'A' joint issue

Dave38

Dave38

theemperorhasnoclotheson
Silver Member
Seeing Greg's thread about A-joint bolts reminded me about what I think maybe an A joint issue that I just had. I made a cored (maple) Zebrawood forearm and joined it to the maple handle with a 3/8-16 bolt. Everything was fine for a few weeks, then when I went to take my first pass, I noticed a slight wobble that wasn't there earlier.After that first pass, it was fine. I then completed the cue assembly over the next couple months, applied the epoxy sealer, sanded, then put aside. I went to start the finish over the weekend and found that it moved again, alot. It looks like the forearm warped, and maybe the A-joint. The forearm has warped, but the joint only touches the tabletop on one side. If I press the raised side down, the forearm wobbles even more. Does this sound like 2 seperate issues, or just a warped forearm? Or a warped A joint? How unstable is Zebrawood? Can the core dowel cause a warp? I had the Zebrawood for about 2yrs before using it, and didn't move in between cuts.
Thanks,
Dave
 
ive never had an Ajoint move. i use 10T not 16T. i like bigger thread grabbing the wood. i dont have experience with coring but its done to reduce weight and for stability. im interested in a possible answer. could your core not have been accuate enough and maybe there was a gap?
 
Dave38 said:
Seeing Greg's thread about A-joint bolts reminded me about what I think maybe an A joint issue that I just had. I made a cored (maple) Zebrawood forearm and joined it to the maple handle with a 3/8-16 bolt. Everything was fine for a few weeks, then when I went to take my first pass, I noticed a slight wobble that wasn't there earlier.
Dave
Click to expand...

Dave, I just did a Zebrawood "A" joint.
I need to check it.
It sounds like the forearm is moving.
The "A" joint is a very strong joint and I seriously doubt it would ever move unless the epoxy failed.

This kind of a problem is a bummer with all the work and time invested in the butt.
Every operation we do is just one more opportunity for the thing to mess up! ... :scratchhead:
But ... if it were easy ... would it be as much fun?

Please keep us posted on what you do with this one.
 
Many questions. How old was the core? And how stable was it?
Sometimes it is not the long grain of the wood that bends. It could come from the end grain swelling. Was the zebra stabilized? was the maple core laminated? What size was the core? How long did the combo sit before you joined the handle and front? Did you use epoxy on the core? Need more info...
 
Two things can happen if the metal stud is too tight or not dead centered. First is the stress on the joint, causing it to cock to one side relieving the tension on the stud. Next would be the wood actually warping to relieve tension of the stud. Sounds like you got a little bit of both. Spinning in the lathe with an uncentered or stressed stud can also cause the centrifugal inbalance that Bandido mentioned, also resulting in warpage. There is a such thing as too tight when it comes to "A" joints.
 
Zebrawood is very unstable.in the realm of Olivewood.sounds liek a forearm issue to me.
 
Yes, I've seen a core warp a forearm before. They need to be seasoned and turned to size slowly like everything else. If you want to use maple, laminated maple is more stable, but will add weight. Purple heart is also a good choice as a stable core, but all of the above applies to it as well.
 
Sorry for not including more info. Thanks also for the replies.
The core is .680, the dowel was .676 non-laminated maple with rings cut into it every 3/4", plus 2 channels running lengthwise, it was a firm fit but not so tight I had to push hard to insert. I used Elmer's poly glue, I coated the dowel and the complete inside of the core and let it set for a couple minutes before inserting. The tenon size was .650 dia. and .700 long. If I remember correctly, the bore was .720 deep. I used System3 30 minute epoxy, which I heated under a bulb to release any trapped air and it makes it a little thinner, to glue it together. I did assemble it all at once, instead of glueing the stud into the handle first then drying then assembling it to the forearm. I cut a glue relief channel in the pin and also in the threaded holes and when screwing together, did it slow, and stopped and reversed alittle to relieve pressure build up. The dowel was about 6 mo. of cutting it, as I forgot where I put them in between cuts a couple of times:embarrassed2:. Other handle/forearms that I joined with the other dowels seem fine. I had the assembled forearm setting roughly 5 months before joining to handle.The handle was a seasoned piece of maple. I hope I answered all questions, and I really appreciate the input. I think it was the forearm, as I've done a few of these in the same way, including a purpleheart forearm with a cored ebony handle and so far, the rest are fine.
Dave
 
Dave, when you drilled the zebrawood, did you let it sit or you glued the dowel right away?
 
To be honest, I really can't remember, Joey. It probably sat for about a week or two as I drilled it before I went for surgury and glued it when I was recuping,(too many pain pills:eek: )
 
Dave38 said:
To be honest, I really can't remember, Joey. It probably sat for about a week or two as I drilled it before I went for surgury and glued it when I was recuping,(too many pain pills:eek: )
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I think it twisted after you glued it then.
You said it was snug when you glued the dowel.
I would have drilled it 5/8 first then redrill it to size a few weeks later.
 
JoeyInCali said:
I think it twisted after you glued it then.
You said it was snug when you glued the dowel.
I would have drilled it 5/8 first then redrill it to size a few weeks later.
Click to expand...



Is It possible that It twisted while He was glueing It, Or is that basically what your saying?

Alot of people use the expanding poly glues. Could that expansion while glueing cause a piece to twist?

Just Curious of the ins and outs. I don't do a full core on My woods, but that somewhat limits me as to the placement of some woods in the cue, and I thought It to be a quicker, more stable, approach to core, so It is something I have planned on trying. I still haven't bought a gun drill yet. Spent way more money on other crap though:rolleyes:
 
Do you have Dehumidifiers in your shop Dave? It's been so humid here the last few weeks, the humidity in mine can change 30% or more in a few hours. I have a couple running all the time and it's a challenge to keep it at around 55%.

I've never had an issue with the Polly Glue on a core. I cut my cores as slow as I cut a shaft - from an inch round to final size in one pass (I'm kidding of course). It sounds like you took your time there, so I doubt the core is the problem.

The Zebrawood might be if it's as unstable as others say. I've never used it, but I did just trash a cue with Amboyna Forearm that was cored and I couldn't keep straight. I went pretty slow, but it just wants to move all over the place.

Like joey said, you might want to bore it out to .625 and let it sit a while before you glue the core in. That's what I'm going to do when I try the Amboyna cue again. I'll let it sit several months before I bore to final size and core it.
 
Aside from the above, one thing that you ay not be aware of or take for granted is "material strength". (Some nifty stuff can be learned in "Strength of Materials" class in Engineering School) Over tightening your A-Joint connection can buckle the softer part of the cored forearm. And this wall buckling takes time to reach maximum movement.

We CMs take our time to age and slow cut our blanks and what we really do is stress-relieve our materials. Once you core this stress-relieved blank you start introducing stress on what's supposedly a stress-relieved material. You need to deal with this first before proceeding. Once dealt with, try these additional precautionary methods. Use glue/pressure relief channels and mind your wall clearances in consideration of the adhesive you'll use.
 
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