Workshop Log

[b.lindsey]

What did you decide on for the vise Stuart ?

Bill

[propforward]

Is it really necessary? Very good question, and one I ummed and ahhed over a fair bit. But as you say - it takes certain variables out of play, and that was the final deciding factor in the end. It was a fairly priced set up, although not inexpensive for sure. But I felt it will expand the capabilities of my lathe, without adfing a smaller machine tool.

[propforward]

What did you decide on for the vise Stuart ?

Bill

I did order a Kurt 4”. Very excited to try it out. Should have it at the end of September.

Maybe I can pop into the Minneapolis factory and watch them make it?

Probably not - although I’d really enjoy that.

[b.lindsey]

Ah great. I guess they are still ramping up production on the 4" version, but you will love it...worth the wait!!

Bill

[propforward]

I’m sure the 4” is much lower demand, but I think it’s the right size for my little mill. I have fiund my bigger vise quite unwieldy - also it’s clamping leaves a lot to be desired. It is incapable of holding work firmly against parallels. 

[propforward]

Adventures in accuracy..................

Today I made a start on finding out the truth about my lathe. I'm sure I'm not the first amateur to just buy a machine tool, assume it was good and start butchering metal, but that doesn't excuse it as an approach. I now want to know where my lathe is, and then see if I can do anything about any errors.

I started with the much celebrated "Rollies Dad" method of measuring alignment. Using a 26" long aluminum round bar (rod) held only in the chuck, I performed the measurements, and found that

At headstock - TIR = 0.002"
Mid way - TIR =  .004"
At tail stock (25.375" from head position) TIR = .003"

Does it seem likely that bed twist could be such that the measurement is worse half way along? Also I wonder if there was some crud on the bar. I think I'll do this again and clean and measure the rod diameter at each position.

According to my acceptance test in the lathe manual, parallelism of headstock axis to the bedways is 0.001" over a 12" length. Based on that these measurements seem encouraging. But I'll return to that.

I then had a try at a test bar. I found a nice piece of 2" steel, and chucked it up, then took a few very light cuts along it.





The diameter of the bar measured

1.4814" at chuck end
1.4830" at mid point (4.5" )
1.4850" at end of bar (9.0")

I must admit that these numbers are better than I had expected (although I had no real reason to expect any particular amount of taper).

While looking through the manual, and investigating the headstock, I was pleased to find that the headstock is equipped with jacking screws, to use in alignment.

So it seems to me that I should be able to take out that 2 thou in 9" taper by jacking the head slightly.

On tuesday I will have access to a machinists level, so at this point I don't think I'm going to adjust anything until I put that on the bed, and see if I can double check the twist that way.

But I wonder if all I'll need to do is adjust the headstock a bit to take out the taper - and then will have a pretty accurate machine (within the realms of the home enthusiast).

I measured run out on the test bar for fun, and got approx 0.0005" at the chuck end, and a bit less than 0.0010" at the 9" end. Not sure what to make of those numbers at this point, but I think the roundness is in spec in comparison to the inspection test report. Probably not much more I can do with that aspect, and I think that is satisfactory.

After that I just busied myself with my new backplates. My lathe has locking dogs on the backplates supplied with it, so spot faced the new ones, and drilled and tapped holes to make use of those.





Fun times! After tea and sammich, and more tea I expect, I'll go and do some more. I think my lathe is accurate enough to start making some of the jig parts I want for my grinding rest, but I'll hold off engine parts for now.

[zeeprogrammer]

If I recall, Rollies Dad needs a straight bar. 26" is pretty long. What was the diameter?

When you turned the steel, was anything holding the end?

I'll be interested to see how you go about checking for twist with the level. I've done it but I don't have confidence I knew how.

[propforward]

Well, according to the blurb, Rollies Dad method specifically does not require a straight bar, since you evaluate the difference in run out. 26" is pretty long, but I felt it would give a good idea of the nature of the whole length of the bed. However, you do need to know the diameter is either the same at each measurement point, or measure the diameter for comparison. I'll repeat it this afternoon, and add that aspect in, since this is a stock bar, it could have variation in it. Or crud on it. It's a 1" dia bar.

From Rollies Dads write up:

"The difference between the "near end average distance" and "far end average distance" is a measure of the misalignment of the spindle axis with the ways."

That means on my numbers near end and far end are 0.0005" misaligned, and the midway point is .001" misaligned (using the means of the TIR per RD method). I'm not sure I could really adjust that out without chasing my tail a lot. But I need to do this again.

I did not support the end of the steel bar - basically I followed the method outlined in my lathe manual, which was very specific about not supporting the bar end. But consequently the cuts must be very light.

I'll post my results as I keep going. Very much a voyage of discovery - quite rewarding in many ways.

[b.lindsey]

Now if they would just make a 2" one for the sherline 

Bill

[RonGinger]

Rollie was a Volvo mechanic. He used to save and pass out all the gas struts he replaced. They were hard and smooth and round. I believe round was the most important requirement.

Its hard to believe how that method is all over the net. Rollies dad would be impressed. A few of  us used to gather in Rollies shop from time to time to just talk shop. His dad lived right across the street and when he saw a bunch of cars he would come over. He had been a machinist all his life, and was then in his late 80's. One day he explained the method to us all, and one guy in the group, Steve Wellcome, wrote it up for HOME SHOP MACHINIST. After it was published Steve got a letter one day with a 20 dollar bill form a guy that said he had used the method and his lathe was straight for the first time.  Later, after the NEMES group was formed (1996) Rollie described the method at a meeting and someone in the group put a write  up on the net. After that it just went nuts and has spread all over the net.

It was fun to be at the start of a legend.

[propforward]

That is very cool that you were there for that. It is astounding how widespread the method is, but more astounding is that it is referred to as "Rollies Dad's" method, which is fitting, and makes me feel good that someone is getting recognized in this way.

I redid my Rollies Dad measurements. These I find more believe-able. Not sure what I did wrong first time - call it set up practice.

This time, I scribed a location at the headstock end, another 12" away, and another 12" away from that. Then measured the diameter of the bar in each location twice, at 90 degrees to each other.

Here is the set up for the vertical test. Horizontal is the same, but with the dial gauge mounted appropriately.





And here are the measurements.



This essentially translates into about 4 thou misalignment over the first 12", increasing to 6 thou misalignment over the second 12" span. Given the nature of measurement and error, it's fair to call it 5 thou per foot.

I was tempted to start shimming, but I think I'm going to have a look using the machinists level first and see how it compares.

[zeeprogrammer]

I may want to trade lathes with you. But I'll wait a bit and see what else you find. 

[propforward]

I may want to trade lathes with you. But I'll wait a bit and see what else you find. 

 

Wait until I've adjusted it first. It might be even worse then!

[zeeprogrammer]

I may want to trade lathes with you. But I'll wait a bit and see what else you find. 

 

Wait until I've adjusted it first. It might be even worse then!

That's my M.O.

[10KPete]

I think you'll be very surprised at how much that rod droops at the end. I don't see any attempts to measure/compensate for that.

Pete