Mitered plywood cabinet corners with parallel guides

[matthew75]

I'm looking to build some 45 degree mitered corner 3/4" plywood boxes and want to use my tracksaw to do so. I do not own the parallel guides yet and have looked at the ones from festool, and Seneca woodworking, but trying to figure out if I can cut miters on both ends with this method? This is for a furniture grade cabinet and is cherry veneered ply so I need measurements and angles to be exact. I know I can cut one end on a 45 with no problem, but will the parallel guides register off a mitered end to cut the other 45? I do not own a MFT table which possibly could help but that's not in the budget right now. Thanks for any advice or tips you can give me on doing this.

 

[jools]

Take care not to crush the mitred edge with the stops. I've used this method when boxing in pipes so only three sides. All I can say is you have to be ultra accurate with setup and cutting technique to get acceptable results.

 

[MGB]

You could build a crosscutting jig without an mft. Just need a fence attached to a half sheet of plywood. With some stop blocks for your track to register against.

The parrallel guides are nice for rips of course.

 

[Tinker]

You could build a crosscutting jig without an mft. Just need a fence attached to a half sheet of plywood. With some stop blocks for your track to register against.

The parrallel guides are nice for rips of course.

I don't understand how parallel guides are used for cutting miters.
I bought the Festoy p.guides and they are something of a TA to use.
I later bought RMW's Rip Guides for a whole lot less and they really work great.
Go that route and you could go along way towards saving for that MFT table
Tinker

 

[benwheeler]

I've done a few jobs like this, and am also unsure why you'd use parallel guides. Just use the biggest and most accurate square you have to set up the track.

As you say, the angles need to be exact. If you've done this successfully before, no problem. If not, here's what I'd say from my experience:

- Just because your saw indicates that it's at 45° doesn't make it so. Do test cuts and ensure it will work.

- The track needs to be well clamped, as well as supported well past the start and end of the cut. Otherwise, the track will droop and affect the cut.

- You'll need to firmly hold the saw on the rail will your spare hand. Also, don't forget that the underside of the track has slightly spongy rubber attached, so if you change the way you hold the saw, this could affect the angle.

By the way, if you did use parallel guides, this could potentially multiply any error.

Good luck!

 

[Michael Kellough]

This is a job for a lock-miter router bit. It's very difficult to cut sufficiently good miters in easily worked material like MDF but it's extremely difficult working with plywood (which is much less flat than MDF).

Then, you'll have a tough time keeping the miters closed during glue-up. Lock-miter router bit solve all those problems but it does have a learning curve.

 

[Birdhunter]

I've done this type of box lots of times, but always using a table saw. I use a spline to align and strengthen the joint. Trying to make this cut with a track saw boggles my mind. Please let us know how you end up doing it.

 

[roblg3]

I like the idea of the router bit!  It doesn't need to be a lock miter, but it won't hurt if it was!  Use the parallel guides to cut the exact boxes, then a router table to cut the angles. If you have a domino you can then do that on the mitred edges which creates a "lock" of their own. Lock miter bits are tricky without practice with the set up.
It's been nearly impossible for me to consistently cut perfect miters over distances , like a long plywood rip. There's always some small wiggle that ruins the meet up point. It's more work to use "additional" processes like cutting square and then going to the router, but my chances of succeeding and creating a better project significantly increase when I do only 1 technique per operation.

 

[tjbnwi]

If you're going to use a lock miter bit get the Infinity Lock Miter jig. If you don't have a lock miter bit the Infinity bit is a very nice one.
http://www.infinitytools.com/2-Pc-Lock-Miter-Master-Jig-Set-For-3_8-1-3_16-Stock/productinfo/00-LMM/

Tom

 

[ear3]

The Seneca Guides will work fine for this operation, but not the Festool ones.  I haven't used them specifically for a box, but I did make a large octagonal pillar casing using them and they worked great (used dominoes for the joints, though).  There's a good thread on the FOG about proper setup courtesy of [member=18283]zxcv[/member] , which will alleviate some of the concerns others have expressed about using the guides:
http://festoolownersgroup.com/festool-how-to/rule-with-stop-to-set-parallel-guides/
 

I'm looking to build some 45 degree mitered corner 3/4" plywood boxes and want to use my tracksaw to do so. I do not own the parallel guides yet and have looked at the ones from festool, and Seneca woodworking, but trying to figure out if I can cut miters on both ends with this method? This is for a furniture grade cabinet and is cherry veneered ply so I need measurements and angles to be exact. I know I can cut one end on a 45 with no problem, but will the parallel guides register off a mitered end to cut the other 45? I do not own a MFT table which possibly could help but that's not in the budget right now. Thanks for any advice or tips you can give me on doing this.