Atlas Mfb Thoughts Wanted

[Deadbolt47A]

I have a question that is a bit above my knowledge/comfort level for deciding on my own. I recently bought an Atlas MFB and am in the middle of cleaning it up and seeing what I have and what I need. One of the things I know for certain I need is the counter shaft two groove pulley. That pulley is Atlas part number M1 80B. Atlas nor Sears have any of these pulleys left. I found a “maybe” online today but it was a bit more than I am willing to pay.

My plan is to use two single pulleys and change them out when the need arises until the correct part comes along. The drawing that Clausing emailed me shows the Atlas pulley having an outer diameter as 2 3/8 for the small and 3 ¼ for the larger side of the pulley with a 5/8 bore. 3 ¼ was easy to find but 2 3/8 not so much.

My intention at this time is to go a bit smaller than stock for the smaller pulley, I’ve found some that are 2 ¼ diameter. My question concerns the size of the pulley and the change in the speed of the head-stock. Will running that much smaller pulley on the counter shaft. Change anything enough to hurt anything in the back gear, the chang-o-matic, or the auto feed? I would think that slowing down slightly wouldn’t hurt anything but I’d like to get some opinions.
Thanks in advance.

Eric

 

[Fairbanks]

Eric,
I am very interested in how you work this out as I have the same problem. My mill came with non-original single pulleys on the motor and counter shaft. Both are the wrong size. I would like to get back to the original configuration.

Steve

Sent from my XT1585 using Tapatalk

 

[wa5cab]

Eric,

The short answer is No, it won't hurt anything. It will just run slightly slower. The only two problems may be that when properly adjusted for the higher speed, the belt tension mechanism may not have enough range to tighten the belt on the slower speed. And fitting both individual pulleys onto the countershaft will almost certainly require modifying the width of the smaller pulley or maybe both of them.

One suggestion, if the pulley castings allow, would be to turn down the hub of the smaller pulley, bore the larger one part way through, and press them together to make an assembly the same width as the original. Then drill and tap through the bottom of the pulley grooves for set screws if either or both get either cut off or buried by the modification.

Another thought that might work in conjunction with the first mod is to find a 2-1/2" pulley and assuming that the casting allows, turn the belt groove down to 2-3/8".

 

[Deadbolt47A]

Thanks guys. I just found one for sale that I could afford and bought it. Hopefully it arrives safely and is in as good of condition as it looked in the pictures.
Eric