drill press math

Leroy

Well-known Member
Been so long loosing all my math so need help. On a drill press to use a 1725 RPM motor driving a 12" diameter pully connected to a 22 tooth sprocket on same shaft driving a 45 tooth sprocket into a 30 tooth sprocket that turns the shaft the chuck is mounted on what size motor pully do I need to get the bit speed down to a hundred RPM or 150 RPM. Only plan on using this press for 5/8" up to 1" bits so I need a slow speed. My supposedly good drill press from TSC 15+ years ago on the slowest speed is faster than I would like (think around 600 rpn) for 1/2" bits and I run it on that slowest speed all the time for all bits, think they call it a 16 speed and it is only fast, extra fast and out of this world fast. This one that I want to get going is one that you could either put a motor on or use a hand crank.
 
with the pulleys and sprockets you give, you would need a 1" pulley for slightly more than 100 rpm at the chuck.
 
Looks like I need to use a jack shaft to reduce speed more as about a 2" pully would be about as small as I could get so if I would use say a 2 1/2" pully on the motor what would I need to use on that jackshaft. Using the smallest pully avaible that I think would be an inch and a half to much belt slippage. And Thanks.
 
I have a similar need to slow down my drill press. My plan is to take an old 1/2" Sioux hand drill that I bought for next to nothing and install it in place of the original motor.
The Sioux turns over about 600 RPMs - about 1/3 of the 1725 the original turns.
 
I have a Jet 16 speed ( I think) floor drill press and it ranges from 200 RPM up to 3500 or so. I use the high speed setting with a sanding disk when I am building violins and mandolins, and the low speed setting is almost low enough to drill larger holes like you want to but a bit slower would be better. I have a jack shaft but have not been able to figure out a handy way to mount it since it would have to be vertical and attached to one side of the top of the drill press. What size is the pulley on your motor, and could you make it any smaller?
Zach
 
(quoted from post at 19:26:13 07/24/13) Been so long loosing all my math so need help. On a drill press to use a 1725 RPM motor driving a 12" diameter pully connected to a 22 tooth sprocket on same shaft driving a 45 tooth sprocket into a 30 tooth sprocket that turns the shaft the chuck is mounted on what size motor pully do I need to get the bit speed down to a hundred RPM or 150 RPM. Only plan on using this press for 5/8" up to 1" bits so I need a slow speed. My supposedly good drill press from TSC 15+ years ago on the slowest speed is faster than I would like (think around 600 rpn) for 1/2" bits and I run it on that slowest speed all the time for all bits, think they call it a 16 speed and it is only fast, extra fast and out of this world fast. This one that I want to get going is one that you could either put a motor on or use a hand crank.


The formula is: Output Rpm = Motor Rpm x (Driver/Driven) x (Driver/Driven) x (Driver/Driven).

Example 1) If you use a 1" pulley on the motor and a 12" pulley on the chuck we have; Output Rpm = 1725 x (1/12) = 144 Rpm at the chuck. As previously posted, 1" is a little small for a v-belt motor pulley - to prevent slippage you could go with a cog belt.

Example 2) Using a 3" pulley for the motor and the sprocket sizes you mentioned, we have; Output Rpm = 1725 x (3/12) x (22/45) = 211 Rpm for the shaft to which the 45 tooth sprocket is attached.

From your post I was not clear how the 30 tooth sprocket was to be used. If it is to form another gear reduction set then simply insert the (driver/driven) tooth ratio into the above formula.
 
Is it reasonable to use a rheostat to slow the press rather than modifying the machine? I confess I'm not an electrician nor machinist but I've seen many applications where rheostats are used to control motor speeds.
 
(quoted from post at 08:18:39 07/25/13) Is it reasonable to use a rheostat to slow the press rather than modifying the machine? I confess I'm not an electrician nor machinist but I've seen many applications where rheostats are used to control motor speeds.

I have a nice floor drill press, about 16 speed, by switching 2 v-belts. It is not hard, but I just get tired of constantly switching them.
What I would like to do is put a Variable Frequency Drive on it.
But they are not cheep, and it only takes a few seconds to switch belts, but that seems like a pain.

And I'm not sure how well a VFD would work on a drill press.


Dusty
 
I see a typo in my orignal post. 30 tooth was supposed to be 38 tooth. My good press is a 16 speed Ironshith with a 4 grove pully on vertical shaft motor, and a jackshaft with a 5 grove the same as the drill post and as near as I can tell the speeds are 720 rpm up to 3250 rpm. What I am trying to work on is what some would call a post drill that could be mounted on a wall and turned with a hand crank on a horsiontal shaft. That horsiontal shaft has a 12 " pully-flywheel on one side for a horsintal shaft motor with the 22 tooth sprocket on the same shaft and that 22 tooth sprocket turns a 45 tooth sprocket that in turn turns a 38 tooth sprocket set to make a 90 degre change in direction from horisantal to vertical that is on the shaft the chuck is mounted on. The good drill press is what they call a 16MM and is a floor mount unit. Just runs way to fast for a 3/4" bit that I need to use in making hitch plates for this machinery I work on. The motor will just be an old flee market motor. The complete unit will probably not see much over a hundred holes a year if that much.
 

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