- Joined
- Jan 2, 2014
- Messages
- 8,853
I found Jim's post, here:
https://www.hobby-machinist.com/threads/not-a-follow-rest.63857/
https://www.hobby-machinist.com/threads/not-a-follow-rest.63857/
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Turning a long, thin, straight bar
- Thread starter ttabbal
- Start date
- Joined
- Jul 19, 2013
- Messages
- 590
It helps a lot to use a tool that cuts on the side, with the cutting edge 90 degrees to the center line of the work. Then all the push is toward the headstock, not sideways causing the work to flex. Make sure that the tool is SHARP(!) and has plenty of relief (edit: also a small nose radius) for effortless cuts. You will be amazed what that does for you. But the real technique here is using AXIAL pressure, and not RADIAL pressure. Joe Pi has a video on that............. well, actually two videos. See if you can keep your mouth closed during these videos...
This is the right way to do it.
- Joined
- Oct 16, 2017
- Messages
- 339
Nice!
Well, took a few tries, but I got a straight turn. Only 0.001 over 16". No chatter, good finish. I'll need to polish it up for my needs, but that's easy. Now I need more stock and hopefully the next one goes much easier. 
- Joined
- Jan 2, 2014
- Messages
- 8,853
Well, took a few tries, but I got a straight turn. Only 0.001 over 16". No chatter, good finish. I'll need to polish it up for my needs, but that's easy. Now I need more stock and hopefully the next one goes much easier.
Excellent!
Got any advice/suggestions not mentioned above?
-brino
The biggest thing I found was to verify the tailstock alignment, and a tiny bit makes a bigger difference than I expected. I had to take a few test cuts and mic them to get it right. DRO was a help as I didn't need to use an indicator on the cross slide. I did need one for adjust the tailstock. And remember that you probably had the DRO in diameter mode, so 1/2 the distance for tailstock movement. Confused the crap out of me the first time I adjusted to match the DRO change I wanted and overshot. For the test, being able to cut the very end, so I got the most support from the tailstock, helped with accuracy.
And I found that the pressure on the follow rest changes the diameter slightly. I actually wanted to be a couple thou under for this application, but dialing in for 0.54 got me to 0.537. A couple test runs can help get a feel for the amount of force on the adjustment screws. It's easy to overdo it and drop another thou or two. My bar is within the spec I need, so I'm happy. Now I need to make another size. But the snow is keeping me from getting more stock. It did polish up nice and smooth, so that's done now.
It's a very different process for me, but was interesting to learn. Increased my understanding of the cutting and deflection forces when I could see it change in real time. I actually experimented with tightening the follow rest while cutting to see the change in size on a test cut. I doubt I'll use the follow rest a lot, but I can see how it will be useful for a few future projects I might want to do. Apparently, you can also use them to cut long threads. I think most of the time I'll be able to use threaded rod, but it's an interesting possibility.
Confused the crap out of me the first time I adjusted to match the DRO change I wanted and overshot. For the test, being able to cut the very end, so I got the most support from the tailstock, helped with accuracy. And I found that the pressure on the follow rest changes the diameter slightly. I actually wanted to be a couple thou under for this application, but dialing in for 0.54 got me to 0.537. A couple test runs can help get a feel for the amount of force on the adjustment screws. It's easy to overdo it and drop another thou or two. My bar is within the spec I need, so I'm happy. Now I need to make another size. But the snow is keeping me from getting more stock. It did polish up nice and smooth, so that's done now.
It's a very different process for me, but was interesting to learn. Increased my understanding of the cutting and deflection forces when I could see it change in real time. I actually experimented with tightening the follow rest while cutting to see the change in size on a test cut. I doubt I'll use the follow rest a lot, but I can see how it will be useful for a few future projects I might want to do. Apparently, you can also use them to cut long threads. I think most of the time I'll be able to use threaded rod, but it's an interesting possibility.