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How do we know if the belt is too tight or loose on a mill?

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oskar

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#1
My mini mill headstock is a Taig ER16 and it’s driven by a Sherline DCV motor. The distance between the 2 pulleys is 3.5” and when I press lightly on the belt at midpoint the belt deflects about 1/8”.

When the motor runs the belt wiggles more than it should (to my opinion) but I don’t want to tight it more in case the applied force will wear the belt prematurely.

So are any tricks here to know when your belt is too tight or not?
 

Alittlerusty

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#2
If it slips or stalls while taking a reasonable depth cut snug her up abit
 

P. Waller

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#3
I do not know how the collective "We" do it.

A belt tension gauge, used in many industries that employ belt drives, I have never used or even seen one.

https://www.grainger.com/product/OTC-Belt-Tension-Gauge-2TVU6

If you require a fixed limit of parameters as many hobbyists do this is for you, it has a white zone and a red zone on the dial.

The white zone is for loading and unloading only.
 

markba633csi

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#4
The 1/8" deflection is probably about right for that size lathe and belt
mark
edit: I meant mill
 
Last edited:

oskar

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#5
Thank you guys, guess I will just have to play with it and find the correct tension. Good to know that 1/8" is about right

Nicolas
 

Bob Korves

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#6
If it is not slipping it is tight enough, the belt will eventually be damaged if it slips. Too tight and the bearings and belt will suffer.
 

mikey

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#7
Depends. Are you using a Sherline cogged belt? If so, just pull it tight and lock it down. My belts move about 1/8" with moderate pressure. The cogged inner surface grabs well but it will slip if too much torque is applied, which is what it is designed to do.
 

oskar

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#8
Yes Mike I use the Sherline cogged belt and also I have a spare one just in case. Looks like the 1/8” slack is the right number and I will leave it there

Nicolas
 

4ssss

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#9
If the spindle turns, the belt is OK. If the spindle doesn't the belt is too loose.
 
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