Topics include, Machine Tools & Tooling, Precision Measuring, Materials and their Properties, Electrical discussions related to machine tools, setups, fixtures and jigs and other general discussion related to amateur machining.
One question that I don't believe has been asked is, what number of tappings are required? Is this a production situation or just a "here and there" tapping typical of a home shop? There are plenty of ways to aid in tapping straight and true by hand.
My Autal tapper has been used for one job ,years ago. The job paid for the tapper with ample profit left over but it hasn't been used since.
I may never require it again but, being the hoarder that I am, it's still put away, at the ready.
Just went out to the brrrr cold! shop to make sure it's an Autal and there it was with it's MT2 shank! ooops!
Yeah, but not in a production format. More like prototyping.
I'd just pop a dead center in the drill chuck that I just used to drill the hole what needs tapped, use it to catch the dimple on a larger tap or the centering divot on any decent tap holder, and tap by hand right then and there, while I'm all lined up on the hole.
Don't think a tapping head thrives in a one-off or prototyping scenario.
Long Tom wrote:Don't think a tapping head thrives in a one-off or prototyping scenario.
That's precisely why my Procunier didn't get a lot of use. It's not worth the time it takes to make the setup unless you've a fair number of holes to tap. They really are a production tool, although they serve quite well for even a one-off, assuming you don't mind spending the time to set up the head.
I could generally drive a tap in and have it out (holding the tap in a drill chuck and reversing the spindle) before I could drop the knee of my mill far enough to install the tapping head (the negative aspect of having one equipped with an R8 tapered shank).
Harold
Wise people talk because they have something to say. Fools talk because they have to say something.
I also power tap with the mill, and I'm done faster than I could even get the tapping head out of the cabinet. I thought I was looking at a few hundred tapped holes once-upon-a-time and got all caught up in getting one from ebay. Didn't ever happen, but I did get a set of the smaller Ettco heads very cheap and they cover my needs should I ever need them. But as of the last (what?) 6 years or so, they were mounted once just to see they worked and never again...
BadDog wrote:I also power tap with the mill, and I'm done faster than I could even get the tapping head out of the cabinet.
Me too...
I bought a tapping head about three or four years ago as it looked like it might be a handy thing to have for the Bridgeport. I thought it might be good on the CNC mill as well.
Still have not used it.
Just went right to a floating tap holder on the CNC knee mill.
Glenn
Operating machines is perfectly safe......until you forget how dangerous it really is!
Speed is a function of your courage, reaction time and a few other things that don't readily come to mind.
Like most machining functions, speed is your friend. It has less to do with how fast you get the job done than it has to do with smooth and clean cutting of the tool in question.
For a through hole, I've been known to tap with a ¼-20 @ 500 rpm. Note that I have three phase power and can achieve instant reverse, which is a saving grace. Otherwise you have to be quick on the brake, assuming you have one. Smaller taps? Depends on the material, of course, but the faster, the better, as it's highly unlikely you'd ever approach a speed that was too fast for the tap in use, barring the idea that you'd be tapping hardened materials.
The nice feature of using a tapping head is that depth can be established very easily, so you don't risk bottoming a tap in a blind hole. Procunier, unlike some brands, does not have a dog clutch, but a friction clutch. The moment the quill hits a stop, the tap is idled, so you can tap to depth at high speeds and not have to worry about going too deep. While that's true of dog clutch types as well, you have to preset a stop reflecting the pull-off. Not a big issue, as you get used to what ever you use. Still, when the dust settles, the Procunier is the winner for me. YMMV.
It would not be unreasonable to drive a number sized tap @ 1,000 rpm, if that answers your question. Just make sure you pick a speed at which you can react when necessary.
Edit:
I should make mention that I often start the spindle, turn it off, then tap, allowing the momentum of the spindle to do the tapping. That works for shallow through holes quite nicely. For deep holes, not so well. Also, be careful if you choose to power tap, especially if you hold your tap in a drill chuck. They are notorious for not running true, plus it isn't beyond reason that if you have to go back in the hole that you could split the thread.
While I routinely tapped holes with a drill chuck (for tooling, never for product), it is not an acceptable practice if your threads are inspected, as they tend to tap oversized (due in part to the chuck runout), or they are often bell-mouthed. Tapping heads tend to have a floating spindle, so they'll allow the tap to follow the hole without wobble (winging), reducing the change of either condition.
Harold
Wise people talk because they have something to say. Fools talk because they have to say something.
