Like many modellers, I have limit-ed budgets to spend on my hobby,and I longed to have DROs on bothmy milling machine and my lathe.The cost of two DROs seemed tobe rather damaging to my purse.Whilst fitting a DRO to my millingmachine (A Wabeco 1210) seemedto be fairly easy, the lathe, - a My-ford Super Seven – proved to bemore complicated due to lack ofroom. Whilst this article lists myexperiences at trying to obtain aneconomical and practical solutionon a Myford lathe, the examinationof the difficulties involved and thethings that need to be considered,are equally applicable to othersmaller lathes and to many othertypes of DRO.

Early Consideration ofDifferent Types of DROAround six years ago, I looked atseveral different ways of obtainingdigital position indication on mylathe before making a decision as tothe way I would follow in thisquest. The first, obvious, choice tolook at was the type of scales usedon industrial machines. Most ofthese were too large for the smallerlathe, but the Newall systemseemed to be compact and robust.However at around £1,200 in thosedays, the cost was way beyond mybudget, although I still do like theNewall system and indeed I think itis now fitted by Myford to theirConnoisseur lathe.The Chinese glass scales later cameonto the market at a much moreaffordable price, but they are muchbulkier than the Newall system andI still find them to be fairly imprac-tical on a small lathe, although of-

fering a good solution on manymilling machines.I considered using a digital calliperclamped to the cross slide for the xdirection only, and indeed one ortwo MEW contributors have donethis with some success. Howeverthis is very much a “make do andmend” solution in my opinion. Itdoes not easily cover the full saddletravel in the “Y” direction, lookspoor on the lathe, and gives younone of the useful features usuallyincluded with a good DRO systemsuch as local and global readingsetc. It is however very cheap.I seriously considered the magneticscales that were coming onto themarket at the time, but could notget these scales to fulfil my require-ments which were as shown below.

Digital Readouts onthe Smaller Lathe

David Haythornthwaite looks at the problems encountered when fitting a Digital Readout on thesmaller sizes of workshop lathe and describes his particular solution to these difficulties.

OverviewA Digital Readout (DRO)is a tremendous asset inincreasing productivity ona lathe. Having seen manyattempts at fitting digitalreadouts to model engi-neers lathes, I noticed thatmost solutions caused in-convenience and loss offunctionality of the lathe. Iset about trying to equipmy lathe with a DRO,maintaining all existingfunctions, whilst still look-ing to be very much anintegral part of the lathe.

A Digital Readout Fitted to a Myford Super 7

1

My Requirements for aDRO on my Lathe

1. I use a taper turning attachmenton my lathe, which, due to thelack of access to the back of mylathe, is permanently attachedand is protected from swarf etc.by a stainless steel cover whennot in use. Most types of DROmake the fitting of a taper turn-ing attachment (TTA) extremelydifficult or even impossible onthe smaller lathe due to the factthat the “Y” scale and / or theread head are too large to fitbeneath the cross slide when itextends over the back of thelathe, and at the same time clear-ing the taper turning attachment.I have seen “Y” scales fitted atthe front of the lathe bed, but inmy opinion they spoil the lookof the lathe and are usually stillin the way of many operations.

2. I did not wish the scale to be atthe headstock side of the crossslide as it would be vulnerable todamage when turning large di-ameter items. It would also bevulnerable to swarf and coolant.Additionally, on the Myford thefixing for the travelling steadywould be covered. I also fre-quently use this fixing point toattach a travelling swarf collec-tion tray to the saddle as shownin Photo. 2.

3.I wanted to re-tain easy access to all “T” slotson the cross slide from bothsides, and wished to retain therear tool post which is almostalways on my lathe. The rear“T” slot is also used for attach-ing to the TTA when turningtapers.

4. The Myford saddle is recessedat the tailstock side to allow thetailstock to slide between thebed “ways” and allow the tail-stock to be fixed as near as pos-sible to the headstock withoutunnecessary restriction of theavailable movement of the sad-dle - see Photo.2. Most smalllathes follow this pattern, andwhen fitting glass slides to thetailstock side of the cross slide,then the tailstock has to bemoved back from the cross slideto allow room for the slide. Thisleads to large overhangs of thetailstock.Of course it is possible to fit aglass slide to the cross slide(just) so that the entire measur-ing system, including readinghead, is either at the front or therear of the lathe, but the over-hang of the DRO is very incon-venient.

5. I wished to retain access to thegib strip adjustment screws onthe cross slide, which are situat-ed down the tailstock side of the

cross slide. The access to thesaddle clamp was also impor-tant, although this could beovercome if necessary.

6. Finally, I did not wish to drillholes in my lathe. This ideal didnot prove possible, although Imanaged to keep any surgery onmy lathe to a very minimum. Ialso wanted any solution to lookand feel right on my lathe.

7. I eventually decided on a solu-tion to these problems using anunusual DRO system. It worksextremely well for me, but if thereader of this article decides ona more conventional solution,the problems of space are thesame and the above commentsmay provide food for thoughtbefore embarking on the pur-chase of a system. Equally, mysystem was being fitted to a My-ford lathe, but most of the Chi-nese lathes now available offerthe same choices and the sameproblems to overcome.

The BW Electronics DROSystemA company called BW electronicsused to advertise, in ME and MEW,a digital readout system whichworks on an entirely different prin-cipal of measurement to other sys-tems. I have not seen anyadvertisements from them recently,but they do still sell these systemsfrom their website

There is very limited room for a DRO The BW334 Display With One Sensor

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www.BWElectronics.co.uk . I haveno connection with this companyother than as a very satisfied cus-tomer, and I have found them to bemost helpful to individual users.I bought the BW 334 unit, whichcame complete with a panel, a pow-er supply, and two sensors foraround £400. The System is shownin Photo.3 with just one sensor inthe photo. The sensors work in anentirely different way to glassscales, in that an extremely finestainless steel wire of 0.38 mm di-ameter (15 thou) is would round arotating, spring loaded, drum in thesensor, and as the wire is with-drawn, the encoder measures thedistance that the wire has beenwithdrawn. One big advantage isthat the sensors come completewith clips to attach to the lathe and/ or milling machine, so that thesystem can be switched betweentwo machines in literally 30 sec-onds, providing you use the sensorsas supplied. Now, DROs for bothyour mill and lathe for around £400cannot be bad value in my opinion.My first reaction looking at thesystem was “Well – yes -, it soundsgood in theory, but it cannot beaccurate in practice”. I have to saythat I have found the system to beextremely reliable and accurate inpractice over several year’s use.An added advantage of this systemis that the wire can be wrappedaround a groove on a drum on yoursimple dividing head and the sen-

sor can be programmed to readwhatever you like for a set dis-tance. Set it to read 2540 for a full360 Deg turn and then every read-ing of 20 will be the next tooth onyour 127 tooth gear wheel. Divid-ing head AND DRO for close to£400 !! However, - I digress.The sensors appear to be built withthe precision of a Swiss watch andI have found them to be very ro-bust. Photo.4 shows the inside ofone sensor, where the sprung wind-ing drum and optical comparatordisc are clearly visible.

The 334 display is fully featuredand comes in a die cast box. TheLED display is clear and the frontkeypad is wipe cleanable plastic.The unit in Photo. 3 has been inconstant use in my workshop for 5or 6 years now.The resolution of the display is0.0005” or 0.005 mm and the dis-play can be switched from imperialto metric and back at any time,maintaining correct readings. A“half” button allows readings to bedivided by two, and the X readingmay be set to read either radius ordiameter for lathe use. Either axiscan be either zeroed at any point orset to a defined reading through thekeypad. Local or global readingsmay be displayed or set and thedisplay switched at the press of abutton. As already stated the sen-sors can be set to read in any userdefined units and then easily re-

tu

rned back to the factory default.The readings are however lost onpowering down the unit.

Fitting The DRO to MyLatheHaving decided that I would usethe BW system, I looked at ways ofclipping the sensors to both mylathe and my milling machine. Fit-ting to the milling machine wasfairly straight forward and BWsupply the small black pipe clipsfor attachment to more than onemachine. The lathe, however, wasanother matter and I have usedthree separate methods of fittingthe sensors to my lathe. Each sys-tem worked and I shall describe allthree methods, explaining the ad-vantages and disadvantages of eachmethod.Firstly I should explain that mylathe was bought pre-used, or sec-ond hand as it used to be called.When I looked round the back ofthe cross slide, I saw that therewere two drilled holes in the back,as shown in Photo. 5, tapped 2BA,just as there are in the front of thecross slide to attach the lead screw.I assumed that these holes werethere on all ML7 lathes, but it ap-pears that this is not so and thatsomeone had previously addedthese (or do you subtract holes !!)to my lathe. However they gotthere, I decided to use these forattachment of my cross slide sen-sor, and if the reader wishes to

The Encoder Inside The Sensor The Holes In My Cross Slide

4 5

follow any of my examples exactly,it will be necessary to drill the crossslide. Of course, a bracket could bemade to clamp between the rear Tslot and the back of the cross slide,but my aim was to keep all T slotsfully operational.

First Method of FixingThe X Direction SensorAt first I attached the X directionsensor, by mounting everything atthe back of the cross slide with thesensor overhanging the taper turn-ing attachment cover, as shown inPhoto. 6. I created a bracket toextend rearwards from the crossslide. The bracket was actuallymade from a piece of 1” x 5/8” stripwith an 11 mm diameter bar setinto it. This bar was milled flat onone side and the sensor clips at-tached, so that the body of the sen-sor was 16 mm from the back of thecross slide. Sorry for the mixedmeasurements, but it was madefrom metal from the oddments bin.The other end of the measuringwire was clipped to a small bracketattached to the existing suds brack-et hole in the saddle. This workedwell, and it is important to note thatwhilst I attached the sensor to thecross slide and the wire end to thesaddle, it could just as easily havebeen attached the other way round.It is the relative movement be-tween the two that we are measur-ing. This choice becomes moreimportant when using glass scalesor magnetic scales. These can also

be mounted in a similar way, butthe overhang is even greater.Disadvantages were that the over-hang was considerable, and as Ihave very limited room at the backof my lathe, the sensor was alwaysbumping into something as the sad-dle and the cross slide were tra-versed. The blue item is a cover formy surface plate – and that didn’tmove when it was in the way !! Thesecond problem was that when thecross slide was withdrawn – i.e. forturning large diameters, the bracketcovered the saddle clamping screw.In the photo that would happen ifthe cross slide was withdrawn anyfurther.

The Z Direction SensorThe Z direction was very simple todo on my lathe. There is a row oftapped holes at the back of the My-ford lathe bed so that the TaperTurning Attachment may be at-tached at any point along the bed.In practice my TTA is permanentlyattached nearest the headstock andI have never had the need to moveit. This leaves unused holes at thetailstock end and these were used toattach a plate carrying the Z sensor,as shown in Photo. 7. The otherend of the wire was attached to theunderside of the saddle by drillingthe head of one of the saddle platefixing bolts and inserting a smallheaded bolt on to which wire termi-nating ring terminal was hooked.The modified bolt is shown in Pho-to. 8. It is important when locatingthe two ends of the wire, that the

run of the wire is exactly parallel tothe lathe shears in both the horizon-tal and vertical plane, if the unit isto give 100% accurate readings.Making the head of the fixing boltable to pass through the ring termi-nal, enables quick removal, and thewire tension keeps it firmly in place.The wire travels just beneath andbehind the lathe bed shears, butover the top of the TTA. I couldhave covered the wire with a travel-ling cover attached to the saddle atthe tailstock end, but the wire iswell out of the way and in manyyears of use, I have only twice dis-covered a small piece of swarfhanging on the wire. The sensorhas a PTFE wiper to assist in keep-ing the wire clean, and I have neverfound it necessary to cover it. This method of attaching the Zsensor has stood the test of time,and I have never needed to modifyit in any way.

Second Method of XDirection SensorAttachment.Having bumped my overhangingsensor into various things at the

The Sensor Overhanging The Taper Attachment.

76

The Z Direction Sensor Fitting

The Modified Saddle Plate FixingBolt

8

back of my lathe, I decided to try amore compact method of fittingthis. No damage had taken place,and little inconvenience. Howeverthe perfectionist in me thought thatthe large overhang of the originalsystem looked as though it wasdesigned by a consortium of HeathRobinson and three cousins ! Itherefore created a more compactsystem whereby the wire wouldtravel around a small ball race andthe sensor would be mounted at

right angles across the back of thecross slide.I had no idea whether taking thewire round a ball bearing wouldseriously reduce the accuracy, but Iconstructed the item shown in Fig.1 and it worked well, although itwas slightly less accurate in use.By tapping the cross slide, I couldget the reading to change by 1 thou– (0.0001”) on diameter, whichrepresented a change in the lengthof the wire of 0.0005”. I could livewith that for a while – and did use

it like that for a year. The unit isillustrated in Photo.9 andPhoto.10. For those readers wish-ing to construct something similar,I have shown the drawing of myunit in Fig.1.In order to mount the sensor in thisway, it is necessary to remove thering terminal from the end of thewire and to thread the wire througha home made PTFE wiper. I wasfearful of doing this at first, butafter several deep breaths and at-taching TWO clamps to the wire to

The Wire Passing Round a Bearing Sensor Mounting Details

9 10

stop it retreating into the unit, thewire was threaded up and the newterminating end was attached to thewire.In Photo.9 you will see that Idrilled the front of the saddle andfitted a post using a 6BA bolt. Thispost holds the end of the measuringwire. The sensor is mounted at theback of the cross slide as shown inPhoto. 10 and the wire is passedround a small ball bearing and thenthrough a PTFE grommet to stopswarf from entering the bearingarea. The end cap was removed inPhoto. 9 for clarity and the entirecover was removed in Photo.10.You can see that The wire is clearof all the T slots and of the gib stripadjusting screws. It was howevernecessary to exchange the boltswhich hold the top slide in place,for grub screws, as otherwise theoriginal bolts fouled the wire re-taining pillar when the top slidewas withdrawn.

This system worked well and was per-fectly accurate for my needs, althoughI never quite trusted it as much as astraight wire path. The wire was leftunprotected as I never got round tomaking the clip on cover that wasoriginally intended. As a result, I didhave to occasionally clean the wirewhen I was making a lot of swarf orusing a lot of cutting oil. (I use neatcutting oil and do not use suds) Themain problem with this system, forme, was that I use collets a lot andwhen working right up against theheadstock, the sensor body tended toget in the way of operating the beltchanging lever. This is the large blackknob in the upper right corner of Pho-to. 9. The sensor body had to extend tothe left of the cross slide in order notto foul the saddle. This is, however avery workable solution and I used itfor perhaps a couple of years.

The final solution for theX SensorMy thoughts turned to making asystem with a straight wire path,

but where the wire was protectedand enclosed in a telescopic guidetube. My cross slide had a maxi-mum travel of 160 mm from fullyout to fully in. The general layoutof the cross slide is shown in Fig. 2and this showed me that if I were tofit the tube below the level of the Tslots, but above the level of the gibstrip adjusting and clampingscrews, then the tube must have amaximum diameter of no morethan 8mm, and that the centre of thetube must be exactly at 14 mmfrom the top surface of the crossslide. The same restrictions wouldapply if I were to fit a more conven-tional DRO similar to the Newallsystem.I thought about making my owntelescopic guide tube system usingstainless steel tube, and then I rap-idly lay down until the feeling wentaway. I looked at telescopic radioaerials and these are cheaply avail-able from radio spares suppliers.

The Sensor and Magnetic Wand Friction Pads on Telescopic Section

11 12

The Finished Guide Tube Attachment Brackets Added

13 14

Some however are very thin andflimsy. Finally my eyes came torest on the magnetic part retriever(wand) that I used for retrievingthose parts that walk under thebench from time to time (entirelyon their own I may add). This wandextended to around 500 mm andreduced to 125 mm, having 4 tele-scopic sections – see Photo. 11, -the outside tube was however 9 mmdiameter. I estimated that, on mylathe, the tube need only extend toaround 350 mm and collapse to 175mm, so a 3 tube “telescope” wouldbe perfectly adequate for my needs.

Adapting The SensorOn removing the pocket clip fromone end of the “wand”, and themagnet from the other end, it ispossible to push the individual sec-tions through each other to disas-semble the telescopic section. Thesections are held together by fric-tion pads as shown in Photo. 12and I considered that the wand wasa little stiff in action. The frictionpads were sanded with wet or drypaper and lubricated with thin oiluntil the friction needed to extendthe wand was just right, and thewhole thing was assembled again.Removing the outer 9 mm tube leftme with three sections of 6, 7 and 8mm respectively. The thread on thesensor box is 1/8” BSP, so a 1/8” to¼” BSP reducing nipple was pur-chased and this was fixed on to theend of the wand with Loctite. I

intended to bore out the reducingnipple to be a tight sliding fit on the8 mm tube, but this proved to beunnecessary as it was already atight sliding fit as supplied.With a cup of calming tea, and withsoothing music playing in the back-ground, I nervously removed theexisting guide tube from the sensor,clamped the wire firmly at the sen-sor side of the tube and removedthe wire end stop yet again. Thewire was then threaded through thenew telescopic tube and through ahollow rivet which was just toolarge to pass through a hole drilledat the narrow end of the tube. Aknot was made in the end of thewire so that it could not passthrough the rivet, and it was thensafe to remove the wire clamp andto screw the telescopic guide tubeinto the sensor. The end of the wirewas Loctited prior to cutting to stopstrands unravelling. The result canbe seen in Photo. 12 and you willsee that I have temporarily placed asmall piece of tape onto the end, sothat it is impossible to push thesmall diameter tube too far in.The attachment brackets have beenadded in Photo. 14 and you will seethat the sensor will attach to therear of the cross slide, whilst theend of the tube will attach to thefront section of the top of the sad-dle. For the eagle eyed readers whonoticed the extra hole in the brack-et, it is there to allow the 2BAsetscrew to be passed through the

rear mounting block and to allow itto be tightened by a long hexagonalkey.Great care was taken in the makingof the above bracket, as the centreheight of the tube had to be EX-ACTLY 14 mm from the top sur-face of the mounting block andcross slide. Also the horizontal po-sition of the centre of the tube wasmade to be 5 mm from the edge ofthe mounting block, so that cuttingfluid would be able to run down the1 mm gap between the cross slideand the larger guide tube.Once the X direction sensor wasbolted to the lathe, it looked com-pletely unobtrusive see Photo. 15.It does not hinder the use of thelathe in any way whatsoever and isproving to be an absolutely superbaccessory. It does make the saddleclamp slightly more difficult to usehowever, as I cannot fit a socketspanner to it, and I shall probablymake an extended clamping handleto overcome this. Photo. 16 showsthe DRO being used with a taperturning attachment, where it is notin the way. Using a DRO makes

The Guide Tube Fitted To The Lathe Using With a Taper Turning Attachment

15 16

Tailstock Stop

17

setting a TTA an absolute dream.Set both readings of the DRO tozero, wind on the saddle by 100mm, read the X reading and workout the angle. Do however be care-ful as to whether the DRO is read-ing radius or diameter when doingthis.I have lost only 10 mm of tailstockmovement by fitting the DRO andPhoto. 17 shows that I have fitteda stop to the tailstock by drilling thesliding section and tapping 4 mm

for a tailstock stop. This extendsonly 10 mm and protects the DROby causing the tailstock to hit thesaddle, whilst leaving a gap of 10mm for the DRO tube.Not every reader will have a My-ford and not every reader will wishto use the BW system of DRO.However I hope that I have indicat-ed some of the questions that needto be answered before laying outmoney on a DRO system whichwill probably be complicated to fit

on a small lathe. The advantage ofthe BW system is that it telescopes.A glass scale, fitted to the crossslide will always be at the maxi-mum length required, and with(say) 160 mm of cross slide travel,it is amazing how long a glass scaleneeds to be, if you are to keep thereading head away from the crowd-ed area in the centre of the lathe bed.