Wednesday, Oct 26 2016
Making a carriage stop, part 1
I decided to make a carriage stop. Most of the stop will be made out of aluminum. My design includes a micrometer style adjustment for fine tuning the stop position. I haven’t a clue if this will work.
The last graduation
Graduated adjustment wheel
When I was making the replacement index pin last week I wondered why, thinking I’d never use it. Today I used it. After facing and turning the stock down to 1” in diameter I used the index pin to lock the spindle at 20 evenly spaced points (every 3rd hole in the bull gear) around the circumference.
I scribed a line at each point on the outer edge of the wheel. When that was done I drilled and tapped a 5/16-24 hole. Lastly I parted the machined part off of the stock such that it is a just under a half an inch thick.
One rotation of the wheel will move an adjustment rod 1/24" or 0.041666 inches. Each graduation is 1/20th of that or a bit more than 0.002". If I need more precision than that I’ll look at mounting a dial indicator.
Next up will be threading the rod that the adjustment wheel will control. I could have bought a long enough 5/16-24 screw and cut off the head, but I want to see how well the lathe will cut threads. Or how well I can cut threads. Something like that.
Saturday, Oct 29 2016
Making a carriage stop, part 2
Threaded adjustment rod
This is my second attempt at making the threaded adjustment rod. My first attempt failed because there is way too much flex in the stock (and my lathe) to try to turn down to size and thread something with that small of a diameter that sticks out that far.
For my second try I started with a much longer rod held in the chuck and supported by a live center on the other end. Why longer? Because I needed excess on the right end of the rod to make room for my tooling. This lathe wasn’t designed for modern tool posts. The tail stock ram only extends an inch and a half (or is it an inch and a quarter).
That made testing for “doneness” difficult. I couldn’t test fit the adjustment wheel as I was cutting the threads. Instead I eyeballed depth using a rule. My eye was close enough. The adjustment wheel and rod are finished. Next up is the body of the stop.
Wednesday, Nov 2 2016
Making a carriage stop, part 3
Note to self: When making design changes to a part be sure to check that the changed design fits.
Functional carriage stop
Originally the adjustment wheel was going to be 3/4" in diameter. I changed it to be a full inch and adjusted other dimensions to fit. What I didn’t do was think how the adjusted dimensions would work when attached to the lathe. As a result the adjustment rod is a bit too far out from the lathe bed. Only half of the rod makes contact with the carriage. It works, but barely. If I make another I’ll fix this.
The stop is functional at this point, but not complete. I need to mill a slot the length of the adjustment rod and add key to the body of the stop so the adjustment rod can’t rotate when turning the thumb wheel. Right now I have to hold the end of the rod with my fingers to stop it from turning.
I don’t have a mill, drill press, or band saw. Well, I have a band saw but it is a portable unit suitable for cutting small stock. I found I can hold it vertical in a vice and use a clamp to hold the trigger on and carefully pretend it is a stationary band saw. That, drilling several extra holes, using a hand coping saw, and lots and lots of filing got the job done. It’s not pretty, but it works.
Thursday, Nov 3 2016
Making a carriage stop, part last
Make do mill
As mentioned above I don’t have a mill. I do have some end mills that I can use in my lathe. The part that needs a slot is about the same size as my lathe tooling. That means I can hold it with a toolholder plus a bit of aluminum shim to keep the lock screws from damaging the threads. It worked well enough. The key is to take lots of small cuts. Slow, but functional.
Drilled and tapped
The last step is drilling and tapping a hole for the set screw that acts as a guide to keep the spindle screw from turning as adjustments are made. I didn’t have any 6-32 set screws and local hardwere store didn’t have any as long as I wanted. For now I’m using a 6-32 button head screw.
It works… but adjustment is not as smooth as I’d like. Sometimes it’s hard make changes. I’ll play with things to try to make it better. In the mean while it does the job I want it to do.