Surface grinder question

How do surface grinders move the wheel (or table?) to give micron positioning diferences?

I would have thought that a straight thread wouldn't work. Is there some other secret?

Ta

Peter Fairbrother

Reply to
Peter Fairbrother
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Peter,

trapezoidal thread, of 0.1" pitch and is driven through a 2:1 reduction bevel from a large 9" diameter handwheel with 50 graduations so each division is 0.0001" (2.54 microns).

Reply to
David Billington

Correction the handwheel is marked 0 to 49 with tenth divisions between those so 500 marks on the wheel so even finer precision.

Reply to
David Billington

I'll get this right eventually, not been a great day for thinking. It is as I said originally each division is 0.0001" of an inch as 2 turns of the 500 division handwheel moves the head 0.1".

Reply to
David Billington

It tends to be an ACME or trapezoidal screw lifting the head. It's always under load from the considerable weight of the head, so backlash isn't a problem. Even though the screws and nuts can suffer significant wear over the years (especially if there isn't an automatic lubrication mechanism), the wear over short distances will be consistent, so a properly geared screw can produce very high precision movements. Silly as it might seem, the slight vibration that is inherent in running the machine ensures that any slack will be taken up.

Note that a heavy cut can lift the wheel-head within the 'play' of the screw and nut. This is one reason for doing a spark-out pass at the end of the job,

Mark Rand

Reply to
Mark Rand

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