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Here is my scarfing jig that I made today and can't say I am 100% happy with it cutting 1/4 ply. I am hoping when I cut the 3/8 stuff it will work much better. My first mistake was not flopping the panel when I done both ends, duh...so had to hack off about 3" of it and redo the cut correctly. I am hoping with the thicken epoxy it will go together and look half decent when it is nailed down.


If anyone has comments please throw them in and maybe I can get a cleaner neater cut.
Jimmy

Jimmy; As I'm close to starting ply, I'm very interested in the method. Could you please explain how the jig is used. Maybe a photo of the scarf being done?
Doug

I'll let Jimmy confirm but it looks like:

1) clamp the plywood on top, with the to-be-scarfed edge against the front.

2) use a circular saw on its side, with the base against the laminated face. (that face has been shaped so that the saw blade gives the scarf angle)

3) I am not sure how you "fence" the circular saw so that it cuts straight. Maybe Jimmy's saw has an edge guide that he runs across the bottom of that face.

(Nice and simple design, Jimmy... I will steal those ideas next time I need to scarf)

I copied this off of the one that was posted here on the forum.
I made this one out of good straight 2x8's and made the length 5' with a 7 degree angle on the bottom piece and with a bunch of good wood screws to hold it together. I have a couple of metal fold up saw horses so used one of those to be able to fold it up and take it out of the weather when done. If you notice there is a slat to guide the saw base along...I determined that distance by openting the saw to the deepest cut and placing the blade up against the top and marking the lower part of the saws base plate. You want to make sure it is thin enough so that it does not set against the motor housing of the saw or it will throw things off. I ran my slat thru a planer until it just barely cleared the saw motor. My first attempt in using it gave me bad results because I did not have enough clearance and it was pushing the blade to low. Anyway I think you will get a good picture off of this photo that was put on the site here.
To hold the panels down flat I found that using some wood screws are much better specially with the 1/4" material. The holes can always be filled in with expoxy.
Jimmy

Jimmy & Porter

Thanks! That is a clean straight forward answer. I have scratched my head raw for a consistent way to do this on full sheets or boards.

Thanks,
Bill

What kind of blade would work best for this?

ya that looks like the cats a**....ummm well you know what I mean. ..lol. I suspect it will now take all of about 10 seconds to scarf a sheet of ply. Awesome. Like Warren asked, what kind of blade works best? Panel blade, other?

So far as blades go I just used a carbide standard blade and a new one so the cut is very clean. Don't rush the saw either just let it cut a good clean slab off. My luck with plywood cutting blades of carbon steel they get burnt up pretty quick as they do not disapate heat fast enough and those are big cuts to slab off. Maybe a fine tooth carbide blade would make a finer cut but haven't tried that so no comments on that issue. For the price of the blades it would be worth purchasing one and give it a go as you can always use it on something else.

Just to let you know I tried Porters method of using a big clamped down board but found the 1/4 play still wiggled up and down to much so never even tried it on the 3/8 ply as I just screwed it down till it was good and tight with wood screws. I would say the accuracy of the cuts are within 98% good to match up. I will have some final touch ups to do but they are glued together and screwed and nailed so I am not worrying about them failing and also I made backups in the frame pieces were they matched up. You can see this in one of the panel pieces in the photo of my tunnel hull report in the power boat section. After fitting those between the frame pieces I then backed those up with some 3/8 ply well glued and screwed together.

Just to let you know. I built one out of 3/4 pine and could not get it lay good and flat in any direction so that is one reason I went with the 2x8 material.

Wish you the best of luck and if you have questions just throw them out and we will work it out.
Jimmy

Thanks Jimmy. All very clear now...will give it a try. I have a 42" by 8 foot workbench so I'll build right on the end of it. Should work great.
Doug

That should work out good with that size work bench. Just make sure to make the piece that fits on it at close to 5' so you will have working room with the saw to run the full length okay.
Jimmy

I picture is worth a thousand words...thanks Jimmy!

i like it ,but whats the cut 3 in. whats norm for scarf cut im talking like tarzan mike

Scarfs are usually 8:1. So, a 3/8 thick ply would have a 3" cut. The saw is seeing a 3"+ piece of wood. So, go slow.

Bill

thanks

I read in the Glen-L building blog that scarfs should be 12/1. So would an 8/1 be OK for side planking in a Zip with 1/4 plywood? That would yield a 2" joint instead of 3". This would make scarfing a little easier, but I don't want to sacrifice strength.

Roberta