Kerf Cutting Plywood

[les_linton]

Hello guys. To help out one of the sales guys at my real job the other night I came home and made a double ended bull nosed starting step.

This is an 8" wide 102" long piece of maple plywood bent around a pair 5-3/8" R forms set into a pair of 3/8" dados (grooves for the purist) at both ends.

It had to be done that night, so I really didn't have the time to experiment, nor did I have an 1/8" bit.

I made the bending forms on the Bot and went to doing the dados and kerf cuts the old fashioned way... on the table saw. Saw blade kerf, 1/8", then move 3/8" and make the next one leaving a 1/4" standing for 25" on both ends. I'm cutting thru to the last full layer of the ply, approximately 5/8".

My question, can I do this type of kerf cutting using an 1/8" bit in plywood without breaking out a lot of the 1/4" pieces and a lot of bits?

I'm sure feed, speed and type of bit are critical to this and would appreciate some starting points to get me on my way.

I am going to experiment with this over the weekend and any help would be appreciated.

Thanks guy,

Les

[waynelocke]

In my youth I worked in a shop where we made many curved reception desks by taking 3/4" hardwood plywood and kerfing it. We left only 1/8" splines and acheived remarkably smooth curves. Kerfing almost a full 4X8 sheet of plywood took consideable time and was terrifically stressful because success and total failure were so close. It was a real zen experience, boring, repititous and requiring intense concentration and attention.

You would need a really good vacuum table to keep the ply flat because it tends curl a little bit after kerfing. Also, given the fragility of the splines a router bit may wreck havoc on them. The life of an 1/8" bit would be a concern if you had much kerfing to do.

I would love to see how your experiments turn out. I have fond memories of the process and what can be acheived...and no desire to relive them. I am happy to have moved on to vacuum bags and laminated curved panels.

You might just need to center yourself, think about the possibilities for growth and fire up the tablesaw.
Wayne Locke

[les_linton]

Wayne,

I had to smile with your reply... every word a truth... "a real zen experience, boring, repititous and requiring intense concentration and attention"

The piece I made had 1/8" splines and kerfs, but the factory one, mdf core ply, had 1/4" splines.

My thought was to make a hold down fixture that I would fasten to the table and set the z move height above that.

Thanks,

Les

[rookie432]

have you guys seen the "bendy" plywood that you can bend around a form then veneer and the veneer will jold it to the shape.
Tried some on a bar project. was kinda neet and no kerf cutting. Used zebrawood veneer, oooohhh!

[beacon14]

There are a few guys who've mounted small saws to their ShopBots. That may be the ticket for this application, if you have a lot to do. If it's only a few, I think the table saw would be faster.

I have not had good results leaving a thin ridge between two deep router cuts, at least not when I wanted the ridge to remain intact. Plus the number of passes required with a 1/8" bit would take forever to comlete.

[gene_marshall]

I agree with Bill.
Neat form bendy MDF is a joy to work with.

Bends perfectly and takes the veneer very well.
use a double thickness if you need 3/4.
and it comes kerfed along the 48 or 96 length

I have tried this on the bot with solid stock.
A down spiral 1/8 end mill(cannot be a ball end)cutting the full depth at a slow speed.
And the slightest warp to the board will ruin the peice.
try it you'll like it
gene

[les_linton]

Well, you guys have pretty much convinced me that using the bot for this project may not be the best method, although, I'm sure that I will have to at least try a small piece.

I thought about the bendable ply and mdf, and I'm pretty sure that it would do the job, but using it for the bottom step on a high end staircase... I'm just not comfortable putting my name on that.

I think that since these are one up, custom units, I should probably just make a new table saw sled and do it the old fashion way..

Good ideas, and thanks for your thoughts.

Les

[beacon14]

I've had good results with products from these folks:

interior products (http://interiorproducts.com/)

Some of them you wrap like bendy board, then veneer, others you can veneer or laminate one side, then wrap to your form.

[gerald_d]

"Saw" mounted in SB (http://www.talkshopbot.com/forum/messages/28/6583.html) - actually a baby angle-grinder.