Enlarging Holes in Thick Plate

Gallery, Projects and General > How do I??

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awemawson:
All a bit too big to put on the table of the Bridgeport :bang:

The side plates with the holes are 1/2" mild steel plate. My plan was to cut a hole in another piece of 1/2" plate with a 1" Starrett hole saw. Clamp it over the 'to be enlarged' hole, centring using a suitable stepped plug, and using a mains hand drill cut the new holes.

I did some experiments with a couple of Starrett hole saws, and they were quite happy cutting 1/2" plate using their outer diameter as a guide.

Then I find I can no longer buy 1" cutters. Nearest metric equivalent is a 27mm, which actually when tested cuts a 27.5 mm hole. Now accuracy is not too critical - these are load bearing (but not revolving) pins - but 27.5 mm ie 2.3 mm is too much slack.

I am trying to keep to Starrett as they are good quality and seem up to the job and was amazed that 1" was no longer available

awemawson:
OK chaps you got in with replies while I was typing !

Yes I have a mag drill, but the access precludes its use :(

Yes I can turn bushes, I can make stepped pins and all sorts of other solutions, but I want to INCREASE the pin size not decrease it. There is a HUGE torque sideways when this is mounted, and I'm planning on using 1" EN24T shaft as pins

In a previous life this flail was just mounted on the 3 point linkage, and the differential torque on the lifting arms twisted and sheared the main cross shaft that the lifting cylinder acts on, and that was 1 1/2" steel of some sort. This new set up will mount directly on the tractor and not use the lifting arms at all.

porker:
If they cut oversize would a 25mm cutter get you close to the 1" diameter?

awemawson:
I had ruled out the 25mm, as oversize would be ok'ish but undersize would be a no-no. and 1" is 25.4 mm as we all know

.. . . . until I spoke to Starrett Tech Support in Scotland :scratch:

It seems that the 1" Starrett constant pitch hole saw sold in the USA is the very same 25mm hole saw they sell in the UK :bang:

What they do with the missing 0.4 mm is probably best left unanswered :lol:

John Stevenson:
Probably falls overboard on the way over the Atlantic. :palm:

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