View Full Version : tapping

11-21-2004, 07:05 PM
What am I doing wrong? I keep breaking off the tap 2-56 in brass using tap Magic in a piece of brass that is 3/8 inch thick. I am new to all of this. I backed out and cleared threads I think a suitable amount. I was almost through...Any suggestions would be appreciated. I love the group! Thanks Fred

11-21-2004, 07:13 PM
That seems to be a deep hole for a 2x56 tap. Are you using a gun type type? This type of tap pushes the chips ahead of the tap. I have tapped a lot of 2x56 holes but never 3/8" deep. Are you using good quality taps? I use the wax type tap sticks for lube and have not broken a tap in a long time. (knock on wood) One thing to make sure of is that you are tapping dead straight, any side motion will snap the tap almost instantly.

Paul in NE Ohio

11-21-2004, 07:18 PM
I think you may be work hardening the piece . try a new dead sharp drill , lots of coolant, gentle pecking . And does the tap lube say it is for brass? perhaps lard or alcohol might work better.unless time - motion eficiency is a major deal I like to drill undersize and then to size with stock sensitive to work hardening from heat of drilling

11-21-2004, 07:23 PM
Try tapping in the mill or drill press to keep the tap aligned. You might want to stop and back out about half way to clear chips and every other turn after that. Thats what I do when I have to tap a blind hole with a small tap.

11-21-2004, 07:29 PM
As said in other post make sure that you are going in straight. On very small taps after a few complete turns I will back the tap out all the way to clear the chips. Haven't broken a tap in a long time. Takes more time but is faster than trying to remove a broken tap.


11-21-2004, 07:32 PM
Bras can be tricky.
If I dont need super strenght I drill the hole larger, which is what I would do in your case.
Here's the rule for strenght.

Lenght = 3 times the diameter.

After this the bolt will most likely break before the hole stips. With your 2/56 you can go to 50% or less and have no porblems.

Also remember that a tapped hole will only lose about 5% strenght with a 75% thread coverage.

[This message has been edited by RobDee (edited 11-21-2004).]

[This message has been edited by RobDee (edited 11-21-2004).]

Don Clement
11-21-2004, 08:17 PM
I have just been tapping a hundred 2-56 holes in SS and aluminum to a depth of 0.15” Although not quite the 3/8” depth, there were no broken taps. A suggestion to tapping 2-56 to 3/8” depth in brass would be to use a forming tap that produces no chips. See: http://www.balax.com/forming.html

Don Clement
Running Springs, California

11-21-2004, 08:32 PM
Check the actual diameter of your tap drill. Measure it with a micrometer just above the flutes.
Don't just trust the drill number.
The actual diameter of numbered drills can vary all over the place.

From a free chart I received from LitteMachineShop at the Cabin Fever Expo:

2-56 tap for 75% threads use Drill #50 = 0.070"
2-56 tap for 50% threads use Drill #49 = 0.073"

At the 2-56 size a couple of thousandths can make a big difference.
When in doubt go with a slightly larger drill.

[This message has been edited by fixxit (edited 11-21-2004).]

11-21-2004, 09:35 PM
Yep, if the strength is not required, go up a drill size.

11-22-2004, 06:23 AM
Thanks guys, alot of information in those posts. I guess I violated about all the rules. Any clues on how to salvage the piece? It sure doesn't want to drill out. Thanks to all for the great advice! For a hobby this sure is frustrating! Thanks Fred

11-22-2004, 08:33 AM
Brass needs a SHARP!!! tap. I've found if the tap is dull at all (or not a really high-quality tap), brass will tend to spring back, rather than cut, and end up binding the tap. You can get away with a less-than-perfect tap on shallow holes, but it catches up with you on deep holes.

The suggestion to use a slightly larger tap drill for a hole that deep is excellent.

Don Clement
11-22-2004, 10:58 AM
Walton tap removal tool may have a tap extractor for a 2-56 see: http://www.waltontools.com/ For forming taps with no flutes and small taps (where there is no extractor tool) Alum (aluminum ammonium sulfate) works for dissolving steel taps stuck in aluminum. I don’t know if Alum works with a tap in brass.

Don Clement
Running Springs, California

11-22-2004, 11:15 AM
On removal: if things get desperate, and the piece allows it, you can make a hollow end mill style of cutter out of drill rod and cut out a plug that includes the busted tap. Then, depending on the situation, either Loctite or silver solder (or maybe soft solder) in a replacement plug that you can then proceed to re-drill and tap.

11-22-2004, 01:03 PM
If I can get away with it on through holes I just pound out the old tap with a punch and redrill to the next large screw size.

11-22-2004, 05:09 PM
Thanks a million! I managed to drill out the broken tap with a bit in a dental high speed turbine drill. I am sure the demensions of the hole have been altered a bit by now. I will take all suggestions and try again. Thanks for all the help and Happy Thanksgiving to all, a great group!

11-23-2004, 12:41 AM
Fred,i often tap 3mm,which is not much bigger than 2-56.Are you using a T-handle tap wrench?they seem to break small taps real easy.
I use a good quality pin vise,turn 1/2,back out1/4,etc.alternatively,it's quite easy to make a holder for a specific tap quickly.alum.rod,drill for tap,cross drill 1/8 from end,tap for setscrew,presto.i have several of these for delicate jobs.That size taps are a bit expensive to break often http://bbs.homeshopmachinist.net//frown.gif.regards,hans.

11-23-2004, 06:00 AM
Yes, That's what I use on small taps too. Pin vises work very well. 'T' wrenches aren't sensitive enough for small taps.
For larger taps over (6-32) I have a trick that works well. What I do is chuck the tap in a portable drill and set the drill to slip at the lowest setting. What happens is the chuck slips and 'hammers' the tap lightly as it's slipping. If the tap stops I turn up the clutch a step higher but use your common sense and make sureto keep the drill straight in the hole.
I'm working on a stepper tapper that will work off a microprocessor but that's a ways away!

11-23-2004, 06:22 AM
Great ideas, thanks Fred

Gary Helmick
11-23-2004, 08:14 AM
I just borke a tap in a piece of aluminum, (got in to big a hurry).

I remembered a thread on this site about broken taps I did a search on the site and got a good hit.

What the thread said was to use alum (you can get it at a grocery store in the spice section)in hot water to remove broken taps in brass and aluminum. Don said the same thing in the above response

As I am writing this, I am cooking my aluminum in a glass bowl and the tap is being eatin away.

Hope you never break another tap again, but if you stay in this game I have a feeling you will, so maybe this tip might help you in the future.

Gary Helmick

[This message has been edited by Gary Helmick (edited 11-23-2004).]

11-23-2004, 10:42 AM
One last thing I didn't see here, Do you nee threads all the way through?

Consider drilling a clearance counter-bore on the back side - maybe half the thickness - then you only have to tap 3/16" deep. assumeing a through hole.

Same could be done on front face if circumstances allow (mating part covers hole, ect.).

May not apply to this project, but something to think about,

If it were me, I'd remember this one after about 2 more broken taps! http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif

That's why I luv this board, When I get "Go Fever", ther is usually someone to remind me --If you butt itches, perhaps you should wipe BEFORE you pull your pants up!! http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif


11-23-2004, 07:27 PM
Exactly what I figure I will do! Thanks, I only need a flush face on one side and the otherone can be countersunk and it will work out Perfectly. Thanks for the help

11-24-2004, 12:54 PM

Are you using a plug or taper tap?....

I was trying to tap 6-32 through 1/2 HR steel and found it close to impossible using a plug tap.....I then purchased some good quality TAPER gun-type taps, and the problem went away due to the smaller cut each tooth was taking.....