# Guidelines for Cutting Baltic Birch Ply



## breakfastchef (Jan 14, 2008)

I am dropping some big bucks on a couple of sheets of baltic birch plywood to build a pair of loudspeakers. I want to make sure I don't foul up any of the cuts with the objective of being as accurate as humanly possible (i.e. straight and square). The speaker cabinet finished dimensions will be 46"H x 16"W x 13"D.

My Dewalt jobsite saw is really too small to handle 5'X5' panels for the initial cuts which leaves me with my circular saw as the main cutting tool. I have an extruded aluminum saw guide called a Pro Edge Model 900 (Empire Level Co.), and four adjustable rollers stands for use as infeed/outfeed support for the table saw. I will use biscuits for the butt joints.

What type of saw blade should I use?
Should I cut a little oversize or shoot for the final size?
Should I score the cutline to prevent tearout?
Should I measure two times ot three times before making a cut?

Any tips from the cabinet builders would be greatly appreciated.


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## bradnailer (Nov 11, 2008)

I've never seen any reason to cut oversize then cut down to size. So...

Use a fine cut saw blade that you know is sharp. Not sure about the blade count on circular saw blades though.
Since you are using a circular saw, the finished side should be on the bottom when you cut.
I normally scribe two lines, one for each side of my saw blade.
I never measure more than once.... or twice.. or three times.


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## 97phatlady (Aug 16, 2008)

Once you have your guide in place put blue painters tape or masking tape over your cut-line, both sides. It will significantly reduce splintering.


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## mmwood_1 (Oct 24, 2007)

breakfastchef,

Okay, I work with BB a fair amount. I usually use a table saw with roller stands to cut the pieces. With a circular saw, here is what I would recommend. Don't use a thin kerf blade, they wobble too much and you will not get a smooth cut. Unless you have a pretty good one. I use Matsu****a thin kerfs, at about $30 for a 7 1/4" blade and they work ok. 40 teeth, I think. Otherwise, go for a 1/8" kerf, carbide tipped blade.

I have read all my life of people using tape to prevent tearout. I've tried it and my experience is that the force of the blade pulling upward against the wood is far stronger than the tape, and it doesn't accomplish squat. But that's my experience. I've found that a good quality blade, run slowly against an accurately positioned straight edge will give you a decent cut.

As for how many times you should measure, that's a pretty funny question. It's completely irrelevant how many times you measure. What IS RELEVANT is measuring ACCURATELY. However many times THAT takes is how many times you should measure.


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## 97phatlady (Aug 16, 2008)

Gotta disagree, bro. Taping has ALWAYS worked for me.


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## GeorgeC (Jul 30, 2008)

If it was my expensive wood and I wanted a good cut, then I would use the circular saw to cut slightly oversize. I would then go to the table saw for the final cut. More work? Yes!! But, in my opinion it is worth it.

Even 1/4 inch oversize is good as long as you have one good edge to work off of.

G


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## Tony B (Jul 30, 2008)

*Given your situation.....*



GeorgeC said:


> If it was my expensive wood and I wanted a good cut, then I would use the circular saw to cut slightly oversize. I would then go to the table saw for the final cut. More work? Yes!! But, in my opinion it is worth it.
> 
> Even 1/4 inch oversize is good as long as you have one good edge to work off of.
> 
> G


what he said


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## toddj99 (Jan 1, 2008)

My TS is also to small to handle large sheets of ply so I'll use my circular saw to cut them down to manageable size. If splintering is a projected problem, I'll cut to slightly oversize (1/8") them use a straightedge similar to the one you have layed on the desired cutline and trim it back with a router and a flush trim bit with the bearing riding on the straightedge. Produces a nice edge with no splintering. I always measure more than once. To many times I've caught myself "looking at 22 1/8" " when I was actually looking at 23 1/8" or something to that effect. I live by the "measure twice-cut once" rule of thumb. A higher tooth count blade, on either saw, produces a finer cut. Plywood cuts - good face up on a TS, good face down when using a circular saw.


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## red (Sep 30, 2008)

GeorgeC said:


> If it was my expensive wood and I wanted a good cut, then I would use the circular saw to cut slightly oversize. I would then go to the table saw for the final cut. More work? Yes!! But, in my opinion it is worth it.
> 
> Even 1/4 inch oversize is good as long as you have one good edge to work off of.
> 
> G


 
Agreed 110%. Red


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## breakfastchef (Jan 14, 2008)

Thanks all. Keep the comments coming. I will be tackling this project the second week of December. As to measure twice and cut once...I have been woefully guilty of measuring three times, cutting onc and running to Home Depot for more material. Haha.


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## allthunbs (May 14, 2008)

breakfastchef said:


> Thanks all. Keep the comments coming. I will be tackling this project the second week of December. As to measure twice and cut once...I have been woefully guilty of measuring three times, cutting onc and running to Home Depot for more material. Haha.


Ok, you asked for it. You ain't gonna get this one from HD. Go here: http://www.leevalley.com/wood/page.aspx?c=1&p=53825&cat=1,42936,50298&ap=1

I don't know if this is available anywhere else. Oops I just checked Rockler. Where do you get reasonablly accurate rules in the US? I thought Rockler would have some.

I'm sorry if I offended anyone. I'm really picky about rules. I have one that's about 70 years old and it's bang on accurate. I bought a metre stick made of stainless and it cost me bucks. It was out 1/4" in 12". Since then, I actually go into the store with one of my "trusted" rules if I'm going to buy a new one. Most of the time I leave the store disappointed. I'll only buy ones that actually state their accuracy on the package. Even then I'll test it before I buy it. 

This is part of my idiot proofing system. First, chose your ruler. Don't change rules in mid project. I mark on the plan which ruler I'm using and I stick with it to the very end. 

_Never_ use a tape measure unless you know exactly how much it is out and you're prepared to compensate _all_ of the time. If you start at the 1" mark you're introducing an error. At some point you'll forget and use the end of the tape, or you'll miscalculate the actual measurement.

Always measure from a fresh, clean, dressed edge with no obstructions. When in doubt, use a "T" square.

I have ruler "families" that I will "allow" to be interchanged but I will never mix families. I have 1 x 18", 1 x 24", 1 x 48" - I can't find a 36" for this family. I also have 1 x 50cm and 1 x 100 cm. I usually convert everything to Imperial measure. I can't find a 2 metre rule that's reasonably accurate. The scrap rules I can usually use as straight edges.

I consult my plan and set my ruler stop (see above.) Then, I go to another piece that I've already cut to ensure the accuracy. It doesn't have to be exact but it does have to be relative. i.e. this piece is 2" shorter than that one, when I compare the measurement, it better be 2". Once I've accomplished this correctly, I butt the ruler stop up against the edge of the piece I'm cutting and using my striking knife (also Lee Valley) I use the end of the rule to cut/mark the workpiece. If this is a table saw operation or some other tool where I can use a jig, I use the ruler stop to set the jig. However, I do like one of the instructions above where he marks the width of the saw blade as part of his measuring operation. Like that you can quickly and easily see if you're out even the slightest bit. I always mark closest to where the cut is going to start.

I'm going to modify this by adding, using my 1/8" setup block I'll add a second line to indicate where the saw blade should go. I'll mark just that area with a bit of a pencil line.

http://www.leevalley.com/wood/page.aspx?c=1&p=45089&cat=1,240,41064

Comments appreciated.

Allthunbs


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## edp (May 25, 2007)

It is not really much of a challenge to get accurate, splinter free cuts with a circular saw. It will require you to invest about 30 minutes of your time and some of the cut offs from your scrap pile. I recommend starting with a 10" or so wide strip of 3/4" thick plywood of sufficient length to accomodate the sheet size you are cutting. Measure in about 6" from each end and snap a chalkline. Using the chalkline as a guide, attach a narrow strip of plywood (2 or 3") as an edge guide for the sole plate of your saw. I use glue and screws. Now, clamp this to a pair of saw horses and rip the base with your saw against the guide strip. The tool is now finished. To break your sheets down, mark the cut line on each end of the sheet with a pencil, align your saw guide with the pencil marks and cut away. A perfect cut everytime, and because your guide is resting on top of the sheet you are cutting, you will get a splinter free cut.

Ed


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## TheRecklessOne (Jul 22, 2008)

Use a straight edge. Swanson makes an aluminum straight edge that I use when cutting plywood. It's like 18 bucks at lowes or something. Buy a plywood cutting blade. Use masking tape..I don't really like painters tape because its more expensive and I don't feel like it works as well. Take your time. Don't rush the circ saw. It'll pay off.

Measure twice and write it down!

I cut all my plywood on 2 - 4' x 8' half inch sheets of blue foam on the ground. The plywood lays flat and doesn't slide. I wouldn't use saw horses. The only thing a sawhorse is good for is spray finishing trim :yes:


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