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Need Vicmarc pin jaw advice

Kalia Kliban

Kalia Kliban

Joined
Feb 16, 2012
Messages
196
Likes
906
Location
Sebastopol, California
The 35mm pin jaws for my Vicmarc 100 chuck are out of whack by about 1mm. It's hard to tell what caused it, and whether it's just a single jaw that's off or if all 4 have gotten tweaked somehow. I do very delicate work with these jaws so am not sure how this happened, but I really need accuracy when I'm using them. The amount of wobble I've got now isn't acceptable. Is this a fixable problem or do I just need to spring for a new set of jaws?
Kalia
 
I picked up a set of Vic pin jaws at an estate sale, and they had seen better days. I did eventually get fed up and re-trued them.
If I remember, I found something (probably a scrap of wood) to clamp in the gap between the jaws so they'd be secure at the right diameter opening. Or maybe I clamped them around a drill bit or a dowel or something like that. But had them clamped on something so they are secure and stable.
Then I ran a drill down the middle, and touched up the outside dovetail with a turning tool (probably a carbide tool, but might have used one of my M42 gouges a bit).
 
I have had the same problem with my vicmarc chuck. In my case, I found that simply loosening the screws and tightening them about a round cylinder did not solve the problem. One needs to insure that the center of the cylinder is aligned with the spin axis of the lathe. If you have a Oneway or other live center that has a half-inch threaded snout, just clamp the jaws snuggly around the snout and tighten the set screws. Otherwise, turn a short cylinder between centers to fit in the pin jaws. With the set screws slightly loosed, bring up the tailstock to engage the dimple in the outer end of the cylinder and tighten the set screws. It may help to wind a rubber band around the loosened jaws to keep them snugly in place while your tighten the screws.
 
Mine work perfectly. When you install.the jaws leave.all.the screws just a hair loose. Then close the jaws all the way and then snug the screws up. If you really need precision use collects. Bealle.sells.a.good.collet chuck. Pennstateind also sells.one but i dont know about the quality. I use #2morse taper collets and a home made draw bar. You can get the collets from machine shop companies very inexpensively.
 
Re-truing suggestions much appreciated. I'll break the chuck down today, give it a thorough cleaning and see if I can get those jaws back into line. I did send an email to Vicmarc to ask for their suggestions as well. Will post the results here.
 
Although my chuck is now much cleaner than it was a couple of hours ago, I wasn't able to eliminate the wobble. I tried closing the jaws around a 1/4" drill bit held in a Jacobs chuck in my tailstock and then tightening the screws, but no dice. I've got a replacement set of jaws on the way in case I can't get these fixed before they arrive. And of course there's time pressure since I'm getting ready for a demo that uses them...
 
I don’t have a VM100, but I do own VM120 and VM150. My jaws and jaw slides are numbered. Are they numbered on the VM100 and on your 35mm pin jaws? I know it’s a dumb question but if they are numbered, are they all in the jaws all matched up? Other than alignment tweaking, all things being equal, I can’t imagine why your run out increased. Perhaps, your chucks jaw slides got damaged?

I have a similar problem with my 20 year old one way talon and 25mm pin jaws. They will not automatically hold a dowel straight without the help of the tailstock. There is too much play in the jaw slides. I can not rely on it to rechuck a piece that was previously trued. I still use it a lot with its inaccuracies for small stuff that gets trued up unique to the piece that I am turning. After all, most woodturning chucks were not designed with the tight tolerances that are required to hold piece true. For those instances, a Collet chuck or a jacobs chuck.


So I echo @john lucas recommendations.
 
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I don't own that model of chuck, but I'm wondering if the problem might be with the slides (or chuck) rather than the jaws. Do you have any other vicmarc jaws you can try on that chuck?
 
The pin jaws that I have for my OneWay chuck have bent due to over tightening so if that is your problem then the best solution is a new set of jaws. The way to tell if the jaws are bent would be to clamp a drill bit or other precision steel rod into the jaws, then if all jaws are clamping at the inner base of the jaws check for clearance on the outer ends.
 
Dennis Weiner said:
I don’t have a VM100, but I do own VM120 and VM150. My jaws and jaw slides are numbered. Are they numbered on the VM100 and on your 35mm pin jaws? I know it’s a dumb question but if they are numbered, are they all in the jaws all matched up? Other than alignment tweaking, all things being equal, I can’t imagine why your run out increased. Perhaps, your chucks jaw slides got damaged?

I have a similar problem with my 20 year old one way talon and 25mm pin jaws. They will not automatically hold a dowel straight without the help of the tailstock. There is too much play in the jaw slides. I can not rely on it to rechuck a piece that was previously trued. I still use it a lot with its inaccuracies for small stuff that gets trued up unique to the piece that I am turning. After all, most woodturning chucks were not designed with the tight tolerances that are required to hold piece true. For those instances, a Collet chuck or a jacobs chuck.


So I echo @john lucas recommendations.
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Everything is absolutely in its correct place. I even engraved the slide numbers on the chuck body so that when I disassemble it it all goes back together the same way. I do plan to try moving the jaws to a different chuck body to see if it's a slide issue, though when I removed the jaws before I took the chuck apart for cleaning, I looked to make sure the slides came together cleanly (they did). I did notice a ding on one of the jaws up at the tip. I don't remember how or when it happened, but if it was while the lathe was running it could have knocked the jaws just that crucial little bit askew. I've got another set of jaws on the way from Packard, so one way or another I should have the problem fixed in a few days.
 
Kalia Kliban said:
Although my chuck is now much cleaner than it was a couple of hours ago, I wasn't able to eliminate the wobble. I tried closing the jaws around a 1/4" drill bit held in a Jacobs chuck in my tailstock and then tightening the screws, but no dice. I've got a replacement set of jaws on the way in case I can't get these fixed before they arrive. And of course there's time pressure since I'm getting ready for a demo that uses them...
Click to expand...
Are you sure that the Jacobs chuck is dead center with the headstock? It is not something one would ordinarily check.
 
By the way, the screws and the sockets in the jaws are tapered. Therefore, it is important when installing the screws with the chuck holding a centered cylinder of some kind, to tighten the screws gradually in sequence. This allows the screws to strike a compromise in position as needed.
 
The mating surface on the jaws have a circular tongue that fits into a mating groove in the slides therefore no matter what you do to align the jaws they will go back to the original alignment. I just went out to my shop and using a machinist square I checked the pin jaws for my Strong hold chuck and they all are out of square. The track that the slides ride in may also have wear that could add to the problem since when the jaws are tightened they will tip toward the outside.
 
Don Wattenhofer said:
The mating surface on the jaws have a circular tongue that fits into a mating groove in the slides therefore no matter what you do to align the jaws they will go back to the original alignment. I just went out to my shop and using a machinist square I checked the pin jaws for my Strong hold chuck and they all are out of square. The track that the slides ride in may also have wear that could add to the problem since when the jaws are tightened they will tip toward the outside.
Click to expand...
Don, My talon 25mm pin jaws are square but they lean outward also. This is due to the slop in the jaw slides or that the jaw slides were manufactured at an angle. If you place a 3/8" rod or drill bit in the jaws, they only grab the rod the first few mm of the 25mm jaws. You can put a band clamp around the jaws tighten it , then tighten the chuck and it will improve a little. On the flip side, the tilting jaws may be an advantage when expansion chucking is required. This may have been designed this way. After 20 years of ownership, I don't think I would have the .... to call Clay about it. These chucks just were not designed like metal lathe chucks and really once a piece is in round it doesn't matter much.
 
Kalia Kliban said:
The 35mm pin jaws for my Vicmarc 100 chuck are out of whack by about 1mm. It's hard to tell what caused it, and whether it's just a single jaw that's off or if all 4 have gotten tweaked somehow. I do very delicate work with these jaws so am not sure how this happened, but I really need accuracy when I'm using them. The amount of wobble I've got now isn't acceptable. Is this a fixable problem or do I just need to spring for a new set of jaws?
Kalia
Click to expand...
I would true them up. My guess is that at some point they were hit. I have hit my jaws several times. A good hit would probably make them woble or worst.
 
Dennis Weiner said:
Don, My talon 25mm pin jaws are square but they lean outward also. This is due to the slop in the jaw slides or that the jaw slides were manufactured at an angle. If you place a 3/8" rod or drill bit in the jaws, they only grab the rod the first few mm of the 25mm jaws. You can put a band clamp around the jaws tighten it , then tighten the chuck and it will improve a little. On the flip side, the tilting jaws may be an advantage when expansion chucking is required. This may have been designed this way. After 20 years of ownership, I don't think I would have the .... to call Clay about it. These chucks just were not designed like metal lathe chucks and really once a piece is in round it doesn't matter much.
Click to expand...
This just indicates the futility of expecting accuracy from a scroll chuck designed with sloppy tolerances such that it can be used without oil that combined with wood dust would gum up the mechanism and get oil on the wood.
So if rigidly gripping rounds is desired the only thing left is a collet chuck.
 
I agree with Don. We are asking a wood chuck to have the accuracy of a metal working chuck and they just don't have that kind of tolerance. My machinist friend says that even a high quality 3 jaw self aligning metal working chuck is not dead on and if he want's dead on accuracy he used a 4 jaw independent chuck. I asked him about collets because I do use those on both my metal lathe and wood lathe. He said they are generally pretty good but for super high quality they just aren't dead on. But then he is talking about 10 thousandth of an inch accuracy
 
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