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Gallery, Projects and General => How to's => Topic started by: mattinker on January 21, 2017, 01:59:59 PM

Title: Drilling large holes in thin metal using a twist bit!
Post by: mattinker 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
Title: Re: Drilling large holes in thin metal using a twist bit!
Post by: awemawson 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.

Title: Re: Drilling large holes in thin metal using a twist bit!
Post by: Biggles 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
Title: Re: Drilling large holes in thin metal using a twist bit!
Post by: mattinker 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
Title: Re: Drilling large holes in thin metal using a twist bit!
Post by: awemawson 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 !!!!! )
Title: Re: Drilling large holes in thin metal using a twist bit!
Post by: Lew_Merrick_PE 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.
Title: Re: Drilling large holes in thin metal using a twist bit!
Post by: mattinker 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
Title: Re: Drilling large holes in thin metal using a twist bit!
Post by: SwarfnStuff 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
Title: Re: Drilling large holes in thin metal using a twist bit!
Post by: RobWilson on January 22, 2017, 04:30:12 AM
Good tip Matthew  :thumbup:



Rob  :dremel:
Title: Re: Drilling large holes in thin metal using a twist bit!
Post by: mattinker 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
Title: Re: Drilling large holes in thin metal using a twist bit!
Post by: BillTodd 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 :-)
Title: Re: Drilling large holes in thin metal using a twist bit!
Post by: Mark_Fisher on January 22, 2017, 05:38:46 PM
Thanks! Why does it work?

Sent from my GT-P3113 using Tapatalk

Title: Re: Drilling large holes in thin metal using a twist bit!
Post by: mattinker 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
Title: Re: Drilling large holes in thin metal using a twist bit!
Post by: awemawson 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:
Title: Re: Drilling large holes in thin metal using a twist bit!
Post by: Biggles 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:
Title: Re: Drilling large holes in thin metal using a twist bit!
Post by: mattinker 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
Title: Re: Drilling large holes in thin metal using a twist bit!
Post by: ieezitin 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. 
Title: Re: Drilling large holes in thin metal using a twist bit!
Post by: mattinker 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: