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How many clamps for a glue up?

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Forum topic by Greg In Maryland posted 194 days ago 1025 views 0 times favorited 23 replies Add to Favorites Watch
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Greg In Maryland

387 posts in 1623 days


194 days ago

Topic tags/keywords: clamps

Hi all,

I have to glue up several panels—approximately 24×40 inches and 24×24 inches. I am tired of using pipe clamps and screwing up. So in hopes for getting better results, with fewer hassles and hopefully much lower stress, I purchased five Jet parallel clamps.

I know, I know, you cannot have too many clamps, but at $60 per, I really cannot afford more clamps. So, will five parallel clamps suffice for a panel that is 24×40 inches? I can always throw on some bar clamps or pipe clamps, but I want the parallel clamps to do most of the work.

Any thoughts or recommendations would be greatly appreciated.

Thanks.

Greg


23 replies so far

View CharlesA's profile

CharlesA

1212 posts in 422 days


#1 posted 194 days ago

I prefer parallel for panels as well, but it might be helpful if you could explain why the pipe clamps screw it up for you.

-- "Man is the only animal which devours his own, for I can apply no milder term to the general prey of the rich on the poor." ~Thomas Jefferson

View Gerald Thompson's profile (online now)

Gerald Thompson

356 posts in 859 days


#2 posted 194 days ago

I have never had a problem with pipe clamp unless it was my mess up. I invariably use cauls to keep it all flat.
http://www.wkfinetools.com/contrib/hendersonM/makingCauls/makingCauls-1.asp Go to Mike’s site and you can learn how to make your own cheaply, easily and fit for a life time of use.
You will have enough claps for your project. Remember to dry fit and clamp to test things first.

-- Jerry

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pmayer

565 posts in 1690 days


#3 posted 194 days ago

It depends how wide your boards are. The wider the boards, the fewer the clamps needed. Picture the clamping pressure projecting onto the panel at roughly a 45 degree angle to the clamp itself. if you put your clamps into position and sketch these lines onto the panel you can get a sense of where your clamp pressure coverage will be.

I would typically want more than 5 clamps on ta 40” panel. I suggest using the pipe clamps in addition to your new bars. Don’t over tighten then and you shouldn’t have any problems. If you are having problems, I would also suggest gluing up these panels in two stages. That way you can focus your attention on flushing fewer joints, and you will likely have better luck with this approach. Plus, if you have a portable planer you can run each smaller panel through the planer before gluing up your final panel size, and that way you only have to sand one glue joint flush.

-- PaulMayer, http://www.vernswoodgoods.com

View CharlesA's profile

CharlesA

1212 posts in 422 days


#4 posted 194 days ago

Cauls really are a key. In addition to the link proved above, I’ve found this one from highland woodworking to be really helpful in making and using cauls.

-- "Man is the only animal which devours his own, for I can apply no milder term to the general prey of the rich on the poor." ~Thomas Jefferson

View waho6o9's profile

waho6o9

4821 posts in 1202 days


#5 posted 194 days ago

View gfadvm's profile

gfadvm

10717 posts in 1315 days


#6 posted 194 days ago

Jerry, That’s a great link. I thought there was a way to make cauls with a jointer (or did I imagine that since I’m not much of a hand tool guy?)

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View alysonsdad's profile

alysonsdad

5 posts in 1265 days


#7 posted 194 days ago

how many clamps do you need? more than you could ever buy! lol

-- Illegitimi non carborundum

View paxorion's profile

paxorion

571 posts in 670 days


#8 posted 194 days ago

I’m still curious as to why pipe clamps aren’t working well for you.

-- paxorion

View Bluepine38's profile

Bluepine38

2876 posts in 1710 days


#9 posted 194 days ago

I am curious about the pipe clamps also, I started using pipe clamps in high school shop and used them
since, because I could not afford better clamps. I now have more clamps, but still use the pipe clamps
quite a bit.

-- As ever, Gus-the 75 yr young apprentice carpenter

View Greg In Maryland's profile

Greg In Maryland

387 posts in 1623 days


#10 posted 194 days ago

Thanks everyone for the replies. Excellent information, as always.

In a nutshell, it’s all about juggling. By that I mean ensuring that the black Iron rods don’t touch the wood, keeping the clamping pressure centered on the thickness of the wood, ensuring that the clamp pads don’t fall off (hot glue does not work all that well) or the pads break or get in the way, all while ensuring adequate clamping pressure, correct alignment, etc., etc. I can get plenty of clamping pressure, but control and finesse is lacking.

Additionally, the f-style clamps I have are Harbor Freight specials and just are not robust enough. They twist and bow, and have their own set of problems.

My hope is that the parallel clamps will eliminate a few of the complexities, and let me focus on the important aspects of glueups.

Thanks again for all the thoughts and comments.

Greg

So, five Jet Parallel Clamps are either with me or on their way to me.

View JAAune's profile

JAAune

774 posts in 942 days


#11 posted 194 days ago

We mostly use parallel clamps now but it’s for speed and not for joint quality.

If you want to get maximum effect from pipe clamps open them up just a little wider than they need to be for the glue up then loosely place a piece of packing tape across the pipe wherever it is likely to contact glue. This allows you to press the boards tight against the pipe without black spots happening. Don’t press the tape in place because that makes it hard to remove later on.

This really helps keep the panels flat. Adding a few clamps across the top to balance the ones on the bottom will also help.

Regarding the number of clamps needed, it’s generally safe to assume that the pressure will spread about 45 degree angle from the clamp face. To ensure there are no problems just make sure you have enough clamps to allow the pressure areas to overlap. The wider the boards being glued, the less clamps you need. I’ve gotten away with far less clamps on some glue ups but it does create a risk of gaps showing up after the dried glue is scraped away.

-- See my work at http://remmertstudios.com and http://altaredesign.com

View pmayer's profile

pmayer

565 posts in 1690 days


#12 posted 193 days ago

I agree with the comments suggesting that pipe clamps should work. I have both pipes and parallel bars, and get good quality results with either. There are reasons that I reach for each of them in certain situations, but for gluing up panels I will use either one with equal confidence. Also, I don’t believe that cauls are necessary for gluing panels, particularly if you glue up in stages. Having said that, I know that many people love them and they can help to overcome some technique problems so they might be one means to solving your problem.

A couple things that might be helpful;

- Many panel glue up problems are caused by distortions in the stock. If you aren’t getting your stock perfectly flat with square parallel edges, you can’t fix those problems with clamping pressure. Take your time at the jointer. If you see any gap or misalignment during dry fit at the glue table, take the offending board(s) back to the jointer.
- Another common problem is boards moving around under clamping pressure as a result of too much pressure too quickly. Tighten the clamps in two phases. First, just tighten them enough so that there is good contact across the joint, and force the joints flush. Then, after the glue forms its initial tack (5 minutes or so, depending on which glue you are using) tighten them further. If you crank to full pressure right away (without cauls), you will have a hard time keeping things aligned.
- As I mentioned in an earlier post, gluing up a panel in multiple stages makes it much easier to get good results. Glue up two separate panels, plane each one, joint the two glue edges, and glue them together. You will reduce your hand sanding time by a lot, and produce a lot less dust in the process. Don’t skip the step of re-jointing the glue edges for your final panel glue-up, as gluing up the stage 1 panels can distort the edges enough to cause problems with your final glue-up.
- Using a glue with a bit more open time like Tightbond 3 can help a lot with larger panel glue-ups. It gives you a couple more minutes to force all of your joints flush and makes the process a bit more leisurely.
- If you are having a hard time keeping the panel positioned properly on the pipe clamp to center the force (and it sounds like this is part of the problem), just push the panel down flat to the pipes. If you alternate clamps on top and bottom, your panel you will offset any distortion. If you glue up the panel in stages any staining will easily come out when you plane the sub-assembly. If you get the panel out of the clamps soon enough, staining shouldn’t be much of a problem anyway. If you have one face of the panel that will not be displayed in the final project, then put that side down in the clamps, and suspend the top clamps with just a bit of clearance to avoid staining.

-

-- PaulMayer, http://www.vernswoodgoods.com

View AlanBienlein's profile

AlanBienlein

141 posts in 1299 days


#13 posted 193 days ago

I only use pipe clamps or my wilton bar clamps. I’ve tried the bessys and they sre just way to fussy and over priced.

As for the black marks I don’t have that problem but I also don’t believe in using the black pipe. Nothing but the galvanized 3/4” ridgid electrical conduit as it’s less expensive than the galvanized 3/4” water pipe. I never never ever had a problem with slippage using this pipe and no black marks.

As for holding the clamps I made me some stands out of scrap plywood and the wonderful thing about doing it this way is there is no need to clean off the work bench to do a glue up.

As you can see there is no need to clear off the work bench to do a glue up using these style of clamps.

View a1Jim's profile

a1Jim

112008 posts in 2202 days


#14 posted 193 days ago

Lots of good suggestions , I find most problems with panel glue ups stem from few mistakes people make, one is that people don’t alternate their clamps (one on the bottom and on on the top) another area is having you clamps uneven (one side of clamp being much higher than the other end) and not having the clamps parallel across your panels making for unequal pressure that can cause distortion of your panel. Another area is when using pipe clamps don’t let the pipes touch your wood (no black marks) an lastly don’t need a lot of pressure(some people tighten the clamps as tight as they can (another area that can cause distortion of your panel). Even though parallel clamps are nice to have you can get good results from almost any clamp that will give you enough pressure to glue up panels.

-- http://artisticwoodstudio.com Custom furniture

View jdh122's profile

jdh122

351 posts in 1442 days


#15 posted 193 days ago

gfadvm:
Here’s a short finewoodworking video that shows how to make cauls with a jointer:

http://www.finewoodworking.com/how-to/video/how-to-make-cambered-cauls.aspx

-- Jeremy, in the Acadian forests

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