4 jaw chuck blues and Sanou review

[Makintrax73]

Thinking a 6" chuck would be a good choice I bought a Shars, and back plate. Decent chuck, not too expensive. But HEAVY at 24 lbs, and my 9" Logan slips the belt sometimes on startup.

Thought hey a lighter chuck might be nice sometimes. Bought a Skinner 6" junior on Ebay.....disaster. Lesson 1: Don't spend money on used chucks you can't inspect. Slots were worn beyond hope, and jaws were hopelessly bell mouthed.

For $60 figure I'll take a chance on a 5" Sanou. 6" down to 5" is 11 lbs lighter. A lot easier on the machine and to handle.



Being cheap....err I mean "frugal" I got some scrap 1/2 plate, and used that to adapt the junk Skinner adapter to the 5" Sanou. LOT of work machining a 5" disk of 1/2" on a 9" machine, but I got it running true, and drilled out with screw locators I machined.



So far so good. Seems to run true. Except....once you dial in work at the chuck it is running out .010" if you move 1" out away from the chuck....uh oh. Triple checked my back plate. Seemed good to .001" anyway.

To make an already long story as short as possible the Sanou chuck jaws were no where near parallel.

The worst of the 4 was .008" out of parallel from tip to tail. The others only perhaps. 002". They aren't all that hard either, which I guess is nice if you need to adjust them. So I loaded the jaws and cut them on the lathe with a carbide boring bar, then filed the peaks down off the machine.



This amazingly worked reasonably well. I now am out only .003" at 2" from the chuck face instead of .010" at 1" from the chuck face.



I'm sure there is a lesson here somewhere. If you have a couple true chucks thank your lucky stars? If you are a cheapskate you better have time on your hands to fix other people's mistakes? Don't buy other people's junk on Ebay, they are selling it for a reason?

Well anyway I probably type too much, hopefully someone gets a laugh out of my stupidity

Edit: Yes, I have yet to machine down the outer edge of the back plate to the size of the chuck, and countersink the back plate mounting bolts. I didn't want to waste time on it until I could get the chuck trued up.

 

[AlfromNH]

I'm on the hunt for a 4-jaw D1-4 chuck and hoping to be "frugal" also. I'll consider this a cautionary tale, thanks.

 

[Nesse1]

Wow! So you literally bored your chuck? Or, am I misunderstanding?

 

[Makintrax73]

Wow! So you literally bored your chuck? Or, am I misunderstanding?

Yes. I loaded the jaws 1 at a time by using steel blocks in between the "work" jaw and the 2 adjoining jaws. Then bored it with a brazed carbide boring bar .001" at a time until it was cutting all the way across the face of the jaw. Then move on to the next jaw until done. They were all marked, removed and filed the rough edge off as flat as possible going very slow.

Obviously this only works with independent jaws because it would ruin concentricity in a scroll chuck.

The jaws must not be terribly hard. I tested them first. Brazed carbide cut them like butter with light cuts. No chatter. When I saw how easy they cut I figure why bother with spreading grinding dust all over my lathe.

 

[RJSakowski]

Yes. I loaded the jaws 1 at a time by using steel blocks in between the "work" jaw and the 2 adjoining jaws. Then bored it with a brazed carbide boring bar .001" at a time until it was cutting all the way across the face of the jaw. Then move on to the next jaw until done. They were all marked, removed and filed the rough edge off as flat as possible going very slow.

Obviously this only works with independent jaws because it would ruin concentricity in a scroll chuck.

The jaws must not be terribly hard. I tested them first. Brazed carbide cut them like butter with light cuts. No chatter. When I saw how easy they cut I figure why bother with spreading grinding dust all over my lathe.

That's a better way to correct the jaws on a four jaw chuck than the approach that I used. I ground all four jaws at once so the worst case jaw determined how much material was removed. It worked OK though.https://www.hobby-machinist.com/threads/grinding-my-jaws.50747/

 

[G-ManBart]

Wow...looks like that one slipped through QC!

I put a San Ou 3-jaw on my Sheldon and it was .002" TIR....was pretty shocked at how good it was.

If you buy a San Ou chuck from CME Tools directly (they are the importer) or from their eBay store (niuniucme) they take returns. I read a lot on them before deciding to try one and the one or two people with issues said they didn't have problems getting a replacement. One I recall was a 4-jaw that had something wrong with the jaws and they essentially sent them a rebuild kit that fixed the issue if I remember correctly.

A lot of other companies sell the San Ou chucks, but they get them from CME...not sure how others might handle problems.

 

[G-ManBart]

Not that I want to make more work for you, but did you reverse the jaws and see if the other side was similarly off? I only thought of that because I was wondering if there would be a way to true up jaw faces on a surface grinder and that got me thinking about the other set of jaws.

 

[MrWhoopee]

I've been pretty impressed with the 6 in. Sanou 4-jaw that I bought. The jaws were consistently very tight in their slots, like two hands required on the chuck wrench tight. I lapped them all to a more reasonable but still snug fit. The jaws have a slight reverse bell-mouth, which I assume is to correct for the tendency to deflect when tightened.

 

[Makintrax73]

Not that I want to make more work for you, but did you reverse the jaws and see if the other side was similarly off? I only thought of that because I was wondering if there would be a way to true up jaw faces on a surface grinder and that got me thinking about the other set of jaws.

Not yet. Clearly need to check.

Mr Whoppee, I believe you are correct. I did note slight reverse bell mouth and the one that was way off was that say direction. Unfortunately it was so far off that defection wasn't going to work. So I figured I'd just cut them. Possibly should have only hit the bad one.