07-14-2007, 04:25 PM
Anybody have an up to date link to or description of Rollie's Dad's Method?
By the way what does OT mean?
07-14-2007, 04:51 PM
Can't help you on the link but OT stands for Off Topic
07-14-2007, 06:29 PM
Having recently been doing it I'll have a shot at expainling it Tyro.
All you really need is a longish piece of stock with a known good diameter. By that I mean it should be round to a matter of tenths so it doesn't throw off your measurements. I used a shaft I scrounged out of a printer.
Chuck the shaft in whatever you got and mount an indicator on your cross slide. Using the carriage to move the indicator, check and record the runout high and low in 2 places. If all is straight the average of those 2 sets of numbers will be the same.
Example: 3-17 on the farthest measurement and 8-12 up close to the headstock tells you the average, or center of the wobble, is 10 in both places. The spindle is inline with the carriage movement even tho the shaft is not.
You must do this in both planes tho. Placing your indicator on top will tell you about vertical alignment only. Placing your indicator sideways will give you horizontal alignment and that's the critical one. If the horizontal's off you'll be cutting tapers. If the vertical's off a little bit due to bed wear or whatever it just affects tool height.
Hope that helps.
Can't help you with a link, but RDM has been discussed several times in previous posts, so a search of the archives ought to turn up information.
In lieu of that, I'll take a stab at describing RDM.
One thing to note is that RDM assumes the headstock is properly aligned on the ways, and you don't need to align the headstock on the ways. Apparently some imports have the capability of shifting the headstock alignment relative to the ways, which adds another layer of complication. But, assuming you don't have that situation....
Get yourself a round, uniform diameter rod maybe 12" long. It doesn't necessarily need to be perfectly straight, but it does need to be round, and of uniform diameter. A piece of something like 1" dia. drill rod would do.
Chuck it in something like a 3-jaw chuck, with NO tailstock support.
Set a dial indicator on the carriage with the tip touching the rod, next to the chuck jaws. Adjust the indicator so, when you turn the rod (i.e. turn the lathe spindle by hand) the movement of the indicator needle is centered on 0. For example, 3-jaw chucks being what they are you'll probably have a couple thou runout, so center the needle travel so it goes from -0.001 to +0.001 as you turn the rod through one revolution.
Without touching the indicator, move the carriage and indicator over to the right-hand end of the rod, and rotate the rod again. The runout will almost certainly be greater at the right-hand end of the rod, but the needle movement should still be centered on 0. For example, it may move from -0.015 to +0.015. If it does, the gods have blessed you and your lathe is properly set up.
More than likely though, the needle movement may go from -0.005 to +0.025 or something. Shim the right-hand leg of the lathe up or down until the needle movement is centered on 0 (-0.015 to +0.015 in this example).
Now, the adjustment will more than likely have messed up the setting at the end of the rod near the chuck. Move the indicator back next to the chuck and adjust the indicator movement to be centered on 0. Then, without touching the indicator, move to the right-hand end of the rod and check. If necessary, shim the leg. Repeat until it looks good on both ends or until you get tired.
07-14-2007, 08:28 PM
This description is very similar to the original RDM:
And there is a link there to the original paper (that link sometimes doesn't work but there is a copy in the 7x12 Yahoo Group's files.) If you can't find a copy of the original paper, email me and I'll send it.
07-15-2007, 09:08 PM
Thanks. As usual, the HSM gang has been very helpful.