Made from an inexpensive digital tyre depth gauge available on eBay this portable DRO shown in position to measure the travel of the cross slide on a mini lathe.
The Mk lll mini DRO is an evolution of a brilliant idea from Rob in Australia. Up to now setting up a digital read out system has been an expensive and labour intensive undertaking with questionable reliability. This little gizmo can be put together in around one hour at a cost of less than £10. It snaps into position thanks to the powerful rare earth magnets (neodymium) when required and can be removed just as easily.
I regard this DRO as ideal for use on the lathe to accurately measure travel of the cross slide and carriage. We can all get within a few millimetres when turning or boring but its that last few mm or thousands of an inch that gives us either the ‘spot on’ size we are looking for or relegates the workpiece to the scrap bin. No doubt with imagination this unit can be used equally effectively on the mill.
In Mk l and Mk ll versions a spring was an important element in the operation of this little unit. However in an Eureka moment my friend, also from down under, Aussie Jim, suggested scrapping the spring and using a small magnet on the tip of the probe.
Brilliant ! The following is a step by step guide to making your own DRO unit.
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- For around £5 buy yourself a digital tread depth tyre gauge, there are loads of them on eBay.
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- Remove the sticky label off the back and clean up residue with a solvent like brake cleaner.
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- Remove the CP2032 button cell and remember to buy a couple of spares at the next autojumble.
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- Take apart and relieve the pressure of the strip metal tension spring by straightening.
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- Turn up a 3mm dia steel sleeve (not stainless) to slip over probe and take two 3 x 1.5mm rare earth magnets.
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- The sleeve and the magnets are held in position with a dab of Araldite. Note the magnet protrudes slightly from the sleeve.
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- A 2mm thick 1″ square steel plate is recessed to take four 9 x 1.5mm rare earth magnets.
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- The DRO in position to measure the travel of the cross slide.
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- Mk l with external spring, Mk ll with internal spring and Mk lll with no spring at all !!!
Got to say John,
I thought this wasn’t really that useful at first (rarely go for accuracy on my lathe) But after reading through all of these projects I’m seeing potentially new ideas based on this design…. I’m going to have to have a bit of a play around with it but I’m thinking of accurate tail stock drilling too…. After adding DROs to my Mill and finding them so amazingly useful I’m warming up to all this digital stuff…. But I’ll try not to be the guy chasing the 0.001mm cut! :-)
Like you Ralph I find the DROs on my mill brilliant for precision milling and now the Micro DROs work equally well on my lathe and are so versatile in that they can measure either or both tailstock or cross slide with equal ease. Where accuracy is vital, like turning pistons and cylinder bores they are superb. I don’t need them for 90% of my lathe work but boy when I do they make life so much easier.
I’m glad you have been converted !
John
John P that’s sound like a great deal, could you post a link to where you bought them ??
thanks for all
Hi John,
Thanks to you, Rob and Jim for the DRO project. Brilliant! I’ve just ordered 4 Tyre units for £15 from China.
On another point, drill bits which are considered non salvageable, can be ground to a 60 degree point at the shank end and make passable tranfer punches.
John P
Hi John
Four for £15 sounds like great value.
I like your suggestion about the transfer punches. I never throw my duff drill bits away and your idea is another way to get new life out of them. I find them useful for crank pins and as locking pins to secure components on shafts.
Thanks for getting in touch.
John