The nature of plywood

[greenie512]

I thought I’d try and build my first small box after reading a recent mag. Now rather than waste a good bit of wood, I thought I’d first try with some scrap 17mm plywood. <o></o>

I cut one long board the correct height for the sides/ends and then cut 3 dado’s for the top/bottom panels and lid recess down the length and all went fine on the router table. I then cut the sides to length, then I put the big locking mitre bit in the router and failed miserably. I got nothing but kick backs while trying to cut the corner mitres. So gave up on the locking mitre and tried my large 45 deg bit – with the same results.

Just to check that I’m not totally inept (I certainly own up to being partially inept) I tried a small off cut of timber stud with no problems.<o></o>

I’m assuming the cross grain nature of ply is causing this kick back?

[damienhazo]

17mm is a pretty thick piece of ply... Regardless of wood-type, I always make a few passes if possible - the first pass being the smallest. This removes the leading edge and prevents breakout. If possible, I also remove as much stock as possible with a saw and then then do the fine work with the router.

Example (where possible):

A mitre join -
Run the piece over a sawbench set at 45°, leaving 1 or 2 mm on the leading edge. Then set up the fence on the router table (or guide piece for hand routing) to make your pass with the router. The router is then only removing a few mil over the entire blade and cutting much more efficiently.

Example (where not possible):

Making a V channel with a dovetail bit -
With passes of various depths, you will of course, end up with a Christmas tree. You can however, set up a saw bench to remove stock within the planned V then make a single pass with the dovetail bit to remove the remainder cleanly.

I have used this method successfully when making up pieces similar to those used in roll-tops. An example would be this dog's bed I built:

21697


I hope this helps.

Damien

[BobL]

. . . .. An example would be this dog's bed I built:



That is the most awesome dog bed I have ever seen! If your dog sleeps on that what do you sleep on?

And does your dog actually sleep on it? We have bought 3 beds for our dog and it just continues to sleep on the floor or waits till we go to sleep and it then goes to sleep on the leather sofa.

[damienhazo]

That is the most awesome dog bed I have ever seen! If your dog sleeps on that what do you sleep on?

And does your dog actually sleep on it? We have bought 3 beds for our dog and it just continues to sleep on the floor or waits till we go to sleep and it then goes to sleep on the leather sofa.
Thanks for the compliment. As for getting the dog to sleep in this bed....I'm working on it. The missus spoils our pure-bred Greek-Alley-Mongrel no end, and there are sheep skins and dog mattresses in every bloody corner. I like to think it's more a case of too much choice and too little taste...

Damien

[greenie512]

Damien - thanks for detailed response.

I think I might know why I’m getting kick backs.

Have a look at the attached photo of my current router table set up. I’m trying to work with small panels say 150 x 100 mm or less. What I think is happening is, as I feed the leading edge through, it’s “drifting” on the other side of the bit before it meets up with the fence on the other side. The movement/lack of control is causing the kick backs.
<o></o>
I need to make a Zero-Clearance fence for my lock mitre and 45 Deg bits when I’m using small components.

[damienhazo]

It's always a good idea to have a fitting table insert and minimum clearence on the fence but a 45&#176; angle removes a hell of a lot of stock. (Stock = (H X W)/2). I still advise removing the desired stock through a number of smaller passes. These passes should remove no more than 2 mm. Push all your workpieces though at each setting then reset the fence for the next pass. You might have to adjust the fence 7 or 8 times, but the result is much better.

Or, like I said, remove most of the stock with a saw first.

Damien

[greenie512]

Diamen - sorry I hadn't answered you on that one. Yes first attempt was full square stock but I soon realised I was trying too much and basically did what you are recommending. I think I set the mitre saw to 35-38 Deg to provide a good chamfer to start with but I was/am still getting these kick backs.

When I run large stock through these bits I have more control and as you say if you take small passes all goes well.

[rrich]

I see that your dog is master of the house, also.