Squaring rails for long plywood cut

[Monju123]

Has anyone come up with a jig or fixture to ensure 90 degree cuts on plywood. I think there must be a way to attach a jig to the bottom of the rail (Using rail connectors or the like), that could rest against one face of the wood and align the cut. Anybody got one or should I try?

 

[Woodenfish]

When breaking down sheet goods I like to set my rails parallel to the edge using a framing square with some brass stair gauges to set the depth. Works great, repeat cuts are easy, stores quickly and is priced right. To me that's a home run.

 

[John Stevens]

Hi, Monju.  How wide a cut does it have to be?  I just use my MFT, but as deep as it is, it "only" can handle a crosscut of about 900mm (36").  So far I've always been able to "rip" sheet goods narrow enough to do the "crosscuts" on the MFT.  With a 1400mm rail and a short length of the MFT extrusion screwed to shims on the front and back of a table, you could do a custom-sized MFT + fence that would handle a 48" "crosscut."  Search the archives here and you can see how I've attached small pieces of extrusion to an MFT top.  You can also find some really clever designs by others for lateral extensions for an MFT, in case you want to crosscut 8' pieces.  Hope this helps.

Regards,

John

 

[JayStPeter]

I put a bolt through the angle unit.  It works great.  I've made 4 cuts all the way around to wind up with a ~42" square part and couldn't measure and difference between the diagonals.  My thread titled ' "Fixed" my angle unit' details what I did.  It makes a perfectly square cut every time now.

Jay

 

[Pat McFadden]

I use an 18" precision tri square from Woodpecker's. It's super accurate and solid, and has a heel to register on the edge of the sheet goods. Works great for 90 and 45's. Kinda pricey at around $100, though.

Pat

 

[Dave Ronyak]

I use an 18" precision tri square from Woodpecker's. It's super accurate and solid, and has a heel to register on the edge of the sheet goods. Works great for 90 and 45's. Kinda pricey at around $100, though.

Pat

Ditto.  I highly recommend that precision right triangle square.  It is well worth its high price.  One edge of the the two forming a right angle has a thick lip that extends above and below the plane of the rest of the triangle.  This square is also very useful for setting up the fence and Guide Rail system on my MFT, and for use with Festool's Hole Drilling jig if you are not strictly following the 32mm system and need to register the Hole Drilling Guide Rail without reference to the top and bottom edges of your workpieces (cabinet sides), and generally checking your work during machining and assembly.  There is rarely a day in my shop when I don't repeatedly reach for that large triangular square.  A 12" Swanson Speed Square is likely a good, lower priced substitute to do what you want in aligning the Guide Rail at 90 degrees to the edge of the plywood sheet workpiece.

Dave R.

 

[UCLA Fan]

Hi Monju,

I use the stair gauges on a ruler for parallel then I square the ends off the now parallel edge. More accurate then using a "square" to set the rail. BUT a bit slower too. In addition to being more accurate the parallel method allows you to set exact repetitive cuts. Once the gauges are set you can run off as many cuts as you need with little to no variance. If you search this site for guide rail jigs you will find many clever ideas on to set parallel then square.

Regards,

Frank

 

[richard.selwyn]

Excuse me if it's already been mentioned but Festool have solved the problem with their rail add ons - FS PA

 

[Sparky977]

I may be speaking heresy here on the Fog, but I only use my TS55 for one side of a long cut.  I measure to slightly over size of what I need, since I never like the factory edge anyway, as it is never as "pretty" as I want it.  Then I cut to final width on my table saw.  At that point, I have two parallel sides and I do my crosscuts on the MFT.
Now, that said, I will probably be changing my methods somewhat, as I am planning on building a table based on Steve Jones' example: Cutting Table by Steve Jones

 

[fshanno]

The DeWalt T-Square fits the Festool rail.  Received mine a couple of days ago and I'm getting very good 90 degree crosscuts now.  This problem appears to be solved.

CPO DeWalt has them in stock.  Here's the link.

As mentioned, Festool has solved the problem as well, with the FS-PA which provides not only a 90 deg. crosscut but also a stop.  One day in the distant future it will be available in the US and our grand children will love it.  Meanwhile the DeWalt is only 26 bucks. 

Also take a look at the DeWalt clamps as well.  I bought a set and I love them, much easier to use under the guide than either Festool version.  On the down side they don't fit in the holes on the MFT, at least not without some grinding.

 

[festool_SWFL]

Has anyone come up with a jig or fixture to ensure 90 degree cuts on plywood. I think there must be a way to attach a jig to the bottom of the rail (Using rail connectors or the like), that could rest against one face of the wood and align the cut. Anybody got one or should I try?

I bought a 106" rail on Thursday.  I have to say, short of the Domino, ts55, ro125, ets125, cd12, of1400, mft3, it was by far my best purchase.  It really brings my TS55 to a whole new level.  If I am working on cabinets or paneling or whatever, I can simply make 2 cuts on a 4x8 sheet.  I make 1 to get rid of the factory edge and another to width.  Then I can cross cut everything else using my 55" rail.

 

[UCLA Fan]

The DeWalt T-Square fits the Festool rail.  Received mine a couple of days ago and I'm getting very good 90 degree crosscuts now.  This problem appears to be solved.... Meanwhile the DeWalt is only 26 bucks. 

Solved? not really but at least another tool that COULD improve square cuts...

I used the "t-square head" method for many years and found many frustrations as well. The idea of a T-square sounds great on paper and for many projects it is near perfect.  You must be careful with your cut sequence when using the t-square method. The small registration surface of the "head" can be a problem and unless the reference edge is "perfect" the error is magnified exponentially by the length of the cut. Usually not a big problem on cross cuts but on occasion I have had the cut wind up out of square by a quarter of an inch. Worse then that is sometimes you don't notice the first cut is off until you go to assemble your project and then ARGHHHHHHHHHHHH.

Now for full length cuts on sheet goods the small head is simply that... TOO DAMN SMALL. It is like using a 6 inch bubble level to build a 10 foot wall. RIGHT STRING WRONG YO-YO! My point here is you can't just "trust the t-square" head and lay it down cut and assume all is well. example: cross cut a panel of cheap plywood: if the "t-square" method were to reference an almost true edge the "almost" could cause the cut to be out by lets say 1/64" (.396 mm) not bad at all, now you find later you need to cut the long edge so you reference the new cross cut edge. this long cut is now out by at least 3/32" (1/64 from first cut plus 2/64 for the double length cut) now lets say you need at least four pieces of this ply for a cabinet and by the time you add up all the cumulative error you can be out by close to 1/2" and nothing will fit right. I know sounds extreme but it happens all the time. To get the best results with the "t-square" method don't assume the sheet is square and parallel to begin with. Use festool_swfl's idea, cut a clean reference edge one a long edge first. use that as your ref for all your cross cuts then square the final long edge. I know it sounds time consuming and tedious but it will save you much more time come assembly! Keep in mind when breaking down plywood, that all the edges on a sheet can be parallel and the the sheet can still be be way out of square (i.e. parallelogram). In fact with some cheap plywood I have had two opposite corners appear to be "square" and had the whole sheet be out a whack do to untrue edges.

Another option for those that like the "t-square" method is to use a 12 inch swanson speed square, cost about the same as the dewalt head and offers a much larger reference edge. I know many people see this as a "construction" tool and it ain't pretty, but mine is dead on when compared to my 12" Starret combo square. works great for the "t-square" method. Heck even the 7 inch swanson is at least as good as the dewalt head at it cost about 10 bucks 

For those that like the parallel technique of squaring sheet goods here is a link for an in-expensive and very precise method http://festoolownersgroup.com/index.php?topic=3341.0

Personally I find a combination of the techniques is often needed and is predicated by just how precise I need thing to be. Cutting subfloor or other construction panels where a gap is left for expansion anyway i just use a tape cut and move on. For general projects I use the t-square method. For the most demanding cuts that can lead to significant cumulative error I use the "cut a new long edge then square method" I think the FS-PA is going to be high on my future list but even then I will continue to let the job at hand define the technique.

So much for my "quick reply"  :

Frank

 

[fshanno]

Solved? not really but at least another tool that COULD improve square cuts...

It WILL improve square cuts.  Get it and see what it can do for you.

 

[Sean_C_G]

What if you were to use two Swanson speed squares to set a guide rail for a cut, one on either end of the rail? Would this help reduce the error inherent in using just one square to set the rail?

 

[mwhafner]

I solved my problem of squaring long cuts.  I took my FS-KS and fixed it at 90*.  I used 3M 77 spray adhesive (on both sides of the washers) to fix the angle, and then used JB Weld to finalize the process.  It works great. 

I spent about $70 on the angle unit a couple of years ago, and only used it a few times.  It probably cost me $100 worth of ruined BB ply before I hung it on the wall.  I finally got some value for my money.  I broke down three sheets yesterday with my "modified" FS-KS and the results were awesome.

 

[UCLA Fan]

What if you were to use two Swanson speed squares to set a guide rail for a cut, one on either end of the rail? Would this help reduce the error inherent in using just one square to set the rail?

Hi Sean,

Two speed squares on on each end MIGHT improve the squaring issue. But only if the sheet good edges are truly parallel. Of course using one on each end should revel any significant variance before you cut so it should be a good way to verify the parallel edges then cut away. Hmm Good idea Sean. Overall I still prefer using the parallel method with two 48" rulers and stair gauges. You wind up with a parallel cut that is an excellent reference for squaring and once you set the gauges you can do exact repetitive cuts ad-nauseam ;D

Frank

 

[Sean_C_G]

What if you were to use two Swanson speed squares to set a guide rail for a cut, one on either end of the rail? Would this help reduce the error inherent in using just one square to set the rail?

Hi Sean,

Two speed squares on on each end MIGHT improve the squaring issue. But only if the sheet good edges are truly parallel. Of course using one on each end should revel any significant variance before you cut so it should be a good way to verify the parallel edges then cut away. Hmm Good idea Sean. Overall I still prefer using the parallel method with two 48" rulers and stair gauges. You wind up with a parallel cut that is an excellent reference for squaring and once you set the gauges you can do exact repetitive cuts ad-nauseam ;D

Frank

Hi Frank,

Go Bruins! Thanks for the informative post you made on the 23rd. I got a lot out of it. I see your point about the sheet's edges needing to be parallel; after a night's sleep, I woke up this morning with this realization. I think what I had in mind in my original post was what you articulated nicely for me: that using two squares would hopefully show a variance. I am beginning to understand the parallel method more. I had trouble visualizing it when I first read about it on this forum. But being a novice, I don't mind taking a little extra time initially to ensure parallel. After all, I'll more than make up for the initial time investment by having my cut pieces actually fit! I'm going to do more searches on the method you described. If I have any questions, will be sure to post them. Thanks again.

 

[nickao]

You know I hear about guys making a first cut to fix the edges on ply.

The plywood I get is usually cabinet grade and really, the factory edges are 99% of the time parallel and square with a nice new edge. So much so that I have made a room full of cabinets basing my cuts on the edge of the ply.

Are people getting bad plywood or is the stuff I buy just a better grade? I mean for 150.00 and up for a sheet it better not require me to square it up. Even sheets for 75.00 seem good enough to me.

Or are most talking about a construction grade ply for general carpentry?

Nick

 

[UCLA Fan]

HI Nickao,

I agree that high quality sheet goods tend to have very good edges and I use alot of it. But I also use alot of Home Depot "cabinet grade" imported birch plywood. For about $40 a sheet it is pretty good over all for paint grade or utility type cabinets but the edge are are awful to say the lest. very inconsistent stuff. Thin surface layers and a touch thinner too. So I like to clean up all the edges it saves a lot of frustration. So now it is just part of my routine only takes one cut and I know I am good and as you said at $150 a sheet even one missed cut can add up to a huge loss of money if I have to redo something and eat the cost of a sheet.

Oh and your welcome Sean and as your experience grows remember preparation in planning and execution can lead to huge rewards as the saying goes "failure to plan is planning to fail"

Frank