trying to dial in a process

[btboone]

It seems simple enough. I'm attempting to do a thick clear coating on cherry burl blanks and am running into walls everywhere I go.

I have done some prototypes with a thick CA finish. This gives the look I need. The problem is the wood has all sorts of holes and checks and stuff. It took me 5 hours to do one to the look I wanted. There was a lot of going back and filling stuff, etc. The trick is I will have to make a batch of hundreds, so I won't have the time to do that. This is my first time making a big batch of wood pens!

I bought a pressure pot, a vacuum chamber, and I have a small kiln with a good controller. I made a fixture to be able to over cast 54 blanks at a time. There are machined plastic plugs on either side and an outer thin plastic tube for the resin to be molded in. It took several tries in Alumilite to get less than disastrous results. The first few times had massive clouding and the next had only a coudy area right near the surface. From what I gather, this is due to some moisure either on the wood or in the airline or whatever. I did have one turn out OK.

My process is that I glued in the tubes in stabilized wood then turned them about .015" per side smaller than flush on the CNC. After the casting overcoating operation. the parts were turned exactly to flush. The CNC is very repeatable, and the parts were turned consistently. I ideally, I'd like to take the hand turning inaccuracies out and speed stuff up.

What I found on my one good part was that Alumilite essentially doesn't polish out! You can still see the fine sanding marks, even when hit pretty aggressively on a polishing wheel. That is a show stopper. I tried Polyester last night, and it completely pulled away from the wood. Another No Go.

Has anyone tried tricks like stabilizing after the wood is on the tube? In theory, less material is used, and if done right (in a mold) might fill those bad spots? My vacuum chamber is being made now, so I can't experiment yet, but I'm hoping there is a solution that can essentially turn the rough and checked wood into plastic that the CNC could eat for lunch.

Any ideas on what else to try? If casting fails, I can go back to CA, but I'll need to bring the wood roughing dimension up to about .005" per side or so, as the CA took about 30 coats to get the thickness I was trying for. Ideally something hard and clear that the CNC will turn off automatically to final dimension then a final sand with 600 grit and polish. That's what I'm shooting for.

 

[JohnU]

I've stabilized a lot of my own blanks with cactus juice but I've never tried stabilizing on the tube. I personally would be afraid the blank might distort in shape since I've had many do this in the normal blank size, from the heat and resin curing. I would think the tube would get hot and possibly weaken the glue or epoxy joint between the tube and wood. I'm curious if stabilizing is necessary since your casting them. I've had repeated success in casting Silmar 41 over many different woods that were turned down just below the bushing size. I never had a problem with it pulling away or moisture because I coat the wood with a couple layers of thin CA and let it cure for a day. I used Maple, Cherry, and Oak in my projects that were turned and sanded to a nice smooth surface like you would a pen before you apply the finish. It might be more time than you want to spend. Good Luck!

 

[jttheclockman]

Have never pursued this but it maybe something to look into. Maybe someone has tried this.

Powder Coated MDF or Wood Components

There is also the Solarez method that has been kicked around here and there are a few that have some technique down by now. maybe they will chime in. I know time is a factor but it always is. That is why we need to look into things like this when there is no need. Being way ahead of the game.

 

[btboone]

Interesting stuff. I didn't notice that the powder coat is possible in clear, but maybe it is.

John U, a coat of CA before casting sounds like it might help to avoid a lot of the casting issues I'm seeing with PR and Alumilite. I've not heard of Silmar 41, but I'll try anything once! I suppose I could cast, turn to final, then do a final CA coat as well, but I wonder if a thin coat like that might peel. I don't know if others are getting better clarity with their Alumilite, but I was definitely not impressed with my trials. All blanks were a bit hazy and some were full white. On my first try, it set while I was pouring, and a big blob came out of the cup. It was crystal clear whereas all my blanks were hazy. They were in the pressure pot, while the blob was not. I'll need to look further into doing an air dryer before it gets to the pressure pot.

 

[btboone]

On CA finishing, I know everyone has their own technique, but what's a good thickness to shoot for? If using medium CA, say 5 coats? Maybe 10? Also RPMs on the lathe, fast to help dry or slow to keep from slinging stuff off? Anyone have luck with a plastic shaper of some sort to slather it on, or just a paper towel?

 

[BRobbins629]

The uv curable resins maybe a good choice. They are very hard, will buff to a high gloss and have good wood adhesion. Some are used for furniture and guitars. Like John says, Solarez has some good stuff. Eastiest to use for me is their ultra thin for fly tying. I have built up some very heavy coatings over things like snakeskin.

Another idea would be to contact one iof the good casters here and subcontract.

 

[btboone]

Both good ideas. I have some UV resin and a UV source. I tried it in rings, and it didn't work well there, but maybe it would work to fill deep holes better than CA. Definitely worth experimenting with.

 

[btboone]

Ok, back to basics. If I found and worked with the cleaner blanks, is there really a need to stabilize them? These are one of the larger kits, so wood is pretty thin. If I just did a CA finish, would that be enough? I only have a small kiln made for jewelry, so the thought of drying a small volume maybe 8" cubic at a time for 24 hours is not ideal in the case of stabilizing. This was freshly cut cherry burl and was about 20 moisture content when I got it. If just CA, how low should the moisture content be ideally? I can lay them on my back porch, which is slate, and where sun reflects off the windows and direct sun combine, it can get to something like 190 degrees and there is wind to help evaporate away any moisture. Seems like that could get the blanks fairly dry.

 

[Skie_M]

You'll want to get the blanks as dry as they can be, ideally ...

Moisture Content for kiln-dried lumber ranges from 8 to 12 percent.


You could also just use your oven .... set temperature to 150 degrees and arrange the blanks on the racks, crack the door 1 - 2 inches, just like you are making jerky .... should be done within 2 to 3 hours.

 

[oldtoolsniper]

I would eliminate one issue at a time. The 20% moisture would be my first one. That is pretty wet and no where near stable, it will shrink as it dries so get it dry first. There are a lot of ways to do this. I use a food dehydrator myself but that's only one of the many ways to dry wood.

Alumilite combined with moisture will create cloudiness. You are essentially doing a worthless wood casting. There is a lot of information on this style of casting.

The reason worthless wood is cast in alumilite is because most other resins shrink quite a bit during the curing process. Shrinking in your voids would still leave a void.

The IAP library has quite a few tutorials covering different techniques, you just need to combine them and narrow down the problems you are encountering.

I'm learning to do feather blanks. Not much information out there on them. However I know it's possible, I've seen some beautiful ones here on this site. I'm a couple weeks into my quest and by eliminating or changing one thing at a time I can determined if that's the problem.

Solve one thing at a time and you will eventually come to success.




Sent from my iPad using Penturners.org mobile app

 

[leehljp]

Both good ideas. I have some UV resin and a UV source. I tried it in rings, and it didn't work well there, but maybe it would work to fill deep holes better than CA. Definitely worth experimenting with.

I have been meaning to check with my dentist friend that I graduated HS with, because I wonder how the UV light works in glueing in the ares that UV cannot penetrate.

I said that because 3 days ago, I tried Solarez on a couple of screw tangs (posts) that broke off of a plastic box at the bottom. I added the solarez to the 2 posts, stuck them back into their previous positions, seated well and UV light for about 2 minutes on each, I then added an external layer of Solarez, UV'ed it for about 5 minutes each. It felt solid, I waited about an hour and then tried to screw the top onto the posts. Came loose way before I got it tight. I looked at it and the Solarez that was up under the posts was still wet. Where UV light did not reach, it did not harden. I had a 36 or 40 LED UV flashlight on it.

So back to my original question, I wonder how Dentists get UV glue to harden in places that UV light doesn't reach. I think this is what is needed for BTBoone's work to be effective with Solarez.

 

[Skie_M]

It's put on in thin layers, cured, and then you can add more directly on top or you can scuff/grind the surface if you want better adhesion in some varieties.

Now ... using it in a blind location where UV light cannot penetrate just wont work ... use some kind of epoxy for that situation.

 

[BRobbins629]

Both good ideas. I have some UV resin and a UV source. I tried it in rings, and it didn't work well there, but maybe it would work to fill deep holes better than CA. Definitely worth experimenting with.

I have been meaning to check with my dentist friend that I graduated HS with, because I wonder how the UV light works in glueing in the ares that UV cannot penetrate.

I said that because 3 days ago, I tried Solarez on a couple of screw tangs (posts) that broke off of a plastic box at the bottom. I added the solarez to the 2 posts, stuck them back into their previous positions, seated well and UV light for about 2 minutes on each, I then added an external layer of Solarez, UV'ed it for about 5 minutes each. It felt solid, I waited about an hour and then tried to screw the top onto the posts. Came loose way before I got it tight. I looked at it and the Solarez that was up under the posts was still wet. Where UV light did not reach, it did not harden. I had a 36 or 40 LED UV flashlight on it.

So back to my original question, I wonder how Dentists get UV glue to harden in places that UV light doesn't reach. I think this is what is needed for BTBoone's work to be effective with Solarez.

To answer your question, they can't get it to cure where light doesn't reach. This is also why you don't see pigmented uv coatings. They have long been used in the packaging industry, but only as a top coat over non uv ink systems. It's also not the number of uv bulbs in the light but the power of them. I have cured coatings with a single uv bulb. Also may depend on how much photoinitiator is used.

 

[btboone]

I just ordered some 2 part epoxy by the name of Crystal Sheen. It's made for bar tops. It sounds like it should be polishable and have a long pot life. Both of those things didn't seem to work well for me with Alumilite. It sounds like it would be somewhere between stabilizing fluid and Alumilite for getting into and filling cracks. I have the 54 blank mold setup and could vacuum out bubbles if necessary. I like that I would be able to see them setting up rather than using the pressure pot. The only drawback I see is that it takes a full day or two to cure. This would give me my overcoated blanks to throw back on the CNC then go to final polish. Even though the set time is far longer than the other stuff, I would make up for it in labor if I could go right to polish after the final turning. It would likely take some wet 600 grit sanding by hand before polish, but that is tons ahead of several coats of CA with all the opportunities to mess that up.

 

[Brian G]

On CA finishing, I know everyone has their own technique, but what's a good thickness to shoot for? If using medium CA, say 5 coats? Maybe 10? Also RPMs on the lathe, fast to help dry or slow to keep from slinging stuff off? Anyone have luck with a plastic shaper of some sort to slather it on, or just a paper towel?

You're about 10 years further into pen turning than I, so my experience is rather young by comparison.

Thickness: I'm about 0.004" to 0.008" depending on how far I overturned or oversanded as measured by calipers. I overturn and then over apply CA, then final finish to the dimension of the mating component. Too thick makes a pen look entombed, in my opinion.

Coats: I don't know for medium. I only use thin. I calculate about a 0.001" layer for each coat of thin the way I apply (sparingly per coat). I come to that number because after 10 coats of thin I'm about 0.006" above final

Speed: Slow as the lathe will go. For me, that's 500 rpm. You're right; too fast and it slings off. That, to me, is not as bad as not slinging off and building big ridges.

Slather: Don't slather or glop it on. A small drop worked back and forth until one second before it starts to harden.

Applicator: Plastic shaper of some sort probably is too stiff. I use craft foam and won't ever go back to paper towel. I use less CA, the craft foam is more consistent for me because it doesn't leave ridges, and I don't risk the annoyance of finding specks of paper towel lint or dust in the finish. I cut strips of about 3/4" x 2". I apply a drop on the very end and more or less squeegee the CA along the blank. I can use both sides of the end, clip it off, and keep going. It helps me count coats, too.

 

[btboone]

Great info. I see there's lots of learning curve for all this stuff!

 

[Dale Lynch]

Look into the shore hardness of the bar top epoxy.some will not harden up enough to be machinable.Less than 80 shore D is probably going to be too soft for your needs. Bar top stuff is designed to lay on a flat surface resist chemicals and absorb impact.

Also have you tried buffing your alumilite with a clean soft buff after your compounded buff?

 

[btboone]

Look into the shore hardness of the bar top epoxy.some will not harden up enough to be machinable.Less than 80 shore D is probably going to be too soft for your needs. Bar top stuff is designed to lay on a flat surface resist chemicals and absorb impact.

Also have you tried buffing your alumilite with a clean soft buff after your compounded buff?

It actually worked great. Much better than Alumilite, as it doesn't cloud, and better than another epoxy I tried. They seem to be about the same hardness after 3 days setup. It took some experimentation on the final polish, but I got a technique that worked.

 

[thewishman]

Congrats, Bruce. I've always admired your willingness to try new things and new processes.