2/56 tapping frustrations

K

Kali4nia

Joined
Aug 12, 2015
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I make folding knives and have always struggled with tapping titanium. I just broke 3 off in parts... Im trying to go .216 deep. Ive drilled 5/64 and #47 with no luck. It seems to work until the tap gets to the bottom of the through holes. I have used thread form taps as well as traditional taps (osg and others).

Ive been using slp 2000 for lube, bad idea? I have a cnc machine but no reverse on the spinal. The single point thread taps ive found aren't deep enough. Any advice to help me in this struggle. I can't keep trashing titanium.
 
Do you have a copy of the Machinery's Handbook? If not, get one.

For tapping titanium, the tap should have a 5 to 10 degree rake angle. Also, make sure any coating DOES NOT have titanium in the mix (TiAlN, TiN, AlTiN, etc...). It will bond to the titanium you're tapping and cause it to drag & gall. CrN and ZrN are safe, but very hard to find. A plain (uncoated) HSS tap will be the best option here. Avoid HSS and tungsten carbide grades containing cobalt, as that also readily bonds to Ti (M42, M35, etc..).

The 5/64'' (0.0781'') and #47 (0.0785) are both within the range for a 60 to 65% thread, which sounds right. You could also use a 2.0mm drill; every little bit counts.

Are you hand tapping with a guided fixture, or doing it on the CNC? That's a really long thread length for such a small tap. Binding chips in the flutes certainly aren't helping (and may be your primary reason for failure). Do you NEED that thread length, or could you counterbore 0.060'' or so, so you don't have to tap as far?

Is your lube the gun lubricant? If so, ditch that & use an oil made specifically for tapping. Hopefully some of this helps!
 
SLP 2000 might be better than nothing (maybe), but it is NOT a cutting/tapping fluid. Get a small bottle of MolyDee. It'll likely last you for 20 years. Is there a reason the threads need to be so deep? If it's a through hole and you have access to the back side, open up the back 50-75% of the hole to just at or under the OD of the 2-56 screw. Also, if you don't have a tapping fixture, it's probably worth the investment.

You might also try a light chamfer on the back side of your through holes. It might help slightly with chip evac/forming the very end of the thread where your taps are breaking.

Honestly, I think just using a proper tap fluid will make a noticeable difference.
 
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View attachment 1199091 There is a chart in the Machinery Handbook that gives tap drill diameter recommendations based on the depth of the hole to be tapped relative to its diameter. Longer threads use fatter drills.
I use a hand tapper and frequently reverse the tap to break up chips. On deep holes I will sometimes back the tap all the way out and clean it before proceeding.
Tap Magic is almost as good as Sulfurated oil (as a lubricant) and is much cleaner.
Broken taps can be removed from Titanium with battery acid. There are probably stronger and faster etchants, but I have not used them.
 
Yeah I think you're gonna have trouble no matter what in that thick of titanium... But good advise by Sam
 
Wow you are all awesome. I do it by hand with no guide:eek:. No machinery handbook but drill trap charts from mcmaster. Slp2000 is my gun lube lol. I make thick folders and have been considering cutting a channel through the backspacer and leave enough meat to thread. I will update this thread with progress and the obligatory picture. :thumbsup:
 
If you looked up your tapping storybook problem in the handbook, it would say that a tap drill for a #2X56TPI thread with a thread length of 1 1/2 to 3X the thread diameter (.086”) would have a range of .0699”-.0737” for a Class 1 or 2 fit. These ranges are generated by equations that conform to the theory of proper thread height. They have little to do with actual available tooling. This is the problem with tap drill charts.
So you have to look for drills that get close to the theoretical sizes. There are 2 common drill sizes that drop in that range: a #50 drill at .0700” and a #49 drill .0730”. If you are breaking drills in holes that are oversized according to the theory, you may need to change your methods or enjoy a loose fit.
 
If you have a CNC you might try thread milling it. And a 256 is damn tiny but if it's not deep you have good success drilling it, following it with an end Mill and circular interpolate a square bottom hole to size and then threadmill that little thing. I've done this in titanium with good results

Single point thread mill, not a full form
 
I also have a hand tapping fixture as shown above and it works very well at keeping things square so the tap doesn’t snap. If you don’t want to use battery acid and want to save your piece of Ti, I’ve used my ferric chloride to get broken hss drill bits and taps out. Stuff doesn’t bother the Ti and eats away at the hss. Good luck, hope you find a solution that works for you.

Jeremy
 
Kali4nia said:
Wow you are all awesome. I do it by hand with no guide:eek:. No machinery handbook but drill trap charts from mcmaster. Slp2000 is my gun lube lol. I make thick folders and have been considering cutting a channel through the backspacer and leave enough meat to thread. I will update this thread with progress and the obligatory picture. :thumbsup:
Click to expand...
Doing that thin thread by hand :) I can bet that you will break that tap if you used it to make thread in butter :D You already get good advice here .... :thumbsup:
 
Get a tapmatic. Seriously.

It's one of the tools that if it broke today, I'd buy another one before tomorrow morning.

I've always tapped holes by hand and am pretty good at it but when I tried the tapmatic, it was a whole different world. I can tap 25+ holes with the tapmatic in the time it takes me to do one by hand.

It saves taps too. I have yet to break one with the tapmatic. And everybody who's broken a tap knows what a nightmare it can be.

They can be pricey but if you've got a CNC then you're no stranger to expensive tooling.

Try it. You'll thank me later.
 
07Vette said:
Get a tapmatic. Seriously.

It's one of the tools that if it broke today, I'd buy another one before tomorrow morning.

I've always tapped holes by hand and am pretty good at it but when I tried the tapmatic, it was a whole different world. I can tap 25+ holes with the tapmatic in the time it takes me to do one by hand.

It saves taps too. I have yet to break one with the tapmatic. And everybody who's broken a tap knows what a nightmare it can be.

They can be pricey but if you've got a CNC then you're no stranger to expensive tooling.

Try it. You'll thank me later.
Click to expand...


Even the chinese knockoff of the tapmatic is great
 
I got a great condition used tapmatic on ebay for like $85 lol, just gotta keep an eye out!
 
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