Pattern routing problem


I'm building an English garden bench out of redwood. To cut the curved pieces (legs and arms) I do the following:
1. created clean templates of curved pieces out of 1/4" tempered hardboard, 2. traced the pattern outline on the piece, 3. rough cut to within 1/8" of the outline using a jigsaw (do not own a BS) 4. attach template using double face tape to top of rough cut piece. 5. Use 2" flush trim bit (top pilot) on router table to trim to pattern.
The problem I am having is that when I do the flush trimming, it trims 95% of the time OK but occasionally, I get chipout and chunks are taken out of the piece along the edge I am routing flush to the template.
The lumber is kiln dried clear all heart (CAH) redwood that is dimensioned lumber (1 1/2" thick). It is beautiful wood (but expensive), very soft, and seems very dry and splinters easily.
I take the trimming operation very slowly but still get the problem. The bit is a 1/2" shank, dual flute, 2" flush trim bit Rockler house brand. I've even tried climb cutting but the operation is very difficult.
Either it is my technique or just a result of this wood species. Maybe kiln dried redwood heartwood is just too frail for this type of operation. The plans called for using a bandsaw to cut to shape -- using the pattern and flush trim bit is my idea.
Any suggestions?
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Jerry, is there anything about the design that necessitates pattern-routed precision? Could you just cut to the line, sand the edges smooth, and call it done? Sounds like the routing is more trouble that it's worth.
You could also use the RoboSander - a bearing guided sanding drum. Woodcraft sells them.
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That is one of the problems with curved pieces. One one side of the curve the cutter is cutting into the grain. On the back side of the curve it's opposite. Several ways to do it. Look at the grain, when you get to an area where the cutter will lift the grain. Hold the work firm and take small cuts like your nibbling away the wood. Once the bulk is gone then make one final pass. You could also do a climb cut but it's not recommended. The best way is to look at the grain. Then mark your template where the cutter will lift the grain. Use a flush trim bit on all the curves with the cutter cutting into the grain. With them done chuck up a pattern bit with the barring on the bottom flip the work and finish the cuts. With the work flipped and a pattern bit the cutters will be cutting into the grain.
. Jerry wrote:

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I am not the original poster, but I thank you for the link. That is a fantastic idea.
Frank

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Even better is to use a shaper. Reverse the motor and the cutter.
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Toller wrote:

I am not a shaper user and am curious why this is better. This bit I linked, own and use a lot couldn't be simpler to use just raise and lower with my router lift.
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Jerry wrote:

I do a lot of pattern routing, but not with the setup you describe. I've never had much luck with it. I use a 1/2" bit with a bushing in a router table... ____ | | _______________ 1/2" straight bit -> | || | || <- wood |____||_______________ ________bushing---->__| ||______________<- pattern
I don't rough trim with a bandsaw... I cut entirely with the router.
First difficulty is cutting the entire 3/4" thickness. It works best if I cut 3/16" or so and then raise the bit incrementally. The end result is pretty good.
Second difficulty is that the finished piece is approx 1/16" larger than the pattern. I take that into account when I make the pattern so it's not a problem.
Based on my experience, to address your particular difficulty, I would first suggest that your biggest problem is trying to trim 1/8" of wood in one pass. It may not seem like much, but it would seem to be causing problems. The wood is not getting cut cleanly. A sharp bit spinning effortlessly through the wood makes a nice clean cut with minimal tearing.
Because you are using a bit with a bearing, you don't have the option to incrementally raise the bit as I do so another solution must be found.
The most obvious solution is to trim a little closer with the bandsaw so that the bit doesn't have to work as hard.
Another possible solution (in conjunction with the suggestion above) is to use a 1/2" spiral bit. I believe someone makes one with a bearing. Exactly what you're using now, but a with a spiral cutter.
Hopefully you'll find some use in my comments.
Joe Barta
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http://www.woodcraft.com/family.aspx?familyid 16
Works great for me. Dave

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Thanks for all of your replies. I see my problem as trying to cut into the grain with a wood that is already prone to chip-out.
Excellent ideas. Flipping the pattern to the other side to continue to cut with the grain is probably the easiest. I like the robosander on my DP idea. With 50 grit on redwood, it would cut like a router bit.
Whiteside as a spiral flush cut bit but at $70, an expensive solution and would probably still cause tearout unless a backer board was used.
Thanks again for your suggestions.
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Consider also simply back cutting in the areas that the grain is prone to chip out. This is standard procedure when routing end grain on drawer fronts.
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I do this a lot. You generally go around the piece counterclockwise. When I get to a place where the grain is ending, such as at a curve, I feed backwards in small bites. When it is very close to flush I feed the proper direction. I think feeding back wards is called climb cutting. The blade has to be very sharp to cut end grain and you have to have a very steady hand and take small bites. max

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