agt613 Posted February 5, 2017 Share Posted February 5, 2017 Given the level of help I have already received, I am daring to start a topic to discuss how to cut holes of 4mm or so diameter in thin material without distorting it. So, ladies and gents, has anyone some advice to this poor scratch-builder? I know enough not to cut out the cab front before drilling the holes so that the material doesn't warp or twist because of its small size. I have found a standard 4mm drill just cuts a very warped hole that isn't actually round. I only have basic hand tools and intend to use 20 thou nickel silver on this one. Thanking you all in anticipation, Graham Link to comment Share on other sites More sharing options...
micknich2003 Posted February 5, 2017 Share Posted February 5, 2017 I would either mark out the hole cut it out with a piercing saw and carefully finish off with a round file, or solder the sheet to a thick piece of brass and drill through. In the smaller scales suitable size drills are readily available. Link to comment Share on other sites More sharing options...
Giles Posted February 5, 2017 Share Posted February 5, 2017 You can sandwich the piece between two sheets of MDF or similar and drill through the lot, keeping it clamped tight.... Link to comment Share on other sites More sharing options...
benachie Posted February 5, 2017 Share Posted February 5, 2017 I use a tapered cutting broach like this http://www.ebay.co.uk/itm/T-handle-Tapered-Bridge-Pin-Hole-Reamer-Woodworker-Cutting-Tool-5-16mm-Blade-Dia-/191724937010?hash=item2ca3b25f32:g:o1wAAOSw0UdXvWQK Start with a small hole and enlarge - you should be able to get a good smooth finish. Alan Link to comment Share on other sites More sharing options...
Guy Rixon Posted February 5, 2017 Share Posted February 5, 2017 If you solder together two sheets of your 0.5mm NS before drilling, you may find that the holes come out cleaner. The chance for the metal to flex and "chatter" is less. If you drill out in steps, less of the drill's cutting edge will be in contact with the metal. This may help to ensure that you have a consistent pressure on the cutting face which lessens the chance of the drill chattering or rubbing. I believe that drill bits with a 135 degree angle at the tip are preferred for drilling thin sheet. Normal drill-bits have a 118 degree tip. Link to comment Share on other sites More sharing options...
agt613 Posted February 6, 2017 Author Share Posted February 6, 2017 If you solder together two sheets of your 0.5mm NS before drilling, you may find that the holes come out cleaner. The chance for the metal to flex and "chatter" is less. If you drill out in steps, less of the drill's cutting edge will be in contact with the metal. This may help to ensure that you have a consistent pressure on the cutting face which lessens the chance of the drill chattering or rubbing. I believe that drill bits with a 135 degree angle at the tip are preferred for drilling thin sheet. Normal drill-bits have a 118 degree tip. Thanks to every one so far. Guy, how does one buy drills with 135 degree angle? Graham Link to comment Share on other sites More sharing options...
cobach47 Posted February 6, 2017 Share Posted February 6, 2017 just drill a lot of small holes around the edge join up the holes with a sharp scalpel then with a bit of sand paper wrapped around a paint brush handle gently sand away until you reach the right diameter Link to comment Share on other sites More sharing options...
sej Posted February 6, 2017 Share Posted February 6, 2017 Hi Graham, I would go for the drilling in stages from 0.5mm to big enough to get the end of a tapered cutting broach in as previously mentioned, Alan's ebay suggestion looks good. Also be very careful with thin sheet metal and large drills as the drill can catch and whip the metal round with alarming and possibly bloody results. Cheers Simon Link to comment Share on other sites More sharing options...
Guest Isambarduk Posted February 6, 2017 Share Posted February 6, 2017 I agree with Simon's suggestion to start with a small hole, say 0.8mm and then work you way up in steps; 0.5mm should be OK. It should be perfectly possible to drill all the way, particularly if you solder the sheet to some thicker material first, but I would probably go in smaller steps of 0.2mm towards the end and then finish off with a reamer or broach. One thing that's not been mentioned: you are attempting this with a pillar drill aren't you? If you are having to do it 'by hand' then a small hole and tediously opening up with broaches, correcting with a file if the hole wonders, is about the only sure way. Chain drilling holes around the perimeter is fine for larger holes but it results rather a lot of laborious cleaning up for such a small hole. David Link to comment Share on other sites More sharing options...
Londontram Posted February 6, 2017 Share Posted February 6, 2017 I like to start with a small drill and work upwards and sometimes finish off with a fine round file or as has been suggested wet and dry paper round a paint brush handle Never try to drill the hole out full size first time. Link to comment Share on other sites More sharing options...
Peppercorn Posted February 19, 2017 Share Posted February 19, 2017 Bit late to this discussion - I hope not too late. I keep a couple of wood drills for the purpose (4 and 5mm) and use them very carefully having firstly drilled a small pilot hole for the centre of the wood drill to sit in. Here are two sets made this way: I hope this is some use. Cliff Link to comment Share on other sites More sharing options...
ian@stenochs Posted February 19, 2017 Share Posted February 19, 2017 Use a conecut which has only one cutting edge and cuts a perfect circle. You need to drill a pilot hole first, 1mm is ideal, and then use the conecut at a slow speed. I have a small Black & Decker rechargeable drill which holds a small Jacobs chuck and runs at a very sedate pace you need to mark where to stop the tool, see the marker pen indicator on the attached photo. The smallest one makes 3mm dia holes and the larger goes up to 20mm. The only disadvantage is that the hole is tapered, however a final cut from the rear virtually wipes that out and in 10 thou metal is not noticeable anyway. Ian. Link to comment Share on other sites More sharing options...
Deano747 Posted February 28, 2017 Share Posted February 28, 2017 Hi All A bit late, but for future information; in aviation when drilling holes on thin sheet aluminium a drill with a long taper, as shown in the pictures, is used. A pilot hole being necessary. I'm sure the same could be used for brass. The one shown is 4.1mm but other sizes are available. Regards, Deano. Link to comment Share on other sites More sharing options...
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