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Lathe DRO

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Jim Smith 812/04/2021 22:57:00
7 forum posts
1 photos

Hi, I'm setting up a 'new to me' Warco WM280V-F that came with a 2 axis DRO. I'm just starting out learning lathe work and everybody tells me a DRO on an imperial lathe like mine makes life much easier.

However I'm puzzled: X axis Longitudinal traverse (large hand wheel) is measured by the DRO but is quite coarse. The Compound rest traverse on the same X axis is much finer and would expect it to get most use for boring, turning and facing? In my ignorance I can't understand why the DRO scale would be on the Longitudinal traverse, unless it is more often used for thread cutting which I don't expect to do.

Could somebody explain how this DRO setup comes about, or do lathe users add a second axis readout for the compound traverse?

Many thanks.

duncan webster12/04/2021 23:12:03
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3178 forum posts
55 photos

I use my topslide for screwcutting and turning short tapers, ie fairly infrequently. I have actually considered taking it off as unless it is set round a bit (which mine usually is) it is always in the way of the tailstock. More useful would be a saddle stop to limit the travel of the saddle towards the headstock, must get round to making one, but as I've managed without for 50 years it's not high on the list.

Grindstone Cowboy12/04/2021 23:12:11
584 forum posts
57 photos

I don't have a DRO, but I wouldn't think a scale on the compound would be much use as it would only give meaningful readings if exactly parallel (or perpendicular) to the lathe bed.

Rob

Pete Rimmer12/04/2021 23:19:04
940 forum posts
57 photos

It's unusual - almost impractical - to have a DRO scale on a compound since it tends to not be used much and even then only over short distances of less than 1 turn for the most part. There is also the complication of space constraints and the fact that the compound rotates meaning that you'll have to have loops of leads that are prone to snagging.

Most of your turning will be done in the X and Z axis, X being across the ways and Z being along them. There are a myriad of functions that a good DRO will provide with scales on X and Z.

Jim Smith 813/04/2021 00:32:31
7 forum posts
1 photos

Thanks, I understand now about the compound being absolutely parallel as i read somebody did add a scale but the DRO readout did some clever maths with the angle. And yes even 2 leads moving across the back of the lathe need watching. I have seen a video of a scale added to a compound which had an integrated lcd readout but if it's anything like a cheap vernier I tried with a rubber wheel tarvelling along and missing counts, I'll give that a miss.

Sorry if I confused on X,Y Z. In maths, X is horizontal, Y is vertical and Z up and down but then that's on a piece of paper.. Something else to learn! So what I initially mean't which you all understood, is my DRO scale is on Z but when the tool holder is set parallel, it has fine control in the Z axis along the ways, which isn't measured.

On another point, I have a quick change tool post that takes up to 16mm sq. tools and I just got some cheaper 12mm HST tools to practice with, since I don't want to ruin tipped tools. The height setting screw on the post seems to foul on the Warco flip down guard if I take a tool close to the chuck but is still a safe distance away. I'll post a photo later to show this.

I've also read the beginners first mistake with no saddle stops! Manually I can be very careful, but its what can go wrong if power feed is used that would worry me. I shall leave that alone at the moment.

Hopper13/04/2021 04:55:11
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5427 forum posts
134 photos

DRO on the carriage travel is all you need. It's what you use for most turning and boring. Compound is usually only used for turning tapers and screwcutting. Feed on the carriage by the handwheel is fine enough for most work. And a handwheel on th eend of the leadscrew gives very fine adjustment indeed, ala Myford.

Take the chuck guard off. They are nanny-state overkill and not at all necessary. Or cut a lump out of it to clear your tool holder. You can also sit your smaller tooling on packing strips in the toolholder if that puts things in the right position. So if using 12mm tooling, a piece of 4mm flat bar underneath it will make it same height as 16mm tooling.

Usual terminology for lathes is the carriage travel left to right is X. Cross slide travel (ie depth of cut) is Y. There is no Z. Z is the vertical movement of the spindle or table on a milling machine, which a lathe does not have. So you had it right first time!

Edited By Hopper on 13/04/2021 04:59:39

not done it yet13/04/2021 07:21:46
5853 forum posts
20 photos

Are you trying to suggest the long travel has no power feed on your lathe?

My 60 year old lathe has power feed on both long and cross travel - as little as 0.01mm per spindle revolution. The carriage and cross slides are the only guaranteed way to cut parallel and perpendicular to the lathe axis unless the compound is set very precisely every time you change from facing to long travel cutting.

Further, the distance one can cut with a compound is very much restricted. My lathe has 610mm between centres but only about 75mm travel on the compound slide. That alone would make turning hard work.

People mostly use the carriage handwheel to fast-traverse the cutter, I would think. I do.

JasonB13/04/2021 07:34:23
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20442 forum posts
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The 280 does have a very coarse apron handwheel feed that makes it hard to put on a few thou cut when say facing a job or cutting a spigot to a set length. My topslide is set parallel all the time except when cutting angles and I tend to use that to put on a cut or space out things like cylinder cooling fins along the length of the cylinder as the aprons 0.020" divisions on the handwheel together with it's action make it very hard to hit a set position.

There are some machines where the owner has hollowed out the underside of the topslide and hidden the readout inside, even new factory Myfords can have this. You then ideally want a DRO console that "sums" the carrage and topslid ereadings or you can get a unit that the two plug into and the output goes to a single socket in the consol

Edited By JasonB on 13/04/2021 07:34:50

John Haine13/04/2021 08:39:44
3826 forum posts
222 photos

On CNC lathes Z is movement parallel to the turning axis, X the cross slide, there is no Y! The X and Z nomenclature is not needed on a manual lathe so one might as well be consistent if you are going to label the axes.

In CNC the lathe is though of as a mill turned on its side and back with the spindle on the left.  This means that (radius mode) g code from a lathe can also be used on a mill where the work is held in the spindle and the tool on the table to the LHS of the spindle.  This is why slightly counter-intuitively a lathe thread in CNC is described as  RH when the chuck is rotating CCW as the operator looks at it - it's rotating CW if you look from the left hand end.

Edited By John Haine on 13/04/2021 08:55:08

SillyOldDuffer13/04/2021 10:10:35
Moderator
7130 forum posts
1571 photos
Posted by Jim Smith 8 on 13/04/2021 00:32:31:

...

Sorry if I confused on X,Y Z. In maths, X is horizontal, Y is vertical and Z up and down but then that's on a piece of paper.. Something else to learn! So what I initially mean't which you all understood, is my DRO scale is on Z but when the tool holder is set parallel, it has fine control in the Z axis along the ways, which isn't measured.

On another point, I have a quick change tool post that takes up to 16mm sq. tools and I just got some cheaper 12mm HST tools to practice with, since I don't want to ruin tipped tools. The height setting screw on the post seems to foul on the Warco flip down guard if I take a tool close to the chuck but is still a safe distance away. I'll post a photo later to show this.

I've also read the beginners first mistake with no saddle stops! Manually I can be very careful, but its what can go wrong if power feed is used that would worry me. I shall leave that alone at the moment.

Having been taught 'Y to the sky' when drawing graphs at school, I find X,Y and Z so confusing when applied to machine tools, I avoid them. Clearer to name the movement, as in NDIY's "long travel" and "cross-travel".

Although Hopper describes the chuck guard as a 'nanny-state overkill' I've put mine back on. This after a ball of swarf caught in the chuck jaws and was flung into my face with enough force to draw blood. A little higher and it would have hit my eye. It may be possible to adjust the guard on the switch axle to avoid the adjuster. Might be possible to move the microswitch :inside the headstock too: I can't remember.

Power feed isn't that scary provided the operator is on the ball. Before taking any cut, manual or powered, it's good practice to check the movement won't foul anything before starting the lathe. Obviously running the carriage into the chuck at high-speed is bad news, but so is a cutter or the tool-post hitting a jaw.

Under power, I note a point just before end of cut and disengage drive as soon as the cutter reaches it. Not difficult because power traverse is fairly slow and it disconnects quickly. Then finish off manually. Long traverse is more likely to end in a crash than cross-traverse. The adjustable stop on the bed is convenient. Best not to bump into it, but provided not overtightened it will slide, which might wake the operator up!

Operators soon learn to pay close attention to what they are doing: it's necessary to achieve good finish and accurate dimensions. The main risk is doing something stupid while concentrating on the cut - head too close to the work for a better view risks a scalping, fingers caught by the jaws etc. Distractions are bad too. Accidents happen disproportionally to Learner Drivers and old-hands. Learners because they don't see the danger and old-hands because they become gung-ho. Good news, Model Engineering is pretty safe - serious accidents are almost unknown. In comparison woodworking is a bloodbath!

Putting DRO on my milling machine transformed it. The benefit on a lathe is less obvious and I've not bothered to put it on my WM280 - yet. Perhaps the best reason for a lathe DRO is mixed metric/imperial working, and I'm almost 100% metric. But even then, I use a caliper or micrometer to turn to a diameter, and stops or visual reference points to control cuts: the dials are used to get close, not to provide absolute accuracy. As always much depends on what the lathe is used for. What works for me may not be good for others.

Great fun learning! Enjoy.

Dave

Journeyman13/04/2021 10:11:28
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953 forum posts
178 photos

As far as I am aware the current convention is that the lathe saddle (left/right) movement is referred to as the Z-axis and the cross-slide movement (in/out) is the X-axis. This is shown on a typical 2-axis lathe DRO display.

drodisp.jpg

If a three axis DRO display or universal display has been used on the lathe then it depends rather upon which port the lead has been plugged into as to whether Z or X increments as the saddle is used.

Not usual to turn up to a shoulder using power feed but for a long turned section I use the power feed for most of the cut and then just finesse the last bit up to the shoulder by hand. A saddle stop is useful for repeatability when cutting up to a fairly deep shoulder, lots of different designs, this is mine.

sadstopmk2.jpg

You can find more with drawing ** HERE ** this is for the WM250 (slightly smaller than yours) so check dimensions.

As has been said the top-slide is normally used for small angled parts, screw-cutting or small parts not needing much Z movement. I find that despite the coarse feed and copious backlash the saddle handwheel used carefully in conjunction with it's engraved dial is easily used for most jobs with reasonable accuracy, just needs practice. I often remove my top-slide and just use a cross-slide tool-post which tends to be more rigid.

toolpost.jpg

More details ** HERE ** again for the WM250 but easily adapted.

John

duncan webster13/04/2021 11:07:50
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3178 forum posts
55 photos

DRO is less use on a lathe than a milling machine, but I wouldn't be without it now I've had it. For a start it allows metric and imperial without a calculator, then when starting a job just take a skim off the bar, measure its diameter, set the X accordingly, touch the tool on the end, set Z to zero and you're done with measuring unless you're going for very good limits, even then you can get very close before stopping to measure. If you can understand the Chinglish you can tell it which tool is in use and it changes all the values to suit. As I said before I keep the topslide set over so it doesn't clash with the tailstock, so I apply Z with the saddle handwheel. On mine this works well. Perhaps someone needs to design a reduction unit for the WM250

You can just about do this with the manual dials, but you have to concentrate very hard!

not done it yet13/04/2021 11:08:47
5853 forum posts
20 photos

My 60 year-old lathe has a long travel auto-trip.

With the same depth of cut, feed rate and spindle speed it is generally good to 0.05mm, or better, consistently. Good enough for me.

It gets used a lot as it removes all the guesswork of stopping the carriage when close to the end of the cut - particularly when cutting close to the chuck.

Edited By not done it yet on 13/04/2021 11:09:45

John MC13/04/2021 11:54:23
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340 forum posts
38 photos

I have DRO's on the x and y axis of my lathes, no problem moving the saddle very small amounts even on a 7.5" lathe. That one has a dial on the saddle hand wheel, I used that for lengths before fitting a DRO.

I keep the compound slide (top slide) set at 45 degrees for chamfering, occasionally moving it for screw cutting and taper turning.

John

Journeyman13/04/2021 12:39:59
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953 forum posts
178 photos

Managed to put the same link in twice on earlier postsad The article for cross-slide toolpost should be ** HERE **

John

Roger Best13/04/2021 14:39:07
235 forum posts
31 photos

Hi Jim

You don't actually have a problem wrt DRO. The cross slide, as Duncan says, is mainly to facilitate some of the more complex processes, especially increasing depth of cut on a thread, for which setting it to 30degrees, (or 60 depending on your lathe) is ideal.

If you watch Ade's workshop he is particularly good at explaining the use of the DRO for incremental cuts. I am sure that as you use your machine you will get used to making fine adjustments and getting sub-thou' cut adjustments as a result.

Tony Pratt 113/04/2021 14:52:29
1503 forum posts
7 photos

Journeyman is correct in his statement, the Z axis should be saddle movement [left/right], I really need to relabel my Warco DRO as it still makes me think.sad

Tony

img_9868.jpg

John Haine13/04/2021 16:13:16
3826 forum posts
222 photos
Posted by Roger Best on 13/04/2021 14:39:07:

Hi Jim

You don't actually have a problem wrt DRO. The cross slide, as Duncan says, is mainly to facilitate some of the more complex processes, especially increasing depth of cut on a thread, for which setting it to 30degrees, (or 60 depending on your lathe) is ideal.

If you watch Ade's workshop he is particularly good at explaining the use of the DRO for incremental cuts. I am sure that as you use your machine you will get used to making fine adjustments and getting sub-thou' cut adjustments as a result.

No, the top slide is for that!

Journeyman13/04/2021 16:19:40
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953 forum posts
178 photos

Anyone who wants/needs to brush up on ** Lathe Nomenclature ** this may helpsmiley

John

Stuart Smith 513/04/2021 16:59:10
191 forum posts
26 photos

Jim

I have just bought a WM290 from Warco which has a factory fitted 2 axis DRO.

I haven’t used it in anger yet, but as Jason says, the carriage hand wheel movement is quite coarse at 0.5 mm per increment on the scale.
I am only a beginner having had a mini lathe for only a couple of years, but fitted a diy dro system to that using 4 cheap digital calipers, a homemade Arduino interface and the TouchDRO app on a tablet.

I have just ordered an extra linear scale from Warco to fit to the compound **LINK**

I am going to make a combiner similar to this one **LINK** to add the new compound scale to the existing z axis.

I suppose it depends on your level of experience and what you want to make, but I find it difficult to take accurate cuts with just the carriage hand wheel and use the compound.

Stuart

 

Edited By Stuart Smith 5 on 13/04/2021 17:00:15

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