lathe chuck problem

[welderskelter]

I have an old Advance lathe. I have a 3 jaw approximately 8 in. chuck that screws on to it very easily. I tried to put a 14in. 4 jaw on it and it lacks about a 1/4in. of going on all the way. They look to be the same thread and they both came with the lathe when I got it. Could there be 2 different size threads so close that they would screw on that far?Harold

[old mart]

Being a threaded spindle, I would guess that the chucks are fitted to backplates. Take the backplate off of the offending chuck and try the fit, it will be easier to diagnose the problem.

[BCRider]

First off check the obvious things. Does the 4 jaw plate have sharp and burred thread peaks on the minor ID? Is there any obvious burr from something? A chip jammed and pressure glued to a spot in the point of the V's major ID at some spot?

Or what about the cylindrical register? Is it possible that the bored out register on the first part of the 4 jaw backplate is a touch snug on the spindle's matching register area? If so that'll bind things up neatly.

When making up threaded parts to fit some other part I've noticed that when I get REALLY close that I can thread the parts together for turn or three. But things get slowly tighter until they wedge together much like an Morse Taper but with a twist.... This is likely from any number of things. But it even happens when both items were single pointed on my own lathe. So it can occur even when you know the pitch is an EXACT match.

The "cure" is to take another light pass or two depending on the factors which clears away this binding. And it's not like the threads at that point are all wobbly. Even the first couple of turns are pretty close... on occasion and probably mostly by accident.... It's just that there was something.

This might be the case with your backplate. It might have been threaded a touch small. If so and it's not one of the other issues mentioned so far then you'll need to mount and true up the plate and pick up the thread and clean a whisker out of the threading.

[oxford]

Being a threaded spindle, I would guess that the chucks are fitted to backplates. Take the backplate off of the offending chuck and try the fit, it will be easier to diagnose the problem.

I would try this.

[redgrouse]

You probably already know about this but look here http://www.lathes.co.uk/advance/
Assuming you intend to keep the lathe longish term I would make a couple of gauges for the manufacture of extra backplates etc etc. One for the thread and another for the register, make this dead size to your machine and add a step at the front 0.001” less for say 0.100” long, use three wires to measure your spindle and replicate on the thread gauge.
John
PS if you have an accurate bore gauge the plug gauge will not be needed.

[NiftyNev]

I don't think he has the Advance lathe linked to in previous post. A 14" chuck would not be suitable.

https://bbs.homeshopmachinist.net/fo...-advance-lathe

[welderskelter]

Why cant this lathe handle a 14in. chuck? And yes it is the Advance lathe .

[welderskelter]

BCRider you say to turn the chuck threads again right? How am I supposed to chuck it up to the smaller 3 jaw? Can I use the 4 jaws to clamp on to my three jaw?

[The Metal Butcher]

BCRider you say to turn the chuck threads again right? How am I supposed to chuck it up to the smaller 3 jaw? Can I use the 4 jaws to clamp on to my three jaw?

Unconventional, but yes, that will work.

[oxford]

BCRider you say to turn the chuck threads again right? How am I supposed to chuck it up to the smaller 3 jaw? Can I use the 4 jaws to clamp on to my three jaw?

Before you get to this, when you thread the chuck on and it stops, does it feel like it hits something “hard” or does it feel like it’s binding up and could go more if you cranked on it?

[welderskelter]

Yeah it will be a trick. Now if the weather will warm up. I am out of wood for the shop and dont want to tear up the muddy trails to get any. Always a deli ma. Thanks

[welderskelter]

Its not hitting hard. But the farther I go the tighter it gets.

[JRouche]

Being a threaded spindle, I would guess that the chucks are fitted to backplates. Take the backplate off of the offending chuck and try the fit, it will be easier to diagnose the problem.

Thats the ticket. My SB lathe had a threaded chuck mounting issue. I separated the two and I forget if it was a burr or some swarf causing it to hang up.. Works fine now. Good idea.. JR

[NiftyNev]

Why cant this lathe handle a 14in. chuck? And yes it is the Advance lathe .

It probably can, but not the Advance that was linked to on the lathes.uk site. It can only swing 8 3/4" in the gap.

[Richard P Wilson]

I think we've discussed this in a previous thread. Its unlikely that the Advance company in Australia, known to produce quite good quality small lathes made this much larger machine which has surfaced in the US.