03 August 2010

The workmare - 3

pencil test
The workmare still needs to be finished, but it is usable?

- The twin vise seems good, I like it. It is made of two oak left over glued together. I should have glued an extra board (softwood) in between to leave room for drilling dog holes. As it is now 3/4 inch holes are to big, I need to find a thinner solution. Anyway I need a solution to compensate the lack of tail vice and be able to clamp sideways.

- I roughed up the hardboard to make it less slippery, but I think that using 1/2" MDF would have been better, as I already damaged the top with my circular saw and hardboard does not leave much depth for error.

- The stability, seems good. I tried out my pencil test, putting a carpenters pencil upright and keeping it so when hammering in all three directions. With a mass proportion close to 50 to 1, over 60 pounds for the top and 1,2 pound for my mallet there is not much moving.

- The stability is less when planing, as I can put a larger mass behind it. I even have the impression that weighting the top down did not change much as adding the gravel did change the oscillation frequency of the top from maybe 30 hz to something like 10 hz without changing much to the amplitude. It can be improved by making the legs and joints stiffer. Increasing the L shaped legs from 4" (by 4") to 5" (by 5") more than doubles the stiffness of the legs (the formula is bh³/12) but not necessarily the stiffness of the joints. Adding diagonals to the legs is probably more effective
adding toes to the legs

- When planing towards the vice the workbench tended to tilt over as most weight is at the front not in the tool tray. A solution is to add toes to the front legs. No one wants to be crushed under the weighted top. All in all if I have to redo it I would add cheap concrete slabs, from the garden center, to the lower tray, to weight the workbench down and avoid the potential danger of a weighted top solution.
leg clamp

- Holes for attaching stuff is a work in progress, I will add them in the top and the legs depending off my needs.