Adjusting Myford ML7 Headstock Bearings
Mike Crossfield
However, I've so far had no replies about adjusting headstock bearings.
My ML7 is the early type with the white metal bearings. Although they
look like new, and the spindle is completely unmarked, there is slight
up and down play, and also some horizontal spindle end play. This was
with everything dry (the lathe had been unused for 25 years). When the
oilers were topped up, the up and down play was only just noticeable.
Does anyone know how much bearing play is acceptable, and how this is
adjusted. I notice that the bearing caps have brass shims under them -
presumably these can be changed for setting up? And how is end play
adjusted?
TIA
Mike
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Tony Jeffree
That is correct - you adjust the shims to change the play in the
bearings. There shouldn't be any detectable play in these bearings.
To quote the ML7 manual:
"For the purpose of bearing adjustment, a pad comprised of brass shims
is fitted between the two housing faces. This shim has a solid
appearance but is made of .002" laminations, and by inserting a
penknife bladeit is an easy matter to peel off the desired thickness
to allow the bearings closer contact with the spindle. After removing
a .002" shim it will be necessary to scrape or file some proportional
amount from the bearing half contact faces, giving a good seating to
bearing halves and housing cap; in effect a solid condition with
running clearance only between spindle and bearing. Whenever bearings
need adjustment use marking blue for contact check, carefully scraping
away high spots with a half round bearing scraper."
The point about the "bearing half contact faces" above is that the
white metal (or more recently, bronze) bearings consist of two
semicircular half-bearings (i.e., a ring of bearing material that has
been cut in half on a diameter); what you are aiming for is that when
properly adjusted, the bearing cap will clamp the two bearing halves
together with no gap between their flat "cut" faces. Hence, if you
adjust the shims, you should also adjust the flat faces of the two
half-bearings accordingly, so that when clamped together the two
halves have the effect of a single, solid bearing.
You should be able to get an idea of how many shims to remove by using
a dial indicator to measure the bearing play; of course, removing one
2 thou shim reduces the effective height of the bearing by only one
thou.
There is a threaded adjuster at the left hand end of the spindle that
controls end float & thrust bearing preload. Again, there should be
no detectable end float in the spindle. Again to quote Myford's
words:
"Spindle end thrust adjustment is made by the screwed collar at the
end of the Spindle, and care should be taken to ensure the elimination
of the end float without undue friction by over tightening."
Regards,
Tony
ChrisH
<mcros...@scigen.co.uk> wrote:
If I can add to Tony's remarks...
You should take measurements after the lathe has been used for
30min-1hour, you'll find clearances will change as the machine warms
up. It may well be OK after it's run for a while. If it can part-off
without jamming there's probably not much wrong with it.
When it occurs wear is usually not even, on the fornt bearing it
happens opposite to the thrust of the toolpoint (i.e., oval towards
the rear and top of the bore). Adjustments would be required to
maintain the spindle parallel to the bed (the scraping can correct it
but it requires experience).
If you just remove shims *without* scraping the bore the bearing will
run hot - I guarantee it.
Having tried this job a few times I decided it's not a trivial task to
do correctly!
ChrisH
speedy2
ChrisH <chr...@noeasynetspam.co.uk> wrote in message
news:j4mu9u81g3sisc29j...@4ax.com...
Be very wary of doing any damage to your bearings. They are Glacier Bearings
and are no longer available from anywhere. In the event of damge or gross
wear, Myford can onle sell you a totally new shaft, of different design,
using a different type of bearing. This will be expensive!
Dave.