How do you position and level bar clamps for flat glue-ups?

[stephen thomas]

In the late 80's i designed a system for Pony I-bar clamps after getting a commission to build a set of curved church pews, 11' long each.
For the seat blanks, it was necessary to clamp enough 3/4" thick x 2-1/4" vertical x 12' long laminae to make 3 seats at once, bent to a plywood form made to the closest pew's inside radius/curve.

For that project, the reason was that i fudged making 3 different forms for the changing radius as the seats progressed back from the focal point. At the given radius, the change for subsequent radii was so small that the error over making 3 forms to also accommodate the 2 spaces between 3 seats, was less than 3/8" drop at the center of the back 2 pews IIRC. IOW, negligible and imperceptible.

Anyway, a fool-proof method to level 4 lower clamps in a flat plane was necessary as the basic support on which to lay the form, register it solidly to the foot of all the clamps so it (the form) did not have to be overly heavy to maintain its correct shape, while bending some 60 or so 3/4" strips + spacers and cauls to it. Twice. (for 2 sets of 3 pews). Ever since, it has been a convenient, adaptive system for any sort of glue-ups that have to be flat in at least one plane. Including the starting platform for moderate size boxes (cabinets) that won't fit in the box clamp. Plus any size cabinet or entry doors

I've wondered at times if it has any commercial potential, but never quite convinced myself that a need exists in the larger world.
Wondering how other people address the problem?

smt

[Kevin Jenness]

I can't quite picture your setup. When clamping flat panels with glued edge joints I rest the material on p-lam covered bunks that put the center of the stock near the height of the clamp screws. I have a number of bunks of various lengths at hand near my 4' x 8' melamine covered assembly table.

[Maurice Mcmurry]

Dad made himself something very similar sounding but based on 3/4 inch Pony pipe clamps recessed into a torsion box. His was for mortis and tenon face frames. I like the look & idea of the pinwheel spinning clamp rack that I saw in the video of the Thomas Moser furniture factory.
I lay my clamps out on my folded over ping-pong table workbench. It is two layers of industrial particle board supported on carefully leveled sawhorses.

[Cameron Wood]

I do like Kevin except that I'm not familiar with the term bunk- I just use sticks. Pipe clamps in particular don't stay flat so having the stock resting on the pipes doesn't work out well. I beam bar clamps are better, but can still flex.

[stephen thomas]

Yeah - kind of forgot the picture
but it was also sort of half hearted intention not to influence replies.

12' long W4 x 13 shown was originally clamped between 2 lally columns in my old shop with a couple short 2 x 4's on end to set the working height & keep it from sliding down as the work piled on.
Legs were made for it after moving to new shop here in NY state. It is possible to glue up 16' parts with the 12' I-beam by extending the wood 2' past on each end, and adding free clamps directly under and over the extended areas.

I often work with cantilevered 5' Pony I-bar clamps. However, they can also be moved to straddle the bar to balance if necessary. For the original church pew app, they were set to straddle, but the form covered the brackets and had clearance holes to get a socket in to the level adjuster screws. I've worked out a system so the bars can straddle flush, (different adjuster screw system accessible from below) but never needed it. Even with full length glue ups to near the 5' bar capacity, all the other clamps added, and sometimes a second layer. For times when it gets heavy as in the latter case, i prop the front. I beam feet allow the option of a slide-able front rest to reduce the cantilever. However, some cantilever is usually desirable for working.

Cantilever is also useful for space such as times when a glue up is being done on both sides, say clamping a couple cabinet doors beside each-other on one side to dry, while assembling & gluing the next pair on the other side.

smt_glueclamp4.jpgImg4332August 08.jpg

Always imagined making more brackets, never needed them even with glue-ups piled a couple high.

Best to immediately add top clamps as the lowers are tightened.
4 clamps to level and build on does not limit the total number of bottom clamps, of course. Others are added directly as the assembly progresses.
This also means that other than the chosen number of attached base clamps, none of the additional clamps need to be Pony. Can even be pipe clamps.
Usually the addition of top and bottom clamps will alternate, but it is often practical to just add top clamps as gravity tends to resist bowing in that direction even with somewhat more top than bottom clamps.

[Kevin Jenness]

That's an interesting arrangement, somewhat like a JLT clamp rack. Even if I had room for one I would prefer a flat bench for support of heavy assemblies- that's a lot of potential stress on a few cantilevered arms plus I don't feature laying parts directly on clamp bars, inviting dents, glue blobs and glue stains. Those Jorgy I-beams are stout but they do develop burrs on the top edge and are harder to keep free of glue than formica and melamine. Just my $.02.

[stephen thomas]

I like the look & idea of the pinwheel spinning clamp rack that I saw in the video of the Thomas Moser furniture factory.

My neighbor who sometimes helped me out, did more cabinet work than i did. Tons of cabinet doors & panel glue-ups. He had a carousel. (Ferris wheel style)

I needed something more flexible with more capacity for millwork including the aforementioned pews, carriage house and entry doors, large tops, etc, etc.
Even just endlessly gluing T & G solid nosings onto plywood, to chop up for cabinets, book cases, and built-ins. Gluing up multiples at a time.

smt

[Kevin Jenness]

I do like Kevin except that I'm not familiar with the term bunk- I just use sticks. Pipe clamps in particular don't stay flat so having the stock resting on the pipes doesn't work out well. I beam bar clamps are better, but can still flex.

"Bunks" = large sticks. Mine are sized somewhere around 1 3/4" x 2 1/2" to match up with my I-bar and aluminum bar clamps depending on orientation. I despise roly-poly pipe clamps for most purposes.

[Maurice Mcmurry]

Something to keep the glue squeez-out from from making black or rust colored stains is important. A nice feature of the torsion box is that the wood does not lay on the pipes or bars. My solution when the clamps just lay on a flat surface is to put a small piece of plastic box tape over the pipe or bar underneath the glue joint. I like galvanized pipe because it does not leave a stain. The clamp clutches do not grab on galvanized as well as they do on black iron or steel bars.

[stephen thomas]

Drat.
So the verdict is in.
I've wasted 35 years!



NO seriously you hit the crux of the matter for me here:

Even if I had room for one I would prefer a flat bench for support ....

I've never had the area for a bench. let alone, say 4 x 8 or 4 x 12. I don't even have a woodworkers bench.
With this set up, i move the machines (most on wheels) out of the way, hang whatever length bar clamps on the rail, positioned as useful, say at the rail positions for a door.
Then spend however many days doing glue-ups, and then take the clamps off and move the machines back for use.
If the glue-ups are something small, like say a couple flat panels or cabinet doors, then i only hang a couple clamps and can probably work them between the machines.

Notice double-sided finish rack in background - this area is also my spray finish booth, with the wing doors opened at the end, and the fan in the sliding barn door outside (not shown)
tenoner24.jpg

In this shot a 3' x 7' door, one of a set of 7 doors is being faced off with the clamps out of the way.
Notice gang drill and pin router on wheels, moved to the back wall of the spray booth.

DSC_0010.jpg

Besides that, i often stack the lumber for a job under the glue rack (covered with a sheet of plastic.) with a bench in the room, i would literally not be able to fit 500 or 1,000 ft of lumber on the first floor to have access for a job. (I can put lumber to the loft through an outside door, and bring it down one piece at a time)

...of heavy assemblies- that's a lot of potential stress on a few cantilevered arms

Like you, it used to worry me. Besides just placing props under a large glue up, i actually made a rail system that positions on top of the feet, and can be slid and tilted to support under the clamps, more or less to the front as preferred. But it turns out i only use it when the clamp system is set up as a transfer table, with a pattern on top for large build-ups of "weird" stuff. Generally, so long as the clamps are hung and leveled by sight, the flex is just enough to be a feature, not a bug.

There's only about 300 ft of 8/4 pine scored from a pattern shop auction here, but it is accessible to work off of for this job, until it gets moved to the loft.
Lots of cantilever and no problems.

DSC_0006.jpg

After making patterns/forms,
Here they are in use:

Doris 2.jpgDoris forms.jpg

plus I don't feature laying parts directly on clamp bars, inviting dents, glue blobs and glue stains. Those Jorgy I-beams are stout but they do develop burrs on the top edge and are harder to keep free of glue than formica and melamine. Just my $.02.

I used to have PVC pipe with a slot cut to slide over the tops of the bars. Of course they gradually get chopped into an accumulation of smaller lengths over time, and ganged as useful.
But again, i found i hardly ever used them for my work. Last winter i got tired of the storage issue and threw them out. I do place slips of poly under glue lines on some work. Mostly for the things the system was designed for, it is not necessary. There is a separate box/drawer clamp (Lancaster) here that is good for production gluing boxes; and cabinet doors with extenders at the jaws.

[Kevin Jenness]

Drat.
So the verdict is in.
I've wasted 35 years!

Not at all. Judging by the work you've posted here recently you are a master at producing sophisticated millwork in a small space. Your setup works for you and thanks for sharing it. Small shops doing large jobs have to be flexible. I used to do assembly on a 4x8 torsion box that could be set on edge against the wall when needed, now I throw a sheet of melamine on my cnc router table in the same spot.

[Cameron Wood]

"Bunks" = large sticks. Mine are sized somewhere around 1 3/4" x 2 1/2" to match up with my I-bar and aluminum bar clamps depending on orientation. I despise roly-poly pipe clamps for most purposes.

I have larger bar clamps but they are heavy. My projects are all over the map size-wise & so are the pipe clamps, the flexibility trumps performance. Have a few parallel jaw ones & don't like them, & one Dubuque one which is nice and light but won't be getting more.

[stephen thomas]

I used to do assembly on a 4x8 torsion box that could be set on edge against the wall when needed, now I throw a sheet of melamine on my cnc router table in the same spot.

I don't use it for assembly, but do use the 24" x 92" table on my planer for laminating flat stuff.
And for a flat reference.
Wish it was wider. For all kinds of good reasons but have not found one within reasonable moving distance with a wide table that is short (under 12' travel)
That machine will not go out of here until i do, feet first. Too darn useful.

planer firehose press.jpg

Looking lower left corner, a foot of the clamp rack is just visible behind it. Another reason the clamps are detachable - so the planer table can pass by.

[stephen thomas]

Another use for the clamp rack is as a porch post lathe. Given the tightness of my space it is good if all the machines can multi-task.

smt_splitbedlathe9.jpgsmt_splitbedlathe12.jpg

[Wes Grass]

[COLOR=#333333]

I don't use it for assembly, but do use the 24" x 92" table on my planer for laminating flat stuff.

I've done the same, but its a giant pain with clamps, with the hollow under the table. The firehose being something I never would have thought of ... or been able to implement in my garage.

That machine will not go out of here until i do, feet first. Too darn useful.

I'm thinking head first ... thru the planer ...

Back to nature ... 'feed the birds ... and coyotes ...'

Although I wonder, if I were ground up into 'meat', would the cat still be interested in biting me? ;-)