Roubo Benchtop Question

[Chris Norman]

I'm getting ready to start on my Roubo Bench.

I was thinking most of the bench (including most of the top) would be Borg Douglas Fir (from 2x12's) since SYP is not available in Northern Colorado.

I'm going to be using a benchcrafted wagon vise so will need a thick endcap on the tailvise end of the bench. I was thinking of using 3" of Ash for the endcap as well as a strip of 8/4 ash for the front lamination for the benchtop dovetailing them together like what Jameel (benchrafted) did on his benches.

I was also thinking of using a strip of 8/4 Ash for the Bench dog lamination.

I just got to thinking: Is this a bad idea to laminate Ash to Douglas Fir in the bench top? I'm concerned about differing wood movement between the two species causing problems.

What does everyone else think? Obviously I would love to build the entire top out of ash, but I don't currently have the funds for that.

[John Schreiber]

I looked at the Shrinkulator (http://www.woodbin.com/calcs/shrinkulator.htm) web page for a couple of different kinds of fir and ash and they seem pretty close. I think it would be ok. It might be a good idea to put ash edging on both the front and back to keep things parallel.

Good luck on the bench. It's a big project, but a satisfying one.

[David Keller NC]

"I just got to thinking: Is this a bad idea to laminate Ash to Douglas Fir in the bench top? I'm concerned about differing wood movement between the two species causing problems."

Why bother with the ash at all (unless you're already got it). The only place I'd use it would be a vise chop. Douglas fir is really strong - there's good reason why it's a structural timber.

No question that it's softer than ash, maple, or oak, but so what? No bench that actually sees use looks good after a year or so, and even hard maple will dent significantly in use. I finished my latest bench last fall, and it's made entirely of (hard) maple. Nevertheless, it still has accumulated lots of dents and nicks in the top, which'll get erased the next time its flattened.

But, I have to ask - if you're willing to pay $350 for a vise, why not an extra $200 for the wood you want?

[Chris Norman]

John: Thanks for the info on the Shrinkulator tool, good stuff!

Dave:
Why bother with the ash at all (unless you're already got it). The only place I'd use it would be a vise chop. Douglas fir is really strong - there's good reason why it's a structural timber.

That's good input, I do already have the ash, but have not yet purchased the Fir.

But, I have to ask - if you're willing to pay $350 for a vise, why not an extra $200 for the wood you want?

That's a great question! I But now that you mention it, it does seem silly to spend heavy on a really nice vise, only to skimp a bit on the top.

I probably will build the base out of fir no matter what, since I don't really care about the hardness of the base, but I'll have to see if I can find more 8/4 ash for the top; my hardwood supplier was a little scarce on ash last time I looked.

[David Gendron]

I don,t think that going with DF is skimping on the top! My entire bench is made out of used DF and it is realy good! Other that my leg vise that is made of Red Oak. the only thing I noticed, is my round dog hole, they have change shape a little because of using a lot of hold fast... But not enough to bother with it!!

[Jim Koepke]

I would go with the ash for the strip with the dog holes. The holes will likely distort less then the Doug Fir.

As far as movement goes, it is usually across grain, so the only place to worry is at the end caps. As long as those are attached so the top can move a lilttle you should be OK.

jtk

[David Keller NC]

"I probably will build the base out of fir no matter what, since I don't really care about the hardness of the base, but I'll have to see if I can find more 8/4 ash for the top; my hardwood supplier was a little scarce on ash last time I looked."

If it was me, and I wanted to use a combination of woods for the bench, I'd probably use the ash for the legs and stretchers, because it's strong and it's highly unlikely that the shoulders of the tenons would distort under load and become loose.

I'd use the doug fir for the top, and because it's inexpensive, I'd make the top 4" thick. That will give the bench a great deal of mass, and will solve the problem of the dog holes distorting after a period of use. Because a holdfast primarily bears against the top 1/4" to 1/8" of the top of the hole, surfacing the bench will remove most if not all of any distortion (and with a 4" top, there's no way they're going to distor enough to be unworkable anyway).

Jim's suggestion is also a good possibility, though I'm thinking that using an extra hard wood for a dog strip and then a softer wood for the rest of the bench top might make flattening it a problem - the extra hard wood will want to "catch" a plane traveling across the bench.

[Chris Norman]

I think I'm going to go with a completly ash top (it will be 4" thick) I talked with my SWMBO and she is ok with the extra cost (Am I lucky or what!)

The base is very similar to Chris Schwarz design with 5in square legs and 2.5 in wide stretchers so I'm not too worried about the weight of the base, I think Douglas Fir should be heavy enough.

I did pick up some of the TFWW holdfasts during the sale, man I love those things. They even work well in my current bench (solid core dore on a set of shop boxes)

[John Sanford]

Whether you go with DF or not, there's one thing to keep in mind when using DF.

Avoid face grain in any horizontal surfaces, which includes a bench top. Face grain will have large swaths of wildly varying density and hardness due to the hardness differential of the earlywood and latewood. Keeping a DF face grain top flat will be a fair bit more work than other woods.

Simply orienting the wood to insure that the benchtop face is quartersawn will put the earlywood/latewood rings in very, very close proximity.

[Graham Hughes (CA)]

On mine I laminated beech to Douglas fir for the front vise, and the lamination hasn't caused me any particular issues. You should be fine, as long as everything involved is nice & dry.

For what it's worth, on my tail vise I have a beech jaw that presses into DF end grain and that works fine. I was a little concerned it would be too easy to dent, but the end grain holds up better than the face stuff.