Hi Ignatz the terminology I would understand as to the movement of the saddle in such a matter is called crabbing. I usually is caused by the jib strips being loose or curved by wear. if you put a dial indicator on the saddle with the pointer resting on the side of the bed and move the saddle backwards and forwards and note the movement as to direction. You can check if the gib strip is lose at the same time and repeat the check after tightening it up. if the saddle becomes to tight to traverse towards the tailstock after tightening the bed is worn and needs attention. if the gig strip is worn you can mill a small amount off to flatten it and possibly relieve the centre area a few thou may help as well. have a look at the bed thickness as well you cam measure the thickness at various places along the length to see if there is any difference. let us know if this helps please.

David

That is the major shortcoming of a V bed , two directions of thrust are adjusted by one movement.

Adjust for wear close to the chuck will make the saddle so tight when it moves back.

You could start with a feeler gauge either side of the saddle, but do not move the carriage during the test as you may be rocking the saddle and get a false reading. If you cannot get a 0.0015" or 0.04 mm feeler gauge into any gap this can only be good news.

If the blade does enter, check if it goes in by the same amount each side. This will tell you if the wear is equal. I would expect the greatest wear on the right-hand side, but you might be lucky and have it symmetrical.

You can go to town with micrometer blue if you feel confident. Provided you have found wear then I would scrape the central portion before I put on any blue. Ideally setting the Saddle up vertically such that a short ground roller resting in the dovetail, can be used in conjunction with a clock to check where to scrape.

If the back face of the saddle is machined you could get away with a micrometer and a roller, after removing any paint.

Getting right into the corner can be difficult if the scraper is not thin enough. A lot depends on how big the flat is on the corner of the bedway dovetail.

Regards

Gray.

You have to remember that you are exaggerating the error by having the clock extended.

There is a back up plan, and the lathe can always be salvaged. Odd items for ML 10's always appear for sale.

Regards

Gray,

I think you are chasing completely the wrong issue. If having to move the cross slide back at the end of each pass is your biggest problem in life you are truely a lucky man. The only thing that should matter in this area is whether your alignment of the headstock and lack of bed twist allows you to cut a parallel bore.
The place where this movement matters is when the carriage is locked and you are facing off a big flat plate. You just need to determine a method for getting the carriage in the right poition for this operation to be true before locking.

Glad my advice worked out, with errors like that I would leave well enough alone and modify my method of working.

A Clock (DTI) is truly a wonderful thing, as are feeler gauges which are very often over looked. A clock in skilful hands can save a lot of worry when it comes to machine tools and wear.

One thing I would do is make some felt wipers with metal protectors for that bed. These will slow down any future wear and keep the bedway lubricated for longer.

Regards

Gray,

Two comments.

Firstly, moving the Cross Slide while making measurements along a bar introduces errors because of the backlash. So, my advice is don't introduce another variable and possible source of error. Lock as many movements as possible.

Secondly, Boring bars are flexible, being long and slender and so deflect more easily than a short rigid external turning tool. What you are seeing is a "spring cut".

Even if you stop the lathe and then withdraw the boring bar, restarting will show the tool taking another spring cut. probably, it will take three or four before it no longer cuts.

So, if you want a precise bore size, it will pay to start taking spring cuts a couple of thou (0.05 mm) before you reach the desired finish size; with the Cross Slide locked.

HTH

Howard..