Questions on the Roubo frame saw

[Mark Gibney]

I'm thinking of making a Roubo type frame saw to resaw beams.

The beams I need to resaw are about 14" wide, so I plan on running both edges over my tablesaw then using a frame saw to finish the rip.
My bandsaw does not have enough resaw capacity to do this, or I would use it. I'm not going the neanderthal way out of romanticism! But I'm actually looking forward to using doing this.

I came across the Blackburn Tools site, and they can sell me a blade and hardware in various sizes, plus plans to build the saw.

They have blades in lengths of 32", 36" and 48".

The beams are Doug fir.
What length blade would be most suitable for resawing a 14" wide beam?
Is the Blackburn Tools kits a good one?
Any other advice you might have on this is very welcome.

Thanks, Mark

[Scott Winners]

Is your total depth of cut 14 inches?

I haven't fooled with wet/ green Doug Fir much but a stick 14 inches by much of anything is going to be a handfull even dried down to 20% MC. More than three or four feet long I would skip the table saw.

Can you post a picture of the mill's stamp on one of your pieces and provide the other dimensions?

[Mark Gibney]

Scott, the boards are 3 1/2 x 14 x 48. The wood is dry. I'm aiming to end up with three boards about 1" thick.

[Scott Winners]

So 16/4 Doug Fir, 14 inches wide, 48 inches long.

My experience with Doug Fir is getting something fat like that dry all the way through takes years and years. And years. More than three or four years. If it has a pencil mark on one face or edge with something like "June 2002", OK, that one is dry and you can resaw it with little risk of wood movement.

If it is fresh from a mill with a KD mark near the D-Fir inside the triangle, the center of the plank is probably somewhere between 19.99 and 19.9 % MC, with a lot of moving left to do. Any surface checking or splits? End checks or splits?

My concern is ongoing wood movement. Given four foot length your plan for table saw to kerf both edges with a table saw and then finish with a rip saw is sound. I am not familiar with the Blackburn frame saws, though I have read positive comments here. In your situation I would reach for my 'big' ripsaw with 5 points or teeth per inch, and let the table saw kerfs work as guides for my handsaw.

I encourage you to start wth a cut one half inch deep, then go to one inch deep and recognize if the blade starts deflecting from square as you go deeper you are getting into moister wood than is at the surface. If you smell turpentine, you are cutting DF wetter than 20% MC.

Getting Doug Fir lumber down to 20% MC with no defects is fairly straight forward, all the left coast kiln operators have to do it if they want to stay open. Getting DF down to 10%MC with no defects is a bigger problem. I don't know Los Angeles pricing, but up here that 16/4 x 14 x 48 in DF as grade 1 or 2 KD to 20% MC would be $30-50 with high risk of cupping after resawing. To get that same plank in SS (select structural) with grain suitable for the Library of Congress and KD to 10% MC that I could resaw with abandon would be about $300.

If the grain in your plank is perfectly flat, either quarter or flat sawn +/- 5 degrees, nope never mind, if it isn't dry all the way through you are asking for trouble. If there is visible curve in the endgrain and you paid less than $250 Alaskan for your plank I suspect it will move on you when you resaw. If the curve in the endgrain is less than 5 degrees of bend but you got it for about $100 Alaskan or less, it is probably going to move on you if you resaw before 01-01-2030.

No offense. If you rip that thing in half on the center of the curve of the grain and resaw +/- 7" wide planks will it destroy your project? SS straight grained DF is beautiful stuff, but you got to pay to play. DF pith is going to bite you if you leave it in. I have learned to use FOHC (Free Of Heart Center cut) DF because there is no pith in it and quarter/flat sawn is so hard to find up here. FOHC is fairly easy to identify, no pith (free of heart) but cut near the center of the tree, so there is no face grain. All four faces of the plank are all edge grain with no visible face grain on any surface.

Good luck and best wishes.

[chris carter]

I have the 48” one. I see little point in pre-cutting on the table saw unless you want to make things take longer than they should. The 48” saw cuts VERY fast. It’ll tear through DF faster than a hungry cheetah. How tall/heavy are you? If you are 5’8” 135lbs than the 48” saw would be too much. You need arms long enough for the throw and enough body mass so the saw doesn’t push you around (and a bench heavy enough so the saw doesn’t push it around). But generally, get the biggest saw you can handle when it comes to resawing. The quality is excellent and a very good value for the money.

A link to a thread with some of my observations after building the saw: https://sawmillcreek.org/showthread.php?290097-What-I-learned-about-Roubo-frame-saws

[Mark Gibney]

Thanks Chris, I think I'll get the 48" saw kit. Looking forward to it!

Scott, the MC of the lumber is not an issue but I appreciate your insights. It's an old piece I've had hanging around for years and it's about as dry as the Dead Sea scrolls at this point.