DRO for Chinese lathe/Mill

[garage nut]

Ordered DRO from Ali Express some 30 days ago.
200mm for x slide and 500mm for longetudenal.
In Rands 1200 compared to the stuff locally available(much fancier, but do you need it for the home?) of around 4 times that.
Free shipping meant 60 days delivery.......here in 30


Any pointers...can I leave the one end of the rail, the slider slides on free, trying to keep the x feed unit away from getting caught between the saddle and the tail stock, I hate it when I have to drill a hole and have to extend the tailstock to its limit simply because it is right up against the saddle and I can not move the saddle closer to the chuck.

[Ralphxyz]

re: "can I leave the one end of the rail, the slider slides on free"?

Absolutely it is even recommended that you do so on some DRO threads.

Some even recommend mounting one end on foam.

Sometimes the mounting fixed on both ends will twist the rail causing problems.

Ralph

[ibdennyak]

re: "can I leave the one end of the rail, the slider slides on free"?

Absolutely it is even recommended that you do so on some DRO threads.

Some even recommend mounting one end on foam.

Sometimes the mounting fixed on both ends will twist the rail causing problems.

Ralph

Thank you for your information. When I installed the Dro on my lathe the instructions were minimal, so I just kind of winged it. I only attached them on one side, and they worked well with good repeatability, so I did the same on my mill. I always told myself I would do a better mounting when I got a roundtuit, but now I feel like less of a hack.

Denny

[Toolmaker51]

Having mounted at least 10 DRO's/ and earlier optical readouts, I've never seen any terminal end portion un-suspended. Been able to qualify each by means of measuring rods, gauge blocks, and machines' own dials.
All readouts meant for general installation have jacking and hold down screws in both ends of rail mounts and each reader heads. They must be brought parallel to the axis being measured, in both planes, often within .0003 per foot. Deviations create sine errors, whence reader sees increments at a different rate than actual travel.
The jacking arrangements compensate for irregularities in machine body castings. Normally, kits are engineered for a 'style' of machine, the mountings cater to that concept. Figuratively speaking any system could be mounted on a machine, provided the scales [and reader installed] have sufficient length that exceeds maximum travel. It takes some mocking up to place rails and readers advantageously, without crimping leads, tugging on connections, or subjecting them to other damage. Few lead cables can be repaired by other than the original maker, if at all.

[edgrew]

These Chinese DRO's from Ali Express are cheap enough to experiment with. I have a Boxford CUD lathe and have fitted a 150 mm unit to the cross slide and a 500 mm unit for the saddle. Also small lathe/mill means less space for installation. You probably won't find a custom DRO kit for many of the older machines we use so be prepeared to look at the job for some time before you start cutting and drilling. An advantage of these magnetic units over optical units is that you can shorten them with a hacksaw if neccessary. I fitted the cross slide unit to the tailstock side of the cross slide as I didn't want the unit near the chuck. The compromise is can't get the tailstock quite as close to the chuck as I could before. I fabricated a cover for the cross slide unit out of some thin sheet from an old microwave unit. I couldn't bend a long enough piece for the saddle unit but used a piece of square plastic drain pipe sawn lengthwise down two diagonally opposite corners to make a length of angle, cheap and cheerfull but it does the job. It is a good idea to arrange some fairly robust stops so that the DRO sensor unit does not become the stop for travel. (Ouch!) I think that as our eye sight become worse with age the DRO is a good idea and very convenient to use so worth the effort.
There are lots of video fitting examples on Youtube. Have a look at a few to get a feel for the job first.

[Ralphxyz]

As Toolmaker51 says "Deviations create sine errors, whence reader sees increments at a different rate than actual travel."

Exactly, the reason given for leaving one end free or floating on foam.

If you do not want to take the time to get it exact and just want to have accurate DRO let it float and move on, unless of course you are getting paid to do the install.

Ralph