I am about to finally build a proper workbench, out of maple, but I am wondering about clamping– the total amount of pressure required for a 2.5 in thick lamination is more than my set of pipe clamps can deliver.
I don’t really want to buy big bar clamps for the one job, so I am considering drilling through-holes in the assembly and using threaded rod to clamp it, adding a pair of thinner outside layers afterwards to hide the holes.
I expect the threaded rod will be able to deliver more pressure than a pipe clamp because there will be no twisting or rotating forces as per the heads on a clamp.
Is this a good idea?
An update–
The lamination went well, I used another thread on the site to validate my choice of epoxy (I had a lot as it happened). I used something more than half a litre in the lamination (ok I am a Canuck). Some tips for anyone following down this path–
The epoxy is great, the weather was cool so I had well over an hour before the glue started to get tacky, I bought a cheapo touch up paint roller and used (destroyed) this rolling epoxy onto all the boards. There were 14 layers in the laminations, both sides were rolled then placed together, the whole lamination is something over 6 ft long, and roughly 2.5 inches thick.
Using threaded rod also went well, I bored all the holes on the drill press, one every 6 in (probably excessive) and used 5/16 threaded rod. Washers deformed, need more or thicker next time.
Next time, I would cut slots in the lamination so I could ensure the top was aligned, epoxy is very slippery and I had some movement up to 1/32 which I sorted out with a power planer afterwards, hand planing and winding sticks to come… I even had some 3/16 thick beech strips I could have used. Normally I use a few biscuits in a larger lamination just to get the alignment. Biscuits are meant for yellow or white glue so I wasn’t thinking this part through clearly–they still would have aligned the top. Clamping cauls can also work but I find less clutter is better when I am working under pressure so biscuits for this kid.
I was worried the threaded rod would be left in the bench forever, but it popped out with a few hammer blows here and there and breaking the glue off by pulling it through with the nut on one end in other spots.
Drilling all the holes took over an hour– 12 holes per layer, 14 layers, 168 holes. The drilling jig had a consistent error to the right, this was ok except for a few short boards that I guess I flipped end for end before drilling– so once in the lamination and tension on the rods I couldn’t get some boards to butt up. Next time I would drill larger holes, I used 7/16th, or tie the boards in any layer together first.
Much more fun than buying a ready-made benchtop, much more work too, _not_ much cheaper. Wood was >$100, $70 in threaded rod and h/w, I used half of a $90 1 litre epoxy bottle (G2, Industrial Formulators).
Best regards and thank-you for all the tips,
Ted Wilson
Edited 5/16/2005 10:57 pm ET by tedwilson
Replies
This will work. Just follow a few principles:
The surface on which you clamp must be flat, so your benchtop becomes flat.
As you tighten each bolt, check for flatness all the way with a straightedge.
Thank-you, those are some good pointers. I was planning to use some cauls to keep things flat. I might get fancy and use a torque wrench at the end.
Much appreciated,
Ted
When you talk about benchtop lamination are you speaking of gluing boards face to face. Always been curiouos of the terminology. thanks
I bought some 8/4 shop-grade maple and ripped it to 2 3/4 strips, I will be tipping each strip on edge and gluing them together. Initially I was going to glue them up as per any normal panel, but decided to rotate the boards to have most of the grain running roughly as per quarter sawn boards--perpendicular to the surface of the lamination.
After ripping, I have let the boards sit in the shop for a number of months (mostly because I've been busy), and some have developed a fair amount of twist. I will likely cut most of the boards to something like 18-24" lengths and then joint and plane to consistent dimensions to avoid too much waste jointing out twist and cup.
With all of these short boards, I'll laminate them together like laying bricks in a wall. The whole process will duplicate the type of bench top you can buy from companies like lee valley, but with somewhat larger individual pieces, and a bit thicker. Sometimes the fun is in the doing.
Best regards,
Ted
Ted
you might look for those double pipe clamps. They span the wood and are attached to a pipe on each side. When you tighten them, they don't bow like single pipies will.
I think Jorgensen makes them. Just buy some new heads and use your own pipes.
Amazon??
Peter
jpswoodworking.com
If the wood is not too badlly twisted and warped [you said that it is cut down to 18-24" boards] then pipe clamps are all you need. Much easier than adding threaded rod. If the bending of the pipe clamp when you tighten it is what worries you, then place the wood on a caul that is about 1/4" higher than the pipe clamp laying on your bench. THis will remove most if not all of the pipes bending effects. Peter
In college I worked in a laminated beam mill and this is basically the method we used to clamp the beams. Threaded rods ran on the outside of the beams (top and bottom). The nuts were threaded on to the rods that went thru a caul and post. We had the posts because we had to bend (camber) the beams to keep the sag out of them on a long span. The back side could be permanently bolted to another caul if you want to keep these around for butcher blocks or whatever. We used air drills to cinch up the press. We could make beams 6 feet tall (planer width limitation) up to 105 feet long in our little mill. We'd stack up 10 - 50 beams of varying dimension. The width was dependent on the 2 by boards we finger jointed end to end. 2 x4s, 2x 6s, 2x 8s, 2 x 10s, and 2 x 12s went thru the jointing machine I worked on. Dip finger joint paddle in glue pot, apply glue to jointed end of board, assemble joint, feed the board down the line, apply glue to next board, etc... Heck of a way to pass 10 hours. I glued a lot boards together that summer.
I think your idea will work great.
In our case (and in benchtops) we laminated them face to face, whereas in wood working it seems most laminations are edge to edge for table tops or panels. Of course veneering is a good example to of laminating.
Ah plywood, another summer job... ;-)
Regards,
Ken
"Do as you would be done by." C.S. Lewis
Edited 5/3/2005 3:09 pm ET by kenshep
Before I bought the lumber for my bench I was planning to just buy an end off a laminated beam salvaged from some building. I've seen the salvaged beams on trucks but never got farther than that.
I always thought it would be funny to have a 4+ in thick bench that was basically chainsawed off one end of a salvaged beam.
It's interesting to hear how they are made. I guess the planer moved instead of the 100+ft board...
Nope. We opened the doors on one end of the building and fed the beams thru the planer. The superintendent took a ride thru the planer one day. The knives weren't going, but the feed rollers were. took him right thru. He lived, but still walks with a cane.
We had three or four power lifts in the building so getting the beams lined up to feed thru the planer wasn't a problem. On the big ones we did have to open the double bay doors though and have someone stop traffic on the street. If they were fine finish beams, we had to putty and sand knot holes. That seemed like an all day job on some of those puppies. I was there for the summer, I can't imagine doing that my whole working life.
Now that's one planer I'd hate sharpen the knives on.
Regards,
Ken
"Do as you would be done by." C.S. Lewis
Our planer, also 72", had a knife sharpening attachment built in it, Took about 30 minutes to sharpen all three knives. We built laminated arches too. The real fun was getting the knee of the arch through the planer as you had to use hoist to not only bring arch forward, but latterally too. We had a tool called a German jointer that was actually a 13" wide hand held power plane. At that time I weighed about 130 pounds. It was a bear to handle. Due to the gyroscope effect you had to hold until it quit spinning just to change directions. I bet you know what a "dutchman " is.
If you mean a patch made with wood to replace a large tearout, (usually caused by a knot), then yes. We would rout out the area to be patched, square the corners with chisels and glue in the replacement. We'd then belt sand it smooth. I didn't get to do much finish work, that was for the best work in the plant, so the senior guys got to do it. When people called in sick, they'd have me help out. Summer help got clean-up, firewatch, finger joint dobbing, (since replaced with a machine), and other glamorous jobs. I did spend a week finishing telephone pole cross pieces made out of douglas fir lams. We'd patch those with some smelly concoction that will last about 100 years. I think they dipped in cresote or some other preservative after they left my hands. I didn't mind that work so much, it was outside in a shed with an open wall. Pretty peaceful compared to the plant. (chop saws, planers, router, air wrenches, rf glue machine, cranes, metal clamps hitting the floor and the dust collection system). When that big planer fired up (usually swing shift), it sounded like a 747 was revving up. Day shift assembled the beams, swingshift assembled the long boards to laminate and also planed beams. Graveyard was breakdown. They would take all the clamps off the beams and move them off the assembly racks. 3-7 a.m. was firewatch. I'd work a ten hour shift and do firewatch (and cleanup) occasionally. $11 an hour at 18 was good money back in the late 70s. Not sure they are making much more these days.
Regards,
Ken
"Do as you would be done by." C.S. Lewis
threaded rod ...
My good bench was made that way.. HAY I thought that was MY idea!
Face-to-face hickory.. I used 6 (each) 1/2 inch threaded rods, thick washers, and yes, nuts..
Just as the other post suggested check your table level while tightening.
I would suggest that you tighten each nut in a sequence.. Sort of like doing head bolts. ie.. not right to left down the line.. Do something like.. Start at rod at one end. Tighten a little... Go to the other end.. tighten a little... Move toward center alternating toward the center rod..
I glued up two sections that were finally glued together after the glue dried for a day.. Not sure I needed to but trying to glue up all that wood in one shot seems like asking for trouble to me.
Edited 5/4/2005 6:03 am ET by Will George
Threaded rod is a good idea, I have made quite a few benches. Most of the benches were softwood benches for different manufacturing companies. They were used for assembly tables. I used threaded rod in all of them, but not so much in place of clamps as added insurance to keep the top together forever.
Last month I made a bench for my 8 year old grandson, it's only 26" high. We'll change the legs when he grows taller.The bench is construction grade fir that I air dried in the shop for about 8 months. The top is 3" thick, 20" wide and 72" long with a shopmade vice.
When gluing up your bench use a slow setting glue like polyurethane. Yellow glue sets up to fast to be able to thread the rods and clamp.I suggest you make it up in thirds, then glue the three sections together.Make sure your stock is straight and flat.If you use 5/16" threaded rod ,bore 7/16" holes. The face pieces should be counter bored for the nut and washer and the socket on the wrench.I have pictures of my grandson's bench below.
That's really a sweet bench! I wish my grandpa would have made me one of those when I was 8!
Nice job.
PeterPeter
jpswoodworking.com
Now THAT bench is cool!
Did you get him a set of little tools too? Just jokin'
I bet he just loved it!
I gave Nicky some cordless drills, a brace and an eggbeater type drill.He had gotten the typical toy tools for Christmas, not much a boy could do with that stuff. I gave him a few other tools, a real hammer 13 ounces, a tape etc.
mike
Will you be my grampa?
Let me add that standard 3/4" black iron pipe pipe clamps exert about 1000 pounds of pressure. Optimum psi for PVA adhesive is about 200 psi for hardwood. That would mean a pair of clamps (above and below) every 7-8 inches or so.
Personally, I doubt you will get as much pressure from threaded rod as you will from pipe clamps. Plus you are going to have a real big job drilling and aligning all the holes you will need for the threaded rod. And, the threaded rod must be removed or you will have distortion from seasonal expansion and contraction.
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