Tapping 4al6V Titanium?

flatgrinder

flatgrinder

Joined
Dec 20, 2005
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I have a piece of titanium that needs to be tapped for a 4-40 machine screw thread, what size hole should I use?

I checked out this chart: http://www.shender4.com/thread_chart.htm

It has two separate categories, one for "Alum, Brass, & Plastics" -the other for "Stainless Steel, Steels & Iron" -what is 4al6V more similar to?

Thanks! :thumbup:
 
The larger the diameter of your tap drill, the shorter your female threads will be. The notion that material determines tap drill size is strange to me. My charts peg tap drill size to hole depth. The shorter the hole, the higher the female threads. For a class IB fit in a tapped hole (the depth of which) is between 0&1/3 of the screw diameter, the tap drill should be between .0849" & .0894". For 1/3-2/3 screw diameter the values are .0871" & .0916". For 2/3-1 1/2 D the numbers are .0894"-.0939". For holes running 1 1/2 - 3 times as deep as the screw diameter, the tap drill diameter should be between .0902" and .0947". These numbers are derived from equations. Whether you can get an exact drill size match is another question. For case one I would use a #44 or a #43 drill. For case two I would use a # 43. For case number three I would use a #42 or 3/32" drill. For case number four I would use a 3/32" drill.
 
tiguy7 said:
The notion that material determines tap drill size is strange to me.
Click to expand...
Nothing strange about it.
Different materials behave differently, and have different strength characteristics.
This allows for different thread percentage requirements.
Ti likes to shrink and bind, and is very strong when properly tapped.

You can get away with a 50 - 60% thread depth in Ti, but not Aluminum, or plastic.
So different requirements for different applications.

Personally for size 6 and below, I only roll tap titanium.
It's easier, a more reliable process, and seems to make stronger threads.

In my shop, I would drill 2.55mm or #38 in a deep hole and then run a thread forming tap.
 
Fellhoelter said:
Personally for size 6 and below, I only roll tap titanium.
Click to expand...

Never heard of roll tapping. Is it just a matter of the taps used and is it as easy as cut tapping for the beginner (bad) machinists like me? Not that tapping is ever easy for me but you know what I mean.
 
Google thread forming taps to learn about them.

I find it much easier to tap using them, as they are substantially stronger, and break way less...
 
Rollform taps rock for titanium! They are a bit more expensive but last way way longer and are really fast and easy to use.

The biggest thing to keep in mind though is that they need a higher tolerance hole to work right. And it's not the same hole size you'd use with a cutting tap.

Lube is a little more important with roll taps too. Use a grease or oil made for high pressure for best results.
 
I really like thread forming taps, they are a lot stronger, and because they don't create chips they eliminate one of the main causes of tap breakage (binding on chips). There is no need to peck. They last forever. But, like Jason just said, the hole diameter is different (.100" for 4-40) and the tolerance on the hole is a lot more important, .0995 gives you 73%, .1015 gives you 61%. That's a pretty big swing for only a couple thou, so cheap tooling and marginal processes can easily cause a lot of trouble.

I'll usually thread mill when I can, but deep holes = taps. Tapping on my machining center has been hit and miss, but I haven't broken a tap since switching everything over to OSG thread forming taps. I remember the first time taping 1-72 in 304 about 3/8" deep, 63% thread, this was just a couple months ago. The head on this mill weighs over 700 pounds and there is a 15 HP motor that has to stop and reverse. All this really heavy stuff all going down to this teeny tiny little tap that you literally can't even see once it's in the machine. I bought three of them figuring I'd bust them in the learning curve. I'm still on the first one, so I'm really pleased.
 
Thanks for all the replies everyone! :)

I was informed that the best way to go would be to use thread forming taps and a Tapmatic 30X tapper. Thanks Chuck! :thumbup:
 
I also appreciate the additional info.
I have to ask. Why is it that it's the first time I heard of them if they are so much better than sturdier than cutting taps (or whatever the regular ones are called)? I mean, I am no expert, but I've read a few posts about taps and don't remember anyone suggesting switching to these. :confused:
 
Nathan the Machinist said:
I remember the first time taping 1-72 in 304 about 3/8" deep, 63% thread, this was just a couple months ago. The head on this mill weighs over 700 pounds and there is a 15 HP motor that has to stop and reverse. All this really heavy stuff all going down to this teeny tiny little tap that you literally can't even see once it's in the machine. I bought three of them figuring I'd bust them in the learning curve. I'm still on the first one, so I'm really pleased.
Click to expand...

Now THAT'S impressive. I was kind of squirming in my chair envisioning that process. Tapping TI usually makes me apprehensive, I'm going to have to check out the threadforming taps. Boy, a Tapmatic would sure be awesome, too...
 
Salem, last night in chat, Jason (Belstain) gave me the drill sizes he uses:

"<Belstain> Patrice, I just checked and I use a .0550 for 0-80 and .0781 for 2-56 rollform taps."

Let us know how it turns out if yo try them.

PS: Salem, you should drop by on Wednesday nights by the way. :D
 
Thanks for the sizes, Patrice.

I've tried Wednesday chat, my connection is too slow. I'll drop in and say hi whenever I figure out high speed internet on this mountain. And no, satellite ain't gonna cut it.
 
Salem, it's weird cause pff (Pat) who is the chat grand poopa is on dial up and it works. I'll ask him if he knows why. Do you access chat through the Java thingy or a standalone app like XChat. That's what I use on Linux (Ubuntu). Did away with Window$ a few years ago and couldn't be happier.

*Sorry for the thread hijack but Salem's PM inbox is full. :(
 
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