clamping a 1/2 thick butt joint, how long before removing clamps

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  • #308463
    5ivestring
    Participant

    Hi, I searched the forums and didn’t find an answer.

    I’m doing several small projects all at the same time for my niece, easy projects, no problem. Well, except I’m prepping the stock now and have run out of clamps.

    The stock is 1/2 thick, varies in length from 7 inches to 15 inches. A lot of them too.

    I almost went and glued them together before I cut the pieces, but had too many knotts to deal with so I ended up cutting to rough size.

    I have 8 pipe clamps, 8 bar type clamps. I clamp the ends together with the pipe clamps, and clamp two pieces of wood top and bottom to keep the stock level with the other clamps.

    The big question, I am more than sure has been covered. How long to clamp? I’m hoping people will say 4 hours is enough as long as I’m not going to use the wood until much later. 8 hours, man, that sets me back time wise, might have to buy more clamps. Longer than 8 hours I’ll be forever. Release the clamps too soon and what’s the point of clamping then.

    I’m clamping pine. I’ve listened to Pauls videos repeatedly, and don’t recall he talked about the length of time except when he did the chess board and he said he was going to leave the clamps on overnight because end grain was so hard to clamp. Luckily for me, I not clamping end grain. I do miss a lot on the videos though, that’s why I watch them over and over.

    With my pipe clamps, I can clamp 2 sets (4 pieces) at one time, so I do 4 sets and then out of clamps. I have enough pipe clamps to clamp up 4 more sets, but not the bar type clamps. I’m not really worried about removing the bar clamps early, but the pipe clamps concern me.

    #308477
    Mike I
    Participant

    I have researched this question a lot before too, and find people saying anything from 30 minutes to two days…

    My guess is that Paul doesn’t want to be too prescriptive in his videos due to the variety of circumstances that could be involved.

    You may find that internet answers on this topic vary a lot. There are many variables involved and sometimes people will plainly say so. Sometimes people just have different experiences which they think must be the “correct” answer to all situations.

    Drying/clamping time Variables could include

    The type of glue.
    The amount of glue used.
    Temperature of environment
    Humidity of environment
    The wood species.
    How dry the wood is
    How tight the joinery is.
    Whether you cleaned up squeeze out immediately or left it for later
    The amount of clamping pressure needed to hold the joint in intended position.
    The amount of stress the finished join will endure
    etc, etc

    I work mostly with pine, live in a temperate climate and usually leave 12 to 24 hr+ in clamps to be “on the safe side” depending on temperature, but I have the luxury of not being in a hurry.

    I guess you have three choices or so…

    #1 Experiment with <=4 hours clamping times. What is the risk to your project of a glue joint opening up or failing vs the extended drying/clamping time? You may be able to answer that question yourself better than anyone. Maybe a failure is no big problem, maybe it is…

    #2 Buy more clamps and use more space to do more glue-ups in parallel and leave them longer. Cost/reward judgement is up to you.

    #3 Revisit your expectations on reasonable clamping timescales and find ways to work your schedule around the waiting periods for glue/clamp-ups. Even though this may not be the most optimally efficient way a mass producer would work due to the context/activity switching, it can work well on a small scale and this is the method I usually choose – I don’t get to do extensive woodwork every day, but even if I did, I would I still have 8 hrs+ of each day where I would be asleep let alone anything else…

    I hope that helps somehow

    Mike

    #308491
    5ivestring
    Participant

    @dragon32

    Hi Mike,

    Your answer is excellent. I thought more about this question, and kind of felt the same, but was hoping that there was some general consensus. I can see how there are too many variables.

    I clamped my first pieces and left them clamped for 8+ hours, then removed the clamps and set the pieces aside, and clamped the next set. The next day, the first set is very solid.

    I think as you suggested, when I finish this project(s) for my nieces, I will do a clamp test, 1 hr, 2,3,4,6. 8 I already feel comfortable with, although I don’t use the pieces until the next day.

    Thanks for your response.
    Gary

    #308608
    deanbecker
    Participant

    Wiuldnt it depend on the. brand and type of glue? Most glue bottles tell you how long before the glue sets up

    #308614
    5ivestring
    Participant

    @dragon32 @deanbecker

    Here’s my findings by trial and well, trial. Absolutely not scientific. don’t take this to the bank.

    Most glue bottles do give a set time, and a total set time, but to me that is pretty much right but not totally covering everything.

    Nothing I did will cover everything either. But here’s what I did.

    I clamped some pieces of wood, all pine, and let them stay clamped for 2 to 8 hours. A couple a lot longer, but that was not what I was after.

    What I found was after 2 hours, the pieces were pretty well stuck together, I think clamps could have been removed and let the pieces cure longer. But when I did try to split them after the 2 hours, they mostly broke at the glue joint. 4 hours was a whole different story. Those pieces were set pretty strong and when I separated the pieces (with the help of a hammer), the wood splintered, the glue joint held fast.

    Now these were’t butt joints, just two pieces glued together maybe 1 inch none end grain pieces.

    Later, I was cutting some butt joint pieces to size and the scrap was 1/8 to 1″ wide. the thinner ones broke near the glue joint, kind of half wood splitting and half glue joint. The thicker ones broke in the grain of the wood, not the glue joint. Those had set up over night.

    So, I’m guessing, and this is just a guess, 4 to 6 hours you can release the clamps, but the glue isn’t cured yet. 8 hours is better, but again the glue isn’t fully cured, but the clamps aren’t needed. Over night clamping, and you will sleep very well.

    For me, if it is a high end project, I’m clamping over night. But for the projects I am doing for my nieces, 4 to 6 hours is plenty of clamping, but don’t use the pieces yet, let them sit. But that does free up the clamps.

    2 hours, I’m not happy with at all. Just too weak in my mind.

    I’m sure Paul would have a lot to say about this as his 50 plus years of experience verses my hours of experience are worlds apart.

    Gary

    #308618
    Mike I
    Participant

    @5ivestring thanks for the update and sharing your experimental findings.

    I hope you now have a much better idea of the trade-offs for your scenarios! Sounds like you do.

    #308619
    deanbecker
    Participant

    Good job that’s a lot of good info. Did you feel after 2 hours that when broken you could recramp and save your work? Doesn’t sound as if.
    Which would mean if you had gaps in your boards and pulled them together they might pull apart at the glue line at 2 hours .
    I enjoyed your findings. Thank you.

    #308630
    5ivestring
    Participant

    @deanbecker

    HI Dean,

    The pieces that broke at the glue joint after 2 hours, looked to have a good even contact with each other. About even amounts of glue on each piece, no gaps or holes. Something your building that is not real important, I probably could have added a bit of glue and re glued them. Better would have been to clean off the old glue then re glue. (When I say I could have just reglued them, I could hear Paul’s voice saying “We always try to do it the best we can, because we are Craftsmen” I bet he would get the shivers reading this. In truth, I am working on perfection even on these projects. I’m the only one who will know, but that’s good enough.

    Update of breaking pieces. Two butt joint, 1/2 wide, about 1 inch long. One snapped about a 1/4 inch away from the glue joint, the other right on the joint. They came from the same piece of wood.

    One other MAJOR factor, a big one. Depending on how I was holding the wood before breaking them might have very well affected where the breakage was.

    The projects I am am doing are small containers to hold flowers, candy or other things to place on a table to sell at events. A small wheelbarrow, create, trays, basket (of sorts), sort of a step stool with trays.

    The girls wanted gave me the dimensions and wood of choice, 1/2″ pine. They wanted 2 of each. I only got wood for one set first and I’m glad I did. the 1/2″ is just too much over kill on strength and weight. 1/4″ would have been strong enough for what they want, and look so much better.

    Also they gave me lengths, widths and height by just looking at a tape measure. The create to me is too tall, the tray is good except for size of wood. Step stool tray is perfect.

    All that I mentioned because if your going to do a project and especially if your going to use real expensive wood, making a mockup with cheaper wood could save you money and frustration.

    All things you’ve heard before, probably know. But first hand experience can sure be a good teacher.

    Gary

    #308633
    deanbecker
    Participant

    100% in agreement
    We determine our quality of work. Ourownselves because we are the ones that see it and judge it
    Your work and thoughts are appreciated
    Dean

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