[Halfnutz]

Where can I get a CHEAP as $%^# thread milling tool?

Can I take a tap ( with the same pitch) and grind off 3 of the flutes and use it?

How about a boring bar for internal threads? What insert would cut a 2mm pitch?

I need to cut a lathe backing plate with a 1.5in x 12tpi thread.

The price of these little 1/8in. thread mills kills me, there like a hundred bucks or more. There has got to be a less expensive way to do this.

[kawazuki]

Not saying it can't be done but i'm guessing thread milling needs a) a very accurate speed control allied with axis positioning control and b) sufficient rigidity for the forces on a single point tool.
What is stopping you grinding your own tool from HSS or tool steel for the task - that would be suitable for use with a boring head. With regard the lathe backing plate, it would be usual to bore it
and thread it, on the lathe for which it is intended to ensure concentricity.

[dazp1976]

For a one off I'd keep my eye out for a hand tap that size on ebay. Mill the fitment hole and tap it by hand.
The X2 is crap imho.

[fc60]

Greetings,

I thread mill with a Widia Carbide Threading bar. Just look up the min bore size in the catalog.

https://www.widia.com/us/en/products...100007813.html

Yes, it takes a few minutes to mill a thread with one insert; but, it can be done.

The tap will not work as it has a helix and will cut an imperfect thread.

[metalmayhem]

a threading bar will do the job , I've used them for internal and external threads . Some inserts need some back clearance ground into them , otherwise they can drag and create a nasty burr
For that size of a thread I'd probably just use a double angle mill

[Halfnutz]

I'd love to find a 1.5 in 12TPI tap, but I have an X2 that is quite capable of milling it, and doing a very nice job of it too. Plus, once I get the process down, I can stop buying taps of that size. I have a huge assortment of smaller taps, Its just difficult to have all of them. Thread milling is a great way to handle the larger size threads with unusual pitches and diameters.

[Halfnutz]

a threading bar will do the job , I've used them for internal and external threads . Some inserts need some back clearance ground into them , otherwise they can drag and create a nasty burr
For that size of a thread I'd probably just use a double angle mill

Thats the direction I'm heading, a boring bar that I can put different size inserts in, for different pitches. I'm not sure of what you mean by a double angle mill, guess you mean a single form, yeah, a double angle thread mill. I did buy a form tool with the correct pitch and 9 teeth, and then I finally found a reasonably priced single form (double angle?) thread mill that can cut 12-48 TPI, at least thats what they claim. It was around 35 dollars. Some of them are so expensive, I looked at several that were only 1/8 in shanks and 2-3 inches long for 150 dollars and up. I couldnt see spending that much on something that I could possibly snap off in an instant. The one I got has a 3/8 in. shank and a much healthier .251 in. neck.

[Halfnutz]

Not saying it can't be done but i'm guessing thread milling needs a) a very accurate speed control allied with axis positioning control and b) sufficient rigidity for the forces on a single point tool.
What is stopping you grinding your own tool from HSS or tool steel for the task - that would be suitable for use with a boring head. With regard the lathe backing plate, it would be usual to bore it
and thread it, on the lathe for which it is intended to ensure concentricity.

Yes for sure I will bore it out on a lathe.

[metalmayhem]

double angle mills come in various angles and sizes
https://www.harveytool.com/products/...-shank-cutters
https://www.maritool.com/p2419/Doubl...duct_info.html

hand tapping a 1.5" thread sucks

[mactec54]

Where can I get a CHEAP as $%^# thread milling tool?

Can I take a tap ( with the same pitch) and grind off 3 of the flutes and use it?

How about a boring bar for internal threads? What insert would cut a 2mm pitch?

I need to cut a lathe backing plate with a 1.5in x 12tpi thread.

The price of these little 1/8in. thread mills kills me, there like a hundred bucks or more. There has got to be a less expensive way to do this.

Yes you can use all those types of tools to make a thread mill, you should be able to find a thread mill for $40 or less here is a link, there are may like this you just have to look for the right cutter.

https://www.maritool.com/Cutting-Too...381/index.html

[mactec54]

Not saying it can't be done but i'm guessing thread milling needs a) a very accurate speed control allied with axis positioning control and b) sufficient rigidity for the forces on a single point tool.
What is stopping you grinding your own tool from HSS or tool steel for the task - that would be suitable for use with a boring head. With regard the lathe backing plate, it would be usual to bore it
and thread it, on the lathe for which it is intended to ensure concentricity.

Not for single point thread milling, spindle speed can be anything you cutter can use, and the feed is to suit the pitch no more is needed, you do not need accurate speed control.

Thread milling can be done even on a simple 3 axes Router, no special control is needed.

[mactec54]

Yes for sure I will bore it out on a lathe.

If you Bore it on the lathe, why not thread it on the lathe at the same time.

[mactec54]

double angle mills come in various angles and sizes
https://www.harveytool.com/products/...-shank-cutters
https://www.maritool.com/p2419/Doubl...duct_info.html

hand tapping a 1.5" thread sucks

The double angle mill will have a clearance problem to cut a thread like that.

[Halfnutz]

If you Bore it on the lathe, why not thread it on the lathe at the same time.

I could, the change gears are such a pain, and Im not very adept at lathe threading. I like thread milling because its so easy, but, wow, I am just in shock at the cost of tooling these days. I found a double angle at mari that will cut a 12TPI for $56.00, but I allready ordered one from rogue, the two guys in So. Oregon, for 38 bucks. Its really a little small for a 12TPI, but I think it will work OK. Im working towards a set of round boring bars, probably have to cut them down, and the ability to use different inserts for different pitches for large threads, which are the ones that are such a pain to tap or thread with a die. Like ball nuts, axle ends, etc. I do have a 15/16 x 16TPI tap for the Thompson 5/8" ballnuts which use to be the goto before the asians started selling metric ballscrews for so cheap, but man that M.F. is a real bruiser to use. I cant even imagine trying to cut a 1.5 inch 12TPI into steel by hand. Maybe cast iron, but I have a steel backplate. I'm getting too old for that. I do have a pipe threader that I could use if I could find the right inserts for it, but those cost a small fortune too, and there are very few available pitch inserts available for them, mainly just pipe standards, and they are all tapered threads. The nice thing about thread milling is the flexibility.

edit: I just remembered the pipe threader cuts outside threads, so it wouldn't help anyway.

[mactec54]

I could, the change gears are such a pain, and Im not very adept at lathe threading. I like thread milling because its so easy, but, wow, I am just in shock at the cost of tooling these days. I found a double angle at mari that will cut a 12TPI for $56.00, but I allready ordered one from rogue, the two guys in So. Oregon, for 38 bucks. Its really a little small for a 12TPI, but I think it will work OK. Im working towards a set of round boring bars, probably have to cut them down, and the ability to use different inserts for different pitches for large threads, which are the ones that are such a pain to tap or thread with a die. Like ball nuts, axle ends, etc. I do have a 15/16 x 16TPI tap for the Thompson 5/8" ballnuts which use to be the goto before the asians started selling metric ballscrews for so cheap, but man that M.F. is a real bruiser to use. I cant even imagine trying to cut a 1.5 inch 12TPI into steel by hand. Maybe cast iron, but I have a steel backplate. I'm getting too old for that. I do have a pipe threader that I could use if I could find the right inserts for it, but those cost a small fortune too, and there are very few available pitch inserts available for them, mainly just pipe standards, and they are all tapered threads. The nice thing about thread milling is the flexibility.

edit: I just remembered the pipe threader cuts outside threads, so it wouldn't help anyway.

A regular Boring Bar will not do threading by just changing the insert, you have to use a different Threading Bar for that.

[Halfnutz]

yes, I have found that out looking at them. I'm gonna try out one of these, some day, but not for this backing plate, and not right now.

https://www.ebay.com/itm/30420461934...Cclp%3A2047675

[CL_MotoTech]

Amazon has decent insert type tooling that come with a variety of tools, threading included. For the $90 I paid, it was well worth it. You couldn't pay me to grind HSS given the cost insert tooling these days.

[kawazuki]

Not for single point thread milling, spindle speed can be anything you cutter can use, and the feed is to suit the pitch no more is needed, you do not need accurate speed control.

Sorry - in my brain, that doesn't compute! Take a 10tpi pitch - for one revolution per minute, the feed (in or down) will be 1/10th" and two revolutions per minute, the feed will need to be double ie. 2/10th"? They are interconnected -
if one changes, the other must change to suit or the pitch will change. Setting the spindle speed at 100rpm and keeping the feed @ 1/10th" you'd end up with a 1000tpi pitch or so fine as not to be a thread at all. Surely this is true,
else why is the lathe toolpost on the cross slide locked to the spindle via drop down gears when threading?

[Halfnutz]

Amazon has decent insert type tooling that come with a variety of tools, threading included. For the $90 I paid, it was well worth it. You couldn't pay me to grind HSS given the cost insert tooling these days.

What did you get for the $90 from Amazon? I'm sorry if I missed something where you already told me or posted? Anyway, I got the multitoothe threadmill I ordered off ebay



Who knows when I'll get to trying it out on a blank piece of steel, Ive been working on a electronic leadscrew using just an Allen Bradley servo drive and motor(s). I think it was you that gave me the idea for it. I have so many of these servo drives and motors, and I think I can get it to work using just the two A-B 3000i servo drives, one for the leadscrew, and one for the spindle. I can pick up the position and rpm off the spindle drive and use it as the index for the leadscrew servo set up as a follower..

Too many motors, not enough time.....

[Halfnutz]

Kawazuki - Thread milling relies on the three axis, X,Y and Z interpolating the thread pitch and diameter of the helix. The cutter, usually a single thread profile, is fed into the helix, and it is assumed that the cutter will cut the entire thread on one pass. This is not a problem, because your spinning that cutter in the thread at 1500-3000 rpm and moving it along the helix as slowly as you want to. Normally, you don't have to run any more than one pass, but as long as you start the helix at the same exact X and Y co-ordinate, it should cut right back into the helix. The problem with thread milling, is that if you want to use a multi tooth form tool, you have to have different form tools for each pitch. Otherwise, if you use a single tooth double angle thread mill, you have to have one small enough to cut inside the diameter of the bore. For external threads, of course, this is not an issue. Otherwise, the problem is that you have to cut the entire helix with a single tooth three or four flute mill, and its very time consuming. Much too time consuming for production work. Using a multi tooth form mill can speed up the time, but there are other problems making sure you move fast enough to clear the chip load, and other issues. Its more complicated than I can fully grasp. That's why the toolmakers usually have their own software to figure out exactly how each of their mills will perform, what pitches and profiles they can cut, and they program the g-code for you. AS LONG as you buy their 175 dollar thread mill.

I'm being facetious really, as Mactec54 has pointed out, threadmills can be had for 30 dollars and up. The problem I have with them is they are so tiny, and I break things.