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Upside down reverse threading

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Danny M2Z11/05/2019 15:05:20
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745 forum posts
278 photos

I have noticed that a few gunsmiths advocate this technique. They are cutting a barrel tenon away from a fixed shoulder and I must admit that it is new to me but it seems to make sense - here is a linky UDRT

Any thoughts on this as a general technique considering that most forum members to not thread barrels?

duncan webster11/05/2019 16:08:18
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2232 forum posts
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Don't try this on a lathe with a screwed on chuck, for obvious reasons

JasonB11/05/2019 16:27:45
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Moderator
16269 forum posts
1721 photos
1 articles

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

Nick Hughes11/05/2019 16:49:10
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201 forum posts
130 photos

No problem with the Myford screwed on chuck when I did it:-

20190223_105748.jpg

Edited By Nick Hughes on 11/05/2019 16:50:29

ega11/05/2019 17:12:14
1265 forum posts
108 photos

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.

XD 35112/05/2019 06:58:21
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1326 forum posts
112 photos

Also used for threading blind holes like threaded end caps etc .

ega12/05/2019 08:35:11
1265 forum posts
108 photos
Posted by Nick Hughes on 11/05/2019 16:49:10:

No problem with the Myford screwed on chuck when I did it:-

20190223_105748.jpg

Edited By Nick Hughes on 11/05/2019 16:50:29

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

not done it yet12/05/2019 08:57:01
3357 forum posts
11 photos
Posted by Nick Hughes on 11/05/2019 16:49:10:

No problem with the Myford screwed on chuck when I did it:-

20190223_105748.jpg

Edited By Nick Hughes on 11/05/2019 16:50:29

Yes, that was clearly so - but would you accept the blame when someone ends up with his chuck on his/her toes?

Hopper12/05/2019 10:54:58
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3706 forum posts
73 photos
Posted by not done it yet on 12/05/2019 08:57:01:
Posted by Nick Hughes on 11/05/2019 16:49:10:

No problem with the Myford screwed on chuck when I did it:-

20190223_105748.jpg

Edited By Nick Hughes on 11/05/2019 16:50:29

Yes, that was clearly so - but would you accept the blame when someone ends up with his chuck on his/her toes?

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.

not done it yet12/05/2019 13:00:36
3357 forum posts
11 photos

So it is no good for any workpiece which might pass through the chuck and into the spindle? Special cases can often be contrived, but simply stating that screw on chucks can be used in reverse is not good information for new starters - who are more likely to get the chuck on their toes.

Nick Hulme12/05/2019 17:18:35
703 forum posts
37 photos
Posted by duncan webster on 11/05/2019 16:08:18:

Don't try this on a lathe with a screwed on chuck, for obvious reasons

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.

Nick Hulme12/05/2019 17:20:48
703 forum posts
37 photos
Posted by not done it yet on 12/05/2019 13:00:36:

So it is no good for any workpiece which might pass through the chuck and into the spindle?

It's fine, all the "experts" haven't actually done it, or if they have and hit this problem they had left their chuck loose :D

Alan .20413/05/2019 00:07:21
304 forum posts
14 photos

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.

thaiguzzi13/05/2019 05:00:19
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573 forum posts
130 photos
Posted by not done it yet on 12/05/2019 08:57:01:
Posted by Nick Hughes on 11/05/2019 16:49:10:

No problem with the Myford screwed on chuck when I did it:-

20190223_105748.jpg

Edited By Nick Hughes on 11/05/2019 16:50:29

Yes, that was clearly so - but would you accept the blame when someone ends up with his chuck on his/her toes?

Not at screwcutting speeds.

Screwcutting on my Boxford in reverse @ 50 rpm and a low DOC is not going to unscrew a chuck.

Hopper13/05/2019 05:24:09
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3706 forum posts
73 photos

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

Circlip13/05/2019 12:00:05
978 forum posts

In a similar vein, left an American ME site after arguing with a colonial about NOT using a milling cutter in a drill chuck.

"I've been doing it for years" was the retort.

Regards Ian.

Jon13/05/2019 20:03:55
988 forum posts
46 photos
Posted by Alan .204 on 13/05/2019 00:07:21:

I do all my threading with an inverted tool away from the chuck, no need for thread relief either, I just go straight in

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

Jon13/05/2019 20:06:51
988 forum posts
46 photos
Posted by Circlip on 13/05/2019 12:00:05:

In a similar vein, left an American ME site after arguing with a colonial about NOT using a milling cutter in a drill chuck.

"I've been doing it for years" was the retort.

Whats the problem with that?

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

SillyOldDuffer13/05/2019 20:41:45
4711 forum posts
1010 photos
Posted by Nick Hulme on 12/05/2019 17:18:35:
Posted by duncan webster on 11/05/2019 16:08:18:

Don't try this on a lathe with a screwed on chuck, for obvious reasons

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.

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

Alan .20413/05/2019 21:30:45
304 forum posts
14 photos

John, when the tip of the insert is where I want it I set a DTI on the bed way so every time I come back I start in the same place, I have brocken tips yes but not doing it like this, as for plunging what ever the finished depth is I go to depth in full then come back to the start of the depth so to speak and add more depth each time I make another pass, I’ve had no problems at all, give it go if you don’t believe me, I will be making some collet holders soon I’ll put it on my ytube channel you can have a look if you want to, just because you haven’t done something a certain way yourself doesn’t mean you should dismiss it ?

Alan.

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