Advice on sawboard construction

[chopnhack]

As usual, I can make the simplest shop jig into a long drawn out thought process so I apologize in advance...

What do you think is the best material to use for the fence portion of a sawboard? I am looking at a 114" long sawboard for ripping plywood, the extra length is for starting the circular saw off of the plywood and allowing for underside clamping, I might be able to shrink this down to ~106". I am planning on using a t-track on the underside with a sliding toggle clamp and a fixed t-bar at the top to act as a squaring guide and clamping mechanism. There will be a smaller jig made for crosscutting as well.

I am leaning towards solid wood (1x3) only because on the long sawboard I can get a 10' length making a long straight? fence. I am worried about seasonal swelling and twist in the wood. I know the swelling is minimal across the grain, but wood always moves. I don't want to buy angle/channel or anything like that because of cost.

Would it be better to use plywood for the fence? How difficult would it be to align two pieces of plywood to make the full length necessary? Where should the long 8' section of fence go if done in plywood pieces? At the beginning of the cut or at the end? Wherever the piece goes is the error induced minimized by the edge of the shoe riding past it? Is this something best adjusted by handplane?

I have put thought into this, but I am not coming up with the solution, a combination of a migraine and playing outside in the sun too long with two children 4 and under who are tireless and helping me to type at the moment LOL Someone help me out with this rather simple task ;-)

[big tim]

Try this:

http://www.popularmechanics.com/home/reviews/4283497

For a longer one cut it diagonaly out of a sheet.
I like masonite, also known as hardboard, more stable than solid wood or plywood.
Hope the link works
regards

Tim

[LCHIEN]

you need a 114" pieces of something that won't bow. That's a long distance.
Plywood and MDF are generally considered a lot more stable than hardwood.
BUt the ultimate would be some extruded aluminum.

I guess though you might get OK results with plywood or masonite base and about 6" wide MDF strip. Depends on how fussy you are and how straight it needs to be.

My sawboard is an commercial extruded aluminum thing that's in two pieces, bolts together for long rips and use one for crosscutting 4' sheets.
It doesn't have a ledge for the saw to ride on, you have to measure the offset. The ledge is on the reverse side for the clamps.

[cabinetman]

I use either 3/4" or 5/8" substrates for a cutoff jig. Looks like this. It works like a "T" square. I have them short and 10'. The first cut sets the distance to the edge of the blade. After that, just mark for the cut. The far end can be clamped if necessary.

I don't use Masonite, as I prefer a thicker guide for the saw shoe.

.

[chopnhack]

Agreed Loring, being a jig, I do want to keep the cost down and I had thought of box aluminum or even channel as the guide, but thought it may be cost prohibitive. I will have to run some numbers both ways to see if its a possibility.

This is where I am currently at:

top side:


bottom side with 4' t-track shown. Debating the thickness of the top sheet which I am calling the carrier as the under side is really just furring to pack our around the t track and to stiffen the the connection between plywood pieces. The toggle clamp shown will ride in the track on a rectangular piece of wood to aid in squaring? Just realize that I will need to route a channel just behind the t track the distance of the toggles length to be able to make complete use of the 4' t tracks length.



Maybe the top (carrier) will be 23/32" with a slight route down the length where the t-track will go on the underside (1/32" or lighter) with again 23/32" on either side of the t track to pack it out. That shouldn't flex at all, perhaps even a 1/2" top with the same treatment? What do you think?

[leehljp]

If my experience is of any value, I personally would not use a 1X4 board because I can't find any that are straight enough over 8ft. Or as said, they can warp, or at least the ones that I get that I want to stay straight!

If you could get someone to cut you a 4 to 6 in wide piece of 1/2, or 5/8 or 3/4 ply and it be PERFECTLY straight, the would be a good guide. At that point I would use 1/4 ply or even 1/4 masonite as the base.

[chopnhack]

True Hank and I was debating whether to remove all the seats from the minivan and bring home the plywood myself or have the folks at HD use the panel saw... really depends on who is operating the device in my opinion...

The reason I am thinking of doubling up the "base" is because of the recess for the t track. I am betting that it will significantly weaken the plywood. That is why I was thinking of going with a 23/32" top carrier piece with another below, that way I only have to graze the top piece so that the t track will sit flush underneath. Probably only have to shave a 1/32" to 1/64" from the underside of the top piece.

On another note, I maybe able to make this from one sheet if I reduce the size somewhat. I am making it this wide only because I wanted to use one side for the router. Has anyone used their sawboard for routing and would they recommend buying another piece of ply to have this feature? How useful is it in your experience?

[chopnhack]

Just realized that at this thickness there is no way I can use the other edge for a router guide because most bits are about 1.5" long LOL, smacks head

I guess then I will have two dedicated sawboards one 114" and another 66" long with underside adjustable clamping courtesy of embedded t-track all out of 1 sheet of 23/32 with very little waste. The underside clamp will be accessible as I intend to cut my plywood on a table with raised sleepers (like the smart table).

Anyone else have thoughts or ideas, would love to hear them. I am going to look into Loring's aluminum extrusions idea to get an idea on cost and some idea of how to build one out.

[chopnhack]

One more for the road. Loring, I have no clue what this would cost, aluminum wise, but it would be interesting to check it out, thanks for the nudge!

This sawboard would double as a routerboard on the left side. Base made up of 2 lengths of 3/16" hardboard glued together. Guide on top would be 1"x2" aluminum rect. tube with a groove cut out for 4 feet, same on base in that area such that a 1/4" bolt could pass through. The top would still have a t piece across to register one side of the ply to be cut. The bolt would attach to a block below and then be tighten from above allowing a fairly quick adjusting jig. Maybe not as quick as the toggle but not too bad. Wondering if there will be too much play/angle splay to keep the piece restrained - any thoughts would be appreciated. I will call tomorrow to source the tube for pricing. Maybe even smaller like 1/2"x1" or even channel if its cheaper.

[LinuxRandal]

Several of us use the EZ system, but that may be more then your wanting to spend. Sawboards are a good start, and metal supply houses would be a good place to look. However, I think the tool that Loring has, may be:
Johnson 98 in. Aluminum Cutting Level
Model # J4900 Internet # 100188970 Store SKU # 703289

It goes for around $20, and could be permanently attached to your sawboard.


EDIT: My father would use bed rails, as they can be had for cheap or free, fairly regularly as well.
Second edit, for some reason they are under levels (who makes them I am guessing):
Empire 8 ft. x 6 in. Pro's Edge Wide Aluminum Cutting Guide
Model # 900 Internet # 100134266 Store SKU # 714910

[chopnhack]

Thanks LR, I just looked on amazon and 3/5 of the reviews are 2 star and under many citing that the aluminum is quite thin and flexes with the saw pushing against it...

The bedrails are a great idea, but the junkers in our area grab any steel in the wee morning hours. Again great ideas and thanks.

[LCHIEN]

Several of us use the EZ system, but that may be more then your wanting to spend. Sawboards are a good start, and metal supply houses would be a good place to look. However, I think the tool that Loring has, may be:
Johnson 98 in. Aluminum Cutting Level
Model # J4900 Internet # 100188970 Store SKU # 703289

It goes for around $20, and could be permanently attached to your sawboard.


EDIT: My father would use bed rails, as they can be had for cheap or free, fairly regularly as well.
Second edit, for some reason they are under levels (who makes them I am guessing):
Empire 8 ft. x 6 in. Pro's Edge Wide Aluminum Cutting Guide
Model # 900 Internet # 100134266 Store SKU # 714910

I have a Strate-cut II. Quick check on the internet suggests it hasn't been made since the late 70s.
I think that's when they invented plywood .

[mpc]

My sawboard is a simple Masonite foot and a 1x4 guide fence. So far it's held up and hasn't twisted, bent, or otherwise gone non-straight. It's fairly easy to site down the 1x4 prior to use to make sure there are no obvious deflections/problems. Gluing the 1x4 to the Masonite added a lot of stability. It's also pretty strong laterally - I haven't had any issues with it flexing sideways during use. My typical usage scenario is to lay four 2x4s on the garage floor and flop a sheet of plywood onto them... with two 2x4s on either side of the cut line. Then I crawl around on my knees to position the sawboard, clamp it, and make the cut. Lots of reaching and twisting as I go so I'm sure I've shoved on it more than necessary a time or two. Never have noticed an issue yet.

I picked my 1x4 from Home Depot simply by looking at the grain on the ends of the stick, trying to find one as close to quarter-sawn as possible... then I held it against the display rack, one of the round metal ceiling support poles scattered about the building, etc. testing one edge for straightness. I suppose it could be run through a jointer or across a router table set up as a jointer to make sure it really is straight. Then trimming the other side on the table saw makes that side straight too. Or you can buy a 1x6, 1x8, etc. - something wider than necessary - and trim it to roughly 1x4 size using whatever technique you like/use to get a straight line. Doing that you'd be better able to select the grain orientation too.

mpc

edit: snap a chalk line on the Masonite and see how your potential fence 1xWhatever lines up with it. Two nails holding a thin string can give you a pretty good straight line reference to see where your potential fence board has high spots that need hand planing/sanding attention.

[chopnhack]

Excellent suggestion MPC! The chalk line would give a rough guide. And I like the inexpensive 1x idea...

[JimD]

My sawboards are just two layers of luan plywood. The top layer that guides the saw gets the factory edge. I just put some heavy things on the two thin layers until the glue dried. To hold it on the board I a cutting I usually use a spring clamp on each end. Sometimes a C-clamp. Masonite would probably be even better.

I rarely have an issue using an 8 foot guide to cut up 8 foot sheetgoods. You are not completely supported at the ends but still have the guide piece to help align you. To me the concentration required to move smoothly and straght through this part of the cut is no worse than that required to stay in contact with the guide in the middle of the cut.

Jim