Why isn't my bench stable? advice needed

[Matthew N. Masail]

So I decided to make a new base from my benchtop, this base would allow me to place vises where I want them.

The previous base was rock stable, not a hint of movement, it had legs at the far corners of the bench. the new is base pictured here:
unnamed.jpg

the base is only 40" long, and the bottom bars about 23", which is the same as the benchtop. My issue is that the bench is highly unstable, it rattles, and the far right corner bounces when I use the face vise.

-The legs are flat and all for edges are co-planer.

I found that I would need about 30kg of mass on each side on the legs to keep the bench stable, and while that is kinda doable, I use thinking maybe there is a better solution.

also I'd like to know, did I make this with bad mechanics, or is it just not long enough at 40" to counter balance the cantilever effect from the top hanging over the edges?

I'm open to all Ideas besides building a new base.... I have no wood, or time for that anymore.

[Brian Holcombe]

All the weight is in the top. I'd make the floor stretchers much heavier.

[Matthew N. Masail]

Thanks Brian. I'm not sure how much heavier can they get? I needed 30kg of steel to keep the bench stable... or is stiffness in play here too?

how is what I did different to this? http://www.google.co.il/imgres?imgur...d=0CD0QMygUMBQ

[Chris Hachet]

I would push the legs back out to the corners, actually. The face vise could work inside the left front leg rather than outside of it. My MINI Cooper S is a great handling car, the wheels are pushed by the designer to the far outside corners. My bench is about the same size as yours, but the legs are near the edges of the bench...stable as a rock...like yours was....

And here is one area where I agree with Chris Schwartz. The legs really should be even with the front and back faces for clamping options. Much easier to work that way.

I know you said you had no time to fix this....in the mean time, add a shelf on the bottom and dump some sand bags on it perhaps.

Just my two cents.

Chris

[Chris Hachet]

Thanks Brian. I'm not sure how much heavier can they get? I needed 30kg of steel to keep the bench stable... or is stiffness in play here too?

how is what I did different to this? http://www.google.co.il/imgres?imgur...d=0CD0QMygUMBQ

I think its mostly physics rather than stiffness.

[Matthew N. Masail]

I would push the legs back out to the corners, actually. The face vise could work inside the left front leg rather than outside of it. My MINI Cooper S is a great handling car, the wheels are pushed by the designer to the far outside corners. My bench is about the same size as yours, but the legs are near the edges of the bench...stable as a rock...like yours was....

And here is one area where I agree with Chris Schwartz. The legs really should be even with the front and back faces for clamping options. Much easier to work that way.

I know you said you had no time to fix this....in the mean time, add a shelf on the bottom and dump some sand bags on it perhaps.

Just my two cents.

Chris

I think I will try tomorrow to push the base to the far right (as far as the side vise will let me) and maybe extend to base to have 2 extra legs on the left.... I'll end up with a 6 leg base ! lol, but I really prefer the face vise on the far end, because I found that any bench space to the left of it was pretty much wasted for me and my bench felt even smaller yet.

[Brian Holcombe]

I'd make them wide as well, that will help. If it's annoying off the front then I would make them wider toward the back to widen the footprint. That, in addition to making them from heavy stock should improve the stability.

You can beef up the stretchers too. I wouldnt be surprised if the stretchers on my bench weighed 2/3 as much as the top, they are 8/4 by 9" by 40"~, combine that with the heft of the feet and legs and the base is heavier than the top, lowering the center of gravity.

[Thomas Schneider]

Thanks Brian. I'm not sure how much heavier can they get? I needed 30kg of steel to keep the bench stable... or is stiffness in play here too?

how is what I did different to this? http://www.google.co.il/imgres?imgur...d=0CD0QMygUMBQ

The bench in the link you provided has toenail feet. On your bench the foot is a flat board. Not sure if that's part of your problem or not but worth a second look.

Tom.

[Maurice Ungaro]

Wider is better, as far as the base is concerned. Short of going BACK to what you had, you could take a tip from the lathe crowd: run a shelf between your two stretchers and add weight to the shelf. My first, and soon to be secondary bench kinda looks like yours, and it's tippy when planing across. I don't know why people enjoy an overhang of their benchtops.

[Tom Vanzant]

Before you reconfigure the base, try shimming under the leg that "bounces". It sounds like your bench feet do not meet the floor evenly. 4"x4"X1/8" pads under the ends of the feet will help bridge floor uneven-ness, but try the shim first.

[Prashun Patel]

I vote to check that your floor is flat first. Shim as necessary to sit flat.

Next I am troubled by your base. How are the legs attached to that base. Without a deep tenon into a base you may need a lower rail on each side of the base. You can half lap it now that it's built.

Last do you have an upper stretcher?

Reading it again if you are having rattle and bounce issues it points to an unlevel floor. Even a small bench can handle reasonable forces on a cantilevered vise.

[Charles Bjorgen]

My bench setup is similar to yours. I'd recommend installing pads under the four corners of the feet. I used pieces of 2x4 for that purpose. You can also make a shelf to span the stretchers for tool storage. Instant weight.

[Dan Clark]

The bench in the link you provided has toenail feet. On your bench the foot is a flat board. Not sure if that's part of your problem or not but worth a second look.

Tom.

I agree about the flat board. From what I can see, it looks like there is limited support for front to rear racking forces. As a test, the OP might want to consider vertically lag-screwing an 8/4 X 8" wide board on the outside edges of the legs to connect the bottom of the front and rear legs. It won't look pretty and it's probably not permanent, but it's a quick and dirty way to see if that is the cause of bench instability.

Regards,

Dan.

[Jim Matthews]

Prashun beat me to it.

Have you put a level on the bench?
I've got a more broadly cantilevered bench,
yet it's stable. The addition of a shelf
spanning the bottom stretchers will reduce
horizontal twist, but won't appreciably
reduce flex in the uprights.

Simple enough to build a shelf and put your planes on it for mass loading.

[Winton Applegate]

Here are some general observations about woodworking benches and how they compare to other general purpose work benches such as chest of drawer type benches and welding tables :

Many general purpose work benches are often "built in" to a wall; anchored to the floor and to the studs in the wall.

Woodworking benches in general lack angular cross bracing. Adding built in cabinets with drawers like the Shaker benches or Phillip Lowe’s bench tends to do the same thing as angle bracing.

Woodworkers avoid bolting the feet / legs to the floor because they don’t see anyone else do that. The pros don’t because they need to move the bench for various big projects but they tend to have full size benches that are massive enough to be free standing and stable. The home shop dude, or dudett consciously or unconsciously emulates this but tends to have a smaller / lighter / cheeper bench which should probably be bolted to the floor or a wall to stabilize it.

so the bench, if small may have a tendency to wiggle, teeter, slide across the floor or tip.

Weight is nice but without bracing you just get an immovable thing that wiggles.
Shimming the feet is a good diagnostic but at least one or two feet that adjust, like a washing machine or refrigerator base is the way to deal with an uneven floor or out of level bench.

Of course every body wants a woodworking bench they can move around.
Me . . . I want a bench that does not wiggle or slide across the floor or tip when I really get to cross grain scrub planing. So I am not above anchoring a bench to the floor or to a wall or running arms over to a wall or two.

For metal working it is kind of the same thing but I can not tolerate any wiggling at all when I am hacksawing. ( a small metal table can get to oscillating).
Running a brace to the wall and anchoring it has been the best solution.