ML7 centre height?

Does the centre height of the ML7 vary significantly? If not can someone tell me what it is precisely? Obviously a nominal 3.5", but is it really so?

I have yet to reassemble my ML7 (easier to renovate all the bits and pieces before reassembly!). So it isn't too practical to measure my lathe yet.

Thanks,

Andrew.

Hi there, Andrew,

Here is a drawing that I have posted before in previous threads:

It is part of Figure 21.2 of Geo. H. Thomas' book, 'The Model Engineer's Workshop Manual', page 240 in my copy, 1st edition. (sorry about the big white space at the bottom of the scan - I ought to have cropped it!)

GHT recommended that lathe owners (well, he actually said 'ML7 owners' but ... ) should measure their own machine and make a customised version of the drawing for their own lathe.

I measured mine by mounting a precision ground bar in a collet and measuring with a height gauge from the lathe bed to the upper surface of the bar, then subtracting half the diameter of the bar.

My measurement was 3.497", though maybe I really ought to write that 7 as a suffix.

Best regards,

Swarf, Mostly!

Swarf Mostly,

Did you take account of any eccentricity when the bar was in the chuck? Or did you centre it in the 4 jaw first of all?

My 3 jaw gives about 0.005" T I R eccentricity; the 3 jaw (well abused) on a pal's Raglan gave 0.036"!

Obtained these figures whilst making Centre Height Gauges to ease tool setting, (Neither of us uses QCTPs)

Howard

If you have any runout, either chuck a bar and skim it so you have a concentric bit to measure on, or take several readings at different chuck positions and average. I have measured my S7 in the past but it was so close to 3.5 I just assume that and never have an issue.

Thanks everyone,

It looks as if I assume 3,500" I will not be far out.

Andrew.

P.S Thanks Swarf for the detailed drawing, I do have GHT's book, but I can't remember the drawing. maybe time to read it again!

Howard,

I made my measurement with the bar held in a Myford Patent 2MT collet. That gave me sufficient accuracy for what concerned me at that time. I used a scriber blade in the height gauge - if I had used a dial gauge, previously zero'd on a known block, I could have checked for any eccentricity in the bar.

Very few of the more exotic instruments in my 'Metrology Department' have been purchased new - the height gauges seem to have been previously visited by the workshop gremlin that eats scriber clamps!

Andrew,

As I wrote in my post, the scan I posted is but a small part of GHT's Figure 21.2. It is at the bottom right-hand corner of the figure.

Best regards,

Swarf, Mostly!

Edited By Swarf, Mostly! on 24/08/2017 16:27:09

I recall being told by a former Myford fitter that the tailstock bases were made in varying heights so that the height of the tailstock centre could be made to correspond with the headstock centre. This suggests that the answer to the original question is "yes"

Thanks Swarf and ega,

You are quite correct as usual! It is indeed in GHT's book. Isn't it wonderful, how one can miss such an obvious figure in Gorge's book? Although I must have read it from cover to cover at least a couple of times, I somehow managed to miss it!

Ega, I think you are probably correct about the varying height, I seem to remember someone at Myford's told me something similar. I don't know how it came up, as you can see from the above, my memory isn't the greatest! It is probably why I asked the question, because I had this niggling doubt, probably that long forgotten conversation trying to surface.

Thanks all,

Andrew.

Thanks Swarf and ega,

You are quite correct as usual! It is indeed in GHT's book. Isn't it wonderful, how one can miss such an obvious figure in Gorge's book? Although I must have read it from cover to cover at least a couple of times, I somehow managed to miss it!

Ega, I think you are probably correct about the varying height, I seem to remember someone at Myford's told me something similar. I don't know how it came up, as you can see from the above, my memory isn't the greatest! It is probably why I asked the question, because I had this niggling doubt, probably that long forgotten conversation trying to surface.

Thanks all,

Andrew.