Router and Flush Cutting Bit Disaster

[Dennis Putnam]

I had a major disaster with with my flush cutting bit last night. I needed to trim my face frame edges so I used a brand spanking new flush cutting bit. As I started trimming, the wood (birch) began not just tearing out but splitting out. I have one spot where a huge chunk (maybe 1/8" deep x 1") was torn out (I have no idea how I'm going to fix that). I tried slowing my feed rate, speeding it up, nothing seemed to help.

What did I do wrong? I've done flush trimming before with no problem but this is the first time I tried to trim anything this wide (3/4") but at thickest part I was trimming <1/8" at most. The only thing I can think of is the bit diameter was too small. Is there a rule of thumb for the bit diameter vs. the width of the material to be trimmed? It seemed the larger the diameter the shorter the blades was the way the case was stocked at the store. The bit I used was 3/8" because it was the only one that was 1" long.

[Cliff Rohrabacher]

brand spanking new flush cutting bit.

What make? Was it actually sharpened at the factory? Errors do occur.

Was that Birch solid wood or Ply??

splitting out. I have one spot where a huge chunk (maybe 1/8" deep x 1") was torn out (I have no idea how I'm going to fix that)

Piece it in. Use a chisel and cut the chip out to some geometry you can cut a patch for. I like to taper the ends to little points: helps hide the repair.

What did I do wrong?[...](3/4")

Prolly nuthin. 3/4" ain't much neither.

The only thing I can think of is the bit diameter was too small.

Doubt it.

Is there a rule of thumb for the bit diameter vs. the width of the material to be trimmed?

Not to my knowledge. It's all about sharp edges when routing unless you have a feed rate that is so aggressive that the cutter can't clear the chip (a CNC issue not hand routing).

Get yourself as Whiteside cutter and lose that nickel plated sissy pistol.

The only thing I can think of is that the bit is defective.

[Chuck Saunders]

Probably just a grain direction issue. Unfortunately unlike a hand plane, you can't work in both directions equally. You will get better results going the opposite direction but you will be climb cutting and the router will have a tendency to run away, firm grip and light cuts will be the name of the game.

Hope this helps
Chuck

[Dennis Putnam]

Thanks for the repair tip. Not sure I have the skills (I don't seem to have the patience for a chisel and wind up gouging too deep) to do that but it sure has to be better then wood filler. Fortunately the chip doesn't go all the way to the edge so from the front it won't be noticeable.

The bit was a Ryobi. My normal router bit store is closed by the time I can get there week days and I didn't want to wait until Saturday where I usually get Freud or Vermont American. Guess I should have waited as I'll be doing something other then making the doors, as it turns out anyway. :-(

[Dennis Putnam]

Probably just a grain direction issue. Unfortunately unlike a hand plane, you can't work in both directions equally. You will get better results going the opposite direction but you will be climb cutting and the router will have a tendency to run away, firm grip and light cuts will be the name of the game.

Hope this helps
Chuck

I tried going the opposite way but I guess I'm too weak. I just couldn't control it (unlike Norm I don't have a drawer full of routers where I might have gotten a smaller one). Maybe I should have taken the wimp's way out and sanded it down but that takes a lot of time and patience, neither of which is very plentiful. Does that mean I'm pursuing the wrong hobby?

[Jules Dominguez]

I'd think grain direction. I've had experiences with flush cutting bits really grabbing the wood. I've learned never to start a cut in end grain, but ease into it. When I make my rough cut before routing, I try to leave as little wood as possible to trim, generally no more than 1/16. It's safer sometimes to climb cut bad sections.

[Matt Day]

I would think grain direction is the culprit, as mentioned above. I would do my best to take as little material off as possible, especially considering you're off 1/8" of material with a 3/8" bit. In my experience (which is amost zero compared to some people here!), splitting in large chunks occurs most when you try to take too much material off.

[Rich Torino]

Would a spiral flush trim bit have prevented the tear out due to grain direction??? Just a thought..

[frank shic]

dennis, were you trying to flush the outside edges of the face frame to the case?

[Dennis Putnam]

dennis, were you trying to flush the outside edges of the face frame to the case?

Yes. Sorry for not being clear.

[frank shic]

dennis, spare yourself the hassle in the future and just leave the reveal. once the cabinets are joined together, no one will be able to tell if you flush trimmed them or not. even on exposed ends, a small reveal around 1/16" is acceptable since the wood is going to expand and contract anyways. a hand plane is a great alternative if you know how to sharpen one. look on the bright side: at least you didn't hurt yourself!

[Peter Pedisich]

Dennis,

I've had the same thing happen to me with an inexpensive flush trim bits.
The problem was lessened greatly, but not completely, by getting a higher quality bit (Amana in this case).

I have had good luck getting smooth, chatter free cuts with Amana bits.

The grain direction was the problem with mine too.

Good Luck,

Pete

[Cliff Rohrabacher]

Maybe I should have taken the wimp's way out and sanded it down but that takes a lot of time and patience, neither of which is very plentiful. Does that mean I'm pursuing the wrong hobby?

No it means you need to spend more money on more expensive tools. Lots and lots more.

[Dennis Putnam]

dennis, spare yourself the hassle in the future and just leave the reveal. once the cabinets are joined together, no one will be able to tell if you flush trimmed them or not. even on exposed ends, a small reveal around 1/16" is acceptable since the wood is going to expand and contract anyways. a hand plane is a great alternative if you know how to sharpen one. look on the bright side: at least you didn't hurt yourself!

In this case it is a home theater equipment cabinet so it needs to be furniture quality (euphemistically :-)). Also, this is my first real project (obligatory beginner bird houses don't count) so there are some flaws that made the "reveal" (I call it mistake) irregular so the trimming was necessary. I though of a plane but since the carcass is plywood I was afraid it would be gouged. Next time I won't have as much "reveal" to deal with (hopefully) so sanding will be sufficient.

I am going to put solid wood around the edge of my plywood top and shelves so I will be more careful about thickness there (along with challenging my poor mitering skills). I'll use the shelves for practice since I only need to do one edge on them.

[Dennis Putnam]

No it means you need to spend more money on more expensive tools. Lots and lots more.

Then maybe I really am in the wrong hobby. The problem is, it is a long time between adding expensive tools and I can't just let the one's I have sit until I get the whole shop outfitted. Do you have any idea how many honey-dos are needed to buy just a jointer, which is what I want next?