"Rollies Dads Method"

There is a fabled way of checking and setting the headstock alignment of a lathe to the ways which was discussed years ago on various groups that became known as 'Rollies Dads Method'. I can find references to the phrase but not a description of the method - does anyone have a link to the method?

I do remember is was a way of eliminating errors from slightly off centre or bent test bars, and I think it was as simple as averaging reading at both ends but would like to get back to the original source if possible.

AWEM

Reply to
Andrew Mawson
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Reply to
Dave Croft

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alignment

averaging

Thanks Dave, just what I was looking for !

AWEM

Reply to
Andrew Mawson

Not sure how useful it would be on your Master 2500! You're right in that it describes a method of avoiding an expensive test bar but relates all problems to "leveling" and "twist". I'm currently in a partial rebuild of my Kerry and headstock re-alignment is on the cards to correct a unwanted taper turn. I doubt that a piece if paper, where ever placed, would have much effect. I'll give it a whirl for diagnosis but might have to resort to an expensive test bar!

Charles

Reply to
Charles Ping

alignment

re-alignment

Charles,

The Master 2500, like most Colchesters, has the headstock female 'ways' ground not to touch the inverted bedways, and has a dowel pin and four hold down bolts. Alignment is done by slackening the bolts and pivoting on the dowel using a cunning adjuster that is set between the shears at the extreme left end of the headstock amd makes small movements possible. The pain is that to do a trial cut the gear train, which has to be removed to get at the bolts, must be re-assembled. I've set it using my 3MT test bar so I'm within 3/10 over 6" but having lent the bar out it came back with damage to the MT and isn't as fresh as when Arrand made it! Being fussy I want to tweak out that last bit of error if I can. AWEM

Reply to
Andrew Mawson

My understanding of RDM is that it allows alignment check without the need of an accurate test bar.

Surely how any error is corrected is not dependant on the method of alignment check?

Pat

Reply to
Patrick

Test bars? Whats that!

I have alway aligned my headstocks with the simplest method possible.

Thats simply to chuck up a piece of material (Usually steel) of a diameter not likely to bend under light cutting with an overhang, and as long as you wish to test over. Say 2"dia x 9"long.

Turn it over the length. Then mic it. Than it's just the fiddle of knocking, jacking or whatever the headstock to take any taper out.

Takes me about 15 minutes.

Wayne...

Reply to
Wayne Weedon

With Rollies Dad's method you can do exactly the same but don't need to cut anything.

Pat

Reply to
Patrick

And it is my understanding that it is mostly about correcting any twist in the bed of the lathe. Level is not essential. Imagine trying to do any machining in a ship or truck if everything actually had to be level. There is only a focus on level as a way of measuring twist in the bed. RDM allows you to correct any twist in the bed by packing up at one corner or another. It is not (as far as I recall, about changing the relationship between the headstock and the bed. Not least because that would not address any problems relating to a twist in the bed.

There is nothing unique about RDM. That just seems to be the name that has become associated with the technique here on th'internet. Reading several sources about lathe alignment all describe essentially the same process. It can be carried out with an expensive test bar if you want or you can cut one from any old bit of stiff material and measure from that. The technique does not depend upon the accuracy of the test piece. I have even seen it described in a form where a couple of thick washers were bolted to a hefty piece of threaded bar and turned in place.

Try it, you'll like it.

My oldish Myford now turns parallel to within my ability to measure it. Perhaps half a thou in 6 inches? Can't remember exactly. Just use a bit of patience. The leaded, free-machining patience works best.

Pete

Reply to
Peter Harrison

By averaging you are measuring the distance between the effective centerline of rotation and the bed/whatever - whether you are measuring for vertical alignment, horizontal alignment or twist is up to you.

One end of the averaged measurement is the effective centerline of rotation

- the other end is whatever you need, eg the horizontal distance to the bed at two different positions along the bed, the vertical distance from some point on the saddle in two different positions along the bed, or more complex measurements to measure twist.

The RDM averaging technique simply allows measurements to be made from the effective centerline of rotation - and you do not need to cut any metal, or use an accurate test bar. That is certainly quite different from the other usual methods, either cutting a fresh bar or using an expensive test bar.

Reply to
Peter Fairbrother

While I agree that there is little point in wasting money all this tal

of 'expensive test bars' is a little overdone. You can get them on eba for under £20 incl P&P(200047392770) and even top British test bars fro Arrand are not that pricey. Given the cost and blood pressure of ruinin a day's work or junking even a moderately priced casting I just can' see the point of not checking with one of these simple to use devices.

Each to their own, but what with accessories and tooling up I've spen a fair amount on my Super 7 and I really wouldn't want to spoil thi ship for a halfpenny of precision ground tar

-- Myford Mat

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Reply to
Myford Matt

Fine - but you don't actually need an accurate test bar at all - what would you want to use it for that RDM wouldn't do?

:!

-- Peter Fairbrother

May the long-time Sun shine upon you All Love surround you And the pure light within you Guide you all the way on.

Reply to
Peter Fairbrother

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