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Thread: Newby question re spindle speeds
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23rd Jun 2020, 03:44 PM #16
The operative word was about 3:1, going by Auscabs measured speeds above, it is about 5.4:1, so I would divide by 5.4. I don't think that Hercus had different backgear ratios withing a model range so it should be similar for your machine.
Sorry for incorrect info about the actual ratio, I grew up with Southbend 9inch lathes (what the Hercus and Sheraton 9in were based on), but haven't been near any of them for 20 yrs, but knew that the backgear needed to be included in the calculations.
I wouldn't worry to much about high precision in the calculations either eg your measured motor pulley diameter was I believe 2.48. These general purpose pulleys were generally made in 1/2in steps in size, rather than to achieve an exact transmission ratio for a task, the motor speed will vary with load applied and you have a maximum 8 speeds available including backgear, so have to try and select the closest one to match your requirements anyway. Your work surface speed will also reduce with each cut made as you reduce the diameter of your work, so even if you calculate an exact speed required and get that speed on the machine, it would be off marginally for the next cut anyway.I used to be an engineer, I'm not an engineer any more, but on the really good days I can remember when I was.
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23rd Jun 2020, 06:47 PM #17
There are differences with my pulleys .
the front ones are the same . I just measured the larges left and smallest right and they match your sizes .
the two on the side are different though . The small on my motor shaft is 3.34”
and my large is 8.36 “.
Im measuring the outside diameter of the pulley . Not trying for the inside of the V . I assume that’s the right way ?
Rob
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24th Jun 2020, 03:19 AM #18Golden Member
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24th Jun 2020, 07:25 AM #19Novice
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