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Segmenting with a steep angle

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Forum topic by tyskkvinna posted 05-27-2012 10:18 PM 1052 views 0 times favorited 10 replies Add to Favorites Watch
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tyskkvinna

1308 posts in 1739 days


05-27-2012 10:18 PM

Topic tags/keywords: question

I am doing some segmentation and I have been playing around with angles. Specifically I am doing something akin to the Celtic Knot, except just one line rather than the whole knot. I am turning some things on a bottle stopper mount.

Three or four times now I have been midway through turning and end up snapping the wood clean off at the glue joint. I have tried using CA glue and tried using Titebond – both pieces snapped off. The ones that I have tried with a flat angle have turned without issue.

Any suggestions for me? I am turning with a live centre and then when I get to the very end I have to take the centre off, and that is when it is snapping. (I tried turning without the live centre from the beginning, like they tell you that you can, and ended up ripping the wood clean off the mandrel. Ooops!

I dug around in the website quite a bit but couldn’t find exactly what I was looking for.

-- Lis - Michigan - http://www.missmooseart.com - https://www.etsy.com/people/lisbokt


10 replies so far

View Jim Jakosh's profile

Jim Jakosh

12383 posts in 1858 days


#1 posted 05-28-2012 01:11 AM

I am surprised that it would break at the glue joint using Titebond. Do you clamp it and let dry overnight?

I think what I would do is stop the process just before the machine takes out the nub with the center and cut off the nub with a hacksaw. Then turn it on and let it finish the cut to clean up the top. That is hanging out there with a lot of spring in it away from the chuck and that snap off coud cause quite a shock.

My 2 cents worth…..........Jim

-- Jim Jakosh.....Practical Wood Products...........Learn something new every day!! Variety is the Spice of Life!!

View Loren's profile

Loren

7826 posts in 2401 days


#2 posted 05-28-2012 01:28 AM

Are you gluing end grain or trying to glue without real
clamp pressure?

-- http://lawoodworking.com

View BertFlores58's profile

BertFlores58

1646 posts in 1675 days


#3 posted 05-28-2012 01:34 AM

Lis,
Try to check on the grain orientation plus the wood tension as where it has to expand. If joint has to be end to end, then this will prevent the tearout if you turn longitudinal like however there is no guarantee on the sides where it becomes so near the last grain. Gluing quarter rounds together, with the weakest point (where a possible tearout would occur) be place in the center of rotation can also be a good way but patience is required.

Another one… make a dowel in the middle from bamboo (skewers or chopstics are made from bamboo.) Bamboo are very resillient and absorbes lot of glue in them. You can hide this by just inserting it in the midsection of your stock.

Hope you would be successful.

Have a nice day.. Its been a while I was not around in LJ.

-- Bert

View tyskkvinna's profile

tyskkvinna

1308 posts in 1739 days


#4 posted 05-28-2012 02:25 AM

Yeah I’m clamping them…. :-) C-clamps with titebond and let them sit at least overnight.

There’s no end-grain gluing but it is a lot of very awkward angles. I’m cutting it at a 15 degree angle relative to the long grain. Also tried a 25 degree. Both failed…

I will try the chopstick idea. I have a bunch of those. I had been debating just putting a screw in the bottom of the hole but didn’t really want to do that.

-- Lis - Michigan - http://www.missmooseart.com - https://www.etsy.com/people/lisbokt

View Roger's profile

Roger

15362 posts in 1557 days


#5 posted 05-28-2012 08:58 PM

Maybe the tool needs sharpened? Just trying to guess myself also. ?? Please let us know what you find out. Thnx

-- Roger from KY. Work/Play/Travel Safe. Kentuk55@bellsouth.net

View rance's profile

rance

4149 posts in 1913 days


#6 posted 05-28-2012 09:44 PM

Sounds like you are just being too aggressive or your tools are not sharp enough. Could you post a pic or two of your pieces you are having problems with?

-- Backer boards, stop blocks, build oversized, and never buy a hand plane--

View tyskkvinna's profile

tyskkvinna

1308 posts in 1739 days


#7 posted 05-28-2012 11:05 PM

I’m definitely not being too agressive. I’m making cuts that are 0.003” deep. (Remember I use a metal lathe)

I will see if I can take some pics in the next day or two to share with you all.

-- Lis - Michigan - http://www.missmooseart.com - https://www.etsy.com/people/lisbokt

View Craftsman on the lake's profile

Craftsman on the lake

2420 posts in 2191 days


#8 posted 05-28-2012 11:34 PM

I understand that the joints are failing. But, in my experience if a joint is smooth and clamped and not end grain the wood around the joint will fail before the glue joint if using white or yellow glue. Just, sayin’ if you can figure out why the glue joint is failing then you’d have it stay together which would be the best outcome for what you are trying to accomplish.

The smoother the wood for the joint the better the glue will work.
Clamping pressure just needs to be so squeeze out starts

Then again you probably already have done this. A head scratcher for sure.

-- The smell of wood, coffee in the cup, the wife let's me do my thing, the lake is peaceful.

View D_Allen's profile

D_Allen

495 posts in 1537 days


#9 posted 05-29-2012 12:55 AM

I was watching a video you made of cutting a maple piece sown to size on you CNC lathe.
What I am wondering is if maybe the angle of attack on the wood is too aggressive. It seems to me that when you are cutting into the wood at a direction level with the center of the piece, it could be stressing the workpiece. Also, what speed are you using. If that is the case then the joint may become weakened during the initial roughing out and fail as the glue area gets smaller.
As a comparison, I often glue waste pieces onto pen blanks and that is end grain to end grain using titebond 2 glue.
When I begin the turning, I use a large roughing gouge that is the sharpest tool I own. I take very light cuts until the corners are turned well away. The angle of cut is the method of rubbing the heal of the tool to the wood and tilting it until it bites in. I have had these glue joints last until the very last 1/8” diameter is turned down.
I think I’ll try some angle cuts to see if that makes a difference.

-- Website is finally up and running....www.woodandwrite.com

View rance's profile

rance

4149 posts in 1913 days


#10 posted 05-31-2012 01:39 AM

Lis, you realize that in woodturning, there is most likely a bevel of sorts rubbing all the time. Whereas on a metal lathe, the tool bit is cut to give relief to the metal since the tool bit is mounted ridgid. If the metal bit starts to dig in, then there is nothing to stop it from going further like when using woodworking tools. I’m guessing that could be the problem.

When you get around to the pics, please include a pic of your tool. I’ll bet you have it ground in what a woodworker would call a scraping geometry rather than a cutting geometry. I’ve see one scenario where someone ground a metal cutting tool to cut like you want(shearing action), but I don’t have a link to it. Maybe on the 7×10 group? Or more likely on mini-lathe.com

-- Backer boards, stop blocks, build oversized, and never buy a hand plane--

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