0 for 3 :(

[rick_lindsey]

Whee! Had what started out as a fruitful session in the shop this eve. Another member of the woodchippers club wanted to see what pen turning was all about, so after I gave him the "keep your salt shaker handy because I'm almost as new at this as you are" spiel we proceeded with the blind leading the blind . We cut, drilled, tubed, and milled an african mahogany blank for him, and I gave him my leftover walnut "practice blank" that had been given to me by another turner in the club. Then I turned my third cocobola Euro blank. It turned out reasonably well, sanded up through the micromesh and did the friction polish thing.

Unfortunately I'm still getting an out-of-round condition, and it was especially exagerated at the nib end (furthest from the headstock). I tried to get the mandrel turning as true as I could but apparently to no avail . To add insult to injury I think I cracked the lower barrel during assembly (the nib didn't want to go on straight at first, but i didn't notice the crack until later)

I was planning to go short-mandrel and turn one barrel at a time, but I wanted to show the new guy what I'd already tried, rather than break new ground... guess I should have stuck with my original plan and used the short mandrel!

I'm starting to wonder how to make/get some bushings to turn between centers on the cheap... I was wondering if you could find a steel tubing that was a snug fit into the 7mm brass tube (which hopefuly would also be a snug fit into the bushings), and just glue a bushing to one end of a ~1" tube? I'd need another set of euro bushings since i'd need two center ones (one for each direction). It might be reasonbly easy to just put a piece of wood on the end for the bushing to hit though so I could turn the bushings around, or slip the bushings from whatever kit i'm turning onto the steel tubes, which then slip into the 7mm tube in the barrel, and the whole contraption gets compressed between dead and live centers?

Also, what's the best way to salvage the transmission and nib? I'm thinking I can just keep the top barrel and maybe turn a new bottom barrel for it, if I can salvage the kit pieces.

anyhow, thanks for listening to me whine and ramble

-Rick

 

[Robert Taylor]

disassembly is not very difficult. check this thread, look at post #5 by cav

http://www.penturners.org/forum/showthread.php?t=39092&highlight=disassembly

then you can turn the bad/cracked wood down to the tube if you don't have a spare.

 

[alphageek]

Unfortunately I'm still getting an out-of-round condition, and it was especially exagerated at the nib end (furthest from the headstock).
-Rick

I usually turn 'short mandrel'.... And since the nib end is in the persons fingers and thus needs to be most accurate, I always try to have that end at the headstock. Is there a specific reason you put the nib at the tailstock end?

 

[rick_lindsey]

Thanks for the link, Bob. I'll go check that out and hopefully salvage my kit! I need to pick up more brass anyways so i'm less worried about saving that.

Alphageek -- I was simply following the directions... they say to load the big bushing, the short blank, the step bushing, the long blank, and finally the little bushing. In the future I'll be doing short (or no) mandrel turning only, and I think I'll adopt your plan of putting the nib end at the headstock!

-Rick (who after only 4 pen attempts is already tired of OOR)

 

[jttheclockman]

Bent mandrels will give an out of round blank as well as tightening the nut too tight which will bend the mandrel. Barry Gross once mentioned at one of his shows that one way to eliminate out of round blanks is to rotate the blank about 90 degree just before final skew work. Does it work I do not know I never tried it but does make sense.

 

[marcruby]

Short mandrel is ok (I still use it myself where I don't have mandrel-less bushings BUT, if the mandrel is bent enough it's going to turn out of round no matter what you do.

Marc

 

[leehljp]

It sounds a little like it might be the live center that is made for wood turning instead of a 60° live center. A wood turning live center will cause what you were describing. Just remember - the mandrel is metal, not wood, and therefore needs a different LC than normal wood turning does.

 

[rick_lindsey]

Quite possible, Lee. It's club equipment, and i'm not entirely sure what sort of live center we have. If I turn between centers does the angle of the live center still matter?

-Rick

 

[leehljp]

Quite possible, Lee. It's club equipment, and i'm not entirely sure what sort of live center we have. If I turn between centers does the angle of the live center still matter?

-Rick

Turn between centers - it doesn't matter.

Concerning the suggestion of too tight on the mandrel above, If a blank is not squared correctly or a tube/bushing is jammed, it can cause the OOR, but tightening the nut too tight itself will not cause the mandrel to bend. Tightening the tail stock too tight on a mandrel can cause it to bend.

 

[rick_lindsey]

The mandrel was wobbling slightly around the live center when I spun it by hand -- I tried to straighten it as much as possible before I started turning, but apparently to no avail. I was using a pen mill on the blanks, so I'd hope they were square. Our drill press leaves much to be desired, and our belt sander isn't set up right now in a manner that makes squaring the blanks that way feasible. I'm pretty sure i'm not overtightening the tailstock. I generally make it just barely touch, turn on the lathe, and tighten it very slowly until it starts to spin with the mandrel.

-Rick

 

[jhs494]

Unfortunately I'm still getting an out-of-round condition, and it was especially exagerated at the nib end (furthest from the headstock). I tried to get the mandrel turning as true as I could but apparently to no avail . -Rick

Rick,
Are you using the tailstock center that came with your wood lathe?
If so most are the incorrect angle to mate with the mandrel.
You will need a 60˚ angle on the point to match the angle that is in the mandrel.
Most wood lathe come with a center that is not intended to match this degree of angle and are meant to just be pushed into the wood.
This might help with some of your out-of-roundness.
Good Luck!

 

[lwalden]

While I agree with Lee that the angle doesn't matter when turning between centers, in some cases the live center that comes with a mini/midi lathe won't work since it has a small point, then a bit of a hollow area and a shoulder that doesn't sit very far back from the point- so there is not a good contact surface, especially on larger tubes, using the stock live center.

Turn between centers - it doesn't matter.

Concerning the suggestion of too tight on the mandrel above, If a blank is not squared correctly or a tube/bushing is jammed, it can cause the OOR, but tightening the nut too tight itself will not cause the mandrel to bend. Tightening the tail stock too tight on a mandrel can cause it to bend.

 

[leehljp]

While I agree with Lee that the angle doesn't matter when turning between centers, in some cases the live center that comes with a mini/midi lathe won't work since it has a small point, then a bit of a hollow area and a shoulder that doesn't sit very far back from the point- so there is not a good contact surface, especially on larger tubes, using the stock live center.

What Lyle said is correct. There are a few live centers with small points that will not fit correctly on larger tubes. The more common or ordinary live centers should work.

 

[rick_lindsey]

I put both dead and live centers from Victor on my christmas list... I'll have to buy myself a dead center at least if I don't get one for christmas .

Our live center is shaped kind of like a "W" with the center point sticking out further than the rest. I'm going to check the other lathe today to see if it has a better live center for the pen mandrel.

-Rick

 

[Blind_Squirrel]

Bent mandrels will give an out of round blank as well as tightening the nut too tight which will bend the mandrel. Barry Gross once mentioned at one of his shows that one way to eliminate out of round blanks is to rotate the blank about 90 degree just before final skew work. Does it work I do not know I never tried it but does make sense.

Please explain to me how tightening the nut will bend the mandrel. Think of the mandrel as being a piece of string. The tighter you pull on a string that has been affixed on one side the straighter it gets. Tightening the nut should actually help to straighten the mandrel.

I do not recommend over tightening the nut for other reasons, but not because it will bend the mandrel.

 

[byounghusband]

Please explain to me how tightening the nut will bend the mandrel. Think of the mandrel as being a piece of string. The tighter you pull on a string that has been affixed on one side the straighter it gets. Tightening the nut should actually help to straighten the mandrel.

I do not recommend over tightening the nut for other reasons, but not because it will bend the mandrel.

Scott,
Your mandrel is not like a piece of string IMHO. You are not pulling anything when you tighten the nut like you are when pulling the ends in opposite directions.
Tighntening the nut is compressing everything betwen the nut and the other end of the mandrel. By surpassing the necessary force needed to hold everything tight, you are, in effect, trying to force a longer rod (mandrel) into a shorter space and it has to deflect to compensate, thus bending.
If there was a way to keep the nut in the same horizontal plain (Stationary side to side) then you would straighten the mandrel road as you stated earlier.

My suggestion would be to get a 60* live center.

Put the blanks on the mandrel, put the nut on and turn it until it contacts the bushing, bring the tailstock up and turn the lathe on and get the live center spinning with the mandrel bit cranking it in a touch. Then stop the lathe and firm up the nut on the mandrel.
That's teh way I do it now and OOR problems have gone away....

 

[rick_lindsey]

I found the 60deg live center today! *yay* but I can't get the old livecenter out . I tried the little knobbed rod that knocks out whatever is in the headstock, but it just bottoms out in the tailstock. It looks like it should have gone plenty far enough to knock out the live center though, which makes me wonder if it's hollow? I wasn't able to find a longer rod, but I may just pick something up at the hardware store.

As far as mandrel compression, I think the mandrel itself is getting stretched isn't it? Tightening the nut effectively shortens the mandrel, which in turn compresses the blank and bushings (with a corresponding tension on the mandrel).

-Rick

 

[byounghusband]

As far as mandrel compression, I think the mandrel itself is getting stretched isn't it? Tightening the nut effectively shortens the mandrel, which in turn compresses the blank and bushings (with a corresponding tension on the mandrel).

-Rick

Rick,
Yes, I believe you are correct, now that I thinhk about it. :redface:

The Mandrel is stretched, but since the space between the nut and the headstock end are getting smaller, it would be the blank and bushings that must deflect.... Thanks for the correction.

 

[Blind_Squirrel]

Another tip to help keep things round:

I use a bushing for my pen mill on all of my larger tubed pens. I leave the bushing inside the tube while turning. This helps reduce/eliminate any flex the tube might encounter from pressure of tools being applied while turning.

 

[rick_lindsey]

Ooh, thanks for the tip Scott. I have a Classic American Fountain Pen kit and bushings waiting for after the holidays... my wife wants a purpleheart fountain pen . I believe it has larger tubes, and while I don't have a pen mill bushing, I might just have to turn an "insert" using a spare 7mm tube....

-Rick

 

[Blind_Squirrel]

Ooh, thanks for the tip Scott. I have a Classic American Fountain Pen kit and bushings waiting for after the holidays... my wife wants a purpleheart fountain pen . I believe it has larger tubes, and while I don't have a pen mill bushing, I might just have to turn an "insert" using a spare 7mm tube....

-Rick

I now have a mini metal lathe and turn my bushings from aluminum (my tolerances are so tight they *pop* when I remove them if I hold my finger over one end of the pen tube :biggrin . Before I got the metal lathe I used acrylic to make my bushings. I tried 7mm tubes and wood, but found it would swell and contract too much for my tastes.