New scarfing jig * Version 3.0

Jeff Horton

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After ripping up my thumb with that nasty kickback I finally got to the shop today. I still had one my cut to make using the jig that bit me. I was very reluctant but I had to make more cut so that that parts would mate up.

Once it was done I felt a little vindication and a lot of relief!

Then I moved on to a new jig. I had decided I was going to just cut out the knots in the middle of these long pieces on the RAS. Then I would just build a jig to sit on the RAS table and cut the actual scarf. After a lot of looking and trying stuff I came back to the fact the table saw is the best tool for this operation. One cut and your done. No new setups. No double cuts. No fuss no muss.

I gave in and built a new jig that I think is better than the sled. No chance of pulling a part back into the blade. The off cut just falls on the table where I can see it. The left handedness of this jig put me out of the line of fire. And I added some walnut handles I had laying around I never used and these keep my hands well away from the blade of the 'line of fire'.

Made a couple of cuts and I like it, don't trust it yet but it seems to work OK.


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Still looking for better clamping method but being so close to the blade it's hard to clamp the parts.
 
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A couple observations; first I would clamp that rig to the RAS table so I didn't have to move the material past the blade. This is a great job for a RAS. Second, assuming I don't know something (very likely) and that you have a perfectly good reason for not using the RAS; I would cut the scarf on a wider board and then rip the strips from it. Idea number two may also have issues based on something I am not aware of ;-)
 
What kind of RAS do you have? I don't understand why you'd need to make a jig or a double cut with the RAS.

I've made the same cut to the one you illustrate on my RAS on 2 by 4's for the roof trusses for Ned's shop.
 
The reason for the scarfs is because of the garbage lumber we get around here. What I am doing (most times) is cutting out of the middle of a strip of wood that might be 10 to 16 feet long. So I may be cutting 4-5 foot from the end. I cut out the knots and glue it back together. It the only consistent way to get good clear stock.

With my RAS against the wall it can't reach but MAYBE 2 foot from the end? I agree is it the perfect tool and if I were just cutting the ends off like in the photo. But this was just a scrap piece to test the jig.

If I start making a lot of kits, I will probably buy a cheap craftsman RAS and dedicate it cutting scarfs. Put it on wheels where I can roll it out in the middle. But that is probably quite a ways off before I can justify that.
 
With the RAS against the wall, yeah, it would be hard to cut in the middle of a 10' long board :D

One quick observation, to avoid any more kickbacks, or actually ejections of the cut off pieces, you should make a corresponding platform on the off cut side of the blade, so the pieces don't drop, or fall off when you cut them, the off cut platform does not have to move, just sit there to catch the off cut pieces. :dunno:

Just a thought :wave:
 
Hi Jeff.

I'm no jig expert at all but I think that if you placed the piece to be cut on the other side of the jig, you could place the first spring clamp closer to the end.

At the same time as the piece to be cut would have the support of the jig the strain on the clamps would be much less, and the piece less likely to move.

I don't know if I have explained myself well, I hope it makes sense or so I think:dunno:
 
Toni, if I understand your idea, I don't think he'd have more room for the clamps he's using now, but by moving the workpiece to the other side of the jig as you suggested, it opens up another possibility for clamping:

Scarf%20Cut%20Jig.jpg


I agree with Stu's suggestion to have the cutoff "fall" on a platform the same height as the sled. Using this clamping idea, you could extend the sled to the other side of the blade, as long as you stop the cut before going all the way through the sled:

Scarf%20Cut%20Jig%201.jpg
 
Here we go...dressed up a bit more:

Scarf%20Cut%20Jig%202.jpg

Vaughn (and Jeff),
Wasn't the 'toss back' caused when the original sled was pulled back, and the cut-off caught the back edge of the blade?

If that was the case, then your sled wouldn't solve the problem - maybe make it less likely, mainly due to operator positioning, but the potential would still exist.

Stu's suggestion (and one I use as well with my 'Norm-style' cutoff sled) would be better. The cutoff would just sit on the fixed platform, and would be pushed out of the way by the next cut.
 
I have a three piece table on my RAS (underneath the melamine top is a three piece mdf table). Here is the setup I would use for this cut. The bit of plywood is where the fence would be and the 2 by 4's are the board to be cut. The miter angle is set to 80 degrees.

80degree01.JPG

80degree02.JPG

Unless your RAS is in a corner, this shouldn't be a problem. The saw would need to be lowered into the table at the extreme forward position and then backed into the fence to make the kerf cut.

When I made similar cuts for Ned's roof trusses, I had a 12" blade on my saw and didn't think to change it. I needed to clamp his 2 by 4's to the fence with he saw raised above the table a bit, tighten the saw - carriage stop and lower the blade into the work piece. Then I'd hold the saw with one hand and release the carriage stop with the other and make the cut.

With your 3/4" material and/or a smaller blade (maybe even a 7 1/4" blade if needed) I don't think I would have had to do this.

It seemed like you were thinking of putting your board perpendicular to the traditional RAS usage and then make a 10 degree miter. I posted these pics because it seemed that we weren't on the same page.

Hope this helps! :wave:
 
i don`t like the spring clamp in close proximity to the blade......."stuff" happens and a 250mph spring clamp has the potential to cause a lot of damage.
 
Toni, if I did it like your suggesting the clamps actually ended up futher from the blade. That is why it is the way it is now.

Vaughn, love the idea for the clamps. Spring clamps are just till I came up with something better. That it worth looking into, just need a spring loaded end of them of some kind of quick thickness adjustment.

I DO NOT want the sled. I think that it what got me hit. I didn't see what happened but I suspect when the part fell, it fell on the sled and then vibrated over in line with the blade. When I pulled it back it picked it up and got my thumb. Again I don't know but I don't want to chance that again.

Mark, your forgetting you have a turret saw and most of don't. That is the one RAS that might replace my DeWalt. I can't turn mine to 10 degrees and get the blade past the fence.

tn_after4.jpg
 
Jeff, could you put on an auxiliary table that mounts the fence more forward? Or are you saying the saw isn't physically able to be moved past 60 degrees or so in the miter travel? I'm only experienced with my turret saw and don't know.
 
Here we go...dressed up a bit more:

Scarf%20Cut%20Jig%202.jpg

That is about the same as I was thinking, but I would add one more piece. Depending on the angle (thus the length of the cut) and how wide the part is, the cut end may flex as it is being cut.

The additonal piece I mentioned would be between the part to be cut and the row of clamps. This way it could be made wide enough to be stiff and extend out as far as the end of the work piece. This would give it support all through the cut and would not allow it to flex.
 
Jeff, could you put on an auxiliary table that mounts the fence more forward? Or are you saying the saw isn't physically able to be moved past 60 degrees or so in the miter travel? I'm only experienced with my turret saw and don't know.



Past 45-50 degrees your cutting on the end of the table and fence. Past that it's going to require modifying the table to move the fence way back.

Don't let someone talk you out of that saw! When it come to RAS they are contortionists!
 
You could also make a splitter specifically for the blade height you use with this sled jig. If the splitter follows the curve of the back of the blade about 1/8" away, that significantly lessens the chances of picking up the offcuts and throwing them.

Better than spring clamps for holding stock to the fence as it's now set up might be something like the Rockler universal fence clamps, number 31373. You would simply drill two holes in a block of wood; the clamps fit into the holes and reach over the fence to clamp stock between fence and the block.
 
Further revisions

Here are some photos of the on-going development of the scarf jig. I added some clamps. These are some Jorgensons I had laying around and while not perfect they do work pretty well. Had to add spacers to keep them from falling down everything I swung them to the side.

overal.jpg


overal2.jpg


So far it has worked really well. There is a balance issue with the long boards but that is to be expected. I am often cutting out a knot in the center of a long board.

long_parts.jpg


As I said it has worked pretty good so far. Obviously I am more careful but standing on the left side of the blade 'appears' to make this much safer. Kickback is always going to be a possibility but I think the chances are much less since this is no longer a sled.

I had this happen on one cut I though seriously about hitting the deck for a second there. Of course it was to late but scared me good.


wedged.jpg
 
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