First off I would like to wish everyone a Merry Christmas and a happy New Year.

I have a SCM/Minimax wood lathe , I was wondering if anyone has some ideas on how I could turn the speed down so I could turn some large diameter projects. I believe the minimum speed is still to fast for turning some larger pieces on this machine.
Thanks for any help.

There are variable frequency drives available from China that are pretty cheap. The catch with slowing an existing motor electronically is it also reduces the available power. An old fashion way would be to install a jack shaft with another set of sheaves to reduce the speed, full power but have to move belts around.

Do you have 3 phase power? If you do, change the motor to 3 phase, then add a VFD. That will get you all the power and torque at low speed.

VFDs used on modern woodturning lathes use a single phase input and 3 phase output. So a 3 phase motor is required. There are other options with a VFD, but price goes up dramatically over the single/3 phase models. No idea what rpm the motor is, but if it's a 3450, you could switch to a 1725.. Finally a jack shaft may be added to reduce the drive gear ratio.

Not sure of your lathe drive but change of either drive pulley or driven pulley would be least expensive way. Speeds you have available should be good for all turning done on the lathe, as long as the blank size is within spec for the lathe and you do not have unbalanced work. I used to think I needed less than my slowest speed until I learned how to get a razor sharp edge on my tools, now I rarely go below 1200 rpm, except for roughing.
A rule of thumb is to divide 9000 by the diameter of the piece to give speed required. i.e for a 18" bowl blank the optimum speed would be 9000/18 = 500 rpm. Which is good for the outside but too slow as you get to the center. With sharp tools speed is good because you get smooth cuts requiring less sanding.

Thanks for all the information, I guess I probably don't need to go slower by the sounds of it. I believe the lowest speed is around 500 so should be good if careful.

Scott, an old guy who did woodturning as a living told me years ago learn to sharpen your tools first, then understand how the tools work, become proficient at spindle work before you do bowls, and finally use common sense when working. It was all good advice, especially keeping tools sharp.
I am presuming you are concerned about a large piece spinning on your lathe.
Then once mounted on the head stock with tail stock in place stand to the side and turn machine on, then stand at the tail stock end and cut from tail stock to head stock. All the force will be directed into the head stock as you true the piece up into the round. And remember keep the tool in contact with the tool rest, face the flute of the tool in the direction of travel, and keep the tool handle close to your body. Dont force the tool into the work and all should be fine. Good luck.