LumberJocks

Need Advice On Accurately Ripping Plywood With A Guide And Circular Saw

  • Advertise with us

« back to Jigs & Fixtures forum

Forum topic by Targa posted 12-09-2013 01:28 AM 3471 views 0 times favorited 15 replies Add to Favorites Watch
View Targa's profile

Targa

117 posts in 1206 days


12-09-2013 01:28 AM

I need some advice on the best ways to make straight rip cuts on 8’ lengths of plywood.

I’m about to start my first woodworking project of making a couple of bookcases for my daughter using oak plywood. I have a regular size craftsman contractor saw that I prefer not to try and use because its just too unwieldy to manage full sheets of 3/4” thick plywood by myself.

Instead, I’m trying to identify all the practical alternatives in which I can use my circular power saw along a straight edge for accurate ripping on the 8 foot length and I’m having trouble determining the best approach.

I’ve checked the archives on this site and found an interesting idea of making jigs using the factory long edge of 1/2” plywood attached to another piece of wider 1/2” plywood that would then be clamped to the piece I’m trying to cut. I bought a piece of good quality plywood yesterday and gave it a try using my circular saw but I’m not sure the factory long edge is real straight. The only tool I have, but do not trust, to verify the straightness of the cut or factory plywood edge is a 20 year old 2 piece flat aluminum cutting edge joined in the middle called “The Cutter’s Edge II All Purpose Cutting Guide” from Sears. I guess I may need to buy a 8’ long good quality level to verify straightness assuming you can depend on a level to be straight.

Here are some things I’m considering that I’d appreciate feedback on.

1. Purchasing a 8’-9’ long piece of aluminum flat bar stock 1/4” – 3/8” thick and 5”-6” wide and clamp it to the work piece. I’m not sure how straight this piece of aluminum would be.

2. Buy one of the several manufactured 8’ long straight edges with clamps built into the ends. Though I’ve read sometimes the clamps will slip after using them at the same setting several times plus the centers tend to lift or deflect especially with the side pressure of running the side of the bottom plate of the circular saw against them during a cut. I’m of the opinion that any guide that is made up of two pieces joined together is much less accurate than a one piece guide.

3. I realize the ultimate tool for what I’m trying to do is a Track Saw but the $600+ price tag is more than I’d like to spend if I can avoid it. After all, this is just a retirement hobby.

Please give me any suggestions or recommendations based on your personal experience.

Thank you

-- Dom


15 replies so far

View firefighterontheside's profile

firefighterontheside

13520 posts in 1323 days


#1 posted 12-09-2013 01:38 AM

The only cabinet grade plywood that I’ve seen that was not straight enough on the long factory edge was baltice birch, but those were 5 by 5 sheets. If you’re using more than one sheet of oak plywood you can use the edge of one sheet as a guide while you make the first cut. Then you can use the factory edge of the first piece you cut as the guide for subsequent rips.

-- Bill M. "People change, walnut doesn't" by Gene.

View kdc68's profile

kdc68

2526 posts in 1744 days


#2 posted 12-09-2013 01:41 AM

I use something similar to this to cut down sheet goods. Simple to make and inexpensive…...I cut my ply a little oversized and cut to final dimensions at my table saw.

http://www.popularmechanics.com/home/reviews/4283497

-- Measure "at least" twice and cut once

View Loren's profile

Loren

8314 posts in 3115 days


#3 posted 12-09-2013 01:42 AM

I think an angle iron (in steel or aluminum) is more likely to
be straighter than a piece of bar stock. Square tubing
is pretty straight too.

Aluminum you can usually get in 10’ lengths from a metal
dealer. Steel is usually sold in 20’ lengths. Hardware store
prices are a ripoff.

I suggest you take a look at the EZ-smart saw guide system
if you want to make cabinets and other casework without
upgrading your table saw. It’s a less-pricey way to get
into a track saw system. It works well and has a lot of
accessories available if you get really into it.

I use a 78’ level a lot in woodworking. They are like $40
and pretty straight. I don’t use it as a saw guide but it
can be used to line-up the two halves of your present
saw guide accurately. Mostly I use it for assessing board
flatness when milling solid wood stock. Comes in handy
doing carpentry too.

View Glen Peterson's profile

Glen Peterson

556 posts in 2523 days


#4 posted 12-09-2013 01:43 AM

You can make an easy jig that’s always accurate. You will need 2 pieces of 3/4 plywood, 8 ft long. One about 12” wide the other about 6” wide. the difference between the widths should be slightly greater than the base of your saw is wide. The narrower board needs to have 1 straight side. Glue and screw the boards together. The straight side becomes the guide for the contractor saw to ride against. The wider board is the base the saw sits on. Once the glue dries, run the saw along the jig and cut off the amount of the base beyond the blade. The edge of the base is exactly where future cuts will be. Just clamp the jig to the sheet of plywood. Match the edge of the jig to your cut line. I have an 8’ and a 4’ version for cutting up plywood.
Glen

Ps. What I described is exactly what kdc’s link shows.

-- Glen

View shipwright's profile

shipwright

7175 posts in 2265 days


#5 posted 12-09-2013 01:44 AM

For a lot less than the price of aluminium bar stock you can get a commercial shop or a friend with a jointer to true up a piece of 3/4” plywood. That said, I’m with Bill above. I’ve seldom seen a factory PW edge that isn’t close enough for this use.

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fibreglass trees. http://thecanadianschooloffrenchmarquetry.com/

View kdc68's profile

kdc68

2526 posts in 1744 days


#6 posted 12-09-2013 01:45 AM

+1 Glen…his post describes the jig I posted in the link above

-- Measure "at least" twice and cut once

View woodbutcherbynight's profile

woodbutcherbynight

2457 posts in 1876 days


#7 posted 12-09-2013 01:48 AM

+1 Glen, my grandfather taught me this same trick when I worked with him on the construction site. It works well and is worth the spend plywood for a excellent straight cut. I did find a straight piece of steel that said it was a stamped guide in his garage when he die, looked like he used it maybe twice. (laughing)

-- Live to tell the stories, they sound better that way.

View WibblyPig's profile

WibblyPig

168 posts in 2741 days


#8 posted 12-09-2013 01:48 AM

I very rarely use plywood but this is a Godsend: http://www.lowes.com/pd_287348-39450-KMA2675_0__?productId=3654122&Ntt=saw+guide&pl=1&currentURL=%3FNtt%3Dsaw%2Bguide&facetInfo=

-- Steve, Webster Groves, MO "A society grows great when old men plant trees whose shade they know they shall never sit in."

View waho6o9's profile

waho6o9

7179 posts in 2044 days


#9 posted 12-09-2013 02:04 AM

View TaybulSawz's profile

TaybulSawz

149 posts in 1149 days


#10 posted 12-09-2013 02:21 AM

The Link KDC68 posted is the best jig to use for what you are wanting to do. In conjunction with a Plywood cutting Platform you’re good to go. I alway cut my stock 1/4” over and then re-run it through the Tablesaw to true it up.

-- Still got all my Fingers!!!

View tefinn's profile

tefinn

1222 posts in 1904 days


#11 posted 12-09-2013 02:22 AM

I’m with kdc68 and Glen Peterson. I made the same cutting jig years ago and still use it. Cut your pieces a little over and trim them to exact on your table saw.

-- Tom Finnigan - Measures? We don't need no stinking measures! - Hmm, maybe thats why my project pieces don't fit.

View Targa's profile

Targa

117 posts in 1206 days


#12 posted 12-10-2013 12:43 AM

I think the jig described by kdc and Glen Peterson using two pieces of plywood is a accurate, practical and low cost approach which is exactly what I’m looking for.

Its what I built over the weekend but questioned its accuracy because the two piece straight edge I used to validate it is not perfectly straight.

Thanks everyone for your quick and insightful responses. I appreciate it.

Now I can start cutting the expensive oak plywood with greater confidence.

-- Dom

View crank49's profile

crank49

3981 posts in 2438 days


#13 posted 12-10-2013 04:11 AM

I also like the exact guide that KDC68 posted in his link.
It is the best jig to use for ripping sheet goods.

In addition to being easy to see where your cut will be, it also provides half of the cut with a zero clearance backer.
This avoids tear out on one side of the cut. With some thoughtful planning that will be on the keeper side of the cut.

I have a nice table saw, but I use these guides for virtually all my sheet goods breakdown.
Another useful tip is to lay a sheet of Styrofoam on the shop floor and do your cutting on top of that.
Just set the circular saw blade to a depth that barely penetrates the cut and the foam backer will last a long time.
This is much easier than trying to balance everything on saw horses.

-- Michael: Hillary has a long list of accomplishments, though most DAs would refer to them as felonies.

View gfadvm's profile

gfadvm

14940 posts in 2157 days


#14 posted 12-13-2013 03:06 AM

I use a 10’ piece of aluminum square tubing BUT I do put a screw in the center to keep it from bowing or lifting off the plywood stock.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View Jake's profile

Jake

850 posts in 1098 days


#15 posted 12-13-2013 06:18 AM

+1 with gfadvm, I had 2 pieces of steel angles made, 9 feet lenght, with screw holes punched in and I also pop a few screws in the middle to make sure it does not move around.

Making straight cuts with any straight edge is quite easy as long as it is around the 6 feet mark, further on the tubing or any material for that matter will start to bend a bit, so this is what you have to be most concerend about. Of course this does not apply to the 3/4×3/4 plywood edge glued and screwed together, but I alway found it too clumsy to use and I managed to score it after a few uses, so the full edge wasn’t as striaght as it ought to be.

That’s why i use my angles 2”x2” L brackets 9 feet lenght, made of 2mm steel.

-- Measure twice, cut once, cut again for good measure.

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com