3 jaw scroll that I don't know how to adjust vs independent 4 jaw backing plate

[Aukai]

My D1-4 chucks need to be changed over to D1-6. I have an 8" 3 jaw PB 3 jaw scroll self centering(Mount to a lathe's spindle to hold round workpieces. Also known as scroll chucks, these are self centering—all three jaws move in unison, centering the workpiece as they close) and an 8" Pratt independent 4 jaw. When looking I can find machined backing plates to adapt self centering, but don't know what the difference would be for the 4 jaw.

 

[benmychree]

There should be no difference, only size matters.

 

[mmcmdl]

Got pics ? And what are you going to do with the left over D1-4s ? We'll make a swap !

 

[Aukai]

Thank you John, Dave I need 2 6" D1-6 backing plates also. I need/want to change over 4 total.

 

[mmcmdl]

I don't have any D1-6s Mike , only one I have is on the 14" lathe . I'm looking for D1-4s for the 13" . I have a few chucks I want to mount down the basement . Once you find those 6s , let me know what you're doing with the 4s .

 

[mksj]

Different animals, a self centering scroll set-tru (set true) type is used to get the scroll jaws centered, not to center the stock. Once you adjust a set-tru chuck you do not readjust for each work piece. The typical TIR spec. is that they will repeat to 0.0004", but depends on the chuck manufacturer and size of the chuck. A standard scroll chuck the typical spec. is around 0.002". Scroll chucks are much quicker to get stock in and out, then an independent. An independent is more often used if you need to zero out the TIR, turning rough/irregular stock, you need to align the bore/hole in stock, or just dealing with square stock or a rectangular piece. I use a PBA 3J scroll Setrite chuck when I am doing multiple ops on the same piece and it may be in/out of the chuck 8-10X. When dialed in it repeats with a high level of repeatability. This also applies to my Bison 5C Set-Tru chuck. I use a 4J independent chuck for rough stock/ turning resulting in a lot of chips/swarf as it is easier to dissemble to clean, also for off center holes.

Your lathe comes with a Taiwanese 3J scroll (not set-tru) and a 4J independent so you may want to see if you can sell some of your older chucks. D1-6 back plates for mainstream chucks manufacturers can be expensive. A number of vendors sell extra thick semi-finished back plates than can de turned down into a configuration for a particular chuck. I have also used Gator back plates which seem to be a bit less then Bison/TMX brands. A 4J independent would use a standard back plate which is less expensive then a set-tru type..

 

[Aukai]

Thanks Mark, I am a little heavy on D1-4 6" chucks for some reason I am also looking for a D1-6 backing plate for my ER 40 chuck. This was one of the reasons I was dragging my feet on getting a bigger lathe spindle, but I jumped in, now it's sink or swim

 

[mmcmdl]

Lets set the record straight on self centering chucks !

 

[mksj]

There are very few back plate options in a D1-6 for a 5" chuck, let alone you also need for a set-tru type. I have only seen two that would fit an ER-40 type chuck. One is offered by Shar's which has been out of stock for months, so a waiting game and you might email them to see time frame. The other is a TMX/Bison back plate, unfortunately it is 2X the cost of the ER-40 chuck. Specifications appear to fit the Shar's ER-40 ero set chuck

5" ER40 Zero Set Fine Adjustment Collet Chuck

www.shars.com

5" D1-6 Threaded Black Plate for ER40 Zero Set Adjustment Collet Chuck

www.shars.com

3-875-056P - Back plate for SET-TRU™, 5in D1-6 - Toolmex Industrial Solutions

3-875-056P Back plate for SET-TRU™, 5in D1-6, Toolmex Industrial Solutions

www.toolmex.com

TMX Set Tru D1-6 Adapter Plate 3-875-056P for 5" Chucks

TMX Set Tru D1-6 Adapter Plate 3-875-056P for 5" Chucks

www.smalltools.com

Bison Set Tru D1-6 Adapter Plate 7-875-056 for 5" Chucks

Bison Set Tru D1-6 Adapter Plate 7-875-056 for 5" Chucks

www.smalltools.com

5" BISON D1-6 Back Plate for SET-TRU Bison Chucks 7-875-056

I would check with Small Tools and also Ajax Industries, as Gator often has the same type/size chucks/back plates, that latter being quite a bit less than Bison/TMX. I use used several of the Gator back plates and they have been very nicely made. Grizzly did have some semi-finished D1-6 back plates that might be machined to fit.

In general, a self centering chuck is a scroll chuck, meaning it will hold stock on center within it scroll range. A Set-Tru (Setrite, Zero Set, etc.) just allows one to dial down the on center position/run out for a particular chuck. The adjustment is indicated below, but takes a bit of tweaking to get it right, typically this is to get the clamping center to a minimum using a accurately ground stock test bay.

 

[Aukai]

That was a lot of research, thank you.