Wednesday, December 9, 2015

Craftsman 109 Lathe - New Homemade Spindle

I  have known that the spindle on my lathe is old and worn out. I am not sure if it is bent, but I like to replace it. There are spindles available on eBay and Home Shop Supply. They run for about $100. But where the fun is if I just bought it.

There are people who has made the spindles themselves. For example, this gentleman in SHDesigns made one from tool steel, and has a page for it. But he turned it on an Atlas/Craftsman 12x36. I don't have a machine of that size or accuracy. All I have is a semi-working Craftsman 109. And even if it cuts, I am not sure if I can make the finishing smooth enough for the bearing surface.

I have been thinking and search for a while. And one day, I realized something. We all know that the spindle size of the Craftsman 109 is 0.551". That is a strange number. I have seen people doing things in strange numbers, but there has to be a reason. And it turns out that 0.551" is 14mm. The all American Craftsman has a metric heart. How interesting is that.

So all I got to do is to find a grounded 14mm rod, and that could be my new spindle. But what about the collar part? I have spent quite some time thinking about it, and there are a few ways I came up with. I did a few experiment to decide the precision of my cut and measurement, and decided that I can bore the hole precise enough for an interference fit (or shrink fit), with my BBQ stove as heating source (no need for a propane torch).

So here we go. First I got the 14mm rod from eBay. It is grounded 1144 steel. Even though it is not as hard as tool steel, I figured that it will do for me now. The piece I got is 24 inches long, just enough to make three spindles (the original spindle is about 7-1/2" long).

So I cut a piece of 12L14 that is about 3/4 inch long, and bored a hole that is just one thou smaller than the spindle rod (which measured to be 0.550"). For some reason, I can not even bore a smooth surface in the collar. But I figured that this would be a good thing here, as it would grab tighter when the two surfaces are shrink fit together.

Before I shrink fit, I made a wood jig (that is nothing more than a large enough hole drilled for about 1 inch deep). That's how much I like the spindle to stick out. And then I put that collar piece on the BBQ stove. After a while, I took it out, put on the wood jig, and stick in the spindle piece. I even brought a hammer, in case I will have to force it in. But it slides right through with a light tap. I kind of worried if I have machined them too close, but it turned out beautifully when everything is cooled down.

Next I put it on my lathe to finish the backside of the collar. The rest of it can be machined when the spindle is on the lathe.

The next challenge is to get the groove for the Woodruff key. For this I just used my Dremal tool with a disk shaped cutter. It is a bit larger than the original, but it works its way in just fine.

Here are the new spindle and the old spindle show side-by-side. As one can see, I left a bit more material on the new spindle, as those will be cut down in the future when fitting the chucks. Plus I like to have some safety margin to give my shrink fit more surface to grab on.

The old spindle is shown here. As one can see, it has been worn out quite a bit on its bearing surface. I guess that this spindle might have never been replaced since the lathe is first sold in late 1940s. It is an old lathe.

Now the spindle is put on the lathe in its place, and nose of the spindle is cut down to 0.5 inches, ready to be threaded. The spindle nose on the 109 lathe has a 1/2-20 thread. It is great that I have fitted my lathe with all the necessary threading gears so I can cut those threads in place.

Because these threads are so close to the end of the ways, we need to be very careful in setting it up. I happened to have grounded a v-shaped cutter that is tilted to the right. So as we can see here, I can cut pretty close to the register surface and still have room for the indicator wheels.

Cutting the threads are largely uneventful. I did have a few mistakes when the gear pops out. But I got it realigned easily. I finished the thread with a die. As always, that is not an easy work, and took significant force at the end. The die set I have is a cheapo set from Harbor Freight. Maybe I will need a better die set someday.

So finally, here is my new spindle on the lathe. All home made cheaply and proudly on the Craftsman 109 lathe I have.


Anonymous said...

I am enjoying watching your pilgrimage with the Craftsman lathe.


Adam Li said...

So far it has been great fun.

drf5n said...

Yours looks like a nice fix, but someone refitted my Craftsman 109 with a spindle that's 0.750 at the bored-out front bearing, 0.544 at the back, threaded 7/8-9 UNC on the spindle and chuck, and poured the oil holes full of babbitt.

It doesn't leave much of an upgrade path.