe try a different cutting oil, though I feel your pain. I think we all have been in this very spot before.
 
Many times I will drill the next size bigger drill, you might only get 55% instead of 60% thread depth. I have also had better luck using bee's wax on those hard materials then tapping fluid.
 
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IRWIN taps are decent???? They are not anymore. Better buy a better brand. And,stop holding the tap in your milling chuck. You cannot feel the torque very well. That's 1 reason you're breaking those taps,which are junk to begin with. Use a hand held tap holder.
 
Sometimes (not always) you can salvage the piece by making a paste of baking soda and water and slopping it into the hole. Keep it damp as possible and warm in the toaster oven about 150-175 degrees. That's well below annealing temperature so no worries there. Let it sit for 4, 5, 6 hours then chip at it with a punch. Most of the time the remaining tap will crumble into pieces.

Are you sure you used the right bit and didn't grab the wrong one? Maybe mic that thing and double check.


Ray
 
I don't remember the brand of oil I am using, I put it in a squirt bottle a while ago. I will get a better tap since the consensus is Irwins are bad and it is in 1018. I do have a tap handle, I just thought using the mill would be more precise, but I see your point on feeling the torque on the tap. Thanks for the input and hopefully I can get this thing done.
 
On threads that small, I only hand tap.

If you use a mill, cut no more than 2-3 threads to aid alignment.

The rest by hand.
 
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