Looking to replace my 4 jaw chuck on my BD-920N lathe

better-lathe-than-never

better-lathe-than-never

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My current 4 jaw chuck is sloppy mess and difficult to adjust accurately. It's hard enough for a rookie to try to work a 4 jaw chuck - but this clunky beast I have is downright infuriating.

So just like the title says I started looking around for a new 4 jaw chuck that would take some frustration away and would make this job easier. Trouble is that none of the chucks I've seen look like they would fit the spindle of my machine. I believe my machine has an externally threaded nose spindle: 1.5in at 8tpi.

Q1: is there some kind of adapter I need to get to mount a replacement chuck?

Q2: Current clunker is approx. 7 1/2'' in diameter, maybe they call this an 8'' chuck - I don't know. What is a size of a chuck that I should I be looking at so that I don't overload the bearings on my machine - is there a weight limit or size limit to watch when buying? Can this machine handle an 8'' chuck plus an adapter?

Q3: With a budget of about $200-300 what are some name brands to look for? I fancy a Bison chuck - made in Poland, but think these are gonna be outside of my price range.
 

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I think your spindle is a very common size. You should be able to get back plates for it. You can then machine the BP to fit most any chuck. Easiest though would be to just buy a chuck made to fit that spindle as a one piece item. I've got a Chinese 8" 4 jaw that came with my lathe works OK. No more than I use it, I'll likely never replace it. Having two chuck keys makes adjusting a 4 jaw a bit easier. Make a couple with handles short enough to clear the head stock Move in all jaws gently so the work can slide a bit. Don't tighten any until all are in final position. Then use your regular key to do final. Watch the videos that demo. Don't assume you will match Abom any time soon.

I did replace my 6" 3 jaw with an 8" Taiwan made, very nice! I had to machine a cast iron BP for it. It is a lot heavier than the integral mounting ones. I made a wooden cradle, with handles, that fits the lathe. (chuck is coated with T-9 & stored on the cradle) For smaller diameter work I use an ER40 that I finally managed to get trued up (Chinese!) For work that has very little to get into the chuck, I've got a 5C.

This is a very DEEP rabbit hole!
 
My 9x20 came used with a 4”jw, 5 1/5” 3jw and a 6” 4jw. 6” is the absolute max because of jaw clearance. All my chucks are Chinese and have no problem. The original owner got rid of the original 4jw junker luckily for me.
 
The BD-920 is almost identical to my Grizzly G1550, except the paint color. The OEM 4 jaw chuck might be OK for a wood lathe but is about useless for metal work. Maybe light weight brass or aluminium, but certainly not steel. The spindle nose is threaded 1-1/2 x 8. A possible alternative is on newer machines, 39 x 4 mm is used. The 39x4 is very close, measure the thread carefully.

Grizzly (https://www.grizzly.com/?gclid=EAIaIQobChMIqK6oifvF4QIV-yCtBh1-HA69EAAYASAAEgJgzPD_BwE) stocks 1-1/2x8 back plates. Or did, last time I looked. They also have low end Asian chucks and 39x4mm back plates. Most 4 jaw chucks require purchasing the back plate seperately. There are better chucks available, usually at a higher cost. Not as important as self centering, but still important.

Screw on chucks are an older technology. Seldom used on modern machines, they do show up regularly on older machines. I found a Craftsman /Atlas 4 jaw, a 7 inch, on eBay. With the backing plate installed. But it's something that has to be watched for, they don't show up often. For my small work, I also have a 2-1/2 inch from an old UniMat that has been mounted on a MT3 spindle. That gets most of my work, the 7 inch is there just in case something big comes along.

There is also a face plate with the small machines. Hang on to the OEM 4 jaw, if nothing more than as a face plate. It will need truing likely, but will be handy when it comes to drilling holes.

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Might be a little small for an anchor, in fast water. . .

The spindle nose is 1-1/2 x 8, not 2-1/4.
 
@DavidR8 - they would ship it but it would be $190 + $150 in shipping/border charges... tempting, but a bit too much. It's really tempting, so I'll have to think hard about it.

What's the advantage of a two-piece jaw - that was an option on the Bison chuck?
 
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