ian maybury
08-24-2011, 9:53 AM
Hi Guys. Now that my dust system is nearing completion I'm thinking about the Roubo style bench that's next on the list - the timber for it (European beech) has been stacked for about a year now. It'll be 8ft x 3ft with a 4in+ top thickness - along the lines of the Schwarz design - but with a Veritas twin screw vise on the face, and a large Veritas front vise with probably full width jaws at the end. Both vises will have dog holes in the moving jaws lined up with the grid on the bench top.
Pardon my bringing up the topic again, but before sitting down to draw it up properly there's a few issues bothering me that don't seem to be covered in the write ups:
(1) The first is how best to get the edge/front face straight when gluing up the top - the laminations at 1 1/4 in + are thin enough that it seems they won't necessarily clamp up dead straight. One option may be to clamp maybe four laminations at a time up along a length of steel box section - which should leave only a little adjustment to be done with a hand plane afterwards.
The same question arises with the hand plane though - how best to ensure a straight and flat edge other than to lay a reference straight edge along it?
It's a significant issue in that it looks to me like the fixture to place and drill the dog hole grid is best lined up off this face/edge - so it needs to be straight - if the grid isn't true it risks pushing frames etc out of square when they are clamped up between dogs. Work will be clamped off this face in use too. (one way to kill all these issues (and others like ensuring the holes are vertical) would I suppose be to park the bench top under a friend's CNC router rig, but transport and handling would be a big deal due to the weight)
(2) The second is the choice of dog hole layout grid. My instinct is a fairly comprehensive grid of maybe four rows of holes on about a 4x4in spacing down the full length of the bench for clamping flexibility while gluing up the laminated curves etc. I want to experiment with.
Lots seem to go for the traditional single row down the front edge though, with a few widely spaced holes to the rear for hold downs, but this seems limiting except for traditional straight edged/rt angled cabinetry - and to be an ideology based decision as much as a practical one. Am I missing something?
(3) The final issue is whether or not to split the top down its length as Benchcrafted and Bob Lang do - and fit a lift out infill/stop strip. The major 'pro' seems to be the additional clamping possibility, but the 'con' is that by splitting the top the structural intergrity is compromised and cross members are needed to link the legs and hold the halves in alignment. This versus the way the traditional Roubo uses the top as a structural member, with the legs set directly into it.
Right now I'm thinking 'not', as dog holes seem likely to provide whatever clamping capability may be needed. Plus it's not a particularly useful stop location. Thoughts?
Thanks,
Ian
Pardon my bringing up the topic again, but before sitting down to draw it up properly there's a few issues bothering me that don't seem to be covered in the write ups:
(1) The first is how best to get the edge/front face straight when gluing up the top - the laminations at 1 1/4 in + are thin enough that it seems they won't necessarily clamp up dead straight. One option may be to clamp maybe four laminations at a time up along a length of steel box section - which should leave only a little adjustment to be done with a hand plane afterwards.
The same question arises with the hand plane though - how best to ensure a straight and flat edge other than to lay a reference straight edge along it?
It's a significant issue in that it looks to me like the fixture to place and drill the dog hole grid is best lined up off this face/edge - so it needs to be straight - if the grid isn't true it risks pushing frames etc out of square when they are clamped up between dogs. Work will be clamped off this face in use too. (one way to kill all these issues (and others like ensuring the holes are vertical) would I suppose be to park the bench top under a friend's CNC router rig, but transport and handling would be a big deal due to the weight)
(2) The second is the choice of dog hole layout grid. My instinct is a fairly comprehensive grid of maybe four rows of holes on about a 4x4in spacing down the full length of the bench for clamping flexibility while gluing up the laminated curves etc. I want to experiment with.
Lots seem to go for the traditional single row down the front edge though, with a few widely spaced holes to the rear for hold downs, but this seems limiting except for traditional straight edged/rt angled cabinetry - and to be an ideology based decision as much as a practical one. Am I missing something?
(3) The final issue is whether or not to split the top down its length as Benchcrafted and Bob Lang do - and fit a lift out infill/stop strip. The major 'pro' seems to be the additional clamping possibility, but the 'con' is that by splitting the top the structural intergrity is compromised and cross members are needed to link the legs and hold the halves in alignment. This versus the way the traditional Roubo uses the top as a structural member, with the legs set directly into it.
Right now I'm thinking 'not', as dog holes seem likely to provide whatever clamping capability may be needed. Plus it's not a particularly useful stop location. Thoughts?
Thanks,
Ian