Calculating thread depth for cutting threads on a lathe

[Steamwhisperer]

Yes Phil, it's a standard 55 deg, I have some 60 deg tips, I might change to those and see what happens but I should imagine it would only result in a shallower cut depth. I have some more paperwork to study and I'll try things again in a few days time.
Thanks
Stephen

Hi Stephen
what I was alluding to was whether or not the particular insert you are using able to cut the threads per inch you attempted.
I am (almost) confident that inserts have a range of threads per inch they can cut before you need to put a different one in the holder for the next range of threads per inch.
Whether that is 55 deg's or 60 degree's is only a measure of the thread angle and not the amount of threads there is per inch of shank length.
I apologise but I am possibly the worst at explaining things.

Phil
ps after a lifetime of machining and literally hundreds of threads I used an insert to cut a thread maybe 2 months ago. I have only ever used HSS (high speed steel)

[Michael G]

Is it possible to do a nice clean thread by plunging?
I tried it once and made a mess of it.

Yes, but like most things there are conditions. The main reason offsetting is suggested is to reduce the load on the tool and power requirements as that can lead to chatter and other problems. If you have a rigid set up then this is not such a problem. With smaller machines you can still do it but need to be careful with DOC.
So, with a sharp tool, rigid machine and decent lubrication they are not too problematic. On a Hercus sized machine you may be better off setting the post over for coarse threads although you will probably get away with plunging for finer threads (say 25 tpi or more?)

Michael

[nadroj]

Thanks Michael,

It's interesting to know that plunge screwcutting can be nicely done.
I think I'll stick to setting over the top slide and cutting from one side though. It works well and with less risk of drama.

Jordan

[Stephen Gorton]

Hi Stephen
what I was alluding to was whether or not the particular insert you are using able to cut the threads per inch you attempted.
I am (almost) confident that inserts have a range of threads per inch they can cut before you need to put a different one in the holder for the next range of threads per inch.
Whether that is 55 deg's or 60 degree's is only a measure of the thread angle and not the amount of threads there is per inch of shank length.
I apologise but I am possibly the worst at explaining things.

Phil
ps after a lifetime of machining and literally hundreds of threads I used an insert to cut a thread maybe 2 months ago. I have only ever used HSS (high speed steel)

Hi Phil, the inserts are good for threads fro to 4 TPI,I have given it another go and I'm pleased to say I'm close. Its obvious it's a skill learnt over many years, Imay have been able to pick it up faster in my younger years when I couldremember where my car keys were LOL, but I am still enjoying learning though itseems to take longer these days.

[Steamwhisperer]

Hi Phil, the inserts are good for threads fro to 4 TPI,I have given it another go and I'm pleased to say I'm close. Its obvious it's a skill learnt over many years, Imay have been able to pick it up faster in my younger years when I couldremember where my car keys were LOL, but I am still enjoying learning though itseems to take longer these days.

It sounds like you are winning Stephen and once you get your head around it, it can be surprisingly easy.
What I am liking about old(er) age is walking into the shed to do something and standing there for 10 minutes wondering what the hell it was I was going to do
It's more embarrassing when the missus walks in. Then I normally pick up a piece of steel and take it to the other side of the shed and put it down, grab the previous piece I put there and do the reverse.
She gets bored by this stage and I stand there for another 10 minutes.

Keep giving this screwcutting a crack as it can be very exciting when it works out to be what you were after plus you will save a fortune on dies
If you can private message me your email address I have a couple of good books on the subject in 'Dropbox' that you should be able to access.

Phil

[pipeclay]

Not sure exactly on the insert that your using but I think you are pushing the boundaries with what you have.

You haven't stated what the tip it is that you are using but I would think larger than an ER16,
you should be looking at an ER11 for your fine thread as this will be better suited, good luck with how they turnout.

[Stephen Gorton]

Not sure exactly on the insert that your using but I think you are pushing the boundaries with what you have.

You haven't stated what the tip it is that you are using but I would think larger than an ER16,
you should be looking at an ER11 for your fine thread as this will be better suited, good luck with how they turnout.

Sorry pipeclay, I didn't check what I typed, forsome reason my type doesn't always finish up where I want it, the tips are goodfrom 8 to 48 tpi and yes they are ER16, I will take your tip and look forER11's, that may be where I'm going wrong

Thanks Stephen

[pipeclay]

You will need a tool to suit the 11 tip, the threading tips are not interchangeable.