Edited By Wolfie on 11/01/2012 09:24:05

Edited By John McNamara on 12/01/2012 13:43:30

Edited By blowlamp on 12/01/2012 14:21:49

Edited By blowlamp on 12/01/2012 14:26:04

However in order to meet tool room spec both the cross slide and the headstock are interrelated.

Hence my comment "alignment is a set of compromises, each error must compliment the others." I wanted to set the headstock point towards me. Within the limits of my measuring equipment a square I wanted the saddle to be square to the bed.

It makes sense to me to use the headstock setting pointing 5 tenths towards the operator over 300mm as it counters the deflection of the cutting forces, and reduces the possibility of making the tailstock end of a bar bigger than the chuck end when plain turning.

When I set my lathe up I did the saddle first by lapping the cross slide until there was no binding with even hand wheel pressure throughout the travel (It was very good to start with so only a few hours work). obviously it mast also travel a straight line. in this case there was slight wear in the centre and maybe .001 to remove from the less used end that caused a slight bind when fully retracted towards the operator as you would expect. I can still see the manufacturers machining marks even after the tidy up.

Edited By John McNamara on 12/01/2012 16:52:07

After the cross slide was attended to the saddle was rebedded using Epoxy bearing material.... Search for MOGLICE and you will get the idea. However i used my own mix (Posted on this site under epoxy bearing material.)

You have attach adjusting jacks to the saddle, working on the inverted V's of the bed. I used the M6 wiper cover holes to attach a 12mm plate that holds the lock nutted jack screws so did not have to drill, a fair bit of work to make, these were used to set the saddle in the exact final position and height it will finally rest in. once all the testing is done you lift it off, apply the bearing material then set it back on the bed (which has been coated with release otherwise it will be stuck fast.) That was 4 years ago now, still perfect.

To set up the saddle I used an 18" reference grade square used from the front and the back of the bed, to reduce the error. I measured running the cross slide in an out with a dial indicator attached against the edge of the square. The saddle was set as high as possible bringing the leadscrew back up into proper line and the feed pinion into full engagement; no more slop in the handwheel.

I also set up a 300mm ground steel test bar in the headstock 3 jaw, (it does not have to be dead centre) then using an indicator (It must be a good one to .0001 accuracy and reliable not "sticky") mapped the min and max at 180 degrees every 20mm along its length; using the saddle which I had to manually push along the bed as it was on jack screws) You end up with a set of pairs of measurements. If you chart the difference between each pair of measurements, Excel makes it easy to visualise, you will get a very accurate map of where your headstock is pointing in relation to the bed. a tiny shim was all that was needed to position the headstock.

It was only after I got the required accuracy of both measurements (together with the rise of the spindle in the vertical plane) that the saddle was set.

In Connolly's book he mentions to methodologies for setting up a lathe; headstock first or saddle first. I guess there are differences of opinion.

It sounds like you achieved your aims John, but I wouldn't necessarily recommend some of your methods to others.

Edited By blowlamp on 12/01/2012 18:28:41

Edited By Stub Mandrel on 12/01/2012 21:28:41