CA Problem

[avbill]

I am having problems with the edge of the CA cracking /breaking off It's nerve racking as the pen is total perfect except a small piece. enough that you can see something is wrong. If it at the area where the clip going no problem but it at the nibs end of the lower barrel. 95% of the time.

I'm using a pen mill mounted in a beall chuck on the lathe on the slowest speed.

Out of 6 pen finishes I have had to redo 5. And that's not fun

Any suggestions fellow turners.

 

[mick]

Bill if you're referring to the CA chipping when you remove the buishings then finish without bushings, between centers. This accomplishes two things. First it stops any chipping you might get when removing bushings and secondly it seals the ends of the blanks. There are various ways to dress up the ends but I keep a piece of Corian with some 400 grit sand paper glued to it by my assembly area and clean any rough Ca up that way, others use a sanding mill. However you do this, I've found for me it eliminates the CA chipping problem....hope this helps!

 

[bensoelberg]

Is the CA cracking because it has stuck to the bushings? If that is the problem, I would either look into delrin finishing bushings, wax your bushings or score a line around the bushings with an Xcto knife or hobby knife so that the CA is more likely to break away from the bushing instead of chipping out on the end of your pen. If you've done all of that, and it is cracking when you are trying to clean the ends, I would try sanding the excess CA off instead of using your pen mill. The method that I use is pretty simple. I got a sample piece of corian from Home Depot it's about 1.5"x1.5"x.5". Using some double stick carpet tape, I stuck it to the center of my faceplate, then taped some 220 grit sand paper to it. I put my drill chuck ($10 HF model) in the tailstock and find the transfer punch (also $10 HF) that is closest to the inside diameter of the tube and put it in the drill chuck. I put the finished barrel on the punch, run the punch up to the headstock until it is just about touching the sandpaper, (1/32" away). With the lathe on its lowest speed, I gently push the finished barrel against the sandpaper while rotating the blank on the punch by hand. Works great and is much less aggressive than a pen mill.

 

[monophoto]

Bill - I think your problem is that you are finishing between bushings on a mandrel, and the CA is adhering to the bushings. You can usually snap the piece away from the bushings, but sometimes that fractures the acrylic coating. One solution that I've read about is to use the tip of a skew to gently cut through the CA right at the end of the finished barrel. My experience with that is that it works sometimes, but sometimes the skew slips and cuts into the barrel.

The solution that I have been using is to replace the steel turning bushings with a set of HDPE bushings. This does two things. First, the HDPE bushings are home-made and no attempt was made to duplicate the actual turning bushings. Instead, they are tapered so that they slip inside the end of the pen tube, but leave a gap at the end. As a result, therere is less tendency to actually glue them to the body of the pen. Yes, some CA will accumulate at the end of the barrel, but that can be dealt with later.

The other thing is that CA will dry on HDPE, but it doesn't actually adhere to HDPE. So when I take this apart after finishing, the plastic bushings snap off much easier. That does leave a rough edge on the glob of CA at the end of the body, but it isn't cracked back onto what will be the finished pen body.

I combine this with the use of a sanding mill on the finished pen. My sanding mills are also homemade - simple spindle turnings with a bolt embedded in one end. I chuck the bolt into a drill and either file or sand it down to a diameter that fits inside the pen tube. Then, I glue the bolt into a billet and, using a Jacobs chuck, turn the billet into a handle. I leave the face of the mill around the bolt flat. Finally, I cut hole in a small piece of sandpaper, and slip it over the bolt with a bit of thick CA between the sandpaper and the smooth end. To use this, I simply insert the sized bolt into the end of the tube, and spin the handle to sand off that blob of excess CA.

 

[MartinPens]

I agree with the above post. I used to have similar problems. I apply my CA (I used 1 coat of thin and then 4-5 coats of medium) with a little accelerator after each application (no accelerator after the thin CA). Then I sand with 400 gently to a uniform cloudiness with no glossy streaks. I then take the tip of the skew (flip the skew upside down) and score the BUSHINGS lightly where the bushings meet the blank. I'm not scoring the blank if at all possible. I'm doing my best to find that place on the bushings that touches the blank. Then I use the micro pads from there. If you use an exacto knife, I would recommend not turning the lath on and just go real slow. I haven't had success with that method. The exacto knife tends to want to ride onto the blank and make a mark. Good luck. Hope you find a solution that makes the turning work out every time.

Martin

Sent from my iPad using Forum Runner

 

[IPD_Mr]

I think Bill is having problems when he mills the ends after taking it out from between centers. If this is the case, never use a mill after a finish is applied. Take your mill and put it on backwards. Cut a 3/4" square piece of self adhesive sand paper and use a hole punch to pop a center hole in the paper. Now sand mill the ends of the barrels. You will see no more chipping of finishes.

 

[avbill]

Mike is correct I'm having problems with the CA after the finish is completed asnd I need to sand the ends down to remove the excess of the CA.

I have a pen mill [carbon] for squaring the ends before turning the blank

I have a pen mill sander that I use for getting the blank's end square for the assembly of the kit. I using 100 grit sandpaper.

I'm looking at two beauty CA finish except there is a 1/32 chip of the Ca at the very end of the blank.

 

[PenMan1]

Before you try to remove the blank from the lathe, use an exacto knife to make a thin cut where the blank meets the bushing. Turn the lathe with your left hand while steadying the exacto to the tool rest with your right hand.

This makes a precise separation and sanding or "end dressing" will not be required.

 

[Lee K]

I separate the bushings after every other coat. I will even take the barrels off after the first 2 applications of thin .... lightly sand the ends of the barrels to keep that 'curve' and eliminate the hard edge.

 

[leehljp]

Bill,

You said in your first post that you used the slowest speed. With a pen mill sander, you shouldn't have a problem but if using the pen mill itself, the slower speeds will cause more catches and tear than high speed. High speeds mean smoother; slow means more catches, rips and tear outs.

 

[itzapen]

Bill,
You may want to try delrin bushings form JohnnyCNC. The CA does not stick as it does on steel bushings. Also, when removing the bushings form the blank there may be some small pieces above the rim of the blank. Gently take your thumb nail and press the excess CA towards the center of the blank. I carry a pen as a reminder that if you you push the CA to the outside, it will chip off below the rim. I slowly use my thumb nail and go around all the edges to make sure they are clear. Remember to pull streight down toward the center so as not to chip the CA.
Hope this helps you.

 

[ghenley]

I've ruined many a polymer pen because I glue the blank to the bushings, and the pen knife approach has not worked for me. My solution was to cut narrow rings from spare tubes (1/2 length of narrow bushing insertion part) and slip them onto the bushings. There is enough length left to insert the bushing into your turned blank and slip it onto the mandrel. Tighten just enough to turn while applying glue. The gap is enough to keep the glue out. After the CA has dried, slip off the rings, insert the bushings again and sand away.

 

[toddlajoie]

I think Bill is having problems when he mills the ends after taking it out from between centers. If this is the case, never use a mill after a finish is applied. Take your mill and put it on backwards. Cut a 3/4" square piece of self adhesive sand paper and use a hole punch to pop a center hole in the paper. Now sand mill the ends of the barrels. You will see no more chipping of finishes.

+1 on this method. Cheap, easy, uses stuff you probably already have, nearly the perfect solution to me...