Calculate Error from uneven rail and reference

[John McNamara]

Hi mike

I also have a Taylor Hobson alignment telescope, not the digital just the older optical model, It is quite a fiddle to set it up and once set if it is knocked it will go out of alignment, having to set the targets and keep checking is slow.

I restored a lathe a while back and used wire, it was a Heidenreich and Harbeck 20 Ro 2.4 metres between centres. to check the straightness of the bed I attached the wire along the side of the bed level with the top of the V's and used an optical microscope. not fancy just a student microscope. the wire was firmly attached and did not need to be constantly checked it never went out of alignment being firmly bolted in position. The microscope was attached to a stage that was guided by the V ways was fixed over the wire and positioned with a Mitutoyo micrometer stem (They are available to be built into an instrument). error readings were taken with the micrometer after positioning the microscope over the wire. it worked very well.

I later purchased a cheap USB microscope About 40AUD it came with software. regrettably I lent it out and it never returned! Hmmm.

So I also need to buy a new one too with cross hair measurement software.
The trouble is there are hundreds of models available for a few quid.

Maybe someone in here has purchased one and can report on it?

Regards
john