.0005 DRO resolution sufficient for Milling Machine?

buffdan

buffdan

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The Excello 602 mill I purchased came with a NOS 2 axis Sargon DRO with display and scales. (never mounted/used) (scales fit for mill)
The scales are glass, and appear compatible with Touchdro.

I am trying to decide whether to sell the entire DRO/Scales/mounting hardware, or keep the .0005 scales and sell the display. I will need Z axis sale as well.
I already have a .0005 scale set on my Bridgeport, which I have found to be sufficient resolution for me. (so far)

But, this will be my last mill and DRO.. Should I go for .0002 resolution.......
Not sure I need additional resolution or..

Any thoughts on this, am I missing the point of needing .0002 resolution?
Thanks for your inputs.
Dan
 
It all depends on the level of work you are doing and the accuracy and repeatability you need. The standard scale resolution for a something like a knee mill these days would be to use 5uM scales and a DRO that would display 0.0002" resolution. it may be that you do not machine to that levels, but it can get you closer to target is say you need a part with 0.001" accuracy. There is also cumulative stacking errors if doing multiple operations.

There is resolution and there is accuracy and repeatability, if you have scales that are capable of a 0.0005" resolution then the accuracy is probably less so something like +/-0.0005 or less depending on the scale resolution/quality, the older scales are probably 10uM. Also this can result in greater error if say one was to diameter mode (on a lathe) and/or in calculation/functions if your DRO is capable of that.

Understanding DRO Scale Parameters

Choice of scales for DIY DRO project will define how well the finished setup performs. Before spending your money, read this article to learn to which parameters you should pay attention and how common DRO scales stack up against each other.
www.touchdro.com

At the cost of new scales/DRO's these days, I would be more inclined to recommend selling your Sargon as a group, they seem to get very good money, in particular id NOS. I would then buy a 3 or 4 axis DRO with scales, and not have to cobble things together.
 
mksj said:
It all depends on the level of work you are doing and the accuracy and repeatability you need. The standard scale resolution for a something like a knee mill these days would be to use 5uM scales and a DRO that would display 0.0002" resolution. it may be that you do not machine to that levels, but it can get you closer to target is say you need a part with 0.001" accuracy. There is also cumulative stacking errors if doing multiple operations.

There is resolution and there is accuracy and repeatability, if you have scales that are capable of a 0.0005" resolution then the accuracy is probably less so something like +/-0.0005 or less depending on the scale resolution/quality, the older scales are probably 10uM. Also this can result in greater error if say one was to diameter mode (on a lathe) and/or in calculation/functions if your DRO is capable of that.

Understanding DRO Scale Parameters

Choice of scales for DIY DRO project will define how well the finished setup performs. Before spending your money, read this article to learn to which parameters you should pay attention and how common DRO scales stack up against each other.
www.touchdro.com

At the cost of new scales/DRO's these days, I would be more inclined to recommend selling your Sargon as a group, they seem to get very good money, in particular id NOS. I would then buy a 3 or 4 axis DRO with scales, and not have to cobble things together.
Click to expand...
Good feedback, thanks
 
Please report back if you connect the Sargon scales to Tough DRO. I also have a Sargon, and am unsure if I can use them with TDRO.

For my use, 0.0005 is good enough. I am rural, and most of the machining is fixing truck and tractor parts or fabricatin things around the house. I just don't have the need (skills?) to get tighter tolerance than that.
 
For a manual mill? Good luck on being able to dial in those numbers and then having everything else dialed in close enough for the higher resolution to make a difference. You can do it. Plenty of people do. I try my best to hit it most of the time, but locking the table axis will make mine move off the number. Trying to stick .0005 is a PIA and .0002 is down to the surface finish. A worn end-mill will throw that number off. I think the scales went that low just because they could, not because they were needed by anyone making parts.

Save the money for accessories, which you will never have enough of and you'll actually use.
 
Repeatability and many other variables combined with tolerance.

Our DRO is that accurate, just try to repeat landing on exactly some number to 4 Decimal places.

Higher accuracy in measurement can result in longer time taken to get to some place.

Example, many years ago in the electronics class, there were power supplies with analog meters as well as some with digital displays.

The labs instructed to set voltages to some voltage, round number voltage, 12 vdc, not 12.5 vdc.

Those who had analog Meyers always finished first with same results as they did not waste time to chase the exact number as the digital was 2 Decimal places.

The analog just has a needle with scale.

Your collection of stuff is worth more to someone who needs that specific item.

There is likely a set of parts as a kit that is possibly better for your application.

The DRO seems to drift as some work is done...nope, it is showing wear in the system.

At hobby level the accuracy does not need to be 4 Decimal places, you need a solid machine and reliable scales that are as accurate as you need but consistent in their measurement and are repeatable.


Sent from my SM-G781V using Tapatalk
 
With dovetail slides the clearance needed to operate freely is more than the 0.0002 on the DRO. This adds up when the X axis is mounted on two other dovetail slides liks a Bridgeport. These fine scales are for jig borers and other high accuracy machines with less play in the slides like a flat + vee sliding system.
 
I have 1um (.00005") resolution scales on my mill. Most of the time I ignore the last 2 digits, reading only the thousandths. When I want extreme accuracy I go to the tenths, working in .0002" increments. I have successfully worked to that accuracy on one-off parts. However, I haven't ever needed or tried, to do a multi part run at that level of accuracy. The fifth digit to the right of the decimal point that reads 5/100,000" is pretty useless as it will flicker between 5 and 0 whenever a crank or lock is turned.
 
The 5 micron scales are pretty much the defacto standard with most DRO's these days, it is not that you need to read down to 0.0002", but that the reading error is decreased and there is better linearity across the scale. It also depends on the machine, the amount of wear and what your need is. The other consideration is that the newer DRO head units offer many functions, like the use of electronic edge finders, tool libraries as well as function keys. They are also less bulky then the older DRO units. Function wise, if just looking at the numbers, then little difference, in particular if there is a bit of wear on the mill. Whether you have a 5 or 10 micron scale makes little difference, and a 1 micron scale on a manual mill drives most people crazy with the 5th digit. The quality, linearity and repeatability of the scale can be an issue. The Sargon is pretty ancient technology, but there are people who are looking for replacements units so there may be more value to selling it if you want to go through the hassle. There is also the issue of adapting the older scales, and if it will work.
 
Shotgun said:
For a manual mill? Good luck on being able to dial in those numbers and then having everything else dialed in close enough for the higher resolution to make a difference. You can do it. Plenty of people do. I try my best to hit it most of the time, but locking the table axis will make mine move off the number. Trying to stick .0005 is a PIA and .0002 is down to the surface finish. A worn end-mill will throw that number off. I think the scales went that low just because they could, not because they were needed by anyone making parts.

Save the money for accessories, which you will never have enough of and you'll actually use.
Click to expand...
Truth!


We have .0002 scales at work, this is Tool&Die mind you and guys put electrical tape over the tenths numbers.

Me, Im not that smart and fight the machine to get just the right position so when I make a mistake Im double frustrated.

Most of what the average user needs could work fine at +- .005, but working that loose gives people the heebie jeebies for some reason.

Im guilty of that.

If you go by prints:

.000= +- .005

.0000=+-.0005

Anything finer than that is for NC or EDM work.
 
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