Jump to content

Entry for May 2020's Guitar Of The Month is open - ENTER HERE!

Prostheta

The Roubo-Derived Luthierie Workbench

Recommended Posts

The taper just allows the leading edge of the dowel to negotiate the offset hole in the tenon without hanging up. I'll illustrate this when the time comes.

Share this post


Link to post
Share on other sites

Again, not a massive amount of progress today. These were done the hard way.

Cutting the tenon shoulders with a Japanese razor saw.

progress4.jpg

Semi-finished second tenon. Most of the work was splitting and honing with a wide bevelled chisel. I really wish I had a face float or a shoulder plane for this. I spent a lot of time with the small steel ruler checking for flatness in the faces of the tenon.

progress5.jpg

The completed first tenon.

progress6.jpg

Share this post


Link to post
Share on other sites

Updated CAD plan although I forgot to readjust the top to be longer again. Tried 1,6m to see how it felt and have gone back to 1,8m.

cad9.jpg

Share this post


Link to post
Share on other sites

B-)

I've been collecting very much the same articles for very similar reasons. The current plans I have rough-sketched use standard dimensional lumber build-up in layers to create "virtual" mortises and tenons. The other key parts of making the base sturdy enough is to use offset holes/draw-bolts and run threaded rod through grooves in the cross pieces.

I'll have to remember this thread when I get the plans into digital form.

Ray

  • Like 1

Share this post


Link to post
Share on other sites

Nothing wrong with that. As long as those laminations are glued up reliably there is no reason they shouldn't be just as strong as single-piece lumber. It would save you a lot of time and blistering, chopping and hogging out material. If you drawbore your joints you shouldn't need any threaded rod. The point is that the dowels are flexible enough to snake through the offset holes yet strong enough to pull in the tenon tighter. I split Oak and hammer my own dowels through a drilled steel plate to get the best straight grained dowels possible. The technique was designed to make the best mechanical joint possible without reliance on glue which back then was still hide, casein or gluten. Through bolts with barrel nuts is a good idea....you could drill a bunch of slugs out of 3/4" steel or aluminium, tap them and use coach bolts from the hardware store.

Share this post


Link to post
Share on other sites

Very interesting read so far, will be watching this one closely.

Having completed my first workbench build late last year myself, it's interesting to see somebody elses take on the same topic. I note that you're using blind mortise and tennon joints throughout the frame. I elected to use through-haunched MT joints on the top shorter crosspieces, and through-MTs on the bottom crosspieces, with two wedges at each tennon to provide more "squeeze" in the joint. The longer stretchers in mine were blind MTs to a depth of only 15mm or so, with 4" through-bolts pulling the whole thing together. It's surprising how strong and twist-resistant the frame is, even more so once the extra mass of the top is fitted.

The other thing that convinced me to use through-bolts on the frame was that if I ever need to relocate the bench, I can break it down to pieces that will fit in the back of my car and re-assemble it elsewhere.

Share this post


Link to post
Share on other sites

I elected for permanency rather than having stress applied to connectors. Mobility is a relevant point but I think with this being smaller than most I can just get help shifting it instead.

When you say wedges do you mean tusks or wedged tenons? The former pulls tenons in whilst the latter stops them in the end of a through mortice.

Share this post


Link to post
Share on other sites

Today's work consisted purely of making the jigs for tapping and turning screw threads for the vices....

The diameter of the tap rod was turned on the copy lathe until it measured a good 50mm. No larger otherwise it won't fit in the guide block and no huge amount less otherwise the play will make crappy threads. The circumference of a 50mm diameter rod is 157.1mm, I want the toothing to have a pitch and lead of 10mm with a thread angle of 90° to match the router bit used for cutting the male thread. Using these values I drew a rectangle with a height matching the circumference in CAD with a series of lines every 10mm across it. These were angled so that the bottom of each line corresponds with where the next line begins at the top....pasting this onto the rod creates a continuous spiral....

screw1.jpg

The rod was then chucked up onto a lathe purely for ease of workholding and the lines sawn into approximately 5-8mm deep from halfway up the rod to the very end. The handedness of this rod is for "normal" clockwise-to-tighten motion. The tail vice with the sliding wagon should be left-handed so that it advances when rotated clockwise. Anyway.

screw2.jpg

Half an hour in the machine shop later I had (thanks to Kari anyway) a 45mm long piece of tool steel measuring 13mm wide and 8mm thick ground with a 90° end profile and a 45° pitch. This fits into a graduated slot morticed through the tap rod and is secured with a small wedge. The slots sawn on the rod mate with my handy steel ruler which itself fits into a slot in the guide block. This slot is cut at an angle which corresponds to the 1:15,7 gradient. Each time the cutter was advanced by another mm to tap out the Acetal/Delrin block until a full width of 60mm was achieved. Squeaky and awesome!

screw3.jpg

The finished thread.

screw4.jpg

Oh, and as soon as I was through the door this morning I threw the legs and front stretcher through the thickness sander to remove the black epoxy I used the fill in the surface checking. No longer a fault, it is now a feature.

progress7.jpg

  • Like 1

Share this post


Link to post
Share on other sites

The epoxy greyed up a bit after sanding however after a quick rub down with some wipe-on poly it popped right up. Really pleased with that since it would otherwise have been waste wood. I find it weird that a lot of people prefer wood to not look like it came from a tree. Strange.

Share this post


Link to post
Share on other sites

When you say wedges do you mean tusks or wedged tenons? The former pulls tenons in whilst the latter stops them in the end of a through mortice.

Wedged tennons. Given that my tennons were such a tight fit and then glued as well, fitting wedges was probably a bit of overkill, but I was keen to try a few different techniques to make it as strong as possible.

  • Like 1

Share this post


Link to post
Share on other sites

Good call. They're a lot more permanent than the more knock-down tusked tenons. Great when you go on a hammer-making spree :-)

What working methods are you designing into your bench? I think everybody blends ideas into what they want out of a bench so it would be great hearing it from another perspective. My design is "watered down" with the needs of my studies so isn't perhaps a solely luthiery bench. In fact, a lot of people say the Roubo leg and tail vice setup is not the most ideal....perhaps not but with a few nifty workholding gadgets it still holds its own....

Share this post


Link to post
Share on other sites

Mine was just a bunch of ideas cobbled together from various designs I'd seen floating around the net and, after battling with a crappy fold-up Workmate-style workbench for the best part of 8 years, also driven by a need for something not **** :) The frame is all 45mm x 90mm hardwood framing (close enough for most people to consider as the "classic" 2x4). Each leg is two pieces laminated together to make 90mm sq profiles. Frame is 1.2m long x 600mm deep x 880mm high, and the top is 1.8m long giving a fairly generous overhang at either end. Only one vice installed at present, a chinese Record knock-off that was given to me years ago by my Father-in-law long before I got into guitar building, let alone before I had a bench to mount it to!

A lot of the plans I'd seen suggested making the worktop the same height as your wrist when you stand with your arms by your side. I'm 5'10" and have an intermittently bad back, and found the suggested height a bit too low to be comfortable for long periods of time. An extra 80mm of height was enough to make a difference for me, and I find it's still a good height for me for either hand tools or power tools.

The one thing I did transfer from that fold-up workbench was the wide gap between the two work faces when the jaws were fully opened. That was the only redeeming feature that thing had, and I found it handy to be able to place F-clamps in the gap that could reach over either the front or rear workfaces. As a result I've deliberately made the worktop on the new bench two separate slabs separated by about 90mm. At a pinch you could probably consider it a split-top workbench, but because the gap between the two tops is so wide it's effectively two separate workbenches in parallel. The eventual plan is to install a removable section in the 90mm gap that could be a tool well or bench dog section etc.

P3160546_zpsf2ae9781.jpg

P3160550_zps93956df9.jpg

These couple of shots show how I did the through-bolts and wedged tennons. As those barrel nuts aren't a normal hardware store item, and I couldn't be bothered specially ordering them, I came up with my own solution - just a 35mm hole bored into the stretchers at either end and one edge squared off for the nut and washer to sit against.

P3160548_zpsceaf5da5.jpg

P3160549_zpsf21d89f0.jpg

Since space is at a premium in the shed at the moment I built a removable router table for the bench that just slides over the end on a kind of cantilevered sleeve arrangement. It's a pretty snug fit but with a bit of jostling it can be slid on and off fairly quickly. If I ever get some space back the router table could be easily reused in a purpose-built stand.

P3160551_zps00f8ee3c.jpg

P3160552_zps76f033a1.jpg

Anyway, sorry to clutter your thread with my chitchat. Your workbench is definitely going to be better presented than mine!

Share this post


Link to post
Share on other sites

No no, this is meant to generate discussion rather than being all me-me-me! I was hoping that by documenting my project and the thought processes behind it (and citing sources which I am yet to do properly) a bit of a think-tank could be generated on useful things for luthiers when it comes to benches and workspace.

The whole thing about working height comes down to the tools and work processes carried out. The consensus is that the knuckle-height thing is more to do with the ergonomics of hand planing. A bench like that is too low for say, hand routing over a body or hammering frets. Christopher Schwarz even points out - quite rightly - that the traditional wooden planes used in period Roubo worked in were far taller than the more modern transitional and all-metal planes. Those 2-3"/5-8cm make a significant different to your stance and hence the amount of time you can comfortably do that work. I suffer from a bad back also so this is a priority subject to me.

Your bench is certainly tailored to your work and I am sure that height is paying off. I brought mine up to 860mm which is a compromise between a low planing bench (which I rarely need) and a higher one for assembly work, dovetailing and detail work. Any higher and I can consider something like a pair of foot blocks.

I was thinking about router tables this morning. Traditionally the Roubo seems very one-sided in that you have workholding on the face and end whereas in a larger area you should be able to walk all around it. I briefly considered that if I could afford one, an Incra router lift or similar at the rear right would be of major use and great integrate. Not fully sold yet, especially since I can't afford one!

Share this post


Link to post
Share on other sites

Lovely benches...I still need to do one but I suspect mine won't be nearly so complex or look so good.

Well I don't know. It's nothing to do with how it looks which is just a bonus when it comes down to it. My decision on a Roubo was down to the availability of information on the design, the fact it is solid and also that it can be made to be more like a piece of furniture taking pride of place in the workshop. A bench can adapt to the user - or to a lesser degree vice versa - so making your own will be a personal experience when you apply your own needs. I think that your back will be an issue as well Wes so height is going to be your sticking or success point.

Complex is subjective. A Roubo is pretty damn simple but the workholding can be complex if you let it be. Curtisa's bench is nothing more than a design along the lines of a split top Roubo. You could even get a leg vice in there if it were useful since the top and legs are more or less flush.

Share this post


Link to post
Share on other sites

I was at an antique store the other day and there were a couple of woodworkers benches for sale. They were labelled as 19th century French origin. One of them was fitted with a leg vice, and may have been split top, but I'm not sure if I'm remembering that correctly. What struck me at the time (apart from the asking price!) was how low and uncomfortable they looked. At a guess I'd say they were only 700mm high. There'd be no way I could use something that low unless I was seated.

I should also point out that the height quoted of my workbench does not include the top. The overall height on mine is 930mm, which is close to what's commonly used in kitchen benches in this part of the world - a much more friendly height for my poor old back.

Share this post


Link to post
Share on other sites

Now that is too low. Unless they were meant to be fitted with a pair of leg blocks under the left and right hand sides? Seems a bit odd. 930mm is ergonomically better if you are not putting your back into work for saw, stock sawing and planing so your correlation between it and worktops is valid. If you were trying to use a bench plane however you would find your ability to put your body into the work comfortably somewhat diminished. I am thinking that my choice of 860mm may be a little low however I perceive a lot of my work to be seated with planing and heavy stock work not being protracted enough to warrant a low bench.

Assembly benches are more appropriate for most luthiery jobs I think. I might have to consider some method of raising and lowering overall bench height if 860mm turns out a bad choice. Best suck it first.

Share this post


Link to post
Share on other sites

I have been experimenting with my computer desk lately.I made it 960 mm to the top,and that works well for motions like sanding a body or routing while standing straight.For electronics I built a 50mm thick support platform that sits flat on a bench and I put a towel on it and do my electronics.for typing on my computer I spread my legs wide enough(no dirty thoughts!) to bring my elbows to a 90 degree angle..it "shortens" me by about 4 inches(100 or so mm)

I need a tall bench to keep my back straight.I also have tall bar stools to sit on if I need that.The only thing left now is to decide where to build the bench and do the work...you know...the hard part :P

Share this post


Link to post
Share on other sites

They're great living room furniture if you make them pretty enough!

Now I've mad my first threading tap I could possibly make adjustable-height stools kind of like the ones in photo booths....maybe modified they would be good as stools for working at desks and benches.

Share this post


Link to post
Share on other sites

Not a lot of progress today in terms of project completion however a lot of work was put in.


Wood pile (plus beheaded pin router in the background).

progress8.jpg


Glass jars with alien babies that ensquish wood. Cue one immense 1,90m x 25,5cm x 13,5cm block of Birch weighing about 50 kilos (110lbs). That's HALF of the top anyway. Although I don't have photos, the monster block was jointed/squared, thicknessed and cut to the correct dimensions of 1,80m x 22,5cm x 12,0cm. I'm currently marking her up with the rising dovetail mortices which somehow I have to chop out. BLehhhhhh.

progress9.jpg

Share this post


Link to post
Share on other sites
If you drawbore your joints you shouldn't need any threaded rod. The point is that the dowels are flexible enough to snake through the offset holes yet strong enough to pull in the tenon tighter.
I had thought of that (and I still want to to a set-neck like this), but I decided against it because I know (sincerely hope) that I'll be moving and will want to move the bench. I may still go that route.
Through bolts with barrel nuts is a good idea....you could drill a bunch of slugs out of 3/4" steel or aluminium, tap them and use coach bolts from the hardware store.
That's definitely an idea. I'm trying to remember why I decided to go the threaded rod route. Another idea was to make my own barrel/dowel nuts (pretty much the slugs you mention) by cutting, drilling and tapping rod stock. The final idea was to bore a hole through the cross pieces, flatten the bottom of the hole and use bolts & nuts.

Ray

Share this post


Link to post
Share on other sites

The tough trick is getting the bolts to apply sufficient force over a large enough area to cinch in the shoulders tight securely over the longer term. Big is best I think. Barrels going through the front stretchers front to back and big 3/4" bolts with fat washers to spread the load.

Share this post


Link to post
Share on other sites

The tough trick is getting the bolts to apply sufficient force over a large enough area to cinch in the shoulders tight securely over the longer term. Big is best I think. Barrels going through the front stretchers front to back and big 3/4" bolts with fat washers to spread the load.

I haven't thought about this since last summer when I realized that the bench was not going to be built that season. Now that I'm thinking about it again, drawboring very well may be the way to go. I'll deal with moving the bench when that time comes.

Ray

Share this post


Link to post
Share on other sites

This project has been on the boil slowly with bits and pieces done here and there, so this thread has been somewhat neglected. A few errors along the way for various reasons, but nothing amazing.

So this is where we are right now. The rear part of the structure has been drawbored and glued up leaving the front legs and stretcher free whilst I complete the front half of the bench. The rear half of the bench fits and is pretty much ready to fit after I run it through the thicknesser to match the front. The leg vice just needs the screw routing and the garter fitting. Once that is all in, the last cap end will be glued on. The tool rack/planing stop is on the top of the truck behind the bench. Going to install a Veritas flush fit end vice instead of making my own wagon vice. Might make a shallow shelf between the stretchers with a top-opening door for tools, etc.

In the background on the bottom of the truck you can see the score of visakoivu ("Karelian Birch") which is somewhat similar to Ambrosia Maple in that the strange flecking is caused by beetle attack. Just calculating how to dry it by baking a sample to bone dry :-)

progress10.jpg

  • Like 1

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...