Repeat cross cuts on long plywood sheets

[Gabriel Marusic]

I'm struggling with making some repeat cross cuts on 70" long sheets of ply for a couple large cabinets and am looking for some ideas based on the tools I have. I initially measured, struck my lines and then did my cross cuts with the track saw but this isn't accurately repeatable and I'm off by almost 2mm on one of my panels which is obviously unacceptable for cabinets. I have a tracksaw, mft table, parallel guides and a table saw but am racking my brain on the right approach. The parallel guides for the track saw don't go to 70" and even if they did I'd be a bit concerned with some wobble at that length. The MFT would be great but my panel is way longer than fence and stop block for repeat cuts. My cabinets are also a bit wider than what is practical to cut on there. I've done it, but I can't latch the track down since my wood is wider than the table and I have to manually square and clamp the track each cut. I watched a video where Peter Millard has a table behind his MFT where he basically temporarily pin nails a stop block to the correct distance and then uses the MFT and track saw to make the repeat cuts. This is probably my most realistic bet though I'd need to make a temporary second table with some saw horses, clamp it all together and hope for no wobble and still fiddle with not being able to latch down the track right.

Hoping for some ideas on a better solution for this. Thanks as always!

[ChrisA Edwards]

I have a MFT and Sawstop, but when I'm trying to crosscut a long length, I revert to my homemade MFT table that just lays on my mobile bench. It could just as easily rest on a couple of 2x4's on saw horses.

This is just a 3/4" sheet of MDF with bench dog holes drilled in using the Parf II system. This gives me positive stops and perfect 90 degree crosscutting.

https://hosting.photobucket.com/albums/i452/cedwards874/Woodworking/Bench%20Dog%20Top/.highres/BenchDogTop2_zpsvpkrlszb.jpg


https://hosting.photobucket.com/albums/i452/cedwards874/Woodworking/Bench%20Dog%20Top/.highres/BenchDogTop3_zpsczfeejs4.jpg

https://hosting.photobucket.com/albums/i452/cedwards874/Woodworking/Bench%20Dog%20Top/.highres/BDTInUse1_zpsaqxwcnzc.jpg

[Gabriel Marusic]

I have a MFT and Sawstop, but when I'm trying to crosscut a long length, I revert to my homemade MFT table that just lays on my mobile bench. It could just as easily rest on a couple of 2x4's on saw horses.

This is just a 3/4" sheet of MDF with bench dog holes drilled in using the Parf II system. This gives me positive stops and perfect 90 degree crosscutting.


That's pretty sweet, do you have a CNC or were you able to get someone to make the top for you?

[ChrisA Edwards]

The holes were drilled using the (Peter ) Parf System Mark II


https://tsoproducts.com/accessories/ujk-technology-parf-guide-system-mark-ii/


This is the original system, but it's pretty much the same.

https://www.youtube.com/watch?v=Xi9raT8gyEE

[Ole Anderson]

Rough cut with the tracksaw, finish cut on your TS. Pretty common. Do your finish crosscuts with a sled tuned to 90 degrees.

[Gabriel Marusic]

Rough cut with the tracksaw, finish cut on your TS. Pretty common. Do your finish crosscuts with a sled tuned to 90 degrees.

I thought about a sled, but I'd need a pretty massive one to cross cut a panel that is over 70".

[Thomas McCurnin]

Story Stick is what I use. Every measurement is on the stick(s).

[Paul F Franklin]

I've made quick and dirty purpose built parallel guides when I need to do multiples with the track saw:

Here's the idea, you make two of these (of whatever length you need):

439805

And here's how I use them to set the track (pic just shows one, but I use one at each end of the track). Once the track is positioned, you can clamp if you want to be really sure it doesn't move.

439808

I have the double sided dewalt track, so I make sure to register off the metal part of the track, not the rubber strip. It's no issue with other brands of track.

[Jim Becker]

Help me out here as I'm apparently missing something in my brain...how wide is the crosscut for those 70" long panels? 48"? 36"? Are they wider than your MFT can support for cross cutting with the MFT setup? If so, you can create a measuring stick with a tee (like a story stick with a stop) to index to end of the panel that you then can use for marking the dimensions you need to lay down the line for your track since you mention that this is a repetitive action. That should be accurate if the panels are square and is much better than using a tape. No way should you be getting up to a 2mm deviation.

[Kevin Jenness]

I think Paul Franklin has the right idea- obviously you have to square up one end of the panel first. Two story poles gauging from the squared end to the back of the saw track. I'm glad I have a sliding table saw.

[Gabriel Marusic]

Help me out here as I'm apparently missing something in my brain...how wide is the crosscut for those 70" long panels? 48"? 36"? Are they wider than your MFT can support for cross cutting with the MFT setup? If so, you can create a measuring stick with a tee (like a story stick with a stop) to index to end of the panel that you then can use for marking the dimensions you need to lay down the line for your track since you mention that this is a repetitive action. That should be accurate if the panels are square and is much better than using a tape. No way should you be getting up to a 2mm deviation.

They're 27" wide so I'm not able to close the track on the latch if that makes sense. On my initial cuts I put the track down on the plywood with it still being connected in the back and used a triangle to square the track to the fence and then locked the track down with a clamp underneath. Really not an ideal setup and probably contributing to the error. I think even if i get a good line across the board it's still going to be tricky for me to line up because of the track locking issue and fiddling with squaring vs the fence. Might be better for me to take the fence off the MFT all together and do it like you suggested.

[Gabriel Marusic]

I've made quick and dirty purpose built parallel guides when I need to do multiples with the track saw:

Here's the idea, you make two of these (of whatever length you need):

439805

And here's how I use them to set the track (pic just shows one, but I use one at each end of the track). Once the track is positioned, you can clamp if you want to be really sure it doesn't move.

439808

I have the double sided dewalt track, so I make sure to register off the metal part of the track, not the rubber strip. It's no issue with other brands of track.

This is a great idea!

[Bruce Wrenn]

I've made quick and dirty purpose built parallel guides when I need to do multiples with the track saw:

Here's the idea, you make two of these (of whatever length you need):

439805

And here's how I use them to set the track (pic just shows one, but I use one at each end of the track). Once the track is positioned, you can clamp if you want to be really sure it doesn't move.

439808

I have the double sided dewalt track, so I make sure to register off the metal part of the track, not the rubber strip. It's no issue with other brands of track.


Make the one guide, then rip it in half length wise, then you have two that are the exact same length. I use a shop made cutting guide for circular saw, but it's only eight feet long. When ripping down 9 or 10' melamine sheets, I use the guide sticks to advance the cutting guide. No measuring, or guessing, after initial set up.

[Jim Matthews]

I've made quick and dirty purpose built parallel guides when I need to do multiples with the track saw:


439805



439808



That's clever.

Kudos

[Jim Becker]

Any time that repeatability is essential, some kind of physical stop or fixed measuring device (combined in the photos for the previous few post) is the way to do. Whether it physically holds the track or just provides the line, the results should be "pretty darn accurate".

[Mark Gibney]

I find the TSO guide attached to the Festool track to give me very accurate 90° cuts.
If you want to cut several different panels to the same lenghts then you might want to make a spacer that will help you place the TSO + track exactly where you want it.

439828

There are other brands of essentially the same product available, but this is the one I have.
The reference edge of the TSO that butts up against the plywood is of course shorter than the track, so you need to be careful to have it sit tightly, but once you do it works as advertised.

https://tsoproducts.com/tso-guide-rail-squares/grs-16-guide-rail-square/

[Gabriel Marusic]

I find the TSO guide attached to the Festool track to give me very accurate 90° cuts.
If you want to cut several different panels to the same lenghts then you might want to make a spacer that will help you place the TSO + track exactly where you want it.

439828

There are other brands of essentially the same product available, but this is the one I have.
The reference edge of the TSO that butts up against the plywood is of course shorter than the track, so you need to be careful to have it sit tightly, but once you do it works as advertised.

https://tsoproducts.com/tso-guide-rail-squares/grs-16-guide-rail-square/

I love TSO. I actually have this along with their PTR triangle and both are awesome. I used it today to build the jig like others suggested and it worked really well. Really wish I have their parallel guide setup instead of the woodpeckers one. I'd end up losing too much to make the switch so I'm stuck.

[Gabriel Marusic]

Thank you all as always for the suggestions and help. To close the loop here, I made a jig like Paul suggested and it worked perfectly. Also turns out that one of the panels I was cutting wasn't actually square which compounded the issue. I've now switched to 75% metric and one of those flat fastcap tape measures which has made validating my cuts so much easier.

[Jim Dwight]

Looks like the issue is solved but I will offer my comment anyway. My assembly table/outfeed table has 20mm holes that are almost square (bored with pegboard and a router base that indexes off it). I thought it was square but it is a little off so I put a screw adjust on the fence I use to have stops so I can get it exactly square.

For bigger pieces I use a plywood square with a fence if that helps. It is 18 inches so I can mark a pretty wide panel from one side. I started using a 0.5mm pencil after getting a track saw. The width of my line was a source of inaccuracy. I am pretty sure I could just mark and cut to less than 1mm variation.

But for repeatable cuts, I use a jig like the suggested one except it has a dado to go over the guide rib of my DeWalt tracks. I use my long square sometimes on the edge of the track but it bugs me that it is soft on the DeWalt so it's a bit flexible. The rib is not. I have a movable stop with a hairline indicator of the length. So I can set the stop, and position both ends of the track. I can do it the same for each cut. I have one of these "track positioning guides" that is for when the piece you want is under the track and one for when it is away from the track. I like these better than the home made parallel guide I have (no commercial ones for DeWalt).