Going to look at a 1944 12CK… what to look for?

[Sellers Machine Co]

Very sweet Monarch. I see it is a 700 rpm machine which may be a little faster than normal for that model. Maybe others familiar with CK can chime in as to spindle bearings and top end. My 60 was a 700 rpm machine and I speeded it up for smaller stuff with no problems. I find that 1000 rpm on a Monarch is plenty fast and gives a very good finish with carbide inserts. I believe that Tailstock4 here suggested synthetic oil for old Monarchs as the oil flows through the pipes and meters more easily so the same weight oil quiets the machine and allows for somewhat higher rpm if wanted or needed.

I intend to try that when my standard ISO68 oil gets old so no real first hand opinion.

Dave

I read somewhere that these could be ordered up to 1,000 rpm from the factory, so anything up to that point is safe! I’ll have to look into speeding mine up.

 

[Ultradog MN]

I read somewhere that these could be ordered up to 1,000 rpm from the factory, so anything up to that point is safe! I’ll have to look into speeding mine up.

My CK is 1000.
My friend's KK is also.

 

[rabler]

I read somewhere that these could be ordered up to 1,000 rpm from the factory, so anything up to that point is safe! I’ll have to look into speeding mine up.

Three options there:
1) Changing the motor and drive pulleys.
2) New motor with a higher RPM rating.
3) Installing a VFD to increase RPM of the motor.
Mine was stock something like 560. I went from a 6 pole motor to a 4 pole motor, roughly 1200 -> 1800 rpm on the motor, and used a VFD, so I can get a bit over 1000 RPM on mine. Had to adapt the pulley to a slight smaller motor shaft, both were 3 HP motors but newer ones tend to be smaller with smaller shafts.

 

[Sellers Machine Co]

Three options there:
1) Changing the motor and drive pulleys.
2) New motor with a higher RPM rating.
3) Installing a VFD to increase RPM of the motor.
Mine was stock something like 560. I went from a 6 pole motor to a 4 pole motor, roughly 1200 -> 1800 rpm on the motor, and used a VFD, so I can get a bit over 1000 RPM on mine. Had to adapt the pulley to a slight smaller motor shaft, both were 3 HP motors but newer ones tend to be smaller with smaller shafts.

What does upping the motor RPMs do to all your feeds and threading settings? Do you have to go back and recalculate everything, since the data plates on the machine are no longer accurate? I guess if you used a VFD you could set it back to factory speed to use all the factory settings.

 

[rabler]

What does upping the motor RPMs do to all your feeds and threading settings? Do you have to go back and recalculate everything, since the data plates on the machine are no longer accurate? I guess if you used a VFD you could set it back to factory speed to use all the factory settings.

The threading and feeds stay exactly the same, those are determined by the gear ratio between the spindle speed and the leadscrew/feed rod speed. The RPM plate for the gears no longer matches.

 

[Sellers Machine Co]

The threading and feeds stay exactly the same, those are determined by the gear ratio between the spindle speed and the leadscrew/feed rod speed. The RPM plate for the gears no longer matches.

Awesome, thanks!

 

[rabler]

I guess if you used a VFD you could set it back to factory speed to use all the factory settings.

Maybe I'm foregoing the advantages of a VFD, but my VFD is set up with a rotary switch that selects 1x, 1.5x, and 2x of the RPM plate. I can pretty easily calculate those factors in my head. A 4th position on the switch selects "potentiometer". It normally stays in the 1.5x position. I rarely use the pot. I found that having to set the speed by gear selection forces me to focus on learning and getting a feel for speeds rather than randomly twisting a pot. Mounting a tachometer would probably be even better. And adding a brake resistor setup, etc. It is on the list, but my round 'tuit list is longer than my day.

The motor was swapped from the original 1200 RPM to a 1800 RPM (6 pole to 4 pole). The 1.5x position sets the VFD to 60 Hz, so the motor runs at its optimum speed. The 1x position is 40Hz and the 2x position is 80Hz, neither are stressing the motor's RPM/torque range. Due to the limited number of input pins on the VFD, I had to use a couple of diodes with the rotary switch to encode the 4 positions to two VFD inputs.