What do I need to know about chucks before buying a four-jaw?

[BaronJ]

Hi Guys,

Looks like a threaded onto the spindle backplate. Can't see the front of it to determine if it has a register. You could use the diameter of the backplate as a guide for the chuck diameter.

 

[Mauser lover]

Okay, short on time, so I'll just post the pics and come back when I can...

Is it polite to post the whole picture, or am I supposed to do thumbnails? I did full pics this time... And why did some of them double and not all of them?!? Oh well...

 

[DAT510]

From the pictures it does appear to be a screw on face plate. Below are the instructions for the Grizzly G9246 lathe which appears to be similar to yours... the full manual can be found here: https://www.hobby-machinist.com/resources/categories/jet-except-grinders.636/

As it is not the exact manual for your lathe, please use caution, as the instructions may not be correct for your lathe, and are presented as potential guidance for removing your face plate.

Btw, Grizzly manual shows spindle clamps that need to be removed....On many of the earlier lathes like my Jet 1024, there were no spindle clamps.

Hope this helped.

 

[BaronJ]

Hi Guys,

Yes it does look like a screw on back plate and a six inch chuck.
I would reassemble your chuck and unscrew the whole lot. I hope you marked the position of which stud went where.

Then you need to find the right back plate for your spindle. I would buy one that is suitably machined so that it will just screw straight on.
After that you will need to get the chuck that you want that is the right size.
Your existing back plate is for a six inch chuck. If you are buying a four jaw you might want to go to eight inch, so you would need an eight inch back plate.

I'll leave it at that for now because there is more to be done.

 

[Mauser lover]

So... It seems that I've got three options...

1. Get a chuck that threads directly to my spindle.
2. Get a chuck that fits onto my existing backplate (maybe a bad idea, maybe impossible?)
3. Get a chuck with separate backplate that threads onto my spindle.

With options one and three, it doesn't matter if I am getting a plain back or a D1-4 or whatever other style, right? I just have to get the right thread size?

Option two, all I need to do is get a chuck that fits a "plain back" backplate? (Assuming it is the same diameter, which looks to be 6.5 inches? Is that a 6 inch chuck if it is 6.5 inches diameter?)

Bad ideas? Which one is best? Which one is cheapest? I was actually looking at getting an eight or ten inch chuck already, so I'm guessing option two is already out.

Thanks for the help.

 

[mikey]

You have a threaded spindle so forget camlock chucks or any other kind of chuck. The only thing that will fit is either a chuck with an internal thread that matches your spindle or a back plate that is threaded to match your spindle. Along with the thread is the register, a shoulder or taper that the chuck or back plate must also match. The thread only allows the chuck or plate to spin on. What holds it concentric to the spindle is the register. The register is a physical feature of your spindle, behind the threaded section.

So, take the existing back plate off your lathe and measure the spindle thread. You need the OD and the thread per inch so you can identify the spindle thread. Once you know that, you need to figure out what spindle standard it fits. If that is an asian lathe then it is likely that it is a DIN standard. This standard will specify both the spindle size, threads per inch and the size of the register. Once you sort out that DIN standard then you can search for a chuck that will fit that standard.

Your options are to find a chuck threaded to the DIN standards of your spindle or you can try to find a back plate that fits your spindle and mount a plain back chuck to it.

 

[BaronJ]

Hi Guys,

I suspect Mauser will have a hard time finding a chuck with a threaded back (Narrow Body Chuck) to fit his spindle !

As far as buying a bigger chuck is concerned, as long as the jaws when stuck out don't hit the bed thats fine. Even so I wouldn't fit a chuck any bigger than the one that the manufacturer would have supplied with the lathe, particularly with a screw spindle.

 

[mikey]

Hi Guys,

I suspect Mauser will have a hard time finding a chuck with a threaded back (Narrow Body Chuck) to fit his spindle !

As far as buying a bigger chuck is concerned, as long as the jaws when stuck out don't hit the bed thats fine. Even so I wouldn't fit a chuck any bigger than the one that the manufacturer would have supplied with the lathe, particularly with a screw spindle.

Agreed. I would think an 8" chuck would be about the max, and even at that I suspect 90% of the work that can be done on a 12" lathe could be done with a 6" chuck. It isn't just about what the swing will fit; it is also about what the spindle bearings were designed to handle.

 

[Mauser lover]

Agreed. I would think an 8" chuck would be about the max, and even at that I suspect 90% of the work that can be done on a 12" lathe could be done with a 6" chuck. It isn't just about what the swing will fit; it is also about what the spindle bearings were designed to handle.

How dare you?! Talking me into cheaper tools!? I came here because I thought everyone here was in the business (or hobby) of talking everyone into more expensive tools!

Really though... Thanks for that suggestion on the sizing, and the help so far with all my questions. It seems that these size lathes generally ship with a six inch three-jaw and an eight inch four-jaw and a twelve inch faceplate (as far as tooling for holding workpieces go). I only got this six (ish) inch three-jaw when I purchase it, but I'd guess that it should be able to handle an eight inch four-jaw chuck.

I'm going to be short of time for the next couple of months, but I'll try to pull that backplate off this weekend and have a look at the spindle and see whats going on back there...

 

[BaronJ]

If you have a good look at your faceplate you will be able to get all the information you need for a backplate. There is no difference apart from size.