It is very hard to rip with a straight edge for repeat rips unless you make a block for a gauge . The block is set the same distance off the edge to set the straight edge each time.

Tim Mooney

http://www.taunton.com/finewoodworking/pages/w00035.asp

Heres what I would do lacking a table saw.  Don't let HD or Lowes do it, they will screw it up.

Figure out the width you want for the book cases

Pick up a piece of 3/4 MDF

Figure out the distance between the edge of the tooth that kicks out towards the edge of the saw and edge of the base of the saw.

Rip a piece of MDF off one side about 2 inch wide. 

Then Rip another piece off the other factory edge wide enough to accommodate the width of the shelf + the two inches of the first piece

Put it together like the picture.

You can use it as a carriage for consistent rips if you clamp it to the edge of the Birch.

Make SURE the factory edge is facing out so the saw rides against one and board rides against one.

Set it up on saw horses with a sacrafial 2x to make sure the piece your cutting doesn't hit the ground when you cut it off. and adjust the saw depth to about 1 1/4" and have it.

Use a good sharp thin kerf blade and flip the plywood finish side down to avoid tear out.

Make sense?

At least that's what I do with out a table saw.

Go Jayhawks

Uncle Dunc gave you the easiest and best answer to your dilemma. Some people refer to this as a "shooting board," others call it a "rip guide," and I'm sure a lot of other names are used as well.

Bottom line, DON"T BUY a sheet of MDF as was mentioned by another poster...too costly for setting up a rip guide...buy a sheet of 1/4 inch luan, or 3/8 plywood. Rip approx a 2inch wide piece off of the one factory edge side and attach it with glue and drywall screws to the other factory edge. Don't worry that the drywall screws will penetrate too far through the wood...flip the wood piece over and "snap" off the protruding tips by wacking the screws with your hammer..they should break off clean. If not, leave screws in place until glue drys and then permenently remove screws.

This 2 inch wide "top piece" that you attached to the main sheet becomes your "fence"  for your circular saw. Install whatever type blade you plan to use (when cutting your book cases) onto your circular saw. Now using the 2 inch strip fence as a guide, run your saw against this fence and cut through the main sheet. Rip the entire 8 ft length. Throw the cut-off piece out. The remaining piece ( or "body") with the strip fence already attached, becomes your rip guide jig.Now you have the perfect guide jig with no need for measuring saw blade distances.

Simply mark each end of the cut-line on your bookcase material, line up the the edge of the rip guide's body next to that line, and clamp this jig in place.  Set the cutting depth of your saw to that of the material you are cutting through, plus add to this depth the thickness of your jig's body.Now run your saw as before,  against the strip fence and you have it. Wipe off any sawdust that may gather on the jig after each cut so that your saw will run smoothly and tightly against the strip fence.

This jig is cheap to make and will yield good results. Use a carbide toothed blade on your circular saw for cutting ease and to minimze tear-out...the more teeth ( 40 is good) the less tear-out.

If by chance you opt for something else, don't buy a cheap table saw, this will do you no good at all. Most of these types only allow for 12 inch wide rips...hard to rip a full size sheet ( dangerous!) on one of these lil things.  Rather, opt for no less than a contractor grade table saw that allows a fence width of at least 24 inches from the blade. When ripping plywood on a table saw, the wider the table, the safer and easier it is to make the cut...also accuracy improves.  If you buy a table saw and unless the fence system is a biesemer style, you will need to physically measure the distance from the blade to the fence at both the front and back locations whenever you are setting up the fence to make a cut.  Failure to do so can result in a crooked fence line-up; resulting in a crooked cut...you don't want that do you?

Last but not least, if you don't like the circular saw set-up, and you don't want to invest in a table saw just for a few rip cuts, then contact a local cabinetshop, moulding shop, custom hardwood supplier , and or a kitchen counter top shop, and have them rip your sheet goods to size. They will most certainly do an accurate job for you. It may cost a few extra bucks, but in the long run may be the most hassle free and cheaper than a cash out lay for a new saw.

LOL.

Davo

Davo,

 Around here a 3/4 MDF is going to cost about 10 bucks more then 1/4 in luan.

IMHO 1/4 inch material could be a bad choice for two reasons.

1. Its to flexible, I like my guides nice and rigid 2. Depending on the saw, many have a radius on the shoe which the saw could "jump" and ruin the piece.

The reasons I didnt suggest the same as Uncle Dunc is because he wants very consistant rips, and I also took it that he did not have much luck ripping in the past

 Its possible the way you and uncle dunc suggested but the set up time of laying each piece out and making it perfectly square at the perfect width for a multitude of the same cut adds up

The way I suggested will you give a very consistant width and is self squaring to the ply.   I've tried both ways, a shooting board is great for one or two off cuts, But they take much longer to square up and its harder to ensure you get the exact same width every time. opposed the other way.

Go Jayhawks

Buy a "good" table top table saw and good in feed and outfeed portable rollers.

You wont regret it. I dont think theres one job I do that I don't take my Makita with me. I've had that sucka over ten years and its still crankin like new (doesnt look it though....lol).

I've done big and small jobs on it.

I also own a very very good Powermatic 5 HP table saw with two different rip fences.a Biessmyer and the original Powermatic rip fence but I have to admit..I use my portable table saw ten X's as often..being that its portable.

Be portable

           Namaste

                     Andy

Uncle Dunc,

  You only need about 6 different ones :)  if you just screw the two pieces together you can un-screw it later and move the "fence"  And like I said its a lot easier to ensure square and equal cuts repeatedly 

  It certainly doesn't replace a table saw, but it beats the heck out of trying to rip down 4x8 sheets on a little job site saw when you don't have a stand, out feed roller and an extra set of hands... 

Go Jayhawks

I bought a small Rockwell table top saw.

With out a doubt, it will not rip plywood good enough.

I bought a simple aluminum saw guide that clamps to the wood for ####rip up to 8 feet.

Worked great, still does after 25 years.

It's like the guides suggested that you make out of wood (I've made
a bunch of them also over the years).

They all will work better then the small saw.

Even today with my large cabinet saw, I'll often break down a large
sheet with that old guide.

Hope that helps.

Jeff