DROs etc

I have a DRO on my vertical mill but it’s not really there for accuracy. It allows me to:-

1 Switch between metric and imperial units
2 Set zero reference at the push of a button

3 Drill holes on a pitch circle for flange mounts and for chain drilling

4 Drill holes space along a line at an given angle

5 Add and subtract

6 And finally eliminate the requirement to approach all positions from the same direction to take up lead screw backlash.

I would not be without it.

regards Martin

PS It’s value is huge as a mistake eliminator.

Edited By Martin Kyte on 21/09/2023 13:19:12

Martin, points 1,2 and 6 seem to me to be game changers.

Anyone recommend a DRO set up for a Naerok mill? (The more useful round column mill as the column is effectively keyed)

Must be fairly cheap. Also anyone know where I can get the long travel nut from?

Points 1 and 2 are the primary ones for me too.

I've not tried PCDs and lines at angles but only because I've not so far needed to, or have tackled those tasks in other ways.

Point 6 though is an interesting one. I may be over-cautious but do still account for the backlash, especially on the long travel when used over a long distance, as there is a curious "miss" point of nearly a full turn in the screw's action on my mill. It may be by an accumulating backlash of some sort. The machine has no power feeds to be affected by it, and it does not seem to affect the feed anyway.

To set the edge from the fence I use as my main alignment tool I usually clip a small flat to the work-side of the fence, projecting above it, and bring the wobbler to the rear of that, so I wind the screw in the same distance to reach the machining points. I do so whether using the dials or DRO, and while it not be strictly (or theoretically) necessary for the latter, regard it as good practice to keep the habit and it takes no significant extra time... as if that matters anyway.

One point about my DRO is that switching between mm and inch seems to need turning the device off and on again, but I may have missed something simple in the instructions.

The biggest advantage to me of the DRO is actual measurement so I don't need keep tabs on handwheel turns, and assurance that Part A will screw to Part B without having enlarge bolt-holes or to file them oval!

BUT.... it still needs me to make sure I read the numbers correctly! It's not a mistake-corrector or metal putter-onner!

It also retains the last measurements after switching off, but I do return everything as a precaution to (0, 0, 0) if I stop for the night in mid-machining.

1000's of models have been produced in the past without DRO's or milling machines but is you can afford them and want to make life a little easier why not

H

Nigel Graham 2, I’m not getting your point about 6, all DRO’s these days measure table movement, the table screw accuracy or otherwise is irrelevant.

Tony

Tony, there were some mechanical digital readouts that were fitted to the handwheels before modern electronic scales became cheap enough to be considered value for money in a home workshop. These mechanical readouts would still be at the mercy of backlash and error accumulation.

It seems that, for most of us now, when we see DRO we automatically assume it means an electronic one with scales mounted on the ways. I do think the original post by Martin K implied this type.

Martin C

Martin C, thanks I'm aware of backlash affected DRO's and used one on a jig borer back in the day but doubt these are around now, from memory these were simple table movement indicators without the multitude of useful additional functions on present day DRO's?

Tony

Before the days of readouts, digital, mechanical or optical, backlash in leadscrews had to be taken in to account and was always taken up in one direction, hence Martins point 6

Hi everyone. I am humbled by all the responses and grateful to all who have responded. I mistakenly quoted my lathe as SC3 but it is the SC4. Not that it matters but just for clarity. I am now in my late sixties and have been a tradesman working in home improvement all my life before retirement. I have little engineering experience when it comes to lathe work and zero milling. So some of the advice on the thread goes over my head. Although I did attended an Axminster beginners lathe course which fired my enthusiasm to take up machining as a hobby. Also thus, my choice of lathe as they used them in their skill Center. Having said.all that in the hope that I have a degree of practical skills which should help. So I want to choose a beginners project and challenge myself. I will be buying a Sieg SX7 milling machine sometime in the near future. My skills with layout and set out as well as using accurate measuring devices is minimal so I think a 3 axis DRO on the mill will help and probably a linear bar digital scale on the longitudinal bed of the lathe. I continue to study videos on YouTube to increase my knowledge and understanding but it is fast approaching time to actually commit to a project. All in all I am looking forward to going forward although there are no clubs anywhere near me and I will rely on remote advice. So thanks again and expect more dumb questions ongoing.

regards

Steve

Tony -

I am simply being extra careful, whether the leadscrew slack matters or not with a DRO. Also as I don't always use the digital display, I keep the habit of one-way working.

Still no DRO...
Steve I am in similar situation than you, this is totally different than I did before, however I grew up fixing my own stuff as far as I can. I watch youtube videos for 3 years to get the feel of if it, how they talk about the operations, tools used etc. before I bought a lathe 1st, then a mill. I now like the mill more and more as I use it, and wonder why I did not buy this with my 1st house/garage already. I still dont have a DRO, the one I saw 1st hand and like is still too expensive at stage as I buy the tools I feel I need 1st and that will continue for some time.....I usually learn something from each video, although some creators are hard to continue watching. Forums you get more to the point info asking about something specific. With an open mind you can learn a lot by yourself from others, pick and chose and experience. I learned that patience and a plan is a good thing.

I'd agree with all of Jason's thoughts and about the marking out when you have a dro. I'll do so on more complex parts and it helps when changing the part orientation in the vise for which side of the part or line you should really be on for the approximate location of other features and to prevent stupid mistakes.

I know I'll get some argument, but I think it was in one of T.D. Walshaws books where he details just how inaccurate marking out and then center punching for hole locations can be. Apparently he was present or somehow got the results from a technical school where they ran a test with a number of students who already had a couple of years experience. My guess is it was probably done sometime in the 1960's to maybe 1980's since dro's of any kind weren't even mentioned. For the first test they did conventional marking out and center punching for a drill press, the second, marking out, center punching and then conventional hole location using the machine dials, the third was only with the dials. In every case that center punching was surprisingly much less accurate with a few locations up to .020" away from there correct location. And that coordinate location was the best. For full scale fabrication work, then that center punching is probably fine or at least good enough in most cases. For a lot of what were doing, you either do so and as Jason mentioned use that to transfer drill a mating part, or imo much better is that coordinate location by either the dials or dro. For larger or parts that can't for whatever reason be put on a mill, then of course I'd still center punch just to get the drill started at least close to where I want it.

On parts that may have a lot of features I may "mark out" with a sharpie but don't count that as proper marking out, as Pete says it is just to help ensure the orientation is correct and helps avoid silly errors like positioning a 6 hole PCD north south rater than east west.

As for proper marking unless it is something like sheet metal than I'll use a height gauge rather than a rule if possible and any punching gets done with an optical ctr punch and if that is not right I'll pull it over with a hand punch. This is mostly reserved for ctr locations that will be going into teh 4-jaw lihe eccentrics or rod holes in valve chests which can then be set to run true with a dti. I see no point in doing it this way if the part is going on the mill when I can pick up the edges with an edge finder and then use the DRO to position the hole. Soemtimes I will even position a ctr drill hole using te hmill and then transfer the work to teh lathe so eliminating even more marking out.

Thats a generalisation of how I work but depending on the part may use other methods as suits.

I'm surprised that nobody has mentioned the 'Half' function that almost all DROs have. That, together with an edge-finder is a game changer.

I do use Half a lot as I tend to work from the ctr of most parts so find one side and zero, find the other and half the reading. Also averages out the two edge finder positions rather than using one edge position only

Jason:

Me too, hence my surprise.

I also use this technique on the mill - which is one that you cannot realistically use on a machine without DRO for position readout as backlash otherwise makes it unreliable using the handwheel dials. Unless you have very low backlash via ballscrews or similar - and that usually comes with CNC which is another can of worms!

I cheerfully used my Super 7 for years without a DRO but that all changed when I bought another lathe with DRO already installed. Apart from the tailstock, I doubt I've ever used the handwheel dials since - and especially for imperial machining on an otherwise metric lathe.

I have 'collected' devices and methods over the years, including 3 axis DRO, but still use one method out of habit, I suppose. Assume a piece of bar deliberately arranged to protrude from one side of the machine vise. Measure diameter with electronic digital calipers and add to 1/4" diameter of centre drill body, then halve answer. Move work towards centre drill body til a 10 thou feeler blade is nipped between the two. I now know how much to keep turning the hand wheel in the same direction to centre the drill over the work centre, having allowed/avoided any backlash. If there are 2 or more items to be drilled at the same distance from the end of the work, I will then set up a simple end stop, to enable both X and Y positional repeatability. This is sufficient for most jobs. The DRO is not so instantly available as each axis is dependent upon a battery being installed. I often remove batteries from various items just in case of failure, having had destructive leaks in the past. If I was clock making, I think that I would strive for greater accuracy, perhaps using the DRO and another method as a check. Only have a DRO on one mill at the moment and may well get another for the other mill. Don't feel the need for a DRO on the lathe, just use time honoured methods which serve me well.

There were a whole lot of parts made to accuracy levels most of us couldn't even replicate today, and long before dro's or ball screws were invented Nealeb. As good as I think my dro is, if I really had to, I could machine to about the same levels of accuracy using a more rudimentary method of what I mentioned on the first page of this thread. That would be extremely slow way to work, although semi permanently mounting the indicators square to the table travels and having clips with true alignments to those travels for various lengths of measuring rods would help speed that up by quite a bit. But it's still more than possible. And without a dro, an indicator set up against the edge or end of the table can be used to show where your backlash ends and the table begins to move. Note your machines dial number at that point or zero it, then move to your known coordinate using either that dial or the indicator for shorter distances within the indicators travel. Again it's much slower, but backlash on manual machine tools is inevitable in various amounts and has always required compensation for in one way or another.

In 1805 Maudslay invented and produced a 1/10,000th capable bench micrometer built using a lathe that no doubt had a large amount of back lash. And machine produced threads had only been invented 42 years before that. By 1868 B & S were producing micrometers very similar to what we still have today. I have a book about Tool & Gauge Work from 1907 and it has drawings for a shop built dti. With it, and a set of shop built hardened and ground tool maker buttons, plus a good set of micrometers. They were hand positioning parts on a sleeve bearing lathes face plate and producing bored and ground master gauges to amazingly accurate levels. While I could probably just measure what they were doing if I was being really careful, neither I or my current lathe could do the same. Even with the best dro made today I still couldn't because my lathe and it's spindle bearings aren't accurate enough.

Depending on how high the accuracy any mill has been built to, or if your using metric / imperial on a machine using the opposite measurement system, those dials and feed screws may or may not have the capability something out of the average requires. High accuracy ACME feed screws and nuts are easily found through specialist manufacturer's. Getting something to fit on the smaller machines may have real issues. And as the guaranteed accuracy levels go up, they get much more expensive than just fitting one of the cheaper dro systems that are available today.

All this is well outside Steve Huckins original thread topic, but there seems to be some amount of for and against opinions about dro's. Yes of course you can produce good work without them. That's been well proven for over a 100 years even in the pages of Model Engineer. Other than the extra cost, they have few disadvantages and more than enough advantages to far outweigh those. And for those with less experience, they definitely help prevent a lot of errors on there parts if there being used properly. How many have added a dro and then posted that they now think it was a mistake?

I have a dro on my small lathe but as my mill is a Sieg SX1L and very small I am trying to see how to replace it with something a little larger before I go down the dro route - but this is unlikely without major building work to extend my garage workshop!

But the point I would like to make is that milling machines were not common I. The home workshop even in the 1960's and if you go back a little further many articles described how to manage without vertical slides, micrometers or even dials on cross or top slides (or even topslides themselves!)

The mindset to have is not what do you need to make something but rather "I know I can make it but would an accessory or two make it easier, or make the accuracy I would like easier to achieve"

So no you don't need a dro but it will give you more information about how you manipulate the machine tool that could be useful and probably, but not certainly, tell you the dimensions of what you are making visually.