4 Jaw Self Centering Chuck Question

[Tool-in-the-Box]

I recently got a Rohm chuck in a bulk buy that looks new and seems to be a fairly current model. I am sure there expensive and accurate so I am planning on keeping it. My question is I have never seen a 4 jaw self centering chuck except for the really old ones. Should it be mounted to a lathe or is it better served for a fixture? It did not come with a back plate so I could do either. Also, what are the pros and cons of this type of chuck? Oh, and the jaws are the type that you can Allen key off and reverse real quick. It's a real sweet looking chuck, I'll try to post a pic later, I have it apart because the grease dried up inside. I think it was bought and just sat in storage unused for a long time. Thanks in advance. -J

 

[Rex Walters]

Dan Gelbart recommends a 4-jaw self-centering chuck (see:

around the 7’29” mark) — I just binge-watched everything he had to say about anything. Twice. Fascinating guy. He points out that even hex stock can be held in a four-jaw scroll chuck without runout (weird, counter-intuitive, and hurts my brain to think about, but apparently true).

 

[atunguyd]

The 4 jaw doesn't interest me all that much but that laser center finder was pure brilliance. I am definitely building myself one of those

 

[Rex Walters]

Off topic, but that 4-jaw scroll chuck holding hex stock concept was going to keep me up all night unless I drew it out. I finally realized that the square is inscribed in the hexagon, not circumscribed. The four points of the jaws all bite on a flat surface of the hex stock, not on any of the apex points:

 

[Tool-in-the-Box]

Interesting video, thanks.

 

[kingmt01]

It can't hold a triangle on center.

It has more points of contact as long as your round stock is pretty true. I wouldn't grab a big heavy chunk that hadn't been turned holding it by its end & spin it really fast. I've never used one but they are usually very expensive. Is love to have one to see if I like it. If you hold square stock it would be really nice.

 

[springer]

I bought a gator 4-jaw scroll chuck for my last lathe and I loved it. Held better tolerance than my old 3-jaw scroll and was pretty repeatable. Of course and independent jaw is for perfect accuracy, but most of the time that scroll stayed on my lathe. Wish I would have kept it instead of selling it with the lathe cuz it took a while to convince myself to spend the money on it. I miss it pretty bad so maybe I'll get another when my pm1236 gets here.

 

[george wilson]

I have kept Bison 8" 4 jaw chucks on my lathes for years. They can hold square as well as round stock as well as hex. It is probably true that 4 jaws hold less securely than 3,since 6 jaws hold even less securely,but I haven't had a problem with mine slipping.

I had a 10 hp 19" swing lathe at work,and used the same 8" Bisons on it as well,making heavy things like large axles for coaches and wagons in the museum. Took some pretty heavy cuts on them,too. No trouble with slipping.

A tip: If you have trouble with slipping in a chuck or a milling vise,put brown paper slips in the jaws. Paper holds like crazy if it has no clay in it. This works great for smooth jawed vises like Kurt vises.

 

[darkzero]

4-jaw scroll chucks (self centering) are still produced). The only advantage I see with a 4-jaw scroll chuck is if you work with square stock often with the ability to still hold round stock. As noted it can't hold hex stock. It will also hold thin walled work with less deformation than a 3-jaw but not as great as a 6-jaw. It can't hold rectangle though.

I don't work with square stock often so I opted for a 4-jaw independent for the accuracy. I use a 6-jaw the most, with a 4-jaw independent second, & 3-jaw coming in third.

There are also 4-jaw combination chucks that function both as a scroll chuck & independent. Awesome chucks but not useful enough for to justify the high cost.

 

[GarageGuy]

The 4 jaw doesn't interest me all that much but that laser center finder was pure brilliance. I am definitely building myself one of those

You know it. That thing is incredible. I wish I could see some close-up photos of it so I could try to build my own too.

GG