You can use cutting oil for aluminum if tapping aluminum. The taps that don't have flutes are not ground round. They are ground to have high spots. If you grast the tap lightly and turn it you can feel the eccentricity. A good hardware store will sell tapping fluid. The clear works well for aluminum. For steel the dark sulfurized stuff is good. You do know that hole size is critical for form taps? The hole will of course be larger than for a cutting tap, but the size has less tolerance than that for a cutting tap because the material is displaced rather than cut. Eric
If you are "free" hand tapping, that is without a tapping machine or using the drill spindle, it is very helpful to fabricate a tap block which can be as simple as a piece of scrap metal with a hole the OD of the tap drilled perpendicular in it to insure the tap is straight when it starts. Quickly pays for itself with avoidance of broken taps and scrap parts. Much less time to fabricate than remove a busted tap from a part.
Store bought ones generally sized for cut not rolled thds
For a fancier one see
If you are using the drill spindle/chuck see
high priced spread :-)
What I bought -- works a treat on both lathe, drill press, and mill
First item: It is critical that you use a tap wrench to minimize side loading and breaking the tap. Never use a crescent wrench, vise grips, etc.
I never disconnect the quill spring, the quill clamp should be adequate. There are several different ways to tap in the drill press or mill.
First is to simply chuck the tap in the drill chuck and start the tap one or two turns, loosen the chuck and retract, and use a tap wrench to finish tapping. The problem here is the tap shank is hard and the drill chuck will tend to slip. This is compounded because when you grasp the drill chuck to turn it, you tend to open it. Some people make a pin or hook wrench to fit into the tightening holes for the chuck key (which the higher quality Albrecht type chucks don't have). While this is a good expedient for smaller taps and occasional use, the guided tap wrench is a much better option as it minimizes any side loading on the tap, and insures the tap remains perpendicular. This can be difficult when tapping into a curved or slanted surface, for example mounting a scope. (it can be helpful to lightly machine a counter bore into the workpiece with a flat bottomed drill or end mill to make the surface flat) In use a guide rod which fits closely into the tap wrench is clamped in the drill chuck, and the tap is clamped on the flats in the tap wrench. The tap wrench rotates/slides freely on the guide rod.
As mentioned I bought both sizes of the WTTOOL tap guide and these have worked well for me. I don't know if the ones currently sold are the same but they look like it.
Another type is a spring loaded guide that centers the tap. Almost all taps have either a center or a cone on the end which will fit into the guide, and most of the fancier t-handle tap wrenches* have a center hole in line with the tap axis. Many of these guides have a reversible pin with a point on one end and a center on the other. These are used to start the tap straight, and are driven with a regular tap wrench.
One additional use I have found for these guides is with a length of 3/16 drill rod with a center [regular 60 degree seems to work as good as a bell center] in one end and a sharp point on the other for use as a pump staff [with a drop indicator] to accurately locate work on the lathe face plate from layout prick [not center] punch marks.
The items shown are only examples and the other mill supply houses should carry.
A tap block can be even simpler. I have just used a short piece of 2 by 4. Just drill a hole thru it using the same drill you used to drill the hole that you are tapping. Run the tap thru it. If you get it started crooked , it will be fairly obvious. In that case drill another hole and try again . Or drill a hole slightly bigger and try that. And when you are done you can toss the bit of 2 by 4 and not worry about finding it the next time yo u have to tap a holo.
Well ... *I* don't -- but I use a TapMatic tapping head, which reverses the tap and speeds it up when withdrawing from the tapped hole.
I suspect that varies with the design of the drill press.
Mine has a flat spring wound up and connected to a notch in the end of the shaft for the feed handles. The other end engages a groove in a cup which is clamped to the side of the drill press. You adjust the tension to balance the weight of the qulll plus the chuck (or the tapping head) and add a little more lift for convenience -- and ideally never touch that adjustment again.
I've not followed the URLs to see what was being described. You might need to back off the tension if you were using it like the so-called "tapping machines" where it guides the tap in vertically, but you provide the turning of the tap with a crank on the upper end.
Aye, that's the same way mine is set up as well. I've read of fellows talking about disconnecting the spring for tapping, but never really figured out how exactly to go about doing it; it would probably be enough to just back off the tension so the quill didn't retract, but I don't know if the spring mechanism is really set up to be continually adjusted like that.
I don't know about using that tool above, but for taps clamped in the chuck or collet, no, you don't remove the spring. It helps the tap to back itself out cleanly. Just leave your hand on the ball as it taps, providing an equalizing pressure to overcome the spring tension, then remove it (I hover) for the backout. Piece o' cake.
I would never disconnect the spring, it's not going to provide any positive benefit even when tapping and it's also very annoying having to unlock the quill with one hand while having to also simultaniously use the other hand just to keep the tool from suddenly dropping down into your work.
I suppose if a person had three hands then if might not be quite as bad.
"PrecisionmachinisT" wrote in message news:HPWdnYy4cbr10c_PnZ2dnUVZ firstname.lastname@example.org...
I drill and tap on a Clausing mill that lacks a return spring, which trades one set of annoyances for another. Having the tool slam onto the work is considerably worse than having it rise when released. I replaced the plastic ball on the quill feed lever with a brass one heavy enough to counterbalance the chuck, and tighten the quill lock just enough that a drill bit has to be pushed through the bottom of the work. Mine is the early model with one hex bolt for the quill lock.
Ball-bearing Jacobs chucks usually grip taps well enough to start them straight in the hole before switching to a tee handle. Resting the chuck jaws on the cone at the end of the tap gives some indication if it wobbles. I suppose I could hang a weight on the quill feed to make the chuck jaws push and center the tap while I turn the tee handle with equal pressure from both hands. A few times I've loosened the chuck so it only guides and started the tap with a wrench on the upper end of the flutes. This area can be ground flat a little to give the wrench a better grip. I don't grind past the thread roots to avoid weakening the tap.
The first taps arrived yesterday. They were some ebay special Brubaker HSS
10-32 H4 ones with a fairly shiny finish.
The test was pieces of 6061 and something else that was much softer and gummier.
As with any tap chart, the more you look, the more answers you get for the nominal drill to use.
The charts from a few makers seemed to suggest someting close to #17 drill for about 75% thread, so that's what I used.
It worked fine. I used the wax stick for a bandsaw as lube and each and every time the taps went straight into the aluminum with no problems. I used a small tapping block for some holes, and did the rest with a lathe to hold the tap straight. I did notice they started easier than cutting taps and didn't try to wander on the first cut.
I didn't measure torque, but they felt much smoother than any cutting taps I've used, even the good ones. No crunchines, no sticking, no need to back out all the time. Backing out still required a wrench, but not much effort. I did some bottom-out tests and it was easier to feel the bottom of a hole with the roll tap.
The thread quality is clearly better too, fasteners go in smoother and there's no fuss with cleaning crud out of the threads when you're done.
The one thing the databooks warn about is how the threads will make a volcano shape if you thread straight into a flat surface. I actually noticed the 6061 would split and flake more than in would make a nice protrusion.
Countersinking before threading just resulted in the protrustion to occur out of the way. Countersinking after threading solved this and gave the prettiest results.
The 1/4-20 tap should arrive in the next few days. I'll try some brass and steel with both next.
So far, two thumbs up. these things are pretty cool.
Though the brass will be easy to tap the results may not be so good. When half hard free machining brass (the most common) is formed by the tap it may flake. Tiny flakes may come off of the threads. You will be able to see them easily with a magnifier. And the threads may be weaker that cut threads. Gummy materials work the best for form tapping, so mild steel and 5000 series aluminum work well. I have form tapped many 10-32 holes in 304 SS, even though the torque required was kinda scary. Eric
Assuming the load and cosmetics are important..and in many cases its not...yes indeed....form taps are much much better than cut taps for non ferrous materials. Well put.
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you were right about the brass. The threads were pretty flakey and the pieces I tested actually deformed quite a bit. The volcano shape around the threads exceeded the diameter of the threads for the 10-32 thread in a piece about 3/16" thick.
I tapped around an existing 1/2" hole and this hole which was about 1/4" away actually changed shapes and no long press fit the mating part.
I guess the lesson is, just cut brass threads, which is no problem since they're strong enough anyways.