Hi there, still new to pen turning. I've been having quite a few wood blanks while on the mandrel chip off down to the tubing and being ruined. Am I doing something wrong or is that just how it goes? :C
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Hi there, still new to pen turning. I've been having quite a few wood blanks while on the mandrel chip off down to the tubing and being ruined. Am I doing something wrong or is that just how it goes? :C
Hi, I’m still learning myself, but if you have a slight crack in the timber it may split, it’s happened to me a couple of times. If I see a crack, once it’s turned down a bit I put some CA in it and sand to fill. I have found this helps. There are a lot more knowledgeable people on here than me though.
Good luck
Dean
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It has been a while since I last turned a pen... but I've found that the #1 cause for this is air-gaps in the glue between the blank and the tubing.
Eventually I found that epoxying the tube into the blank was the only way I could ensure a good glue up. Sadly, it is also the messiest method.
But the results speak for themselves.
As skew said. I'll take a stab and guess being reasonably new to pen turning you're using CA to glue the tubes into the blanks. As skew mentioned, it's usually the glue letting go that causes this issue. Using epoxy glue (aryldite) works well but I tend to only use this for resin or hybrid blanks rather than straight timber. For solid timber I use polyurethane glue. This glue expands as it dries and fills any gaps there may be.
Since switching glue I haven't had any blow apart on me (unless I have been heavy handed with the skew but that isn't a glue problem)
I predominantly use medium CA for my glue ups and have never had a failure. Initially I used thin CA but did have a couple let go if I went at it too hard. The other problem with thin CA is that if the hole in the blank is too tight a fit on the tube the tube can get stuck before it is all the way in because the CA goes off too quickly in the small clearance, medium goes off slower. I put a layer of glue inside the blank and smear it all around and also coat the tube. When the tube is inserted I twist it back and forward while slowly sliding it in and out and the CA gets a chance to cover all areas inside making 100% contact.
I sometimes start turning the blank within 1/2 an hour of the glue up at around 2,000 RPM and light cuts so there is no real force on the blank. Heavy cuts, blunt tools and slow speed will tend to tear the blank from the tube.
Might pay to examine your choice of chisel, method of presentation to the wood,
as you might be too aggressive. Sharp chisels are a definite advantage.
I'm with Dallas on this I only use medium ca glue from Timbebits and haven't had any issues easy to use and if left overnight no problems.
While the glue could play a role and you can try a good 5 minute epoxy instead of CA, I agree with what Allen said above. It is most likely tool and technique. There must be a turning club in your area where you could get a member to help you with some basic hands on turning, even if only for half an hour. Otherwise be prepared to either loose a lot of blanks or practice on scrap wood between the centres your lathe came with until things jell and you get the hang of it. You could try youtube but there is as much bad instruction (actually more) as good and nothing equals good hands on. Don't be discouraged, it just takes a little practice.
Pete
I'll add that when you know how to turn you can take a straight grained blank and drill it to fit the bushings. Mount it on the lathe without any tubes and turn it to size and not blow it up.
A pic of your setup (blank ready to go, and when mounted on the lathe) might help.
It could also be not having the ends of the blank trimmed square, (so one bit gets more pressure from the bushing and cracks off), or too much pressure from the tailstock.
CA user here as well. Make sure your chisels are as sharp as you can get them.
I use both med ca and also 5 min epoxy. I have found if you use the wrong activator with a ca it can cause the ca to be brittle, I found if I glue up one day with either and do a batch. Then I turn them the next day. I also use playdo to block the end of the tube i am inserting and I put glue in the blank and also on the tube im inserting and I twist the tube as I inserting the tube this has cut down my blowouts
Hey Skew, been a while mate. The debate as to how glue and what with. What you described is a blowout due to the lack of adhesion of tube to the drilled hole. There are people that prefer CA, thick for gluing, epoxy or a polyurethane glue. All are and can be messy to use. Dispossb look e rubber gloves are the answer. CA burns, epoxy is plain messy and polyurethane will turn the skin black for a week or so.
In saying that whether you use any of the 3 mentioned coat the drilled hole with the glue first. Seal the end of the tube that you are going to push into the blank, this will stop the glue going inside the tube.
Coat the tube well and twist it into the hole. The glue in the hole and glue on the tube will adhere together forming a solid bond.
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