Finish build up?

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Woodchipper

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Joined
Mar 15, 2017
Messages
3,465
Location
Cleveland, TN
I use Titebond Thin CA glue for finishing blanks. How much does six coats of glue measure? I have read where blanks are turned slightly undersize to take into consideration of the build up of glue, leaving the blank and nib, etc., even without one or the other standing proud.
 

magpens

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Feb 2, 2011
Messages
15,577
Location
Coquitlam, BC, Canada
@Woodchipper
For a long time, I had never bothered wondering how much thickness a coat of thin CA adds to a pen barrel's diameter.

Recently, I have been wondering so I made some rough measurements/estimates.

For a Sierra size blank, one coat of CA requires 4 drops of CA and adds (very approximately) 1/2 a thou to the blank diameter.

That info might be useful to you for estimating the answer to your question, which will depend on your method of CA application.

There are so many factors involved in each pen-maker's method of CA application that you pretty well have to do the measurement yourself.

My method of application is to drip the CA right out of the bottle onto the top surface of the rotating pen barrel.
At the same time as the drips fall, I hold a 1" x 3" piece of clear plastic up to the bottom surface of the barrel, rubbing slowly back and forth
as the drips fall. . The clear plastic is from a bag that pen kits come in, or I sometimes us bubble wrap for the plastic.

By rotating very slowly, I mean about 20 RPM or less. . I use the lathe to rotate and protect the lathe bed with a folded up rag ( 4 thicknesses).
Keep the rotational speed very low because you don't want to fling CA everywhere. . Electronically variable speed is essential.

After 4 such applications, I measure the diameter of the pen barrel. . I usually do about 12 - 16 such applications, then sand and polish.
So, usually this adds about 6 to 8 thou to the pen barrel's diameter. . It does vary, and the measurements are not terribly accurate.
By the time you have smoothed the surface of the CA the actual thickness is cut in half, roughly . . . . as I do things.
 

leehljp

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Feb 6, 2005
Messages
8,445
Location
Tunica, MS,
Six coats of thin will be different than 6 coats of medium, considerably different; Coats of CA thickness cannot be measured definitively because of the pure subjective nature of applying CA. More on this below

6 coats of medium applied with paper towel will be much less than 3 coats of medium applied with an applicator or small plastic bag such as mentioned in this thread:

The build up ThicKNESS of CA is NOT dependent upon the number of coats, but rather 1. the applicator type, 2. the subjective pressure of each individual as they apply it, and 3. the type of CA Thin, Medium, Thick.

Paper towel soaks in more CA than it puts on. But this is what most people learn to use and become proficient with. Once proficient, why change? But then for me and a few others, Change brings a new experience once in a while. When those plastic bags are used, or foam applicators, 90+% of the CA goes onto the blank. Build up happens much quicker overall, but slower curing in winter due to cool/cold weather. Papertowel friction in winter does create more heat and help in curing time.

I (and others) use calipers. We measure the nib end, center band, and clip end and write down the numbers and put it beside the lathe. For me, I turn the blank about .005 or .007 smaller than the measurements of the parts. Then I begin the application of CA and build up several layers. By the way, Foam applicators and those parts bags apply a smoother surface flow than paper towel does most of the time. I tend to overbuild and then take my special made scraper and turn to size, measuring every 15 to 20 seconds of turning until it is the size I want on each end.
 
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mmayo

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Joined
Jan 12, 2013
Messages
2,187
Location
Tehachapi, CA
My pens feel and look like the metal kit matches the turned and finished blank. The feel is very telling if too high. If you can SEE the difference you have an even bigger problem. That said, I turn to the Nikitas TBC bushing, sand carefully with a delrin bushing, clean with alcohol and apply finish. I sand when cured carefully and buff. I use other delrin bushings while buffing to prevent over buffing the blank at the ends. Some may wish to make this more technical than I do. My pens sell fast and repeat customers talk about the difference between mine and other pen makers in my area. Unknowingly they complimented fit and finish.

I hope this helps anyone wishing to have nice pens.
 

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