Thread: Glueing up.
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Old 07-24-2011, 05:57 PM
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derekcohen derekcohen is offline
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Location: Perth, Australia
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Default Re: Glueing up.

Hi Rick

Thanks for your thoughts. By way of reply I thought that I would post a copy of two replies I made to Bill Tindale over at Wood Central, since he raised similar queries.

Reply #1:


Many thanks for your thoughtful reply. You raise many of the issues that are often in one's mind, and the choices that we have to consider. I will respond from my experience here, mainly to clarify what went on in my head and what was unseen in the pictures (not that cool under pressure as suggested by having time to take all the photos!).


You are using way to much glue. It takes a film of glue only two molecules thick to form the bond. Try brushing it on with a small brush. Before assembly scrap all that extra glue off with the spreader, or don't put it on to begin with.


Although it looks a lot of glue in the pictures, the fact is that there was very little squeeze out - the tiniest bead only. Squeeze out was immediately cleaned up with clean paper towel soaked in tepid water. I'd rather that there was a little squeeze out - the merest suggestion thereof - than none as then I am reassured that I put on enough glue.


For glue to work it has to wet both surfaces. If one puts it on both surfaces there is no doubt it has wet both surfaces. I think it a waste of time to glue the end grain.


There are two schools of thought when it comes to one- versus two sides. I have done both. In this situation, with as many dovetails to glue, the open time of the glue would effectively have been halved - that would not have been sufficient (and THEN I really would have panicked!).

With regard end grain, I do agree with you .. intellectually. Emotionally it is another thing ... my fear of leaving some join unsupported gets the better of me.


If you put glue only on one surface(not recommended) then put it on the surface where the excess will be pushed to an outside joint, not an inside corner. In this case glue the tails.


Yes to ensuring that the surfaces coming together do not create a starved joint. I made sure that the glue was a little thicker at the top of the pins. Pushing one end over another does not favour gluing the tails - that does not make sense. I chose the pins because it is easier to spead glue fully over the surface.


I don't risk a partial case glue up and I have never seen a professional shop that does either. Somewhere down the road you will get one of these joints off a bit and not know it till the rest of the parts get added. Glue gets applied one joint at a time and that joint assembled until the whole of the case is done.


I think that if I did this more frequently (2 or 3 large projects a year is my quota, with a dozen small ones thrown in that do not require this kind of pressure), then I would be more efficient and more confident. I have better control working with smaller sections. I wonder how others feel? In any event, your point about having a joint move is taken - which is why I am fanatical about measuring and monitoring the squareness as I go along (you can see several squares being used in the pictures). As I mentioned, clamps are used to maintain the angles, not simply to add pressure on a join.


It is unimaginable that more than 20 min would be necessary to do the assembly. I do often get help applying glue in a complicated assembly. I use liquid hide glue for dovetails. It has slow tack so assembly is aided.


I am in a double-bind with hide glue - I lack experience in using it, and therefore I avoid it. I recognise the advantages regarding repairs (as Warren mentioned below). Help? Rufus (the Golden Retriever) would rather chew any Jarrah than help me. And Aura (my son's shih tzu cross maltese) just bats her eyes at me, then lies down to rest) ..





Diagonal clamping is risky. When the case is dry fit I check for square in the unclamped state. If it is not square then I fix the issue. If clamps are needed to square a case then spring back is likely and the result is unsquare.


I will find out whether there was any springback later - I am in your camp here. I do not rely on these braces to square the carcase. They were just fine tuning - there was a fraction of a mm that I wanted to correct.


There are two times important to glue. One time involves how long the joint can be left exposed to air. This time is typically in the range of 10 min and it of course depends on temperature and humidity. Glue can be diluted with 5% water to increase this time. The second time is how long after assembly can the joint be adjusted. 10-15 min is typical and it depends on moisture content of wood and variety of glue.


Thanks. Good info.


For reference, it is Winter here and the weather is cool (18-21 Centigrade/about 65 degrees F).


Reply #2


Below are a couple of images from the glue up today. The first one was about average for the amount of squeeze out I generally experience, while the second is a little more than average. Both are, I believe, quite a small amount, and far less than I think that Bill was imagining. Yes/No?


First image ..





Second image ...





Regards from Perth

Derek
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