Wandering runout

[Garwood]

I have a 16" Schunk chuck on one of my machines. It's a weird chuck. Quick change jaws are handy, but I like the Kitagawa style better.

What size/hole/back chuck are you needing? I have spares.

 

[mach ramsey mn]

Yeah, I’d be going for what bolts up and will work with the existing draw tube, actuators assembly. Sucks there’s no easy fix for this…

 

[Spruewell]

It's a 10" chuck on an A2-8 spindle nose. 96mm spindle bore, 76mm ID on the draw tube and 85mmx2 thread. I do like the versatility of the serrated master jaws. I'm leaning towards buying new, but I (like everyone) don't want to spend a fortune.

 

[mach ramsey mn]

Fortunately (or unfortunately) when I had to replace a chuck it was an assembly replacement, actuator, draw tube, chuck. I’d call my SMW guy and they would come and take care of it. Worth every penny.

 

[Herding Cats]

It's been a while since I had a power chuck apart. Is there enough material in the chuck body to bore it out, press in a thin sleeve and rebore?

Even some pre-hard 4150 would buy you some time, especially if you kept it well lubed.

 

[Garwood]

I'm thinking like Kustomizer... Put something in there to keep the guts preloaded, even if it's preloaded to one side. Like drill a hole and install a ball bearing with a die spring behind it and a set screw or pipe plug to keep it in.

Might be worth a shot before tossing it.

 

[Jashley73]

Are we sure this isn't a case of the jaws being bored with too-large a radius insert, and the part's stock having sharp corners from being saw-cut...? In other words, the part's sharp corner trying to sit against the chuck jaws' corner radius, and therefore, will never sit correctly in the jaws...?

Do your second-op parts repeat better, with less runout?

If I understand this correctly, the power-chuck's central cam having a little clearance inside the chuck's body, shouldn't be too big of a deal. The cam pulling on the jaw carriers needs to be fairly snug. But all of those clearances should nearly-equalize when loaded/clamped.

 

[Spruewell]

I think this thing is done for. After talking to a couple places that rebuild chucks, it sounds like the cost will rival or exceed that of a new one

 

[Spruewell]

Are we sure this isn't a case of the jaws being bored with too-large a radius insert, and the part's stock having sharp corners from being saw-cut...? In other words, the part's sharp corner trying to sit against the chuck jaws' corner radius, and therefore, will never sit correctly in the jaws...?

Do your second-op parts repeat better, with less runout?

If I understand this correctly, the power-chuck's central cam having a little clearance inside the chuck's body, shouldn't be too big of a deal. The cam pulling on the jaw carriers needs to be fairly snug. But all of those clearances should nearly-equalize when loaded/clamped.

The runout is showing up on the portion of the jaws that is bored through and is clamping on a cylindrical surface. It is not running up against a step where issues with a rough cut or burr will affect it.

 

[Mud]

Is MMK/Matsumoto still available? I have one on an old Cincinnati that has been faultless. Looks a lot like a Kitagawa, takes the same jaws.

 

[Garwood]

Howa is another name I've seen a lot and struck me as quality.

 

[yardbird]

Them jaws look like they go on a size bigger chuck. Outside bolts hanging almost off. I bet they flex a pretty good bit.

 

[lobust]

Them jaws look like they go on a size bigger chuck. Outside bolts hanging almost off. I bet they flex a pretty good bit.

Good catch, I didn't pay attention to that at first glance - those jaws are definitely too big for that chuck, top jaws generally are the same width as the masters. Is the slot even the right width?

 

[Spruewell]

I made the jaws. I had some 1045 2-1/4" square stock I cut them out of and didn't bother making them narrow to match the master. They are a good tight fit to the chuck and the nut is entirely within the master. Didn't occur to me that jaws could be too wide. Pie jaws are much wider and nobody seems to be bothered by that.

 

[Mud]

How did you cut the serrations? I've wanted to do that myself.

 

[Vancbiker]

How did you cut the serrations? I've wanted to do that myself.

Back in the olden days before cheapish jaws were widely available, the place I worked at made our own for the 3 lathes we had. all were 12” MMK chucks. For serrations we had a half dozen or so V cutters surface ground so that when stacked on an arbor for the manual horizontal mill they were on the correct pitch x4-5 (don’t remember exactly). The jaws themselves started as 30ish” long CRS bar. We cut the slots and drilled them on a VMC then the went to a gang drill press (solely for the large table) to c’bore the holes (good trainee job). Then they went to the horizontal for serrations. Each pass cut 6 serrations. move Y one pitch and make another pass and so on until all cut. Final op was the bandsaw to cut them into individuals. At first we’d cut a bit long and face the edges. After a batch or two realized that the saw cut edges were fine and eliminated the facing.

 

[Herding Cats]

I use a 1" ID threading bar in a 1" weldon ct40 holder. Not very fast but when I need to make some jaws I just let an old machine chug away while I'm doing something productive.

All the Kitagawas I have are 60 degree 1.5mm pitch

 

[Spruewell]

I square off the ends, then stand it up in a vise. Put a threading bar in a toolholder and use it like a single point thread mill. The program calls a subroutine to step down your desired pitch, feed the tool one way, incrementally step down again, and feed back. Loop the sub according to how many serrations you need. It's not super fast, but it works. If you had a thread mill with multiple teeth, it would be much faster. After that, I set up to do the slot and holes. I'll often relieve the end of serrations to clear the center of the chuck.

 

[Herding Cats]

If I made more jaws I would invest into a large indexable threadmill with 1.5mm pitch multi tooth inserts.

 

[dsj]

How did you cut the serrations? I've wanted to do that myself.

I've only had to make one set but I used a 60deg chamfer mill. Worked just fine. The jaws were 6061 so I didn't have any issue with knocking the tip of the tool off. YMMV in steel.