Oneway Talon Chuck -- how to check for "trueness"

[Jamie Straw]

It was apparent just before Christmas that when I would tighten the Oneway Talon chuck to hold a piece of spindle stock, it was throwing the stock away from the axis of the lathe -- i.e., not perpendicular to the chuck body and not parallel to the spindle axis. Since other stuff was going wrong, I just stopped for Christmas and went back to troubleshooting last week. I'm here to ask (A) how one checks "trueness" in a chuck, and (B) what to do if it's not "true." I have plenty of experience tuning up miter saws, table saws and jointer, but precisely assessing a chuck is evading me. First, a description of what's been done so far, and what I'm seeing now:

I had been keeping the chuck pretty clean, but last week I took it apart down to the chuck body (did not remove the scroll). I cleaned the base jaws (that slide in the channels of the chuck body), and the channels they fit in. I also removed the taperlock adapter, made sure it and the corresponding chuck body taper were clean, and re-installed the adapter, being careful to alternately tighten the three screws a little at a time so it would be square in the taper (per instructions<click>).

When I put it back together and installed the spigot jaws, then closed the jaws all the way, one "seam" between the jaws seemed to lag behind the other three. When those three were fully tight, the fourth seam is very slightly open (no feeler gauge, can't say how much). Moving jaws around didn't change things. Same thing with the regular jaws. Next, I removed the jaws and decided to try and comparatively measure the base jaws with calipers. It seems that the #1 base jaw is a bit longer than the other three. Getting a perfect measurement is hard, but it seems to consistently measures longer from the inside tip to the outside.

So, please advise on all things chuck -- if I ever buy another one, I want to know how to check it immediately for precision!

 

[Jamie Straw]

Measurements

Here a pic of what I was measuring, base jaws tip to end. The #1 base jaw is 1/10th mm longer than the other three. Just a tiny (but perceptible) difference if the stock is only 2" long, but when it's 7" or 8" it really telegraphs. The gap in the seams of the gripping jaws seems to be bigger than that.

 

[Gerald Lawrence]

I cannot see this measurement being the problem. Was it off before you cleaned or did it start after? The slides on my Nova chucks do not look to be completely precision ground on the ends, as it is the location of the screws which makes the difference. Second question is do the jaws meet precisely all the way around when mounted and closed? That is where you should see precision.
The next area to look at is the insert. If not made by the chuck manufacturer it could be off. Also this insert sould be seated against the chuck body completely and against the flat on the spindle shoulder.......does it?

 

[Bill Blasic]

Jamie when you put the jaws on do not tighten the jaws screws all the way, just snug them. The close the jaws to get your ring (the circle the jaws make when closed) then tighten the screws. It is hard to grip a cylinder especially with the grooved teeth that normally come with the Oneway Chucks because wood is not the same density all around its perimeter and like stated make sure the wood is not seated against the bottom of the jaws.

 

[john lucas]

Ditto what Bill just said. Measuring the inner jaw length is useless. What is more critical is the placement of the screw holes and the shape of the jaws and the placement of the holes in the jaws. If you put the jaws on with the screws very slightly loose and then tighten the jaws until they touch. Tighten the screws and this should take care of the problem as far as the chuck is concerned.
Wood compresses differently when tightened in the chuck jaws. It will often pull to one side or the other depending entirely on how hard the wood is in that area where the jaws touch. If the wood was turned round before inserting in the jaws and the jaws are holding side grain all the way around such as in a spindle then it usually grips pretty accurately. However when you grip a piece say 6" long it can easily be pulled off center just a hair. I usually bring up the tailstock and align the piece before tightening the jaws all the way.
When gripping side grain pieces such as the tenon of a side grain bowl or a square block of wood cut from a board, you have end grain and side grain. If 2 jaws are on the side grain and 2 on the end grain it can pull it off center very easily. On a bowl where you've turned the tenon round before gripping it can be even worse because you may have the jaws unevenly gripping the side and end grain. What I try to do in this case is to rotate the tenon so the grain runs through the slots between the jaws. It's hard to describe without a drawing but what I want is each jaw to have the same amount of side grain and end grain contact. If the grain is running lets say from 12 to 6. You have end grain at 12 and 6 and side grain at 9 and 3. If you rotate the wood so the grain runs from about 1:30 to 7:30 then you end grain and side grain being gripped by the corners of each jaw. That usually keeps the wood straight unless you have a punky or soft area on one side.

 

[Fred Belknap]

Jamie I use Oneway chucks, I have a Talon and two Stronghold. Several years ago I was having trouble when I reversed a bowl and connected to the tenon I was getting a slight wobble. When I held a white paper behind a spinning bowl I would get a ghost of about 1/4" on a medium size bowl. I watched a video by one of the Beattys the one with the English accent, he showed how a chuck like the Talon would clamp on the tenon would throw the piece out of align. It was caused by how the teeth on the jaws would fit into the tenon. I change my reversing method by using the tailstock to put pressure on the inside of a bowl before tightening the jaws completely tight. This has cured my problem with the ghost bowls. I like my Oneway chucks because they hold great for how I work. I don't do much spindle work and if I do it is between centers so this may not apply to how you work. What others have said about centering the jaws before tightening the jaw screws is good advice. You might also check that the chuck is going all the way on the spindle. Some lathes have had problems with the chucks not seating all the way, this is pretty common on Grizzly lathes. I hope this helps and I also realize it is kind of rambling.

 

[hockenbery]

The Talon is an excellent chuck and should run true.
No chuck is perfect but you should get most items run in near true if you have a proper tenon.

Two more trouble shooting checks.

Test the jaws for flatness at the top. With the jaws installed put the chuck jaws side down on a flat surface. All jaws should touch the surface with no gaps.
Many years ago a student dropped a strong hold. Later I found it wasn't recentering well.
Checking the flatness revealed one jaw was apparently bent. New jaws fixed the problem.
The flat test could also reveal a gouge, a burr, or foreign matter on the tops of the jaws. This can be fixed by sanding the tops of the jaws flat with abrasive on a flat board.

Also check the insert.
Make sure the insert was mounted with the bolts through the unthreaded holes.
Bolts through the threaded holes and into the body will put the chuck off axis.
The threaded holes should be over the solid part of the body where the bolts are used as jack screws to lift the insert out of its taper.

Al

 

[diverjoe]

Jamie, ensure that you have started the #1 slide at the #1 mark on the chuck body. After you have inserted the four slides, screw them in until they touch. All 4 should meet at the center. Remember that the slides go in counter clockwise. Hope that this helps.
Joe

 

[Ed Sandle]

I also had trouble with a few of my Oneways when I first got them, and called Oneway to ask about it. Their suggestion was after first tightening the screws on the adapter, to lay the chuck down on a solid table with the insert up, and lay a piece of hardwood on top of the insert, and hit it squarely in the middle with a hammer. Worked for me screws actually tightened some more after that, and chucks ran much truer. I will say that my Vicmark chucks, all run extremely true, without any monkey business.

 

[Jamie Straw]

I cannot see this measurement being the problem. Was it off before you cleaned or did it start after? The slides on my Nova chucks do not look to be completely precision ground on the ends, as it is the location of the screws which makes the difference. Second question is do the jaws meet precisely all the way around when mounted and closed? That is where you should see precision.
The next area to look at is the insert. If not made by the chuck manufacturer it could be off. Also this insert should be seated against the chuck body completely and against the flat on the spindle shoulder.......does it?

Chuck was "off" before cleaning, that's what started all this. After reading your post, I measured the location of the screws (screw hole to tip of base jaw), and they seem to be the same, thanks. The base jaws may meet precisely -- at least to my eye -- but the gripping jaws do not (more on that later). If by "insert" you mean the taperlock (adapter to make the chuck fit my lathe), it is made by the same company and was installed by them originally. As described in my first post, I removed it, made sure mating surfaces were clean and carefully reinstalled per their instructions. Oneway states that there should be a gap of 0.020 to 0.050 between the adapter and the chuck body. I haven't measured it yet. Will check on whether it sits flat on the spindle shoulder (I think it does), but it's definitely tight.

As far as the jaws meeting (the add-on jaws, not the base jaws), below is a picture of the regular jaws fully closed. You can see that one "seam" meets tightly, the other three have varying degrees of gap between them. NOTE: the Talon chuck has a choice of 2 different slots below the jaws for a pin to fit into which limits the distance the jaws can be expanded. There's a short slot (for beginners) and a longer slot (for those who pay attention). When I swapped the pinned jaw from one slot to the other, the wide-gap position changed also. There's still one seam that's totally tight, and three that aren't, but the widest gap switches from one side to the other. As I'll mention in a reply to Al, the jaws are not flat on top either (i.e., if turned upside down on a flat surface, they whole thing rocks). A small straightedge placed across the jaws verifies.

 

[Jamie Straw]

Jamie when you put the jaws on do not tighten the jaws screws all the way, just snug them. The close the jaws to get your ring (the circle the jaws make when closed) then tighten the screws. It is hard to grip a cylinder especially with the grooved teeth that normally come with the Oneway Chucks because wood is not the same density all around its perimeter and like stated make sure the wood is not seated against the bottom of the jaws.

Thanks to all who mentioned this important part of the process -- I will adhere to instructions henceforth!! Was already aware of not seating the stock against the bottom of the jaws.

 

[Jamie Straw]

[Snip] It will often pull to one side or the other depending entirely on how hard the wood is in that area where the jaws touch. If the wood was turned round before inserting in the jaws and the jaws are holding side grain all the way around such as in a spindle then it usually grips pretty accurately. However when you grip a piece say 6" long it can easily be pulled off center just a hair. I usually bring up the tailstock and align the piece before tightening the jaws all the way.

Mmmm, way more than a hair! Tried the tailstock trick and it didn't work, even after I worked on alignment; offset seems to come mostly from the chuck. At the very end of tightening, the stock jigs in one direction. Thanks for info about balancing side/end grain in chuck, have been conscious of that but more detail is always good.

 

[Jamie Straw]

Jamie I use Oneway chucks, I have a Talon and two Stronghold. Several years ago I was having trouble when I reversed a bowl and connected to the tenon I was getting a slight wobble. When I held a white paper behind a spinning bowl I would get a ghost of about 1/4" on a medium size bowl. I watched a video by one of the Beattys the one with the English accent, he showed how a chuck like the Talon would clamp on the tenon would throw the piece out of align. It was caused by how the teeth on the jaws would fit into the tenon. I change my reversing method by using the tailstock to put pressure on the inside of a bowl before tightening the jaws completely tight. This has cured my problem with the ghost bowls. I like my Oneway chucks because they hold great for how I work. I don't do much spindle work and if I do it is between centers so this may not apply to how you work. What others have said about centering the jaws before tightening the jaw screws is good advice. You might also check that the chuck is going all the way on the spindle. Some lathes have had problems with the chucks not seating all the way, this is pretty common on Grizzly lathes. I hope this helps and I also realize it is kind of rambling.

Thanks, Fred. I will keep the bowl tips in mind when I'm turning them. As far as I can tell, the chuck is going all the way on the spindle -- it's certainly tight -- but I'll look again in case it's not apparent.

 

[Jamie Straw]

[Snip]Two more trouble shooting checks.

Test the jaws for flatness at the top. With the jaws installed put the chuck jaws side down on a flat surface. All jaws should touch the surface with no gaps. Many years ago a student dropped a strong hold. Later I found it wasn't recentering well. Checking the flatness revealed one jaw was apparently bent. New jaws fixed the problem. The flat test could also reveal a gouge, a burr, or foreign matter on the tops of the jaws. This can be fixed by sanding the tops of the jaws flat with abrasive on a flat board.

Ohhh, bummer. Chuck rocks when placed upside down on flat surface -- 3 different cast iron tool tops, just to be sure. Using a small straight-edge across the meeting edges (chuck closed) confirms they don't match. I don't always use a tenon, as this chuck will hold square stock (and I always check to make sure it really is square) -- the corners fit in the spaces between the jaws. Have spindle stock alignment problems with or without use of tenon.

Also check the insert.Make sure the insert was mounted with the bolts through the unthreaded holes. Bolts through the threaded holes and into the body will put the chuck off axis.The threaded holes should be over the solid part of the body where the bolts are used as jack screws to lift the insert out of its taper.

Original mounting was done before it was shipped to me. For removal, cleaning and remounting, I read and followed the instructions carefully, and understand the difference between the holes for jack screw action and the holding holes. Mounting was done correctly.

 

[Jamie Straw]

Jamie, ensure that you have started the #1 slide at the #1 mark on the chuck body. After you have inserted the four slides, screw them in until they touch. All 4 should meet at the center. Remember that the slides go in counter clockwise. Hope that this helps.
Joe

Thanks, Joe. Fortunately, the instructions for this chuck are pretty complete, so I did it correctly. Miracles never cease.

 

[Jamie Straw]

I also had trouble with a few of my Oneways when I first got them, and called Oneway to ask about it. Their suggestion was after first tightening the screws on the adapter, to lay the chuck down on a solid table with the insert up, and lay a piece of hardwood on top of the insert, and hit it squarely in the middle with a hammer. Worked for me screws actually tightened some more after that, and chucks ran much truer. I will say that my Vicmark chucks, all run extremely true, without any monkey business.

Thanks, Musky, had not thought or heard of doing that. I ever-so-slightly loosened the screws (actually bolts I guess) and did that, tightened it up and gave it one more whack for good measure. Unfortunately, didn't resolve the dilemma but at least I know the taperlock is on square for sure!

 

[Owen Lowe]

As far as the jaws meeting (the add-on jaws, not the base jaws), below is a picture of the regular jaws fully closed. You can see that one "seam" meets tightly, the other three have varying degrees of gap between them. NOTE: the Talon chuck has a choice of 2 different slots below the jaws for a pin to fit into which limits the distance the jaws can be expanded. There's a short slot (for beginners) and a longer slot (for those who pay attention). When I swapped the pinned jaw from one slot to the other, the wide-gap position changed also. There's still one seam that's totally tight, and three that aren't, but the widest gap switches from one side to the other. As I'll mention in a reply to Al, the jaws are not flat on top either (i.e., if turned upside down on a flat surface, they whole thing rocks). A small straightedge placed across the jaws verifies.

View attachment 9149

It sounds as if the taper-lock is installed squarely — misalignment would be apparent in the spinning chuck body with a “ghosting†of the silhouette. Secondly, if the base jaws come to a complete close with no gaps between the nose sections, then I’d assume the body, scroll, and base jaws are just fine.

I can see the varying gaps between the secondary jaws at the center hole. Do you own (or can you borrow) other jaws that you could install to see if they exhibit the same gaps? (I believe I have a spare set of #2-standard jaws if you’d like to borrow them.)

If’n it were my problem, I’d swap around the secondary jaws to as many configurations as I can think of to see if the problem exists no matter where they are mounted. Keep the pinned jaw in the long slot position and swap the other three around to see what happens. I, too, follow the method of closing the jaws completely before final snugging of the mounting screws.

Hmmm. If you leave the screws barely snug and bring the jaws to a close what happens with the gaps?

I’m suspecting a bad jaw set and don’t know if Oneway would send a replacement. BTW, the jaw faces where they’d bottom on a tenon can be trued up with a scraper so they’re all the same length — the metal is certainly soft enough for HSS as I’ve taken a few unplanned bites from my jaws over the years.

 

[hockenbery]

Ohhh, bummer. Chuck rocks when placed upside down on flat surface -- 3 different cast iron tool tops, just to be sure. Using a small straight-edge across the meeting edges (chuck closed) confirms they don't match. I don't always use a tenon, as this chuck will hold square stock (and I always check to make sure it really is square) -- the corners fit in the spaces between the jaws. Have spindle stock alignment problems with or without use of tenon. Original mounting was done before it was shipped to me. For removal, cleaning and remounting, I read and followed the instructions carefully, and understand the difference between the holes for jack screw action and the holding holes. Mounting was done correctly.

With the jaws uneven on the top you definitely have a problem with that set of jaws or with the chuck.
Now to determine which.
In my case the chuck was dropped and a #2 jaw was bent. New #2 jaws fixed it.
The primary jaws were fine.

If one jaw is sticking up and it is the one with the alignment pin it may be sticking out too far you can tap it in. It may be bent, pull it out.
Clean the alignment track.
Mark the jaws that stick up You can swap the jaws with those opposite each other if the same jaws are proud I would think you just need new jaws.
If you have another set of jaws or can borrow a set from a club member put those on and tops pass the flat test then you probably need a new set of jaws.

These test should tell you if it is problem with the jaw set or the primary jaws a and the scroll.
It might be time to call ONEWAY.

The chuck should still hold square stock. You will need to center the blank and hold it I place with light pressure while tightening the chuck.
It should then hold it for turning with or without the tailstock.

Al

 

[Jamie Straw]

It sounds as if the taper-lock is installed squarely — misalignment would be apparent in the spinning chuck body with a “ghosting†of the silhouette. Secondly, if the base jaws come to a complete close with no gaps between the nose sections, then I’d assume the body, scroll, and base jaws are just fine.

I'm pretty confident that the taperlock is square, have seen no ghosts. No gaps between base jaw nose sections unless it's so small I can't see it. Good news there.

I can see the varying gaps between the secondary jaws at the center hole. Do you own (or can you borrow) other jaws that you could install to see if they exhibit the same gaps? (I believe I have a spare set of #2-standard jaws if you’d like to borrow them.)

The only other jaws I have are spigot jaws, which have their problems too. Your offer is very generous (and you're not far away from my Puget Sound Location). If those are spare jaws for you, I'd love to borrow them. It would be a couple weeks before I'd see any local turner(s) who might have such. It should be only a 2-day ship with Priority Mail, which I'm glad to pay for. Will PM you tonight.

If’n it were my problem, I’d swap around the secondary jaws to as many configurations as I can think of to see if the problem exists no matter where they are mounted. Keep the pinned jaw in the long slot position and swap the other three around to see what happens. I, too, follow the method of closing the jaws completely before final snugging of the mounting screws.

I'll have to do that in an organized fashion. I've changed the one with the pin, but haven't done a complete survey of the different configurations.

Hmmm. If you leave the screws barely snug and bring the jaws to a close what happens with the gaps?

Well, that's pretty close to what I'm doing with the "... closing the jaws completely before final snugging of the mounting screws" technique. Am I misunderstanding? I've been very gently twirling the T-handle hex key between index finger and thumb (sorta like twirling a wine glass, if you ever do that) until it stops, so the screw is in the recess but not snugged, then tightening the jaws, then tightening the screws. I tightening the inside set first, going like 1 - 3 - 2 - 4 (old habit learned when assembling motorcyles). Then I tighten the outside set, same technique. The gaps are there before and after snugging, though they may change a bit afterward.

I’m suspecting a bad jaw set and don’t know if Oneway would send a replacement. BTW, the jaw faces where they’d bottom on a tenon can be trued up with a scraper so they’re all the same length — the metal is certainly soft enough for HSS as I’ve taken a few unplanned bites from my jaws over the years.

Hmmm, not sure I'm up to that but I'm sure someone in this area is brave enough. Last resort, methinks. After I've done all the things suggested here, I'll call Oneway if no success. This situation would be a test of extreme Customer Service, given how long I've had the jaws. They just have hardly been used, relative to the time owned.

 

[Jamie Straw]

With the jaws uneven on the top you definitely have a problem with that set of jaws or with the chuck.
Now to determine which.
In my case the chuck was dropped and a #2 jaw was bent. New #2 jaws fixed it.
The primary jaws were fine.

If one jaw is sticking up and it is the one with the alignment pin it may be sticking out too far you can tap it in. It may be bent, pull it out.
Clean the alignment track.
Mark the jaws that stick up You can swap the jaws with those opposite each other if the same jaws are proud I would think you just need new jaws.
If you have another set of jaws or can borrow a set from a club member put those on and tops pass the flat test then you probably need a new set of jaws.

These test should tell you if it is problem with the jaw set or the primary jaws a and the scroll.
It might be time to call ONEWAY.

The chuck should still hold square stock. You will need to center the blank and hold it I place with light pressure while tightening the chuck.
It should then hold it for turning with or without the tailstock.

Al

Thanks, Al, I'll examine closely (again) tonight, and spend the evening swapping jaws like a mad-woman, check the pin, etc. When I turn square stock, it still should not be against the base of the jaws, correct?

 

[Owen Lowe]

I tightening the inside set first, going like 1 - 3 - 2 - 4 (old habit learned when assembling motorcyles). Then I tighten the outside set, same technique. The gaps are there before and after snugging, though they may change a bit afterward.

Like wheel lug nuts, yes. The gaps before and after are what I was looking for. If they appeared after snugging down then I’d guess the screw holes were pulling things out of alignment — but that doesn’t appear to be the case.

Hmmm, not sure I'm up to that but I'm sure someone in this area is brave enough. Last resort, methinks. After I've done all the things suggested here, I'll call Oneway if no success. This situation would be a test of extreme Customer Service, given how long I've had the jaws. They just have hardly been used, relative to the time owned.

Actually scraping the jaws is pretty easy and painless. Don’t do that now though until you get the gap thing fixed.

Is the high jaw the one with the pin? As Al suggested the pin can be driven up or down or removed completely.

 

[hockenbery]

Thanks, Al, I'll examine closely (again) tonight, and spend the evening swapping jaws like a mad-woman, check the pin, etc. When I turn square stock, it still should not be against the base of the jaws, correct?

Jamie, when I drive square stock in the chuck I rest it on the bottom of the jaws. It may only touch on one corner if it isn't cut real square.
I mark the center on the tailstock end and use the tailstock to line it up and hold it in place while I tighten the chuck.
Since there is nothing for the tops of the jaws to ride on resting on the bottom of the chuck jaws is good or at least does no harm.
The ONEWAY jaws grip square stock really well.

One of the bad things about resting a tenon on the bottom is that the closing of the jaws will,post it off center.
Using the tailstock for alignment minimizes the off center push.

I usually use the tailstock support for the initial roughing.

Al

 

[Jamie Straw]

Jamie, when I drive square stock in the chuck I rest it on the bottom of the jaws. It may only touch on one corner if it isn't cut real square.
I mark the center on the tailstock end and use the tailstock to line it up and hold it in place while I tighten the chuck.
Since there is nothing for the tops of the jaws to ride on resting on the bottom of the chuck jaws is good or at least does no harm.
The ONEWAY jaws grip square stock really well.

One of the bad things about resting a tenon on the bottom is that the closing of the jaws will,post it off center.
Using the tailstock for alignment minimizes the off center push.

I usually use the tailstock support for the initial roughing.

Al

What causes that, Al? I'm too sleepy (or clueless) to figure it out.

 

[Jamie Straw]

[Snip] Is the high jaw the one with the pin? As Al suggested the pin can be driven up or down or removed completely.

Nope, the pins are just right. At least something is "just right." (whine)

 

[hockenbery]

What causes that, Al? I'm too sleepy (or clueless) to figure it out.

When you have turned a tenon you have created a round surface on center with your turning.
The ring where the tenon meets the turning should register with the tops of the jaws of the chuck.
If the tenon is too long it prevents the ring from making contact and the piece can be tilted off center in the chuck.
A flat surface turned to rest on the tops of the jaws increases the support for the tenon and makes it easier to line up the tenon in the chuck.

On square blanks there is no tenon and there is nothing to register against. So the best centering is made by holding the blank in center with the tailstock.

 

[Bill Boehme]

Check Chuck Crazy Characteristics

Based on what I have read it doesn't sound like the base jaws are defective, but I wouldn't rule them out yet. Defective parts can happen. I have a Vicmarc 120 Chuck with one defective base jaw. It fits very loosely in the guides in the chuck body. However, it hasn't proven to cause a significant problem so I have chosen to ignore it. In your case, it appears that the problem moves as you move the top jaws around so I would concentrate on seeing if one top jaw is defective. If the problem is a bad top jaw then a different set of jaws should work fine. Is this the case? The top jaws are made of soft steel so they could bend if dropped or struck very hard due to a catch.

Just to be certain that the base jaws are OK, check to see that one doesn't fit loosely in the slot in the body. Also, check to see if the teeth that engage the scroll aren't damaged. The scroll itself has been hardened, but the base jaws aren't quite as hard so they can deform a bit. The picture of the top jaws is slightly fuzzy, but as far as I can tell they mesh together just fine -- don't expect a perfect fit because they aren't that precise. An uneven top however is a problem that needs to be corrected. Make some measurements before sanding. If you have the same problem with other jaws then sanding is the wrong thing to do. Also, sanding can actually make things worse if not done right.

Always have a shoulder on a spindle if you want things to align. Don't over tighten. A machinist wiould say that a chuck is a precision tool and over tightening will turn it into a non-precision tool. How tight? Using just one hand and no more than moderate force to snug the chuck should be plenty tight. More than that and you will be crushing wood fibers and possibly even bending jaws by a few thousandths of an inch if you are being a gorilla. There are a lot of opinions about tightening ... My opinion comes from an engineering manufacturing background ... and I like my opinion ... a lot.

 

[Jamie Straw]

New findings

OK, I still have some things to check based on Bill's last post, but here are two things I've seen, which may or may not be relevant. I've tried various jaw placements, and the chuck still rocks one one axis, but not the one 90 degrees to it.

1. There is daylight between the flats of two pairs of the base jaws. Diagram below shows a red line indicating these adjacent areas. The seam between 2&3 is .003", the seam between 4&1 is slightly less than that. No daylight in the other two seams. Have no idea if this is significant. However, when the jaws are placed down (earlier test) the chuck rocks if tested along the axis of the red line, but not if trying to rock it 90 degrees to that line.


2. The taper slot in base jaw #2 (which is what registers the secondary jaw) does not appear to be uniform in depth across the slot (from left to right). Very hard to measure accurately (impossible really), but looks less deep on left than on right. Initial impression is that the top of the flat drops down a bit, which would tip the attached jaw.



My acquaintance who has metal lathe chops is going to look at the chuck Thursday if I can't figure things out between now and Wednesday afternoon, he'll have it for a couple of days. I'm hoping he can measure that taper slot and also sort the wheat from the chaf in diagnosing this thing. What I did today (little time available) was to take the base jaws out, make sure the grooves were clean and blew out the chuck with compressed air to clear anything affecting the scroll (really didn't want to take the scroll out).

 

[Jamie Straw]

Varsol?

Instructions say if the chuck is sticky to "soak in varsol or mineral spirits with about 10% oil added." What is "varsol" (sloppy definition in web search)? I'd just as soon use something premixed than to make it up myself. What do y'all use to soak your chucks in?

 

[Bill Boehme]

Good information about the things that you have found. The fact that the jaws don't meet up perfectly is not the problem. We're talking about chucking up wood something that we measure with a tape measure, Mark with a crayon, and then cut with a chainsaw. A few thousandths of an inch one way or the other in the chuck jaws alignment is nothing. I have a whole stable full of chucks and none of the jaws close together perfectly without one or more gaps. I didn't take any measurements, but the largest gaps are about like the thickness of a fingernail. The regeristration keyway that aligns the top jaw with the base jaw sounds like it might be the problem. I'm pretty sure that the boss on the top jaw doesn't bottom out in the keyway on the base jaw. However, if it is malformed, it might prevent proper seating. When you mate the two parts together they should slide smoothly along the slot. If the problem is a bur, you migh be able to clean the slot up. Otherwise, give Oneway a call and they will send a replacement jaw ... Maybe even for free if it is a manufacturing defect.

 

[Jamie Straw]

Input from "metal lathe guy"

[Snip] The regeristration keyway that aligns the top jaw with the base jaw sounds like it might be the problem. I'm pretty sure that the boss on the top jaw doesn't bottom out in the keyway on the base jaw. However, if it is malformed, it might prevent proper seating. When you mate the two parts together they should slide smoothly along the slot. If the problem is a bur, you migh be able to clean the slot up. Otherwise, give Oneway a call and they will send a replacement jaw ... Maybe even for free if it is a manufacturing defect.

Metal lathe (and some wood lathe) guy took a look at scroll chuck today, showed me how I can check the machining on that one base jaw that seems a little off. You're right, the aux jaws don't ride on the bottom of the slots, just the tops, he's skeptical that there's a significant problem there, but showed me how I might tune up those base jaws if need be. Suggested, as suggested here, that I take care of Morse taper problem ASAP.

One other thing I asked him about is how the tailstock on my lathe moves side to side between the rails, and I have to position it just right before locking it. If I just lock without checking it will be in a different place than if I hold it in position first. Does anyone know if there's an adjustment for this on the old Jet 1236's?? I don't see anything on the tailstock body that's obvious. Perhaps in the locking mechanism? Otherwise I guess I need to shim the male part that rides between the rails. Thanks for all your help on this, will plunge in tomorrow and see what can be fixed. Time to get re-acquainted with spinning wood.

 

[Gerald Lawrence]

Metal lathe (and some wood lathe) guy took a look at scroll chuck today, showed me how I can check the machining on that one base jaw that seems a little off. You're right, the aux jaws don't ride on the bottom of the slots, just the tops, he's skeptical that there's a significant problem there, but showed me how I might tune up those base jaws if need be. Suggested, as suggested here, that I take care of Morse taper problem ASAP.

One other thing I asked him about is how the tailstock on my lathe moves side to side between the rails, and I have to position it just right before locking it. If I just lock without checking it will be in a different place than if I hold it in position first. Does anyone know if there's an adjustment for this on the old Jet 1236's?? I don't see anything on the tailstock body that's obvious. Perhaps in the locking mechanism? Otherwise I guess I need to shim the male part that rides between the rails. Thanks for all your help on this, will plunge in tomorrow and see what can be fixed. Time to get re-acquainted with spinning wood.

Not for sure , but I think some has talked about the tailstock on the 1236 before and his was slipping. His solution was to make a larger contact plate to go between the rails. Not sure this has anything to do with the positive registration of the tailstock, just something I remember.

 

[Bill Boehme]

Metal lathe (and some wood lathe) guy took a look at scroll chuck today, showed me how I can check the machining on that one base jaw that seems a little off. You're right, the aux jaws don't ride on the bottom of the slots, just the tops, he's skeptical that there's a significant problem there, but showed me how I might tune up those base jaws if need be. Suggested, as suggested here, that I take care of Morse taper problem ASAP.

One other thing I asked him about is how the tailstock on my lathe moves side to side between the rails, and I have to position it just right before locking it. If I just lock without checking it will be in a different place than if I hold it in position first. Does anyone know if there's an adjustment for this on the old Jet 1236's?? I don't see anything on the tailstock body that's obvious. Perhaps in the locking mechanism? Otherwise I guess I need to shim the male part that rides between the rails. Thanks for all your help on this, will plunge in tomorrow and see what can be fixed. Time to get re-acquainted with spinning wood.

I don't know of any woodturning lathe that has an adjustment to take out the lateral slop in the tailstock. All lathes have some slop there. If it is 1/8 inch then that would be something to worry about. If it is 1/32 inch then your lathe is pretty good. one problem with shimming or something to give a snug fit is that the inner ways guide probably isn't exactly parallel to the spindle axis. And, in some lathes, the inner ways guide isn't perfectly straight. Unlike metal lathes, wood lathes really aren't high precision machines. If you were to shim the tailstock to ride snugly in the ways, it would be a big let-down to find out that that the tailstock alignment with the spindle is worse than before and without any way to compensate for the misalignment. It would be a major job to boresight the spindle and tailstock and eliminate the lateral play in the tailstock (and headstock in some cases).

 

[Jamie Straw]

Not bad, not great...

I don't know of any woodturning lathe that has an adjustment to take out the lateral slop in the tailstock. All lathes have some slop there. If it is 1/8 inch then that would be something to worry about. If it is 1/32 inch then your lathe is pretty good. one problem with shimming or something to give a snug fit is that the inner ways guide probably isn't exactly parallel to the spindle axis. And, in some lathes, the inner ways guide isn't perfectly straight. Unlike metal lathes, wood lathes really aren't high precision machines. If you were to shim the tailstock to ride snugly in the ways, it would be a big let-down to find out that that the tailstock alignment with the spindle is worse than before and without any way to compensate for the misalignment. It would be a major job to boresight the spindle and tailstock and eliminate the lateral play in the tailstock (and headstock in some cases).

Thanks for hangin' in there on this thread, Bill! It'll go off-line 1/16", and is always a bit low (may add another layer of strapping-tape-shim to tailstock base). Hoping that the Nova live center set I ordered will help, because when I'm turning a thinnish handle that's 6.5" long with a 7mm hole at the tailstock end riding too high on the 60° center point, it wreaks havoc. Good News is that I discovered one correctable problem -- the headstock wasn't tightened down quite enough. I really laid into the lock-down lever this afternoon while messing with the Beall buffer, and alignment improved. It appears now that if I hold the tailstock against the far rail, things line up just fine laterally. Before horsing the headstock lock, "center" was somewhere between far and near rails.