12" or 14" for RAS blade question

[accentphotography]

Besides price, if your RAS can handle a 14" blade, is there any reason why you would use a 12" over the 14" size? Keep in mind that I will have either a 6" or 7" stabilizer set when I make my decision on the Forrest Woodworker I blade. I realize there is a little deeper cut (extra inch) and the blade on the 14" in theory should not get as hot as the 12" (if that is even discernible) or is it about HP? I will have a 5hp but I may have the option to going to a 3hp motor.

 

[junquecol]

I would go with the 12" blade. It will also fit a 12" CMS, but not so for the 14" one. As a plus, you can ofter get reasonably priced 12" CMS blades. My RAS takes either 12", or 10" blades. Being as how 10" blades are cheaper, my choice is easy. Plus they will also fit my table saw.

 

[mkepke]

You'll need a 14" blade to cut 4x4 material in a single pass. This may or may not be important to you.

Other than that (depth of cut) and price, there's no reason to favor a 12" over a 14" or vice versa.

-Mark

 

[accentphotography]

Actually that 4x4 advice is very handy. I can foresee that in the future. If you get a chance check out this Dewalt RAS video. Thats a darn good setup RAS:

http://www.youtube.com/watch?v=aUnZpUDvzgs&feature=related

Thanks!

 

[mshel]

The key thing is a negative rake on the blade. If you noticed, the blade didn't climb in the video. Very important to keep in mind.

Mike

 

[accentphotography]

Forgive the ignorance but could you explain the "negative rake" thought.

 

[mshel]

Forgive the ignorance but could you explain the "negative rake" thought.

Simply put, if you draw an imaginary like from the center of the blade outward, a negative rake blade tooth will lean away from the line. A positive will lean toward the line. In a nutshell, for radial arm saws, especially with high hp models, a blade with a positive rake will bite and climb and hopefully your hand / arm is out of the way when it does. A negative rake blade will not grab, climb and gives you more control of the cut. So, it is not recommended to switch your table saw blades (positive rake) with your RAS blades (negative rake).

Hope this helps

Mike

 

[accentphotography]

That was what I was thinking. So do most people adjust that by raising the back of the table or is the adjustment made somewhere else?

If you were to measure the blade's (we'll say from the bottom the lowest tooth) negative rake from touching the back of table (0") to the end of the front of the table are we talking about a difference in 1/8", 1/4" ... etc (this is for a standard arm)?

Is this technique good only for simple 90 degree cross cuts? It seems that a 45 degree (for example) bevel cut would not have a perfect 90 degree finished on the cut edge.

Please understand that I have not had the saw delivered to me yet so I am just guessing here. I would like to have as much of a perfectly setup saw as possible. I have a Delta DJ-15 planer and 20" jointer so I want the RAS to match the quality of work that the other tools produce.

So if the saw was set to a 0" at the back and a 0" at the front would the saw perform just as well as the one with the negative rake?

By the way, nice furniture Michael. I aspire to achieve that level ... one day ... :eusa_booh

 

[mkepke]

Hi Ken..you've misunderstood. In this discussion, rake refers to the geometry of the teeth on the sawblade only and has nothing to do with the saw.

Rake is manufactured into the blade during the manufacturing process.

Mike explained rake already, but here's another try: when you look at the teeth of the blade, will the topmost portion of any given tooth engage the wood being cut *before* the bottom portion of the tooth (positive rake), or *after* the bottom portion of the tooth (negative rake), or at the same time (0 degree rake; neither positive nor negative) ?

Pretty pictures here:
http://www.freudtools.com/images/PDF/sb_industrial.pdf

-Mark

 

[accentphotography]

Okay .. got it. That helps a lot. The catalog link is nice. Looking at it now. Now I need to see if Freud even resharpens their blades as it looks to high tech for the average blade sharpening company here. Thanks for the information. I don't want to buy the wrong expensive blade when the time is near.