advice - is it possible to route plywood?

[LCHIEN]

I thought I could route some small 1/2" thick plywood pieces. I wanted plywood because I thought I wanted some wood that wouldn't split along the grain.

I tried to use a 1/2" pattern bit like this from MLCSWoodworking


in a router table. THe pieces were about 5" long which is a bit of a problem because the pivot pin was about 3" from the bit.

When I tried to start the wood feeding it the correct direction into the spinning bit, it grabbed and it was like routing end grain the whole way around. I didn't go very far as I really didn't feel comfortable. Felt like it was chattering a lot. Made a mess out of the wood. (see picture below).

Is is practical to pattern rout plywood?

I'm going to make a holder jig with some 3/4" wood and a jig (toggle) clamp holding it from above. I'll have to raise the bit 3/4" more to compensate.

Is this the best way to do this? I'm Not too happy with the way this has gone. I'm going to have to go back and cut another blank...

In the picture below I have a 1/4" plywood pattern. I cut close with a bandsaw and pegged the two pieces together with a 1/4" bit and a dowel and a 1/4" transfer punch I thought might help make a safer handle than holding the piece.

THe last picture shows the completed routed piece after I slowed the router some (probably backed from 20,000 to 16,000 RPM) but it looks like heck.
I have several more I want to do.

[jussi]

Perhaps make a jig that can carry the piece and hold it down with toggle clamps. I haven't used plywood but did have to pattern route some highly figured wood before and hand to use a spiral pattern bit

http://www.finewoodworking.com/item/25690/pattern-routing-jig

[mpc]

You can get bearing guided sanding drums for a drill press for "pattern sanding." I'd expect that to be a lot cleaner but slower than pattern routing. The one time I tried a small router job on plywood it made a real mess. And that was with good Baltic Birch plywood, not thicker/coarser layered stuff. I was just trying to put a small roundover on the plywood if I remember correctly.

mpc

[woodturner]

When I tried to start the wood feeding it the correct direction into the spinning bit, it grabbed and it was like routing end grain the whole way around. I didn't go very far as I really didn't feel comfortable. Felt like it was chattering a lot. Made a mess out of the wood. (see picture below).

I'm confused by this observation - if it was being cut against the rotation of the bit, I don't understand how it could grab.

I've pattern routed Baltic birch plywood with essentially no issues. I just made a 1/4" plywood or plastic template, secure it to the blank, and used a pattern bit in a router table. With the bit rotating clockwise, I fed the work from right to left, below the bit. In other words, the bit was rotating into the cut.

I'm wondering if you have a dull or defective bit - I've not had an issue like you are experiencing. Might also be some issue with plywood, but I'm not sure what that could be.

Edit: After looking at your photos more carefully, that looks like lumber core ply, and it looks like the inner, lumber core is the one that is a problem. I'm wondering if it has voids in the glue so that the inner core is delaminating.

[capncarl]

Looks like a job for a stationary disk/belt sander to me. You know the saying, plywood warps like plywood, well, plywood routes like plywood as well.
capncarl

[leehljp]

I immediately thought of the MLC "shear angled flush trim" bits which should eliminate that. I have not seen that much tearout before.

http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/bt_flush.html

Do spirals come in a flush trim?

[JimD]

I guess I have never tried. I would agree that is going surprisingly badly. The main pattern routing I have done is on kitchen chairs using plans from woodsmith. The back legs are pattern routed. I alway dread doing the top of the legs because it is end grain. I try to take light cuts but it still sometimes grabs. I usually get a usable leg but sometimes have to sand out chipping.

By it's nature you will always have some end grain involved when cutting plywood. Maybe that is the issue?

I've dovetailed a lot of baltic birch making drawers so for that operation I have proven to myself I can treat plywood like solid wood. But maybe pattern routing is different.

[Ken Massingale]

Loring,
To me it looks like you left too much ply around the template in pics 1 and 2. The bit would then cut without the bearing riding on the template.

Ken

[Cochese]

Loring,
To me it looks like you left too much ply around the template in pics 1 and 2. The bit would then cut without the bearing riding on the template.

Ken

That was my first thought as well. I think perhaps next time use the fence to help do it in stages.

The other thought would be to have a wider base to have your hands better steady the work and control it. Rockler and others sell a small piece holder but it can be as easily accomplished with a sqeeze bar clamp.

[LCHIEN]

Loring,
To me it looks like you left too much ply around the template in pics 1 and 2. The bit would then cut without the bearing riding on the template.

Ken

Ken, In the second picture it only stuck out that much after the bit tore it up.
I pre-trimmed it pretty close all around if you look at the other pics. By definition the first contact will always be without the bearing in contact...

Maybe the problem is that every side you route on in plywood is/has end-grain...

[LCHIEN]

I seemed to have had a lot more control after I slowed the router down... I initially figured that near max speed was OK since the router bit dia. was only 1/2"
Since If I can't route them the other pieces are useless I may go ahead and try routing them at maybe 10K RPM, even slower than what I finished that piece at.

[LCHIEN]

I immediately thought of the MLC "shear angled flush trim" bits which should eliminate that. I have not seen that much tearout before.

http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/bt_flush.html

Do spirals come in a flush trim?

MLCS has shear angled flush trim bits, a 1/2" shank, 1/2" Dia., 1-3/16 long is $13. just ordered one.


They also have solid carbide spiral upcut flush trim similar specs for $54!


images from mlcswoodworking.com

[Black wallnut]

For pattern routing if the piece is too small to effectively use a pivot pin it is best to make a jig to hold the piece so that the bearing rests on the jig prior to the cut being started thus using the jig as the pivot. Still then with lumber core plywood I'm not surprised with your results. Sometimes even the best technique does not work. i.e. making arched door rails; sometimes I've cut and routed several before finding one that did not grab and chipout.

[jussi]

They also have solid carbide spiral upcut flush trim similar specs for $54!

You need to pick up this one up. A mere $135.

http://wnwoodworkingschool.com/shop/index.php?main_page=product_info&products_id=2

[capncarl]

I have not run into ANY plywood lately that routes worth a flip. I suppose that cabinet shops might have a better source, I would hope so because the cnc machines all use router bits. My latest plywood from the local box store was mfg in China. It cut ok but the outside ply chipped when using a dado blade. I saw all kinds of hollows in the plys on the sides, I bet it would route just like your plywood. If you did not have a lot of patterns to cut you could screw a stack together and cut the whole batch at one time on a disk/belt sander.
capncarl