DROs etc

I have been studying YouTube regarding a first project such as Stuart model engines. Although I do not yet have a mill, it is on my wish list and probably a Sieg SX7. I already have an SC3 lathe. I see that for serious accuracy most model engineers have DROs on both (2 axis) lathe and (3 axis) mill. I wonder if it is possible to get really good results without using them ???

I have it in mind to purchase one for the lathe soon and does anyone have some advice regarding a good option and where to buy. Maybe how to fit them as well. Although there are plenty of videos on YouTube, some more personal experience from all of you would be better.

Probably a huge subject !!

Cheers

Steve

Personally I would fit a DRO to the mill over the lathe any day of the week so save your money until then.

Yes it is still possible to do good work with just handwheels but that obviously can depend on the user, my first engine was a Stuart 10V which I still have and that will run simply by blowing into it and was done on avery small Unimat 3 and I'm not an engineer by trade. I do have a DRO on the mill now and would not be without it, have not got round to fitting one to the lateh and quite probably wont.

Can you get good results without a DRO?

Yes. All the engines you are likely to model were made without a DRO.

Also, a mill is nice... but a lot of Stuart engines were designed with being made on a lathe in mind.

I fitted a digital read-bar to the long travel of my ML7R and would not be without it. They cost around £30, depending on length, from Arc Euro Trade, Chronos Tools and others and in my humble opinion worth every penny.

Dick

I have a professional 2-axis DRO on my vertical mill and nothing on the lathe.That suits me fine. The DRO on the mill is the single most useful accessory I have bought, but I simply don't see the need for one on the lathe. I am pretty sure the DRO scales on the lathe would interfere with operation, and clash with other accessories, whereas on the mill they are clear of any interference with operation.

Andrew

+1 for DRO on the mill, but don't skimp and go for only 2-axis, the Z scale is so useful. Contrary to other opinions I fitted DRO to my lathe too, and wouldn't be without it now. But overall, the mill benefits the most.

You don't need a DRO in order to make anything. If you have some measuring instruments and a way to mark things out then most things can be made. Remember this is a hobby and time is not a factor so making one part fit another with somewhere near limits and fits works. Drawing dimensions for the hobbyist are there as a guide, if a piston is drawn to be 5/8 inch it doesn't matter is you made to 16mm so long as the bore it goes into is the same and all other fitting parts are as well. I went without a DRO on my initial lathe and mill, a SC3 and SX2P for five years before changing both for bigger machines which now have DRO, but I still managed to make a working 3 1/2inch steam loco running chassis. A DRO setup, particularly on a mill, allows you to do things quicker but no more accurately if you take care and the additional cost may not be worth it if the machine doesn't cut accurately.

As an apprentice on a Harrison 10 lathe I had to make 400 parts for Rolls Royce aero engines inspection department accurate to .00025" with a micrometer, so in answer to your question YES accurate work can be done with out a DRO ! Noel.

I am in full agreement with Andrew, readouts on lathes especially smaller lathes get in the way, an example being the Myford 7 series, you cannot use the rear bed stop or taper turning attachment with readouts attached, how do I know, I fitted two axis readouts to my super seven and regretted it ever since, I still have not sussed out how to store offsets for multiple tools, despite having used dozens of lathes and mills equipped with readouts in my working life. I have got to remove them soon so I can use the taper turning attachment, I doubt very much if they will be put back on. On the other hand I have a set of Mitutoyo 3 axis readouts on the mill and would not be without them.

I certainly don't consider myself any sort of expert on this matter, nor do I have DROs on my small lathe (although I have, quite a few years back used a larger machine that had them fitted). But just a personal view of the topic which are certainly not intended to disagree with the "pro camp" - just offered as a different perspective.

It's now possible to use AI to write a letter. Before that using a computer with voice recognition. Before that a word processor, an electric typewriter, a manual typewriter. And, before all of those things - a pen. In other words, none of that technology is essential in order to write a letter. It just makes the job (arguably, some might say) easier or, more to the point, quicker.

I think the point is it's easy to be drawn into the mindset that add-ons, gadgets, gizmos (to generalise) are essential and indespenible. I suppose in some cases "technology" (again generalising) can help in plugging a gap in skill or ability. But generally are not essential.

The first micrometer was invented in 1772. I'm not sure when DROs were first introduced but let's assume, for the sake of illustration, the 1980's. Just look at what was produced as a result of skill and ingenuity in that intervening period.

Another reason for my views here is my underlying beleif that engineering is inherently about ingenuity or "finding a way". This was excellently summed up by the first really knowledgeable engineer I ever met (actually one of my lecturers many years ago) who advised: an engineer is a person who can do for a bob what any fool can do for a quid. That principle in pretty ingrained in the way I approach challenges.

Andy

Of course you can produce first-rate results without a DRO.

The electronics simply makes the task easier and perhaps less prone to error (anyone can miscount hand-wheel turns or make a reading error; but some marking-out first will go a long way to minimising that risk.)

I have fitted a Machine-DRO set to my mill, all 3 axes, and do use it, though not every time. Depending to some extent on the work I still use the dials occasionally to maintain my ability with them, or because it's just as quick.

Fitting it on a machine not built to take one, a Myford VMC, was a challenge involving much rather complicated metalwork and the loss of the table-stops. Just because I've a box of numbers does not mean I need sacrifice existing aids unless enforced mechanically as here. I prefer augmenting or complementing such aids, not mere replacing.

I have not yet used its more advanced features such as pitch-circles and radius-generating, but the instruction-manual is very clear, and I am very pleased with having put my works retirement collection towards it!

.

I have not fitted a DRO to either of my lathes, where I think them marginally less valuable and right in the way of all the swarf and coolant; and anyway the Myford ML7 is crowded already. (Myford sells a new version of the top-slide, I think, with a rectangular outline to facilitate fitting a DRO.)

.

As for "serious accuracy", although a DRO will read to the tiddliest bit of thous or mm, the accuracy (or is it precisyon?) and quality of the work it is still very much up to the operator! The display is an aid to your accuracy, not an accuracy-maker itself.

Excellent point: the DRO (or other measurement system) provide precision but the operator achieves accuracy which is a pretty binary outcome: it's either within the limits of required tolerances or it isn't.

You don't need a DRO to make accurate parts. However I feel the DRO's on my machines help me ensure I'm more likely to get parts right first time than when using the usual methods. Whether they are worth it depends on how valuable you feel your time is. Even if it is a hobby it should be enjoyable and there is probably nothing more frustrating than have to make a part again because of a simple measurement error. Even more so if that part is one from a set of castings.

I find making an in situ diameter measurement on a lathe the most difficult and frustrating as the carriage or tailstock often prevent a clear view of digital calipers. With a DRO I measure the first cut and then calibrate the DRO for that tool. This ideal for multiple parts as they all come out the same diameter but you have to ensure you get the first one the right diameter.

Using the DRO on a mill to spot mark multiple hole locations for latter drilling is particularly valuable and reduces silly errors.

CS

Most Model Engineering doesn't take extremely high accuracy since much of what we do is simply fitting one part to another with the correct clearances for smooth operation. What is important and not stressed enough on these forums is paying a lot of attention that your machine alignments are correct. Square and true parts to each other is extremely important for any functional model engine and its operation since there's so little HP developed. Where a mill dro really helps is the easy and repeatable location accuracy for machined features. Any decent dro today can allow items such as bolt hole locations to very close limits. All feed screws including the best in the world will have measurable amounts of what are called lead and lag pitch errors. And the less you pay for any machine tool, the higher the chances those errors will be larger. So an accurate dro system can produce better or at least more repeatable accuracy than the machine itself was built to produce. They also pretty much eliminate any feed screw and nut backlash that takes a fair amount of mental arithmetic to keep track of or your parts will be scrap.

But not all dro's are created equal. There's 3 terms that need to be properly understood and then researched for whatever system your planning to buy. Accuracy, Repeatability and Resolution. Any of the better dro's and metrogy equipment will all have those specifications listed. Accuracy is mostly a combination of all the effort that went into the system and it's components to manufacture it. Repeatability is also somewhat related to producing that accuracy, and while both are related, there still not the exact same thing. So that repeatability number means how well it's components can be expected to repeat the same measurement distance each time. Resolution gets confused by most, it simply means how many digits there are to the right of the decimal mark. You could have a display showing .0001" or .001 mm as the smallest digit, yet that does not mean what you bought is in fact capable of that level of accuracy or repeatability. There's also a world wide standard in use, and that for good metrology equipment, it should be accurate and repeatable to + or - one digit of it's smallest division on it's markings or display.

Yes those much cheaper bar type scales and displays may show measurements to the nearest .001" or .025 mm. But the guaranteed specifications on even Starrett or Mitutoyo bar scales would still allow maximum inaccuracy's of that + - one count. On average those two brands will generally have about half the maximum allowable on any of there metrolgy equipment I've checked. But any of those bar type scales are poorly protected from cutting fluids and swarf when used on machine tools because that's not the environment they were really designed for. So there long term life spans are usually fairly poor because of that. The better and more usual dro's today with the separate display units will or should have a lot of built in useful programs to make them highly useful. On a mill, then quickly finding your part center, pitch circle for bolt holes, point to point locations of holes etc are imo highly desirable. Even having your Y axis zero preset on the rear fixed jaw of the vise speeds up the work by a lot since it's always in that known and repeatable position. And to get the best out of a dro on any mill, then good edge finding technique and a tool that will provide a high level of both accuracy and repeatability for a part edge or surface is also required.

It's also impossible to give all the examples of how any dro can be mounted. All of that depends on what exact machine and dro system you have. One almost universal requirement would be having a dial indicator and magnetic base since the manufacturer's will usually recommend those scales be set up within at least .001" or .025 mm or better in two dimensions along there full length. But I doubt there's many dro's where the end user didn't have to machine at least some parts to adapt there dro to the specifics of the machine there mounted to. It's not usually all that hard to do, it just takes a bit of thought.

Permit me, please, to philosophise from a sedentary position:

DROs can be an enormous time-saver, and an aid to accurate working … but , as might be inferred from Pete’s excellent note, they can also be misleading.

Until we get down to the atomic level … ‘stuff’ is analogue in its nature, not digital

Therefore anything you care to measure digitally could be more accurately measured using analogue instruments.

The cost and complexity of so-doing might, of course, be excessive !!

MichaelG.

Steve, to be classed as a 'model engineer', the following BASIC rules MUST be obeyed.

1. Nothing other than a Miffod lathe is acceptable.

2. QCTPs are obligatory.

3. Carbide cutting tools are essential.

So yes, your disposable (or non) income needs to be frittered on non essential goodies to be accepted into Home Workshop elite.

All that glisters is not Gold and many of the Hew Tub videos need to be observed with a pot of SAXA (or other brands) close to hand.

Regards Ian.

Yes your 100% correct about the differences between analog and digital Michael. Digital is either the number it's on or higher and lower, there's no interpreting between the divisions like you could with something that's analog.

Prior to the invention of our now common dro's, those screw pitch accuracy problems were a large issue for high accuracy machine tools. Moore Tools in the U.S. spent very large amounts of time, effort and money trying to manufacture feed screws and nuts with much lower deviations for there jig borers and grinders. Even they failed. They got close, but still not quite good enough. And any wear over some time obviously affects there ultimate pitch accuracy as well. Instead and what they did is sort of come up with an analog method for high accuracy machine coordinate moves on each axis. 1.000" travel .0001" reading dial indicators and what were known as distance rods in almost exact 1" increments clipped in place depending on how far those moves were. Those were a bit like what we have today for micrometer setting rods. But those expensive distance rod sets were built with much higher accuracy levels than even those micrometer rods. Today those jig borer and grinder sets can still be found at normally fairly reasonable prices because few other than hobbyist's would use them. They would still work well for straight line X,Y,Z moves on a mill. But anything more complex such as bolt circles would require the same good understanding of trigonometry to calculate the X,Y positioning, and a lot more time to properly use them. At high enough levels of accuracy, having more exact environmental temperature control becomes important. All a bit outside what most model engineering would ever require, but still at least worth knowing how it was done I think. I've used that method and my micrometer rods to make fairly high accuracy carriage moves on my lathes a few times.

But it's also worth understanding than no dro can compensate for the inevitable machine or part deflections. It's still cut a bit oversize, measure and then make your final adjustments process. They get you close and are faster to use as you mentioned, but no matter how perfect a dro might be, our machines and methods are still a bit inexact.

Edited By Pete on 21/09/2023 07:46:25

The comment that as model engineers we tend to make one part to fit another is interesting.

On the lathe I will often use the part turned first to gauge the size and fit of the second diameter so in that case making one to fit the other applies.

However on the mill it is very much the opposite and since fitting the DRO I tend to make each part with that and they fit. The old books and mag articles would generally tell you to mark out and drill one part, then clamp it to the other to spot or drill through into the second and if it were a tapped hole you would then have to open up the initial holes to clearance size. So a lot more long winded and there could be errors in the marking out and picking up those marks.

Now with the DRO I just drill say the ends of a cylinder using the DRO's PCD option with tapping size and go round again to guide the tap so it is directly above the hole. Then the covers get done straight away with clearance holes so no need to do them tapping size followed by opening up. I then know that my covers willfit in any orientation as the holes have all been placed equaly and I don't tend to allow much in the way of clearance eg a M3 fixing goes into a 3mm drilled hole.

I seldom do any marking out now, usually locate the ctr or edge of the part and then use the DRO to locate any features, lets face it even if your DRO only reads to 0.01mm that is going to be more accurate than most people can use a rule, scribed line, correctly located punch mark and picking up that punched location not to mention a whole lot quicker. Or if using the handwheels to place the features there is no need for compensating for backlash

A DRO on a lathe lets you

• Switch between metric and imperial should you need to (except when threading).
• Take measured length cuts with the carriage when there is no graduated dial on the lead screw and the top slide travel is too short or set over at an angle.

It also gives notice when backlash has struck as the display will change.

Is it worth £200+ to you ?

With a mill, above it's a no brainer, they need one.

For many years I used my trusty Myford without a DRO, now that I have a DRO on it, which that I had done it earlier. I find the dro to be alot more useful and time saving than I ever envisaged. I started with fitting a dro onto the Myford Quill for drilling depths etc. Been so useful to have.

The same with the Mill / Drill . Since putting the dro on to it, it has been really great. My next project is to add the Quill dro, and have it linked to the table/ column Z axis. We have a mill at work with the table and quill linked, and I really like it.

I don't think it matters which way you go for the dro, but do take into consideration coolants if you use them etc. A friend fitted the type that are based on a digital scale like a digital caliper with remote screen. It works just great for him.

Then look at features, I think they all have similar things like pitching holes, but I really like the multi point radius options, that can be used in lathes or mills etc. My dro's have a rpm feature, very usefull if you have added a VDF for variable speed ranges.

Is it something that the more you use a dro you will discover new and better ways of doing things and often more easily as well.

Neil

Edited By Neil Lickfold on 21/09/2023 11:03:29