I've gotta do a dozen little parts with 2, 2-56 holes and 2, 0-80 holes in each of them. I have not had good luck with tapping titanium in the past. Also, I would usually be inclined to do it by hand, but with taps that small, I'm thinking with the right tap it may actually be safer to do it in the machine. Anyone have any recommendations? I do not care at all to set the world on fire with speed, just wanna get through it without breaking taps in the holes. Material is Ti-6Al-4V solution treated and aged. Thanks in advanced.
Roll Tap and Moly-D and mfg's speeds
I've always used cut taps in titanium that were specifically designed for titanium. I like Emuge, Prototyp, OSG, and Greenfield. Rigid tapping M3 holes with a spiral flute bottom tap + moly-dee works well, if I am using a hole size to give a 65% thread. I've tried various tapping fluids and I like moly-dee the best. One place I worked used Accu-lube and I remember that that also worked. I use form taps all the time but have never tried them in titanium. Balax recommends machine screw & miniature form taps in materials up to RC35.
If you can, once you start tapping don't backup or stop until you have full thread. Use proper titanium tap like jcoehlo mention. Good luck.
I wouldn't even think about using a form tap in Ti. In my experience with Ti, the one thing it doesn't seem to like is stuff "rubbing" against it. What has worked for me in the past is grinding (by hand) relief behind the cutting edges of the tap flutes, this minimizes the amount of tap flute rubbing against the Ti. Your doing some pretty small holes though so I don't know if this method will work for you. Spending the money on quality Ti specific taps may be the way to go for your situation.
Originally Posted by jcoehlo
+2 on what these guys have said, if you can, Rigid Tap with attention to Surface Speed, ask whoever you're sourcing the Taps from about the Surface Speeds.
Originally Posted by Dustcanblue
+1 for Titanium specific taps and MolyDee
Give me your depth of each thread, class of fit and whether they're through holes or blind holes. I'll run the Prototyp CCS software and see what tools and running parameters it comes up with. Also let me know if you've got rigid tapping, and if so do you use a flexing tap chuck?
No mystery here.
Basic failure mode analysis. You cannot rub ti.. but you can cut it easily. So why is the tap failing? Because it's rubbing the material.
How do you keep from rubbing the material? Use a tap with high hook and radial relief.
Check out the hook on these taps. Guess which one works great on cast. Right. Not the high hook version. Abrasive material would wear down the hook really fast. But the high hook works great on ti because it shaves the material.
Now, let's consider the other important factor: relief behind the cutting edge.
Remember how everyone preaches to you about using positive rake tooling on ti? Don't you think that basic premise would apply to any cutting tool in a ti application..? Yep. So apply it to tap geometry. Get some relief behind the cutting edge so the tap doesn't rub. Ti has a low modulus of elasticity. That means it closes down on the tap behind the cutting edge, causing the snatching, binding, and popping noise that we all hate.
Remember.. there are two basic modes of tool failure. Mechanical and heat related. Mechanical can be broken down into two subsets: abrasive wear, and abrupt catastrophic failure such as breakage from an interrupted cut.
Heat is always and everywhere the killer.. and ti is the textbook example.
The only acceptable mode of failure is abrasive wear at a predictive rate.
Get an application specific tap for titanium. It will have the proper hook and relief.
Use a tap with as much lead as possible. 3-5 will work.
Keep the sfm below 70.
Use a decent tap compound. Moly-D is just fine. Coolant sucks. (Notice it doesn't say "tap compound" anywhere on the barrel.)
If you want to rub something find a vase. Call me if Barbara Eden shows up.
Thanks for the smarts Curtis. Much appreciated.
Way to put it into words we can all understand.
Here's a good article with illustrations similar to what Curtis just posted. It has a sidebar that describes the flexor-equipped holders that I recommend using for very small or very high-speed taps.
All of the above and run the max allowable minor diameter for the thread class and don't use 4 fluters.
Once I started using Balax form taps in Ti, most of my problems went away. While I don't doubt what others have said, the Balax form taps have worked GREAT for me when rigid tapping in a VMC. I've used 0-80, 1.0 UNM, and 1.2 UNM so far.
Emuge has both form and cut taps designed/recommended for Ti. Anyone used the Emuge form taps?
I've found this OSG technical link to be helpful:
OSG Tap & Die, Inc.
I ended up using Emuge taps. Just called them up and said "This is what I'm doing, what should I use?" Anyway, machine-tapped about 40 0-80 holes and 80 2-56 holes and never broke a tap. I was quite happy, even if the suckers are $45 a pop! What have you, small price to pay rather than snapping off taps in a part every other hole...
Originally Posted by claya
Originally Posted by StreetSpeed
How deep were you going?
Crap I don't remember. I wanna say .180" blind with the 0-80 and .300" thru with the 2-56.
Did you go with form or cut taps?
Originally Posted by StreetSpeed
I don't even know. Whatever the tech rep at Emuge told me to use. Sorry I'm a shmuck for not knowing the answer to that.