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What sizes do you find you use most often when fixing instruments?

arpthark wrote: ↑Thu Nov 30, 2023 9:04 am What sizes do you find you use most often when fixing instruments?

For me: 3x0.5 in metric, and 4-40 in U.S. Customary.

I'm sure that stop-arm screws vary all over the map, and I generally have no need for tapping stem threads on pistons so I don't recall what those threads are (and they vary by manufacturer, too).

Rick "just to get the replies started" Denney

more and more: metric

Including that stupid less-common M4 X .75 that Yamaha uses...

But I would recommend having on hand 2.5, 3, 4, and 5 in the standard TPI.

You likely already know that the most common SAE taps will be 8-32, 1/4-20, and 5/16-24. You'll need smaller ones if you're messing with woodwinds, and obviously these aren't the only ones needed for brass.

I don't find much use for the two or three SAE thread sizes other than 8-32 which are used on American valve stems, because when the threads break off of a finger button, it's pretty much scrap brass, and when one breaks off in a stem, it's either extracted and the female stem threads are still good, or the stem is thrown in the trash and replaced.

You should also have a dye for each of these thread sizes listed above.

I don't think you'll ever have any of these though, because - knowing you - you're probably going to wait until you can get each of them for a dollar or fifty cents.

I'm sure you know - or at least suspect - that I have quite a few more taps and dies than the ones listed above.

Since we are on the subject, I have never had any trouble tapping decent interior threads, but using dies to create make threads is much more difficult.

Is that normal, am I the only one? Does thread pitch matter? I seem to recall the last time I tried, I had more success with one pitch than the other for a m4, But I cant remember more than that

LeMark wrote: ↑Thu Nov 30, 2023 2:27 pm Since we are on the subject, I have never had any trouble tapping decent interior threads, but using dies to create make threads is much more difficult.

Is that normal, am I the only one? Does thread pitch matter? I seem to recall the last time I tried, I had more success with one pitch than the other for a m4, But I cant remember more than that

I find that cheap dies are really difficult to use, and that trying to cut threads with no oil with cheap dyes is really difficult. You are also supposed to cut threads on material that is exactly the right diameter, and not force a die over something that's even a little bit too large. I've been guilty of using cheap dyes, not stopping to oil, and forcing dyes over things that are too large in diameter, so you can march me to the gallows along with everyone else.

I was using a m7 die on a m7 rod, but I wasn't using oil.

Another thing is getting them started nice and straight, but you probably did that too. A seven is pretty big, and it's a size that - when done by hand - can tend to get manhandled and might tend to go crooked and then straight and then crooked and then straight.

If you can think of something wrong way to do something, I've probably done it or I probably will do it.

How much and what kind of oil depends on the material. Gooey metals like stainless steel are the worst. I usually use Anchor Lube, because it’s a paste that doesn’t run off. It’s better on stainless than Tap Magic, which I use for iron and regular steel. Aluminum is gooey but soft, and even WD40 works fine. Brass is easiest of all, and I use Tap Magic if anything.

Most cheap dies are intended for thread chasing more than thread cutting. Good dies are expensive, and I buy the only when I need that size as a result.

For large sizes, a die really needs to be mounted in a machine to hold it straight. I have a die holder for the tailstock of my lathe. I don’t use the lathe to power the die, just to hold the material straight while I turn the handles.

I also have a spring-loaded center to keep taps centered using a drill press or the lathe.

But nothing on a tuba I’d anywhere near that big.