Sliding deadman considerations.

[Jessica Pierce-LaRose]

So, I've got the benchtop flipped over; working the mortises for the bench legs. While I've got it flipped over, I should work on prepping for the sliding deadman's groove. I'm not convinced I really need one for a bench this small, and with the size of pieces I generally work, but I figure it's easier to make the accommodations now rather than try and kludge it in later.

Here's the issue at hand - the outside of my dogholes are 1 1/8" in from the outside of the bench. The dogholes are 3/4" deep. I'd prefer not to have to lift the dogs out of the way just to slide the deadman around.

Do you think I can get away with something along the lines of a 1/2" groove 1/2" in from the face of the bench (approximate, since my plow plane irons aren't really exact anything measurements . . . ) or should I go about making something like the jiggery solutions I've seen that move the deadman groove a few inches in from the face, on the other side of the dogholes:

http://oudluthier.blogspot.com/2009/09/roubo-bench-one-year-later.html
http://carlswoodworking.wordpress.com/2011/06/17/the-sliding-deadman/

I think my tooling would accommodate the former (closer to the edge) easier, even though I'm leaning towards the latter.

Given the scale of the work that I do, while I suspect if I put the deadman on, I'd be using it to support things quite a bit, I don't really plan on putting a whole lot of clamping pressure onto it. At least, the times I've used other benches with that option, I've never found the need to clamp anything to it. But things can change, I suppose.

Comments?

[Jim Ritter]

The bench I built in Jan. is only 5'3" so I feel it is short. I put a sliding deadman on and the groove is only about a 1/2" deep. I did not want to compromise strength at the edge of the bench. I describe it all a couple posts down, I think on page 2 now. My Ash workbench. I use it more than I thought, but it is easily removed if it is not needed.

[Jessica Pierce-LaRose]

Thanks for the input Jim. If I go with it closer to the edge of the bench, I'll definitely be going with a shallower groove, so it's good to know the 1/2" is working for you. I'm still wondering more about the thickness of the groove (or actually - the thickness of the tongue) and the spacing of that from the front of the edge.

I figure the deadman will definitely make it on to the bench at some point, because I can't see any drawbacks to having it, as opposed to not having it; but it's somewhere above "add a shelf" and far below "get the legs mounted to the top" on the list of getting things done on this silly project . . .

[Jim Ritter]

My deadman is 1 1/2" thick and the tongue is half that so 3/4". I wanted it beefy enough so when I clamp to the deadman it won't want to move. I do have to be careful when clamping to the top that the clamp swivel pad does not tip into the slot.

[Mike Holbrook]

There is another option, one I plan to use on my bench. Bob Lang's 21st Century Workbench design uses a stretcher or second rail, 6" from the bench top, dovetailed into the legs, in place of the deadman. I have even more bench edge issues than you do, but even without those issues I believe I would still prefer the 2nd rail to a sliding deadman. The rail can be thick and securely attached to the bench, allowing one to use holdfasts or Veritas Hold-Downs to secure work to the sides of the bench. Even if one does not think there will be any need for the extra pressure holdfasts can apply holdfasts are still faster and have a much greater reach.

[Wilbur Pan]

Given the scale of the work that I do, while I suspect if I put the deadman on, I'd be using it to support things quite a bit, I don't really plan on putting a whole lot of clamping pressure onto it.

That is true with a sliding deadman. You really don't need a lot of clamping pressure for it to do its job.

I'd stick with keeping the groove in front of your dog holes. On my bench, the wall of the groove is 1/2" thick between the front face of the bench top and the groove. My groove happens to be 3/4" wide, but in retrospect I could have made it thinner. On my sliding deadman, which was made from 8/4 cherry, the top tab that fits into the groove is about 5/8" thick. Having used this for a while now, I think that I could have gone with a 1/2" wide groove and a 1/4" thick top tab. As you said, you really don't need that much clamping pressure on the sliding deadman. Given that plenty of M/T joints have been made with 1/4" tenons that have lasted a long time, you should be good with a 1/2" groove and a 1/4" thick tab.

If you are worried about strength, make the groove deeper and the tab higher, even if it means that you have to make the tab more narrow so that you can maneuver the deadman into place.

A sliding deadman doesn't need to be a precision piece of woodworking. There's plenty of slop in mine, which makes it easy to slide back and forth.

[Floyd Mah]

Instead of putting a groove on the underside of the bench, consider a deadman that has two or more pegs at the top that fit into the dog holes from the bottom. The pegs can be offset from the front by just enough to line up the front with the top. You can still fit it in from the bottom, like a window screen, but the pegs will hold it at the top and the bottom rail will keep it lined up at the bottom. The pegs don't even have to be the full width of the dog hole, just big enough to locate the deadman. Your only disadvantage would be that it wouldn't slide, but that's not extremely important to its' function. You could store the dogs in the deadman, then you wouldn't be having a conflict between the two.

A second alternative, if you don't want the deadman to interfere with the bench dogs is to make a slotted top to the deadman and use the bench dogs to stabilize the deadman. You are unlikely to be needing the bench dogs at the same time that you would use the deadman support.

[Jessica Pierce-LaRose]

Those are both pretty neat ideas, Floyd. Neither of them had occurred to me.

[Derek Cohen]

Hi Joshua

I cannot claim to be an expert here, but the method I used has created a smooth sliding deadman with very little "rattle". It is also easy to install and remove.

All I did was to make the triangular runner a separate piece. This is screwed to the top of the stretcher. The deadman and runner are installed together, which means that the groove for the tenon does not need to be deep (to accomodate the extra length if lifting over the triangular piece) or wider-than-necessary (to make it easier to install at an angle).

Some images on this page: http://www.inthewoodshop.com/ShopMadeTools/OhSoclose.html

The placement of the groove does not limit the thickness of the deadman. All that this does is determine where on the deadman the tenon and V-groove need to be positioned. Go as thick as you can since thicker equates to firmer holding.

Regards from Perth

Derek

[Jessica Pierce-LaRose]

A separate triangular runner was in the plans - if for nothing else, than because I forgot to do that part when I was making my stretchers! But I was also taken by the idea of having to deal with a little less "play" in the mechanism by not needing to angle the deadman up and into it's groove. (I suppose Jim's approach of allowing the deadman to enter via the gap in the triangular guide at the far left accomplishes the same thing.

Given that my bench top is 3 5/8" thick, however, I'm not super worried about making a deep slot.

Just thinking that since most of my concerns were more about the tongue breaking off the deadman, given the small dimensions I can squeak into the front space, that I could do a thinner slot in the benchtop, and a matching slot in the deadman, and then attach a bit of plate steel or aluminum to the deadman as the "tongue" . . .

[Jim Matthews]

I used a cutoff length of oak rail from a stair well retrofit.

Turned on it's side, it presents a full round profile, with a raised bead on the "flat".
My deadman has a halfround carved into the front, and an inline skate wheel riding behind on the rail.

It's easy to reposition, and can't be misplaced.

[Salem Ganzhorn]

Joshua,
My sliding deadman has a 3/4" tenon and is set 3/4" back from the front of the bench. I don't think I would want it any closer to the front of the bench because it does weaken the front edge (that being said a weak front edge is probably never going to be a real issue). But I do think a 3/4" tenon is probably overkill and a 1/2" should work.

I will mention however that although I like my Gramercy holdfasts in my bench they don't work great in a deadman. My Veritas bench hold down however works great in the deadman:
228460

It is tough to work out the math for how big/small to make the tenon and still have it possible to insert and remove the dead man. I started with a full 3/4" tenon just slightly less then the height of the mortise and then relieved the back edge of the tenon until I could insert the deadman:
228461

I don't like the idea of having to remove the rail to remove the deadman. That being said in the last year I have never had a need to remove the deadman... except to take a picture for you :).

Relieving the back of the tenon is safe and does not significantly compromise the strength.

Good luck!
Salem

Salem