I took off a little time, to investigate the best ratio of liquid resin to catalyst when using Unibond 800 glue (the liquid part). It turns out that 10:1 by weight worked best; and, best of all, this was confirmed by Darryl Keil, at VacuPress. The normal working range for Unibond 800 is 7:1 for a “fast” reaction (translation: shortest open time and quickest set times); a ratio of 12:1 results in a “slow” reaction time (longest open time before applying clamping pressure). As I understand it, the “ideal” ratio is 10:1.
Using a 12:1 Unibond 800 liquid-to-catalyst ratio, with 2-inch thick machined walnut boards containing 7 – 9% moisture, and ambient temperature of 75°F, I managed to create some glue-ups that failed (that is, open up slightly on one edge). Since it was the week-end, and I could not access the folks at VacuPress, I decided to try laminations using 10:1 Unibond 800-to-catalyst ratio.
In the context of my work, all this means that in this case the 12:1 ratio was not the optimal ratio. Based on my results, I suggest that readers try the mixing ratios that give them the best results. I cannot tell why a ratio of 12:1 did not work 100%; but I know that in this case the 10:1 ratio worked great.
I am happy to report that no failures have resulted when using the 10:1 Unibond-to-catalyst ratio. Therefore, I decided to proceed to machine the mortises in the legs.
In this photo I use the tall stand I made some time ago, to allow machining the tenons on longer boards, such as required for this table; it worked great, with minimal vibration, by simply clamping the stand to the workbench:
I will use this stand on the workbench when I make the stand-up desk; that piece will require aprons close to 60 inches long.
Once the initial setup is complete, machining the mortises is trivial. But it is important to keep track of which leg goes in which position:
I prefer to always check for square during dry fit. It is much easier to make corrections at this stage, prior to gluing up; it is also a good preparation for clamping strategy:
The longest parallel clamps I own are 48-inch Besseys. As a result, I had to purchase some Bessey K body clamp extenders:
In case something goes wrong – and sometimes things happen – I like to have a spare leg. It is time well spent:
Next: Since the table top is already finished, I will glue up this base, and prep it for the finish.