I do it quite often except I have a tool the right way up behind the work and just run in reverse, have suggested it a few times on here as you can run at a decent speed due to having miles of room to stop.

Edited By JasonB on 11/05/2019 16:57:54

Jason B:

You have not mentioned this in vain.

However, the direct import Chinese tool-holder I used to try this would, I think, only be usable with relatively short threads. I was surprised by how well this method worked given that the tool seems to be working the wrong way round in relation to the helix angle of the thread.

I found also that the work is more difficult to see working like this and it was obviously necessary to be very disciplined about moving switches and levers in the appropriate direction.

Light bulb moment: running the tool upside down at the front would deal with my visibility problem – thank you!

There is a simple safeguard to stop the chuck unscrewing: A length of threaded rod through the spindle hole with a large washer or even a piece of flat bar with hole drilled in it holding the chuck in place. Other end of the threaded rod has a nut and washer that is nipped up. Simples.

Done it on a Myford Super 7 for 15 years, you have to cut a massive thread in one pass to dislodge a well fitted Myford chuck.

I do all my threading with an inverted tool away from the chuck, no need for thread relief either, I just go straight into the finished depth pull back out then thread in stages as normal just in reverse, works a treat and more importantly for me safer.

Alan.

It's probably like welding petrol tanks, maybe one in a thousand goes wrong. Just don't be that one…

How are you plunging in to the metal with no relief?
Instant busted tip guaranteed every time not to mention aligning the start every time = impossible.

Most blind hole have no relief

Perhaps your chuck is jammed, it's a well known Myford problem…

"

Whats the problem with that?

Is it because its not a drill or a D bit or any other kind. "

Try milling with it. Once you've seen one rattle and exit the chuck, you won't do it again.

Regards Ian.

Edited By Circlip on 14/05/2019 12:14:19

If you do think your chuck may screw off then the upside down and reverse method can still be used if the tailstock ctr is brought up for support as the chuck won't unscrew against that. Good idea anyway if threading slender items.

A more useful comment than "don't do it on a screwed chuck machine" , would have been to say take precautions to stop the chuck coming off if doing it on a threaded spindle machine.

Now just need to go and remake that Minnie of mine where all the milling was done with the cutters in a drill or 3-jaw chuck

Edited By JasonB on 14/05/2019 13:10:35