Bench dogs lifting work off table? - new roubo build

[Tyler Keniston]

Hi all.

I recently completed (save for the shelf and 'gap stop') a Roubo bench a la Benchcrafted. I am psyched to start putting it to use (have done so a bit already).

Bench resize.jpg
I am happy as heck with the functioning of the vises (I would hope given the $), with one minor issue unrelated to the vise itself (I think). When pinching work between the bench dogs, they ever so slightly lift the work off the table. I'm talking just a glimmer of light, but enough to feel it rock/bottom out when I push down on it.

My guess, and hope, is that is has something to do with my dogs being sized weird or the spring interacting funny or the face being off angle or...
They are square dogs, leather faced, and routed in at a 2 degree.

So has anyone else experienced this 'lifting' and if so, any advice? It seems with the 2 degree angle, that as the dogs go under pressure, they rock back (spring compresses), which in turn also pivots them (rotational force) causing slight lift. This actually makes sense and I would almost expect it, but I can't imagine people put up and are OK with that sort of issue...

Thanks,

Tyler

[glenn bradley]

Angled holes for dogs or angled faces on then are pretty standard in my experience. I use angled faces as I use dogs in all directions.

[mike holden]

Too much clamping pressure will bow the board. This is one reason that planing stops are so popular on older benches.

[Tyler Keniston]

Too much clamping pressure will bow the board. This is one reason that planing stops are so popular on older benches.

That makes sense. In this case, however, i am certain that the dogs are lifting the board and it is not bowing. I know this because I tested it with a really thick short board, and I am also barely applying pressure. As the dog just comes in to touch the work piece I can watch it lift it a smidge as I apply just light pressure (as the dog cocks itself into solid position).

The dogs, I thought, were a pretty tight fit, albeit the design with the little spring makes it inherently so the dog will pivot some as pressure is applied. So I am not really sure how to troubleshoot, or perhaps it is just the nature of the beast?

[Dave Kelley]

If the dogs were slicker then they wouldn't grip the board and take it with it. I would try some dogs without the leather, don't over tighten, and push the board down as you tighten the vice.

[David Carroll]

My old Sjobergs bench with properly angled rectangular dog holes does the same thing. A tap with a mallet or a dead blow hammer on each end by the dog puts it back where it belongs. I'm sure it's physics.. not just a good idea, its the Law!

David Carroll

[Erik Christensen]

I have the same bench - from what I remember of the instructions (it has been a few years) that subtle lift is due to the angle of the dogs under pressure - after you tighten the wagon vise & the stock lifts slightly - tap the board down to seat it against the bench top - that locks everything in place and you are ready to work

nice bench BTW - mine is my favorite tool in my shop - the benchcraft hardware is spendy but it has worked flawlessly for me for years - enjoy

[Tyler Keniston]

Thanks. Took me a loong time to build, (too long perhaps) but I am pumped to work with it.

I guess I could live with the slight lifting and just tap the work down, or perhaps try dogs without the leather facing. There is a part of me though, after all I put into the bench, that wants to make it operate as smoothly as possible. Slick as chubby as some might put it.

Has me wondering If I could design the dog differently (besides perhaps removing the leather, which is maybe the first step i'll try) to correct this. I have to admit that I'm not sure I fully understand the purpose of the 2 degree pitch forward, aside from it perhaps being a sort of 'toe in' feature similar to the leg vise. If the dogs were tight, not sure if this would be completely necessary though? The 2 degree angle is there for good at any rate, but perhaps I could redesign the spring. Make the dog fit snug with little play and find another way to keep it in place such as a recessed spring that allows the dog to fill the entire hole but still have some spring holding action.

[Christopher Charles]

Nice looking bench and workspace! You'll love the bench. The toe in prevents even more lifting compared to dogs at 90 deg. I've not found it to be a (real) issue with mine after a couple of years of use. A quick tap and get going...

[Karl Andersson]

Tyler,
My dogs are made of dogwood (i.e. very hard) rectangular, angled towards each other, and not faced with leather BUT I put the springs on the side, not in line with the clamping force of the vise. They have about 1/16 clearance, so they don't lose their angle when clamping and the work does not rise on the ends, although thin stuff will bow up if I'm too energetic. Maybe try making new dogs with the springs out of the line of compression - or cut the dogs' clamping faces at more of an angle.
Karl

[Prashun Patel]

+1 on angling the faces of the dogs downward. Is there a lot of slop between your holes and the dog posts?

[Tyler Keniston]

good advice Karl.

Prashun I wouldn't say there is a lot of slop, but the way the spring works (so far as I can tell) there will inherently be some play there. I was considering making the spring narrower than the dog and recessing it so there would be no slop, but perhaps Karl's suggestion of putting the spring on the side would be simpler. I might experiment some. Or might just forget about it for awhile...

[Nicholas Lawrence]

It also depends what you are putting on the bench. If the side of the lumber you are putting down is perfectly flat, and the ends are perfectly square, everything should be perfectly flat and stable. But almost nothing I put on my bench starts out perfectly flat. Have you tried it with something that you know is flat and square to see if you still have a problem?

The suggestion to put align the springs the other way also makes sense to me, and if you don't have the problem just with rough lumber, that is probably where I would start.

[Tom Bussey]

Tap the bench dogs down lightly and get on with your life.

[Karl Andersson]

I just found the old bench build thread pictures of my dogwood dogs with side-mounted springs that I've been using for 5 years now without a problem and thought I'd add them to this thread for illustration purposes.

The "shafts" of the dogs are recessed on the spring side and beveled down in the last inch to make the spring angle outwards. The springs are also Dogwood, about 1/16" thick. Unsightly Philips screws hold them on - I probably glued them too, so maybe the screws could come off now.

The opposing faces (where the heads stick out from the shafts) are angled towards each other about 5 degrees. They fit pretty tightly in their holes, with about 1/16" clearance, so the angle doesn't disappear when I tighten them.
hope this helps,
Karl

bench dogs.jpg