Iwould agree with you. I think it's pointless to make a part if you can get it reasonably easily/cheapky. In the UK there are model engineering enthusiasts who make scale reproductions of steam locomotives, and even make all the nuts and bolts themselves to get the right (scale) size heads, etc. I have great admiration for this sort of work, but I don't intend to do it myself. I have a reasonable workshop, including a lathe, but I got the latter to make bits for computers (OK, one day I am going to start making a clock screwcutting) if I can get an acceptable part from one of the normal suppliers. But if I need some special mouting pillar with a threaded end, then I make it. [OK, one part I have _not_ been able to get ready made in the UK is the jackposts for the HPIB connector (M3.5 thread). When I needed those, I made them]. I haev never done gear cutting, although I understand the principles, and have a dividing head. But the way to learn, IMHO, is to have a go and see whwt goes wrong. If I attempt to make a gear for one of these plotters and it doesn't work out, all I've wasted is a bit of metal. I've not even wasted any time, because I will hopefully learn from the experience. Problem is, there are an infinite (litterally) different pitches, numbers of teeth, etc. Finding a workable replacement for one gear in a train is not foing to be easy Due to lack of workshop space, many UK model enginers, etc do milling in the lathe. You put a 'vertical slide' on the cross slide, and put an end mill or slot drill,. or whatever in the lathe mandrel. Obviously the capacity (in terms of length of movements, depth of cut you can take in one go, etc) is a lot less than a real milling machine, but it's enough to make an awful lot of parts. You might as well use a clockmaker's wheel cutting engine. That lets use rotate the blank using a division plate (normally with no step-down gearing between the division plate and the blank, unlike a dividing head), and cut the teeth using the appropriate rotating cutter. Doing it with a file, even with a jig, would be very hard IMHO. To get all the teeth cut to the same depth would be a problem. Is there a good reason _not_ to get a small lathe? I am not sure how much a Taig/Peatol or a Unimat costs these days, but it's not _that_ expensive, and if not misused will last a long time. Yes, it's a small tool, but it's big enough for this sort of job. I've read said book. One day I am going to make it (with a few modifications). Yes, you need a lathe, particularly to make the injection cylinder and ram,. but it doesn't look that hard (famoug last words). My attitude to this sort of thing is 'have a go'. Yes, I'll make mistakes. Things won't work out first time (or second time, or...). But all I waste is a bit of metal (that will probably get used for something else later anyway). I am not risking a classic computer by making parts for it. I am convinced the world would be a better place if more people tried to make things... -tony

On 6/5/2006 at 3:18 PM Chris M wrote: You can just throw your bad one away and get a new one. There's a guy selling 825 printers for $10 the each, NOS on Yahoo!: http://tinyurl.com/e4sgx But I'd make sure he's for real, first. Cheers, Chuck

That was my first thought. These gears don't fail because they wear out in use, they fail due to stresses generated by them being pushed onto the speindle. Severaal of mine have failed without being used. Personally, I'd want to use a metal gear that was a sliding fit onto the motor sprindle, and then fix it on with a suitable Loctite. Somebody else suggested replacing all 3 gears in each train. Difficult. The last gear is part of the platten or cable drum, and is, in fact 2 gears wit han anti-backlash spring IIRC. All these parts could be made, but you're not going to find them off-the-shelf. And if you're going to start 'm,king swarf'[1], why not just make the pinion you need. [1] A common UK expresion for doing home machining, for the obvious reason. -tony

The spindle is about 1.5mm in diameter IIRC (I've not put the micrometer on it, so don't make something based on that). Making a hole-with-flat of that size could be 'interesting! Again, a very small screww (M1, or smaller, I would think). I haev never had this sort of Loctite fail. It's the sort of thing that's specified to lock certain bolts in modern cars, and they don't expect said bolts to undo themselves after a few years :-) In any case, shoulkd the gear come loose in one of these plotters, it's not going to cause death, injury, or even loss of income I would have thought :-). And I'd rather have to pull the cover and put another drop of Loctite on the spindle every 10 years (or whatever) than to have to keep on making plastic gears like the original. -tony

Steven Canning wrote: Can someone please repost that URL, I seem to have lost the message that contained it. Probably when I managed to clobber the mbox file that held my copy of this month's classiccmp messages... -- Phil. | Kitsune: Acorn RiscPC SA202 64M+6G ViewFinder philpem at dsl.pipex.com | Cheetah: Athlon64 3200+ A8VDeluxeV2 512M+100G http://www.philpem.me.uk/ | Tiger: Toshiba SatPro4600 Celeron700 256M+40G

I do love the comment on the title page which says something like 'for engineers, mad scientists.. and very few normal people' :-) In the UK, look at Camden Miniature Steam Services. They sell Lindsay books, along with other reprints of old books, etc. Much of their stock (As the company name implies) is aimed at the model engineering crowd -- people who make small steam locomotives, etc. But there's plenty there to interest eccentrics like me too. The only complaint I have ever heard about Camden's is that if you order a book from them they send you their current booklist (catalogue). And you are sure to find 10 more books you want. They will end up bankrupting you :-). Seriosuly, they're a great company to deal with, they send the right books almost all the time, and when they did once make a mistake and sent me the wrong book (same title, different author), they put it right very quickly and without fuss. I've never read that series, but I've read plenty of other books by Dave and VInce Gingery. They're excellent. Very clearly written, and you get the impression that they've done the stuff described in the book, and you can do it too. -tony