How to read bandsaw speed?

[AR1911]

I am modifying a bandsaw to slow the speed down.
Other than doing the math - motor speed X pulley ratios etc - how can one determine the blade speed?
Is there a way to read it directly?

 

[jumps4]

this could be good i have an old heavy upright bandsaw i'd like to fix for metal
steve

 

[jumps4]

a hand held tach would give the rpm of the blades pulley then multiply that by the circumference of that pully would give inches per minute right?
steve

 

[poptops]

There is a way to read it directly. Well sort of directly. And, you will have to set it up initially. See it this relates to what you are looking for.....
If you will tool over to the sherline site using this URL www.sherline.com/rpmgage.pdf you will find an RPM gauge some clever gentleman made to attach to his mill spindle to read RMP directly. This is the kind of gauge we used to lay on a record player to check rpm. The only difference for you is that you will have to draw up a table to convert the measured rpm, to inches per second.

Indicated Revolutions per minute X 3.14 X inches of diameter = inches/second
60 second per minute

 

[jumps4]

ok i'll try this
lets say the motor rpm is 1750
measure motor pulley say 3"
measure other pulley say its 6"
divide 6 by 3 gives you a ratio of 2 to 1
so the blade pulley speed is 1750 divided by 2 or 875rpm
take circumference of the blade pulley x 875 and you have inches per minute
i think thats how its figured
steve

 

[jumps4]

i'll have to look at my motor speed i'd like to use that upright for metal also
steve

 

[jumps4]

I am modifying a bandsaw to slow the speed down.
Other than doing the math - motor speed X pulley ratios etc - how can one determine the blade speed?
Is there a way to read it directly?

sorry ar
i'm not reading the post correctly you said no ratio math i must be past my bedtime sorry
steve

poptops method works well i did that before

 

[AR1911]

I have one of those optical tachs. I was looking for something similar, or a way to adapt it for this use.
The suggestion to use that on the driven wheels is probably close enough, had not though of that.

I know how to calculate the ratios. I'm thinking of changing to a variable-speed DC motor.

 

[Tom Griffin]

Just put a mark on the blade and time how many seconds it takes to make one trip around. Then multiply by 60 to get inches per minute and divide by 12 to get feet per minute.

Example:

If your 120" blade takes 10 seconds to make one revolution (120/10) then multiply by 60, 120/10*60=7200/10=720, and divide by 12, 720/12=60 feet per minute.

There's still a little math involved, but not as much as measuring and calculating pulley ratios and motor rpm.

Tom

 

[Bill Gruby]

Any way you do this some math will be involved. The way Tom has shown seems the easiest.

"Billy G" :thinking: