RMweb Premium Compound2632 Posted November 8, 2019 RMweb Premium Share Posted November 8, 2019 ... or how to insert a rectangular peg into a round hole. I'm building several 4 mm scale whitemetal wagon kits. I'm intending to use 3-link couplings with sprung brass drawhooks. To fit these, I need to open up a blind hole in the headstock to a slot about 2 mm high by 0.5 mm - 0.6 mm wide. Drilling a 0.6 mm hole top and bottom doesn't work out as the existing blind hole causes the bit to drift towards the mid-point. The bodger's method I've used with plastic kits, inserting a craft knife blade and waggling it, is ineffective. Broaches, being designed for rotary motion, are also no good. I think I need some sort of ultra-minature needle file but haven't so far located such a thing on the websites of the usual tool suppliers. Any suggestions gratefully received! Link to post Share on other sites More sharing options...
Baby Deltic Posted November 8, 2019 Share Posted November 8, 2019 The best thing would be small round diamond files or broaches. 1 Link to post Share on other sites More sharing options...
RMweb Premium Compound2632 Posted November 8, 2019 Author RMweb Premium Share Posted November 8, 2019 8 minutes ago, Baby Deltic said: The best thing would be small round diamond files or broaches. The miniature broaches I have a smooth-sided, so whilst good for opening up holes are no good for slotting. I've looked at diamond files; the problem I find with the suppliers' catalogues is that they are rather coy about sizes. Link to post Share on other sites More sharing options...
Baby Deltic Posted November 8, 2019 Share Posted November 8, 2019 (edited) This is always an issue. The trouble is, if you use normal needle files or rifflers, they will very quickly become clogged with white metal swarf. The best thing to do is wait until an exhibition where you can actually look at what you are buying. I’ve had similar issues where I have ordered diamond files and they have turned out to be way too big. Eventually I did get hold of a few small sets ideal for cutting slots for Scale couplings. Edited November 8, 2019 by Baby Deltic 1 Link to post Share on other sites More sharing options...
Miss Prism Posted November 8, 2019 Share Posted November 8, 2019 https://www.cooksongold.com/Jewellery-Tools/Vallorbe-55mm-Escapement-File,-Sq,-Cut-6-prcode-999-548 https://www.im3vet.co.uk/accessories-and-consumables/dental-burs/dental-bur-diamond-conical-pointed-859-med-gri 1 1 Link to post Share on other sites More sharing options...
JeffP Posted November 8, 2019 Share Posted November 8, 2019 Drill through the centre, thread in a piercing saw blade, cut upwards, turn it over, cut downwards. 1 1 1 1 Link to post Share on other sites More sharing options...
RMweb Premium Compound2632 Posted November 8, 2019 Author RMweb Premium Share Posted November 8, 2019 1 hour ago, Baby Deltic said: The best thing to do is wait until an exhibition where you can actually look at what you are buying. Well, I shall be at Warley, where both Eileen's and Squires have stands. Link to post Share on other sites More sharing options...
Devo63 Posted November 9, 2019 Share Posted November 9, 2019 I've have used mini side-cutter bits in my Dremel. You need to have a reasonably steady hand but it is relatively easy to do. I place the buffer beam/kit end on some scrap balsa and line up a steel rule along the slot line. Starting in the middle I carefully mill the slot up and down until it is the required length. 1 Link to post Share on other sites More sharing options...
RMweb Premium Compound2632 Posted November 9, 2019 Author RMweb Premium Share Posted November 9, 2019 47 minutes ago, Devo63 said: I've have used mini side-cutter bits in my Dremel. You need to have a reasonably steady hand but it is relatively easy to do. I place the buffer beam/kit end on some scrap balsa and line up a steel rule along the slot line. Starting in the middle I carefully mill the slot up and down until it is the required length. Interesting. Trickier on an assembled kit! A Dremel is a tool I don't have. Link to post Share on other sites More sharing options...
RMweb Gold Enterprisingwestern Posted November 9, 2019 RMweb Gold Share Posted November 9, 2019 Proper engineers avert your gaze now! Use a drill of the appropriate diameter as a file. Leave a small amount sticking out of the end of a pin vice and proceed firmly but carefully. Works for me. Mike. 2 5 1 Link to post Share on other sites More sharing options...
Flood Posted November 9, 2019 Share Posted November 9, 2019 (edited) You could saw through from the bottom of the headstock, insert a packing piece which is the size of hole you want to keep and then fill in the remainder with low melt solder. Using an old piece of brass, very slightly wider than a drawhook, as a packing piece may work so long as it wasn't soldered firmly in position. I initially thought of a plastic packing piece but that would probably melt when the low melt solder was applied. Edited November 9, 2019 by Flood 1 Link to post Share on other sites More sharing options...
PenrithBeacon Posted November 9, 2019 Share Posted November 9, 2019 Many wagon detail frets come with coupling plates. To fit them I drill a hole that will allow the coupling hook to go into the buffer beam and them cover the hole with the coupling plate and CA. Can be done in around two minutes. Cheers 1 1 1 Link to post Share on other sites More sharing options...
RMweb Premium Compound2632 Posted November 9, 2019 Author RMweb Premium Share Posted November 9, 2019 2 hours ago, Enterprisingwestern said: Proper engineers avert your gaze now! Use a drill of the appropriate diameter as a file. Leave a small amount sticking out of the end of a pin vice and proceed firmly but carefully. Works for me. Mike. That does sound like a way of working through my packet of 0.6 mm drill bits... 1 hour ago, Flood said: You could saw through from the bottom of the headstock, insert a packing piece which is the size of hole you want to keep and then fill in the remainder with low melt solder. Using an old piece of brass, very slightly wider than a drawhook, as a packing piece may work so long as it wasn't soldered firmly in position. I initially thought of a plastic packing piece but that would probably melt when the low melt solder was applied. I did think of the sawing through from below and filling in with low melt method earlier today, while doing the ironing, but not the ingenious idea of using a piece of brass to keep the hole open. 1 hour ago, PenrithBeacon said: Many wagon detail frets come with coupling plates. To fit them I drill a hole that will allow the coupling hook to go into the buffer beam and them cover the hole with the coupling plate and CA. Can be done in around two minutes. Cheers I have some MJT axleguard etches like that - the current version of Item 2299 - but the etched slots in the plates aren't tall enough for the coupling hooks so need extending... With this method, for the sprung hooks I'm using (mostly Slaters, or some rather similar-sized ones that come with Roxey/Chatham Kits), there would need to be a similar plate on the inside of the headstock for the spring to bear against. Interesting ideas, all of which I am mulling over. Many thanks all, keep them coming! Link to post Share on other sites More sharing options...
cctransuk Posted November 9, 2019 Share Posted November 9, 2019 2 hours ago, Enterprisingwestern said: Proper engineers avert your gaze now! Use a drill of the appropriate diameter as a file. Leave a small amount sticking out of the end of a pin vice and proceed firmly but carefully. Works for me. Mike. ..... and me - just be careful to ensure that the 'filed' slot does not wander off the vertical. Regards, John Isherwood. 1 1 Link to post Share on other sites More sharing options...
PenrithBeacon Posted November 9, 2019 Share Posted November 9, 2019 (edited) 42 minutes ago, Compound2632 said: That does sound like a way of working through my packet of 0.6 mm drill bits... I did think of the sawing through from below and filling in with low melt method earlier today, while doing the ironing, but not the ingenious idea of using a piece of brass to keep the hole open. I have some MJT axleguard etches like that - the current version of Item 2299 - but the etched slots in the plates aren't tall enough for the coupling hooks so need extending... With this method, for the sprung hooks I'm using (mostly Slaters, or some rather similar-sized ones that come with Roxey/Chatham Kits), there would need to be a similar plate on the inside of the headstock for the spring to bear against. Interesting ideas, all of which I am mulling over. Many thanks all, keep them coming! I haven't used springs on coupling hooks for the best part of 50 years! Just fold the hook's shank over across the back of the buffer beam and secure with adhesive. If the shank of the coupling hook is too large for the slot in the coupling plate then just file it down a little until it fits. Cheers Edited November 9, 2019 by PenrithBeacon 1 Link to post Share on other sites More sharing options...
Fat Controller Posted November 9, 2019 Share Posted November 9, 2019 22 hours ago, Baby Deltic said: This is always an issue. The trouble is, if you use normal needle files or rifflers, they will very quickly become clogged with white metal swarf. The best thing to do is wait until an exhibition where you can actually look at what you are buying. I’ve had similar issues where I have ordered diamond files and they have turned out to be way too big. Eventually I did get hold of a few small sets ideal for cutting slots for Scale couplings. It's worth spending a few bob on a 'file card'. This is basically a fine wire brush, which you use to unclag files after you've used them on soft material. 1 1 Link to post Share on other sites More sharing options...
Baby Deltic Posted November 9, 2019 Share Posted November 9, 2019 I do have a file card but the white metal gets right into needle files. Link to post Share on other sites More sharing options...
micklner Posted November 9, 2019 Share Posted November 9, 2019 Scrape the metal out with a old scalpel or similar blade. 1 Link to post Share on other sites More sharing options...
RMweb Gold Enterprisingwestern Posted November 9, 2019 RMweb Gold Share Posted November 9, 2019 https://www.cousinsuk.com/product/french-chalk Mike. 1 Link to post Share on other sites More sharing options...
micklner Posted November 9, 2019 Share Posted November 9, 2019 (edited) I have just tried these below for the first time on whitemetal kits, cutting the slot longer without any problems , I doubt if they would be as good on brass. https://www.ebay.co.uk/itm/Steel-Tool-Luthier-Replacement-File-Saw-Rods-Guitar-Filing-Set-Nut-Slotting-/202745733929?hash=item2f34966329 Edited November 9, 2019 by micklner 2 Link to post Share on other sites More sharing options...
sharris Posted November 9, 2019 Share Posted November 9, 2019 6 hours ago, PenrithBeacon said: Just fold the hook's shank over across the back of the buffer beam and secure with adhesive. A solution I often adopt as leaving it straight for a spring can foul rocking compensation units. 1 Link to post Share on other sites More sharing options...
RMweb Premium Compound2632 Posted November 9, 2019 Author RMweb Premium Share Posted November 9, 2019 1 minute ago, sharris said: A solution I often adopt as leaving it straight for a spring can foul rocking compensation units. Yes, I've run into this with fixed etched-brass fold-up axleguard units - I've either fixed the coupling hook solid or nibbled away at the axleguard unit. That wouldn't be possible with a rocking compensation unit. Link to post Share on other sites More sharing options...
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