Wednesday, November 18, 2015

Craftsman 109 Lathe - Spindle Adaptor 3/4-16

Using tailstock to start a straight tapping
To make the lathe usable, I will start with the chuck. First I would need to get a chuck that is shorter. It looks like that all the plane back chucks stick out too much because of the extra space taken by the back plate. So the one that would fit well would be the screw mount chucks. I happened to have have read about the 3/4-16 adapter for Taig chucks in Dean's website. So I put in an order to purchase one of 4-jaw chucks from Taig, and getting ready to make the adapter.

Finishing tapping on a vise
To start out, I have cut out a piece of 12L14 round rod. For my weak lathe, it seems that the only steel I can cut at this time is the free machining 12L14. The rod is held in my old 3-jaw chuck, and it is faced and drilled a through hole to about 15/32. Then the hole is tapped with a 1/2-20 tap. The tap was held in a drill chuck from endstock to start the thread straight. It went pretty well initially, but soon it become really hard to turn. Maybe it is because that I don't have a sharp enough tap, but I have to take it out from the lathe to be held on a vise. This is different from what Dean did on his page. Everything looks so easy there. Another thing that I did differently is that I didn't turn the outside down in this step. Part of the reason is because I am not sure if my lathe can turn well with the chuck it has. Well, I am fortunately I didn't, because holding it in a vise will ruin the finish, and it did slip pretty badly. Like all my projects, I always have to go through some rough patches along the road.

Then the piece is thread on the spindle nose and faced. Since the thread on the nose did not go all the way to the register surface, a few threads need to be bored away. I don't have a boring bar, so I have tried to grind a drill bit to be held on tool post as a boring bar. I have tried it on aluminum just to make sure it works. It did. But when I put it on use on steel, it turns out did not cut as well. Maybe I didn't grind the cutting edge well enough. But I ended up just enlarge the hole with the 1/2 drill I have to get it against the register.

3/4-16 Adapter
The picture to the left is the piece mounted on the nose ready to be turned down. A hole is drilled on the back for inserting a bar to remove the adapter if it gets too tight. The front 1/2 in or so is turned down to 3/4 in size. The turning down was so smooth, and it cuts like butter. Turning steel has never felt so good with my mis-aligned chuck. That further confirmed to me that it can work well if I can bring it closer to the nose and the spindle.

As I mentioned earlier, I was able to get the thread cutting of the lathe working. So I got that ready and start threading it. Contrary to Dean's experience, I was able to cut the entire length with the threading indicator mounted. This is the first real thread I am cutting, so I have also bought a 3/4-16 die ready to finish it. I really have no idea how deep it should go, and learnt my share of lessons there. I thought I got it deep enough, and tried it with the die. In the process, I have removed the tool and soon realize that it would not be in the same place when I put it back. Fortunately I have the die ready, and  I would finish the thread with it.

That turned out to be another tough operation I have to drive to the maximum that my little vise can handle. In that process, the surface is destroyed again, which I have to turn down afterward to clear the deep marks. But all in all, I have a cool looking adapter ready to mount my Taig chuck (which I purchased for this modification).

So here is my new chuck, sitting nicely on the lathe ready for the next project.


Anonymous said...

You are probably aware that Sherline makes components that also fit the 3/4-16 thread. Their PN 1040 3.1" dia. 3-jaw chuck has a very short compact design, and hence, a low overhung weight...and also has the nice "Tommy Bar" system of tightening and loosening...though they are a bit expensive. However, they are very high quality.

Also, I would suggest that Sherline (and Taig) users can help the most in helping you with issues related to tool chatter, tooling and techniques. This is because those small lathes (and more so with the Sherline) are limited to moderate cuts due to their diminutive size. As a result, the users have learned quite a bit about alternative tool grinding methods, and also lathe speeds to adapt to their small size. As an example, look carefully at the tooling and methods used by YouTube user Luiz Ally aka Tryally.

It is quite amazing what he is able to accomplish with the small Sherline lathe. Of course, he is also using CNC and the Sherline is a DC motor driven variable speed lathe but most of his unique cutters and methods are transferable to your lathe as well.


Adam Li said...

Thanks, Hans. The Sherline chuck looks nice but is expensive. Since it is a hobby for me, I would take this as a learning experience, even though the time spent versus money saved does not even make to the minimum wage here.

The Tryally video is amazing. I agree that the Sherline would work much better as a computer controlled conversion. Maybe one of the days I will get time to do something like that on my Craftsman.

Anonymous said...

The Taig 3-jaw is only $68 and is nearly as thin as the Sherline...certainly much lighter than your current 3-jaw and with much less overhang distance. However, you would have to use your 3/4-16 adapter as you do with the Taig 4-jaw whereas Sherline sells a 3-jaw with the 1/2-20 thread.


Adam Li said...

Thanks, Hans.

One interesting thing I found is that with the new spindle in place, my 3/4-16 adapter is no longer concentric with the axis. Turning down the register face does not help. I guess my old spindle might have too much bent that is now built into the adapter I made on it.

The screw type chuck, as nice as I like them for the small overhang, is not as easy to adjust as the plain back chuck is. Maybe I will need to make a new adapter someday.