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cross-cutting large plywood pieces on table saw fence

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Forum topic by ramblinwreck posted 10-12-2018 12:00 PM 1827 views 0 times favorited 16 replies Add to Favorites Watch
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ramblinwreck

13 posts in 260 days


10-12-2018 12:00 PM

Hi.

I understand that cross-cutting ‘wide’ (wider than long) pieces on the table saw needs to be done with a miter gauge or cross-cut sled, and NOT the rip fence, due to the lever action created which can pinch the blade and cause dangerous kickback.

However, I have noticed many seasoned woodworkers cross-cutting against the fence on ‘large’ plywood pieces that are indeed wider than they are long. One random example: https://imgur.com/a/psAmrgh . I suppose this piece is too large to cut with a miter gauge, and maybe even for a cross-cut sled (well, it would be for mine). Is this okay?

I’ve not seen this particular usage addressed in any educational videos or discussions that I’ve seen. Presumably there must be a point when the workpiece length (registered against the fence) reaches a certain dimension, that helps to stabilize the workpiece despite the lever introduced by the width of the piece?

Can you guys comment on this, or point me to some materials/video/etc that discuss this?

Thanks!
Chris

-- Chris


16 replies so far

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jmos

902 posts in 2567 days


#1 posted 10-12-2018 12:14 PM

You are correct, it’s not a good idea to cut something that is wider than it is long against the rip fence, but you need to look at the relative dimensions. It all comes down to how sure you are you can keep the reference edge against the fence while you push it through. My comfort level in doing this may be more or less than yours. Like many machine operations, if you’re not comfortable with it, don’t do it. I don’t think there is a hard rule for when this goes from OK to dangerous.

-- John

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lumbering_on

572 posts in 687 days


#2 posted 10-12-2018 01:04 PM

I have a track saw now, but before that I used to do a cross cut on large plywood all the time. However, I took precautions such as making sure the cut wasn’t less than 12”, and that the cutoff was supported by the table saw and wouldn’t fall after the cut. I also used Board Buddies to prevent any chance of kickback and to maintain down pressure on the board. I also do it on a 1.5 hp saw, which is more likely to stall then kickback a large sheet of plywood.

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bondogaposis

5086 posts in 2548 days


#3 posted 10-12-2018 01:11 PM

It is not too bad to do if the piece in question is close to square. If you look at the picture, the piece is rectangular, but the offcut portion is irrelevant, it is the portion between the blade and the fence that matters and that is nearly square. You have to be very careful when pushing it through not to put any kind of twisting pressure on the board, tight to fence and straight through. Also the fence must be properly aligned.

-- Bondo Gaposis

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Andre

2198 posts in 2003 days


#4 posted 10-12-2018 02:00 PM

Good rule to live by, if it feels wrong, it probably is! But seeing he is using a Saw stop the safest Saw in the World what can go wrong?LOL Remember there is no cure for stupidity.

-- Lifting one end of the plank.

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splintergroup

2421 posts in 1419 days


#5 posted 10-12-2018 02:41 PM

My personal limit is when the workpiece is less than about 2x the exposed width of the blade. If it is not square or less at this point, I’ll (usually subconsciously) figure out another plan of action. The picture you show has the work piece at about 4-5x the width of the exposed blade.

Alternatively, He could cut the short end against the fence.

It’s all about control. A large piece like that has plenty of surface area to place your hand as added control and guidance. The workpiece is much wider than the exposed blade which means the saw blade is pushing down on the front while is is trying to lift in the rear (kickback). There is more wood mass and length to counter this torque. As stated, the workpiece is almost square so there is better control of the torque trying to twist the board in a circle.

Andre has a excellent point. If it feels wrong, it probably is. That is your spidey sense telling you that you are not ready for this cut. With more experience, you’ll get a better idea of good/bad, the best thing is you usually start off on the safe side and gradually move your comfort zone out.

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ramblinwreck

13 posts in 260 days


#6 posted 10-12-2018 04:28 PM

Thank you all, particularly Bondo:


It is not too bad to do if the piece in question is close to square. If you look at the picture, the piece is rectangular, but the offcut portion is irrelevant, it is the portion between the blade and the fence that matters and that is nearly square.

So let’s look at a specific example which prompted this question. I’ve got a 16”x32” piece of plywood that i need to cut some drawer faces from. These drawer faces are 14-1/2” wide (i’ll just make a full 16” cut and trim them later). The faces are roughly 5” to 8” tall.

See here: https://imgur.com/a/aKfIRjW

Any problem with me cutting these as shown? For example, in all cases I’ll have a full 16” registered against the fence as I make the cut, and the distance between the blade and the fence will be 8 inches at the most. From what I understand here, this shouldn’t be any problem as long as I’m careful pushing it through.

I could probably make these 16” cuts on my crosscut sled (Incra Miter Express), but I’d prefer to use the fence for these parallel cuts if possible.

-- Chris

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JohnMcClure

310 posts in 838 days


#7 posted 10-12-2018 04:35 PM

What you are planning sounds safe. But it’s good you asked first.
I make a simple push block to keep pressure in the right places, but hand clear of blade, in your exact situation. Don’t have a pic, but the first item in this article is a good example. Basically a handle with a cleat on it
https://www.google.com/amp/s/www.popularmechanics.com/home/tools/how-to/gmp2615/7-diy-push-sticks/

Be safe!

-- I'd rather be a hammer than a nail

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splintergroup

2421 posts in 1419 days


#8 posted 10-12-2018 06:26 PM

Your plan looks fine safety wise. I’d cut the pieces a tad (1/8”) taller than final dimension (if you have the excess material). This way you can run them through afterwards on both sides for a clean up pass. Cutting sequenced pieces off a larger sheet the way you have shown often leaves a slight bump on the trailing edge of the “waste” side of the cut as it rotates slightly at the end of the pass.

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ArtMann

1135 posts in 1013 days


#9 posted 10-13-2018 02:08 AM

I would do it without hesitation but I have been doing this a long time. Just be sure the material rides snug against the fence at all times and you will be fine.

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TheFridge

10699 posts in 1683 days


#10 posted 10-13-2018 03:10 AM

I am a safety rebel.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

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waho6o9

8516 posts in 2774 days


#11 posted 10-13-2018 03:18 AM

“Is this okay?”

No

Hell no

Don’t even think about it no.

With all due respect Sir.

View BlazerGator's profile

BlazerGator

25 posts in 1386 days


#12 posted 10-13-2018 04:40 AM



So let’s look at a specific example which prompted this question. I’ve got a 16”x32” piece of plywood that i need to cut some drawer faces from. These drawer faces are 14-1/2” wide (i’ll just make a full 16” cut and trim them later). The faces are roughly 5” to 8” tall.

If I had the same concern, I’d probably cut the piece roughly in half (whatever fits your cutting layout) and then cut the drawer faces from the smaller blanks. For an extra measure, I’d oversize them a bit and cut to final size later, as you described you’ll be doing with the other dimension.

-- Blaze

View NoSpace's profile

NoSpace

140 posts in 1438 days


#13 posted 10-13-2018 06:22 AM

As someone else said the piece in the picture is so large that it’s hardly going to be unstable. Also, plywood is more stable and easier to cut than hardwood. With plywood, if i have 16” against the fence, and conscientiously supporting it against the fence through the cut I wouldn’t be too worried. Wouldn’t do it with 3/4” maple. I do things like lower the blade all the way down, and practice the motion of the cut to see how it feels going along the fence for larger pieces. But a lot is having a feel for the saw. When I got my TS, as a newbie, I read the manual twice, and built a crosscut sled with my miter saw before I ever even turned on my TS. I never used the miter guage probably for the first year i had it.

I prefer to use a sled or more recently, I built a slider mechanism for crosscutting and breaking down larger plywood pieces so I don’t have to use my circular saw anymore. If the concern is getting pieces the same size, then I use the fence to set up the cut with the slider/sled, and then move the fence before cutting.

View therealSteveN's profile

therealSteveN

1674 posts in 771 days


#14 posted 10-13-2018 06:38 AM

So let s look at a specific example which prompted this question. I ve got a 16”x32” piece of plywood that i need to cut some drawer faces from. These drawer faces are 14-1/2” wide (i ll just make a full 16” cut and trim them later). The faces are roughly 5” to 8” tall.

If I had the same concern, I d probably cut the piece roughly in half (whatever fits your cutting layout) and then cut the drawer faces from the smaller blanks. For an extra measure, I d oversize them a bit and cut to final size later, as you described you ll be doing with the other dimension.

- BlazerGator

Yes, when I looked at your second example pic I immediately thought if your safety concern was the amount over a certain %, why not go close to 50/50, and then cut what is left the widths you want, makes 3 cuts.

Of course if anything there makes you feel uncomfortable, there are other ways to skin this cat. A track saw was invented for such work, before that guys used a circular saw and a ho made cutting jig to place on a cut line, and cutting into rigid foam, good face down. If concerned about ragged cuts then putting a strip of masking tape on the cut line, any of them can give you excellent results.

-- Think safe, be safe

View ramblinwreck's profile

ramblinwreck

13 posts in 260 days


#15 posted 10-13-2018 12:33 PM

Thanks all for all the replies, I have learned some things here.

I had considered cutting roughly in half or thirds (e.g. on my cross-cut sled) which would give me a skinnier piece to rip, and then trim afterward. Sure, that would work. But I was curious if it is reasonable to cut using the rip fence only. The reasons are three-fold:

1. Maintaining the continuous grain (there is a bit on this particular piece of plywood) on the drawer faces. Cutting as shown in the second picture achieves that best.

2. Efficiency. Not having to swap to my cross-cut sled for this kind of cut makes things faster. I have an Incra Miter Express, and while it does work great (no complaints), it does require getting out a hex key to install the fixed panel, and so does take a few minutes.

3. Minimizing waste. Not a problem on this particular piece, but could be on others.

As Bondo pointed out, the long vs short dimension ‘formula’ for when to not use the fence involves the distance between the fence and the blade, not the total width of the workpiece. This is a subtle but important distinction that I did not realize initially. And I have confirmed this with other sources (e.g. see time 2:06 in this video: https://youtu.be/F0jbg9LuDsc?t=126). On that basis, my workpiece cuts should be OK, as my against the fence dimension is at least twice the distance between the fence and blade. In fact, at 2:24 in the same video George shows a cut with proportions very similar to the one I wish to make: https://youtu.be/F0jbg9LuDsc?t=144.

This particular cut doesn’t necessarily make me ‘uncomfortable’, I was just exercising an abundance of caution before approaching it. :)

-- Chris

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