Thread: Make a 5/8"tap

I am also at the point I have to make an ACME tap... I was going to use 4140 to make it, it will harden to 50HRC...

Mine has to be similar to Mike's but instead of 5/8 has to be 0.6"...

Maybe he could make one for me when he is in the tap making mood...

Originally Posted by Stustoys

I'd think if you have some longish dowel pins or some ground rod you could make something in the spirit of Phils in less than a week. Turn the "spaces" to suit your dowel/rod. Mount the dowel/rod in the lathe chuck and the tool on the tool post(just like you were cutting the thread).
Am I missing something?

Stuart

Yes , that is a way to go . A bit of lateral thinking Thanks .. Mike

Originally Posted by .RC.

I am also at the point I have to make an ACME tap... I was going to use 4140 to make it, it will harden to 50HRC...

Mine has to be similar to Mike's but instead of 5/8 has to be 0.6"...

Maybe he could make one for me when he is in the tap making mood...

.6" is a rather odd diameter for a ACME thread ? What is it for RC

Make another

I thought it was better to rough the thread out first with a square tool, then cut the acme form? That way you can make the cutter undersize and leave the compound at 90deg and use it to bring the cut to the right width. Keep in mind i have never cut an acme thread......

Ew

Originally Posted by Ueee

I thought it was better to rough the thread out first with a square tool, then cut the acme form? That way you can make the cutter undersize and leave the compound at 90deg and use it to bring the cut to the right width. Keep in mind i have never cut an acme thread......

Ew

Ewan ,

That sounds a little esoteric BUT

That is what I did the first time I did a 8 TPI ACME thread on the lathe , making a leadscrew. After cutting the initial groove with a thin thread form to remove the bulk of the metal in the groove , I finished off with a ACME shape tool - I thought that ACME tool was the correct size, in that case a commercial insert . Turns out it was the wrong size insert - it was supposed to be a 8 tpi thread form insert , as sold on fleabay , but what it was, was actually a 6 tpi insert

So I now have a 8TPI ACME leadscrew with a 6 TPI threadform ... for the junk bin .

Originally Posted by morrisman

.6" is a rather odd diameter for a ACME thread ? What is it for RC

The 10EE...

I could buy an aftermarket cross slide screw and nut for it but they are over US$300...

If you are planning to use a DRO, it does not really matter how the thread turns out so long as it is good and backlash is not a lot...

Originally Posted by Ueee

I thought it was better to rough the thread out first with a square tool, then cut the acme form? That way you can make the cutter undersize and leave the compound at 90deg and use it to bring the cut to the right width. Keep in mind i have never cut an acme thread......

Ew

Ive done a few now, 10tpi in 4140 and a 5tpi in some mysterium, both multiple times done on fairly tired hercus 9in lathes. I never ran into a need to use two different profile tools. However, I did deliberately grind the tool to be narrower than spec. Id cut the thread to full depth, then realign the tool (using the cross and compound slide against each other) in the opposite direction of the thread movement, and line it up for another series of passes. Using trig you can calculate how far across youre moving and some wire gauging and maths can yeild how much wider you have to go.

This made grinding the tool a lot easier too, all I needed to get right was the angles and take some of the point off. Worked a treat in the end.

I did something similar to Scotty, but used a pin gauge to check the width of land at the bottom of the thread. Seemed to work.

Michael

Originally Posted by Ueee

I thought it was better to rough the thread out first with a square tool, then cut the acme form? That way you can make the cutter undersize and leave the compound at 90deg and use it to bring the cut to the right width. Keep in mind i have never cut an acme thread......

Ew

That's how I do mine, and I've done quite a few. Square threads are dead easy to cut and you then only need to clean up the flanks to get an acme thread form, rather than cutting on all 3 faces (or at minimum, 2 and skimming the third) going at it with an acme tool form.

I *think* that the huge collection of Valenite TC tips I inherited has some acme form tools there but I'm not about to look ATM. There are literally hundreds of boxes of inserts and I don't have a list of what the magic numbers mean, so I have to open every box and use the Mk 1 eyeball.

PDW

Oops wrong thread.

Phil

I managed to make the measuring device OK

I mounted the shaft in the lathe as Stuart suggested , works well

My tip is .008" too wide, so a little more careful grinding is needed .. Mike

Damn after all that hard work.
Ah well, back to the KISS principle.
Well done Mike

Phil

I am still playing around with taps , practice makes perfect

The silver steel I got from Chronos or RDG is horrible stuff - It is very difficult to get a good finish on it .

The flanks of the threads have scouring on them , even though the tool is sharp .

I am yet to buy a ball end mill for the fluting ........... Mike

Looks good Mike.

Is there enough straight section of the tap to get the nut fully threaded?

As far as i am aware, you don't really need a ball end cutter for the flutes, you can use a straight cutter (with radius corners perhaps) and just mill out the flutes. If you take the cut over the center line you will get a slightly positive cutting angle. Not the best pic but this shows it Leadscrew nuts

Cheers,
Ew