Circular Saw Blade Selection question

[Keith Woythaler]

Hi all,

I am planning on doing work on mostly furniture pieces (i.e., plans such as found @ Ana-White), and before I get started I figured I would replace the older blade in the circular saw (the saw, which works perfectly fine was passed down to me with a fairly used 24T blade).  As it is my first time purchasing a blade, I am curious what tooth size I should look for.  I could very well be wrong, but I am assuming that a higher tooth count would be helpful for cutting wood to be used in furniture pieces as higher tooth count provides finer/smoother cuts, right?

From what I was able to find online it seems maybe a 40T or 60T would be good?  And carbide-tipped as well?

And I'm sure I would be doing some combination of cross-cutting and ripping at some point, so a combination or compromise blade of some sort is probably what I'm looking for.

Any ideas?

[Ken Darga]

"Carbide" tooth blade is the way to go.

Obtain blades for their intended purpose.

The marking on the blade and the packaging defines the specifics.

Blade tooth types, and how they're shaped and ground, are described by the OEM.

Ripping blade for rough cutting lumber ---

blade features a deeper gullet, so as to carry away the larger chips faster.

Position the blade height so the gullet is exposed at the workpiece surface.

A 24 tooth blade for general purpose ripping and cross-cutting of construction grade lumber.

Does not produce a smooth cut.

40 tooth blade for most general purpose.

Produces a relatively smooth cut.

60 tooth blade to obtain smooth cuts.

80 tooth blade to obtain very smooth cuts.

100 tooth blade to obtain ultra-smooth cuts.

[justin waldron]

You will get good results from Freud, they're sold at Home Depot, relatively inexpensive and do a good job.  Their general purpose 40 tooth does a good job ripping hardwoods and also on plywood.   I use a 40 tooth for cutting harwoods and a 60 tooth for plywood in my shop making cabinets and they have done well by me.

[Keith Woythaler]

Thanks so much guys!

I guess maybe I will start out with a 40T blade as it will be significantly smoother than the 24 and it should work well as a general purpose blade on both plywood and lumber for my projects.

Justin.....are the Freud blades the same as the Diablo blades I see Home Depot selling?

[Ken Darga]

Diablo is made by Freud---

a lower cost version.

A 60 tooth will provide a smoother cut edge than a 40 tooth on plywood,

as well as cutting thinner materials.

Option:

a 7-1/4" 60 tooth blade, can be used in the table saw, miter slide saw and a circular hand saw.

(less costly than a 10" blade)

A 7-1/4" blade is adequate for cutting most materials on a table saw.

[Rick]

Ken let me make sure I understand what you just said.  The same size blades in my 7.25 inch circular saw will work in my new Dewalt 10 inch table saw?  Is that correct?  Thanks
Ken Darga said:

Diablo is made by Freud---

a lower cost version.

A 60 tooth will provide a smoother cut edge than a 40 tooth on plywood,

as well as cutting thinner materials.

Option:

a 7-1/4" 60 tooth blade, can be used in the table saw, miter slide saw and a circular hand saw.

(less costly than a 10" blade)

A 7-1/4" blade is adequate for cutting most materials on a table saw.

[Ken Darga]

Rick, 

A 7-1/4" saw blade can be used in a 10" saw; however, it cuts slower.

and it suffices on smaller material(s).

Standard arbor dia on most saws is 5/8".  The blade must fit the arbor.

 

Circular saw blades are available in different sizes.

Diameter is the span from one edge of the circle to the other measured along a center line. A saw doesn't have the capacity to cut that deep, though. Maximum depth of cut is less than the radius. It cuts no deeper than 1/3 of its diameter.

A 10" saw cuts about 3" deep at maximum capacity, and usually less. A big blade has greater cutting depth. Not only can a larger blade cut deeper, it also has a larger circumference, or the measurement around the rim.

A longer cutting length around the circumference makes space for more tips overall. For this reason, bigger blades have longer endurance. Small blades have less circumference circling the rim, which explains how fast they get used up.

A 10” blade might last the equivalent of two smaller ones. However, large sizes won't necessarily allow faster feed; coarseness determines that.

 

Rotation Speed

RPM means Revolutions Per Minute. One revolution is one turn around in a circle.

To find out how fast it is revolving, look on the motor for the RPM specification.

Revolutions are different from peripheral rim speed; also called SFM (Surface Feet Per Minute). How fast does a saw go at the rim?

If a big saw blade were turning at the same RPM as a small one, it would have greater SFM and go faster at the surface.

Maximum SFM for saws is around 18,000, but recommended speed is typically lower, especially for sawing hard materials. This is why a cold saw for metal cutting is built to run at a very different, much lower SFM than a typical saw for woodworking.

For an average woodcutting example, a 10 in. miter saw turning at 5,000 RPM goes a little over 13,000 SFM. Calculate your own saw rotation speed by following the steps of this formula:

 

 SFM (Surface Feet Per Minute)

Measure the diameter in inches and divide it by twelve to find the diameter in feet.

Then multiply it by pi, (3.14) to get the circumference in feet.

Finally, multiply it by the R.P.M. to get S.F.M.

Rick said:

Ken let me make sure I understand what you just said.  The same size blades in my 7.25 inch circular saw will work in my new Dewalt 10 inch table saw?  Is that correct?  Thanks

[Jay Boutwell]

Hi Keith,  Although this does not apply to a hand held circular saw the time will come when you will graduate to a table saw.  When you do  something to think about when changing from a 10 inch blade to a 7&1/4 inch blade is the throat plate in the table saw.  Since there will be more space in the front and the back of the blade there is the hazard of some material catching in the front of the blade and can pose a safety threat.  You can make your own throat plate out of something like 1/2 inch thick Baltic birch.  Cut the shape of the old throat plate lower the saw blade all the way down and fit it into the saw table so that it is level with the surface and tight in the table top.  Sand it smooth and wax it up with something like Johnson's paste wax so it is slick.  Move the fence over the edge of the new installed throat plate and turn on the saw and slowly raise the blade up cutting the blade kerf in the throat plate.  Continue raising the blade until you reach the total height of the saws blade carriage.  This will give you a safe superior throat plate cover to what is on there now as it is a zero clearance cover.  Depending on the saw model you can also purchase throat plate covers of which you cut the saw kerf in them. This would be the method of cutting one for all purpose cuts of different heights.  A better zero clearance plate would be one of which you only raise the blade to the height you wish to cut.   For example I use mostly 3/4 to 13/16 thick stock so I have a plate that I use to cut this specific thickness and change if I cut 1/2 inch thick material.  I do the same if I cut thin material like 1/4 inch or less.  IN these plates I have the kerfs cut just a bit higher than the thickness of the material.  A good rule of thumb is to have the blade exposed about 1/4 inch above the material you are cutting  I know it sounds like a lot of work changing the throat plates but it is worth the effort as the resulting cuts you get are superior to those made with a factory plate.  You can copy the factory method of removing the plates however since it is wood I usually use a screw that I drive into the plate when I need to remove it.  I drive it into the wood leaving about 1/4 to 1/2 inch into the plate and use this to pry out the plate.  A claw hammer works great for me but the method of how the factory made the plate may dictate a different method.  The important thing here is make sure the plate is secure in the table so it does not raise up in operation of the saw.

Since I use the  table saw for many different cutting operations and have made myself many throat plate covers to fit specific cutters from  large molding head cutter to a zero clearance plate for cutting thin stock for inlays as well as thick material that I cut at a specific height.  Not only is it for safety but a zero clearance gives you a better cut with less tear out in the cut.   It is a safe and efficient method that has given me excellent results for many years.  Happy wood working and work safely. 

[Ken Darga]

diablo saw blades product info

http://www.diablotools.com//products?c=Saw_Blade

[Rick]

Dewalt blades does anyone use them?  

[ray vile]

I use both the 40t and 60t Diablo blades from the Home Depot, I use them for breaking down the bigger sheets of plywood to more manageable pcs. for the table saw. I work in my basement so getting a 4x8 sheet of plywood down there is close to impossible, The combination 40t blade does a really good job with very little splintering. If I iwas only to use one blade I would get the 40t one.

[Rick]

I think the way I will go is a 40 tooth rip blade in 7.25 a 80 t crosscut finishing blade 7.25 and make zero clearance throat plates for both.  The 24 tooth blade that comes with the saw will be researved for construction grade materials like decking maybe?  Does this make sense to everone.?

[Jay Boutwell]

Hi Rick, You are correct about the zero clearance throat plates.  However I never use saw blades other that the 10 inch but making a zero clearance throat plate is standard procedure for me.  I make one for all the heights that I cut so that it is a true zero clearance plate.  I get better cuts doing it this way.  Since I also use the table saw for doing a variety of operations I also make special throat plates for them as well.