Why did this happen (router question)

I am building a table top out of 4 edge glued boards. 2 of the corners have a radius to them. I have a piece of MDF that I am using as a template, with a trim bit and about 1/8 to 1/4 overhang rough cut with a jigsaw. I am moving around the edge counter-clockwise. As I cam up the left end and round the turn around the first radius, suddenly the router "caught" and a hunk of the edge tore loose. I moved past it and completed the rest of the cut around the edge without incident. I glued the broken piece in and it isn't noticible, but now I have to match the edge and I'm leary of using the rounter on it.
My theory is that that point of the cut was just too thick and I was taking too much off at one time, and perhaps the grain was funny there. The way I want to proceed once the glue has been on for 24 hours is to sand the offending piece down to about 1/16" from the template and then route that off.
Thoughts?
-Jim
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jtpr wrote:

As you rounded the radius the direction of the grain in the wood changed and instead of cutting across it you found yourself cutting against it. I like working ash and mahogany. Mahogany is fairly well behaved but the ash as a tendency to tear along the grain line when cutting against the grain. There are two ways to avoid the tear out. 1) Don't rout against the grain, always rout with it.
The second is useful when you have to cut against the grain. The simple cure is do a "climb cut" where you rout in the direction your router is turning. The one thing to watch is that it does not take off on you, meaning you have to hold it tight to the piece and be ready for it to start to run away with you. As long as you are careful, it works like a champ.
Deb
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wrote:

I agree with Deb. Climb cutting, when done with caution and common sense (router hand held ... NEVER in a router table) taking small cuts and nibbling away slowly, is the best way to handle tough grain.
Lenny
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Radius only the right hand upper corner. (Facing a piece of paper, the upper right hand corner where the date often goes). Turn the work over as you go so you're only routing that corner. **************************************************** http://www.patwarner.com (Routers) *****************************************************

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The answers about routing end grain or against the grain is like the others said, climb cutting, especially at corners.
However, now that you have this situation with a glued in patch, you might consider using some hand tools such as a coping saw, super sharp pairing chisel, rasp, file, custom shaped scraper, etc. Or even multiple nibble passes with the table saw at various tilts to trim close to the radius. Then make a reverse shape sanding block and sand it out to a good finish.

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What about a spiral up- or down-cut bit? Aren't those supposed to yield less tear-out?
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-MIKE-

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Spirals do a little better but once a spiral grabs it really grabs. Unlike a wing cutter that is going bang, bang,bang, if the spiral grabs the wood it seems to just pull quite a bit more. My most dangerous router stories involve spirals. I now pretty much only use them in a table, but this is just my bias, having broken one while freehanding and luckily having it not embedded in my gut, as it was in the wall.

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Wow, that seems totally counter intuitive (to my mind, at least). Thanks for the valuable info.
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Thank you all, I see the error of my ways now. But isn't Pat Warner's suggestion really the best one? Just turn it over first and do the last radius?
-Jim
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But isn't Pat Warner's suggestion really the best one? Just turn it over first and do the last radius?
-Jim
I know *I'd* never question Pat's wisdom re: routers, router safety, techniques, etc.
my $1/50, ymmv, etc etc and so on and so forth....
jc
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Joe wrote:

If the shape of the workpiece allows it, then yes, turning it over is the easiest way to continue routing "with" the grain, but it's not always possible. Otherwise, some form of climb cutting is the only alternative (other than foregoing the router for other methods, as previously discussed).
What I usually do (after removing as much waste as possible using other methods, such as the bandsaw) is to reposition the piece on the downside of the waste area, as though I'm going to make a full climb cut, but I'll take a bunch of little router-bit-sized "bites" out of the tail-end of the waste area, keeping the workpiece moving in a circular motion against the grain and into the bit (so it's not *really* a climb cut), using push blocks to maintain firm downward pressure and with very firm and deliberate strokes to prevent the bit from grabbing the workpiece.
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Well, I got to it last night and all went well. I ended up using the router and took very small bites out of it until it got almost to the template, then finished it off. A little sandpaper and then a rounding bit, and you can't see anything. Thank's for all the advice. Now for finishing...
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Thanks for all the help. If anybody is interested, this is how it all turned out...
http://picasaweb.google.com/jtpryan/BarTop?feat=directlink
Jim
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Thanks for all the help. If anybody is interested, this is how it all turned out...
http://picasaweb.google.com/jtpryan/BarTop?feat=directlink
================================= Looks nice. I like the thin stripes of darker wood in the midth of the top.
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Nice!
-Kevin
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Very nice.
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