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Old 15th Mar 2021, 4:21 pm   #8
David G4EBT
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Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
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Default Re: Enlarging an existing hole in a steel chassis.

Originally Posted by Nanozeugma View Post

I was wondering what would be the most appropriate tool to enlarge the hole neatly? I could, of course, use a half round file, but that would be a bit crude and possibly end up off centre to the existing holes for the fixing bolts.

Your thoughts much appreciated
It wouldn't be that much of a chore with a half-round file - to enlarge by 3mm only requires 1.5mm to be removed around the perimeter. That said, if you have a pillar drill, a 'step drill' (often incorrectly terms a 'cone drill', which is tapered -not stepped), is by far the best solution. They've been mentioned before, but are worth repeating. A step drill would do the job neatly and in a jiffy. A set of three isn't expensive, and they're excellent for cutting holes in metal, ABS project boxes, and especially acrylic sheet without snatching, and even cut their own pilot hole. EG:

Hope that might help.

Good luck with it.
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Last edited by David G4EBT; 15th Mar 2021 at 4:28 pm.
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