This week I've started working in earnest on my new veneer press. It's going to be of the traditional type with lots of hand screws, and I thought I would do a WIP as there's not that much info about this on the web and it will hopefully be useful to someone.
I'm departing from tradition in that I'm basing it on a torsion box. The reason for this is that I don't have space to have the press set up all the time, so need it to easily dismantle, and I don't want to be shimming and adjusting it every time I assemble it. With a torsion box I will know the platen is flat. As an added bonus it will double as a dead flat assembly table, and by drilling a grid of holes on one side I will be able to flip it over to serve as a base for attaching jigs for steam-bending, laminating etc.
I've started by making this torsion box which is the heart of the whole thing. It is 6' by 3' which is bigger than I need right now, but my intention it to be doing larger work with it in the future, and I only want to make a press once!
The skins are 3/4" BB grade birch ply, the core is 5" deep 12mm mdf. Since torsion box stiffness is mostly related to the thickness of the skins and the depth of the core, this should produce something very rigid. I used mositure resistant mdf, on the basis that it is better quality generally, and most of the things I will be using the press for involve a certain amount of water and heat.
The long edges of the box need to be drilled to take steel rod which will support the cross bars for the hand screws. In order to support these rods I need thick core sections at the edges. I laminated them up from 3 pieces of 18mm mdf.
I then jointed and planed to width all the mdf for the core as accurately as possible, and drilled eight 22mm holes down each of the laminated pieces for the steel rods.
I needed a flat reference to assemble the box on. I used two saw horses, which I screwed to the floor. To them I attached OSB fins levelled with a spirit level, and laid four lengths of 4x2, accurately jointed and thicknessed on top. With the benefit of hindsight it would have been better to have made the fins out of something thicker or attached them differently — they bent a tiny bit with the weight of the box, and I had to wedge them at the ends to compensate.
On this platform I laid the bottom skin, which is the one drilled with holes for attaching jigs. The holes are 6mm at 50mm centres and I had them CNC drilled because I thought I would struggle to get so many spot on, and they need to be very accurate to work well. I got the company that drilled them to also drill the 2' offcut from the end of the board with the same pattern, so I can use it in future to help set out holes on formers etc that will exactly mate up with the holes on the skin (to which they will then be secured with 6mm metal pins).
I had this bottom skin cut 4mm oversize, so I could easily use it as a guide to set out and assemble the core on. The top skin, which was be glued to the core second, was 20mm over size.
The usual recommendation is to use a nail or staple gun to assemble the core. I don't have either, and also the sides were too thick to nail through, and screws seemed like too much fuss, so I used housings to locate and secure the cross pieces.
The lengthwise core pieces were cut and placed individually between the widthwise ones and secured with hot melt adhesive, again because I don't have a nail gun. There's no question that a nail gun would have been a more convenient choice if I had one. Still the glue held the pieces in well enough, and the strength comes from the bond between the core and the skins — the bond within the core doesn't matter very much. The spacing of the core is not quite regular as I needed to dodge the holes in the bottom skin and the holes for the rods at the edges.
Then it was a question of making sure the core was dead flat using a straightedge and spirit level and a handplane. I was quite obsessive about this and took a good hour on each side. obviously there's no going back once the skins are glued on.
I put a polythene dust sheet on top of one of the skins, laid the core on top and did a final check for wind with a spirit level. I then spread glue over the top of the core and laid the other skin on to it. I then secured it to the core with screws (I pre-drilled clearance holes in the skins). The screws are set below the surface and I filled the holes with filler later on.
Once the glue had gone off I flipped the assembly over and drilled through the 22mm holes along the edge and out through the skin, using one of the 2x4 supports to eliminate breakout. The holes are drilled through the second skin using the same procedure once it is glued on. I was a bit paranoid I would forget to drill through the first skin before glueing on the second which would have left me in a real fix, but fortunately I remembered!
I did the drilling like this (ie drilling the core first, then drilling through the skins once assembled) so that I could take advantage of the accuracy of the pillar drill, which would have been impossible once the box is glued up.
When only one skin is attached the structure is not very stiff at all. However as soon as the second skin is glued on (using the same procedure as for the first) it immediately becomes enormously rigid.
Then it was just a question of trimming round the slightly oversized skins with a router using a straight bit with a bearing, chamfering the edges, and generally neatening things up.
I was originally planning to paint the skins with epoxy paint, but had visions of the paint getting into the small holes on the drilled side and being a nightmare to clean out. So I have decided just to give it a couple of coats of wiped varnish/oil and to wax the platen side now and then.
The holes at each end are handles to help with moving it about. It's quite heavy.
I haven't made a torsion box before, but having done one I'm quite impressed. If I ever need a new workbench I will definitely consider using torsion box construction.
So that's a start. There is still the press assembly and the legs/frame to make. And 32 hand-screws to fit....
I'm departing from tradition in that I'm basing it on a torsion box. The reason for this is that I don't have space to have the press set up all the time, so need it to easily dismantle, and I don't want to be shimming and adjusting it every time I assemble it. With a torsion box I will know the platen is flat. As an added bonus it will double as a dead flat assembly table, and by drilling a grid of holes on one side I will be able to flip it over to serve as a base for attaching jigs for steam-bending, laminating etc.
I've started by making this torsion box which is the heart of the whole thing. It is 6' by 3' which is bigger than I need right now, but my intention it to be doing larger work with it in the future, and I only want to make a press once!
The skins are 3/4" BB grade birch ply, the core is 5" deep 12mm mdf. Since torsion box stiffness is mostly related to the thickness of the skins and the depth of the core, this should produce something very rigid. I used mositure resistant mdf, on the basis that it is better quality generally, and most of the things I will be using the press for involve a certain amount of water and heat.
The long edges of the box need to be drilled to take steel rod which will support the cross bars for the hand screws. In order to support these rods I need thick core sections at the edges. I laminated them up from 3 pieces of 18mm mdf.
I then jointed and planed to width all the mdf for the core as accurately as possible, and drilled eight 22mm holes down each of the laminated pieces for the steel rods.
I needed a flat reference to assemble the box on. I used two saw horses, which I screwed to the floor. To them I attached OSB fins levelled with a spirit level, and laid four lengths of 4x2, accurately jointed and thicknessed on top. With the benefit of hindsight it would have been better to have made the fins out of something thicker or attached them differently — they bent a tiny bit with the weight of the box, and I had to wedge them at the ends to compensate.
On this platform I laid the bottom skin, which is the one drilled with holes for attaching jigs. The holes are 6mm at 50mm centres and I had them CNC drilled because I thought I would struggle to get so many spot on, and they need to be very accurate to work well. I got the company that drilled them to also drill the 2' offcut from the end of the board with the same pattern, so I can use it in future to help set out holes on formers etc that will exactly mate up with the holes on the skin (to which they will then be secured with 6mm metal pins).
I had this bottom skin cut 4mm oversize, so I could easily use it as a guide to set out and assemble the core on. The top skin, which was be glued to the core second, was 20mm over size.
The usual recommendation is to use a nail or staple gun to assemble the core. I don't have either, and also the sides were too thick to nail through, and screws seemed like too much fuss, so I used housings to locate and secure the cross pieces.
The lengthwise core pieces were cut and placed individually between the widthwise ones and secured with hot melt adhesive, again because I don't have a nail gun. There's no question that a nail gun would have been a more convenient choice if I had one. Still the glue held the pieces in well enough, and the strength comes from the bond between the core and the skins — the bond within the core doesn't matter very much. The spacing of the core is not quite regular as I needed to dodge the holes in the bottom skin and the holes for the rods at the edges.
Then it was a question of making sure the core was dead flat using a straightedge and spirit level and a handplane. I was quite obsessive about this and took a good hour on each side. obviously there's no going back once the skins are glued on.
I put a polythene dust sheet on top of one of the skins, laid the core on top and did a final check for wind with a spirit level. I then spread glue over the top of the core and laid the other skin on to it. I then secured it to the core with screws (I pre-drilled clearance holes in the skins). The screws are set below the surface and I filled the holes with filler later on.
Once the glue had gone off I flipped the assembly over and drilled through the 22mm holes along the edge and out through the skin, using one of the 2x4 supports to eliminate breakout. The holes are drilled through the second skin using the same procedure once it is glued on. I was a bit paranoid I would forget to drill through the first skin before glueing on the second which would have left me in a real fix, but fortunately I remembered!
I did the drilling like this (ie drilling the core first, then drilling through the skins once assembled) so that I could take advantage of the accuracy of the pillar drill, which would have been impossible once the box is glued up.
When only one skin is attached the structure is not very stiff at all. However as soon as the second skin is glued on (using the same procedure as for the first) it immediately becomes enormously rigid.
Then it was just a question of trimming round the slightly oversized skins with a router using a straight bit with a bearing, chamfering the edges, and generally neatening things up.
I was originally planning to paint the skins with epoxy paint, but had visions of the paint getting into the small holes on the drilled side and being a nightmare to clean out. So I have decided just to give it a couple of coats of wiped varnish/oil and to wax the platen side now and then.
The holes at each end are handles to help with moving it about. It's quite heavy.
I haven't made a torsion box before, but having done one I'm quite impressed. If I ever need a new workbench I will definitely consider using torsion box construction.
So that's a start. There is still the press assembly and the legs/frame to make. And 32 hand-screws to fit....
