3-in-1 lathe pulleys

[aPpYe]

Hello,

I have a Bolton BT800 3-in-1 combo machine. It is the same as the Grizzly G9729. I use it for hobby stuff and have enjoyed it reasonably well. I have mostly used it for milling stuff, which has it’s own issues, but this question is about the lathe. I have turned a few things on it, but I never had need to change the speed until yesterday. I can't seem to figure out how to tension the belts. Every time I try, I am able to tighten the bottom belt but this loosens the top belt. Is there a correct order or something for positioning or clocking the pulley so I can get both belts tensioned?

I get (I think?) how it is SUPPOSED to work. My thought is that the pulley is initially placed somewhere along the slot, then things are tightened up with the fastener, which would pull the pulley against both belts.

I was hoping someone can explain to me a proper procedure to use when changing these belts around? I have been fighting with this for hours. I even ground a slot into the stud that comes out of the other side of the pulley, which does make it easier to clock the pulley with a screwdriver, but I still can't seem to figure this out.

Okay, so the first picture shows where the pulley stack goes. The second picture is the stack, removed from the machine. Why does it have this extra raised surface on the mounting surface? I don't understand what that is for. The third picture is just a closeup of the mounting surface next to the pulley. The last three pictures are of the fastener that goes on the stud and how it mounts to the other side.

I hope my this makes sense. Theoretically you should be able to see the image above, let me know if you can't ...

 

[AnthonyInMass]

Hi, I have a Harbor Freight 44142 which is almost the same as the Grizzly G9729(the G9729 has a Morse taper in the mill spindle, the 44142 has an R8 taper in the mill spindle).
The pulley drives are identical though between the two brands both for the lathe, and mill though.
I have attached some pics of my lathe pulley drive in hopes that they may be of some use to you. I have changed out both motors on mine with American made motors, however, I retained the original motor mounting brackets.
The raised surface that you indicate is necessary for the eccentric idler shaft to be spaced out enough to clear the sheet metal cover which encloses the lathe drive as it is mounted to the headstock. There is no need to clock it with a screwdriver. The idler shaft should clock itself as it is tensioned in the mounting slot. Also, it would be a good idea to replace the idler pulley bearings on both the lathe and mill with sealed ball bearings at some point.

 

[aPpYe]

Hey thanks for taking the time to respond! I actually figured things out though. Just a few minutes ago actually.

Initially, I was thinking the issue was with the slot. Even with the fastener loose, the pulley would not slide freely along the slot. I took a file (and then, carefully, an angle grinder) to the slot. This did make it slide up and down much more freely, but then I couldn't get either belt to tighten! I cussed a bit and threw my screwdriver into the woods somewhere (I live in the mountains, I am gonna have to go find that now! Its bright orange) ... After some fuming, it dawned on me that opening up the slot had exposed the real problem. While the pulleys were still sliding more or less freely, I still had to break the fastener loose to get it off, it was quite tight. It turns out that the surface of that bolt that slides along the slot is just a little too long. I shimmed it with a washer and can properly tension the belts now.

I figure that the center lines for the belts will not match this way, so I am thinking I will take a grinder to the bolt and carefully take a couple millimeters of material off.

 

[AnthonyInMass]

Glad to hear that your all set.