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9/22/2017 12:11:25 AM
Posted: 8/2/2005 7:40:32 PM EDT

I am in the process of making a Murphy bed.


I need help making even square cuts over a very long piece of plywood. The cuts are up to 82" long. I am using a circular saw. Normally when I do small wood work I use a T-square clamped down as my guide.

But I am making extremely long cuts and the cutting is perfect for the first 20 inches or so then by the other end of the cut something has gone wrong (like a loss of 2/8"). Even though I thought everything was square.

The cut always wonders off the line. I have been using a straight piece of wood but I feel I need something better. I need a straight edge that will extend the whole length of the wood.

I need some advice on how to cut perfect lines over a long distance. And making sure everything is square.
Link Posted: 8/2/2005 7:45:16 PM EDT
No table saw, huh?
Link Posted: 8/2/2005 7:46:20 PM EDT

Originally Posted By palmer:
No table saw, huh?



I wish
Link Posted: 8/3/2005 3:19:07 AM EDT
bump
Link Posted: 8/3/2005 3:36:04 AM EDT
[Last Edit: 8/3/2005 3:41:21 AM EDT by Zaphod]
There are clamps which you can buy to create the straightedge you need. I just don't know if they are vailable in the length you need. I'll see if I can find a link.

ETA: Here you go (example)...

You may also want to consider a pipe clamp, which can be made to almost any length. I just don't know how well an 82-inch pipse will remain straight...


Another option is to create a "table saw" of sorts by buying a quality piece of flat, thick plywood, mounting the circular saw to it with the blade extending throug a slot in it, then flipping the plywood over. Use one of the clamps above to create a fence, mount the plywood to some sawhorses, then run your stock through SLOWLY.

Instant table saw.....
Link Posted: 8/3/2005 3:43:07 AM EDT
www.woodcraft.com/family.aspx?familyid=4607

or take it to lowes or home depot and see if they will cut it for you,using that big panel saw they have.
Link Posted: 8/3/2005 4:00:32 AM EDT
2/8"....

aint that like 1/4"
Link Posted: 8/3/2005 4:05:07 AM EDT
Use a drywall square & 2x4 at a guide.
Link Posted: 8/3/2005 4:06:05 AM EDT
Try using a jig saw instead of a circular saw.

It'll be easier to control along the length of the cut.
Link Posted: 8/3/2005 4:12:12 AM EDT
Link Posted: 8/3/2005 4:14:02 AM EDT
Your circular saw should be able to be fitted with a rip-guide. My Makita came with one and they work very well as long as the factory edge is straight(they generally are).
Link Posted: 8/3/2005 4:14:12 AM EDT
A straight-edge clamped then use the circular saw is the way to go. I have a table saw, but for long cuts like that, I use the circular saw and straight-edge. The new edge of the new piece of plywood should be straight enough. Cut a wide enough strip off of that and clamp it to the plywood. Place the circular saw against the new edge. You could maybe sand that edge a little so the saw will slide easily along it. Just don't sand it so much that it becomes wavy.

A murphy bed is quite an ambitious project for someone without a table saw. I wish you luck. If it comes out well (and the fact that you are asking these questions makes me think that you take enough pride in your work to make sure that it does), you will have some serious braggin rights. "Yep, nothin' but hand tools and my trusty old circular saw..."

-RJ
Link Posted: 8/3/2005 4:21:21 AM EDT

Originally Posted By hanau:
www.woodcraft.com/family.aspx?familyid=4607




Hey! Those are new!
Link Posted: 8/3/2005 4:23:43 AM EDT

Originally Posted By ikor:
You can make a guide...often called a "shoot board"...from a really straight 1X4, etc...or I have seen guys use clamps and a metal stud to do the same thing (Lowes will have metal studs...they are cheap and straight). Actually, the easiest thing to do if you don't have many cuts is to buy the ply at Lowes or HD, mark your cuts like you need them (make a list and take it with you) and have them do it on the panel saw like hanau said, IIRC they will give you two free cuts and the rest are like 25 cents each.



This is what I do - a steel stud or a piece of aluminum angle and a couple of inexpensive clamps and you are set.
Link Posted: 8/3/2005 4:26:03 AM EDT

Originally Posted By ikor:
You can make a guide...often called a "shoot board"...from a really straight 1X4, etc...or I have seen guys use clamps and a metal stud to do the same thing (Lowes will have metal studs...they are cheap and straight). Actually, the easiest thing to do if you don't have many cuts is to buy the ply at Lowes or HD, mark your cuts like you need them (make a list and take it with you) and have them do it on the panel saw like hanau said, IIRC they will give you two free cuts and the rest are like 25 cents each.

+1 in all respects. I use a clamped board or another piece of the same stock I am ripping, as a guide for the circular saw. With good clamp, alignment and a steady hand keeping even pressure on the saw against the guide, perfectly straight cuts are possible / routine.
Link Posted: 8/3/2005 4:59:09 AM EDT
Try a new, high quality saw blade.
Link Posted: 8/3/2005 5:11:10 AM EDT
I have a 2X4 piece of tube steel I got a scrap steel yard for a couple of bucks, and that is exactly what I use it for....

Dan
Link Posted: 8/3/2005 5:36:13 AM EDT
Rip the edge of a piece of plywood about 4 inches. Flip it over and you have an 8ft straight edge with the factory cut edge. Clamp it or screw it to the piece of plywood you are cutting as a saw guide.
Link Posted: 8/3/2005 5:43:45 AM EDT
[Last Edit: 8/3/2005 5:48:02 AM EDT by mousehunter]
Not sure if this is the issue or not, and please forgive me if I am saying something that you already recognize as obvious.

Dimensional lumber (2x) often can be perfectly straight till you cut it, but end up warped and twisted as all afterwards. I have noticed the quality of (affordable) lumber decline a lot since I started doing wood work. Mills are trying to get every last board out , and now marketing boards cut too near the heart of the tree. The grain of these all but prevents ripping. The grain is too circular, and when ripped you will get some terrible warping. I suspect if you want strait cuts you will to make a jig and practically need to re-mill the boards after you rip them.

Not sure if it is cost prohibitive, but life can often be much happier if you find a decent lumber yard (rather than a home improvement center), get higher quality lumber to start with. Finding a good trip shop (mill) can also be nice.

Anyway, good luck with your project. Oh, treat yourself to good staight edges and clamps. If you are going to be making a ton of simular cuts, consider builing a jig.
Link Posted: 8/3/2005 5:46:30 AM EDT

Originally Posted By tommygun2000:
Rip the edge of a piece of plywood about 4 inches. Flip it over and you have an 8ft straight edge with the factory cut edge. Clamp it or screw it to the piece of plywood you are cutting as a saw guide.



Somebody else mentioned having a sharp saw blade. This is every bit as important as having a ripping guide. They are inexpensive at the home improvement stores.
Link Posted: 8/3/2005 5:48:49 AM EDT
2 options I have used.

1. a factory edge (such as a sheet of plywood) from a piece of matwerial a few inches wide, clamped to your material, then use a circular saw.

2. chalk line. Follow the line and go slowly. It will be perfectly straight, but you will probably have to sand to clean it up.
Link Posted: 8/3/2005 5:52:09 AM EDT
Sharp blade, metal guide(home dome $16) or make a guide out of another material (1/4" masonite)
Link Posted: 8/3/2005 6:08:17 AM EDT

Originally Posted By hanau:
www.woodcraft.com/family.aspx?familyid=4607

or take it to lowes or home depot and see if they will cut it for you,using that big panel saw they have.



I have an extruded aluminum edge guide similar to that. It uses small C-clamps.

It's invaluable IMHO.
Link Posted: 8/3/2005 10:56:45 AM EDT
Get a straight piece of scrap, screw it to the material you are cutting and use as a fence.
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