What size of 4-jaw independent chuck on a 12”x36” lathe?

[jlficken]

It looks like I’m going to have to have a back plate made for my lathe since it’s a weird 55mm spindle size so I’m trying to decide what size of chuck to get.

I have a 6.25” 3-jaw on there now but want a 4-jaw independent jaw as well. The question is 6” or 8”?

I’m tempted to go 8”, however, it weighs substantially more than the 6” and I’m not sure if my 1HP lathe is really meant for an 8” chuck.

ETA: On a side note I now know the difference between a threaded backing plate and a blank. The blanks have a 3” hub while something threaded in 1-1/2” x 8 that I could have threaded M55 only had a 2-5/8” hub. The hubs on my existing plates are 2-3/4” so pre-threaded won’t work.

 

[MyLilMule]

Either would work, but it often depends more on the kind of work you are doing. I find that the smaller chucks will grip smaller diameter material than the larger ones. And if I have to reverse the jaws for a larger piece, the larger one might be a better option. I have 6", 8" and 10" chucks for my 13" lathe.

 

[mmcmdl]

8" . The 4 jaw is usually bigger than the 3 jaw but is lighter . Most 4 jaws are webbed making them light .

 

[jlficken]

8" . The 4 jaw is usually bigger than the 3 jaw but is lighter . Most 4 jaws are webbed making them light .

I hadn’t thought about the independent chucks being lighter.

I’m still working on finding someone to thread the back plates for me. I can take it from there but I’m just not set up to thread them.

The 8” blanks are spendy at $120 each though compared to the pre-threaded at $50 each which sucks.

 

[jlficken]

The spindle threads are definitely M55 x 8TPI as I was able to compare 8TPI to 3.0 now that my thread gauges arrived and the 8TPI fits perfectly.

 

[WobblyHand]

You could make your own back plate. I made mine from raw cast iron. In a way it was easier than finishing a back plate, since I controlled the whole process. I had to, since it was the height of the pandemic and I couldn't source one. So I bought a slice of cast iron and turned it into a set true back plate. Mine had 8 TPI threads that I single pointed.

However, if you can find something close that has enough meat to it, that's where I'd start. It certainly would be cheaper.

 

[GeneT45]

**At least** 8 in. I'd go for 10" on a 12" lathe. 1HP is mighty puny for a lathe that size, what is it? I'd still go for the larger chuck. It may take a moment to spin up, but inertia will only improve your cut.

GsT

 

[Ischgl99]

I have that size lathe and have an 8” 4 jaw. I would like to get a 6” as well, but would not want to be without the 8” capacity and would recommend that first unless you know you won’t be needing it for anything larger than 6”. I haven’t weighed them, but the 8” 4 jaw is about the same weight as my 6” 3 jaw.

 

[jlficken]

It’s a Buffalo Power BP-1236.

 

[jlficken]

I have that size lathe and have an 8” 4 jaw. I would like to get a 6” as well, but would not want to be without the 8” capacity and would recommend that first unless you know you won’t be needing it for anything larger than 6”. I haven’t weighed them, but the 8” 4 jaw is about the same weight as my 6” 3 jaw.

I’m thinking 8” too so that I could at least possibly try making my own back plates some day.