- Joined
- Dec 3, 2017
- Messages
- 2,227
Well I guess that’s it then. The ONLY possible solution is the one you originally suggested….and keep suggesting every time somebody tries to give you an alternative. Sorry I can’t help. Good luck.
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Custom Threaded Chuck
- Thread starter CJ5Dave
- Start date
- Joined
- Jun 12, 2014
- Messages
- 5,135
Having a chuck hold stock off center is not uncommon, many Chinese chucks have that degree of TIR. You can bore a back plate with your current chuck, mount the back plate to your lathe and then true it up. You probably could start with a 2" threaded back plate, turn down the threads and then re-thread to 2-1/8", if you can cut a thread plug another forum member may be able to make one to fit. The same goes for a thread plug, all you are looking for is fitment of the thread. Then get yourself a 3J scroll or 4J independent chuck and mount it to the back plate. It sounds like your current chuck is toasted.
I think the chuck is beyond precise work but I am using it as it is. I will get some mounting plate pics sometime I have more time.
Somebody asked why this has meaning to me. Here is a similar situation. I have had this 1973 Jeep since about 1985. Looked great when I got it, but it got down to no paint, broken windshield, bad tires, brakes locked. Was gonna sell it, but I spent 2 years on brakes, paint, windshield, new tires and wheels good enough to get to Sonic and back. The Sears fiberglass top is worth more than the Jeep, and I have the doors as well. As you can see from the dust it does not get out much but has insurance, tags and new battery. It was our convertable as we did not want a Harley. A buddy begs me to sell it to him everytime we meet. Why is it still here? My wife and I went on our first date in it in 1986 and she asked me not to sell it. Not everything is about new, shiny and pricey.
Somebody asked why this has meaning to me. Here is a similar situation. I have had this 1973 Jeep since about 1985. Looked great when I got it, but it got down to no paint, broken windshield, bad tires, brakes locked. Was gonna sell it, but I spent 2 years on brakes, paint, windshield, new tires and wheels good enough to get to Sonic and back. The Sears fiberglass top is worth more than the Jeep, and I have the doors as well. As you can see from the dust it does not get out much but has insurance, tags and new battery. It was our convertable as we did not want a Harley. A buddy begs me to sell it to him everytime we meet. Why is it still here? My wife and I went on our first date in it in 1986 and she asked me not to sell it. Not everything is about new, shiny and pricey.
- Joined
- Mar 25, 2013
- Messages
- 5,221
The missing pinnon a should not really affect the work holding. If it won't hold the work correctly there are other problems. A scroll Chuck can be tightened correctly by a single pinnon. You probably want to take the chuck apart and post pictures of the scroll and the teeth on the jaws in addition to the other pictures. Yes the Chuck body should run true so it appears to be a problem with that back plate.
- Joined
- Mar 25, 2013
- Messages
- 5,221
One other thing to note here. Even if your chuck is WAY of center (lets say .250") if you grip a piece of stock in this chuck, face the end, bore out the center and then machine multiple features along the length, all of these bores and features will be concentric with each other. They will always be concentric to the spindle axis no matter how the part was gripped. The only part that would be non-concentric is the surface that was gripped by the chuck. In other terms, a chuck that has a huge TIR still turns a perfectly circular part. I am saying this so you can understand how trueing up an eccentric back plate can fix the issue.
I am wondering if your back plate got bend in a crash and also has angular runout. Truing up the back plate would fix all of that.
I am wondering if your back plate got bend in a crash and also has angular runout. Truing up the back plate would fix all of that.
- Joined
- May 3, 2020
- Messages
- 378
You might be better off leaving it alone and just making parts for a while. You'll be a better machinist as time goes by.
If you need an improvement, I don't see how you can avoid cutting threads. There's no reason you can't do it with your current setup.
Someone advised you to make a plug gage, which is good advise. It's practice and you need it to test if you've cut threads deep enough. Otherwise you've got to take off the chuck (with work in place), reverse it so the work is facing the spindle, and see if it will screw on. Do that 5 times fast. Unless you have a crane and time to kill, the plug gage is required.
If you need an improvement, I don't see how you can avoid cutting threads. There's no reason you can't do it with your current setup.
Someone advised you to make a plug gage, which is good advise. It's practice and you need it to test if you've cut threads deep enough. Otherwise you've got to take off the chuck (with work in place), reverse it so the work is facing the spindle, and see if it will screw on. Do that 5 times fast. Unless you have a crane and time to kill, the plug gage is required.
