Tear out - Leigh 24" Dovetail Super Jig

I'm pretty much in heaven playing with this thing, but I'm getting a fair amount of tear out. I think it might be the cheap practice pine I'm using, but I wonder if anyone has any tips about this issue.
Thanks,
S.
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samson wrote:

Speaking from a D4R perspective, as I haven't seen the Super Jig...
1.) Make sure the work is up tight against the "spacer" board.
2.) Mind the bit rotation direction on initial entry from the front. A light climb cut will leave an clean cut.
3.) Slow down at the edges.
There's a special section in the manual that has diagrams showing proper motion. I always need to refresh myself when I set up the D4R.
Other than that, it's the pine. <G>
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If the manual is only half as good as what mine is for the D4, reread the manual where it tells you how to make the cut. Pay particular attention to the direction of cut at the entry and exit of the board. Be sure to use a backer board on the back side and climb cut at the initial entry/front side of the cut.
Think about the direction that the bit is spinning and where the tear out is likely to be.
On the entry front side of the cut you should work the router right to left in shallow even passes until the bit has clearly entered the board all the way across that particular cut. On the exit side of the cut and again with a backer board on the back side of the cut let the bit exit on your left side and work towards your right side after exiting the back side. Once the backer board has been cut the full width this will be easier to do.
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snipped-for-privacy@swbell.net says...

Leon and Barry,
Thanks for the info. That helps.
S.
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Put a sacrificial backer board into the top clamp, in place of your spacer board, and position it up against the back side of your part. This will significantly reduce tear-out from the back side. You can leave the same sacrificial board in place while doing all of your duplicate parts. The best way to reduce tear-out from the face side is to use the climb cutting technique, but another way to reduce front side tear-out is to clamp a thin (1/4 or 1/2" ) piece of sacrificial material across the face side of your work using small C clamps to hold it in place (Be sure to position the C clamps so that they do not interfere with the router bit movement). In the end, there's always a small risk of some tear-out no matter what you do.
Climb cutting and slow movement of the router while entering or exiting the cut is usually all that is necessary, but this takes a bit of practice to get the best results. Using pine to practice is a good idea, but you should try using some oak, poplar, or other hardwood scraps for practice too, as each wood will behave a bit differently. I frequently use a sacrificial backer board, but I've only had to resort to using a sacrificial front board one time so far, while cutting a particularly difficult piece containing significant swirling grain.
Charley

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snipped-for-privacy@carolina.rr.com says...

Thanks, Charley. I'll try using some better wood and, when the projects become critical, I'll try clamping a board to the front.
S.
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In addition to what everyone else has said, I put a straight cutter in the router and hog out most of the waste wood with a free-hand cut. Or mark the piece with a pencil and free-hand out the waste on the bandsaw before I clamp it up. Then when I do the final passes the router has a much easier time of it.
Tom Dacon

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