Internal thread cutting advice needed

Garth.

Get this free software.

Garth, Perhaps if you read the post on a proper news reader instead of relying on a second hand web feed then you might not miss what's going off in real time.

On or around Tue, 4 Dec 2007 06:31:52 -0600, DR_G enlightened us thusly:

To get accurate metric threads you need a 127 tooth wheel, from my recollection, to do the conversion to metric.

depending on what it's for, 26 TPI is not that far off, but for anything precise or a long thread, it'll not be good enough.

John,

Thanks, that is a great bit of software.

Mr. Shackles,

The thread is only about 15mm long. What tolerance on pitch would yo guys say is reasonable for someting like this?

Thanks,

Garth

-- DR_

----------------------------------------------------------------------- DR_G's Profile:

Indeed; sorry, should have said 1.023 - almost a quarter of a thread. Still not close enough though.

David

Use HSS, no carbides. Slow RPM (60), you'll know when the tool hits the bottom of the bore. Cutting oil.

You should not make an internal thread as your first thread cutting project. Try some external threads before. I warned you! :-)

Nick

Duncan,

Thaks very much for the suggestions. I'm not planning on doing massive amount of threadcutting, so I can't really justify a new moto and inverter. I will give it a go and see what happens, initially will just wind the handwheel back.

Your program looks great - I figured out I could put my own gear set in, but haven't got around to listing what I've got yet! One questio re. the program is the 'filter' button. From what I could find on th help menu (or at least the example menu) I should only get one solutio using this, but with the figures I put in I got about 5. Also, I notice that sometimes you get a list of about 5 or 6 solutions where all th ratios are identical, all gears are identical, but 'driven 2' an 'twist' are different, which I found a bit strange. What exatly i 'twist' by the way?

Thanks very much,

Garth

-- DR_

----------------------------------------------------------------------- DR_G's Profile:

Sadly, Nick, he rarely seems to take much notice of the advice he is given....

--

Chris Edwards (in deepest Dorset) "....there *must* be an easier way!"

That's OK. He can do as he wants. But then he has to accept the laughter when he reports failure. OTOH, he can be proud if the succeeds.

It's just a different way of learning.

Nick

Chris,

Maybe you would like to give some examples of all the advice I hav ignored? Just a couple would do...

Regards,

Garth

-- DR_

----------------------------------------------------------------------- DR_G's Profile:

Well you're getting closer but it would help still further if you divide

Don't make no odds how good the batteries are if you don't press the buttons in the right order.

- almost a quarter of a thread.

Let's try again. 25.4/26 = 0.977mm x 15 threads = 14.65mm = a 0.35mm error. Certainly as you say though, nowhere near close enough.

In article , David Littlewood writes

S*it s*it s*it. Serves me right for not going to bed earlier. Try again!

Mismatch 0.35mm, or about 1/3 of a thread.

(Hides face in embarrassment)

David

In article , Dave Baker writes

Yep, spotted it myself, thanks; correction crossed in post.

David

The filter button stops you getting 50 results all for 1.0123mm (for example). It picks the one that gives the minimum "twist" and bins the others.

"Twist" is how much the quadrant which holds the changewheels is twisted from its normal position. There are a couple of small locknuts on the end of the quadrant which allow it to rotate around the axis of the leadscrew.

Thanks Duncan, that explains it.

I was thinking 'twist' was some kind of torque loading on the quadran or something.

Regards,

Garth

-- DR_

----------------------------------------------------------------------- DR_G's Profile:

Far far too late!

Your sig is noted and any further calculations will be subject to high scrutiny ;-)

Sorry. David, ya won't be smoking a cigar today...

Tom

The dropping of the NP reverberates around the world...

Mounting a dial indicator to your ways so you can pick up the carriage position and unlock/pull out will help. I like to position the indicator so it winds to 12 o'clock where I unlock/pull out as as fast as I can.

HSS, slow spindle, practice first doing an od thread to get your hand and eye sharp.

Wes