[atomarc]

For the belt drive..I ordered a J section, 4 rib poly belt just to see what it looked like in person. It's the right scale for the machine and will handle the HP just fine. I have read the poly sheaves are easy to make so I'm going to give that a go. The spindle sheave will be a tap fit onto the OD of the splined shaft on the spindle and will also fit down into the ID of that large upper bearing. This plan seems like it will stabilize the upper end of that long splined shaft, giving it more rigidity.

The driven pulley OD will be based on the available room for the driver OD pulley, and such that it give me a ratio of around 1.44:1..but also allows me a center distance for a off the shelf belt.

These are my plans..we'll see what reality brings! The timing belt drive was my first choice but my son has read there is more noise associated with it and above all, I'll like this little Chinese bucket of bolts to run smoothly and quietly.

Stuart

[atomarc]

No pictures today, but an update nonetheless. I started making the 'top hat' for the power draw bar today and things went sour in a hurry. The top of the spindle on these machines is threaded 20mm X 1.0. My design called for my top hat to screw onto these threads which would also secure the poly belt pulley to the spindle. After hours of fussing it finally became apparent that the factory threads were cut slightly out of line with the spindle axis. How this happened is beyond me! This wouldn't allow the top hat to seat flat on the pulley and also resulted in about .015 of lateral run out.

As Nick (my son) stated..if nothing else is done right on this conversion, the spindle has to be perfect. It must be balanced, true and quiet. The Chinese thread job was not going to let that happen.

So...3/4" X 16 TPI is real close to the existing size, but not much would be left of the threads if I merely threaded over the existing ones. My plan is to tig weld up the threaded portion, then single point it 'dead nuts' in the lathe with the new 3/4" X 16 thread.

I'll take my camera down to the shop and get some pictures of this when I do it.

Stuart

[atomarc]

I had success re-treading the end of the spindle!!! It was quite the task setting up the spindle in the lathe and dialing everything in perfect. 3/4 - 16 threads were single pointed after the spindle was setup in the lathe. Now time to proceed with the top hat portion that will thread onto the newly corrected spindle threads. Also picked up some 4140 for the clamping part of the power draw-bar as was as the draw-bar its self!



(newly "minted" threads!!!)









(top hat in progress)






(top hat progressing....)





(soon to be "clampy" part of draw-bar)





(the thing that says draw-bar on it....)



Thanks!!!

[gcofieldd]

Hey man,

I feel certain the thread on top of your spindle was M20X1 (metric) and not 3/4-16, so it might not have been messed up...

[atomarc]

Hey man,

I feel certain the thread on top of your spindle was M20X1 (metric) and not 3/4-16, so it might not have been messed up...

You are absolutely correct...the thread on the spindle WAS 20mm X 1.0...but any more. The factory thread was somehow cut out of parallel (?) with the axis of the spindle and would not allow a threaded piece to sit flat on my poly pulley. I dialed the spindle in on the lathe and cut a new thread...3/4" X 16 and now everything is square, plumb and proper.

How those factory threads were cut out of whack is beyond me. I machined a disc and single pointed internal 20mmX1.0 threads in it, screwed it onto the spindle...it wobbled like a drunken sailor.

Stuart

[lcvette]

You are absolutely correct...the thread on the spindle WAS 20mm X 1.0...but any more. The factory thread was somehow cut out of parallel (?) with the axis of the spindle and would not allow a threaded piece to sit flat on my poly pulley. I dialed the spindle in on the lathe and cut a new thread...3/4" X 16 and now everything is square, plumb and proper.

How those factory threads were cut out of whack is beyond me. I machined a disc and single pointed internal 20mmX1.0 threads in it, screwed it onto the spindle...it wobbled like a drunken sailor.

Stuart

If you are going to run it at high rpm, I recommend assembling everything with a tool holder in place and turn the whole shebang true to the spindle center, collet, drawbar, bellvilles and all, makes a big difference when that top pull hat assembly is concentric!

Chris

Sent from my QTAIR7 using Tapatalk

[atomarc]

Chris,

Yes..that's what we're doing, although I'm picking off the OD of the bearing fits for my reference as the hole for the factory draw bar going up through the spindle looks like it was made with a rat tail file. I think my maximum spindle speed will be just over 4000 but I still want everything as true as I can get it. I don't think it's a wise idea to mess with the Bellevilles in any way. Being a spring, they're tough to begin with and they have smooth polished edges that need to remain intact...I wouldn't touch them myself.

Stuart

[lcvette]

Chris,

Yes..that's what we're are doing, although I'm picking off the OD of the bearing fits for my reference as the hole for the factory draw bar going up through the spindle looks like it was made with a rat tail file. I think my maximum spindle speed will be just over 4000 but I still want everything as true as I can get it. I don't think it's a wise idea to mess with the Bellevilles in any way. Being a spring, they're tough to begin with and they have smooth polished edges that need to remain intact...I wouldn't touch them myself.

Stuart

Doesn't effect them in the least, its the outer edge and they machine like butter. Helps in aligning them, once they are aligned they pretty much stay there unless you unbolt the stack. Certainly your peragative, but it's worthwhile having Everything aligned perfectly. A little unbalance up that high will make the spindle wobble and it will show in your finishes. It also will make keeping everything up there aligned more difficult as the stack will want to shift around and like you said the draw bar bore isn't a ground opening with a tight fit so there is room for everything to shift. The top hat hopefully has a good close tolerance fit to help and the drawbar should fit snug to the belville ID to keep them aligned but without them binding when compressed I know your figuring this out on your own, but sometimes it's wise to stand on the shoulders of those who have blazed the trail previously. 😁 May save you some time and frustration.

Chris

Sent from my QTAIR7 using Tapatalk

[gcofieldd]

You are absolutely correct...the thread on the spindle WAS 20mm X 1.0...but any more. The factory thread was somehow cut out of parallel (?) with the axis of the spindle and would not allow a threaded piece to sit flat on my poly pulley. I dialed the spindle in on the lathe and cut a new thread...3/4" X 16 and now everything is square, plumb and proper.

How those factory threads were cut out of whack is beyond me. I machined a disc and single pointed internal 20mmX1.0 threads in it, screwed it onto the spindle...it wobbled like a drunken sailor.

Stuart

Ah, gotcha. You are doing good stuff. I am enjoying your build. I wish I had a Bridgeport at home...makes things a lot easier and cheaper.