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Measuring acceptable deflection on a mill.

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trevoratxtal:
Please assist me in finding out what deflection your mill shows when pressure is applied downward on the head.
The reason is I would like to find what is acceptable to users  and what type of mill you use.
The measurement is taken with a clock gauge between the head and table , not the quill or chuck. motor not running!
My mill an old very heavy type shows 0.001 (one thou) with 50 pound pressure.
I  feel this is excessive or maybe I am not seeing the bigger picture.
The interest come about when taking a thin skim with a 8 tooth 2 inch cutter, I applied pressure to the drive cover to check it was in place, there was a distinct change in cutter swish, it also showed a a faint difference on the finish! this surprised me so I took further checks, hence my interest.
Many thanks folks.  :D

Trev

kwackers:
Mines in about the same ballpark. I can change the amount of overhang though, more overhang would obviously make it worse, less better.

All machines move when you apply force, usually more than you'd think. Even some enormous machines have measurable deflection when you apply moderate forces. IIRC the relationships between mass and rigidity are complex and non-linear.

John Stevenson:

--- Quote from: trevoratxtal on September 26, 2010, 11:49:09 AM ---
My mill an old very heavy type shows 0.001 (one thou) with 50 pound pressure.
I  feel this is excessive or maybe I am not seeing the bigger picture.


Trev

--- End quote ---

I think you are very lucky, my Bridgeport moves two post codes when the door is left open on a windy day.

Throw the dial gauge away it's only worrying you.

kwackers:
 :lol:

--- Quote from: John Stevenson on September 26, 2010, 01:13:37 PM ---
I think you are very lucky, my Bridgeport moves two post codes when the door is left open on a windy day.

Throw the dial gauge away it's only worrying you.

--- End quote ---

Bogstandard:
I remember watching a machinist pulling his hair out while doing a very long facing job on the lathe, truing up a 2ft diameter lapping plate. The surface finish went to pot every so often across the cut, and he just couldn't fathom it out. This was on a large Triumph lathe.

You could have timed his smoke breaks by the surface finish. Every so often, he would park his a**e against the lathe drip tray and roll himself a smoke, and light it up. Once he went back to check the cut, it was cutting perfectly, but the previous few minutes it had been cutting crap.

As John said, forget about checking, just don't lean on the machine while it is in action.


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