Math Question

Gene Howe · Post by **Gene Howe** » Fri Jan 24, 2014 1:56 pm

I can barely add, subtract, multiply and divide, so I'm asking youse guys for help.
Where should I set the speed control to achieve the same tooth speed for a 7.5" blade that a 10" achieves at the teeth?
Some 7.5" will give a smaller kerf and are certainly less expensive. Although, I'll be using Tenryus to insure quality, and they are not cheap!
Thanks to you math whizzes for the help.

JPG · Post by **JPG** » Fri Jan 24, 2014 2:23 pm

Peripheral velocity is proportional to the diameter since the circumference is pi x diameter. So 10 / 7.5 = 1.333, then multiply the 10" speed by that.

So if 'normal' is 3000 rpm, set it to 4000 rpm.

More importantly, let the saw tell you if it is a 'good' speed.

nothungry3 · Post by **nothungry3** » Tue Feb 04, 2014 8:41 pm

My deWalt circular saw runs at 5100 rpm.
Set max speed and follow JPG's advice.

Gene Howe · Post by **Gene Howe** » Wed Feb 05, 2014 7:48 am

Thanks, JPG. That I can do!

JPG · Post by **JPG** » Wed Feb 05, 2014 7:54 am

Gene Howe wrote:Thanks, JPG. That I can do!

Where ya been?

Snowed in????:D Ya musta gotten more than one flake!:eek:

robinson46176 · Post by **robinson46176** » Wed Feb 05, 2014 3:52 pm

JPG40504 wrote:More importantly, let the saw tell you if it is a 'good' speed.

I rarely pay much attention to the dial other than to look to be sure that start up speed is reasonable for the setup.
Actual working speeds are sat by ear / feel.
I have spent my life using all manner of machinery from a lot of different occupations and very few of them had any sort of indicator of speed. One of my most common settings is "about like that".

.

Gene Howe · Post by **Gene Howe** » Wed Feb 05, 2014 4:20 pm

Hey, I been bizzy.

Sorta.
Making jewelry chests, Wedding ring boxes, jigs, and what not.
Not snowed in....yet. Had some snow yesterday. About 3/4" in the drifts.

We are getting a more typical snow now. About 18".....between the flakes.
How's the weather in Kitten Kountry? You getting any of this last batch?

JPG40504 wrote:Where ya been? Snowed in????:D Ya musta gotten more than one flake!:eek:

benush26 · Post by **benush26** » Wed Feb 05, 2014 4:23 pm

robinson46176 wrote:I rarely pay much attention to the dial other than to look to be sure that start up speed is reasonable for the setup.
Actual working speeds are sat by ear / feel.
I have spent my life using all manner of machinery from a lot of different occupations and very few of them had any sort of indicator of speed. One of my most common settings is "about like that".

.

Had a very good friend who tuned, fixed, mended, and measured using "or there abouts" as his standard. In reality his "there abouts" were usually closer than a blond hair on a gnats ass (yes another of his favorite sayings).

JPG · Post by **JPG** » Wed Feb 05, 2014 8:13 pm

Gene Howe wrote:Hey, I been bizzy. Sorta.
Making jewelry chests, Wedding ring boxes, jigs, and what not.
Not snowed in....yet. Had some snow yesterday. About 3/4" in the drifts.
We are getting a more typical snow now. About 18".....between the flakes.
How's the weather in Kitten Kountry? You getting any of this last batch?

Got 4" of wet snow over the weekend, got freezing rain last night, thawed by daylight, turned colder, and light snow currently.

Not sure your last batch is 'here' yet. Maybe Farmer saw some of it the other day.