More Speed for a Finer Cut?

algale · Post by **algale** » Sat Nov 23, 2013 9:50 am

When I went to the Lowe's demo last week, the demonstrator made two cross cuts through a piece of what I think was sugar pine to demonstrate the advantages of having a variable speed table saw. He was using a combination blade. The first was done at what I think was normal table sawing speed, I think he said 3450 rpms. The results had some chip out. For the second cut, the demonstrator adjusted the PowerPro speed up to 5000 rpm, if I recall correctly. The cut was much smoother without any chip out. The demonstrator explained that increasing the speed puts more teeth through the cut per second and effectively turns your combo blade with 40 teeth into a cross-cut blade with a greater number of teeth. And I suppose one could do the math and figure out the rpms at which a 40 tooth combo blade would effectively give you the same number of teeth per second as a cross cut blade with a greater number of teeth spinning at 3450 rpm. [Ok, I did the math. If my math is correct, a 40 tooth blade spinning at 5175 rpms will deliver the same number of teeth per second as a 60 tooth blade spinning at 3450 rpms; and a 40 tooth blade spinning at 6900 rpms will deliver the same number of teeth per second as an 80 tooth blade spinning at 3450 rpms].

While I have slowed my table sawing speed to get increased torque (I don't have a PowerPro) when cutting difficult woods, it never occurred to me to speed up my blade to get a smoother cut with less tear our (when the increased torque isn't necessary). I think my Forrest WWII is rated to 7000 rpms (although manufacturer recommends 3000-5000). Has anybody else heard of doing this (speeding up the blade to get smoother cuts)? Can anyone think of a reason not to try it (other than the loss of torque on a normal motor and potential for bogging down my motor)?

dusty · Post by **dusty** » Sat Nov 23, 2013 12:01 pm

algale wrote:When I went to the Lowe's demo last week, the demonstrator made two cross cuts through a piece of what I think was sugar pine to demonstrate the advantages of having a variable speed table saw. He was using a combination blade. The first was done at what I think was normal table sawing speed, I think he said 3450 rpms. The results had some chip out. For the second cut, the demonstrator adjusted the PowerPro speed up to 5000 rpm, if I recall correctly. The cut was much smoother without any chip out. The demonstrator explained that increasing the speed puts more teeth through the cut per second and effectively turns your combo blade with 40 teeth into a cross-cut blade with a greater number of teeth. And I suppose one could do the math and figure out the rpms at which a 40 tooth combo blade would effectively give you the same number of teeth per second as a cross cut blade with a greater number of teeth spinning at 3450 rpm. [Ok, I did the math. If my math is correct, a 40 tooth blade spinning at 5175 rpms will deliver the same number of teeth per second as a 60 tooth blade spinning at 3450 rpms].

While I have slowed my table sawing speed to get increased torque (I don't have a PowerPro) when cutting difficult woods, it never occurred to me to speed up my blade to get a smoother cut with less tear our (when the increased torque isn't necessary). I think my Forrest WWII is rated to 7000 rpms (although manufacturer recommends 3000-5000). Has anybody else heard of doing this (speeding up the blade to get smoother cuts)? Can anyone think of a reason not to try it (other than the loss of torque on a normal motor and potential for bogging down my motor)?

The manual for the 510 shows specific speed ranges for sawing Hardwood and for Softwood. Those two categories are further divided in General Sawing, Heavy Ripping and Trim Cuts.

What the demonstrator was showing you is not a departure from normal operation. With the PowerPro, the speeds that he recommends may be more comfortable (for the machine) but they are also achievable with a 510.

The RPM range, according to the manual, for saw operations is 2800rpm to 3800rpm. Getting up to 5100rpm puts you in the planer which is really "top end". I don't go there.

Realize that you loose some torque as the speed goes higher.

Just curious: Was the demonstrator Mike Young?

Also curious: Is 5100rpm a resulting speed that the PowerPro is programmed to run at for SAWING HARDWOOD or is this an over ride option?

JPG · Post by **JPG** » Sat Nov 23, 2013 12:08 pm

Tis more to this than blade rpm/teeth.

There is also the feed rate of the workpiece.

When torque is needed, slow it down, but also slow the feed rate also.

This is the same set of parameters for routing with a 'slow' SS. i.e. ya need to feed slowly(teeth biting/feed distance.)

For smoother cutting, nibble rather than tear.

algale · Post by **algale** » Sat Nov 23, 2013 12:15 pm

dusty wrote:The manual for the 510 shows specific speed ranges for sawing Hardwood and for Softwood. Those two categories are further divided in General Sawing, Heavy Ripping and Trim Cuts.

What the demonstrator was showing you is not a departure from normal operation. With the PowerPro, the speeds that he recommends may be more comfortable (for the machine) but they are also achievable with a 510.

The RPM range, according to the manual, for saw operations is 2800rpm to 3800rpm. Getting up to 5100rpm puts you in the planer which is really "top end". I don't go there.

Realize that you loose some torque as the speed goes higher.

Just curious: Was the demonstrator Mike Young?

Also curious: Is 5100rpm a resulting speed that the PowerPro is programmed to run at for SAWING HARDWOOD or is this an over ride option?

The demonstrator's name was Bill or Billy Martin, I believe.

Someone with the PowerPro will need to answer the programming issue.

I am curious enough now that I will probably experiment. It may be that the torque with a non-PowerPro head is just too little to operate at the high RPMs.

dusty · Post by **dusty** » Sat Nov 23, 2013 12:26 pm

algale wrote:The demonstrator's name was Bill or Billy Martin, I believe.

Someone with the PowerPro will need to answer the programming issue.

I am curious enough now that I will probably experiment. It may be that the torque with a non-PowerPro head is just too little to operate at the high RPMs.

With sharp blades and proper feed rate I don't believe you will need to worry about your Mark Vs capabilities to cut wood. Just don't try to mill any logs.

The only time I have trouble is when I need to bury the blade like when cutting 4x4 or 6x6 fence posts.

When doing that, remember the old adage: The right tool for the job.

WmZiggy · Post by **WmZiggy** » Sat Nov 23, 2013 12:52 pm

I don't think this is too far afield as it deals with blades and wood. Running the SS Planer or Jointer with increased speed, shallower depth of cut, and slower feed rate will give a smoother cut.

Ed in Tampa · Post by **Ed in Tampa** » Sat Nov 23, 2013 2:27 pm

While speed may seem like a good thing it can also cause burning. Not so much on pine but on cherry you have to be real careful of the speed so as not to cause any burning.
The faster the blade turns the hotter the blade gets because the teeth are cutting wood more. As this heat increases burning can occur.

I would rather go with more teeth to accomplish the smooth cut I was after.

WmZiggy · Post by **WmZiggy** » Sat Nov 23, 2013 4:26 pm

I agree. I don't work with cherry often, but when I do it's temperamental, especially with high speed router bits. I don't use my Mark 500s to cross cut and rip, as I have a radial arm and table saw for that. For ripping I have a thin kerf Freud blade designed for ripping. On the radial arm, I use a Forrest blade designed for smooth cross cuts. I don't like combination blades.

wa2crk · Post by **wa2crk** » Sat Nov 23, 2013 7:05 pm

Was Billy Martin wearing a Yankee uniform?:D
Bill V

charlese · Post by **charlese** » Sat Nov 23, 2013 7:36 pm

No one has yet mentioned the maximum RPMs of the saw blade. The maximum speed of the Shopsmith carbide blades is printed on the side of the blades. It is 5,000 RPM. Correction - Shopsmith blades maxim speed is 5500 RPM

Now to the number of teeth per second giving a smoother cut. I assume we are talking about cross cuts. The answer is yes. More teeth passing through the wood in a time period will result in a smoother cut. (up to a certain limit I assume)

This is not necessarily true for rip cuts. There are other considerations such as blade angle and gullet configuration.

That's why Shopsmith offers a 60 tooth crosscut blade. With fewer RPMs the crosscut blade will yield a smoother cut. http://www.shopsmith.com/ownersite/cata ... blades.htm

The right tool for the job is always better that pushing the limits of the wrong tool. I'd hate to hear from someone that was injured by a flying tooth from a carbide blade.