Workbench construction � open questions

Re: New questions about the Tucker 7

thomd


>What happened to the light, I can't see anything.

A stantion is a tower attached by it's base. The example I am most aware of is the object that supports life lines on a boat. As far as I can see there is one stantion on my vise. The one on my bench does not look far enough under the bench to contact your tray. My top is similar to yours except it hasn't the tray. If you have metalworking capabilities you could make your stantion out of a single rod that is hardware bonded to the underside of you top, it would have a very minimal footprint, not that I think that is necesarry, but it would be pretty sanitary.

All the stantion does is allow you to clamp off the sloted bar that controls tilt attitude of the vise in the Y, Z, axis. I hope that helps. :0)

I left off the foot actuation to this function, but I don't believe that affects what you are doing. Foot activation is a good thing, I just didn't like the look. I will probably work out something I can live with at some point.

Re: New questions about the tail vise 7

thomd


>They always seem to be separate parts. There is probably a way of putting them together with wedges or something, but screws or threaded rods hardware bonded are a good method.

Stanchion

Dirk Vogel


>Hi Thom ! I already knew what a stanchion, or stantion like you write it, is for. It's not its function I'm worried with, it's the semicircular extension of my benchtop my question was about. As far as the distances between stanchion and bench top edge are concerned, I just took instructions from the Tucker Operation Manual. They say the Tucker stanchion must begin at a distance of 4 1/2" from the edge. As the stanchion's length is 4 1/2" as well, the stanchion screws need holes nearly 9" away from the edge. My benchtop half is only 8 1/2", that's why the screws would fall into the tool tray if I didn't do anything.

Re: trestle + cross beams updated

thomd


>Normally with this kind of thing there are pairs of wedges in each tenon, coming form different sides. Otherwise unlike the single vertical tenon they tend to walk out, or they set the piece at an angle (but you ave several stretchers). I suppose if you found a nice wood that was a little gripy, made sure the back was hollowed and a little rough.

Re: Short grain

Paul M. in San Diego


>I agree with Thom. Your approach may look more architectural than mine, but would result in very weak grain at the thinnest section.

I honestly do not think you need this at all if you have a sizable stretcher. I did it only because I was cutting corners to maximize the area available for a tool box. Just use a wide stretcher and you're done!

One concern I have

Derek


>That's a nice looking bench!

I have not read all responses so if this has been addressed forgive me. My concern is for wood movement between the top and the stretchers.

Looking at your drawings, it appears that the stretcher protrusions (I'm not sure what else to call them) which fit into the bottom of the benchtop may need some clearance for wood movement. The stretcher long grain is parallel with the width of the top. The width of the top is face grain (weather quarter or flat sawn). The top will expand and contract considerably but the protrusions on top of the stretcher will not change much at all.

I suggest you provide clearance on the front and back edges of the stretcher-protrusions to allow the top to move when it needs to or you may end up with unwanted cracks in the top.

Re: strechers

thomd


>"Attention ! First, I have no longitudinal strechers near the top, only the two in the middle of the trestle."

Right, those two you just notch the top and the bottom of them half an inch, and they lock up solid. I think I did that,and the hated cross tenons, on my Flintstones bench. Only one stretcher.

"And second, my cross beam strechers on the trestle's top won't be attached to the bench top ! That's why I had my question about the splines."

Right but as long as the stretchers stop the X movement in your bench and the tresles at the ends stop Y movement, then the main remaining force that the stetchers could resolve would be a twist, the base going diamond shaped when viewed from the air. The engagement of your top supports will stop that, unless your top deforms. And the tenon shoulders such as they are will resist the racking also.

The only problem with this approach is aesthetic, you have to leave enough room for the stetchers to penetrate and be removeable so there are visible shadow lines around the shoulder area, if the shoulder doesn't flow around the whole tenon, but :

a) you have that problem on the wedge end anyway

b) that ship preety much sailed when your stock got so thin

c) there are ornamental things that could be done to hide this

Re: Weight ratio

thomd


>OK, I could buy that, who said that by the way. Though in practice it takes about 20-30 pounds of structure to support the top, and any base I have built was pretty easy for one person to move by hand, maybe 60+ pounds. Tops are really heavy.

Re: Stanchion

thomd


>Right, well my first thought would be does this problem present itself because you are flushing the vise a few inches anyway.

My other thought is that I can't see why it would mater much if you moved it in a little, ask Rob Lee. Presumably it loads up, but when responsibly used I'm not sure it would be a problem

Your pics of the circular part come out blackish on my screen and I really am not sure what you want to do. I do recall in one of your pictures the tool tray was floating in a groove above the underside of the top. That would seem to provide an opportunity for the stantion to be mounted on a plate/block under the tray. The stantion could be mounted to a metal plate and the plate attached to either side of the tray. That isn't cheating since there isn't any way to take loads off metal without using metal to do it, it's impossible. Or yuo could do my clean detail. Contact off list if you want any metal work, but it's better to develop local contacts. For the plate all you would need would be a drill press.

I just checked, I did mount my rear screw at 9 inches, but my top is 11.5 inches wide.

Another idea

Paul Kramer


>Dirk,

Roy Underhill showed a bench contruction for "heavy" work. In it he glued and pinned the tenons in each trestle. For the long stretchers he used an interesting wedging method where the tenon has one edge that is inclined like a dovetail. The mortise is also shaped to receive the dovetailed shape of the tenon. Lastly, a wedge fills in the space between the other inclined side of the mortise and the flat side of the tenon. I hope that the rough drawing appears below and you are able to understand the concept.

HTH,

Paul

Re: contact between bench top and trestle

thomd


>Crossgrain comes into play with or without glue. It's less of a problem with round holes or, small dimensions. What makes a good fit, is probably pretty much the same regardless of the overall dimension, so the larger it is the more expansion will take place and one runs into problems with the fit ending up too loose or tight. So for instance across 10 inches, tangential range could be 7-8 % with the kind of woods we are using here. Nearly 18mm of movement. So obviously over a 1" range it will be 1.8mm. In the real world you are only going to get a small component of that, maybe 2-3 mm but if a good fit is .2-.3mm it's still an issue.

I forget, what happened to the sliding dovetails?

I just mentioned floating so you could understand the joint language. You could choose a floating tenon or not depending on how you are building. Generally floating tenons are closer to power tool methods.

paired wedges

Dirk Vogel


>Ok, I see what you mean with floging wedges. That's no problem, I hope.

"I suppose if you found a nice wood that was a little gripy, made sure the back was hollowed and a little rough."

The back of the wedge ? How do you imagine that ? Do you mean the surface where the two wedgs, coming from different sides, meet each other, or just the opposite side ? How could it be hollowed ? I can't find anything about hollowing wedges in my Rogowski reference book ...

Re: Another idea

Dirk Vogel


>Hi Paul ! Sure I understand this kind of tenon and mortise construction, thanks for the picture. Do you see any advantage there, compared to what I planned before ? Is this construction stronger ?

clearances

Dirk Vogel


>Hi Derek ! Thanks for your hint. It has not yet been given, but I foresaw the problem anyway and let little clearances between my cross beam "protusions" and the bench top. In the pictures you can't see them, but they're there. How much space would you give there, by the way ?

Re: Stanchion

Dirk Vogel


>"My other thought is that I can't see why it would mater much if you moved it in a little, ask Rob Lee."

Ok, I'll do that :-)

"Your pics of the circular part come out blackish on my screen and I really am not sure what you want to do."

Ok, right now I've only the time to prepare one of them in brighter colors. I hope it's easier to understand with it. D 1 and D 2 are clearances for the Tucker rods, E is where its mounting plate will be fixed, F is the tool tray, and C the place for our stanchion. Everything's clear now ?

Re: Stanchion

Dirk Vogel


>One more photo from the bench side (the previous one was from the bottom side of the bench) :

Re: Stanchion

Dirk Vogel


>... and a last one fom the top side.

Re: paired wedges

thomd


>Hand plane. start in middle work out. The main thing is that they have good contact, and not just at the mortice.

Re: Stanchion

thomd


>I guess that would work. I like the way it reads back through to the top. I assume that colorations aside this is actually a sidegrain element, and therefore a little fragile. If you did do this, it would be better if the tool tray impinged as little as possible since it sorta cuts your circle in half. You could reduce the penetration at this post to 1/8" or something.

Also it appears that in D2 in this pic http://www.woodcentral.com/cgi-bin/handtools.pl?review=99536, you have created a place for the rear screw, but eliminated the place for the front one?

I'd go for the metal rather than this stuff. As far as the purity of intention is concerned you have to take the loads of some metal at some point and it doesn't mater what point so why not alter your metal to fit your purpose rather than you bench.

A further problem is the end caps appear to have disappeared, and while I like the modern look this thing now has, with the exposed tool tray ends, you have created a cross grain issue where the end caps are located within the rails, you would have to float the middle of each beam's bench top, the yellow bits.

Also, if you don't connect the front and the back elements of your beam system, and you don't have to, you: a) make it more difficult to align them, and; b) you don't share their common weight, so if you put something in the front vise, it won't be held by the leverage of the back beam, particularly since you aren't attaching this stuff to the base.

Re: New questions about the tail vise 7

Ellis Walentine


>Hello und guten Tag, Dirk. I have followed this thread with interest, as you've invested a great deal of effort in your drawings and descriptions. It has taken me a while to grasp the workings of your tail vise design, and it looks like it should work, but it might need a bit more engineering to work really well. (This is so speculative, but you asked for input.)

My specific question is not whether your cap block (T) will hold your guide rail (M) but whether the vise will be properly supported for the length of its travel and whether the jaw will remain parallel to the fixed jaw when you apply a fair amount of torque to the screw. My fear is that there is a natural tendency for the tail vise to push away from the bench when tightened. The bench screw and one rail held by a small cap block is not adequate, in my mind, to keep that from happening. This is why Frank Klausz's bench and other typical European cabinetmaker's benches have a center rail, positioned under the bench top and bolted to the fixed jaw and mortised into the end cap. (in your design, I would mortise this center rail into your cap block (T/Q) and into the underside of the fixed jaw.) The movable jaw is typically notched to ride on this rail, and thereby prevented from moving on any axis as pressure is applied with the bench screw.

If you go with the center guide idea, you don't even need the grooves (R1 and R2) or the guide blocks (K1 and K2).

Ellis Walentine, Host

Re: Another idea

thomd


>As mentioend I have that on two benches it is very solid if you have a connection between the top also. The big advantage to you is that you can have a 3/4" mortice, a 3/4" wedge, and you aren't spliting out the end of the tenon, you would have to blow appart the upright. The disadvantage is that you are depending on a dovetail as compared to the rigid encasement formed by the system not used on Klauzs' bench.

Funny how shimering, planed surfaces, look like tear-out in bad light.

Center rail

Dirk Vogel


>Hi Ellis ! Thank you very much for your analysis of my end vise. What you wrote about directional instability was my feeling from the beginning. Of course I studied the Klausz' solution of this problem. Klaus, however, did several things I wanted to avoid.

Firstly, and that alone is making his end vise more stable than mine, he uses a metal screw. That allows him another kind of construction for the vise part that is aligned to the front section with the dog holes, while I'm rather following the Fortune / Nelson tail vise model.

And secondly, his front jaw is just a bit lower than his rear jaw. That means that his bench top above that jaw can only consist in a thin layer of wood. I wanted a 3" thick bench top even above the tail vise mechanism. That's why "L" is so low. Sure, I could have put another bracket (like the one formed by L, M, and N) at the level of K 1. But then, the bench top would have been too thin above this second bracket.

Furthermore, I would really prefer to avoid metal bolts or screws, even those used in order to put wooden parts together. That is one of the secrets of constructions like Klausz' tail vise (and others) : You can build them only if you admit to put them under a half-finished bench top, screwing several spacers, guide blocks and runners into place in a specific order. My idea was to try and have only a couple of wooden screws, like in the Q/T piece. If this is not possible, I might compromise with metal, but I hope there's still some possibility to manage without it.

What is true, however, is that Klausz gets more stability out of the use of two runners. I'm working on this right now, and I'll post the result as soon as possible. :-)

Re: Another idea

Paul Kramer


>Dirk,

I don't have the experience Thom has. But, it seems that the construction is easier and you don't need as much wood (that is the beefiness of the stretcher) since you're not putting a wedge through the stretcher. Just some thoughts,

Paul

Re: clearances

Derek


>Dirk,

I can not give you numbers, but principals. You should be able to figure this out deterministicaly though.

I would determine the maximum expansion/contraction of the top between the point where the top is secured to the frame and the edge in question. I would add some margin to that and use that number.

Usually, a top is secured to the frame (constrained to not move) in the front side of the frame and any other places it is secured are designed to allow for wood movement. The holes are typically elongated so that the top can slide on the frame at other points. Only one point (front to back that is) would be actually fixed to the frame.

For example, if you are using quarter-sawn European beech, that will have a certain expansion over the temperature and humidity range you expect. I don't know the side of your top or the material expansion/contraction so let me make some wild guesses.

Let's say the top will expand/contract, say 25 mm over 750mm. If your top is 750mm wide, and it will be secured firmly to the frame 150mm from the front edge. This should be your reference point and any other points where the top is secured or constrained in any way should be referenced to the point and movement accounted for.

If an edge is 150mm from that point, then a clearance on the order of (150 * 25)/750 mm would be in order. You might be able to reduce this a bit if you are fabricating it when the wood is not at the minimum moisture content and temperature. That number should be safe though.

You need to look up the expansion/contraction info in a table fo the type and orientation of wood you are using. If you are face gluing flat sawn boards, the wood will be quarter-sawn in the end. That will be much more stable than flat sawn wood but both work.

I hope this helps.

Re: clearances

Dirk Vogel


>Thanks, Derek, for your patient explanations ! I knew in theory how to calculate these wood expansions you're talking about, but I actually never did them, because I can't measure the moisture of the wood I'm working on, so it's difficult for me to forsee in what direction (expansion or shrinkage) my wood's going to move, and how much. Well, the idea of my benchtop was to have a tool tray in the middle, so the wood can work in its direction. I'm going to fix the bench top on its edges, of course, but then, its bigger half is just 15" broad, so maybe the wood movement won't be that pronounced as you expect it to be (25 mm would be an inch !).

Anyway, my guess is that half an inch of distance between the bench top aprons and the trestle supports should be largely enough.