Need to Build a Plywood Grooving Jig

[Mike Lagness]

I need to put V grooves 2" apart in about 10 sheets of 4' x 4' 3/4" plywood. I have a couple of ideas for a router fixture but was wondering if anyone else has done anything like this?

How to hold the plywood flat or have a weighted router fixture?

Lots of questions.

Thanks

mike

[Michael Pyron]

I would be thinking along the lines of a Festool router using their track system for that many sheets.

[Michelle Rich]

I think you might try the CB-7..it is an aftermarket router base that can do what you are asking. I think I saw it at Infinity tools

[Michael Pyron]

the CRB-7 does have an edge guide accessory but it only allows for 7 1/2" from the edge...too boot using an edge guide is a tricky thing as any slip and things go FUBAR real quickly (don't ask me how I figured that one out)

I'm making the assumption that flawless quality is desired and the only thing I can think of is a track router as it is locked in place and won't wander

[Charlie Velasquez]

A piece of 1/4" pegboard about 5' x 1',a workbench with a straight edge or a straight piece of 1x4x6', a couple of screws that fit in the holes of the pegboard snugly.
1. dog and wedge the plywood even with the bench edge using 1x so as to match the width of the ply (or on the 1x4, use another sheet of ply to get the top layer of ply to lay flat.) Dogging and wedges keep clamps out of the way.

2. remove the screws on the base of your router and screw the pegboard to the base such that the center point of your bit is centered over one of the holes in the pegboard in the 6th row. The rest of the holes in that row should now be in 1" increments from the center (or adjust it as needed to accommodate your specific distance for the first groove).

3. place a screw in the appropriate hole near each edge of the pegboard so the distance for the first groove is correct. And make the groove with the screw studs acting as bearings against the edge of the ply and bench (1x4).

4. Move the screws two holes down and repeat.

edit: Yes, I know, an edge guide, but moderate pressure and you should be good. You're not hogging out a lot of material. Should be easy to control.

Alternately
1. Shape a piece of stock the inverse shape of your groove, about 8" long or so.
2. Make your first groove with a clamped straight edge.
3. screw the shaped stock to your router base such that the midpoint is 2 inches from the center of your router bit and is perpendicular to a line from the midpoint to the center of the bit, use a square.
4. let the shaped stock ride in the first groove to make the 2nd
5. repeat

PS... Welcome to the forum

[Michelle Rich]

it will run in the groove it made and will hop the 2" , then hop the 2 inches. Just what he was asking for. Watch the video at Infinity or on Youtube

[glenn bradley]

If you just clamp a straight edge to the ply the small base of the router should follow any irregularities pretty well. You may want to make a couple pairs of of sticks that help you consistently set the position from the edge for each pass.

[Doug Garson]

Do you have a router table? Would be easy to run the plywood along the fence then index the fence 2" and repeat. A 4' x 4' x 3/4" piece of plywood would be easy to handle provided you have a reasonable sized router table.

[Charles Lent]

I think the best solution is a CRB-7 jig with a strip attached to the bottom to ride along the edge and then in every previously cut groove. Watch the CRB-7 demonstration video. It shows this exact feature. https://www.youtube.com/watch?v=VyS1JpKx684. The part most important for your need begins at 3:28 , but I'm certain that watching the rest of the video will further convince you that you need one of these jigs. Any router with guide fence rod holes can be mounted to a CRB-7. I've had one of these with all of the options that are available for it, and I use it frequently. My only problem with it has been my fault, when I didn't lock the router position on the rods sufficiently tight - my fault. Doing the operation that you want to do should go quite easy for you. Just be sure to keep some downward pressure on the guide strip area to keep it in the previous cut. The weight of the router should also help.

Charley

[marlin adams]

I had to do something similiar but not as many times as you are needing to do.

IMG_20180419_201714292.jpg I made a fabric cutting board for my mom and had to cut to V-grooves in it for cutting guides at certain lengths. I basically made a router guide from a 1"X3"x4' piece of poplar that had a striaght edge and attach it to a 1/4 inch piece of plywood that was 4 foot long and about 8 inches wide. Then I clamp it down where the plywood was overhanging a little where I took my router with my v-bit and cut off the excess sorta like making a saw guide
FH08OCT_SAWGUI_05.JPG But then measure from the point of the v-bit to edge of bit and factor in the offset. It work pretty good and keep everything striaght. I took it apart because I needed the popalor for another project or I would had taken a picture of it too.

v-bit.jpg

[Bruce Wrenn]

This idea was stolen from a book on jigs and fixtures (I'm not that smart.) Rip enough pieces of hardwood, 2" wide to go across your sheet. Glue them up, using canvas, as in the making of a roll front desk. Because this is a temp. fixture, you could use a lighter weight cotton cloth. Be sure and apply wax to edges before glue up so they don't stick to each other. Clamp one side to plywood, then use other side as an edge guide for router. When first groove is done, fold first strip back on top of the rest. Route and repeat.

[Mike Lagness]

Lots of great ideas. I have a bunch of aluminum t slot stuff and glides for it. I'm thinking of starting the piecing stuff together next week. Both sides as in left and right will have to be done to make them line up side by side.
In the big picture there might be 40-50 sheets over the next year so I need repeatable.

thanks and keep em coming