Thread: Dimmer switch for buffer for variable speed ?

Im getting a spindle headache !

@mcpell
Thanks. I already bought 4 inch wheels there. I downloaded the file and read it through.

Originally Posted by gssixgun

Formula for calculating surface speed of wheel in SFPM.
SFPM = 1/4 x diameter of Wheel x RPM (revs of spindle per min.)

Rated speed on the buffers is rated as Spindle speed...

Examples of common buffers we use

.25 x 4 x 3450 = 3450 sfpm

.25 x 6 x 3450 = 5175 sfpm

.25 x 6 x 1725 = 2587sfpm

.25 x 8 x 1100 = 2200 sfpm

Dremel

.25 x 1 x 10k = 2500 sfpm


Caswells will also have the most effective application sfpm rate for many of their polishes being used on different metals,


sfpm + pressure + time = heat keep in mind that the grit and media being used changes the equation also...

This seems to be a good rule of thumb and easy to figure but my numbers are larger.

Circumference X RPM = surface speed [Changing from inches to feet divide by 12.]

3.14 X diameter = circumference

3.14 X 6 X 3450 / 12 = 5416.5 sfpm

By your example it is 5175 sfpm.

But is a 6 inch buffing wheel not 6 inches in actual use?

Tim

Originally Posted by 32t

This seems to be a good rule of thumb and easy to figure but my numbers are larger.

Circumference X RPM = surface speed [Changing from inches to feet divide by 12.]

3.14 X diameter = circumference

3.14 X 6 X 3450 / 12 = 5416.5 sfpm

By your example it is 5175 sfpm.

But is a 6 inch buffing wheel not 6 inches in actual use?

Tim

don't know Tim I used the formula from Caswells I figured they knew Buffing wheels better than I did

Why did I read all this ? Oh yeah the variable speed control. **makes note...forget it.****

Not sure I understand you confusion: if the spindle rotates at 3450 RPM, and the wheel is attached to the spindle, then obviously the whel also turns at 3450 rpm The diameter of the wheel does not have anything to do with it unless you want to know how fast the wheel surface is rubbing over your blade. In that case you need the formulas.

For razors, it is better to go as slow as feasible initially, because buffing generates heat, and something as thin as a razor blade heats up awfully quickly.

The calculation that 32t uses is the one I learned a number of years ago. I agree with that.

What you really need is the SFPM to compare different size buffs & rpms.

But to the original question..... I have never tried a Variac but I know that a dimmer type control nor a router speed control will usually not work. However, using a 3 step pulley will give a good speed range and using two of the 3 step pulley system , one on the motor and one on the arbor shaft will give a broad range of speeds. Combine that with different size buffs and you will find the sweet spot of speed when using a 1750 rpm motor.

Hope this helps

@Bruno, My confusion was I thought the RPM's were based of the size Buffer you are buying. Like if you buy 6" buffer the RPM's were based on the diameter of the wheel. I now see that s not so and understand what is being said here.

@Randydance
Are pulleys and pulley driven spindles available for purchase ? So you put a pulley on the buffer motor and run belt driven buffing wheels?
I feel another formula coming.......

I have used Variacs on many motors,without capacitor start,they work,With capacitor start,I do not know.

Take a look at this setup of mine. Just imagine that the motor also has a 3 step pulley.

http://www.flickr.com/photos/randyda...th/8017361174/

Does anybody have a pic using pillow blocks? I have not built mine yet.