digital readouts Amazon sells

[JimGlass]

I have an old Sony DRO Magnescale that recently died. I see Amazon sells DRO's real cheap, $150-$300. Are they any good?

[Bill Shields]

Try DRO Pros..they are a good, reliable consistent group to deal with. Honest fair prices, consistent service.

I di not work for them but am a satisfied customer for many years.

While it is true that they have no control over companies that go out of business, but they appear to choose their suppliers carefully...which may not happen with Amazon suppliers who can be here today, gone tomorrow.

[NP317]

I agree with Bill.
The DRO Pros devices I installed on my milling machine have been perfect for my needs.
RussN

[Steggy]

I have an old Sony DRO Magnescale that recently died. I see Amazon sells DRO's real cheap, $150-$300. Are they any good?

The main weakness of the “economy” DRO models is in the scale (aka encoder) that detects feed movements. Cheap DRO kits use a glass scale and the really cheap kits use a capacitive scale. The good DRO kits use a magnetic scale, which has a number of distinct and important advantages over the other types.

Capacitive scales are the cheapest and least desirable. Absolute resolution is good but linearity tends to degrade over longer distances, such as in tracking the movement of a lathe's carriage. A capacitive scale can be disturbed by electrical noise and linearity can change with temperature and/or varying amounts of contamination. Fun fact: many electronic digital calipers have a capacitive encoder, which means you should take a reading from such a caliper with a grain of salt. Avoid a DRO kit with a capacitive scale.

A glass scale has high absolute resolution and very good linearity, and it largely immune to electrical noise and reasonable temperature fluctuations. However, there is a certain amount fragility, plus a glass scale can be contaminated to the point where it will be erratic or completely inoperative. Glass scales come in fixed physical lengths, which may complicate installation.

A magnetic scale has essentially the same performance capabilities as a glass scale, but suffers from none of the issues. The absolute resolution of a magnetic scale isn't quite as good as a glass one, but is still well beyond what is needed with a machine tool. A handy feature of a magnetic scale is it can be cut to size to fit a particular installation.

As always, you only get what you pay for.

[atunguyd]

Glass scales can be cut to size too. Plenty of videos on YouTube of people doing so.

True they can get contaminated but they normally come with covers and if you mount them in the correct orientation it is highly unlikely.

My instinct tells me that magnetic scales can be interfered with too. Surely a magnet stuck on or near them would cause errors? And there are plenty of sources of magnets in the workshop. Just speculation on my side, I have no proof of this.



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[Steggy]

Glass scales can be cut to size too. Plenty of videos on YouTube of people doing so.

Yep, I've seen those videos. What they don't show you is how many scales have gotten trashed in the process. Cutting a glass scale is quite risky, in that the glass lining in the scale's interior can craze or shatter, rending the scale useless—and without a warranty.

True they can get contaminated but they normally come with covers and if you mount them in the correct orientation it is highly unlikely.

It won't matter how a glass scale is oriented if coolant is being sprayed, as mist will get into the scale where the external part of the read head protrudes from the scale channel. That sliding rubber seal is not guaranteed to be liquid-tight.

My instinct tells me that magnetic scales can be interfered with too. Surely a magnet stuck on or near them would cause errors? And there are plenty of sources of magnets in the workshop. Just speculation on my side, I have no proof of this.

Actually not. A stationary magnet has no effect on a magnetic scale. Multiple poles on the read head are used to produce a polyphase flux pattern that a single magnet could not possibly duplicate. Also, the read head uses the principle of magnetic reluctance to prevent interference. Even the oscillating magnetic field generated by a nearby motor has no effect.

As a magnetic scale isn't affected by coolant and other contamination and thus needs no seals, it can be made thinner and narrower than an equivalent glass scale. which feature often simplifies installation. Also, the read head is removable, which further simplifies installation.

I should mention that the cost of magnetic scales has come down to where they are only slightly more expensive than glass. If I were going to fit a DRO to one of my machines, it would be with a magnetic scale.

[NP317]

After installing a DRO on my lathe which uses glass scales, I chose to use magnetic scales on my milling machine installation.
So far both systems continue to work flawlessly, but I definitely prefer the mag. scales for the reasons described by BDD.
RussN

[Bill Shields]

Me three.

Esp on my small lathe where the X axis scale causes interference with the short nose tailstock (typical SB 10" lathe problem).

A glass scale is a non starter.

[Steggy]

I'm old school when it comes to using machine tools and have relied on the collars ever since I learned how to machine things (that was 64 years ago—yikes!). I've made everything under the sun—including some aircraft parts, in some cases to a few tenths, using only the collars. That's why I never hopped on board the DRO wagon. I didn't see any advantage to it.

However, vision loss is getting in the way, and those little numbers and marks on the collars seem to be shrinking at a rapid rate. I may have to fit my lathe with a DRO just so I can see what the heck it is I am doing.

[Harold_V]

I turned 83 last week. My vision is not what it used to be. Like you, I, too, am old school. I still don't use a DRO, nor am I tempted to. Like you, I learned to use the dials and cherish the skills I acquired in doing so. I really don't want to sacrifice them or allow them to atrophy from disuse. Not saying there's anything wrong with their use--it's just my way of expressing my capabilities. I worked hard to gain those skills and would not enjoy losing them.

H

[atunguyd]

Totally get your guys reason for not using a DRO and I agree you can be just as accurate using dials. Hell plenty of aircraft were built on mass during WW2 using dials on machine tools.

That said however using a DRO is not about accuracy for me but rather time. If I need to move over to another point 23.4mm away I crank the wheel to I get there. Worth the dials I need to count the number of revolutions then remember that each revolution is 3mm but since I am traversing left I need to subtract from three to get to my point on the final rotation.

With a DRO I just advance to said point. Then I can add that point to my point list and move to the next one. Want to return to point A? I just select it on the DRO and all measurements magically are relative to point A so I just crank the wheels till I see 0 on both axis.

With two kids I don't often get time in the workshop. I'd like to use that time building and not counting revolutions.

Horses for courses I guess.

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[Mr Ron]

I have the DROPRO on my milling machine and am very pleased with it. Best money spent. Just dial in the number you want, No keeping track of revolutions on a dial. i do appreciate the skill developed in using dials, but it is not a skill I am able to develop. Since I got a DRO, my precision machining has improved to the point where I can get parts to fit together as they should. Thinking about getting one for my Sheldon lathe.