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Drilling holes in Bridgeport / Warco mill

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Spurry:

--- Quote from: John Stevenson on March 19, 2016, 02:55:52 PM ---Yup,
Got the same machine but now got a few extras.

--- End quote ---

It was because of a little chat with John S at one of the shows that I actually bought this machine. Having previously bought one of their VMC mills, I thought I would never go near that company again. Hopefully this machine will be somewhat better than the last one.  :bang:

I will leave the big Hydrovane in the barn, and just use the little one for the mill. :-)

So thanks again to JS.

Pete

Spurry:
I am still prevaricating about drilling the holes in the casting shown in pic 2 above.

During my googling I have found pictures of older Bridgeports with the on/off switch mounted in the same postion.
Would anyone happen to know what size bolts they used?

In the meantime, I thought I would have a go at fitting the air-driven unit to the head. I had been told it just bolts on.

Containing a 62x35x14 bearing to support the top of the spindle is circular plate
with 6 radially spaced holes. Three are m8 and the others are counterbored M6 ish.
(The latter hold the plate to the head casting. The others are to jack-off the plate from head casting.)
None of them fit the base of the air unit.

Decided to make a new top plate. The air unit is nicely made with plain 6.50mm holes on a PCD of 110.
The Warco ones do not seem to be to any particular PCD, but somewhere about 114mm.

The plate did not fit centrally in the recess in the top of the mill head, so offset the centre
hole of my plate by 1.00mm and increased in overall diameter by 2mm.

I set up the new plate to drill the three 5.00 holes to secure the air unit, on the new mill.

A mandrel had been made to mount in the drill chuck to centralise the plate on the bed.
Moved the Y to check that my calculations had been correct, then revered the Y to re-centralise.
The DRO display read 0.00, but the mandrel was NOT over the hole. It was about 0.80mm out.

Thinking my eyes must be deceiving me, tried it again, but this time error was about 0.50mm.

Gave up at this point, and drilled the holes on my old Bridgeport.

I am at a loss to comprehend how a DRO could do such a thing. Would anyone have any ideas, or had a similar experience?

The motor was not running at all. The machine is fed from a rotary inverter to generate the required voltage.

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