meil Posted January 11, 2020 Share Posted January 11, 2020 On 10/01/2020 at 09:00, ColinK said: I’m currently building a chassis kit for a Pacer and have hit on a problem. Some of the axles will go through the top hat bearings, but some do not. The difference is tiny, probably less than one tenth of a millimetre, but what do I do to solve the problem. Any help appreciated. Emery paper wrapped around a cocktail stick. Twiddle until axle fits. 1 Link to post Share on other sites More sharing options...
RMweb Premium ColinK Posted January 11, 2020 Author RMweb Premium Share Posted January 11, 2020 Back home now after a long hard shift. So I’ve read all the replies carefully, many thanks for them, I have certainly learnt a lot. I’ve done some tests and measurements which I hope help. The holes for the bearings in the etched frames are about 3.76mm/0.148 inches in diameter. The brass bearings which go in these holes have an inside diameter of 1/8 inch (for an axle). The axles have a diameter of 2mm. The wheels are 12mm diameter (tread to tread). One side on each axle is insulated and I removed the insulated wheel off each axle for my tests (and so they can be fitted). The inserts in the bearings reduce the hole diameter from 1/8 inch to 2mm. I then tried each axle in all four pairs of bearings with the following results, All four axles will go through bearing set A. No axles will go through bearing set B No axles will go through bearing set C All axles will go through one side only of bearing set D. I think that points to the brass bearings or inserts being sub-standard. So the ideal solution would presumably be to source new bearings which fit the 3.76mm holes in the etched frames and have an inside diameter of 2mm. I’ve also noticed that one of the axles is not straight, I may have bent it when pulling the insulated wheels off. I think I know where I can get replacement wheels/axles. I’m hoping I can solve this with everyone’s help. Link to post Share on other sites More sharing options...
PenrithBeacon Posted January 11, 2020 Share Posted January 11, 2020 You can buy top hat bearings with an i/d of 2mm from Gibson, Branchlines. Cheers 1 Link to post Share on other sites More sharing options...
RMweb Premium melmerby Posted January 11, 2020 RMweb Premium Share Posted January 11, 2020 1 hour ago, ColinK said: I then tried each axle in all four pairs of bearings with the following results, All four axles will go through bearing set A. No axles will go through bearing set B No axles will go through bearing set C All axles will go through one side only of bearing set D. How accurate can you measure the axle diameters? I've just measured a selection of Hornby, Bachmann, Gibson & A.N.Other axles, using a decent micrometer and the variation was from +0.01mm to - 0.015mm from the nominal 2mm The +0.01mm was the Gibson axles the others were all 2.00mm or just under. I would be surprised if any bush within normal tolerance would reject those sizes. Link to post Share on other sites More sharing options...
RMweb Premium ColinK Posted January 12, 2020 Author RMweb Premium Share Posted January 12, 2020 All I’ve got is a Aldi digital calliper, but the measurements were consistent for all four axles. Link to post Share on other sites More sharing options...
RMweb Gold Enterprisingwestern Posted January 12, 2020 RMweb Gold Share Posted January 12, 2020 Rat tail file (which I would assume the OP already has) instead of specially buying reamers, we're not talking high end engineering tolerances here are we? Mike. 1 Link to post Share on other sites More sharing options...
micklner Posted January 12, 2020 Share Posted January 12, 2020 As said before its a very simple procedure. Buy a decent quality 2mm Parallel/Straight Reamer , it will do the job in seconds and will last a lifetime . You will also need a holder something like a hand held small drill chuck that can take sizes upto 3mm wiil do. Lots on ebay and the reamers as well. 2 Link to post Share on other sites More sharing options...
RexAshton Posted January 12, 2020 Share Posted January 12, 2020 Hi Colin If the job isn't urgent bring your bits to the next meeting or the exhibition and I'll sort them for you. Link to post Share on other sites More sharing options...
hayfield Posted January 13, 2020 Share Posted January 13, 2020 On 12/01/2020 at 08:39, micklner said: As said before its a very simple procedure. Buy a decent quality 2mm Parallel/Straight Reamer , it will do the job in seconds and will last a lifetime . You will also need a holder something like a hand held small drill chuck that can take sizes upto 3mm wiil do. Lots on ebay and the reamers as well. Mick I totally agree with you on this one, overtime just buy the tools you will commonly need, things like small tapered broaches and axle reamers are extremely useful if you plan to build kits in the future OK for some jobs you can get away with using a file or emery cloth, but you do run the risk of damaging the work Also change the bearings for 2 mm ones, things like these will always become useful in the future 1 1 Link to post Share on other sites More sharing options...
billbedford Posted January 13, 2020 Share Posted January 13, 2020 On 11/01/2020 at 21:48, ColinK said: I then tried each axle in all four pairs of bearings with the following results, All four axles will go through bearing set A. No axles will go through bearing set B No axles will go through bearing set C All axles will go through one side only of bearing set D. Did you try the axles in both ends of the bearings? Link to post Share on other sites More sharing options...
RMweb Premium ColinK Posted January 13, 2020 Author RMweb Premium Share Posted January 13, 2020 Thanks Bill, As I’ve fixed the bearings in the frames, I can only try putting them in the outside face of the bearings. Link to post Share on other sites More sharing options...
JeffP Posted January 13, 2020 Share Posted January 13, 2020 More suggestions, although my opinion (FWIW), would still be inverst in a 2mm reamer: Are the bearing inserts MAYBE fitted slightly cokeyed? Due to glue? Is there any glue in the actual bearing hole? Could any of the inserts have been ovalised on insertion? I'd be removing the modified bearings and fitting new 2mm ones, using a piece of silver steel, a 2mm drill or even the reamer to keep them lined up during fitting. 1 Link to post Share on other sites More sharing options...
RMweb Gold Happy Hippo Posted January 13, 2020 RMweb Gold Share Posted January 13, 2020 From what the OP has written, I'd have assumed that all the axles are from one source which would suggest a reasonably consistent diameter. So, if some bearings work, and others don't then the obvious solution is to ream the misbehaving bearings out to the correct diameter for the axles. The question I would ask is were the bearings all checked before you soldered them in place? If not you may not have soldered them in place so that they are in line with each other, Ditto making sure the 'frames' are parallel. As you can imagine, any misalignment would mean that the axle would slide into one bearing, but would foul on the lip of the hole on the other! As others have pointed out, once you get into the realms of kit or even scratch building, there comes a point where you do need to invest in some decent tools in order to progress. The kitchen table, Grannies old dress making scissors and Uncle Bob's b*stard cut file are only the starting point when it comes to move on from rtr. Link to post Share on other sites More sharing options...
RMweb Premium ColinK Posted January 13, 2020 Author RMweb Premium Share Posted January 13, 2020 Thanks guys, I'm certainly no expert I'm building chassis kits so all posts are helping me learn. I'm fairly sure the frames are square and the bearings clean inside and line up correctly, I spent a lot of time trying to get things right. I know where the axles come from so will order a replacement for the one I bent. I'll ask about replacing the bearings and inserts too. I'm gradually building up a collection of the more exotic tools as I need them. I do have a tapered reamer but even I realised that would only wreck the job. I'll let you know how I get on. Link to post Share on other sites More sharing options...
laurenceb Posted January 13, 2020 Share Posted January 13, 2020 If the inserts were cut with a tube cutter the ends will be slightly crimped, a quick cut with a cutting broach will soon clear it Link to post Share on other sites More sharing options...
RMweb Gold ianLMS Posted January 13, 2020 RMweb Gold Share Posted January 13, 2020 With all of the axle bearings I have had from a variety of sources (Gibson, Branchlines, MJT, Romford, DJH kits etc), some, if not all usually require a very tiny amount of fettling with a reamer to get the axle to go through, and spin freely. If you intend on doing this with any more axles, or plan on kit building, changing chassis' etc, I cannot recommend buying a set of reamers highly enough. It makes the job so much easier and safer! I only use tapered reamers. Not sure how square reamers work for opening out holes to the right size and get it perfectly square. In other words, how do you get a 3mm square reamer dead centre in a 2.5mm hole? Engineers I am sure will be scoffing at my stupidity, but I am always told, there is no such thing as a silly question. if you don't know, ask! Link to post Share on other sites More sharing options...
hayfield Posted January 13, 2020 Share Posted January 13, 2020 4 minutes ago, ianLMS said: With all of the axle bearings I have had from a variety of sources (Gibson, Branchlines, MJT, Romford, DJH kits etc), some, if not all usually require a very tiny amount of fettling with a reamer to get the axle to go through, and spin freely. If you intend on doing this with any more axles, or plan on kit building, changing chassis' etc, I cannot recommend buying a set of reamers highly enough. It makes the job so much easier and safer! I only use tapered reamers. Not sure how square reamers work for opening out holes to the right size and get it perfectly square. In other words, how do you get a 3mm square reamer dead centre in a 2.5mm hole? Engineers I am sure will be scoffing at my stupidity, but I am always told, there is no such thing as a silly question. if you don't know, ask! Ian I think you are talking about broaches, which are tapered and are used to open up holes. To be accurate I think what most of us are referring to in this instance is a STRAIGHT reamer, which we use in model railway situations to ensure a bearing has a consistent bore and or both bearings are aligned with a constant bore (either 1/8"th or 2mm for 4mm scale axles) You can get conical reamers for deburring and tapered reamers to open up a hole No doubt someone with engineering experience can elaborate (or correct me) further Link to post Share on other sites More sharing options...
RMweb Gold ianLMS Posted January 13, 2020 RMweb Gold Share Posted January 13, 2020 (edited) yes sorry - I have sets of tapered "broaches" for up to about 3mm holes/bearings and I have one tapered "reamer" for 1/8" bearings. I will now be looking for straight reamers to add to my ever growing tool kit! Are these suitable? https://www.cutwel.co.uk/hole-making/reamers/hsshsse-hand-reamers/hss-straight-flute-hand-reamer-yg-1-k1143-series I assume 3.2mm is closest to 1/8th Inch. Either way - To stay on-topic as it where, I rarely have a bearing which the axle slides through immediately without the need to take some of the burrs off from the milling/manufacturing process. Edited January 13, 2020 by ianLMS Link to post Share on other sites More sharing options...
Il Grifone Posted January 13, 2020 Share Posted January 13, 2020 (edited) Reducing the axle diameter (not easy as they are usually steel) will result in the wheels becoming a loose fit. As previously stated the correct tool is a parallel reamer. The problem is not the bushes being out of line (easily remedied), but that the bush is too small for the axle. Any play will result in the model bouncing about a bit which surely is prototypical for a pacer! Edited January 13, 2020 by Il Grifone Link to post Share on other sites More sharing options...
RMweb Premium polybear Posted January 13, 2020 RMweb Premium Share Posted January 13, 2020 A straight reamer has a slight (and not very long) taper at the start, in order to assist with starting and centering of the reamer in the hole. HTH 1 Link to post Share on other sites More sharing options...
billbedford Posted January 13, 2020 Share Posted January 13, 2020 4 hours ago, ColinK said: As I’ve fixed the bearings in the frames, I can only try putting them in the outside face of the bearings. So I see. Your photo shows a chamfer on the bore of the inner bearings so some questions Are all 4 inner bearings the same? If not, then chafer off the edge of the bore with a bigger than 2mm drill. You can do this holding the drill in a pin vice Do the axles enter partway into the bushes and then stop? In which case there is a burr on the inner face of the bush. The best way of removing this is with a reamer. If neither of these are true then I suspect the you have some bushes that have been made from drawn tube rather than being machined. Drawn tube is notoriously inaccurate in the bore. That being true I would suggest that tyou remove all the bearing and go an buy machined ones fro someone like Alan Gibson. 1 Link to post Share on other sites More sharing options...
Andy Reichert Posted January 13, 2020 Share Posted January 13, 2020 Sanding steel axles is usually a bad idea. Any sanding of steel axles will produce a rougher steel surface which will quickly wear a brass bearing. Andy 1 3 Link to post Share on other sites More sharing options...
RMweb Gold Enterprisingwestern Posted January 13, 2020 RMweb Gold Share Posted January 13, 2020 5 hours ago, Happy Hippo said: The kitchen table, Grannies old dress making scissors and Uncle Bob's b*stard cut file are only the starting point when it comes to move on from rtr. B*gger, that's where I'm going wrong then? Mike. 2 Link to post Share on other sites More sharing options...
RMweb Premium melmerby Posted January 13, 2020 RMweb Premium Share Posted January 13, 2020 19 minutes ago, Enterprisingwestern said: B*gger, that's where I'm going wrong then? Mike. I guess you must be using pinking shears instead of scissors Link to post Share on other sites More sharing options...
RMweb Gold Enterprisingwestern Posted January 13, 2020 RMweb Gold Share Posted January 13, 2020 6 minutes ago, melmerby said: I guess you must be using pinking shears instead of scissors ' Well, I do seem to finish up building a lot of station awnings! Mike. 3 Link to post Share on other sites More sharing options...
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