Runout on Nova jaws

[Gary Pennington]

I started to turn some knobs today, put a piece of blackwood that I had turned round between centers in the pin jaws on my Nova G3. Right away I noticed a lot of runout on the piece. It's been ages since I had used those jaws so don't remember if I had the issue before.

Dug out an indicator and magnetic base to do some investigation. The OD of the chuck had about .002" runout, respectable I think. I put the shank of a 1/2" drill bit in the jaws and ran the indicator on the remaining full round (the pic looks like the indicator is dropping into the flute but it's not) part of the shank. Runout was .010" right in front of the jaws. I removed the chuck and checked the spindle on the 3520B--zero runout on the shoulder right in front of the bearing.

So pulled the jaws off the G3 and put them on a G2 that is threaded for the spindle, not an insert chuck as the G3 is. Runout on the OD was .003, the drill was exactly the same .010" runout.

I don't know what is acceptable but when I can see runout on a chucked part it seems to me that's too much. What should one expect? Looking around the internet I find numbers for spindle runout but not chuck jaws.

Thanks, Gary

indicator.jpg

[Edward Weber]

The jaws themselves usually aren't the issue, it's usually the chuck.
The jaws are just a lump of steel. the amount of movement the jaw slide has (play) has more to do with running true or not.
I would say, make sure the locking groove is clean on the slides and jaws so there is a good mating surface. Put the jaws on in proper order and try again. Try a few sets of jaws and a few different bits to see where the run out is coming from.
It could be as simple as needing a good cleaning. A G-3 is an open backed chuck and if debris gets into the scroll ring, it can throw off a jaw slide or two, resulting in run out.

[Steve Eure]

Not being snarkie, but are your jaws in the right numbered sequence? And are they from the same set? The reason I asked this last question is because I have several sets of the same size jaws and I try not to get them mixed up, since they are not identical. The cuts may be off a bit between sets of jaws and they will not match up perfectly with others. Again, not being snarkie.

[Gary Pennington]

It's the same jaws on two different chucks with the same results.

The jaws are sequenced correctly and are a set which I bought new at Rockler maybe five years ago. It's the only set of these jaws I've ever had so I doubt they could be mixed with another set. It's quite possible they have done this since day one, they're rarely used.

I may get another set of jaws to try, maybe someone in our club has a set.

Gary

[John K Jordan]

If the runout has always been there you may not have noticed it depending on how you used it. For example, gripping and turning square stock would result in a perfectly round turning regardless on the runout. I have several type and sets of pin and small spigot jaws and the Nova mini spigot jaws (which I like best and use often) and the runout is not unreasonable on any. The mini spigot jaws use 8 screws instead of 4 which seems like a better design.

Is the drill bit good, any burrs? Is the runout in the same place relative to the jaws and chuck if you rotate it some or use a different bit? (I used a hardened precision rod when checking for runout.)

I might be inclined to investigate further, maybe something like this: Remove the jaws and put them flat on the table in the right order and make sure they are a matched set. (someone somewhere could have mixed up some before you bought them which might be obvious.) Make sure the grooves and slides are clean, no burrs, and don’t have excessive play. (I use a small brass brush to clean, usually take the slides out and chuck apart and clean everything.) I bought some used SN chucks that had been abused and the mechanism on one was sloppy and the other was warped.

While the jaws are off, try gripping the drill with the slides themselves, no jaws, and check the runout. (I’ve turned small stock in Supernova II slides this way, I assume the G3 works the same way but I gave mine away so I can’t check.) If the runout is there with no jaws the chuck might be the problem. I checked a chuck like that and it was pretty good.

Reinstall the jaws in the same position and tighten the screws as described in the chuck manual and recheck the runout. Mark the high spot on the jaws and the chuck. Remove and reinstall the jaws in the next position and recheck. (The jaws don’t have to be mounted with jaw “1” on slide “1” - they can start on any slide as long as they stay in the right order.) See if the runout it’s the same and the high spot is in the same place relative to the jaws and the chuck. Based on what I found I might try other things.

JKJ

It's the same jaws on two different chucks with the same results.

The jaws are sequenced correctly and are a set which I bought new at Rockler maybe five years ago. It's the only set of these jaws I've ever had so I doubt they could be mixed with another set. It's quite possible they have done this since day one, they're rarely used.

I may get another set of jaws to try, maybe someone in our club has a set.

Gary

[Richard Coers]

Runout on the body of the chuck means nothing. You never use the body, so who cares if it's out of round. More importantly is how clean the face of the threaded adapter and the face of the lathe shaft was when you installed the chuck. I've been turning for decades, never put an indicator on a chuck, maybe because there were no 4 jaw scroll chucks when I started turning. But I also don't own a Nova chuck because there are much better chucks on the market. Oneway is my preference. There has been lots of discussion on the internet about runout with a Nova chuck with a Woodriver adapter. Most say going to a Nova adapter was the cure.

[Gary Pennington]

Runout on the body of the chuck means nothing. You never use the body, so who cares if it's out of round. More importantly is how clean the face of the threaded adapter and the face of the lathe shaft was when you installed the chuck. I've been turning for decades, never put an indicator on a chuck, maybe because there were no 4 jaw scroll chucks when I started turning. But I also don't own a Nova chuck because there are much better chucks on the market. Oneway is my preference. There has been lots of discussion on the internet about runout with a Nova chuck with a Woodriver adapter. Most say going to a Nova adapter was the cure.

Thanks for your thoughts.

Gary

[Gary Pennington]

Cleaned the spindle and chuck mating faces. Checked both chucks without jaws using the vertical rod from a dial indicator base instead of the drill bit. It rolled smoothly across the cast iron table of my SawStop. Runout on the G3 was .010", G2 was .008". Clearly both chucks have an internal issue. I'll disassemble and clean and recheck. Thanks to all that responded, I thought for sure it was an issue with the jaws.

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Gary

If the runout has always been there you may not have noticed it depending on how you used it. For example, gripping and turning square stock would result in a perfectly round turning regardless on the runout. I have several type and sets of pin and small spigot jaws and the Nova mini spigot jaws (which I like best and use often) and the runout is not unreasonable on any. The mini spigot jaws use 8 screws instead of 4 which seems like a better design.

Is the drill bit good, any burrs? Is the runout in the same place relative to the jaws and chuck if you rotate it some or use a different bit? (I used a hardened precision rod when checking for runout.)

I might be inclined to investigate further, maybe something like this: Remove the jaws and put them flat on the table in the right order and make sure they are a matched set. (someone somewhere could have mixed up some before you bought them which might be obvious.) Make sure the grooves and slides are clean, no burrs, and don’t have excessive play. (I use a small brass brush to clean, usually take the slides out and chuck apart and clean everything.) I bought some used SN chucks that had been abused and the mechanism on one was sloppy and the other was warped.

While the jaws are off, try gripping the drill with the slides themselves, no jaws, and check the runout. (I’ve turned small stock in Supernova II slides this way, I assume the G3 works the same way but I gave mine away so I can’t check.) If the runout is there with no jaws the chuck might be the problem. I checked a chuck like that and it was pretty good.

Reinstall the jaws in the same position and tighten the screws as described in the chuck manual and recheck the runout. Mark the high spot on the jaws and the chuck. Remove and reinstall the jaws in the next position and recheck. (The jaws don’t have to be mounted with jaw “1” on slide “1” - they can start on any slide as long as they stay in the right order.) See if the runout it’s the same and the high spot is in the same place relative to the jaws and the chuck. Based on what I found I might try other things.

JKJ

[Dick Strauss]

Pin jaws are not strong and can easily be bent largely because of the distance they stick out from the chuck face. A friend had pin jaws on his chuck holding a dowel pin driven into a recess in the wood being turned (chuck/pin jaws/dowel/wood). One good catch and the jaws were never the same!