Stain Dipper Machine – Lathe Work

In the Stain Dipper Machine, we have a top pulley which is mounted on a 10mm shaft that is seated in 10x26x8mm bearings.  In the last post on this topic, I showed the pulley holder assembly.  In this post I’ll show the pulley and the final assembly.

Here is the finished pulley, made from a 1″ long by 1.5″ diameter piece of brass.

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Here is the pulley mounted on the top of the machine.  This is a satisfying point in the project because of all the ways this could have been solved, we chose an elegant, smooth, and accurate one.  You can’t buy this specific part anywhere in the world – we designed and made it just for this purpose.

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Here is a picture of tapping the pulley for a M5 set screw.

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This is a picture after the first operation was complete.  Now we need to turn it around in the lathe, recenter it, and finish the other side.

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Here is a picture of the part in the lathe.  Notice the difference in surface finish?  The shiny area is freshly cut.  The dull area was original surface.  The semi-dull area was shiny just an hour before, but oxidization got to it that quickly.

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A view of the spinning 4-jaw chuck and quick change tool post.

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Stain Dipper Machine Top Pulley Assembly

One of the key components in the Stain Dipper Machine is the top pulley assembly.  It is crucial that it normalizes the unspooling location of the cable so it does not put lateral forces on the slider rod below.  To this end, we designed and created 3 components out of UHMW (Ultra High Molecular Weight Polyethylene).  It’s a nice plastic to work with, and super tough.  It cuts like butter but has a lot of strength too.  This is a 10mm hardened shaft with two bearings pressed into the UHMW.

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Here is a picture of the 3D model.  As you can see I haven’t trimmed the shaft yet.

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Shave a bit here and there.

A friend of mine needed a bushing assembly for his street bike to be reduced in width by about 0.230″.  Having a 1930’s South Bend Lathe in my shop, I naturally said “come on over”.

My respect for machinists just went up a few notches (it was already high).  I’m also glad I got a 4 jaw chuck for the lathe instead of a 3 jaw.

4-jaw chucks allow you to hold irregular work and precisely center it. The process for doing so can be tedious, but it’s a good feeling when your indicator reads in at less than 0.001″ variance from side to side.

This little project was fun for a few reasons.  The assembly comes apart into several pieces.  The little ring has multiple inner diameters used for different things, so it needed to be machined carefully on both sides.  Holding small and irregular parts is a challenge.  But seeing it all come together was great.

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