Thread: What speed for internal threading

For a 1st attempt at blind hole threading I would be running the lathe at its lowest RPM.

I understand that the cutting specs for your Tip will suggest a higher RPM but it should still be ok at a lower RPM.

If you feel that it wont be good for your Tip or the finish of the thread I would suggest to change to HSS.

Is the thread running to a Shoulder or Undercut.

An undercut would be better,it would at least give you a little leighway before you tool possably crashes into the end of your work piece.

You have a couple of choices for finding the right spot to disengage if you have got a mechanical means of either stopping the Spindle or disengageing the Leadscrew.

1 would be to put a mark on your Lathe bed when the threading tool has reached the correct length,when the carriage gets to this mark dissengage your Clasp nuts.

2 would be to use a Dial Indicator attached to the Lathe bed or other position which is ridgid,set the length of your thread,bring the Dial Indicator up so that it is registering on your carriage by .100"/.200" or 3mm/5mm and set on Zero,work to this indication and disengaged the Clasp Nut.

Hi Jackaroo,
As fast as you can while still being in control, I don't think the AL960 has a brake.
If I am threading something like that I will pick the slowest gear which on mine is 65 rpm because I don't have a brake.
If you have a recess to start in or a through hole, you could bore it away from the spindle with the lathe running in reverse. That way you can run at any speed you want and not run into troubles.

Dave

Hi Jackaroo,

I generally put a relief groove inside the end of the hole to give plenty of room for the bit to run around in once your dial says your there. The speed is something you could practice with on some external stuff of the same Dia till you get hang of it. Once you feel good with the external practice you will know you can trust the internal. I'm only a novice also in this area so I thought it might be good to get an opinion from someone who is just a bit ahead of you so you might better understand the lingo hey, because some guys in the know talk in a strange language, or at least they do to me.

Regards...Oddjob1

Thanks All for the tips

I'll give it a try tonight to see how it goes. I have 2 chucks and i made this before. for the tailstock. I am trying to make the adaptor for the mill (just imagine a female to go on this)

Reverse sounds like a good idea. I'll have to grind the hss instead of the insert then.

Thats real nice machine work there mate, Did you use a tap for the draw bar end or cut it on the lathe?

I agree, it came out nice.

Dave

Hi again Jackaroo,

yes I can imagine the female on it, not being very deep you should be able to see your tool reach bottom and also with the dial gauge you shouldn't be nervous being your first time. But practice makes perfect as my wife always says.

Nice job...Oddjob1

Jackaroo,
Consider the possibility of running the thread right through the workpiece, then no worries about where to stop.

If you want it closed for cosmetic, or other, reasons, you could Loctite a plug in afterwards.

John

Hi All,

I got it done by running on reverse like Dave suggestion.
First attempt on carbide at 120rpm with undercut went well until the level got stuck one time and it hit the end...broke the insert

Yes no brake on it and its a bit nervous when running forward the end, very stressful when looking at the mark as it goes in.

@Matthew, I used drill/tap with M10 for drawbar

@oddjob1, I cant put locktie on it as I will ave to put the chuck back on the spindle so cosmetic is also important.

Thanks again everyone, I learned quite a lot from this site. I should have the piece done after work tomorrow.

Good to hear you got it done,
even if it did cost an insert (I hate when that happens)

Don't forget to post some photos when you finish it.

Dave

Thanks all, here is the product.

Looks good, and the threads came out great. is it all one piece?
Also did you end up with much runout?

Dave

Hi Dave,

Yes its from one piece. The spindle end was done on the Al960 but the collet end was done on the myford itself.

Jackaroo

Hello Jackaroo,
I'm Glad your job turned out OK. I would have probably taken the chicken's way and just turned the chuck by hand. I have often used that method on short threads when coming up to a shoulder. On longer threads, I turn the power off well before the end and finish the last part of the cut by hand. If you don't tell anyone, they wont know.
Regards, Russell