what is a starting tap and a finishing tap

Den 08-06-2013 00:18, Jude007 skrev:

Here you can see a picture of different taps:

Finishing taps are needed for blind holes. Pipe threads are almost never used in blind holes. Although a pipe thread in a manifold might not have enough space for tap clearance.

Anyhow, McM-C doesn't have NPT finishing taps, so they must be pretty uncommon, if they exist at all.

Maybe your customer is pulling your leg. Or maybe you're pulling ours.

Bob

In a German hobby store I saw a set of very small, delicate taps that enlarged the threads sequentially in IIRC three steps. I believe US practice is to use a tap with a long taper instead. jsw

...

They exist albeit are relatively unusual...

Far too little information to satisfy -- you can begin to get the picture of the questions needed to be answered if browse here

Taper pipe taps aren't the same as machine screw taps. Machine screw taps come in taper, plug(or second) and bottoming. Normal hardware store stocking is just the taper, rarely bottoming. You have to get to an industrial supply house for the other two. Usually taper taps are fine for through holes, it's only when you've got a blind or shallow AND blind hole that you need the others. A taper tap can be ground to be either of the other two when needed. Just buy extras.

As far as pipe taps, for most plumbing, the standard one that most retailers carry is usually fine. Have never needed more than just the one type.

Stan

-Taper pipe taps aren't the same as machine screw taps. Machine screw

-taps come in taper, plug(or second) and bottoming. Normal hardware

-store stocking is just the taper, rarely bottoming. ...

-Stan

Make that "plug" for the hardware stores.

If you want a LONG taper on a straight-thread tap, look for a "nut" tap.

"Pulley" taps look similar but have plug-length cutting edges and standard diameter shanks. That's obvious if you see them, but maybe not in a catalog.

There are also untapered pipe taps, for hydraulic Straight-O-Ring (STOR) fittings, some electrical conduit, and electric water heater element threads. jsw