Common practice re: CA build up

[jbg230]

I haven't seen anything real specific about this, but as I have started to pay attention to more detail, I'm wondering what those with more experience do regarding the build up of CA at turned portion of the nib and cap ends of the blank during the finishing process.

I'm wondering how thick a layer of thin CA is and how thick a layer of medium CA is. That would certainly help, but I'm sure that's an unfair question since there's so many variables. So my bottom line question is if it's common to turn a little bit further past the bushings, to compensate for the extra thickness of the final CA layers. And if so, how much further past the bushings?

I use a small piece of 400 grit sandpaper on a flat section of the lathe to sand down the build up of extra CA at the open ends of the finished blanks, but it's the build up of CA on the turned nib and cap ends that is the frustration. Just when you think I'm done, I find I have to put the blank back on the mandrel and turn down the ends with a tiny piece of 600 grit and re-polish. I'm not sure if it'd be worse trying to compensate by "over turning" those ends and "build up" to the bushing with the CA.

 

[Dehn0045]

So my bottom line question is if it's common to turn a little bit further past the bushings, to compensate for the extra thickness of the final CA layers. And if so, how much further past the bushings?

Yes. I personally turn to a diameter that is 0.005 to 0.010 inch less than the component diameter (when doing a CA finish). This means that the final CA thickness is 0.0025 to 0.005 after the finish is complete. I shoot for a build-up that is about 0.002 greater than the final diameter and then remove the excess with a sharp skew using a scraping cut. I find the skew gives me better control than sandpaper. I can then go through the micromesh skipping the first few grits as the skew leaves a very smooth finish, polishing will remove some material but if I'm careful it is usually less than 0.0005.

Also, there really isn't a "normal" thickness of a coat of CA. I can apply a single coat of thin CA and gain anywhere from 0.0002 (estimated) or as much as 0.0015 or so in diameter. I usually gain about 0.001 and use only thin, but this is obviously very dependent on method.

 

[Curly]

If you were to use a buffer the ends get a slight radius on them and the oversize isn't felt or seen when looking or handling the pen. Different story with doing all the polishing on the lathe.

 

[wouldentu2?]

If you were to use a buffer the ends get a slight radius on them and the oversize isn't felt or seen when looking or handling the pen. Different story with doing all the polishing on the lathe.

I was going to make the same comment, simple procedure with great results.

 

[leehljp]

Build-up on the ends is more or less practice and skill that comes from experience over time. I use a margarine tops cut into 1" or 1 1/4" squares and use that to wipe the CA from end to end. Being a bit firm, it moves the CA and I can easily control any excess build up on the ends. My method doesn't have to be yours by any means. Find a way to move the some of the CA more to the center and away from the ends before it sets. It doesn't really matter if it is thin, medium or thick; the process is the same.

You can control the build up much better if you use TBC or the Mandrel Saver. The mandrel saver has or uses a cone shaped bushing to butt up against the blank when you finish it; the TBC does not use a mandrel, but uses the centers (head stock and live center) do the same as the cone shaped bushing on the mandrel saver. Use calipers to measure to size, not bushings. Bushings are better to use to turn close to size, then move to the TBC or Mandrel Saver for finishing sizing and applying the CA finish. However, for sizing, use calipers to measure your fittings nose cone, center band and clip end, then turn the blank to those measurements or .005 less than and build up the CA on the Mandrel Saver or TBC.

This prevents CA from building up on the bushings. Actually, TBC (Turning Between Centers) and the Mandrel Saver came into being because of the heavy build up of CA on bushings, and both methods prevent that.

 

[mnerland]

Build-up on the ends is more or less practice and skill that comes from experience over time. I use a margarine tops cut into 1" or 1 1/4" squares and use that to wipe the CA from end to end. Being a bit firm, it moves the CA and I can easily control any excess build up on the ends. My method doesn't have to be yours by any means. Find a way to move the some of the CA more to the center and away from the ends before it sets. It doesn't really matter if it is thin, medium or thick; the process is the same.

You can control the build up much better if you use TBC or the Mandrel Saver. The mandrel saver has or uses a cone shaped bushing to butt up against the blank when you finish it; the TBC does not use a mandrel, but uses the centers (head stock and live center) do the same as the cone shaped bushing on the mandrel saver. Use calipers to measure to size, not bushings. Bushings are better to use to turn close to size, then move to the TBC or Mandrel Saver for finishing sizing and applying the CA finish. However, for sizing, use calipers to measure your fittings nose cone, center band and clip end, then turn the blank to those measurements or .005 less than and build up the CA on the Mandrel Saver or TBC.

This prevents CA from building up on the bushings. Actually, TBC (Turning Between Centers) and the Mandrel Saver came into being because of the heavy build up of CA on bushings, and both methods prevent that.

Lee,
Maybe a confusion on terms here. I believe the Mandrel Saver was designed to "save the Mandrel" from being bent or warped with too much pressure applied from the tailstock live center on a standard mandrel. I use the cone shaped "non-stick" bushings to finish and they work just as well on a standard mandrel setup or a Mandrel Saver. I learned real quick to buy these after trying to break off my metal bushings after a CA finish. With these in use, I don't really have the CA build up problem described.

 

[leehljp]

Lee,
Maybe a confusion on terms here. I believe the Mandrel Saver was designed to "save the Mandrel" from being bent or warped with too much pressure applied from the tailstock live center on a standard mandrel. I use the cone shaped "non-stick" bushings to finish and they work just as well on a standard mandrel setup or a Mandrel Saver. I learned real quick to buy these after trying to break off my metal bushings after a CA finish. With these in use, I don't really have the CA build up problem described.

An overview of the chronological history and therefore the purpose:

That is part of the reason, but there were a number of aspects in both the mandrel saver and the TBC. The original TBC came about for the single purpose of preventing the snapping of the bushings and the resulting separation/lifting of CA on the blank. It didn't take long before the other/side benefits were discovered and added into the "purpose". And it was a couple of years later that a company or two came out with "mandrel savers" in response to the TBC because they were losing sales to TBC, which didn't cost anything to most turners. The none stick cones were those companies response to the 60° live centers and dead/drive centers used on most TBC, which most people already had. And quite a few pen turners were making their own non-stick bushings for finishing - which also cost a few companies lost sales. Cone shaped helped in making the separation easier. That was the original reason and advantage to TBC - cone shaped drive centers and live centers.

"Saving the Mandrel from being bent" became an "additional sales point" for mandrel savers, and that was also used in promotion of the TBC shortly after the CA benefit was discovered - long before mandrel savers came into being.

Most Companies employ great sales people and great ad/marketing people. By listing all the benefits of a product, sales potentials increase. Regardless of how they word it, it is the original purpose that brought it into being, which is what I focus on.

In the original posts on TBC, we, or rather I called it Mandrel-less, but I acquiesced to my cohorts here to the term TBC.

Below is the original cone shaped drive and original blank for which TBC and later Mandrel savers came into being:

Imported Photo from leehljp

Imported Photo from leehljp. Please edit title and description.

www.penturners.org

 

[leehljp]

Michael, I should have added that the Mandrel saver by its specific name does imply what you described; but the intention from the beginning was ALSO to allow for single blank use as does TBC, AND to allow for cone use which did the same thing for it (mandrel saver) as TBC had done in preventing the sticking bushings. Cone use on a mandrel basically took off with the mandrel saver, and that purpose was to prevent sticking of bushings.

 

[mnerland]

An overview of the chronological history and therefore the purpose:

That is part of the reason, but there were a number of aspects in both the mandrel saver and the TBC. The original TBC came about for the single purpose of preventing the snapping of the bushings and the resulting separation/lifting of CA on the blank. It didn't take long before the other/side benefits were discovered and added into the "purpose". And it was a couple of years later that a company or two came out with "mandrel savers" in response to the TBC because they were losing sales to TBC, which didn't cost anything to most turners. The none stick cones were those companies response to the 60° live centers and dead/drive centers used on most TBC, which most people already had. And quite a few pen turners were making their own non-stick bushings for finishing - which also cost a few companies lost sales. Cone shaped helped in making the separation easier. That was the original reason and advantage to TBC - cone shaped drive centers and live centers.

"Saving the Mandrel from being bent" became an "additional sales point" for mandrel savers, and that was also used in promotion of the TBC shortly after the CA benefit was discovered - long before mandrel savers came into being.

Most Companies employ great sales people and great ad/marketing people. By listing all the benefits of a product, sales potentials increase. Regardless of how they word it, it is the original purpose that brought it into being, which is what I focus on.

In the original posts on TBC, we, or rather I called it Mandrel-less, but I acquiesced to my cohorts here to the term TBC.

Below is the original cone shaped drive and original blank for which TBC and later Mandrel savers came into being:

Imported Photo from leehljp

Imported Photo from leehljp. Please edit title and description.

www.penturners.org

Thanks Lee,
As always IAP and the "old timers" are a fountain of knowledge for us beginners. Thanks again!
Mike