I WILL Prevail

I almost had a machining project today, but it looks like I may have to use hand tools instead.

I have a tractor. It has a bucket. There are brush forks on the bucket. They attach with turnbuckles that tighten chains around the bucket.

A turnbuckle (AKA “bottle screw” or “stretching screw”) is a tube with internal threads on each end. One thread is right-handed, and the other is left-handed. Screws go into both ends. When you turn the tube, both screws go in or out at the same time.

At some point in the past, someone with good intentions and not a lot of knowledge applied something like a Vise Grip to one end of one of my turnbuckles. There are matching gouges on two sides of it, showing where the tool was attached. I assume the purpose was to grab the tube and turn it. A pipe wrench would have been better (but still bad) because it wouldn’t have compressed the tube as much. I think. Anyway, it appears that the tube was narrowed slightly by the pressure, and this made it very difficult for the screw to go in and out. Because of this, I could not tighten the turnbuckle properly. I could only turn it so far, and then it became impossible.

I put off fixing this because I wanted to use the lathe. I wanted to grind a 60° threading tool, put it on a bar, run the bar into the turnbuckle, and follow the threads to remove material. This may not be the smartest way to fix the part; a tap would be faster. I wanted to use a machine tool, though. I’ve been deprived of machine tools for so long, I want to use them for everything.

Today I took the part off the tractor, mounted it in my bench vise, and used a breaker bar to remove the bound screw. That’s how tight it was. I had to push so hard, I had to be careful not to turn over my heavy workbench. When I got it apart, I was left with the turnbuckle body, which is the tube part. I chucked it in the lathe, and I found that the runout was something like 3 thousandths, which is fine. There was a lump on one side that went up to maybe 7 thousandths, but because it was only in one area, I assumed it was an anomaly I shouldn’t take into account.

Once I got the part chucked, I saw that it was very hard to see inside it. The part is black inside and out. It will be hard to put a cutting tool inside it and see well enough to register it in the existing thread.

I went to Ebay and ordered a used tap, just for the purpose of fixing the part. It will run me about $12. If I end up using it, the whole job should take under 15 minutes. The tap gives me a plan B. Once I’m done with it, I should never need it again, but $12 is a great price for fixing this part, and it never hurts to have extra cutting tools. I don’t know what a machine shop would charge to fix it, but I would have to drive all over and find someone who had the right tap, so I think going to a professional would be stupid even if it were free.

I may still use the lathe. It’s possible to line a tool up with an existing internal thread. I’ll just have to play around with it. Because it’s so dark inside the tube, I’m thinking of painting the inside. That would make it easier to see. One does not ordinarily paint things before machining them, but this is kind of a bubba job, so I don’t have to be persnickety about it. All I need to do is scrape maybe 10 thousandths out of the part, and it should function again.

I should be all set now. If I can’t make the lathe work, the tap will be here in a few days, and I’ll get the job done. It will be nice to have the fork attached properly for a change.