Announcement

Collapse
No announcement yet.

3-in-1 lathe pulleys

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • 3-in-1 lathe pulleys

    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 ...

  • #2
    Looks like one of those setups where there's only one "sweet spot" to tighten both belts, due to the way the shaft is off centered. Do you have a pic of the way the belts originally ran?
    25 miles north of Buffalo NY, USA

    Comment


    • #3
      No, unfortunately. I did manage to get it going, but it still felt less than optimal, as one belt was still tighter than the other. I don't know that pics would be any good anyway, as the sweet spot might be different depending on what speed is set ...

      I did have a thought though, shouldn't the pulley be able to slide a little more freely inside the slot? Once it is in there, it is very difficult to move, as it is easier to pull it out, stuff it in another slot and try to reclock it...

      Comment


      • #4
        I always wondered what 3 in 1 oil was made for.
        Now I know.

        -D
        DZER

        Comment


        • #5
          I don't know about that ... I am thinking I will try wire wheeling the slot, then if it doesn't slide easily enough in there after that, maybe some light dremeling?

          Comment


          • #6
            You shouldn't need to clock the pulley, It should swivel freely on the stud. At least that is the way my Shoptask works. Dennis

            Comment


            • #7
              You say it is the same as the Grizzly G9729, but an apparent likeness does not necessarily mean that they are identical in all aspects. I have a Central Machinery 20" drill press that looks a lot like a 20" Grizzly and I bought a Grizzly part to use on it. However, it turned out that the spindle OD on the CM is about 3/4" smaller than that on the Grizzly so I will need to make a spacer ring before I can use it. I suspect that the Chinese factories are willing to make changes for the bigger importers and Grizzly specified a better set of bearings in the spindle than CM did and that required a larger OD.

              Anyway, a nice thing about Grizzly is they provide the manuals for their machines available on-line for download. It may not give you any help, but for what it is worth, here is the link to the Grizzly G9729 manual.

              https://cdn0.grizzly.com/manuals/g9729_m.pdf

              I could not tell from your post weather you were talking about the lathe or the mill head pulleys. I looked in it briefly for the belt changing instructions for both the lathe and mill heads but neither looked a lot like your photos.

              Perhaps Bolton also has the manual available. Or a phone call to them may help. Of course, you may already have the manual and it was not of any use.

              Good luck on this.
              Paul A.
              SE Texas

              And if you look REAL close at an analog signal,
              You will find that it has discrete steps.

              Comment


              • #8
                It looks like this is one of the arrangements where you have 2 belts and 3 pulleys. 2 pulleys (the motor and the final driven) pulley are fixed. The middle pulley should be free to move in 2 axes - vertical & horizontal. They do this by providing a slot and an eccentric mounting bolt. The bolt should slide freely in the slot. It doesn't matter which way around the offset bolt is relative to the axis of the free pulley (closer to the fixed pulleys or further away), both will work, just find what works with the belts that you have. So first get the bolt to slide freely in the slot, assemble it and fit the belts. Push the sliding pulley as far as possible away from the other 2 pulleys, the eccentric bolt will let both belts tighten. I don't think that separate raised portion is of any relevance - they could just have left the whole thing flat. It might give slightly more even clamping, but I wouldn't worry about it. Not my favourite pulley arrangement, but it works. Ian
                All of the gear, no idea...

                Comment


                • #9
                  BINGO IAN ! ! !

                  The offset on your pulley that is shown in the upper middle and upper right part of the picture montage is supposed to swivel this way and that to equalize the pressure of the belts. THAT is your "play" that you need to make the whole thing work As such you want it to be able to swing quite freely.

                  BUT, there is a limited range of swinging freedom with this design and it may be that you need to swap the belts for some setups if they are close to but not the same size. Or you might need to pick up a belt that is a slightly different size. The goal is that you want to see the offset be sitting at an angle that is fairly close to bisecting the angle between the two belt axes... Or bisecting the angle formed by the three shafts where the tensioning pulley axle is the point at the apex of this angle. Hope that makes sense.... Only when the dog leg design is within a few degrees of splitting that angle will the tension to be nearly the same for both belts.

                  Another issue I see is that there is no way to pull tension on the belts then tighten the locking lever. I think that is why the smaller pad is there. If you think about it and you pull out on the pulley with the locking lever and not your hand on the inside then the pulley will tilt towards the center of the "V" of the two belts. And then when you tighten the lever it will tilt away back to square using that little pad as a lever fulcrum and pull the tension into the belts. Hardly an ideal design because it relies on the user knowing how to do this.

                  On the other hand if you do the obvious thing and pull on the pulley itself while tightening the lever you are tilting it the wrong way and it will pull down and slack one or both belts.

                  Pulling directly on that lever to hold tension and tighten at the same time would be a PITA. Perhaps replace the washer, which looks way to small anyway, with a tensioning strap. I'm thinking a piece of 1 1/2 x 1/8 or thicker flat bar that is long enough to extend out where you can grab the end of it and pull. On the locking stud end you drill a hole and this pulling strap replaces the washer. On the other you drill a similar hole but include a piece of 1/2" round as a "T" handle. It might be welded or it might just be a piece of all thread with two nuts and some soft tubing slipped over the threaded stubs. But it would let you pull firmly with one hand to make that "levering shoulder" work for you and get more tension on the belts as the shaft pulls in and straightens up.

                  Plus don't forget the idea of switching the belts to aid with getting that offset angle to be close to bisecting the angle between the two belts as that is what you want to get even tension.
                  Last edited by BCRider; 05-10-2020, 01:46 PM.
                  Chilliwack BC, Canada

                  Comment


                  • #10
                    Hi Everyone, I really appreciate your replies. This has been driving me bonkers.

                    Originally posted by mixdenny View Post
                    You shouldn't need to clock the pulley, It should swivel freely on the stud. At least that is the way my Shoptask works. Dennis
                    That was my initial thought as well! I should just be able to pull the belts tight by hand and cinch it up with the fastener which pulls them tight, right? I ended up thinking to clock it because it would tighten up the bottom belt first, preventing any further movement and not allowing for the top belt to tighten.

                    Originally posted by Paul Alciatore View Post
                    You say it is the same as the Grizzly G9729, but an apparent likeness does not necessarily mean that they are identical in all aspects. I have a Central Machinery 20" drill press that looks a lot like a 20" Grizzly and I bought a Grizzly part to use on it. However, it turned out that the spindle OD on the CM is about 3/4" smaller than that on the Grizzly so I will need to make a spacer ring before I can use it. I suspect that the Chinese factories are willing to make changes for the bigger importers and Grizzly specified a better set of bearings in the spindle than CM did and that required a larger OD.

                    Anyway, a nice thing about Grizzly is they provide the manuals for their machines available on-line for download. It may not give you any help, but for what it is worth, here is the link to the Grizzly G9729 manual.

                    https://cdn0.grizzly.com/manuals/g9729_m.pdf

                    I could not tell from your post weather you were talking about the lathe or the mill head pulleys. I looked in it briefly for the belt changing instructions for both the lathe and mill heads but neither looked a lot like your photos.

                    Perhaps Bolton also has the manual available. Or a phone call to them may help. Of course, you may already have the manual and it was not of any use.

                    Good luck on this.
                    The parts views show very similar design. It is close enough to where general instructions like changing belts would apply to both machines. Both have the same belt and pulley arrangements for sure. Generally, I have consulted the Grizzly manual for most things because the Bolton one is written in very broken english. I should have taken that as a sign before buying the Bolton. I am sure there are specs that are different here or there, and I don't know how precise Bolton asks for things to be, but I doubt it is as precise as Grizzly apparently is. I was very underimpressed with the milling vise I will tell you that. Once I got a dial indicator, I discovered that the vise was off by over .005" from one end to the other. The table itself was also off by a couple thousanths on one side. I shimmed the table and bought a better vise. I am thinking the fact that bolt doesn't slide freely is just more of this poor QA. My thought is that Chinese manufacturers are plenty capable of making quality parts, it is just that the ones that come out poorly they still sell to distributors who are not too picky. It's too bad. At the time, people all over the internet had nice things to say about Grizzly but Bolton was hardly mentioned. The G9729 was only a couple hundred dollars more at the time too. I just had to save a buck. Oh well.

                    ... I was talking about the lathe pulleys. The mill pulleys are much more straightforward.

                    ... I might call Bolton ...

                    Originally posted by Ian B View Post
                    It looks like this is one of the arrangements where you have 2 belts and 3 pulleys. 2 pulleys (the motor and the final driven) pulley are fixed. The middle pulley should be free to move in 2 axes - vertical & horizontal. They do this by providing a slot and an eccentric mounting bolt. The bolt should slide freely in the slot. It doesn't matter which way around the offset bolt is relative to the axis of the free pulley (closer to the fixed pulleys or further away), both will work, just find what works with the belts that you have. So first get the bolt to slide freely in the slot, assemble it and fit the belts. Push the sliding pulley as far as possible away from the other 2 pulleys, the eccentric bolt will let both belts tighten. I don't think that separate raised portion is of any relevance - they could just have left the whole thing flat. It might give slightly more even clamping, but I wouldn't worry about it. Not my favourite pulley arrangement, but it works. Ian
                    Thanks for confirming that. I will try and smooth/open up the slot a little and see if this makes things any easier. I am hoping this is what has been gumming things up for me.

                    Comment


                    • #11
                      Okay! I figured it out. 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.

                      Click image for larger version  Name:	2Ab-NhHXkRsfWq4_3M48hpFQ2kpC5veG9eJ9GpqeERg3F_n5f-sUAtxQQmDdeiUhE-QAD1D4xQrUXbcNjAKjru9V9MLcwQ1fSvZfkkBX1mAnCkJhlzl14OKQtCzi-4aVIjyZUxzwyz3jjvKWFkJGGp5h4Po0GnIZtHPQEBmP-9M5vgPho0iWu2i4Gg1_yBJwyAtp4z0IiPRbFrVqYQiq_B-CJIrjbbVCFyQJHp1oSeVmkww5WQAjunpkKV07ZhG Views:	0 Size:	137.1 KB ID:	1874293
                      Last edited by aPpYe; 05-10-2020, 04:08 PM.

                      Comment


                      • #12
                        It must be rather UN-like the Grizzly.....

                        The Grizzly has the same eccentric, but it is intended to just swivel to take up the tension. The motor has a tensioning arrangement on it, so with the Grizzly, you move the motor, which pulls the motor belt to tension the idler pulley, and the idler pulley swivels to tension the spindle belt.

                        There is no nonsense of a slot with the Grizzly. The idler shaft pivot is fixed in position, so the eccentric takes up all the movement..
                        CNC machines only go through the motions

                        Comment


                        • #13
                          Originally posted by J Tiers View Post
                          It must be rather UN-like the Grizzly.....

                          The Grizzly has the same eccentric, but it is intended to just swivel to take up the tension. The motor has a tensioning arrangement on it, so with the Grizzly, you move the motor, which pulls the motor belt to tension the idler pulley, and the idler pulley swivels to tension the spindle belt.

                          There is no nonsense of a slot with the Grizzly. The idler shaft pivot is fixed in position, so the eccentric takes up all the movement..
                          Hmm. I am not sure you are talking about the same machine. The parts list on their site illustrates a slot in the "bracing plate" ...

                          Comment


                          • #14
                            Originally posted by BCRider View Post
                            BINGO IAN ! ! !

                            The offset on your pulley that is shown in the upper middle and upper right part of the picture montage is supposed to swivel this way and that to equalize the pressure of the belts. THAT is your "play" that you need to make the whole thing work As such you want it to be able to swing quite freely.

                            BUT, there is a limited range of swinging freedom with this design and it may be that you need to swap the belts for some setups if they are close to but not the same size. Or you might need to pick up a belt that is a slightly different size. The goal is that you want to see the offset be sitting at an angle that is fairly close to bisecting the angle between the two belt axes... Or bisecting the angle formed by the three shafts where the tensioning pulley axle is the point at the apex of this angle. Hope that makes sense.... Only when the dog leg design is within a few degrees of splitting that angle will the tension to be nearly the same for both belts.

                            Another issue I see is that there is no way to pull tension on the belts then tighten the locking lever. I think that is why the smaller pad is there. If you think about it and you pull out on the pulley with the locking lever and not your hand on the inside then the pulley will tilt towards the center of the "V" of the two belts. And then when you tighten the lever it will tilt away back to square using that little pad as a lever fulcrum and pull the tension into the belts. Hardly an ideal design because it relies on the user knowing how to do this.

                            On the other hand if you do the obvious thing and pull on the pulley itself while tightening the lever you are tilting it the wrong way and it will pull down and slack one or both belts.

                            Pulling directly on that lever to hold tension and tighten at the same time would be a PITA. Perhaps replace the washer, which looks way to small anyway, with a tensioning strap. I'm thinking a piece of 1 1/2 x 1/8 or thicker flat bar that is long enough to extend out where you can grab the end of it and pull. On the locking stud end you drill a hole and this pulling strap replaces the washer. On the other you drill a similar hole but include a piece of 1/2" round as a "T" handle. It might be welded or it might just be a piece of all thread with two nuts and some soft tubing slipped over the threaded stubs. But it would let you pull firmly with one hand to make that "levering shoulder" work for you and get more tension on the belts as the shaft pulls in and straightens up.

                            Plus don't forget the idea of switching the belts to aid with getting that offset angle to be close to bisecting the angle between the two belts as that is what you want to get even tension.
                            Hey sorry I didn't notice your reply this morning!

                            Actually, I didn't have much trouble getting equal pressure doing everything by hand. I stand behind the machine, pull it up into position and tighten the fastener/handle on the other side. It works pretty consistently. I don't think I will need any extra leverage, the belts are tight enough to stall the machine when I try to take too much material ...

                            Comment

                            Working...
                            X