Disappointment = Learning

[Pjohnson]

I have been humming along making several Sierra kits that I purchased from Timberbits. All has been going great - the kits are great. my blanks have been a combination of either wood, segments, or self poured acrylics.

A pen or two ago I noticed two things:
- I need a small wrench to loosen the brass knurl on the mandrel. It wasn't that tight when I first put it on.
- The blanks are out of round at the bushing at one end when finished turning

My setup:
- Pen mandrel, Sierra bushing, blank, Sierra bushing, wood spacer, brass knurl
- the nib end of the pen is always on the right end

Hypothesis:
The spacer has developed a slant on the end that butts against the bushing. When I realized it was out of round, I replaced the wood spacer with several 7mm bushings. To maintain more control I sanded the blank as opposed to touching it with the gouge or skew. It got closer to round within a level of tolerance.

Learning:
Ditch the wood spacer - use bushings to make up the spacing.

Interested in your thoughts ...

Thanks

PJ

 

[longbeard]

Ditch the madrel and turn between centers. If you cant get TBC bushings, you can use the factory ones. I only use the bushings for a reference, turn the blank down very close to final size and then use a mic to get the final size. Hope this helps and makes sense.

I should also mention that when i get close to final size WITH the bushings, i then remove the bushings, put the blank between the centers and finish to size that way

 

[Tom T]

I use WC slim line bushing. One or two depending.
They work every time and they are cheap.
My two cents.
I would like to turn with out bushing TBC but can seem to get the bushing I need.

 

[Jim Burr]

Ditch the madrel and turn between centers

Yup...+1

 

[longbeard]

I use WC slim line bushing. One or two depending.
They work every time and they are cheap.
My two cents.
I would like to turn with out bushing TBC but can seem to get the bushing I need.

You can use the factory bushings to a point, (dont rely on them being perfectly round) then remove them as i mentioned above. I have few kits that i dont have TBC for and this what i do.

 

[its_virgil]

Get an adjustable mandrel and ditch all of the spacers.
Do a good turn daily!
Don

 

[Tom T]

Harry,
I have tried the factory ones. Could not get them to work. Do I need to do something to the ends. I do not have a metal lathe. I can not get the pen blank to turn well it spins until I put a tool on it then it stays in place and the ends turn on the 60 degree center.

 

[longbeard]

Get an adjustable mandrel and ditch all of the spacers.
Do a good turn daily!
Don

Not saying they dont work, just dont work for me personally, i get some chatter with mine. So now i only use it for when i want to paint the tubes.

 

[Pjohnson]

Thank you for the thoughts. The bushings are a ballpark guide for me. i do not use them as the final measure. Once I get close, I rely on the calipers.

Would 60 degree bushings work for all kits?

 

[longbeard]

Harry,
I have tried the factory ones. Could not get them to work. Do I need to do something to the ends. I do not have a metal lathe. I can not get the pen blank to turn well it spins until I put a tool on it then it stays in place and the ends turn on the 60 degree center.

May tighten your tail stock up just bit. Some will use a counter sink bit to make a 60 degree shoulder on the factory bushings. I haven't found that necessary yet.

 

[longbeard]

Would 60 degree bushings work for all kits?[/QUOTE]


What do you mean?

 

[Pjohnson]

Sorry for not being clear ...

If i had 60 degree bushings ... can they be used on all size tubes, thus eliminating the need for kit specific bushings?

A trip to the library may be in order to learn about turning between centers.

 

[longbeard]

Turning between centers. You need a 60 degree drive center and 60 degree live center. About 30 bucks for both. The TBC bushings have 60 degree shoulder. You would have your blank with the proper bushing in each end then mount between centers. Hope that made sense.

You need kit specific bushings, although some bushings fits other kits.

 

[1080Wayne]

I turn everything between my 60 degree drive and live centers without bushings , relying solely on a caliper for sizing .

 

[tim self]

Ditch the madrel and turn between centers. If you cant get TBC bushings, you can use the factory ones. I only use the bushings for a reference, turn the blank down very close to final size and then use a mic to get the final size. Hope this helps and makes sense.

I should also mention that when i get close to final size WITH the bushings, i then remove the bushings, put the blank between the centers and finish to size that way

You're doing it EXACTLY like I do. No more out of round!!! I also square close to finish, turn round by that axis, then square exact with my collet before turning. May be a bit anal but my way and I like it.

 

[shortz1lla]

Since no one has addressed this yet, just based on the mandrel you're using, I would recommend turning your blanks with the nib end towards the headstock. I've never used the "standard mandrel" as I started out with a mandrel saver from PSI (love it), but I've read many times over on this site that most OOR incidents occur on the knurled nut end of things.... so even if it doesn't turn out perfect, the nib to blank transition should be smoother. I'm a major proponent of the mandrel saver, though. The only spacers you have to use are the actual bushings used for holding the blank and you tighten it up by engaging your tailstock, fast and simple as can be. I hope you get this figured out.

 

[Charlie_W]

I use TBC bushings as well for all I can. I CA between centers only...no bushings at all at this point.
One item not mentioned earlier was changing from a standard mandrel to an adjustable mandrel. Shorter rod = less deflection.
I have a mandrel saver as well. It has just a little play between the mandrel and the ID of the mandrel saver...just another place to get out of round pens.
TBC bushings or totally between centers is best for getting the best fit between blank and pen hardware.

 

[Dan Masshardt]

I turn between centers as well.

But another option is a mandrel rod in a collet chuck. Obviously fully adjustable.

I happen to have liked the mandrel saver as well when I was using a mandrel. Also no spacers etc needed.

 

[Justturnin]

If you want to keep the mandrel, and there is nothing wrong with that, you can do like Don said and get an adjustable mandrel or a mandrel saver from PSI. I used the saver when I was turning on a mandrel and it worked great. The trick is one part at a time. if you put both pieces of a two part of a two piece pen you increase the chance of the mandrel flexing in the middle. Do one part at a time and it will use less mandrel and it will be stronger. I do TBC now but not because the mandrel was not giving me the results but because it is faster to remove the pen from the lathe and measure w/ my calipers. Once you are getting close you should be measuring often.