Cutting straight with a circular saw

[reeljob]

You'd think I could do it. I set up a fence running the length of a sheet of plywood, using a thin kerf carbide blade. I don't wander from the fence at all. How come, with my seemingly good setup, does the finished cut sometimes have a distinct wavy edge? Could i be pushing the saw too hard, causing the blade to wander? It's not like I moved from the fence and came back, rather it is really even looking. I'm really not sure why it is doing this.

Thanks

[muscongus]

Hello,
I find that thin kerf blades tend to wobble a lot, flexxing and oscillating.
Faster feed rates result in more wobble, but I never have had satisfactory results with them on circular saws or table saws.
There are plates available to stiffen them, but why not just use a normal kerf blade for these plywood cuts.
Jack

[Tom W.]

The freud blades have expansion slots machined in the blades to keep the blade from warping as it heats. I have had very good results with these blades, both in a hand held circular saw and table saw.
It takes very little wobble, either due to blade warp or saw movement to deviate from the straight line, in my experience.

[muscongus]

The too thin Freud blades wobble just fine, it's not heat it's just too thin. On the table saw you can see them wobble as soon as you start a cut. The regular Freud blades aren't bad.
(I know heat Can be an issue, the slots help, but what I see is just a too thin blade wobbling from lack of stiffness)

[ishmael]

Hm. Assuming a rigid fence it sure sounds like blade flex. Slow down, use a beefier blade, or both.

[Tom W.]

The Freud blades I have used work well. There are ways to keep heat at a minimum by adjusting depth of cut, using a shallow setting. This cuts down on heat, but sometimes a deeper cut will give you more blade inside the cut and therefore more straight line control. My experience has been good with these blades using very close scrutiny of the blade travel. I also have used 7 1/4" blades in the 10" table saw with good results on hardwood ripping. There are probably better blades out there for some jobs, but I have had little problems since using the Freud blades. Plus they hold an edge well.

[reeljob]

Thanks for the replies. Initially, I was using a normal kerf plywood/composite blade. It had many fine teeth, cut VERY slowly, got very hot, and all round did not work well at all. It also had this wavy cut, even though it was thick. It did get extremely hot, though. After that I've been using a carbide tipped 24 tooth skilsaw blade. Its pretty thin, but not as thin as some I've seen.

I just got four free Avenger (i think) blades, think kerf, carbide, they've got big slots in the blade. I'll give these a try and cut more slowly.

[Dave Wright]

Check the saw shaft for play in the axial direction (pull and push on it).

Dave Wright

[ishmael]

Dave's thought was my second. What's the saw?

[Mrleft8]

Dull blade (s), and thin kerf. I only use thin kerf blades on cross cuts.

[Tom M.]

Could be too thin a blade, could be excessive arbor runout. Also, worm drives have tighter arbors than sidewinders in my experience.

I'd find a good table saw to use.

[reeljob]

Just made a jig I saw on DIY channel. Tried cutting the wavy edge off of a ply sheet with that Avenger blade- worked better. I cut it slower, and it seemed to work fine. Wasn;t any more of that wavyness. The saw I'm using is a 14 amp Craftsman that I got a couple of years ago. Its worked pretty well for me. I'll check and see if there is any play in the shaft- I don;t think there is though.

http://i74.photobucket.com/albums/i254/reeljob/DSC00780.jpg

[RodB]

Try cutting with one of the Red 40 tooth blades from HOme Depot...and perhaps a decent worm drive saw. I use a Makita Hyphoid and it cuts beatifully and if my straight edge is straight...the cut is straight. Large wormdrive saws are very stable and do not wander very easy.


Another great solution is Eurekazone's Smartguide (www.eurekazone.com) (the two section 100" kit) with any circular saw mounted in their base. This system is hard to beat handling ply panels and is not expensive. The Smartguide table is very affordable and is the center of this system...hard to beat.

The smartguide works with any right bladed sidewinder circular saw with the Porter Cable 325 mag as one of the best recommended with dust collection. The Hilti 267 is a great saw with this system too.

I can cut straight and square with my Makita Hyphoid following a line freehand with almost no effort. Wormdrive saws have a "gyro" effect with the motor and blade running in different planes. . . which makes for easy control when cutting...and running these left bladed saws on a straight edge offers good visibility while cutting and a nice square cut.

Good luck,

RB

[Tom Hoffman]

Back in 90, Irwin introduced the Irwin Marathon, I got one for a project using plywood. I have never used anything else in my circular saw. You can rip dead straight. The finish cut is not smooth like a Freud Teflon Coated 80 tooth blade on my table saw, but for fast straight cuts on plywood, I doubt you will find its equal anywhere.

[ErikH]

The trick to perfect straight cuts is to turn the saw upside down, increase HP to about 2-5 HP, add a cast iron table, and put it in a a cabinet ;)

heh.

Really, though: You may wander from the fence more than you think. perhaps a festool setup would help?

[Ken Hutchins]

Stop all the hype of this blade is better than that blade etc.
First the saw, the edge of the sole plate of the saw MUST be ABSOLUTELY parallel to the blade also the collars and nut must be square and run true to the centerline of the arbor.
I can cut perfectly straight with a 30 year old piece of crap B&D plastic housing saw with a hand sharpened steel blade, because I pay attention to the small details with precision.

[GregH]

My money is with Dave Wright (shaft play). I was at a woodworking show years ago, and happened upon a fellow selling circular saw blades. Another guy and I watched in amazement as he sliced off piece after piece of maple, oak, etc. with glass-like surfaces- using his blades on what looked like a $75 Monkey Wards bench-top table saw. At one point, he was called away from his booth. I lifted the saw to see underneith. The stock motor/mechanisms had been replaced with a SOLIDLY mounted precision motor that obviously had bearings that were left over from one of NASA's spacecraft!! He could have made clean cuts with a pie tin for a blade!

[Dave Carnell]

For ten years I sold the 7¼” 36-tooth MS71436 Matsushita combination thin kerf carbide-tipped saw blade by mail to hundreds of satisfied customers. Bob Simmons, a boatbuilder in Sand Point, ID, introduced me to the blades, about which I never had a complaint and many rave reviews:
Robb White: “You have the best circular saw blade I ever used…the most startling thing is how fast you can feed to it with a power feed without burning, overloading the motor, or gyrating in the cut. About the only thing I use a circular saw for in the boat shop is ripping rails…I use poplar, hickory, longleaf yellow pine and ash to make rails with and ripping hickory and longleaf pine was all my little jackleg rig could do with the power feed geared down as slow as it would go. With that blade, I can speed it up so that it is hard to keep up with and there is never any circuit breaking tripping, burning of the wood or wandering…One of those blades is a revelation in a skilsaw too, I sawed a huge ash log a man gave…it had about eighteen inches curve in the twenty foot log. The lumber was too valuable to waste any by trying to straighten it out so I sawed it into five quarter flitches on my sawmill…I have been ripping one inch rails around the bend with a short-fenced skilsaw and one of those blades. I couldn’t imagine doing that with any other blade…the smoke would suffocate me but it ain’t nothing but a trick with your blade, They last too….” “Mac” McCarthy (Feather Canoes) reported he could rip the strips for half a dozen canoes before resharpening. They have been very popular with strip builders because so little wood is wasted as sawdust. Thomas Firth Jones wrote about the smooth edge of cuts made in acrylic plastic. Matsushita doesn’t recommend them as ripping blades, but they work beautifully. Any other blade has a thicker kerf and costs more. In a 10-inch table saw they cut 1¾” thick at 90°.

I’ve retired from selling them, but you can find sources by a froogle.com search. My last purchase was five blades that I donated to Cape Fear Community College. The instructor and students were amazed at the thin kerf and smooth cut.

[Wes White]

I'll second that, Dave.

[Philip Maynard]

Working as a house carpenter, I was cutting sheathing for a circle window freehand with a circular saw, someone asked how I did that and I told him I used a curved blade.

[johngsandusky]

Take a good look at your saw. Measure the edge to blade, front and back. Some saws are not parallel, right out of the box. Sometimes the base isn't flat either.