advice - is it possible to route plywood?

[leehljp]

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

Capn

The more I thought about the plywood, the more I thought it could be just poorly glued ply or poor grade of wood in the center.

Loring, I know better than ask an engineer, but here goes: Can you shake the router at all? Is there any looseness to the router shaft if you try to wiggle the bit? ANY will cause chatter and add to the results above. Just wondering if something slipped into the equation unsuspecting like.

[steve-norrell]

Capn

The more I thought about the plywood, the more I thought it could be just poorly glued ply or poor grade of wood in the center.

This was also my first reaction in looking at the pictures. What is that middle ply? Its clearly not 'baltic' plywood, but I don't know if that would have made any difference.

I honestly can't remember if I ever tried to pattern trim plywood. I am blessed in that I bought one of those Rigid oscillating sanders several years ago and use that any time I have doubts about being able pattern trim with a router.

Good luck with your project. Steve

[LCHIEN]

Results

Well, in the end I got acceptable results.
I decided to wear goggles over my safety glasses.
First of all I slowed the router to about 10,000 RPM so I felt I had much better control.
Second I used a push block to hold down the item as I was a bit ginger holding it before due to the small dimensions. Part of the difficulty was the pegs I put in the template to align the work piece stuck up so it did not have a completely flat surface to rest the push block on.
Finally I think part of the roughness and chattering I felt was cutting the layers of glue (probably not that great for the bit either). More than with any other wood I've used pattern bits on I needed to forcefully drive the initial contact using the starting pin as a lever and get the bearing down to the template as fast as I could. Once the bearing was riding on the template it cut OK albeit still rough and chattering some. But no bad tearout. If I hesitantly pushed the piece into the spinning bit it would grab like heck and do all the damage you saw. Because of the chattering and rough feeling cut I was initially hesitant when starting the cut.

I really only had 1/16th mostly and not more than 1/8" oversize of the template and a 1/2" dia. bit. Often with other woods and long pieces I make a skimming pass where I don't have the bearing in contact with the template yet. That technique didn't work well here.

[Brian G]

I'm late to the discussion and it looks like you solved your problem. One suggestion I have for next time is to glue or screw a sturdy and comfortable handle(s) on your template. That makes your template perform double duty as its own pushblock.

[LCHIEN]

I'm late to the discussion and it looks like you solved your problem. One suggestion I have for next time is to glue or screw a sturdy and comfortable handle(s) on your template. That makes your template perform double duty as its own pushblock.

brian that was initially supposed to be the purpose of that black rod sticking out the top as well as being a alignment pin... A little small to hold onto, admittedly.

[chopnhack]

As for plywood quality, I just compared pricing for the Home Depot cabinet grade pine plywood AC versus the Chinese imported true cabinet grade plywood that is calibrated and it was double

Differences are the HD plywood top veneer is paper thin, think air mail paper.... it also delaminates if you touch the edge or blow on it.... other than that it is actually not all that bad. The C side is so good on most sheets you really can't tell which side is the good side The laminations are pretty much void free.

I have successfully routed profiles on this and the Arauco plywood several times. A light pass followed by successively deeper passes was all I needed to get good, blowout free edges. I typically was doing a roundover. I will only add that if the router bit had pitch or resin on it or simply was old and not sharp, tearout would occur. Try a better grade plywood and check to see if the bit is sharp.

As for the cabinet grade stuff from China at this particular dealer, its actually quite good... just $75-80 a sheet!

[LCHIEN]

OK I managed to complete these, except for the first one I bunged a bit they came out OK. Usually I'll make 5 to get four allowing me to hone the technique on the first one but in this case I got lazy and the scrap I cut it out from only fit four.

They are pretty much perfect clones with the hole positions and profile and even the arced slot lining up when stacked. Yes, I for the first time ever made a curved slot for an adjustment.

Here's the results. You can see the pivot and the two stop pins for the ends of the 5/16" curved slot.

I was a bit annoyed that with the base I used for the stops and center pin, that the straight router bit I used was just barely able to cut through the half-inch ply.
I had to use an oversized insert ring to allow the collet to raise up and I had to stretch the bit out of the collet a little to cut through then I had to countersink the back side of the half-inch hole the router bit passed through the jig base so that the 1/2" shank of the router bit could rise high enough, and in the end the tips of the router bit just barely breached the top of the workpiece. Yeah, it was a 5/16" 1/2" shank with a 1" cutting length - the standard MLCS straight bit. In the picture its as extended as I could get it. I guess I could have drilled out the opening for the bit to like 3/4" if I needed more. I didn't really want to drill that hole out because its my circle cutting jig as well! I usually put a 1/2" guide templet in that hole.

Wonder what Its going to be part of?

[chopnhack]

Interesting, it looks to be a hinge for something, but I would only have expected two...

[LCHIEN]

Project identified.

My new 12" CMS has a deck height that's over 2" higher than my old 10" CMS.
Needed some new feed/support rollers for my DIY miter stand.

(DIY Miter station thread here)

http://www.bt3central.com/showthread.php?t=20500

So, these rollers are the third generation. Fully adjustable and won't fall out. The knobs on the end are in the curved slot. THe arm pivots around the bolt next to the knob, its got a ny-lock nut to take up the slack but allow it to turn. The Roller is designed for the height of the deck plus mounting board and +/- 0.5" adjustment. Didn't have time to try it tonight but it looks good so far.

First couple of pictures show old vs new. The old had a simple slot and a wood screw in the bottom of the slot to adjust height. The roller axle was hex cross section and fell out easily (just held in place by gravity). The new one I cut holes whose diameter was smaller than the distance across the points of the hex... and hammered it into the hole. Nice heavy ball bearing industrial rollers I bought used from eBay.

[chopnhack]

Looks cool Loring! I like the adjustability feature. Are you concerned at all with weight of stock causing them to sink at all? I was thinking about that and thought of a row of holes at various heights to stick a pin through to lock the unit. Just a thought.

How much did the rollers set you back?

[LCHIEN]

A row of pins makes it have finite adjustments. If you have the adjustment arc of pins on a smaller arc than the arc of the roller then your adjustments are coarser than the pin spacing. which is in turn limited by the diameter of the pin how closely you can space them.

That's why I have a continuous slot.

So far I am able to lean on it heavily without its moving. I tried to maximize the surface area (fiction is proportional to the area of contact) between the fixed and moving parts. Plan B if it moves is to use PSA adhesive sandpaper between the two pieces to get a higher coefficient of friction. So far it doesn't look like i'll need it.

The test will be to bang a 4x4 onto it.

I bought the rollers, used, back in early 2011 - found the ebay receipt - $10 + 12 shipping for 6 rollers. (love that 10 GB of Gmail storage)
I saw 3 new ones nearly identical for $15 plus $17 shipping on ebay yesterday.

http://www.ebay.com/itm/380729280776?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

[chopnhack]

the test will be to bang a 4x4 onto it.

bingo!

(love that 10 gb of gmail storage)

oh, yeah!

. .

[LCHIEN]

actually its 15 GB!