TS55 8ft plywood cut

[sancho57]

Some good info here. This very question has come up in the past. One thing that hasnt been mentioned is your technique. On long cuts we tend to pull the saw one way or the the other which will throw the cut off a tad.

Its best to stand behind the saw ensuring that your not inadvertantly pulling the saw to one side or another.

 

[WeekendWoodWerker]

The clamps!??

- I checked for straightness of the rails again with another 48" straight edge. I also checked at the front edge of the bump in the rail that the saw rides on instead of the back of the rail.

- I made several more cuts exactly like before, each time I encountered the same issue. Same direction of bow and same magnitude of error, sometimes worse than the 1/16th inch from original post, never better.

- Just after a "bad" cut, if I butt the cut edge against the waste-side edge, they don't match. Not even close... they touch on the ends and have big gap in thr middle.

- As an experiment, I ripped a clean edge again using the track with NO clamps, and then made several more cuts following the exact procedure before except this time omitting the clamps.

- The results of the cuts without the clamps were that the kerf matched almost exactly after the cut and much much less error than with the clamps.

This doesn't prove anything since they are, of course, different cuts, but I think there is something to it.

Either way, I have no doubt I could improve on my technique over time. And I will likely be over sizing rips like these in the future and then trying to true up with a second cut.

Thanks again for all the ideas and support.

 

[waho6o9]

" Using dewalt track clamps at both ends,"

Interesting results omitting the Dewalt clamps.  Good job.

 

[clark_fork]

Let's talk about cutting surfaces and direction of cut.

Are you cutting an overhang or cutting into a MFT table? I don't like to cut up my MFT for rip cuts.

I use a 4'X 8' sheet of 2" Styrofoam as my surface. If I am using my serpentine folding table I mount the Styrofoam on as sheet of plywood. By cutting into Styrofoam, I have no sag as I might if I am cutting an overhang.

You might also think about the direction difference of a left hand cut and a right hand cut. You may push differently depending on left and right.

 

[Bob D.]

"I have a table saw but don't have the skill or means to feed a 4ftx8ft sheet of 1/2" ply through it by myself safely"

What are you calling a table saw that will not handle a sheet of 1/2" ply. Is it a jobsite saw, contractors saw, hybrid, or cabinet saw?
For a portable jobsite saw I could understand this without any additional support. A contractors saw or a hybrid with some in and outfeed support should be fine. The RIDGID FlipTop stands work well and are easy to adjust for height and fold up quickly for storage. I had a contractors saw for years and used a pair of FlipTop stands along with a good size outfeed table and had no problem ripping sheet goods. I sold that contractors saw 9 years ago and bought a new Unisaw and built a large outfeed/assembly table for it and came up with a solution for infeed support that works in my small shop. I can concentrate on running my workpiece through the saw and not worry about supporting any of it.

At the time I did not have a track saw, so the table saw was my best bet for cutting sheet goods. Not long afterward I got the DeWalt track saw and a couple years later the Festool TSC55 but I still use the table saw at times.

Because my workbench is located behind the table saw it can be used to support long or wide pieces when working at the table saw. At first I would clamp a piece of plywood to the bench at the same height as my table saw which is about 3 inches higher than the bench. Then I made a support that made use of the dog holes in the bench to I could drop it in and it would be ready to go in seconds with no tools or clamps required. Later I added a fold-up side table extension to my outfeed table to give me more room for project assembly. This also gave me about 36 inches of support to the left of the blade on the table saw extending 57 inches beyond the blade.

Not long ago I made a short video showing the outfeed table and the infeed supports I made for use with my workbench.

 

[Birdhunter]

This has been a fascinating thread.

I always use Baltic Birch plywood cut mostly on a big SawStop and I’ve never seen the wood move after cutting. If I’m cutting really long cuts with jointed guides, I do a rough cut and trim on the table saw.

I wonder if the quality of the plywood has any effect on movement.

 

[Mike Goetzke]

View attachment 1

I had similar results so I attached a center stop to reduce lateral movement.

YMMV

[member=7659]waho6o9[/member] You are using a single rail and getting bow in the middle?

[member=71406]WeekendWoodWerker[/member] First off, 1/16" over 8' with two cuts back to back is pretty good. I have been taught and experienced that ply usually has nice straight/parallel edges across the width but don't trust the lenghtwise sides. Maybe try ripping a clean edge first?

(About 20 years ago I bought my first ripping rail when I was ripping a piece of 3/4" ply by myself (and a couple roller stands) and actually got the cut to bind up so bad it stalled my 3HP Uni and I was 7' from the stop switch.)

Mike

 

[waho6o9]

[member=7659]waho6o9[/member] You are using a single rail and getting bow in the middle?

Yes, without the center clamp on the one piece rail I would get a bow because of lateral movement as I push
the saw with my left hand.
After I check all three measurements, both ends and the middle, I'll rip the sheet goods. 
The preferred method is two at a time with my TS75. 

 

[Cheese]

Not long ago I made a short video showing the outfeed table and the infeed supports I made for use with my workbench.

Nice solutions Bob.  [big grin]  I like both the folding side and the dog hole rear risers.

 

[Michael Kellough]

The clamps!??

- I checked for straightness of the rails again with another 48" straight edge. I also checked at the front edge of the bump in the rail that the saw rides on instead of the back of the rail.

- I made several more cuts exactly like before, each time I encountered the same issue. Same direction of bow and same magnitude of error, sometimes worse than the 1/16th inch from original post, never better.

- Just after a "bad" cut, if I butt the cut edge against the waste-side edge, they don't match. Not even close... they touch on the ends and have big gap in thr middle.

- As an experiment, I ripped a clean edge again using the track with NO clamps, and then made several more cuts following the exact procedure before except this time omitting the clamps.

- The results of the cuts without the clamps were that the kerf matched almost exactly after the cut and much much less error than with the clamps.

This doesn't prove anything since they are, of course, different cuts, but I think there is something to it.

Either way, I have no doubt I could improve on my technique over time. And I will likely be over sizing rips like these in the future and then trying to true up with a second cut.

Thanks again for all the ideas and support.

This is the classic indication of tension in the wood. If the cause of curved cuts was the guide rail alone then the offcut would match the main piece. But, whenever you join two rails the straightness of the guide is always suspect so it’s hard to know after one bad cut what the cause is, unless the offcut does not match the main piece.

To test the guide rail straightness make another cut just a few mm in from the edge. It’s extremely unlikely that removing that small amount will cause even a tensioned panel to move so if the edge is not straight you can blame the guiderail.

Experimentation is a great way to learn but the results of tests can be difficult to interpret since the material you are cutting is an unknown variable. As you remove strips from a tensioned panel they may naturally become more or less bowed despite you using the same technique.

Since you never know if you’re cutting into a more or less tensioned territory you should leave enough margin between parts to allow for recutting to final size.

 

[WeekendWoodWerker]

Let's talk about cutting surfaces and direction of cut.

Are you cutting an overhang or cutting into a MFT table? I don't like to cut up my MFT for rip cuts.

I use a 4'X 8' sheet of 2" Styrofoam as my surface. If I am using my serpentine folding table I mount the Styrofoam on as sheet of plywood. By cutting into Styrofoam, I have no sag as I might if I am cutting an overhang.

You might also think about the direction difference of a left hand cut and a right hand cut. You may push differently depending on left and right.

Probably can't see it clearly in the photos, but in my case I am making the cuts on a 4x8ft workbench that is flat and level and has a sheet of the 2" rigid insulation on top as a sacrificial surface.

What are you calling a table saw that will not handle a sheet of 1/2" ply. Is it a jobsite saw, contractors saw, hybrid, or cabinet saw?
...

Not long ago I made a short video showing the outfeed table and the infeed supports I made for use with my workbench.

At the moment I have a DeWalt 7491RS because I am space and power constrained. That saw doesn't have any problem cutting anything that I need to cut, it is just that I don't have a great way to feed a 4x8ft sheet goods through it straight. I have done it before, and it's fine for certain things, but in this case I feel that I should be able to make the cuts I need with the TS55. I mean after all, that is exactly the type of cuts I bought it for. I use the table saw non-stop for other stuff and I don't plan on stopping anytime soon... I will definitely watch your video. Thanks for the link!

[member=71406]WeekendWoodWerker[/member] First off, 1/16" over 8' with two cuts back to back is pretty good. I have been taught and experienced that ply usually has nice straight/parallel edges across the width but don't trust the lenghtwise sides. Maybe try ripping a clean edge first?

I never rely on the factory edge of plywood, even for gadgets around the garage / shop. In this case the first thing I did was run the TS55 along the edge removing ~a kerf width to get a nice straight edge.

This is the classic indication of tension in the wood. If the cause of curved cuts was the guide rail alone then the offcut would match the main piece. But, whenever you join two rails the straightness of the guide is always suspect so it’s hard to know after one bad cut what the cause is, unless the offcut does not match the main piece.

To test the guide rail straightness make another cut just a few mm in from the edge. It’s extremely unlikely that removing that small amount will cause even a tensioned panel to move so if the edge is not straight you can blame the guiderail.

Experimentation is a great way to learn but the results of tests can be difficult to interpret since the material you are cutting is an unknown variable. As you remove strips from a tensioned panel they may naturally become more or less bowed despite you using the same technique.

Since you never know if you’re cutting into a more or less tensioned territory you should leave enough margin between parts to allow for recutting to final size.

Agreed on all points.

 

[mhmcgrath]

One stray thought. I have used a little tool from Betterly that does a great job of lining up two rails as you install/tighten the Festool connectors.https://www.festoolproducts.com/bet...e-connector-for-festool-guide-rails.html?SID=

Sent from my iPhone using Tapatalk

 

[andy5405]

Joining rails and getting straight cuts has always been relatively easy IMHO. What has changed in my world has been the quality of plywood, there is some seriously dodgy stuff out there nowadays negating all the traditional benefits associated with ply as a stable material. It's got much worse globally since Trump was elected. Mods, that is not a thinly veiled political comment, I'm merely implying correlation not cause.