Aligning a mini-lathe

[WobblyHand]

Rollie Dad Method - Spindle alignment on my mini Lathe from Micromark 7x14 - YouTube

I watched this. It was the first video I found. Unfortunately, the video sort of blunders its way through the measurement, but does not show how to actually make the corrections. I measured the error. Now I need to take some of the error out.

 

[WobblyHand]

Now thinking about this... RDM checks for headstock alignment to the ways. The measurements were made at 2 points (actually 4 points, since the horizontal and vertical were done at different start points). But lets say the horizontal and vertical corrections were made, what else needs to be done? (Besides the tailstock, which is its own project - one of the adjuster screws is stuck...) Sometime I need to make a test cut, yes? What else?

 

[addertooth]

Other errors... Chuck mounting plate on spindle and chuck (wobble). Head-stock Bearing play. Mal-adjusted Gibs, which shift more under heavy load, than under light cuts. Tool post flex/slop. Tool flex. Lathe not level in both planes also contributes to errors.

 

[homebrewed]

Here's a description of one approach that was taken to align a mini lathe, which includes the shimming procedure: Lathe Alignment. Among other things, it answers your question of just where the shims are placed.

Examination of your RDM results suggests that you really don't need to worry about your mini's headstock alignment. I bet it's better than mine, and I've been using mine happily for years. There are other components that often are much further out of alignment (like the notoriously-bad tailstock).

 

[Weldingrod1]

Hershey bar foil was half thousandth...
The shims should go between the headstock and the bed: two steel parts.
If you have 0.006" in 15", then 0.0005" on 4" might actually be a useful correction.

I bet you find goo/junk under the headstock!

Sent from my SM-G892A using Tapatalk

 

[Weldingrod1]

You might want to loosen those bolts and see if you CAN rotate the headstock with respect to the ways. In a perfect world there would be perfect, solid contact between the headstock and the alignment features on the bed. In the real world, there might be slop. If there is, you want to shim it solid and move shims around to get solid alignment. You really dont want the headstock alignment depending on friction.

That said, aligned by friction is better than not aligned! You could always align it and then wick some bearing retaining compound or some "after-lock" in there to fix it!

And, yes, tapping is a time-tested machinist alignment technique capable of sub 0.001" work if you have the measuring tools and some practice.

Sent from my SM-G892A using Tapatalk

 

[mikey]

So it would seem my headstock is off by 6 tenths in the horizontal and 3 tenths in the vertical over about 9-1/4". What is confusing to me is the correction. @mikey For a mini-lathe, the horizontal correction would be to partially loosen the 3 bolts #131 that fasten the headstock casting #10 to the bed way #132, and rotate the headstock relative to the bed way? Please state yes or no, sometimes things are not obvious to me - that's why I am asking the question.

How does one move the headstock such a tiny, minute, amount in a controllable fashion? Does one tap the casting with a hammer? Use a lever? I could see myself battling with this for ages, some practical experience would be most helpful.

Typically, the headstock is located on the ways by the angled rail in front or a pin. In your case, it is the rail in front. You would loosen whatever bolts hold the headstock to the ways and see if there is enough play to shift it in the direction you want the headstock to go. If not, then you may need to very judiciously file the contact point under the headstock to allow for the correction.

0.0006" is not a lot of misalignment and for most work you would not notice it. However, on long pieces it will show. How critical this is going to be is unclear at this point. For myself, I would correct it.

Actually, for myself, I would put a 1-1/2" OD aluminum or 12L14 rod in the 3 jaw and stick it out about 4". I would take a 0.010" cut to take off the skin, then take 0.003" to smooth it out and then a 0.001" deep cut all the way down the bar with a sharp, well ground HSS tool set dead on center height. Measure the tail end and the chuck end and see if there is a difference. If there is then move the headstock to correct it without disturbing the rod. After a correction is made, repeat the cuts until any error resolves. I don't use the RDM method or any other method; I use this one because it is self-proving.

 

[WobblyHand]

Here's a description of one approach that was taken to align a mini lathe, which includes the shimming procedure: Lathe Alignment. Among other things, it answers your question of just where the shims are placed.

Examination of your RDM results suggests that you really don't need to worry about your mini's headstock alignment. I bet it's better than mine, and I've been using mine happily for years. There are other components that often are much further out of alignment (like the notoriously-bad tailstock).

My RDM results are a lot better than I feared. To be honest, I thought something was really wrong after I stuffed up my saw arbor. Now I realize I'm just a poor machinist. Hope to get better with time and practice.

My tailstock is off by many thousandths, it's one of my (many) projects to tackle.

 

[WobblyHand]

Hershey bar foil was half thousandth...
The shims should go between the headstock and the bed: two steel parts.
If you have 0.006" in 15", then 0.0005" on 4" might actually be a useful correction.

I bet you find goo/junk under the headstock!

Sent from my SM-G892A using Tapatalk

My numbers are 0.0006", (not 0.006") over 9.25". Would need to be a mighty thin shim. Maybe gold leaf? That is about 0.1 microns, or 4 millionths of an inch. That's really thin. Silver leaf comes at 0.32 um or 0.0000126" thick per sheet. $9.31/2 square feet. (25 pieces of 3.75" x 3.75") silver leaf Gee, this doesn't sound impossible, but it doesn't sound easy either. If all 25 sheets were stacked and the air was smoothed out the leaves would be 0.000315" thick. Sure wouldn't want to sneeze!

 

[WobblyHand]

Typically, the headstock is located on the ways by the angled rail in front or a pin. In your case, it is the rail in front. You would loosen whatever bolts hold the headstock to the ways and see if there is enough play to shift it in the direction you want the headstock to go. If not, then you may need to very judiciously file the contact point under the headstock to allow for the correction.

The contact point might be a section on the angled rail, say on the front edge? (or rear?) Just enough for there to be a tiny movement in the horizontal plane? Would using a diamond stone be better (slower) than a file? How would one shim vertically with a pyramidal way? _/\_ __

Actually, for myself, I would put a 1-1/2" OD aluminum or 12L14 rod in the 3 jaw and stick it out about 4". I would take a 0.010" cut to take off the skin, then take 0.003" to smooth it out and then a 0.001" deep cut all the way down the bar with a sharp, well ground HSS tool set dead on center height.

Have 2" OD 6061 11.5" long, 2.25" OD 6061 x 12" and lots of 1" OD 12L14, 303 and 6061. Is it necessary to shorten the 2" 6061? I have a 16" bed, so it should be able to turn the full length.