Harrison M250 bed/tailstock setup

Hi, my first post so hopefully its in the right place etc,

I am doing some moderatly high precision work on an M250, had had it ages and spent ages getting it level and setting things up, it works well however...

If i set the tailstock on something long i can get it good, can get it to turn within 0.01mm tailstock to headstock end at say 300mm long, but then if i turn somethign short say 50mm i have to adjust the tailstock by about 0.05mm else it tapers the item by apx 0.1mm,

The beds in pretty good condision and so is everythign else, i think its fairly straight as if i put something thick in it without the tailstock it will turn bang on for 80 or so mm with no taper,

if it wasnt for the above i was thinking it wasnt level and that the tailstock was compensating for something which varied, maybe this is the issue,

If anyone with more expenience can throw any light on it i would be delighted,

i really want to get things to turn within 0.02mm over a foot and not need to adjust the tailstock for diffeent lengths which i think should be possible,

Thanks,
Ralph

Is it bolted down to the floor ?

Its sitting on ajustable feet,

Ralphh85 said:

Its sitting on ajustable feet,

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Sounds like the bed is twisted a wee bit.

if this is the case working out which way is breaking my mind,

if its set for a short item, then i put in a long item the tailstock has to move backwards by 0.05mm or so,

I kind of hope your right as that should be fixable,

You first level the bed
Then you adjust the headstock

In your case I think the bed is twisted and the headstock compensates for that twist
Always first level the bedways Then do a 2 collartest to see if the headstock is alligned properly with the (now alligned) bedways

Peter

I looked up the manual and it seems the headstock of the Harrison M250 sits on the V of the bedway
Sometimes the V is a bit wider as the V of the bedways making it adjustable anyhow
But I think the M250 has a V in the headstock that fits the V of the bedways
That makes it impossible to adjust the headstock without scraping
However if you or a previous owner ever took off the headstock there is a chance of loose bolts or dirt in between the V
If I was sure the bedways were leveled properly I would take off the headstock
Clean deburr clean clean and clean once more and put it back with all bolts tightened properly But clean it once more with a clean cloth before putting it on
I had that issue once with a Weiler Commodor lathe
There is a chance even you can adjust the headstock slightly by torking one bolt more as the other

Peter

chances are your tailstock quill is not parallel to the headstock spindle.
my guess is that it is pointing down.
you might be compensating for that fact while you are adjusting it in the horizontal plane.
i would check that first.

janvanruth said:

chances are your tailstock quill is not parallel to the headstock spindle.
my guess is that it is pointing down.
you might be compensating for that fact while you are adjusting it in the horizontal plane.
i would check that first.

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That would only count for if the stick out of the tailstock was different for a good amount
And that was not mentioned But could be possible

Peter

Peter from Holland said:

That would only count for if the stick out of the tailstock was different for a good amount
And that was not mentioned But could be possible

Peter

Click to expand...

it would be more if the quill were to be extended further, that is exactly how to detect whether the whole tailstock is low or the bottom is lower towards the headstock