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Drilling large holes in thin metal using a twist bit!

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mattinker:
Hi,
A short video about drilling holes in thin metal sheet using a twist drill bit, in this case, a 29mm hole in 2mm plate.

I hope it's useful to someone!

Regards, Matthew

awemawson:
Matthew, back in the mid 1960's at school I was making my first oscilloscope, using an ex WW2 radar tube - a VCR97 as it happens, and I needed to make up a chassis with several 'valve base size holes' for EF50's. The metal work master showed me that trick, which sort of worked but not as well as your demonstration.

These days I'd use a Q-Max, or a stepped drill, or maybe bore it out. The other approach is to clamp the sheet between pieces of timber.

Biggles:
Back in the 60's when i was at school, i was also shown how as above. Sandwich your plate between two pieces of wood clamped together, or you can purchase a sheet metal hole punch for the size you need. 
https://www.cromwell.co.uk/shop/hand-tools/punches-wad-and-hole/60mm-round-hole-q-max-cutter/p/QMX0451124B

mattinker:
This is a 29mm hole, in my opinion, the rag trick is so simple, if you have the right sized drill bit, it's better than two pieces of wood! You have a 29mm step drill Andrew? The plasma table beats all!

Regards, Matthew

awemawson:
Biggles - your Cromwell link is to a Q-Max as per my comment earlier !

Matthew - my step drills are in 2 mm increments to 40 mm so 28 or 30 mm in your case - you'd be a brave man to entrust a hole to my Plasma Table until I've fine tuned it, but I'm definitely getting there  :lol:

(As it happens those holes I needed (when I was probably 14) for my EF50 9 pin Loctal based valves were 30 mm so close to that that you demonstrated, where as I can remember my chassis jumping all over the place !!!!! )

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