Cutting plywood

[cbrown]

I have a 24" x 25" piece of 3/4" birch plywood that I want to cut down to 21" x 25" and then cut 3 6.5" x 21" strips plus 2 dividing the remainder. What is the best way of doing this on a stock BT3100 (i.e., no left-and-right miter slot tables and crosscut sled, no front-edge fence for the SMT)? I am aware of dire warnings against trying to cut a nearly square piece using the rip fence, and it is too wide to use the SMT. Or is the best thing to use a circular saw and a straight edge--a little disappointing, since it seems like something the BT should be able to handle?

Thanks,

Christopher

[bigsteel15]

I have a 24" x 25" piece of 3/4" birch plywood that I want to cut down to 21" x 25" and then cut 3 6.5" x 21" strips plus 2 dividing the remainder. What is the best way of doing this on a stock BT3100 (i.e., no left-and-right miter slot tables and crosscut sled, no front-edge fence for the SMT)? I am aware of dire warnings against trying to cut a nearly square piece using the rip fence, and it is too wide to use the SMT. Or is the best thing to use a circular saw and a straight edge--a little disappointing, since it seems like something the BT should be able to handle?

Thanks,

Christopher

Why cut it down to 21" first? Skip to step 2
Step 1: set your rip fence to 21", measure and then cut the 24" down to 21".
Step 2: set and measure rip fence to 6.5" then rip your 3 strips
Step 3: measure remainder (should be ~5-1/4") and set fence to cut in half
Step 4: open a cold one

[LCHIEN]

I have a 24" x 25" piece of 3/4" birch plywood that I want to cut down to 21" x 25" and then cut 3 6.5" x 21" strips plus 2 dividing the remainder. What is the best way of doing this on a stock BT3100 (i.e., no left-and-right miter slot tables and crosscut sled, no front-edge fence for the SMT)? I am aware of dire warnings against trying to cut a nearly square piece using the rip fence, and it is too wide to use the SMT. Or is the best thing to use a circular saw and a straight edge--a little disappointing, since it seems like something the BT should be able to handle?

Thanks,

Christopher

well, first the nearly square danger is mostly for sizes around 3-4-5 inches.

I would have no hesitation in cutting like this:
trim the 24" dimension to 21"; I might well do this by cutting off the ~3" and leaving 21" just so I won't have to rearrange the rails...
The the 3"x25" cutoff is between the blade and fence, its long and not a bad kickback candidate.
And use the rip fence, 25" along the rip fence is plenty.
(You can also set the rip fence 21" from the blade and have the good piece of wood between the blade and fence, if you wish. It's too big to make a bad kickback)

Then I'd set the rip fence 6.5" from the blade and run the 21" edge along the rip fence three times to get your three pieces.

Then adjust the rip fence and divide the remaining piece.
If the two pieces being equally divided is more important than the actual dimension, then I'd set the rip fence to a hair less than half and rip one pieces, then rip the other to match, assuring identical widths.


Note: you should not be afraid of cutting small square pieces. When I do, I make a note tha this is the size/proportion that has a higher liklihood of kicking back, use extra precautions, and make sure I use a shoe rather than just a push stick so that I bear down with sufficient force the whole way through on the small piece so that it cannot lift. KNowledge and appropriate technique is the key. A safe push shoe can be simply a 6" 2x4 on edge with a little hook on the end to push the rear of the workpiece through.

[cbrown]

Thanks--I am posting the results over on the project-related discussion forum.

http://www.bt3central.com/showthread...880#post196880

[davidtu]

I've had to do a lot of cuts like this and was convinced I should not use the rip fence to do it because the piece was rectangular with long end along the would-be rip fence (ie. if I used it).

What exactly are a good set of rules (or source to read them) for when to use the rip fence vs. when to use the SMT? Do the rules change depending on whether its plywood or MDF or regular stock?

Also, it seemed like the general advice was that the smaller cut-off should not be between the blade and the fence. How can I tell when this rule does not apply?

Or maybe I should be asking for the principles involved rather than a set of rules... whatever you think would help.

Thanks,
David

[LCHIEN]

I've had to do a lot of cuts like this and was convinced I should not use the rip fence to do it because the piece was rectangular with long end along the would-be rip fence (ie. if I used it).

What exactly are a good set of rules (or source to read them) for when to use the rip fence vs. when to use the SMT? Do the rules change depending on whether its plywood or MDF or regular stock?

Also, it seemed like the general advice was that the smaller cut-off should not be between the blade and the fence. How can I tell when this rule does not apply?

Or maybe I should be asking for the principles involved rather than a set of rules... whatever you think would help.

Thanks,
David

I don't know that there are published rules but I feel that if there is an edge long enough to run against the rip fence and the piece is easy to guide where it won't rack (Twist away from the rip fence) then its safe.
If you can't easily control the piece and it twists then it can get caught and something bad may happen.

If you need, get some roller stands, outfeed tables, infeed tables whatever to make the piece controllable. If its 8 feet long and 1 foot wide I'd not be comfortable controlling the foot wide edge along the rip fence. but I'm sure I could handle a 1 foot wide edge against the rip fence with a three-foot piece of plywood.

Like I mentioned before the really nasty kickback is when you have pieces around 3-4-5" on a side and a near-square format between the fence and blade. Something like 4.5" x 4" ought to send alarm bells ringing in your head to be real careful.

It really makes no difference the type of wood, whether its a glued up panel or plywood or MDF.

I use the SMT if the edge is too narrow to run along the rip fence and keep it from twisting. Like a 1" x 12" piece the 1" edge is not long enough to control
6"x12 is definately controllable. Some where in bewteen is no mans land - depends what you feel you can control.
I use the SMT as an alternative as long as I can control it without racking again, AND it fits inthe space betweenthe fence and the blade (corsscut capacity). There's some ways around this in the BT3 FAQ.

[scoutmgr]

What about 8'X4'

This is an interesting topic and one that I have been wondering myself. Up to this point, all my woodworking had been of the "rougher" type with smaller pieces, 2 x 4's, and pieces of wood that did not required perfect dimensions.

I finally worked up the courage to get a couple more tools I needed (router mainly) to do some more "finer" woodworking. I'm going to get cabinet-grade plywood ... the one that comes in 3/4" x 8' x 4' to do my projects. I have a BT3100 with the stock blade.

Now, as I'm planning the different size pieces I will need to make out of the variouys 8' x 4' I'll be buying, I'm sitting here thinking ... how do begin to make the cuts? Some of the boards will be used to create larger pieces (i.e. 63" x 36") and others will be a bunch of smaller pieces (ala 12" x 15") ... but the point is still the same.

This is related to this topic because I'm not sure when you throw it on the BT3100 and when you pull out the old Circular Saw ... so I was kind of like Davidtu .. wondering what most people do and how they have addressed safety issues.

Any tips would be grealy appreciated.

[John Hunter]

This is an interesting topic and one that I have been wondering myself. Up to this point, all my woodworking had been of the "rougher" type with smaller pieces, 2 x 4's, and pieces of wood that did not required perfect dimensions.

I finally worked up the courage to get a couple more tools I needed (router mainly) to do some more "finer" woodworking. I'm going to get cabinet-grade plywood ... the one that comes in 3/4" x 8' x 4' to do my projects. I have a BT3100 with the stock blade.

Now, as I'm planning the different size pieces I will need to make out of the variouys 8' x 4' I'll be buying, I'm sitting here thinking ... how do begin to make the cuts? Some of the boards will be used to create larger pieces (i.e. 63" x 36") and others will be a bunch of smaller pieces (ala 12" x 15") ... but the point is still the same.

This is related to this topic because I'm not sure when you throw it on the BT3100 and when you pull out the old Circular Saw ... so I was kind of like Davidtu .. wondering what most people do and how they have addressed safety issues.

Any tips would be grealy appreciated.

When dealing with full sheets I like to cut them down to size on saw horses using my Ryobi 18 Volt circular saw and an aluminum guide. I can handle a half sheet on the BT3100 but full sheets are a bit heavy.

[LCHIEN]

When dealing with full sheets I like to cut them down to size on saw horses using my Ryobi 18 Volt circular saw and an aluminum guide. I can handle a half sheet on the BT3100 but full sheets are a bit heavy.

Roger that but I use a corded circular saw.

[Deadhead]

Roger that but I use a corded circular saw.

Lately I've been using my jigsaw and a guide to cut down plywood sheets. It doesn't coat everything within a 10-foot radius with dust like my old circular saw does.

[dwk]

I faced this situation with the BT3k for the first time last night - had to rip a 4x8 sheet of 1/2 ply into 6.5" widths. I started prepping for trying to handle the entire sheet, and very quickly came to the conclusion that it's a no-go on the stock saw. I just can't see how you can entertain the idea of working a full sheet without a greatly expanded working surface. Most of the mobile cabinets I've seen are good in the width and outfeed areas, but I'd also want an improved infeed arrangement - otherwise you're supporting too much weight for too long to get a precise feed IMHO.
I sliced the sheet roughtly in half (20/28 split) with the circular saw and cutting guide, and after that was able to rip the smaller pieces on the BT3k pretty easily.