Roubo Bench Issues and Questions
I am about to build a new bench. My existing bench is 18 years old, has been modified many times over the years to keep pace with my changing approach to woodwork, and is showing its years. It is small - about 4'10" long. It is too wide - about 26". The top has been planed down so many times that the dowels I used to orientate the boards all those years ago are now showing half their thickness. Although the legs are spindly, the bench is really rigid as it is bolted to the wall (the new bench will be placed about 2 ft from the wall). The Record 52 1/2 vises are now hopeless. The front vise racks and the tail vise does not open unless you hold down the release lever while you turn the handle. And it is too dark. The Karri top may look exotic in pictures, but it does not reflect light well.
http://www.inthewoodshop.com/Furnitu..._m2feaf3e6.jpg
The bench has been a good friend but I still find it amazing that I managed to do so much work on it. I procrastinated and avoided building another as I generally dislike building shop furniture. Or using good wood that would better be used on furniture for the home. But now it is time for a new bench, a better bench.
I like the simplicity of a Roubo. I thank Chris Schwarz for his research and the information he disseminated. It has been educational.
Since building a Moxon vise (for dovetailing) a year ago I have come to recognise that my face vise needs (for planing edges) would now be best met by a leg vise. I plan to build one with a 2" Lake Erie wooden screw, while the tail vise is a Benchcrafted wagon vise (both USA).
Generally I try and build as much as I can from recycled timber. I find a lot of old Jarrah roof trusses. These are dry and hard. They will be turned into the base.
Today I dug out the rafters that I thought would work best. These are 3"- 3 1/2" x 4"- 4 1/2" and around 80" long. I should be able to get four legs at 3" x 5". I am aiming for a 34" high bench.
http://i13.photobucket.com/albums/a2...oughbeams1.jpg
Question 1: Your thoughts on dimensions for the legs? What are the dimensions of your benches legs?
The top is to be 4" thick, 21-22" wide and 6 ft long (perhaps 6'6" if I can squeeze it), built from European Oak (which means it likely originated from Eastern Europe). One of the members of my local ww club bought a shipment imported by a failed business, and was selling it at the price for Tassie Oak, which lacks its stability and texture. This was jointed and thicknessed for me, and has been "acclimatizing" (aka lying around) for several months. There has been minimal movement.
http://i13.photobucket.com/albums/a2...uild/2-top.jpg
http://i13.photobucket.com/albums/a2...ild/3-top2.jpg
Two boxes at the top ... BenchCrafted tail vise and woodscrew ...
http://i13.photobucket.com/albums/a2...ld/4-vises.jpg
Question 2: I plan to add rectangular dogholes. How far apart are yours (my thoughts run to about 3")? I plan to get them as close to the edge of the top as possible - it depends on the positioning of the BC tail vise. For those with the BC, how close did you place yours?
Question 3: Also for those using the BC end vise, what is the length and width of the cut out for the vise?
My intention is to build a wooden replica of the steel screw leg vise designed by BenchCrafted. The key feature here are the wheel guides. I plan to use roller skate wheels. Any other wheels to consider (with a smooth running internal bearing)?
Question 4: I believe both Chris Schwarz and Jameel Abraham recommended that the leg vise screw is placed 9" below the top of the chop. Anyone do anything different, or would have feedback on their experience?
Regards from Perth
Derek
On vises and dogs and bench heights.
Hi Ian
The choice of tail vise was made on a number of factors, one of which was the space available for the bench. You have used my bench a couple of times and will recall that it is placed against a rear wall in my garage/workshop. The length of the bench is limited by a cabinet, to the left, and a door, to the right. It comes down to the longer the bench, the shorter the tail vise ... or, the longer the tail vise, the shorter the bench.
The Benchcraft tail vise is notable in that the handle remains in one position, that is, does not "screw out" or "screw in" in length. This translates into a short vise, which means I can build a longer bench. The bench size increases from a little under 5' to a little over 6'. This may not sound a lot, but it is a massive change for me.
I was initially planning on building my own version of the Benchcraft wagon vise. However, when Chris Vesper visited with me last year, he mentioned that he had purchased the BC tail vise. When I asked why he had not simply built his own - since he is a top class machinist - he explained that the design of the vise places great stresses on the mechanism (it screws at the side of the captured dog so as to run close to the edge of the bench), and that to accommodate this, the steel work needed to be heavy duty ... and that the BC was built like the proverbial tank. He did not believe he could replicate it. That sold me on the BC for the tail vise.
I hope to get to the bench dogs tomorrow. These will be rectangular, not round, so I have to prepare them before I glue up the bench top. Why rectangular? Simply because I believe that they will hold work more securely than round dogs. They have a broader face and will not twist. Plus, I wonder how many bench (dog) builders realise that the dogs need to incline slightly (I am using 2 degrees) towards the work piece? This is difficult to do if drilling for a round dog. Yes, it is possible to cut and angle a flat upper section of a round dog, but this thins and potentially weakens the dog, making it more susceptible to bending under stress. A rectangular dog is more work, both in planning and build, but it worth it. This does not preclude one from adding holes for bench accessories, such as hold downs.
So today I plan to finish off the legs. Their dimensions are 5" wide and 3 5/8" deep. I have cut the tenons, and what is left is to prepare one for the leg vise and all for the mortices for the adjoining stretchers. While I will not complete the base until after the top is done (as the length of the stretchers is determined by the dimensions of the top since all facing edges will be co-planar), I need to have everything ready to receive the top once it is glued up just so that I can work on the top.
To decide the length of the legs I first had to finalise the height of the bench. The present bench, which I built 18 years ago, was a remnant from a pre-handtool era. Much modified over the years to better deal with the demands of handtools, it still retained that one feature of the powertool user - height. It is 34" high. Too high for comfortable handplaning at my 178cm/5'10".
Chris Schwarz recommends the "pinky test", that is, the height of the bench should be situated where your pinky joins your hand when your arm is held at your side. I did this and the result was a bench height of 30". To test this out I place a double layer of bricks in front of the bench, and planed a board while standing on the bricks ...
http://i13.photobucket.com/albums/a2...nchheight1.jpg
Interestingly, this did feel so much better. It moved the focus of strength from my arms and shoulders to my hips and legs (which is what one is taught in karate). So the length of the legs was calculated for a bench top of approximately 4" thickness (it will end up a little under that), and the tenons were cut. Pictures of the legs tomorrow.
One other point: One change begets other changes. With the lowering of the bench, I shall need to build a new Moxon dovetail vise. The whole idea of the Moxon is to raise the work up high. The existing vise was built for a 34" high bench. To work with the same ease, the new Moxon will need to work 4" higher. Hence a new, taller Moxon.
Regards from Perth
Derek