griping on OD of thread

[lumley32]

I've got 6000 parts to make that is 40mmOD with a 1mm pitch thread on the outside in aluminum. would really like to move it to our sub-spindle lathe but not sure how to hold on the second opp.

do you just turn the chuck pressure down and grip on the thread with soft jaws?

 

[William Lynn]

Make a split sleeve.

 

[lumley32]

just added the quantity of the parts, it needs to run unatended.

 

[Milland]

Which Al alloy, what can you get away with for thread OD minimum diameter? Intensive secondary work, or minimal?

If you can go near the min OD you should have small flats on the thread peaks. If a hard alloy like 7075, or even 6061, then smooth steel soft jaws bored to actual OD should be fine as long as you're not hogging. Make sure you can drop into a tray or basket or whatever when done without damaging the threads.

 

[RJT]

Can you use a collet, step cuck or pie jaws? Grab as much as of the thread as you can (length and circumference). We do it quite often, and yes limit your rough cuts to minimize torque.

 

[RC Mech]

Holding on the thread is a last resort. Are you certain creative tooling could not be used to flips ops and have the thread be done in the sub?

I may know the answer to that and for the life of me I can’t understand why TF, for the price, MTB’s don’t have encoders on the sub.

 

[implmex]

Hi RC Mech:
Are you telling me that sub spindles don't commonly have spindle encoders on them and that you can't run threads on them.
I didn't know that...and I'm shocked!

I always assumed the sub was basically just as capable as the main on any modern subspindle lathe.
Is this commonly the case or are there only a few machines out there with this particular limitation?
(I was gonna recommend the OP find a way to run the thread last too, but I guess maybe not.
I wonder if he can back turn them on the main?)

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

 

[RC Mech]

Hi RC Mech:
Are you telling me that sub spindles don't commonly have spindle encoders on them and that you can't run threads on them.
I didn't know that...and I'm shocked!

I always assumed the sub was basically just as capable as the main on any modern subspindle lathe.
Is this commonly the case or are there only a few machines out there with this particular limitation?

Right? I’ve run beautifully optioned DMG and Hwacheon lathes, from 2019-2021 model years and both had no encoders on the sub. Had to thread everything in the main.

The damn Hwacheon had live tools but no indexing on the sub so hex flats as a 2nd op was out of the question too.

 

[implmex]

Hi again RC Mech:
I can see why you're incredulous and pissed, all at the same time.
What bonehead would design a lathe that way.
What were they smoking?

I'll betcha they had all kinds of door interlocks to keep us from doing our jobs easily though!

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

 

[guythatbrews]

I run thousands of parts in sub holding on threads. Major diameter is on nominal. Held in a collet. Mostly brass but some alumimum parts all sizes up to 1.25". Sometimes it is the only way that makes sense, or the only way possible.

As said before, in a chuck use carefully bored jaws. At 40mm you probably don't need to but use pie jaws for bigger diameters. If you see chucking witness marks work the edges of the jaws over a tiny bit. And you can't go at it hammer and tongs but you may be surprised what you can get away with.

 

[implmex]

Hi All:
40mm diameter x 1 mm pitch sounds pretty fine...almost like an optical thread.
If we use the rule of thumb of 1/8 pitch for the crest width, those crests are about 0.005" wide...not a lot to squeeze on in aluminum unless it's 7075 or 2024.

I've never tried it, so I'm gonna defer to those who have.
But I'd want to see those threads under the microscope before I committed to running all 6000 parts.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

 

[plastikdreams]

What part of the threads are you griping about? What did they do to you?

 

[Orange Vise]

Right? I’ve run beautifully optioned DMG and Hwacheon lathes, from 2019-2021 model years and both had no encoders on the sub. Had to thread everything in the main.

The damn Hwacheon had live tools but no indexing on the sub so hex flats as a 2nd op was out of the question too.

Which models of DMG?

Our 2014 NLX2500SY has full C-axis and threading on the sub.

Our two Haas ST20Ys and our ST30Y have 5-degree indexing on the sub and will also allow threading on the sub.

 

[gustafson]

If you are in control of the thread, I see no problem. You can choose to over spec the thread to assure repeatability, as opposed to trying to hold some rolled thread POS you got supplied to you

 

[sinha]

Can you use a collet, step cuck or pie jaws? Grab as much as of the thread as you can (length and circumference). We do it quite often, and yes limit your rough cuts to minimize torque.

I always wondered why a pie jaw called a pie jaw.
When I searched the net, this is the answer I got ...
The Greek word περιϕέρεια means “circumference” or “periphery”.It has been abbreviated to its first letter π which is used as a mathematical symbol (for 3.14....) in the context of a circle. Thus, pie implies circumference, and pie jaw means circumference-holding jaw.

 

[guythatbrews]

I always wondered why a pie jaw called a pie jaw.
When I searched the net, this is the answer I got ...
The Greek word περιϕέρεια means “circumference” or “periphery”.It has been abbreviated to its first letter π which is used as a mathematical symbol (for 3.14....) in the context of a circle. Thus, pie implies circumference, and pie jaw means circumference-holding jaw.

I always thought it looked like a big piece of pie. Not a big piece of pi.

 

[lumley32]

ok, more info...
its 6082T6 aluminum, so hardish.
the part is 9mm thick with threads on the full length.
there is a through hole, I guess I could get hold of from the inside but it's only 12mm.
full C on both spindles so can make the part in any order.
all i want to do on the sub side is face and a shallow CB, so cutting forces will be light.

 

[sinha]

I always thought it looked like a big piece of pie. Not a big piece of pi.

It can hold a pie, without damaging it!

 

[EmGo]

I always wondered why a pie jaw called a pie jaw.

 

[guythatbrews]

Awww why'd you do that? Time for breakfast and not a slice of pie in the house!