Threading toolholders

BTS12 at bottom of page

on >micro<

?ProductID=1968 Unka George (George McDuffee) ............................. I sincerely believe . . . banking establishments are more dangerous than standing armies, and that the principle of spending money to be paid by posterity, under the name of funding, is but swindling futurity on a large scale. Thomas Jefferson (1743?1826), U.S. president. Letter, 28 May 1816, to political philosopher and Senator John Taylor

Thanks. You always have some of the best posts in this group.

So...

tools most like what I wanted and cheaper than what I paid for my indexed version.

The other links had lots of good stuff about tools or threading but I didn't see anything about creating your own tools that work like the tools in the expresscuttingtools link. Did I miss something?

I said I already have a simple tool bit I ground to fit in a boring bar that will work in a 3/4 inch hole. It's the 3/4 down to maybe 1/4 inch hole that I don't know how to easily make a tool for. My inclination is to try to grind a tool like the expresscuttingtools out of a thicker HSS toolbit, but as I said, that seems really hard.

Thanks again for taking the time to post all those good links, but in a quick scan, I missed any info on how to grind or otherwise make your own inside threading tool for smaller diameters.

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Thanks for your kind words.

Yes, its a *LOT* of work, and a lot of practice/skill is required.

My advice is to use a tap (or series of taps taper/plug/bottoming) for the smaller holes. This will save you a huge of time and aggravation. Even on external threads, you are generally better off using a die, rather than trying to single-point, and the threads are generally much higher quality.

You will need what is called a "fishtail" or thread gauge to both accurately grind and to align the threading tool with the part. for example see:

that a seperate gage is required for each thread form, i.e.

60 degree V, 29 degree Acme, 30 degree Trapazoidal, 55 degree Whitworth, etc.

Considerable experience and patience is required to freehand grind a thread tool to a "line out" fit with this gage, especially in the smaller sizes, so a grinding jig or fixture is suggested. A carbide style grinder is ideal [with white wheels for steel] but a belt/disk sander with a little care and some shop-made jigs/fixtures will be more than adequate for your use. I like the zarconia (blue) belts. see:

You can get fine and very fine grit zarconia disks from the paint and body section of your local autostore that will let you put a mirror finish on your tools. I don't know how much better this helps them cut, but they sure look nice....

The smaller boring/threading bars take round rather than square tool bits, and some sort of holding fixture is a necessity to shape/sharpen the tool bit, and these are a PITA to align in the boring/threading bar.

As you lack the required experience and more importantly the necessary equipment to grind an internal threading tool from the solid, spend the 20$ or so and buy one.

Everything considered, if you are, or will be, doing an extensive amount of internal threading where the taps are not easily available, bite the bullet, buy the micro internal threading tools (and cry when you break one).

FWIW -- If you are using a spindle hand crank, there is no machining benefit to be gained from high speed [heat resistant] tool steel. High carbon steel, perhaps from a bit of broken file will work just as well. Indeed, while not widely appreciated, high carbon steel can be harder than HS steel, and can produce a better surface finish with a properly honed and finished tool. The downside is that it is much easier to overheat high carbon steel and "draw the temper" when grinding.

The key is not to get "hung up" on any one detail, but cut some metal!!! Unka George (George McDuffee) ............................. I sincerely believe . . . banking establishments are more dangerous than standing armies, and that the principle of spending money to be paid by posterity, under the name of funding, is but swindling futurity on a large scale. Thomas Jefferson (1743?1826), U.S. president. Letter, 28 May 1816, to political philosopher and Senator John Taylor

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30 degrees puts all of the cutting on the forward edge of the tool. In some cases a *SLIGHT* drag introduced by using 29 degrees will produce a better finish by burnishing the trailing flank and/or supporting the tool.

Some writers indicate that the last pass should be done using the cross slide rather than the top/compound slide to remove the [possible] steps in the trailing thread flank, although with a 29 degree angle this has not been a problem for me.

Unka George (George McDuffee) ............................. I sincerely believe . . . banking establishments are more dangerous than standing armies, and that the principle of spending money to be paid by posterity, under the name of funding, is but swindling futurity on a large scale. Thomas Jefferson (1743?1826), U.S. president. Letter, 28 May 1816, to political philosopher and Senator John Taylor

Thanks for the additional reply. I already have a fish gage and have made a couple tools for cutting outside threads. Seem to work ok.

It's one project that got me started on the inside threading of smaller holes. I have a gooseneck and I want to make a lamp holder for the end of it. It has a strange thread, 1.6 mm if I remember right, and somewhere around 3/8 in diameter.

A couple weeks ago I needed to thread a 1/4" hole with 32 tpi. I used a

10-32 tap clamped in the tool holder as a thread cutting tool (just cutting on one set of flutes). With light cuts it worked.

OK. See

The larger one was ground from a broken 3/8" dia HSS end mill. It will do inside threads in a .250 dia hole. The smaller one was an HSS

1/16" drill that I heated, bent, then ground. This particular bit is an internal clearance-groove cutter but the corresponding threading tool is very similar -- I didn't bother to dig thru the drawer to find it. These will work inside an .090" dia hole. I ground the little one with a Dremel while wearing binocular magnifiers.

Gee, I just use an old Craftsman bench grinder, a Dremel and a magnifier. My threads seem to work OK, often "feel" better than tapped threads.

Looks good, Don. Thanks for the ideas.