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Lathe dro users

killswitch505

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#1
Can you guys tell me what y'all use diameter or radius? From what I'm reading both are correct but I would like to grasp the most common way of doing things. I mean with out a dro I'm already thinking if I take a .010 cut I removed .020 from the diameter of the part. Sorry this might be extremely newbie but I'm new
 

JimDawson

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#2
The dial on most lathes reads radius, so you divide by 2 to take some amount off of the diameter. You can do the same thing with a DRO. I just got my lathe DRO a few weeks ago and I still haven't figured out set it for for diameter :) Doesn't really matter, I have been dividing by 2 for about 50 years.
 

killswitch505

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#3
Thank Jim. I've only been doing it for 8 months but that's what I've been doing thinking that's what I'm going to stick with
 

mksj

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#4
Usually diameter in my experience, it is the actual amount of material or diameter size that you are ending up with. This is one reason on the crosslide, they usually specify 1 micron scales as opposed to 5 micron as you would loose to much resolution. In diameter mode the the DRO doubles the actual scale reading (so a 1 micron scale you get a 0.0001" resolution, 5 micron scale is 0.0004). I started out with radius, but for me on the lathe I wanted to know what I was cutting to or finished diameter, I also made more goofs with radius mode. On most lathes I have used the manual crosslide scale reads diameter. I will also do a cut, measure the diameter and then reset the DRO to the measured diameter, this helps me get down to a few ten thousandth resolution in my final diameter if needed. But I guess like anything it depends on what you are use to.
 
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darkzero

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#5
With the DRO, I use both modes, I switch back & forth constantly depending on the operation. A lathe specific DRO has a radius/diameter button, a glance at an LED indicator tells me which mode I'm in. A push of the button allows you to change back & forth quickly without having to go into the settings. Some universal DROs have the R/D button as well. I prefer a lathe specific DRO for the lathe since there's less clutter not having all the mill functions that are not needed but not a big deal.

Before having a DRO, I prefer to use indirect dial for the cross slide, 1 division on the dial is the actual travel & is what would be removed from the radius. It's just easier for me when the dial reads the actual DOC like on the compound slide & dials on a mill.

I'm not sure what the ryhme or reason is but on most asian import lathes that I have seen the cross slide dials are indirect reading. The larger old American lathes I've used (16x & larger) had direct dials where as the smaller American lathes had indirect dials. But that doesn't really mean anything as far what the "standard" was, could have just been what those manufacturers for those lathes chose to use. I don't think there is a standard for dial types.
 

BGHansen

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#6
I have a TPACtools.com DRO on my G0709 lathe and only use Diameter mode. I typically measure the diameter of the work before turning (if it has a smooth finish), then advance the cutting tool under power until it scrapes the work. Then press the "X" key and punch in the diameter. Make a light pass to load everything up (account for flex, backlash, slop in the cross feed nut, etc.), take a mic check and reset the DRO "X" if need be. Same thing for boring. If it's a critical dimension, I take a mic confirmation check when getting close.

If I need to take a diameter down a known amount (i.e. 1.000" down to 0.750"), I could zero out "X" on a tool scrape, then advance to -0.250" in Diameter or -0.125" in Radius. Or punch in 0.250" in Diameter mode and take it down to zero.

I hope I'm describing my set up correctly?!?! According to my DRO manual I'm in Diameter mode but really can't tell you for sure. All I know is my DRO reads the diameter of the work so I'm assuming I'm in Diameter mode.

I got so used to using the cross feed dials on the lathe over the years that frankly I'm hit or miss turning on the DRO for diameter work. However, I use it ALL of the time for "Z" work. Really nice to face off the work, zero out the "Z" (or set a "Z" dimension) and know exactly where you're at on the longitudinal position.

Bruce
 

Wreck™Wreck

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#7
The DRO is independent of the lead screw, it attempts to measure true position.
The dial on a lead screw measures position by dividing the screw lead at the dial, a lead of .100" requires 10 revolutions to travel 1.00" so if the dial has 100 divisions each is .001" this will yield .002" on the diameter on the X axis of a lathe.
If you divide the dial 200 times the position moves .oo05" per division or .001" on the diameter in X on a lathe.
If you have a reliable DRO you will never use the dials again, using diameter mode does not require dividing by 2 in the X axis resulting in fewer mistakes. Most modern machines have no hand wheels at all and if they do they are not divided and are used to jog the machine around using the DRO.

For example this new Trak mill that we got several weeks ago has hand wheels (not yet installed in the photo) that are not connected to the lead screws, they are encoders that control the servo drives and are not divided.

Use the DRO and ignore the dials.
 

Wreck™Wreck

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#8
If I need to take a diameter down a known amount (i.e. 1.000" down to 0.750"), I could zero out "X" on a tool scrape, then advance to -0.250" in Diameter or -0.125" in Radius. Or punch in 0.250" in Diameter mode and take it down to zero.

I hope I'm describing my set up correctly?!?! According to my DRO manual I'm in Diameter mode but really can't tell you for sure. All I know is my DRO reads the diameter of the work so I'm assuming I'm in Diameter mode.

I got so used to using the cross feed dials on the lathe over the years that frankly I'm hit or miss turning on the DRO for diameter work. However, I use it ALL of the time for "Z" work. Really nice to face off the work, zero out the "Z" (or set a "Z" dimension) and know exactly where you're at on the longitudinal position.

Bruce
Also known as Work Shift, it moves the tool position globally which means that all of the stored tools are moved the same amount, maintain the diameter closely because this is fixed, the 0.00 Z changes with every different setup and job.
 

RJSakowski

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#9
I tend to use diameter mode on the lathe. The reason being that in touching off the x axis on the lathe, measurements are usually made with a micrometer or caliper measuring diameter. I will first turn a reference cylinder and measure that diameter with a micrometer. Then I set my x axis DRO to that diameter. Now all DRO diameter readings reflect the actual diameters being turned. No math involved and less chance of making a stupid mistake.

It is true the the readout resolution is reduced in diameter mode but if you think about it, .001" in radius mode is equivalent to .002" on the diameter anyway. I have Yuriy's TouchDRO installed on my lathe. His readout has the option of showing four decimal places. The iGaging scales have a native resolution of 10 microns or .0004". In changing the DRO to diameter mode, the DRO just does an internal x2 multiplication so my DRO increments by .0008". This gets me to less than a thousandth on the diameter. For anything closer, I wouldn't rely on the DRO anyway but cut and verify with a micrometer.

For those with the 5 micron glass scales, you will be able to resolve no better than .0004" on the diameter regardless of whether you're in radius mode or diameter mode. If you need better resolution, the only recourse is to go with a 1 micron scale.
 

Wreck™Wreck

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#10
This lathe that I use nearly every day displays all inch dimensions to 4 decimal places except thread lead which is 6 decimals, I find this absurd.
Angular values are also 4 places, go figure.
 

JimDawson

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#13
The dial on most lathes reads radius, so you divide by 2 to take some amount off of the diameter. You can do the same thing with a DRO. I just got my lathe DRO a few weeks ago and I still haven't figured out set it for for diameter :) Doesn't really matter, I have been dividing by 2 for about 50 years.

OK, using the lathe today, so I decided to sit down and read the book for the DRO. I didn't see anything in there that told how to switch between diameter and radius. But... I have 1 micron scales, so by setting the DRO X axis resolution to 2 microns, the readout is now correct for radius. May not be the right way to do it, but it works fine. ;)