Depending on the end of the tap, either a regular pointed taper or a reversed point, ie has a center hole to receive the end of the tap, and basically turn the work and hold the tap with a wrench. Just like turning between centers. A bit difficult to do, need two hands if you'll not have a spring center.
That is the cheapest.
I have a spring loaded layout punch I mount in the tailstock. Depending where your located, they are dirt cheap, about
5 bucks at places like harbour feight. They are the spring loaded type that you just push the tip on your layout mark, and when it gets to the end of the travel, it clicks, and makes a punch mark. Great for quick punch marks for drilling, or use as a spring loaded guide for your taps.
Then comes those times when the tap you have, doesnt have the drilled dimple for the spring loaded device. This is when you need one of those tap holders that have the ferral to tighten the tap into it, and the other end has the little round stock handle. Most are allready drilled on the centre of the handle end, and the spring loaded device fits in perfect.
Those are allso available dirt cheap to.
Even if the handle end isnt drilled, just chuck it you lathe, and take a centre drill and put your own dimple in it. Many tap sets come with these as well as the standard handle.
You dont need any thing fancy , or expensive, just the spring loaded punch, and a few sizes of the tap handles. The type with the ferral to tighten the tap. Then regardless if the tap wil take the sping loaded point, or not, you have a way to get them started and get it straight.
As a matter of fact, I had to use both items tonight, the 1/4-20 tap had not been drilled to take the point.
I should have taken a pic while it was setup, it would have made it more clear.
One other way you could do it with out any extra tooling in a pinch, is remove the chuck from the tailstock, and put the tailstock barell up against your tap handle. It will help keep things straight, provided your tap handle is flat on that side.
You can roughen the shank of the tap by rolling it gently against a bench grinder and it will grip enough but slip before it breaks. Just make sure it stays round and consistent. Or if you're really good, grind three flats @ 120°.
I just use a standard drill chuck -- just for the reason you pointed out, the the tap will slip when it meets the bottom of the hole, or when the resistance gets to much (taps are hard and wont mar like a drill bit). I do have variable speed and this is done very slow. At the first slip, I reverse and will usually try again and get a thread or two more, if needed then I finish the threads with conventional means by hand. (use lots of thread cutting oil!)
Here is a few pics for you. I am assuming your just trying to get you tap started straight.
These tap holders are roughly under 10 bucks each, the spring loaded punch is also under 10 bucks. Hardly worth the effort to make one. For large taps, I use a my 3 jaw 3 inch chuck, I can get a pretty good grip with that.
The one pic just shows different ends on the taps. Not all will take the point directly, and the reason I use the tap holder with T-handles to get them started. Once your in a few turns, put what ever handle you want on.
There is also special chucks meant for holding taps on the square end, but I dont have one. But if your tapping under power, then thats another deal all together.
Nice job you did on your spring loaded tap holder. Thats a real nice looking piece of work.
Tapping under power is ok to do. I wouldnt recommend doing it till you get used to tapping with out power. Someone on this site made a slick tap handle/holder, it looked like a good plan for under power tapping. In the design, it the tap got tight it would slip. Atleast I think it was here. If anyone remembers the thread, point us to it.
Pontiac, if your wanting to tap under power, you can still do it using a typical handle, with lots of care I might add. I do it on my machine. I rest the handle on a wood way cover that locks over the ways. The other thing you will need, is a good spring loaded setup like Jimbob has made. The big problem with tapping under power is if things get to tight, then come the sound, Snap: and there goes the whole job. Your best to start and finish by hand. Unless you have a run of the same parts to tap.
When I use a drill chuck in the tailstock for tapping, I turn the spindle by hand. I'm just interested in getting the tap started straight. After there are a few threads cut, I remove the tap from the chuck and then use the regular tap handle to run the tap to depth.
By doing it all by hand power, you are able to back up regularly to break the chip. Every now and then, remove the tap to clear the chips.
There's nothing wrong with power tapping in a lathe, but you have to know what you are doing. The tap must be sharp, the tap drill size must be correct and the tap must be gripped in the chuck tight enough to feed but not so tight that it breaks. If you are just starting out, it would be best to hand feed it with one of the centering devices already described. I really like the tool posted by Steve and can definitely see one of them in my tool box in the near future. :thumbzup:
Thanks Tom. Before I made that tool I also chucked taps in the tail stock. People don't seem to realize how dangerous power tapping with a T handle can be. Even at seemingly slow speeds if the tap sticks, that other handle is getting accelerated instantly just like the one jerked out of your hand. I have done it on mine but they have a belt clutch I could feather, it still scared me as when it was running good I'd get carried away and getting whacked would be like getting hit with a tire iron.
Personally I do not consider it safe to hold anything by hand that could rotate with the chuck I wouldn't touch if it was spinning with the chuck.
Nice job on the tool. Thats probably a safer way to do any tapping under power. I like the idea of just letting it go if the tap sticks. The tool you have built still allows the operater input to how much force it takes to hold the wheel. Very cool design work, and with safety in mind.
Ok, everybody that has contributed, Thank You! I got the machining part of mine done, just need to get the spring for the inside. I think it will work, not the prettiest but not as bad as I could have done. Once again, thanks everybody! You guys make it so much easier with your quick responses and pictures.
Don't we all have a stock of varying sizes of music wire in 36" lengths, I've got from .025 to .093, about 8 different sizes, (propeller shafts for rubber band airplanes) That make wondrous springs. Then I've got a spool of .009 for really tiny springs.
Tell me what size you want, diameter of wire, outside diameter and number of turns, I'll see what I can do.
Collis or collus make taper shanks that hold taps and drills. I've used and own them they work well , I would tend to watch using them in a gear head lathe unless your use to doing it. I've never broken one power tapping with my lathe or even my mill . I have broken them trying to Jack them around by hand on a lathe. I've always wanted to build one like the one Swatson built figured it would work for very small taps.