What kind of tap set???

[rkcarguy]

There is 1 HSS tap set at horrible freight that is a good set...

This photo isn't real clear, but they all look to be plug hand taps, which are not suitable for power-tapping. Caveat emptor! You only get what you pay for.

The set I got contained 2-flute spiral tip taps up to 1/4", then the bigger ones are 3 and 4-flute plug style which I agree you don't want to power tap with. They aren't all the same types of taps which is strange usually the whole set is of one type. I've used the smaller ones a lot and haven't had issues. The main reason I bought it was I needed a pipe size tap and die for an emergency fix on a boat manifold drain and the taps in the kit ended up being pretty good for $40. Per my above post, I subsidized the kit with high quality taps for the larger sizes that I power tap with often, like 5/16, 3/8, and 1/2 NC and NF.

[Harold_V]

The set I got contained 2-flute spiral tip taps up to 1/4", then the bigger ones are 3 and 4-flute plug style which I agree you don't want to power tap with.

The number of flutes does not dictate if a tap can be power driven or not. Larger taps intended to be power driven are often made with more than two flutes. What determines if a tap can be power driven is the grind at the cutting edge, or the nature of the flutes. Hand taps, which are generally multi-fluted, have flutes that are parallel to the shank, and do NOT direct the chip in any particular direction. As a result, it builds in the proximity of the cut and will load a flute to the point of binding the tap in the hole if it is not reversed to break the chip on a regular basis. For that reason, straight flute taps that don't steer the chip should not be used for power tapping, the exception being for thin materials, where the tap reaches through the part before the flutes can load to the point of binding the tap.

By sharp contrast, spiral point taps (gun taps), even those with more than two flutes, have an angular grind at the point of the cut, which drives the generated chip forward. This type of grind, like the grind of a spiral flute tap, provides for evacuation of the chip from the flute, so taps of those designs lend themselves to power tapping.

H

[Steggy]

Also I found that a beat up tap that I got from who knows where, cut a LOT better than the shiny new cheapo tap.

Back in the days when high fidelity, stereo amplifiers were powered by vacuum tubes (and some still are, for reasons that usually become clear when you hear one through high-end speakers), a common bit of advice was to pick up the amp you were contemplating purchasing. If it was heavy and you had to strain to lift it, then buy it. The reason was the high quality ones had a lot of copper and iron in their transformers, which had a marked effect on sonic qualities, especially at the bass end.

Now, I'm sure you're wondering what a stereo amp has to do with cutting metal. Just as a high-quality amp has a subtle feature that is a clue to its quality, taps can similarly tip you off to their quality. If a tap is uncoated steel (which almost all of my taps are) and the shank looks to have been polished it's likely that tap was subjected to high precision grinding after heat treatment, which is a finishing step omitted with cheap taps. You will also see that the flanks of the threads themselves appear to have been polished. A tap made that way cuts very accurately and produces smooth, well-shaped threads, even in tough materials (assuming proper lubricant is used).

Some "off-shore" taps are cut to shape and size and then heat treated, with no post-heat treat processing to assure the thread form is what it should be. The tap may be subjected to pickling to strip the oxides left from heat treatment, which will make the tap look shiny, but don't be fooled. These are the taps that cut raggedy threads, require a lot of torque, and easily break.

As always, you never get more than your money's worth.

[Harold_V]

Weight for quality amplifiers is not limited to tube type gear. McIntosh has built amplifiers with more than ample copper and iron since its inception. I have owned four of their amplifiers, starting with one of their tube types. The current amplifier tips the scales at approximately 130 pounds, and it's solid state. It's rated @ 400 watts/channel, which it can produce with .0005% distortion. Their tube type amplifiers were never rated as well, due to the difficulty of producing non-distorted sound with tubes. Granted, that is likely not discernable by ear, at least for most folks. They were heads and shoulders better than the majority of other makers, as they still are today.

No, I am not a stock holder. I just appreciate the fine quality they produce.

Having owned both types of amplifiers, and listening over exceptional quality speakers, I am of the opinion that one is not able to discern a difference between solid state and tube type equipment. A blind test would most likely prove the point.

I welcome your thoughts, and apologize for the hi-jack (of which I approve).

Yep! Good taps are ground with thread grinders. However, quality taps of days gone by, that was not the case. Most taps were machined and then heat treated. It was not uncommon to sharpen them after heat treat by grinding the faces of the flutes. They performed less than adequately, however. Grinding is a critical step in producing high quality, and allows for a miniscule taper towards the shank, which reduces friction of the tap in the hole. Needless to say, the pristine thread form permits a far better result.

H

[SteveM]

I have one set of metric taps, an offshore set I picked up at an estate sale.

I tried tapping a hole and it was incredibly difficult, even though I wasn't trying to go with full thread depth. The tap was squeaking and I felt almost no cutting action.

I stopped because I feared that the tap was going to break.

I removed the tap and almost dropped it, it was so hot (and this was HAND tapping). My guess is that the threads behind the cutting edge were not properly relieved and that was rubbing on the threads.

Steve

[Bill Shields]

what..you say that there needs to be relief????

shhh....don't tell anyboy

[tornitore45]

Tap relief, sure they cut in one direction, can't be started from the shank. I read somewhere that dies do not need relief because one can reverse then and cut with the back to go up to a shoulder, also the relief may trap chips when reversed.
Any truth to that?

[Harold_V]

Relief in dies is achieved much the same way it is achieved in twist drills. Exposed area is reduced. That's what the holes are for (aside from being the place chips can accumulate), and, yes, it's true that you can reverse a die to limit the amount of lead presented. With a little care, a thread can be created to a shoulder, although thinning the die may be required. It should be noted that the holes allow for a die to be sharpened, although I suspect precious few are. Note, too, that the hole creates rake, just as the flute does in a tap.

While twist drills are ground with a taper, reducing size towards the shank, being circular ground (the sides of a drill are not backed off with a primary angle, as they are not intended to be a cutting surface), the surface area of the margin is reduced, so a limited amount of the margin contacts the generated hole. That lowers friction of the drill in a hole.

H

[mcanaedi]

On the side of buying what you need, in my project I am wanting to thread 1/2 in. diameter 306 stainless rod. I am learning as I go here. Have a big shelf project to hang from ceiling. Also have 3/4 inch SS plate to make square nuts. For nuts I am gathering that I need a 29/64 drill bit with the belief that I should do 13 TPI. Not sure about sticking with 60 degree pitch or going acme (30)? but in any event trying to figure out where to buy the tap and die for this project knowing it has to be the best and harden steel for SS. Any suggestions appreciated. If this is not the right place to post understand this is my first post. Plug, TIN, NC, HSS, 302...certainly the most indepth topic of my whole project!

[Bill Shields]

you do not want to know the cost of acme tap / die set.

for 306 any HSS set will work as long as you are careful and lubricate as you go.

is there some specific reason why you do not think a standard 60 degree thread will not be strong enough....or is this something that is going to be 'in motion'?

[mcanaedi]

Bill over at Regal mentioned acme so I had to question it. I do see that TiNC is best. Oxide used. It is just 4 drops hanging from ceiling hold the board in suspense with plate and nut for shelf. Heavy but not in motion. One last question, do I use UNC 2B or UNC 3B thread type? I understand that to be medium tolerance on threads vs. low tolerance tighter fit on 3B. The threads are what is holding this heavy board? Suggestions?

[B Mann]

Just an amateur myself... So my questions may be off... I think an acme thread is for a something movable. Like the thread used on a C clamp. Or hooked to a motor to move a threaded part back and forth. So I do not believe that is something you need.

As far as a heavy shelf, what do you think is heavy? 50 lbs, 500 lbs or more?? Would you use stainless threaded rod?? or are you going to try to thread a 1/2" rod yourself? That will be a lot of work. I think standard nuts or threaded steel like you are talking should be more than strong enough. Depending on how heavy vs the strength of the support rod.