|
|
Hi,I am restoring an old drill press - interested in an estimate of the slowest speed config with pully - belt setup. Wondering if this logic makes any sense - motor speed is 1750rpm - using the diameter ratios of motor pully to drill pulley - is the estimate of drill bit speed approximated reasonably? i.e. motor pulley 2.75", drill pulley 6.5" - ratio of .42 - therefore drill speed .42 X 1750rpm ~ 735 rpm?thx
Reply:You have to convert the diameter to circumference first then do your ratio. And they need to be the theoretical diameter numbers not the actual OD's of the pulleys
2.75 in = 8.63 inches6.5 inches = 20.42 inches
Reply:Thx Ronsii - I thought about the linear travel (circumference) and then did the ratio - it appears to be the same at .42 - figured with desiring an "estimate" only would be OK - ultimately wanted to determine I'd be OK to drill out 1/4" and under thickness carbon steel pieces - on occasion - seems like I will be OK. Thx for your comments.
Reply:Yeah, I just always find it easier to use linear/circumference numbers as a lot of times I will matchmark the pulley and belt then rev it an measure the actual travel just to see the real numbers
and in the past I have inadvertently made some errors when doing it by radius/diameter
Reply:
Originally Posted by ronsii
You have to convert the diameter to circumference first then do your ratio. And they need to be the theoretical diameter numbers not the actual OD's of the pulleys
2.75 in = 8.63 inches6.5 inches = 20.42 inches
Reply:
Originally Posted by John Bartley
You don't have to convert to circumference.If you want "exact" numbers, you have to know the diameter of the pulleys "where the belt rides". Once you know that it's just diameter ratio, just like the OP calculated.
Reply:
Originally Posted by John Bartley
You don't have to convert to circumference.If you want "exact" numbers, you have to know the diameter of the pulleys "where the belt rides". Once you know that it's just diameter ratio, just like the OP calculated.
Reply:
Originally Posted by John Bartley
You don't have to convert to circumference.If you want "exact" numbers, you have to know the diameter of the pulleys "where the belt rides". Once you know that it's just diameter ratio, just like the OP calculated.
Reply:Just guessing...translating to circumference might make it easier to relate cutting distance, since the cutting distance changes as the drill not diameter changes for a given rpm. Just thought about that after ronsiis post.
Reply:Screw it. Get a VDF!
Now, in all seriousness. Your calculations are ok and Oscar's clafirication is spot on.What drill press are we talking about that gives you a +700rpm's slowest speed? Waaaaaaaaaay to high for metalworking (in any reasonable drill diameter).Mikel
Reply:
Originally Posted by Mikel_24
Screw it. Get a VDF!
Now, in all seriousness. Your calculations are ok and Oscar's clafirication is spot on.What drill press are we talking about that gives you a +700rpm's slowest speed? Waaaaaaaaaay to high for metalworking (in any reasonable drill diameter).Mikel
Reply:
Originally Posted by danielplace
VFD !!! 3 phase baby !!! Infinite !!!You'll still be using the pulleys even with a variable speed VFD. It is still going to need the ratio changed for different jobs.
Reply:
Originally Posted by danielplace
VFD !!! 3 phase baby !!! Infinite !!!You'll still be using the pulleys even with a variable speed VFD. It is still going to need the ratio changed for different jobs.
Reply:
Originally Posted by Mikel_24
Screw it. Get a VDF!
Now, in all seriousness. Your calculations are ok and Oscar's clafirication is spot on.What drill press are we talking about that gives you a +700rpm's slowest speed? Waaaaaaaaaay to high for metalworking (in any reasonable drill diameter).Mikel
Reply:
Originally Posted by jfk92
...- I find a number of charts citing rpm speeds above 700rpm as "OK" for mild steel, smaller hole diameters and thinner plate... |
|
发表于 2021-9-1 23:17:42