Glue
  • Sounds a bit basic but what is strongest glue for wood. Doing some experiments to make gear wheels from solid wood and intend to glue 4 segments for grain alignment and strength. I guess PVA but could be wrong. After glueing it will be turned in a lathe.
    Thanks for any answers

    George
  • I do not know about the strongest, but I have the tendency to stick with what works, and as far as I am concerned that is bog standard PVA white glue. It is non toxic and if you get some on your hands it is no problem to remove.

    The only thing with PVA is its tendency to creep under load, which means, as far as we are concerned with our small clock gluing jobs, that when you glue 2 pieces of solid wood together and they shrink/expand at differing rates you will notice this on the joint as it will stand proud on one side as the joint has "crept" rather than held. This is very much a "can happen", and the amount the joint stands proud is really very small.

    As a carpenter I have also used PU (Polyurethane) glue, which pretty much bonds to anything and gives a very strong joint. The problem with PU is that it really does bond to everything, clamps,hands,hair,cat in fact anything within a 10m radius, and once its stuck that's it.

    Another kind of common wood glue is aliphatic resin, such as Titebond, but I have no experience with it, but seems to be also a good option.

    Dave
  • Thanks Dave
    Will stick to PVA (no pun intended)
    Had clock plans printed out on card as opposed to paper and again want know best glue?
    In past used paper plans stuck with Pritstick wax type which can lift on scroll saw, need stronger glue now and thought about wallpaper paste. Want it to be water soluble for ease of release.
    Met Paul Davis through this forum who is a great guy who planed me some walnut to make some cogs. These will be segmented for grain alinement and will beef up from plans of primus.
    Will add pics as i go along
  • For mounting paper patterns to wood/metal I find 3M "Remount" usually available at art stores very good. Not that cheap ~$30 for a large aerosol can. I just spray the back of the pattern and the wood and use a small 4" drywall spatula to spread it flat with no air bubbles. It will stand up to scroll sawing and bandsawing. It has trouble with heat which I find using it on steel and grinding or sanding to the line as the part can get quite hot. It will typically curl up off the part if the part gets hot. This is not a problem with wood parts though. When you finished cutting out your part you can get your thumb nail under it and peel it off.

    For making your own plywood (for gears) I think epoxy is the strongest but it can be messy to work with. Better to take your time and make one piece of ply (say 8" x 8" at a time. I did this with maple once and West system epoxy. 3 pieces (1/8" x 8" x 8") laminated together at 90 deg to each other. I still have a piece in my basement and it's been completely flat for 10 years. Now for the horror story. When I did this I made 8 of these (24 lamminations) at once. I glued up 3 layers then a tin foil separator then another 3 layers on top of that then another tin foil etc etc up to 24 ply. Then I put my "gravity clamp" on it - a 1.5" thick 12" x 18" block of steel. Of course I did this on the kitchen table (granted it was protected). It was at this point I saw the folly of my idea as viscous forces and fluid dynamics came into play. The middle of my 24 layer sandwich kept trying to slide out sideways and epoxy was starting to squish out like a slow motion honey waterfall. I managed to clamp all four sides (like clamping a pillar) which kept my top gravity clamp, the bock of steel, stable. Net net, it worked and I got good gears but it was very messy and with the hardened spillage I broke up the following morning I was able to offer up epoxy throwing stars for months afterwards.The wife was not amused!
  • Thanks Dayrl

    Nice to get feedback for my questions.
    The way i glue my cogs is not to make ply but to utilize grain for strength in teeth from solid wood. I have made pie sections from 1/4 " walnut to create a disk - turned on lathe to create depth. Whilst on lathe i pop a 1 mm hole in center and use this to align gear template printed on card glued to back which is flat and then cut teeth.
    So far all gears apart from escapement have been made and run very well in frame.
    I have noticeable run out or truth by a few mm yet when placed on a smooth surface they appear flat as a witches tit so must be arbour drill holes slightly out.
    As for glue i go for PVA and found an adhesive for wallpaper borders is a good one for the plans to wood.
    One other tip - get a wood burning stove - more cogs have gone into mine than decorate the room and at least you get some heat from the blood sweat and tears.

    George
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  • When I stick patterns to wood for scroll saw cutting I first cover the wood with masking tape and then use PVA glue to stick the patten to the tape. Obviously have to be careful not to over wet the pattern and stretch it, but I've never had problems and when left to dry the pattern sits very flat on the wood. When the cut is done, peeling the pattern off is dead easy compared with the spray mount I used to use as all you have to do is peel the tape off. The added benefit that I saw somewhere on youtube is that the adhesive on the tape acts as a lubricant for the saw.

    I started doing it when I ran out of spray mount and have kept to it since as I find it very satisfactory.