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Glue-joint Failure; what am I doing wrong!?

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Forum topic by Bertha posted 1120 days ago 2539 views 2 times favorited 71 replies Add to Favorites Watch
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Bertha

12951 posts in 1320 days


1120 days ago

Ladies and gentlemen of the Lumberjocks, I recently received a 1/2” MLCS gluejoint bit without bearing guide. I chucked it into my table-mounted Triton 3hp, made a few test pieces, dialed it in. I made a setup block once I was happy with the cut, then moved to my piece. To my horror, it was horribly off, rendering the piece useless.

I checked the bit against the setup block and it has moved upward at least 1/8”.
1) Yes, I’ve taken the plunge spring out of the Triton 3hp, using above-the-table crank
2) yes, I’m pretty sure I have the plunge lever locked
3) Yes, the bit is very snug in the tightened collet
4) I’m running very slow rpms.

I must admit, I have a hard time visualizing how a glue bit works spatially. I managed to succeed in test cuts but I’m still a bit confused. I’m not even sure what my main question is, so I’ll just accept ANY comments graciously. Thanks!

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog


71 replies so far

View Roger's profile

Roger

14318 posts in 1431 days


#1 posted 1120 days ago

when you put the bit into the collet, and bottom it out, raise it up about a sixteenth, then tighten it down. sounds like the bit is just not getting tight to me. how old is your router/collet? maybe its worn out.. dats my thoughts. ??

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

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ajosephg

1850 posts in 2188 days


#2 posted 1120 days ago

I’m voting on a worn out or dirty collet.

(While it can retain “smaller” bits, the increased torque on these bits cause allow the bit to creep upwards.)

-- Joe

View Bertha's profile

Bertha

12951 posts in 1320 days


#3 posted 1120 days ago

Thanks guys, there’s a distinct possibility that I didn’t engage the plunge lock. It seems to defeat the purpose to have an above-the-table crank, then having to reach under the table to lock the plunge mechanism (?). I tugged real hard on the bit and it seemed snug in the collet. The router is only a few months old, maybe ran 10 feet through it.

I’ll try to elevate the bit in the collet just a hair. And yes, August, the bit elevated itself above the table. With a gluejoint, it’s hard for me to say whether it was cutting deeper or more shallow, given that you flip one of the workpieces;) I’m still generally confused about how to properly setup a glue-joint bit. It makes sense that you’d want “where the two opposing tongue/groove lands/valleys meet” in the middle of the board. Oh well. Thanks!

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

View Porchfish's profile

Porchfish

572 posts in 1159 days


#4 posted 1120 days ago

Hello my friends, I am going to show my age here and ask why the router is necessary for gluing up lumber ? Enlighten me. I have always surface glued lumber after using a rip/glue blade on my table saw and made use of titebond, upper and lower pipe clamps and immediate clean up. In cases of resinous material I have used a 1/4 ” or less spline (depending on stock width) if the spline material grain runs perpendicular to the material being joined, mount olympus would not be able to move it . But I am always anxious to learn new techniques if they improve on, or lessen the effort required to complete a task.

-- If it smells good, eat it ! The pig caught under the fence is the one doing all thesquealing

View klassenl's profile

klassenl

113 posts in 1286 days


#5 posted 1120 days ago

From what I understand of those types of cutters is that your stock has to be exactly the same width as well. If it’s not then you will get and error in the same size that your stock is a different width.

-- When questioned about using glue on a garbage bin I responded, "Wood working is about good technique and lots of glue........I have the glue part down."

View Bertha's profile

Bertha

12951 posts in 1320 days


#6 posted 1120 days ago

To Porchfish, there IS NO good reason for a gluejoint in my shop. I hand joint, then Titebond III. The only reason I’m playing with this bit (translated ruining my stock) is because it came in the set alongside my raised panel set. I’m simply curious (and an idiot). I’m using cheap pine so I figured I’d try a new joint.

To Klassen, my stock is exactly the same thickness, namely 3/4” off the DeWalt 735. The bit is weird. It seems like if you flip on piece, the cuts should mate irrespective of the bit height. I’m having brain issues on this one.

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

View Bertha's profile

Bertha

12951 posts in 1320 days


#7 posted 1120 days ago

I should have spent the $20 extra for the setup blocks. My bad.

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

View dbray45's profile

dbray45

2488 posts in 1403 days


#8 posted 1120 days ago

Al,

Put your straight edge across your table and very carefully check your inset to be flat – length wise and at 45 degrees. Then put a piece of wood between your fence and the straight edge. Pushing down, with the same force that you use when holding the wood to cut, see if there is any deflection in the plate. If there is, your joints could be out a significant margin from the ends and middle.

Then, with the bit in place, I use welding gloves for this, see if there is any slop in the bit grabbing it at trying to move it – up, down, back and forth, if there is, its the bearings, if the bit can be pulled out, its the collet.

If there is still a problem, look at the grain and see what it is doing. I have had pieces that after milling, had a warp. It is annoying but it happens. After that, it is a setup issue. Run the bit at design speed or the cuts will be scalloped and not fit.

-- David in Damascus, MD

View Bertha's profile

Bertha

12951 posts in 1320 days


#9 posted 1120 days ago

Von, thank you. These bits are not high quality ($120 for the whole set) and I will probably never use a gluejoint bit again. Curiosity got the best of me and I was pretty tickled with myself after my first (lucky) pass. I figured, what the heck, I’ll just have an excessively strong gluejoint in my panel that will have absolutely no stress applied to it. I probably could have put gum in the joint and been fine. Instead, I ruined my piece with a bizarre 1/2 gluejoint. The boards are dead-flat and even. I paid meticulous attention to my feed. The cuts themselves are very uniform and don’t deviate along the length of either face; they’re just 1/4” off of each other!!! I fear that I’m missing something painfully obvious. At a minimum, I need to figure out why my bit creeped between the test pass and the real pass. I had been using the table saw to rip boards after I had set the bit on the extension router table and made my setup blocks. I’m thinking that if I didn’t have the plunge lever locked, the vibration from my ripping may have allowed the adjuster to raise the bit.

To anyone with an undertable Triton 3hp, do you have to lock the plunge mechanism? I’ve already removed the plunge spring, as recommended.

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

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Bertha

12951 posts in 1320 days


#10 posted 1120 days ago

Von, how do you “center the bit on the board?” What is the “center” of a gluejoint bit? I will take some better pictures tonight.

This is the bit in question:

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

View dbray45's profile

dbray45

2488 posts in 1403 days


#11 posted 1120 days ago

I have the set, works well. When set, I always lock things down so the router doesn’t drift. Setup blocks are great if you are always using 1/2” or 3/4” wood. I make my own using offcuts from pieces that I am using. Make them work first before touching the real stuff.

-- David in Damascus, MD

View Grandpa's profile

Grandpa

3078 posts in 1302 days


#12 posted 1120 days ago

You ran a test piece on pieces and they were perfect. After you ran the good wood and produced the bad parts did you take the test pieces and see if they fit the setup….as you would a setup block? I know it seems like something not necessary but I could see the router drifting up and down while operating if it isn’t locked in place (the plunge mechanism). Stranger things have happened. One thing we know for certain is something moved.

Porchfish, you should get a stronger joint with a perfect fit with this set up. I know you get joints stronger than the wood with you set up but we are always wanting overkill. When I was in high school we would take the ends of our glue ups and break them to see if they broke in the joints. That was with white Elmers glue. When the yellow glues came along we didn’t hesitate to use it because it was stronger. No need. the white glue was stronger than the wood, but we still used it then we went to Tite Bond II and now III. It is just our nature.

View CampD's profile

CampD

1201 posts in 2113 days


#13 posted 1120 days ago

First, I have the same set and rarely use that bit.
Second, was the test stock and finished stock exactly the same thickness?
you mention that it was a 1/16th off, sounds like the stock had a 1/32nd difference in thickness,
1/32 + 1/32 (when you flipped the piece) = 1/16.
when ever I’m running stock like this thru a bit this size I make more then enough extra pieces to test multiable set-ups plus an extra just in case.
and third, make the finished piece thicker and finish it off by running it through the planer after glue-up.
Remember, wood is not perfect, we have to make it that way!

-- Doug...

View coloradoclimber's profile

coloradoclimber

548 posts in 2695 days


#14 posted 1120 days ago

An advantage of using a glue joint bit is that if the bit and stock are setup right the mating surfaces should meet (ideally) without any offset in the joint. You don’t need cauls, you don’t need fancy clamps, you don’t need anything special. The glue line is self aligning, spread some glue and clamp across, done. When you take the clamps off there is little to no offset to plane / sand / scrape / mess with.

I recognize that with a “proper” glue up, and some cauls, and some wishful thinking, you should be able to edge glue two long boards and have no offset anywhere along the joint. If so you’re a better man/woman than me. I usually don’t use a glue line bit, mostly because I do small stuff and setting up the glue line takes longer than planing down the joint offset after a simple jointed edge glue up.

I think if I were doing some production work, turning out a lot of edge joints or making something out of gnarly wood that would be hard to plane, or making something big that I didn’t want to do the work of surfacing all of the joints, I probably would take the time to setup a glue line.

My understanding is that with modern glues on long grain joints a simple jointed edge glued up is stronger than the surrounding wood, no need for any biscuits, glue lines, finger joints, etc.

I think of glue line joints for alignment, not strength.

View coloradoclimber's profile

coloradoclimber

548 posts in 2695 days


#15 posted 1120 days ago

Back to the original issue, I’m gonna second the “is your router plate FLAT across your table”. Any dip or offset will be doubled, not cancelled, when you flip the second piece.

That can be a problem with using setup blocks. Setup blocks are usually short, so they ride down into the bowl of a dished router plate. Then you run your long stock over the table and it rides up over the bowl and you get a different cut than what you thought you had.

The dished router plate problem is an issue with any bit, dado, edge forming, whatever. You set the depth of cut by measuring near the bit and then run a long piece of stock that comes into the dish at the correct angle, then rides high over the dish when both ends are supported off the plate, and then rides low in the dish again at the end of the cut. For dados or grooves it is a real problem, you get a hump in the middle of your groove where the board rode high over the bit.

Did you do your test cut on a short piece and then try your real cut on a longer piece? Could explain why the test cut lined up and the work piece did not.

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