Been thinking about this Grizzly DRO for my lathe

[rodm1]

I think you could piece together a nicer one but you will be happy with that.

 

[Ischgl99]

One point of Stefan's video was not so much two small cuts, but only two medium-sized cuts instead of a big cut followed by several shavings. His point was that the small cuts will be difficult to maintain a good finish, but the one large cut will cause tool and workpiece deflection that will undermine accuracy.

A DRO is really required for that strategy. The dial on my old South Bend lathe's cross-slide is pretty small to read anything smaller than about half a thou, and the main strategy for dials like that without a DRO is cut, measure, cut, measure, cut, measure, with the last cut being a thou or two or maybe even a spring pass using sharp HSS cutters rather than carbide inserts.

But I doubt I've made much of anything very large that needed better than 4 tenths accuracy. The cheaper DRO's with 5-micron resolution can't get better than 2 tenths except by luck, and that's assuming the scale is really accurate. And all of those scales have an expected accuracy over a relatively long length that is somewhat less than the specific resolution.

Even with a DRO, accuracy takes real work and skill.

Rick "not as old as my lathe" Denney

Agree on the first point, he did say you could do 3 or 4 finishing passes instead of two, the important point was they need to be a consistent depth of cut so the cutting forces are similar so that you get an accurate measure of how much to take on the next cut. How deep you take your finishing passes will depend on your lathe and cutting tools being used, so what works for me might not work for someone else.

This strategy can be done with dials successfully, Stefan did it that way in his video, and I did it that way before getting my DRO. The DRO definitely makes it easier though, especially if the lathe has small dials. I’ve never run a South Bend, so I don’t know how that compares to my lathe.

Even with a DRO, accuracy takes real work and skill.

100% agree!

 

[rwdenney]

This strategy can be done with dials successfully, Stefan did it that way in his video, and I did it that way before getting my DRO. The DRO definitely makes it easier though, especially if the lathe has small dials. I’ve never run a South Bend, so I don’t know how that compares to my lathe.

South Bend increased the size of the dials at some point, but well after 1946 when my 14-1/2 was built. The dials on mine are 1.something inches in diameter, and with an 8-pitch screw, show 0.125 in a full rotation (mine reads in radius distance, not diameter). The hash marks are quite close together. Machining to a thousandth is really about the limit of those, but I can usually interpolate to 2 or 3 tenths. Gotta be religious about backlash, of course. I found an unused screw and replaced the nut, so my cross slide backlash is only about 6 thou, but that's a lot when chasing tenths.

I've also used the compound trick, by rotating the compound to 60 degrees (30 degrees off spindle axis). That cuts the measured readings on the compound dial in half. The compound screw is 10-pitch, so it reads 0.100 in a rotation, and at that angle, it's really 0.050 with each mark being half a thou. It's almost like adding a vernier scale to the main dial, but it slows the process down quite a bit and you also lose Z-axis accuracy if you are indicating on the carriage, as I usually am.

All that is just so much easier with a DRO, and I feel the desire to install one on my lathe rather strongly because of that.

The scales on Stefan's lathe, even the cheapie in his earlier videos, are very much larger in diameter, maybe 75mm or more. And they have a nicer and newer satin chrome finish. And a scale that's easy to zero, which mine does not have.

Rick "but people made accurate stuff with those old lathes" Denney

 

[Ischgl99]

The dial on my lathe is 2.5”, I can definitely see that being a challenge with the SB. I had a DRO on my mill for years, but just added one to my lathe a couple months ago, I’m kicking myself for waiting so long. Maybe this thread will be the push you need to get the DRO

 

[Janderso]

I programmed my tools and played with it, but feel the same way that I will likely make a mistake with it, so not sure how much I will actually use it. I wish the DROs had a display on the screen with tool number so you know which one is currently active. I didn’t see that on my D80 either, it seems like it would be easy for them to implement.


I was having the same trouble with my 3 year old lathe lol. There is some deflection when taking a cut even with new machines, so taking it in steps can be more accurate. Stefan Gotteswinter did a video on taking two smaller finishing passes instead of one deeper one to improve accuracy. For your example, you would take a 0.050” diameter cut, measure what the actual diameter was, then compensate for the difference for your final cut. That is if you need better accuracy than 0.0004”! Lol

Do I need better accuracy than 4 tenths?. I think that falls into the chasing my tail realm. With a good old lathe I am happy with .001”.

We agreed the tool library and tool offsets would probably cause more mistakes. I remember this video. Tony does a great job.

 

[Janderso]

South Bend increased the size of the dials at some point, but well after 1946 when my 14-1/2 was built. The dials on mine are 1.something inches in diameter, and with an 8-pitch screw, show 0.125 in a full rotation (mine reads in radius distance, not diameter). The hash marks are quite close together. Machining to a thousandth is really about the limit of those, but I can usually interpolate to 2 or 3 tenths. Gotta be religious about backlash, of course. I found an unused screw and replaced the nut, so my cross slide backlash is only about 6 thou, but that's a lot when chasing tenths.

I've also used the compound trick, by rotating the compound to 60 degrees (30 degrees off spindle axis). That cuts the measured readings on the compound dial in half. The compound screw is 10-pitch, so it reads 0.100 in a rotation, and at that angle, it's really 0.050 with each mark being half a thou. It's almost like adding a vernier scale to the main dial, but it slows the process down quite a bit and you also lose Z-axis accuracy if you are indicating on the carriage, as I usually am.

All that is just so much easier with a DRO, and I feel the desire to install one on my lathe rather strongly because of that.

The scales on Stefan's lathe, even the cheapie in his earlier videos, are very much larger in diameter, maybe 75mm or more. And they have a nicer and newer satin chrome finish. And a scale that's easy to zero, which mine does not have.

Rick "but people made accurate stuff with those old lathes" Denney

I too struggled with my 1941 13” South Bend. The dials were so small! Several videos exist showing the upgrade to larger dials.

Stephan is amazing. He is a professional with very accurate machine tools in his home shop.
I love watching him make those crazy accurate small parts.

 

[Ischgl99]

Do I need better accuracy than 4 tenths?. I think that falls into the chasing my tail realm. With a good old lathe I am happy with .001”.

We agreed the tool library and tool offsets would probably cause more mistakes. I remember this video. Tony does a great job.

For most stuff, 0.0004" is more than good enough, but for things like bearing seats, bushings, etc., it is good to be able to do better. I often practice using the techniques for the best precision so that when I need it, it's second nature. I recently started a side business like you and would like to be as precise as I can be so I can actually make money on a job instead of being in hobby mode.

I watched Tony's video when I was trying to set up the tool library, it helped me understand the Chinglish instructions better. He is my favorite YouTuber, I wish he posted videos more often, but that must take a ton of effort to make those.

I'm a bit jealous of Stefan's Weiler lathe, I was at IMTS shortly after I started doing machining and saw them in person, beautiful lathes. If I win the lottery, one of those is getting ordered before my wife can say no new tools!

 

[Janderso]

For most stuff, 0.0004" is more than good enough, but for things like bearing seats, bushings, etc., it is good to be able to do better. I often practice using the techniques for the best precision so that when I need it, it's second nature. I recently started a side business like you and would like to be as precise as I can be so I can actually make money on a job instead of being in hobby mode.

I watched Tony's video when I was trying to set up the tool library, it helped me understand the Chinglish instructions better. He is my favorite YouTuber, I wish he posted videos more often, but that must take a ton of effort to make those.

I'm a bit jealous of Stefan's Weiler lathe, I was at IMTS shortly after I started doing machining and saw them in person, beautiful lathes. If I win the lottery, one of those is getting ordered before my wife can say no new tools!

Yeah, Stephan lives in Germany? He has opportunities for high quality machine tools that I bet are better than ours.
That Weiler caused me to check the company out. Yes, good stuff at a very high price.

 

[Ischgl99]

Yeah, Stephan lives in Germany? He has opportunities for high quality machine tools that I bet are better than ours.
That Weiler caused me to check the company out. Yes, good stuff at a very high price.

Yes, he lives in the central part of Bavaria in Germany. I lived in Germany for 7 months during training at one of my employers, the equipment they have there is top notch, but you certainly pay for the quality!

 

[GT-6 Racer]

Lots of good machines here too, my 1971 Monarch 30" 10EE will still easily hold a few tenths over a foot. It has a Newall DP700 with microsyn5 scales. I only ever set tools up when i am running repeat parts that require several tools. I turn the compound all the way in tight to be non-moving as possible. Then I set up all the tools i need and the workpiece zero that matches. Then I treat it like a manual tool change CNC. I order the tool numbers same as the operations and just cycle through them. It really speeds up repeat parts and isn't too hard to keep straight. I never try and reuse tool settings for another part at another time. Just start over from scratch on each setup. Just remember if you move the compound, it's all over ... For normal manual one off operations i don't set anything up, just go one at a time too. It's worth getting comfortable with it if you make any repeat parts.

Oh, and as far as the Germans go, of course I do love my Deckel FP3. What a wonderful manual mill, holds amazing tolerances and so rigid. But God help you if you need parts.

If you want to see some unbelievable German machine tech check out Kern.

KERN Microtechnik | CNC machining centers and shop

CNC precision machining centers and contract manufacturing made in Germany by Kern Microtechnik - operating successfully for over 60 years

en.kern-microtechnik.com

wunderbar!