Jet lathe

[Sumboodie]

Picked up an 80s 13x40 lathe at auction.

It's missing the chuck and toolpost so looking at options.

Is a 10 or 12" chuck the right size to use?... ie should I use the biggest that'll fit?

Apparently these lathes use a backplate that threads, chuck bolts to it. That mean no "backward" work???? Chuck would unscrew?

 

[Mgdoug3]

I would say a 6" 3 jaw chuck and a 8" 4 jaw is more appropriate for that size lathe. I have a 10" and 17" lathe. I use 5 and 6" chucks on my 10 and 10" chuck on my 17.

You could probably go bigger on the chucks but thats extra weight on the spindle and you'll have to watch to make sure the jaws can clear the carriage or ways when you turning something larger.

 

[Sumboodie]

How big of a shaft will a 10" clamp on the od?

 

[whateg01]

I have an 8" 3 and 8" 4 which do most of the work. But I also have a 5" 3 because the 8" won't grip smaller than about 0.450". Sometimes I'll throw a collet block in it, but often I grab the shaker chuck. I also have a 4" 3 that I stick in the 8 " 4. Then you have to get a Jacobs collet chuck. And a 5C. And face plates. And a dog plate. And another lathe...

 

[GeoBruin]

How big of a shaft will a 10" clamp on the od?

Keep in mind, many chucks have inside and outside jaws, do you csn clamp something almost as large as the chuck (10" in the case of a 10" chuck).

The thing you have to remember, is that the jaws are going to stick out past the edge of the round part of the chuck. So if you have a 10" chuck, the jaws are only going to be able to open a little past the edge, which means the clamping capacity will be limited anyway. With a smaller chuck, (say, 8") the jaws can open much wider without hitting anything, so you don't really lose as much clamping capacity as you think with the smaller chuck.

Oh, and chucks are really heavy. Like really heavy. They get too big and changing chucks ceases to become a 1-man operation without a crane.

 

[Sumboodie]

It's a gap bed lathe so was thinking it'd clear that way.

Had I think a 6" chuck at the 12?x36 at a shop I worked at and it was fairly useless. Maxed out at maybe 1.5"
Maybe was just a crappy chuck though. Jaws weren't reversible, they only fit into the scroll 1 way.

 

[dutchgray]

I have an English 13" lathe.

I have a 10" 3 jaw with both inside and outside jaw sets, make sure a chuck bought used comes with both or that you can buy a new set, or buy a new 3 jaw chuck.

A 12" 4 jaw independent chuck, this you should be able to buy used as they often never get used so can be found in basically new condition for little money.

I also have a 10" 4 jaw.

You can go bigger and use the gap but you have to work out if there is any need to, will the machine actually run work that large diameter successfully.

Faceplate, find a used on if you can with the correct spindle mount that is as big as will swing in the gap.

A collet chuck is useful for the smaller diameter work, 5C or an ER style to your preference.

Can you buy the threaded backplates for your spindle or are you going to have to make them?

What's your max spindle speed? The larger chucks might not run at it unless you buy expensive steel ones, an 8" might be perfect for much of your work, worth checking the chuck bore is at least as big as the spindle bore.

 

[dutchgray]

And yes threaded spindles generally speaking you don't run in reverse, as they can unscrew and throw the chuck off.

 

[GeoBruin]

It's a gap bed lathe so was thinking it'd clear that way

Should have lead with that

 

[darkzero]

I agree, for a 13x lathe I would go 6.3" 3-jaw & 8" 4-jaw. Or 8" & 10". 12" is pushing it IMO for a 13x. Keep in mind that a 12" chuck will take longer to spin up & spin down. I only have a 12x but I use my 6.3" chucks the most. I also swap chucks pretty often. I wouldn't want to be swapping out a heavy chuck that often.

Also, it's spec'd as 13" swing. With a 12" chuck & the jaws fully extended, the jaws may hit the ways. Some will say they won't need to ever extend that jaws out that far or they can just remove the gap if they have one. Sure ok, but what's the point in having such a large chuck for your machine if you can't use the most out of it.

The only reason I see to have an oversized chuck is to get you a bit more largeer through hole depth into the chuck. But the spindle through hole will most likely still be smaller than the chuck through hole.

 

[Sumboodie]

Don't have any plans for a 4 jaw. 3 jaw should be fine for anything I'm doing.

 

[darkzero]

If you get more serious into it & continue with the hobby, you'll need a 4-jaw..... and whole bunch of other stuff too!

I don't use mine very often but I wouldn't want to be without a 4-jaw. But then again I would want to be without my other 5 chucks too.

 

[Aaron_W]

Very rough rule of thumb on chucks is 50-60% of swing, 4 jaw can go a bit larger since the jaws don't extend as far past the chuck body as on a 3 jaw.

Assuming the 13x40 lathe is truly a 13" swing (often times they are bigger than the nominal swing, some significantly so) then a 6" would be safe, and an 8" would probably work. 4 jaw 8" maybe up to a 10".

It's a gap bed lathe so was thinking it'd clear that way.

Had I think a 6" chuck at the 12?x36 at a shop I worked at and it was fairly useless. Maxed out at maybe 1.5"
Maybe was just a crappy chuck though. Jaws weren't reversible, they only fit into the scroll 1 way.

I bet that was a chuck with separate inside and outside jaws and it was missing the outside set. I have a 6" 3 jaw on my 11" lathe and can fit probably a 5" piece using the outside jaws. I haven't needed to work on something that large but the jaws open wide enough that it should be able to.

 

[RoninB4]

This isn't my experience but something I've read on a machinist board. If you pull the section of a gap bed lathe the section won't go back in exactly as before, implying that there will be a slight mismatch in the ways that will show up on the work when the saddle reaches the mismatch. This has been echoed by several other members. Perhaps this could be from the bed flexing or just not enough care taken to have immaculate mating surfaces. This may/may not make a difference with the work you do. I have a removeable section on my Weiler but I've never taken it out, haven't needed to and don't want to find out what happens.

Agree with what others have posted, smallest chuck I can get away with (mass/swing interference) and wouldn't want to be without an independent 4 jaw. I don't use it very often but when I do nothing else will take the place of it. My spindle is also threaded but has large set screws to lock on so I can run in reverse for lighter cuts. If there are no provisions for locking a threaded spindle I would NOT run it in reverse.

 

[Mgdoug3]

I keep two 4 jaw chucks on both of my lathes and only switch if I'm doing a production type job. With a little bit of practice, you can have near zero runout in a minute. If I have a hex shaft, I'll use my 3 jaw. If I doing a high production job under 1-1/16", I'll use my 5c collets.

 

[alfadan]

This isn't my experience but something I've read on a machinist board. If you pull the section of a gap bed lathe the section won't go back in exactly as before, implying that there will be a slight mismatch in the ways that will show up on the work when the saddle reaches the mismatch. This has been echoed by several other members. Perhaps this could be from the bed flexing or just not enough care taken to have immaculate mating surfaces. This may/may not make a difference with the work you do. I have a removeable section on my Weiler but I've never taken it out, haven't needed to and don't want to find out what happens

I don't have a gap bed lathe, but as long as the surfaces are clean and without damage, the gap should go back just fine IF you indicate it. Keith Fenner has a couple of good videos on reinstalling the gap. I wouldn't be afraid of it. Lazy yes, but not scared

 

[Sumboodie]

If you get more serious into it & continue with the hobby, you'll need a 4-jaw..... and whole bunch of other stuff too!

I don't use mine very often but I wouldn't want to be without a 4-jaw. But then again I would want to be without my other 5 chucks too.

Just using it for stuff like pins, bushings, etc for equipment. Not a hobby.

 

[Sumboodie]

Very rough rule of thumb on chucks is 50-60% of swing, 4 jaw can go a bit larger since the jaws don't extend as far past the chuck body as on a 3 jaw.

Assuming the 13x40 lathe is truly a 13" swing (often times they are bigger than the nominal swing, some significantly so) then a 6" would be safe, and an 8" would probably work. 4 jaw 8" maybe up to a 10".



I bet that was a chuck with separate inside and outside jaws and it was missing the outside set. I have a 6" 3 jaw on my 11" lathe and can fit probably a 5" piece using the outside jaws. I haven't needed to work on something that large but the jaws open wide enough that it should be able to.

Thanks for the help.

My brother is a machinist/manufacturing engineer but getting help from him has been like pulling teeth.

 

[Sumboodie]

I don't have a gap bed lathe, but as long as the surfaces are clean and without damage, the gap should go back just fine IF you indicate it. Keith Fenner has a couple of good videos on reinstalling the gap. I wouldn't be afraid of it. Lazy yes, but not scared

It's a 45 year old Chineese lathe, not expecting to build NASA parts on it.
Half the stuff I do +- 0.0625" is getting fussy.

 

[RoninB4]

I don't have a gap bed lathe, but as long as the surfaces are clean and without damage, the gap should go back just fine IF you indicate it.

-"Should" and "do" are often two different things. Indicate? The machinist board members that posted their experience probably have far more experience with indicators and precision assemblies then most. Do you understand how flexible a lathe bed can be? May I ask what background you have that has led to your untested belief?

I wouldn't be afraid of it. Lazy yes, but not scared

-Enthusiasm not tempered with experience is the folly of youth. You do you as you see fit.

 

[RoninB4]

It's a 45 year old Chineese lathe, not expecting to build NASA parts on it.
Half the stuff I do +- 0.0625" is getting fussy.

-Then I wouldn't worry about a mismatch when re-installing the bed section. I should have asked about the accuracy of your work.

 

[dutchgray]

It's a 45 year old Chineese lathe, not expecting to build NASA parts on it.
Half the stuff I do +- 0.0625" is getting fussy.

I had a bearing fit to do at the weekend
40.002 mm min to 40.011 mm max
I didn't even use the compound set to a low angle, just did it with the cross slide dial and a 2 micron per division indicating micrometer set to a 40mm gauge block.
On a good but well used lathe built in 1957.

Even relatively "bad" machines can do accurate work if the operator knows how to make it do accurate work.

 

[Steve from Socal]

A couple of things about swing, first the chuck is only part of the issue. If you plan on anything but face work the saddle and compound come into play. The chuck may be able to swing a 12" part, the saddle may only allow a 6" shaft. If you do a lot of work with common size pins consider a collet chuck. As to 3 jaw chuck size I would agan suggest an 8" as a practical limit.

I have a 13" swing lathe and would never consider using a 10" chuck. The mass difference between even the most robust 8" and light tens are huge. I have three lathes and chucks ranging in size from 6" to 15" and the big jump in weight and heft is from 8-10. You might find a light 9" chuck from a South Bend or the like that could be the better choice if you really want to maximize capacity.

 

[rsanter]

You can buy a plain back chuck and then the plate or you can also buy chucks that have the threads in them

The advantage of the back plate is that you put the back plate on and dress it then mount the chuck. If you have an accident you can correct the chuck back to Center.

You can do light work in reverse. Some people have added set screws to the threaded area of the thread portion. That in addition to the natural resistance when threaded on and given a bit of tension

 

[rsanter]

And I should have a couple chucks I could part with

 

[Firebrick43]

You can buy a plain back chuck and then the plate or you can also buy chucks that have the threads in them

The advantage of the back plate is that you put the back plate on and dress it then mount the chuck. If you have an accident you can correct the chuck back to Center.

You can do light work in reverse. Some people have added set screws to the threaded area of the thread portion. That in addition to the natural resistance when threaded on and given a bit of tension

When you finish a blank back plate for a chuck you cut the spigot for the size on the back of the chuck, then it "should be" true and a snug fit. You can not correct it back in the future with a standard chuck or it will be loose on the spigot.

There are "set tru" chucks that have 4 set screws near the back edge of the chuck around the perimeter every 90 degrees. The spigot on these chucks is smaller than needed by .020" or so and the set screws are used to realign the chuck to be on center. Most scroll chucks are actually only on center in one specific clamping spot. Many production shops will clamp a part the correct diameter that will be used in the production run and set the chuck tru to center at that clamping diameter.

Its a very fine feature to have and can sort of replace a 4 jaw in many round clamping situations. It does add an inch or so to the length of the chuck and they are more expensive.

 

[RoninB4]

You can do light work in reverse. Some people have added set screws to the threaded area of the thread portion. That in addition to the natural resistance when threaded on and given a bit of tension

-Any set screws that make contact with the threaded portion should have either a small brass plug to contact with the threads or be the type of set screw that already has a brass/aluminum insert in the set screw. This is to avoid damage to the threads, they're available for purchase of you make them yourself. This is (or should be) common machine tool practice.

 

[larry_g]

A couple of things about swing, first the chuck is only part of the issue. If you plan on anything but face work the saddle and compound come into play. The chuck may be able to swing a 12" part, the saddle may only allow a 6" shaft. If you do a lot of work with common size pins consider a collet chuck. As to 3 jaw chuck size I would agan suggest an 8" as a practical limit.

I highlighted the above in red, This is important. If your just making pins and bushings then your probably not turning anything above 3-4" diameter. If I may suggest, if you only have one chuck make that a 4 jaw. It will teach you how to properly mount work and get it centered and straight. It also allows you grab irregular items and set them so you can accomplish what you want. 3 jaws are quick and handy for round stuff but your at the mercy of the chuck for centering if you don't want to do a bunch of packing and fiddling. Learn with a 4-jaw and you'll understand the limits of a 3-jaw.

lg
no neat sig line

 

[rsanter]

-Any set screws that make contact with the threaded portion should have either a small brass plug to contact with the threads or be the type of set screw that already has a brass/aluminum insert in the set screw. This is to avoid damage to the threads, they're available for purchase of you make them yourself. This is (or should be) common machine tool practice.

Yes this is true, a brass or aluminum slug is the best way as it will begin to conform to the threads and provide more contact surface for friction against moving. This is what I have done with my grizzly machine

 

[rsanter]

When you finish a blank back plate for a chuck you cut the spigot for the size on the back of the chuck, then it "should be" true and a snug fit. You can not correct it back in the future with a standard chuck or it will be loose on the spigot.

There are "set tru" chucks that have 4 set screws near the back edge of the chuck around the perimeter every 90 degrees. The spigot on these chucks is smaller than needed by .020" or so and the set screws are used to realign the chuck to be on center. Most scroll chucks are actually only on center in one specific clamping spot. Many production shops will clamp a part the correct diameter that will be used in the production run and set the chuck tru to center at that clamping diameter.

Its a very fine feature to have and can sort of replace a 4 jaw in many round clamping situations. It does add an inch or so to the length of the chuck and they are more expensive.

Yes you face the plate and the cut a step that will center in the back of the chuck.
If it needs corrected in the future then you will reface and turn the step again

 

[Nutria]

Picked up an 80s 13x40 lathe at auction.

It's missing the chuck and toolpost so looking at options.

Is a 10 or 12" chuck the right size to use?... ie should I use the biggest that'll fit?

Apparently these lathes use a backplate that threads, chuck bolts to it. That mean no "backward" work???? Chuck would unscrew?

Let's see a photo of your find!

 

[Sumboodie]

Let's see a photo of your find!

Haven't hauled it home yet, I'm at work till next week.