Lathe seems wobbling

[YoYo]

Folks,
Happy New Year! I haven't came here in long time. I hope everyone is doing well. I have a question, please take a look the attachment. Can you tell it's wobbling? Why? Thanks ?

 

[jttheclockman]

Can not tell if the back handwheel is wobbling. I see the tailstock end with the mandrel saver wobbling which could mean bent rod. I always hate doing 2 blanks at a time. The people that do that just ask for trouble all the time. Shorten the blank up to one and see if it wobbles. That is a thin rod that is used for holding blanks on and any pressure from dull turning tools to sanding especially will bend that thing. Not a fan. If you take everything off does the lathe still wobble. Start there. check to make sure lathe is level both ways and is laying flat with all legs sitting flat.

 

[YoYo]

Can not tell if the back handwheel is wobbling. I see the tailstock end with the mandrel saver wobbling which could mean bent rod. I always hate doing 2 blanks at a time. The people that do that just ask for trouble all the time. Shorten the blank up to one and see if it wobbles. That is a thin rod that is used for holding blanks on and any pressure from dull turning tools to sanding especially will bend that thing. Not a fan. If you take everything off does the lathe still wobble. Start there. check to make sure lathe is level both ways and is laying flat with all legs sitting flat.

Yes, the lathe is level. The mandrel is those expandable ones. I have to extend the mandrel. If we turn the two blanks one at the time, I'm afraid I can't tell if they are even. I think the headstock wobble a little bit. I also need to replace the belt. Thanks for the suggestions.

 

[egnald]

Greetings from Nebraska.

I think part of your problem is because you are using a mandrel and mandrel saver combination that is not really meant to be used together in the way you have it configured.

Your mandrel appears to be an "adjustable mandrel" design based on the two nuts near the headstock. The mandrel shaft is held and centered by a collet that is part of the design. The intended purpose is so that you can avoid using spacer bushings by shortening the mandrel shaft.

The mandrel shaft itself appears to be a standard threaded mandrel shaft that uses a knurled knob. For these you should be using a standard 60-degree live center that mates up with a 60-degree dimple in the end of the threaded section. The live center and the dimple are what keep the mandrel centered and running true at the tailstock end.

With the mandrel saver, you should not have the brass knob and spacer bushing at the end of the mandrel. This will let more of the mandrel shaft (and not just the threads) go into the mandrel saver. The mandrel saver is drilled out so that a mandrel shaft will fit through it and will essentially run true because of the hole size relative to the mandrel shaft diameter.

In the configuration you have, it looks like the threads of the mandrel shaft go into the mandrel saver insead of the mandrel itself. The threads are likely a smaller diameter than the shaft and since the hole in the mandrel saver is made to fit the shaft, there is a sloppy fit, so the mandrel isn't being held centered in the mandrel saver. Since it is not concentric it is wobbling at the end of the mandrel.

Try this - Adjust the mandrel shaft so that it is long enough to accomodate the bushings and blanks while still leaving some of the shaft (not just the threads) extend past the last turning bushing. Without a spacer bushing and without the brass knob/nut, slide the mandrel into the hole in the mandrel saver and use pressure from the tailstock (mandrel saver) to apply pressure to the bushings and blanks for turning. This should keep your mandrel concentric and as short as possible.

So it looks like this:

An alternative would be to use the mandrel as you have it configured, but shorten it so that you don't need the spacer bushing at the end. Then replace your mandrel saver with a 60-degree live center that fits inside the 60-degree dimple in the end of the threads. You don't need to apply excessive pressure with the tailstock as it only needs to hold the mandrel to keep it centered. Excessive pressure can cause the mandrel to bend slightly which would show up as a wobble in the middle of the mandrel. - The mandrel saver is designed to prevent this excessive pressure and wobble in the middle, so I think the method above that ditches the spacer and brass nut would be the best case.

I hope this helps.
Dave

 

[leehljp]

If we turn the two blanks one at the time, I'm afraid I can't tell if they are even. I think the headstock wobble a little bit. I also need to replace the belt. Thanks for the suggestions.

While it may work for some, trying to make two parts equal on a lathe in the manner that you do will have its problems for sure. John is right on with his comments; YoYo is right, Dave is too. If you want both the same size, get a good set of calipers and learn to measure with a finer instrument than bushings, spacers and eyeballs. Bushings will wear down a smidgin EVERYtime you touch it accidentally with a sandpaper and or tool. Measure the fittings of the pen with a good set of calipers that measure to .005, or a much better set that measures to .0001 at least.

Measure the fittings of the pen, mark them down on a piece of paper or in a notebook. Turn the blanks to that size. When close and if you do use sandpaper or other sanding material use the fine to bring to size. Measure every minute or so until it is the right size.

This takes an extra minute or two for each blank, but you and any customer will feel the difference as they will be perfect.

And yes, you will have wobble in the way it is set up as it appears in the picture. Multiple parts pushed together like that are a recipe for trouble.

 

[YoYo]

Greetings from Nebraska.

I think part of your problem is because you are using a mandrel and mandrel saver combination that is not really meant to be used together in the way you have it configured.

Your mandrel appears to be an "adjustable mandrel" design based on the two nuts near the headstock. The mandrel shaft is held and centered by a collet that is part of the design. The intended purpose is so that you can avoid using spacer bushings by shortening the mandrel shaft.

The mandrel shaft itself appears to be a standard threaded mandrel shaft that uses a knurled knob. For these you should be using a standard 60-degree live center that mates up with a 60-degree dimple in the end of the threaded section. The live center and the dimple are what keep the mandrel centered and running true at the tailstock end.

With the mandrel saver, you should not have the brass knob and spacer bushing at the end of the mandrel. This will let more of the mandrel shaft (and not just the threads) go into the mandrel saver. The mandrel saver is drilled out so that a mandrel shaft will fit through it and will essentially run true because of the hole size relative to the mandrel shaft diameter.

In the configuration you have, it looks like the threads of the mandrel shaft go into the mandrel saver insead of the mandrel itself. The threads are likely a smaller diameter than the shaft and since the hole in the mandrel saver is made to fit the shaft, there is a sloppy fit, so the mandrel isn't being held centered in the mandrel saver. Since it is not concentric it is wobbling at the end of the mandrel.

Try this - Adjust the mandrel shaft so that it is long enough to accomodate the bushings and blanks while still leaving some of the shaft (not just the threads) extend past the last turning bushing. Without a spacer bushing and without the brass knob/nut, slide the mandrel into the hole in the mandrel saver and use pressure from the tailstock (mandrel saver) to apply pressure to the bushings and blanks for turning. This should keep your mandrel concentric and as short as possible.

So it looks like this:
View attachment 366440

An alternative would be to use the mandrel as you have it configured, but shorten it so that you don't need the spacer bushing at the end. Then replace your mandrel saver with a 60-degree live center that fits inside the 60-degree dimple in the end of the threads. You don't need to apply excessive pressure with the tailstock as it only needs to hold the mandrel to keep it centered. Excessive pressure can cause the mandrel to bend slightly which would show up as a wobble in the middle of the mandrel. - The mandrel saver is designed to prevent this excessive pressure and wobble in the middle, so I think the method above that ditches the spacer and brass nut would be the best case.

I hope this helps.
Dave

I'll try what you suggested, to shorten the mandrel. I'm just curious what you mentioned about not to use the the brass knobs at the end. Isn't that necessary? Without the brass knobs, I'm afraid the blanks will be loose , don't you think?

 

[YoYo]

While it may work for some, trying to make two parts equal on a lathe in the manner that you do will have its problems for sure. John is right on with his comments; YoYo is right, Dave is too. If you want both the same size, get a good set of calipers and learn to measure with a finer instrument than bushings, spacers and eyeballs. Bushings will wear down a smidgin EVERYtime you touch it accidentally with a sandpaper and or tool. Measure the fittings of the pen with a good set of calipers that measure to .005, or a much better set that measures to .0001 at least.

Measure the fittings of the pen, mark them down on a piece of paper or in a notebook. Turn the blanks to that size. When close and if you do use sandpaper or other sanding material use the fine to bring to size. Measure every minute or so until it is the right size.

This takes an extra minute or two for each blank, but you and any customer will feel the difference as they will be perfect.

And yes, you will have wobble in the way it is set up as it appears in the picture. Multiple parts pushed together like that are a recipe for trouble.

Thanks for your tips. But, most of the videos I saw on YouTube, they turn 2 blanks at the same time unless pen kits only need one blank like the cigar type. Also, I don't know why pens I turned are not smooth. Likely my hubby said, it's a failure. I wonder if the wobbling caused the uneven on the blanks. I can feel the bumps when I run my finger on the blank after finishing.

 

[jttheclockman]

Not to be contradictory because I bet there are many people who turn 2 blanks at a time. But when you say you can not get them even. That just is your technique then Look at your setup on this photo. You use 2 sets of bushings and each blank is turned to the bushing diameter. So you are not relying on one blank to turn the second one at all. Without the lathe running just slightly push in on the mandrel and if you see any and I mean any deflection in movement then what I am saying is true and it can account for out of round finished blanks. As far as speed that is not true. I can turn 2 separate blanks just as fast doing one at a time as you can doing 2 set up like that. remember it is not about speed it is about accuracy and selling a perfect product to the best of your ability. as far as lumps in the finish that is a different subject. That could be from your application of CA or finish of choice. You need to solve one problem at a time. The first is to see where the wobble is coming from. good luck.

 

[sorcerertd]

I've had that problem also. It's probably not the lathe itself. Many of us here are pretty picky about our work. Most pen turners out there probably turn multiple barrels just as you are doing here, and are happy enough with the results. Also, most of them are slightly, if not grossly, non-concentric. You will see the wood does not meet up with the kit parts as shown here. (I just grabbed a random pic from the internet of what I feel is a poorly made pen.) You can see the difference at the union of the barrel to the tip. The upper part of the union is smaller (overturned) than the tip piece, but the bottom looks even. There are other reasons this can happen, but the mandrel is the most likely cause.

To re-iterate earlier comments, that mandrel was meant to be used with a 60° live center. You will see a dimple in the end of the mandrel meant to meet up with this piece. You will find this much more stable, but do not over-tighten it or it will bend the mandrel. Once the mandrel is bent, there's really nothing that will give you an evenly carved barrel when using it. The hole in the mandrel saver is generally a little bigger than the mandrel, allowing it room to develop that wobble even if it's not bent. Also, as Dave mentioned, the threaded part is a bit narrower, but I find the fit to be slightly loose even with the mandrel properly inserted into the saver.

Shortening the mandrel by doing one barrel at a time will limit the wobble some. That's just a simple rule of physics.

Many of us turn "between centers" to take any mandrel problems completely out of the equation. If you search "TBC", you will find plenty of discussion on that. Below is my result using the TBC method. Many are able to achieve this using a mandrel, but I didn't want to spend money on a really good mandrel ($100-150ish) when TBC was an easy option for me. Even TBC will be a problem IF you don't have the ends of the barrel properly squared (trimmed).

As for it feeling rough, that could be dull tools or just not sanding down to a low enough grit. Those come with practice of both sharpening and sanding/finishing. Just keep turning and you will get this part fine tuned.

With all of that being said, don't overlook the simple thing that there may be some foreign matter in the morse taper. Make sure to clean that out, both inside the lathe shaft and on the mandrel. Even a small drop of glue will cause a problem there. I know this from my own experience.

 

[Gary Beasley]

I'll try what you suggested, to shorten the mandrel. I'm just curious what you mentioned about not to use the the brass knobs at the end. Isn't that necessary? Without the brass knobs, I'm afraid the blanks will be loose , don't you think?

The mandrel saver in the tailstock replaces the brass knob. You want to run the tailstock against the bushings firm enough to prevent them from slipping. Really dont need to shorten the mandrel as you need some length of unthreaded rod in the tailstock to hold it centered.

 

[RunnerVince]

It was really difficult mentally for me to switch to the TBC method, where you only do one barrel at a time. But I guarantee you will be pleased with the results if you follow the advice others have given in this thread and others on TBC.

It's really just a shift in perspective and adoption of a good pair of calipers. If I do spend more time now, it's negligible (maybe an extra 30 seconds to a minute taking one barrel off the lathe and putting the other on) compared to the increase in quality I immediately saw when I switched to TBC.

 

[jrista]

Folks,
Happy New Year! I haven't came here in long time. I hope everyone is doing well. I have a question, please take a look the attachment. Can you tell it's wobbling? Why? Thanks ?

View attachment 366439

Remove the knurled brass nut. Since you are using a mandrel saver, you shouldnt have the brass nut on there, the mandrel saver tailstock should be in direct contact with that last bushing.

If you continue to have wobbling issues, it may be that the mandrel saver itself has an issue. I've had one that had a very loose bearing, and it wobbled. Was one of the things that drove me to TBC turning, and I've never looked back.

 

[egnald]

I'll try what you suggested, to shorten the mandrel. I'm just curious what you mentioned about not to use the the brass knobs at the end. Isn't that necessary? Without the brass knobs, I'm afraid the blanks will be loose , don't you think?

The tailstock should provide enough pressure to keep the blanks from slipping on the mandrel shaft. If they slip then tighten the tailstock against them harder, but just until they stop slipping. This is the configuration I use all of the time.

Dave

 

[YoYo]

Not to be contradictory because I bet there are many people who turn 2 blanks at a time. But when you say you can not get them even. That just is your technique then Look at your setup on this photo. You use 2 sets of bushings and each blank is turned to the bushing diameter. So you are not relying on one blank to turn the second one at all. Without the lathe running just slightly push in on the mandrel and if you see any and I mean any deflection in movement then what I am saying is true and it can account for out of round finished blanks. As far as speed that is not true. I can turn 2 separate blanks just as fast doing one at a time as you can doing 2 set up like that. remember it is not about speed it is about accuracy and selling a perfect product to the best of your ability. as far as lumps in the finish that is a different subject. That could be from your application of CA or finish of choice. You need to solve one problem at a time. The first is to see where the wobble is coming from. good luck.

Understood ! I'm a rookie, still have a lot to learn.

 

[YoYo]

Remove the knurled brass nut. Since you are using a mandrel saver, you shouldnt have the brass nut on there, the mandrel saver tailstock should be in direct contact with that last bushing.

If you continue to have wobbling issues, it may be that the mandrel saver itself has an issue. I've had one that had a very loose bearing, and it wobbled. Was one of the things that drove me to TBC turning, and I've never looked back.

What is TBC turning? A website? Thanks.

 

[YoYo]

It was really difficult mentally for me to switch to the TBC method, where you only do one barrel at a time. But I guarantee you will be pleased with the results if you follow the advice others have given in this thread and others on TBC.

It's really just a shift in perspective and adoption of a good pair of calipers. If I do spend more time now, it's negligible (maybe an extra 30 seconds to a minute taking one barrel off the lathe and putting the other on) compared to the increase in quality I immediately saw when I switched to TBC.

You are another person mentioned TBC. How long have you been turning pen?

 

[d_bondi]

What is TBC turning? A website? Thanks.

TBC = Turn Between Centers

 

[egnald]

What is TBC turning? A website? Thanks.

As already mentioned, TBC means Turn Between Centers using a 60-degree dead center in the headstock and a 60-degree live center in the tailstock with no mandrel at all. Ed from Exotic Blanks has a video Link: Turning a pen "between centers" that shows the fundamental TBC process. There are also TBC methods that use special TBC bushings and some that use adapters along with standard bushings. - Dave

 

[leehljp]

I used the first TBC turning here on IAP back in 2008 (I think) for a specific reason. Only not knowing what to call it, I just used the term "Mandrelless". The earliest I can find is in March 2008.

I lived in Japan at the time and had access to a fair amount of ebony (oily dense heavy black persimmon).
Everytime I made a single barrel pen with that ebony, as soon as I pulled the bushings off, the CA finish would "lift" up off of the ebony on the ends. I asked for some help with a different method. Two members replied of a method they heard about in which the finishing is done without bushings and between the lathe head and tail stock (between the centers). That is about all that was said. I couldn't completely visualize it and started putting things together and it wound up working far better than I had experienced with a mandrel. By the fall of '08, it was a called TBC.

TBC does offer the potential for more precision in turning turning because it is very simple in its setup and less parts involved that can cause problems.

Dave gave an excellent link to a simple TBC setup.

 

[jrista]

What is TBC turning? A website? Thanks.

The web site TBCBushings.com sells bushings designed explicitly for TBC, which is Turning Between Centers. It a manner of turning pens that ditches the mandrel, and just puts each individual blank between two 60-degree centers (dead for the headstock, live for the tailstock). Some people do TBC with bushings, some just ditch the bushings entirely and put the brass tube directly between centers. Some, like myself, use a hybrid approach.

Regardless of the specifics, the general idea is that mandrels are often not perfect, most of the ones you get with a starter kit, or that you might buy from say PSI, are poor quality and often have bent shafts, or angled shafts (from the morse taper part that fits into the headstock), etc. and that often leads to the wobble you are experiencing.

Turning between centers means you no longer have a mandrel at all to deal with. If you use bushings from say TBCBushings.com (and there are some other sources), that are explicitly designed to be in direct contact with the 60 degree surface of your centers, then you can eliminate those sources of wobble. This then shifts the concern of proper configuration for optimal precision and accuracy from the mandrel to the lathe. Moving to TBC will generally right off the bat give you some improvements, but as you hone your craft you may find that you need to align your headstock, or tailstock, or both in order to eliminate any remaining issues (which are usually fairly small, but it can be a useful exercise over the long term to really dial it in).

Once your lather is fully dialed in, TBC can allow you to get extremely good precision with every turn. You can either do this with bushings, although to truly nail your results for every single kit, popping the bushings off and just putting the brass tube with its blank between the two centers on your lathe directly. Then doing your final passes or sanding with caliper measurements at each end of the blank (and comparing directly to the hardware of the kit you will be using with that blank) will give you the best possible match between blank and fittings.

 

[YoYo]

The web site TBCBushings.com sells bushings designed explicitly for TBC, which is Turning Between Centers. It a manner of turning pens that ditches the mandrel, and just puts each individual blank between two 60-degree centers (dead for the headstock, live for the tailstock). Some people do TBC with bushings, some just ditch the bushings entirely and put the brass tube directly between centers. Some, like myself, use a hybrid approach.

Regardless of the specifics, the general idea is that mandrels are often not perfect, most of the ones you get with a starter kit, or that you might buy from say PSI, are poor quality and often have bent shafts, or angled shafts (from the morse taper part that fits into the headstock), etc. and that often leads to the wobble you are experiencing.

Turning between centers means you no longer have a mandrel at all to deal with. If you use bushings from say TBCBushings.com (and there are some other sources), that are explicitly designed to be in direct contact with the 60 degree surface of your centers, then you can eliminate those sources of wobble. This then shifts the concern of proper configuration for optimal precision and accuracy from the mandrel to the lathe. Moving to TBC will generally right off the bat give you some improvements, but as you hone your craft you may find that you need to align your headstock, or tailstock, or both in order to eliminate any remaining issues (which are usually fairly small, but it can be a useful exercise over the long term to really dial it in).

Once your lather is fully dialed in, TBC can allow you to get extremely good precision with every turn. You can either do this with bushings, although to truly nail your results for every single kit, popping the bushings off and just putting the brass tube with its blank between the two centers on your lathe directly. Then doing your final passes or sanding with caliper measurements at each end of the blank (and comparing directly to the hardware of the kit you will be using with that blank) will give you the best possible match between blank and fittings.

Thanks for the information. Right after I posted my question on TBC, I went online and did some resear. Guess what? I ordered a 60 degree live center and received it yesterday.

 

[YoYo]

As already mentioned, TBC means Turn Between Centers using a 60-degree dead center in the headstock and a 60-degree live center in the tailstock with no mandrel at all. Ed from Exotic Blanks has a video Link: Turning a pen "between centers" that shows the fundamental TBC process. There are also TBC methods that use special TBC bushings and some that use adapters along with standard bushings. - Dave

Thank you very much for the link. I looked at the video, when I saw that was no mandrel, I almost have a heart attack. I think, my level is not there yet.

 

[egnald]

Thank you very much for the link. I looked at the video, when I saw that was no mandrel, I almost have a heart attack. I think, my level is not there yet.

I am not there yet either. I still use a mandrel and my configuration was very similar to yours, except for the spacer bushing and brass nut. - Dave

 

[TurnTheWorldAround]

I've had that problem also. It's probably not the lathe itself. Many of us here are pretty picky about our work. Most pen turners out there probably turn multiple barrels just as you are doing here, and are happy enough with the results. Also, most of them are slightly, if not grossly, non-concentric. You will see the wood does not meet up with the kit parts as shown here. (I just grabbed a random pic from the internet of what I feel is a poorly made pen.) You can see the difference at the union of the barrel to the tip. The upper part of the union is smaller (overturned) than the tip piece, but the bottom looks even. There are other reasons this can happen, but the mandrel is the most likely cause.

View attachment 366464

To re-iterate earlier comments, that mandrel was meant to be used with a 60° live center. You will see a dimple in the end of the mandrel meant to meet up with this piece. You will find this much more stable, but do not over-tighten it or it will bend the mandrel. Once the mandrel is bent, there's really nothing that will give you an evenly carved barrel when using it. The hole in the mandrel saver is generally a little bigger than the mandrel, allowing it room to develop that wobble even if it's not bent. Also, as Dave mentioned, the threaded part is a bit narrower, but I find the fit to be slightly loose even with the mandrel properly inserted into the saver.

View attachment 366462

Shortening the mandrel by doing one barrel at a time will limit the wobble some. That's just a simple rule of physics.

Many of us turn "between centers" to take any mandrel problems completely out of the equation. If you search "TBC", you will find plenty of discussion on that. Below is my result using the TBC method. Many are able to achieve this using a mandrel, but I didn't want to spend money on a really good mandrel ($100-150ish) when TBC was an easy option for me. Even TBC will be a problem IF you don't have the ends of the barrel properly squared (trimmed).

View attachment 366463

As for it feeling rough, that could be dull tools or just not sanding down to a low enough grit. Those come with practice of both sharpening and sanding/finishing. Just keep turning and you will get this part fine tuned.

With all of that being said, don't overlook the simple thing that there may be some foreign matter in the morse taper. Make sure to clean that out, both inside the lathe shaft and on the mandrel. Even a small drop of glue will cause a problem there. I know this from my own experience.

I can't agree more about Turning Between Centers (TBC) I have completely abandoned using a mandrel. My favorite is bushings with the 60 Degree taper on the inside of the bushing that fits between a dead and live center which has tremendously improved precision in turning my Pens. For bushings that don't have the tapper I have used this method which does fairly well https://www.pennstateind.com/store/PKMBCM2.html so mandrel bushings can be used between centers. I resist the urge to think that it will be quicker to have two blanks turning at the same time on a double mandrel the faster the process. Most times the slower more precise journey is the quicker path. I turn each piece separately for double piece pens.

 

[Kenobi]

There is a lot of reactions already, and I did read only like a half, so sorry if already said...The mandrel saver is mentioned to replace the brass nut to put pressures against the blanks without stretching the mandrel itself,this prevents bending. As I also have that mandrel type, important to mention is DO NOT OVERTIGHTEN THE NUTS THAT HOUSES THE COLETT, it causes the mandrel not to go straight then. And, I always turn both blanks at once, and I have two more advices here. First, do not use more bushings than 3 , no spacers. And second,when turning two blanks,its always the middle bushing that makes a mess. When getting towards the finishing cuts, stop and turn both blanks in different meanings a bit, do it like there or more times, to prevent the finished blanks to be off-center .