I have been using the 6-48 tap & drill set that Steve Earle used to sell but the tapered tap snapped off in a piece of brass.  They are no longer listed on his site, so I am sourcing some elsewhere.  I have read pros and cons of high carbon steel vs HSS.  Is the ability to shatter a broken off tap the best way to go.  One comment on a machinist board said a HSS tap in a custom tap holder that uses a set screw holding the round shaft of the tap is best as the shaft will turn before it breaks.  

Your thoughts?

I have had no issues doing barrel holes but had read that you don't need fluid with brass.  Prior to snapping this 6-48 tap, the only brass I have done is 10-32 or 1/4-28 with no fluid and no problems.  I just read that a good cutting fluid for brass is bacon grease.  Next time I will have a BLT before cutting brass threads.

Jack,
Lard or bacon grease is a good medium for tapping brass, just a dab will do.  A dark sulfur base works as well, mixed with white lead, it works even better...

A practice a mentor of mine back in my early days of machining use to do - partway between the flutes and the square drive he would use the corner of the grinding wheel and hand grind a "v" at that point, making it slightly smaller in diameter than the distance across the bottom of the flutes.  He said that would be the point the tap would break if he pushed it too hard or used it when it became dull.  I have used that idea a few times and it does work, it breaks with enough sticking out it can be grabbed again.  I don't seem to remember to grind it until it's too late, but sometimes I look close at the tap before I use it too many times and give it a toss.

I too get the majority of my taps off eBay, the HSS taps are my  first choice, they stay sharp a lot longer.

GT

There's brass and then there is brass!  Some brass, bronze?, like bearing brass is really hard to machine and is worse than steel.

Just ordered a few from Amazon. I like the HHS, seems to hold up better on hard stuff. I drill out broken taps with carbide

bpjack wrote on Feb 3^rd, 2025 at 11:21am:


I'm sure you had the right sized drilled hole for the tap. Right? #31 or .138" drill bit.

In my working days I tapped a lot of # 3 4 and 6 dia holes and have used just about every tap manufacturer out there and every lube I could find. Even with the best of conditions taps will eventually fatigue and break. You never know when they will let go. Hopefully when they do you can get the remnants out.


JMH

wesg wrote on Feb 3^rd, 2025 at 8:04pm:

For the most part I second the statements above. Buy good quality taps, learn which tap type to use for which job, and they do wear out so if you are doing a critical job (and IMO all tapping is critical) buy new taps, they aren't that expensive but fixing a broken tap issue is. If I had to scale worst to best I would say 4-40 is at the bottom and gets better as the taps get both bigger and smaller. A 2-56 is easier then a 4-40 as well a 6-32 is easier. That has been my experience over the years.