Author Topic: Drilling large holes in thin metal using a twist bit!  (Read 1244 times)

Offline mattinker

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Drilling large holes in thin metal using a twist bit!
« on: January 21, 2017, 01:59:59 PM »
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
https://youtu.be/3jyp1RFvzyM

Offline awemawson

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Re: Drilling large holes in thin metal using a twist bit!
« Reply #1 on: January 21, 2017, 02:21:41 PM »
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.

Andrew Mawson
East Sussex

Offline Biggles

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Re: Drilling large holes in thin metal using a twist bit!
« Reply #2 on: January 21, 2017, 02:35:26 PM »
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

Offline mattinker

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Re: Drilling large holes in thin metal using a twist bit!
« Reply #3 on: January 21, 2017, 02:43:35 PM »
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

Offline awemawson

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Re: Drilling large holes in thin metal using a twist bit!
« Reply #4 on: January 21, 2017, 03:28:26 PM »
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 !!!!! )
Andrew Mawson
East Sussex

Offline Lew_Merrick_PE

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Re: Drilling large holes in thin metal using a twist bit!
« Reply #5 on: January 21, 2017, 08:33:06 PM »
Back in the 1960's (when I was an apprentice) some of the Industrial Supply shops sold sheetmetal drills.  They were similar in fluting to today's step drill bits for 3-5X the diameter of the bit.  Above that there was a section (full round) about .005 (inch)larger than the step drill area that "burnished" the final diameter.  I only have a couple left today as they "sprouted feet" with great regularity.

Offline mattinker

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Re: Drilling large holes in thin metal using a twist bit!
« Reply #6 on: January 21, 2017, 08:53:57 PM »
Just pointing out the the method I'm demonstrating requires no modifications to anything, if you have the right sized drill bit, all you need is a bit of rag! Andrew, if it judders about as you describe, you haven't got enough rag in there! I posted this as I thought it might be useful!!

All the best, Matthew

Offline SwarfnStuff

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Re: Drilling large holes in thin metal using a twist bit!
« Reply #7 on: January 21, 2017, 11:55:49 PM »
      This topic got my grey matter searching the dusty file section somewhere in me dandruff. I recall needing to enlarge a hole in sheet metal and no drill big enough. Cross the road to the neighbour (a man of many interests including silversmithing, wood work, gem stone faceting and polishing to name a few) to see what he might have.
      No, drill that size but he handed me a very large round metal file, told me to set it in the hole and wind it Backwards with the timber boring brace. Worked like a charm although it was no where near 29mm dia, now that would be a big file.
     Marvelous what is lurking back there in the memory-bank just needing something to prompt recall.
All the best,
John B
Converting good metal into swarf sometimes ending up with something useful. ;-)

Offline RobWilson

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Re: Drilling large holes in thin metal using a twist bit!
« Reply #8 on: January 22, 2017, 04:30:12 AM »
Good tip Matthew  :thumbup:



Rob  :dremel:

Offline mattinker

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Re: Drilling large holes in thin metal using a twist bit!
« Reply #9 on: January 22, 2017, 06:35:08 AM »
Thanks Rob!

 John B it's a good idea to get thes ideas out of the depths of our memories, they won't be there much longer!!

All the best, Matthew

Offline BillTodd

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Re: Drilling large holes in thin metal using a twist bit!
« Reply #10 on: January 22, 2017, 07:13:35 AM »
Odd, a few months ago a tool maker at work showed me this rag trick , I'd not seen it before , now it appears everywhere. New or like flu - just popping in to infect a new generation :-)
Bill

Offline Mark_Fisher

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Re: Drilling large holes in thin metal using a twist bit!
« Reply #11 on: January 22, 2017, 05:38:46 PM »
Thanks! Why does it work?

Sent from my GT-P3113 using Tapatalk


Offline mattinker

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Re: Drilling large holes in thin metal using a twist bit!
« Reply #12 on: January 23, 2017, 02:22:44 AM »
BillTodd I'm glad to contaminate, I feel that this kind of thing shouldn't be lost! Mark, how does it work? Well, I think that by filling up the space with rag, the tendency for the two flutes to move sideways is counteracted or at least reduced therefore cutting in an arc instead of a series of tangents.

Regards, Matthew

Offline awemawson

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Re: Drilling large holes in thin metal using a twist bit!
« Reply #13 on: January 23, 2017, 02:40:42 AM »
Probably first discovered by some hapless chap who caught his sleeve when drilling. When they were consoling him on the loss of his arm, they could at least compliment him on the roundness of the hole  :jaw:
Andrew Mawson
East Sussex

Offline Biggles

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Re: Drilling large holes in thin metal using a twist bit!
« Reply #14 on: January 23, 2017, 02:21:27 PM »
Mat, I posted before I read your comment but there are other makes and sizes also. I would have thought the punch method safer than a rag round the quill of a drill. (The rag could catch the vice and spin the lot round). But it is interesting.  :headbang:

Offline mattinker

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Re: Drilling large holes in thin metal using a twist bit!
« Reply #15 on: January 23, 2017, 02:40:22 PM »
Biggles,

have you tried my method? It isn't dangerous, it isn't "a rag round the quill of a drill", it's a rag between the drill bit and the work piece! I said that this was a method for drilling a hole, if you have the right sized bit, all you need is a bit of rag, which on a Sunday afternoon can get the job done!

Regards, Matthew

Offline ieezitin

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Re: Drilling large holes in thin metal using a twist bit!
« Reply #16 on: January 23, 2017, 06:53:54 PM »
I saw this trick on a Youtube video a few years ago, i tried it and works flawlessly and it is perfectly safe.. other than Andrews conclusion on how this was discovered I would like to know what Nit-Wit decided to toss a rag on the spot where the drill was going to bore into.... such is life.

Anthony. 
If you cant fix it, get another hobby.

Offline mattinker

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Re: Drilling large holes in thin metal using a twist bit!
« Reply #17 on: January 23, 2017, 07:48:40 PM »
 :dremel:
I saw this trick on a Youtube video a few years ago, i tried it and works flawlessly and it is perfectly safe.. other than Andrews conclusion on how this was discovered I would like to know what Nit-Wit decided to toss a rag on the spot where the drill was going to bore into.... such is life.

Anthony.

 :thumbup: