Jointing Heavy Slabs
Furnituremakers discuss how to get a glue-ready edge on heavy Walnut slabs for a bookmatch table top. December 31, 2013
Question (WOODWEB Member) :
I'm up against my largest table top to date which will be 10' long by 4' wide. Itís coming from book-matched walnut slabs 12/4 thick. On smaller tables I chalk line the two halves, free hand it on the band saw and joint it for cleanup. I fear these pieces will be too large for my system. I've thought about bringing them to a neighbor shop that has a straight line rip and then clean it up by hand or getting a reasonable line then finishing with a straight edge and flush router bit. Does anyone have any thoughts? Also, I've used biscuits and then bow ties on top. Is that enough for a piece this big?
(Furniture Making Forum)
From contributor M:
The tool that you're after is a joiner. There are stationary power joiners, as well as joiner planes (hand powered). Both will do the trick. A straight line rip makes a crappy edge along a line that is only marginally straight; a skill saw with a straight edge will likely be a better choice for the initial cut.
From contributor U:
A straight line rip will do a great job of getting the edges close. With a fresh blade and flat slabs, there are SLR machines capable of ripping a glue line edge, no problem. So that would be my first step. If you still need to clean up the edges, you could use a router and a straight template. Take very light cuts because it is easy to telegraph bumps into the edge. If the depth of cut is too much for a single bit, you can use a pair of bearing flush bits: one with the bearing at the end, and one with the bearing at the shaft. First cut along the straight template, then flip the slab and use the other flush cut bit to reference off of the straight edge of the slab.
From the original questioner
That's just about what I was thinking. The reason I am cautious about using my jointer is the weight of each slab is going to be over 100lbs. The handling will be a problem, but I have also had my jointer lose alignment in the bed which is frustrating. I fear the weight at the end of that 76" table would be asking for problems.
From contributor D:
If you don't have a SLR, an outfeed extension for support on the jointer helps. A table, not an outfeed roller, that gets you support just over half the length of your slab will make handling it no problem. Really, technique will make jointing heavy slabs like this easy. Spending hours on end jointing heavy stuff you tend to try to find easy ways to do things. With support just over half the length of your slab, you won't need to bear down to keep the forward end from tipping down. If you haven't tried this - it's a revelation on saving your back: soon as you clear the cutter push only a bit farther until the slab begins to tip forward.
With the weight supported just at the center on the edge of your outfeed table, you can literally move it up and down with fingertip force, like a playground teeter-totter. A roller will let it roll off this apex point. At this point, you can let it tip forward until forward edge touches the floor. The easy move then is to keep pushing forward on the slab until it's standing straight up. It's surprisingly easy to carry by letting it then lean back against your shoulder, with your arms down and straight, like marching soldiers carrying a rifle. You're standing straight up, you're arms aren't straining, and even gripping isn't so hard because such a large area is in contact with your arm and shoulder that the friction of it trying to slide down helps you hold it as you walk around to the other side. Really heavy, wide slabs at this point could also be dog walked on each corner. It's all a balancing act. Letting it down from vertical I like to keep a wide stance, hands high as possible, and step back slowly, hand over hand, until it's almost horizontal again, with one end on the floor. At this point you set it down with as much overhang as possible on the infeed side of the jointer table, again like a teeter-totter, then walk around to the back and lift it easily, ready to push through again. With practice, you can go like this all day without straining or bending over.
From Contributor O
At some point things get so large that you have to stop taking the work to the machine and reverse the process by taking the machine to the work. You get to determine the point - part of the joy of being your own boss. You have good advice above for either approach.
From contributor S:
I use my sliding table saw to straightline big slabs like that. I use a cam clamp on both ends to hold it down. You'd need at least a 10-1/2 foot stroke to do slabs that long, and a good rip blade. Another way is to nail a straight board to the opposite side of your slab, and use that against your rip fence on your table saw. You'd need at least a 12" blade to cut through a 12/4 slab.
From the original questioner
I have not thought of creating an out-feed table. I feel like the last time my jointer got out of true was because of long heavy pieces tipping at the end of a pass. It will be a help in the future and creates a feasible way to run the slab. Is a full inch bowtie necessary? I've seen some articles suggesting that 1/4" is enough.
From contributor H:
I do thick ones in that situation. I've never tried it and had it fail. Maybe somebody else here knows more. But thick is no harder than thin.
From contributor C:
When faced with a similar situation I laid the two large slabs to be jointed on my CNC 3/8" apart and ran a half inch router bit between them using manual control. It didn't matter if the line was perfectly straight or not - when pushed together the two pieces joined up with no gap. Of course, that method is limited by the width of the CNC bed, but I could join two pieces almost 3' wide on my machine.
From contributor Y:
I can understand that a 10'x2'x3" weighing most likely over 240 lbs would be quite daunting on a 6' jointer. If it were not bolted to the floor all kinds of bad things could happen. Proceed with caution and best if done with infeed and outfeed table as already suggested. I would probably follow the earlier advice of bringing the tool to the work if I was in your shoes. My jointer weighs in at 2K lbs. but muscling around slabs that big is hard work at best. Besides if the reference face to the fence is not dead flat the edge attained will not be any better than shooting it with the router and a straight edge. Trueing from there on with a hand plane is par for the course in my opinion.
The butterfly dovetail keys work their best when you provide equal support on both top and bottom faces - the deeper the better as well. If you only were only applying them to the top then the bottom may open. I feel that they have a much more important role than decoration and that is the mechanical union of two edge joints when and if the glue fails.
If you were to look at the underside of George Nakashima's table's you would also find he adds a screw to each side of the butter flies. This undoubtedly holds them in as reoccurring expansion and shrinkage cycles will eventually loosen the key and it could just fall out one day. It would not be surprising to hear that he may have learned from experience. The top ones of course will look better sans screws and probably will not have and fear of those falling out.
From Contributor G
Festool will rip a glue edge line. We use the rough ripping blade, the fine blade and then clamp together, making for a nice joint.