Out of round Statesman's

[Ryan]

All,

I have been fighting out of round Statesman's since the first one I made. I have done everything I can think of to keep it round on the tail end of the pen and nothing has worked. Since I live not too far from CSUSA I even took them into them to look at with my bushings thinking the bushings must not be square. We checked their display pens and found they had the same problem. Rex came down and looked at the problem and he discovered that the bushing is undersized. He said they would get some new bushings ordered to correct the problem. He said in the meantime just leave the tail end a little proud of the bushing. I said ok and went on my way.

The more I thought about the problem the more this did not make sense, because the blank fits perfectly on 2 sides of the pen and is proud on the other 2 sides. This tells me it is out of round. I started to rotate the blank a half turn just before the final cuts and this seemed to help a little but did not solve the problem.

This weekend I was gearing up for Christmas and while working on some Statesman’s again I think I found the problem. I do not think it is the bushings as stated. I looked at my mandrel and found that the bushing sits on the threads of the mandrel causing quite a bit of play. As I tighten the nut it is pulling the bushing to where ever causing it to be off center.

So now that I have been long winded the short version is: The mandrel seems to be too short for the larger pens.

Can anyone else confirm this for me?? I REALLY want to get this solved. Aslo let me know if anyone else is having the same problems.

Thanks,
Ryan

 

[ed4copies]

Ryan,

Turn one half at a time, always using the side toward your head-stock. Your tail stock is probably off center-I am using a double thickness of sandpaper to support the front of my tailstock to keep it "in-round". But on really good pens, I use a short mandrel and turn one half at a time.

Not a great answer, but it works.

 

[Ron Mc]

Ryan,
Interesting that you would bring this up. I have been fighting this type of issue with several pen styles. About 2 weeks ago I noticed a slight wobble on the tail stock side of my mandrel. I turned the lathe off and turned the blank and tried again and the wobble was still there. The strange thing was it is only showing at the tail side and not anywhere else. I use an adjustable mandrel so I pulled the mandrel and checked it and it isn't bent. I then put the mandrel back and only put one blank on and I'll be darned if the wobble was still there. I purchased 2 new mandrels a totally different mandrel set up and tried all of them. It's still there. I notice it because the knurled brass nut makes it obvious. I am starting to believe that possibly the threads on the inside of the latest runs of brass nuts are crooked or the threads are the mandrel have an issue.
To date I have not solved the problem and will continue to look for answers. BTW. I have the problem on both of my lathes. Very strange.
If you have a chance the next time you start a pen could you look at the brass nut to see if yours spins straight?
Thanks,

 

[woodscavenger]

Ed has the right idea. For the pens that is really makes a difference for I too do one blank at a time so I can keep it near the headstock. I think I am eventually going to get one of the collet chuck systems.

 

[alamocdc]

Ryan, I had the same problem w/my Perfect Fits on the "B" mandrel. It's about 1/4" too short and this small amount throws the last bushing out of kilter just enough to screw things up. That's what I get for not ordering the new custom made "B" madrel that some of our members got going some time back. [!] In the mean time, Ed's solution is the best one.

 

[Ryan]

Originally posted by Ron Mc
<br />Ryan,
Interesting that you would bring this up. I have been fighting this type of issue with several pen styles. About 2 weeks ago I noticed a slight wobble on the tail stock side of my mandrel. I turned the lathe off and turned the blank and tried again and the wobble was still there. The strange thing was it is only showing at the tail side and not anywhere else. I use an adjustable mandrel so I pulled the mandrel and checked it and it isn't bent. I then put the mandrel back and only put one blank on and I'll be darned if the wobble was still there. I purchased 2 new mandrels a totally different mandrel set up and tried all of them. It's still there. I notice it because the knurled brass nut makes it obvious. I am starting to believe that possibly the threads on the inside of the latest runs of brass nuts are crooked or the threads are the mandrel have an issue.
To date I have not solved the problem and will continue to look for answers. BTW. I have the problem on both of my lathes. Very strange.
If you have a chance the next time you start a pen could you look at the brass nut to see if yours spins straight?
Thanks,

Ron,

My brass nut does not spin true. This is how I have been noticing the problem as well. What I have noticed is if I put the nut on and not the blanks it will spin true. When I put the blanks and the bushings on it does not. I think it has something to do with when they cut the treads some of the metal was removed and now there is slop in the bushing. When everything is on there and it spins up the slop is taken out and it finds it own center.

I have thought of having a local machine shop make a one piece mandrel for me. I know this could be expensive, but if the longer mandrel I am going to try does not work then I am going to make it happen. I am tired of fooling around with it.

Ryan

 

[Ryan]

ED,

I have turned 1 section at a time and it does help, but it slows things down and I do not get to see the shape of the whole pen at the same time which I like doing.

I have checked the tailstock and it matches the headstock perfectly point to point.

Thanks for the idea's,

Ryan

 

[Rudy Vey]

I had similar problems with three different lathes (that all were fine-tuned and head and tail stock in perfect alignment). I think a couple things are playing a role here, and if they come all together, the effect is more visible.
For me the most adding factor is that the blanks is not square to the bushing. If the blanks is just a smidgen off out of square, it will shift slightly when the nut is also only very lightly tightened. I do not use the large brass nuts, just normal hex nuts that I finger tighten. I also have added spring washers between the last bushing and the nut. Sometimes the centrifugal forces have the tendency to tighten the nut more then it should be.

Secondly, mandrel flex. The longer the mandrel the more it flexes when the lathe spins very fast and you then put your tool to the blank, making things worse.

Thirdly, wood density. Some woods are more hard then others, worst are burls that can have different densities within one blank. Harder wood needs sharper tools and when the shaving not fly as on other woods, some people (me included) have the tendency to press a bit harder and then comes factor #2 in again.


What can be done to over come "out of round" pens:
If you can, turn single barrels, means less length of mandrel means less flex. A collet chuck that allows for the mandrel adjustment was one of my biggest improvement. Sharp tools, this is pretty clear and does need any more clarification. Thirdly, what I do sometimes is to rough turn the blanks round within about 1/16" of the final diameter, then I loosen the nut, rotate the blanks against the bushings slightly (about 1/4 - 1/2 turn), then finger-tighten the nut and finish turn. This last finish turning has only a very light touch towards the wood. Also, when sanding, light touch is the word.
And the most important is a square blank, sharp pen mill or what ever one uses. I found out that for pens that can be either turned with a short upper barrel (American Flattop, Perfect Fit etc. from Berea) or with a long barrel, but then one needs to cut exactly the length and down to the brass, that the latter gives you better square results since one can easily square the blank before turning. Squaring a short cut blank with the brass tube sticking out is nearly impossible, and drill holes are very often not square either.

 

[dfurlano]

I now usually put a dial indicator on the mandrel before I start my finish turning. I find that mandrels have what I call "multi-stable shapes". The mandrel will spin tru but when either a large force or specific vibration can cause it to deform or go out of round. I place the tip of the indicator on the bushing.

The best I have seen a mandrel turn is with about 2-3 thousands run out. I would also suspect that this situation is very dependent upon the force of the tall stock on the mandrel. I have been thinking that it may be better to chuck the mandrel in the tail stock with a mini self centering chuck that I have.

Using a live center in the tail stock is not consistent or reliable in mho.

 

[Daniel]

Since I have always had an out of round problem with my lathe at the tail stock end, I have always been int he habit of turning the blank for the final cuts. one thing that stuck out to me in the original statment was.
"I started to rotate the blank a half turn just before the final cuts and this seemed to help a little but did not solve the problem."
If you really turned it a half turn you simply swapped the high sides for each other. A quarter turn may help more than what you have been getting.
now that si only a band aid fix anyway.
sound to me that the thread thing may be the problem. I have a brass nut that actually wore a groove in it from the bushings. long storry but it woudl get over tightened while turning the pen. problem was it di dnot wear the brass dead center and was doing the same thign you are talking about here. it woudl push the bushing off to one side jsut a bit. this of set has the additional effect of doubling how far out of round the finished pen is. the final answer I found for my lathe is to have a small but more accurate lathe to do the final sanding and finishing on. this has worked very well for me but the small lathe also cost me four times as much as my larger lathe did. my statesmans are round though.

 

[dfurlano]

Now this is a very interesting concept! Although I think it is way over priced. This looks like something that can be retrofitted without to much trouble.

http://www.fholder.com/Woodturning/product7.htm

 

[TomServo]

I think I can make something like this with my Taig lathe - all I really need is a ball bearing center with a 3/8-24 thread for a drill chuck. If the adapter were to thread onto 3/8-24 then I could simply attach it to the standard chuck adaptor. I'll have to think on how I can make one. After that, we would just need appropriately sized pieces of drill rod (hss is nice and ridgid). Most tailstocks could pull as easily as push, but those with MT tailstocks would need thru-tailstock capability.

Enjoy my paint skills:

feel free to shoot my idea down, but this wouldn't be impossible to make (i'm going to try, i think)

edit: come to think of it, you could loctite RC the chuck holder into the bearings, ie turn the rod down to 5/16" and use 5/16" ID bearings and loctite rc the rod into the inner races. You could probably use a 3/8-24 bolt and cut off the head and find bearings that it fit snugly in. If the bearings ever go bad, it would be cost effective to simply replace the bolt and the bearings. The PITA part for most is the aluminum housing.

 

[Fred in NC]

Right Tom, Very right .... excellent design.

You can also buy it ("Rotating Drill Chuck") from Little Machine Shop. Expensive, but ready to go.

The live center itself is often the culprit. The live center that comes with wood lathes is not the right one for pen turning. The hole in the end of the mandrel has a 60 degree included angle, and the live center has to have the same angle. I use a machinist's live center from LittleMachineShop.com. The best one for this is the cheaper one too, about $12.

 

[TomServo]

I came up with a more simplified design... I think there are some aluminum sockets at a nearby surplus store that may work. I definitely want to try making one of these.

 

[Fred in NC]

I think we are trying to reinvent the wheel !!

 

[mschem]

Fred-

I've certainly noticed the negative effects of mismatched angles. Over time, either the end of the mandrel or the point on the center shows clear evidence of wear. I suspect which one wears is dependent on which is the softer metal.

Can one pretty much use any machinist live center? Is a 60 degree angle "standard" in metal work or does one need to check each specific center? I notice that LittleMachineShop.com does not explicitly say the $12.95 model (PN 1189) has a 60 degree angle. Is this the one you were referring to?

Thanks for any help.
Mark

 

[Fred in NC]

Mark: the $12.95 model (PN 1189) is what I use, both in metal and wood lathes. I have a couple of them. The point is 60 deg included angle. That is the common angle of machinist's live centers.

Included angle is measured from one side to the other, what you would get if you used a protractor.

Also, most center drills have the same 60 deg angle. I find them very useful too: it drills a hole that is a perfect match to the live center. Very good also to get holes started when the stock does not behave properly, since they don't flex and have a tiny point to start the hole. LMS sells a set of five for about $5. AND I use them a lot!

The heavier duty live centers are too long, and too heavy for use with a mandrel.

 

[Mikey]

Another thought... I found last night that some bushings slide easily on to the mandrel, and can move a few thousandths around on the mandrel. I figured out that some bushings were worse than others because I got a set of snug fitting Baron bushings that yielded a perfect pen with no fuss.

 

[Randy_]

Mark: I also bought one of those 12 dollar live centers from the Little Machine Shop. I think Fred pointed me in that direction a year or so ago when I was struggling with a worn LC tip. It has worked very well for me.....an excellent investment!!!

You/I would think that all of the people who sell pen kits/mandrels would make this information known; but they don't, for the most part. I just bought what must be my hundredth kit recently and saw, for the "FIRST" time, mention of the need for a 60° live center. Can't remember for sure; but I think it was in the instructions for a kit that I bought from BB.

 

[Thumbs]

Knotty Harry was telling me I should replace my current live center tailstock with one of these better ones, too. I guess I should have listened to him! Guess who just just placed his order with The Little Machine Shop?[]

 

[TomServo]

Be sure and let us know how it goes - I myself am using a dead center held in my
drill chuck (I still have to order the live center). I made the center out of a
piece of brass rod and lubricate with synthetic grease. I thought I'd matched up
the angle well enough but I'll double check that too. I'll make a 60 deg angle on
a sheet of paper and compare. Alternatively, do we want the point to hold the
center, or for the angles to sit flush against each other? I still like the idea
of holding the rod in tension, as it'd help prevent center wobble and help keep
the rod from shifting. Next paycheck I'll work on the concept and report back
I love a good, useless yet potentially useful project.

 

[Mikey]

The 60* live center ensures that the point of the center does not bottom out in the hole of the mandrel. If the pont bottoms out, it may walk or deflect a little. With the 60*, it contacts the sides, making the mandrel more stable.

This is a problem I had with mine. When I first started making pens, I was having wobble problems. the guys at Woodcraft immediately told me I needed to grind the sharp tip off the center. Things turn out much better now.

 

[KenV]

The "mizer rest" would be to put a 0.250 sealed bearing on the shaft and adjust a "steady" block against it from the back. Bearings are a buck or two. The bearing would present another item to avoid with the tooling, and will occupy about 1/4 inch of mandrell capacity. It certainly would cut the flex and deflection of the mandrel by cutting the l/d ratio in half.

A block of uhmd plastic or a dense wood against the bearing should work.

Will have to see if I can mock this up.....

 

[KenV]

The "mizer rest" would be to put a 0.250 sealed bearing on the shaft and adjust a "steady" block against it from the back. Bearings are a buck or two. The bearing would present another item to avoid with the tooling, and will occupy about 1/4 inch of mandrell capacity. It certainly would cut the flex and deflection of the mandrel by cutting the l/d ratio in half.

A block of uhmd plastic or a dense wood against the bearing should work.

Will have to see if I can mock this up.....