Converting 1948 Leblond Regal english threading to metric

Steve F · Aug 1, 2013

Quick question. Wouldn't it be easier to replace the lead screw and half nuts with a metric screw than manipulating the gears?.

Putch · Aug 1, 2013

Maybe if you only ever wanna cut metric threads...can you do the math to figure out what pitch leadscrew would give you all your metric threads?

John Hill · Aug 1, 2013

You can effectively convert your imperial lead screw to metric by adding a 120/127 compound gear to your gear train.

johnoder · Aug 1, 2013

Steve F said:
Quick question. Wouldn't it be easier to replace the lead screw and half nuts with a metric screw than manipulating the gears?.

Sure, easy to see you only get partial usage though.

Lets say you replaced a 6 TPI lead screw with a 4mm lead screw (and half nuts) and did nothing else. Let's say the coarsest thread was 4 tpi in the QC gear box

4 TPI position would cut 6 mm thread
4 1/2 TPI position would cut 5.3333mm thread
5 TPI position would cut 4.8mm thread
6 TPI position would cut 4mm thread
6 1/2 TPI position would cut 3.6933mm thread
7 TPI position would cut 3.4285mm thread
8 TPI postion would cut 3mm thread (halves the 4 TPI position)

and so on

Joe Michaels · Aug 1, 2013

LeBlond offered metric transposing gears for the round head Regal lathes. I was fortunate in that my 13" Round Head Regal lathe (1943 machine) has the extra quadrant gears for cutting metric threads. Several participants on this 'board clued me in to the change gears and corresponding positions of the quick change gear box to cut popular metric pitches. It is actually quite a simple matter to swap over to the "transposing gear" on the quadrant, and a whole lot simpler and less expensive than swapping out the lead screw and half nuts. As John Oder notes, the quick change gearbox would not cut the common metric pitches even if you were successful in changing out the lead screw and half nuts. The metric change gear allows the lathe to cut 0,25 ; 0,50; 0,75; 1,0; 1,25 mm and a few other metric pitches- all of which are the standard or common pitches.

Steve F · Aug 1, 2013

Thanks for the info. I was reading another thread about using change gears for metric thread and the author mentioned you couldn't use the chasing dial. I wondered if changing the lead screw would make the chasing dial work. Do you cut metric threads in one pass? Or does the chasing dial work with the metric transposing gears? What are the odds that metric transposing gears are still available for sale somewhere?

ratbldr427 · Aug 2, 2013

You leave the half nuts engaged until you finish,you reverse the lathe after each pass.The metric dials use a set of gears for the different pitches.Make or buy the transposing gears.I have an old 1924 Dalton lathe that came with a set of change gears that cut most all the common metric pitches,so it is nothing new.
Randy

DocsMachine · Aug 2, 2013

ratbldr427 said:
You leave the half nuts engaged until you finish,you reverse the lathe after each pass.

Question relating to this: I'm looking at an old Springfield lathe, that has a feed-reverse lever on the apron. As I understand it, you can thread as normal, except that when you reach the end, instead of retracting the tool, stopping the feed, and manually cranking the carriage back to the start, you can just retract the tool and hit the reverse lever, which runs the carriage back under power.

The halfnut stays engaged, as you have to do when threading metric on an imperial machine, but I'm not sure the feed reverse works the same way The spindle keeps going forward, but the leadscrew reverses direction. Would this work for metric threading, or would it lose indexing?

I suspect it doesn't work that way, but I'm curious to know, anyway.

Doc.

Hopefuldave · Aug 2, 2013

DocsMachine said:
Question relating to this: I'm looking at an old Springfield lathe, that has a feed-reverse lever on the apron. As I understand it, you can thread as normal, except that when you reach the end, instead of retracting the tool, stopping the feed, and manually cranking the carriage back to the start, you can just retract the tool and hit the reverse lever, which runs the carriage back under power.

The halfnut stays engaged, as you have to do when threading metric on an imperial machine, but I'm not sure the feed reverse works the same way The spindle keeps going forward, but the leadscrew reverses direction. Would this work for metric threading, or would it lose indexing?

I suspect it doesn't work that way, but I'm curious to know, anyway.

Doc.

Hi Doc,
Depends on whether the reverse is by gears (usually bevel) in the apron, acting on a feedshaft that doesn't reverse, or in the headstock/QCGB and reverses the leadscrew. Even if it reverses the leadscrew, it needs to be a single-tooth dog clutch running at spindle speed to maintain the relationship between spindle and leadscrew and hence stay on the same thread helix... Although it's aimed (I think) at the hobbyist, Martin Cleve's "screwcutting in the lathe" does a thorough job of explaining imperial/metric threading on the "wrong" leadscrew, conversion gears, leadscrew-reverse etc., well worth a read.

If the Springfield's anything like the ones on the lathes.co.uk site, that's a beast...

Dave H.

johnoder · Aug 2, 2013

As I understand it, you can thread as normal, except that when you reach the end, instead of retracting the tool, stopping the feed, and manually cranking the carriage back to the start, you can just retract the tool and hit the reverse lever, which runs the carriage back under power.

Revise this thinking enough to retract tool to accommodate the various backlashes in the system

See post #17 here for how Hendey's system worked:

http://www.practicalmachinist.com/vb/antique-machinery-history/hendey-lathe-emergency-113621/

DocsMachine · Aug 2, 2013

Hopefuldave said:
Depends on whether the reverse is by gears (usually bevel) in the apron, acting on a feedshaft that doesn't reverse, or in the headstock/QCGB and reverses the leadscrew.

-I'm pretty sure the lever on the apron works a gear change of some sort in the QC box. The lever doesn't appear to have an actual linkage to the apron- just a "carrier bearing" of sorts- and works a square rod that runs back into the QCGB.

If the Springfield's anything like the ones on the lathes.co.uk site, that's a beast...

-I wish.

No, those are mid-50s and newer. The one I'm looking at is a '43, if we're reading the serial number right:

She's still a beast though.

Doc.

Steve F · Aug 2, 2013

ratbldr427 said:
You leave the half nuts engaged until you finish,you reverse the lathe after each pass.The metric dials use a set of gears for the different pitches.Make or buy the transposing gears.I have an old 1924 Dalton lathe that came with a set of change gears that cut most all the common metric pitches,so it is nothing new.
Randy

I've got the 2 1/8 5tpi threaded spindle, so reversing is not a good idea with this lathe. Maybe it's time to put a CNC on my Hardinge DV59.

makinthings · Jun 20, 2019

Sorry to revive a dead thread, but can you please post a picture of what that looks like? I'm trying to figure out how to do this for my lathe and I don't even know what I'm looking for or how it will install!

Thanks

johnoder · Jun 20, 2019

makinthings said:
Sorry to revive a dead thread, but can you please post a picture of what that looks like? I'm trying to figure out how to do this for my lathe and I don't even know what I'm looking for or how it will install!

Thanks

(I'll assume you refer to a lead screw reverse system - as used on many high end tool room lathes)

Thumbnail is the reversing bevels UNDER the Hendey head stock. The shuttle with the groove for a shifting fork selects the forward and reverse rotation of the lead screw. Since NOTHING is ever out of gear and the single tooth clutches always engage at the same place, NOTHING ever gets out of time in relation to spindle rotation.

If you don't have this feature - or an equally functioning other design - you DON'T have a workable lead screw reverse

john.k · Jun 20, 2019

A self opening Coventry type diehead will cut perfectly satisfactory metric ,or any other threads.......and can be used immediately,rather than embarking on a ten year long project......that will inevitably end up with a dismantled lathe with bits missing.

Froneck · Jun 20, 2019

DocsMachine said:
Question relating to this: I'm looking at an old Springfield lathe, that has a feed-reverse lever on the apron. As I understand it, you can thread as normal, except that when you reach the end, instead of retracting the tool, stopping the feed, and manually cranking the carriage back to the start, you can just retract the tool and hit the reverse lever, which runs the carriage back under power.

The halfnut stays engaged, as you have to do when threading metric on an imperial machine, but I'm not sure the feed reverse works the same way The spindle keeps going forward, but the leadscrew reverses direction. Would this work for metric threading, or would it lose indexing?

I suspect it doesn't work that way, but I'm curious to know, anyway.

Doc.

I had a Springfield lathe, The lead screw reverse will work for either Inch or Metric threads. If you have the Inch lead screw you will of course need to use the change gears 127/120 compound set then calculate additional gearing. If you calculate various ratios available in the quick change you will find quite a few metric threads can be had from one gear change. Machinist Hand book does have a section on how to calculate the needed gearing. I have Hendeys and a P&W with lead screw reverse and do quite a bit of metric threading with them though all of them have Inch lead screws and I calculate the gears needed and use lead screw reverse.

Hudson · Jun 21, 2019

Current issue (July/August 2019)of the "Home Shop Machinist" has a good article on cutting metric threads on an Imperial lathe. Includes cutting a 127 tooth gear if cannot locate one for your quadrant.

Fair number of pictures.

T W Hudson

makinthings · Jun 21, 2019

john.k said:
A self opening Coventry type diehead will cut perfectly satisfactory metric ,or any other threads.......and can be used immediately,rather than embarking on a ten year long project......that will inevitably end up with a dismantled lathe with bits missing.

Lmao. I just spend 8 long months with 250 nuts and bolts laying around as I rebuilt my lathe from a "quick" project. On the upside, I'm very comfortable with replacing parts [emoji14]

Sent from my CLT-L04 using Tapatalk

makinthings · Jun 21, 2019

Hudson said:
Current issue (July/August 2019)of the "Home Shop Machinist" has a good article on cutting metric threads on an Imperial lathe. Includes cutting a 127 tooth gear if cannot locate one for your quadrant.

Fair number of pictures.

T W Hudson

Ahhhh! Amazing! I was thinking of going that very route!

Sent from my CLT-L04 using Tapatalk

makinthings · Jun 21, 2019

johnoder said:
(I'll assume you refer to a lead screw reverse system - as used on many high end tool room lathes)

Thumbnail is the reversing bevels UNDER the Hendey head stock. The shuttle with the groove for a shifting fork selects the forward and reverse rotation of the lead screw. Since NOTHING is ever out of gear and the single tooth clutches always engage at the same place, NOTHING ever gets out of time in relation to spindle rotation.

If you don't have this feature - or an equally functioning other design - you DON'T have a workable lead screw reverse

Thanks!... But unfortunately not at all how my leblond is built... Hum.... Oh well. Quarter gear it will be.

Sent from my CLT-L04 using Tapatalk

Converting 1948 Leblond Regal english threading to metric

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