My first piece of astronomy lathework

[Ajohn]

There are a whole series of books that can help with various aspects of "engineering" at home that go by the name of the "Workshop Practice Series". The same people also publish several related books. One thing that these cover fairly well is anodising in the booklet on plating. They give a range of current densities to use and I find that that aspect is more critical than some web pages suggest. Best experiment on some clean scrap. I used lead flashing for the anode/cathode and should remember which one it is. I cleaned it up with wire wool and then etched it a little by leaving it in white vinegar for a while. Good quality fountain pen ink can be used as a dye.

I mostly use hss tooling on a lathe as I can get better results on most materials than carbide tips. This is basically because I polish them with a fine slip stone. Diamond lapping sticks can be used too. I started working for a company where everybody did several years of toolroom work before anything else and the slip stone came from that. Some one on ebay lists 5% cobalt hss tool bits and that is a decent grade to go for. Many people buy 6in grinders but these are too small to make a really good job of grinding tools especially with the wheels they come with. Axminster sell some white aluminium oxide wheels that work remarkably well on these machines. Water is still needed to cool the tool bit from time to time but the wheels cut hss nicely if a bit slowly. They also do a hammer headed wheel dresser which is very easy to use.

Some one on a Schaublin group suggested trying a particular type of carbide tip. They do work rather well. Personally I would avoid buying these off ebay as I feel sure that many are part worn. Better to buy from here. These are the type of raked finishing tips that were suggested.

http://www.shop-apt....um-uni-tip.html

They work well on aluminium,stainless,brass and steel. A cutting oil helps on stainless and the others sometimes too. Morris Lubricants will sell 5ltrs mail order. A near life time supply as all that is needed is a very light smear with a lightly wetted brush. I use £ shop kiddies paste brushes. The wooden handled ones last longer.

It's worth nosing about the site as they have offers. The same style of tips are shown in hobby tips as well. These will fit the ebay small shank tipped tool sets. Best buy those with Torx screws as the hex socket ones soon round over. This site also carries spare screws.

I often use imperial threads where I can as screw cutting metric ones often involves reversing the lathe which is a bit of a pain. If a lathe has a screw cutting indicator one easy way is to disengage the drive, turn the lathe off, reverse it and re engage the screw cutting on the same index mark. The same thing can be done when the tool has traversed back to the start if needed.

If buying a typical heavier duty model engineering lathe the Myford name usually crops up. Super 7's in particular. Bearings are usually worn on ML7's. These can be good and are heavily featured in just about every model engineering book. In practice however they have their problems usually associated with wear particularly in the bed and having owned several lathes I feel Boxfords are a much better bet. Usually cheaper too but one with a T slotted cross slide can be hard to find or that will have to be bought separately if needed. The Myford Speed 10 and ML10's can often be found little used and with lots of bits and pieces. The bits and pieces that come with any lathe are important. If bought later costs tend to rocket. One interesting thing about these myford xxxxxxx 10's is that they often come with imperial screw cutting gears. Buy a couple more and they can cut metric too. They also did metric lathes as well. For a variety of reasons I'm not too keen on metric machines so stick to imperial. The reasons mostly relate to divisions of an inch against what can easily be done on metric machines.

John

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[Cath]

Sometimes (often, even I wouldn't mind a complete change of career, particularly one that didn't leave me sitting at a desk for most of the day, but right now I'm working on a project for a client who is insisting that I charge them more than I already do and I think I should probably be being grateful for what I have rather than looking over the fence and deciding that perhaps it's more verdant on the other side

Well, we are very lucky here in the 'developed' parts of the world, but ..

If there is something you'd like to do in life James, then I'd say go for it while you can. Because all too often something can along in life that makes that thing you'd like to do quite impossible from that moment onwards.

.. assuming of cause it doesn't mean loosing what you already have.

I suspect the time we appear to have here on planet Earth (with all it's luvly colours etc) is going to be a rare event for each of us, not that we'd notice any possible inbetween bits

[DaveS]

One big regret is never buying a lathe and getting dad to teach me how to use it.

What he didn't know about machine-shop work wasn't worth knowing.

20 years he's been gone. I still miss him dreadfully.

[Ajohn]

It isn't difficult Dave. Many people who know absolutely nothing about machine tools buy one and teach themselves with the aid of books and various web forums. If you search "workshop practice series" on ebay you will find very reasonably priced books on most aspects of things that might interest a model engineer. The usual problem people have with lathes is cutting speeds. They read that this and that material has to be cut at so many ft/sec surface speed or whatever the metric equivalent is most of my books are old. What books don't point out is that these are largely related to doing a job as quickly as possible with an acceptable rate of tool wear. They also indicate that some materials needs to be cut more slowly than others eg marine grade stainless steel, cut that too fast and it work hardens. In practice many lathes produce a better finish at much lower speeds. Low speeds are not a problem providing a lathe has a sensible power feed. Aluminium can be a problem too. People might find themselves using high speeds and the aluminium cuttings melting and sticking to the tool. This isn't obvious when it's happening but leaves tell tale smears of aluminium stuck to the tip of the tool and produces a very poor finish.

Books mention a huge range of tool cutter angles. That style of carbide tip I linked too will cut all of the usual materials well. The ones that come with ebay sets are ok too. The main thing about cutters on a lathe really is setting them correctly. An external tool needs to be set as close as you can get it to the centre height of the lathe but not over it. Things are the other way round when boring holes and boring bars bend so the tool usually has to be set at a height to account for that as well.

The other problem is what lathe to buy. 2 things to check on Chinese lathes. One is usually a fact of life. Spec's give the swing over the bed but often the maximum feed across the lathe isn't sufficient to turn over that size of item. Usually they will turn over the other swing that is mentioned over the saddle. Some wont turn up to a centre in the tail stock. That can be fixed by using a thing called a morse taper extension but it annoys me as it happens because the spec of the lathe looks better if it can't. People buy lathes on the basis of centre height and distance between centres so there have been instances where importers tell them to increase it even if it causes this problem. The people who sell them usually do know about any problems like this so asking about them may help. For screw cutting a lathe with a screw cutting indicator is best but people manage to cut with the screw cutting drive permanently engaged it's just a lot more difficult to work up to a shoulder as the lathe may take some time to stop when turned off. People have been known to fashion a handle to turn the lathe spindle by hand to get round that.

Various books are often useful to people like me who had a very thorough toolroom training. In a toolroom the perfect machine for the job is usually available. At home people have to cope with what they happen to have.

John

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[laser_jock99]

One big regret is never buying a lathe and getting dad to teach me how to use it.

My regret is selling my Myford Super 7 in my younger/poorer days. I sold it a friend and he made a great job of restoring it to like new condition. I also had a tiny Unimat 2B watch makers lathe which was great for precision jobs.

[fwm891]

Really great stuff James. I've had my lathe a few years now and wouldn't be without it. What I like is making my own tools and accessories for the lathe.

Enjoy. Just take it slowly to start with, it doesn't take long to move to quite complex turning/milling on the lathe.

[DaveS]

I may have a look to see what I can find S/H. I remember being quite taken with the little Unimat lathes but wanted something bigger. Unfortunately "something bigger" usually by Myford cost too much and would be too heavy to lug up stairs to our then flat.

Now I own the whole house and could accomodate it on teh ground floor I may see what I can do.

[JamesF]

I may have a look to see what I can find S/H. I remember being quite taken with the little Unimat lathes but wanted something bigger. Unfortunately "something bigger" usually by Myford cost too much and would be too heavy to lug up stairs to our then flat.

What I have is one of these:

http://www.chesterma...uper-3966-p.asp

which I believe is bigger than the Unimat though small and quiet enough for people to have actually in the house. It's also light enough (about 40kg) that I can pick the entire thing up in one go which was certainly not the case with my dad's Boxford . Unless I was only interested in making very small components I don't think I'd want anything smaller just because the working space would feel very cramped. Even with this one I often remove the tailstock completely when I'm not using it just to give myself more room and I bought the 4-jaw chuck because it would take a much more useful size workpiece. The "next lathe up in size" seems to be a fair jump, as if you're going from "recreational hobby" to "serious hobby".

The one I have actually seems to be a fairly generic Chinese-made unit sold with their own branding by Chester, Amadeal, Arc Eurotrade, Sieg, Warco and quite possibly others I've forgotten. They have a few little niggles that can be relatively easily corrected and I think Arc even sell a version that they tweak for you before shipping it. Second hand they seem to go for not excessive money.

I get the impression that Myfords and Boxfords are more robust and perhaps a little more flexible, but they seem to come with a price tag that reflects that.

James

[DaveS]

Thanks James, that looks a very do-able lathe.

Perhaps not in Myford / Boxford league, but for my modest needs....

[JamesF]

Perhaps not in Myford / Boxford league, but for my modest needs....

That's exactly my feeling. My dad has sold his Boxford and swapped it for something more suited to what he wants to do these days and whilst I'd love to have had it particularly given that it's had gentle and limited use for the last forty years of its life (and I probably could have had it, too) it's twice the size and three times the weight. I'm not sure the times when it would be useful to have the bigger machine outweigh the advantages of having space for another piece of kit in the workshop.

Ok, so I admit it would have been nice to own a bit of engineering history, too. No-one is ever going to go into a workshop and say "Wow! That's a lovely example of a cheap Chinese generic lathe!"

James

[DaveS]

If you really want to see nostalgic "They don't make them like that anymore" then take yourself off to Threlkeld quarry / mining museum. More assorted cranes / excavators than you could shake a shovel at, and the engine sheds, with old belt-driven lathes are a photographer's paradise. There's a fabulous view of Blencathra thrown in for free, too.

[DaveS]

Thinking......

I've still got dad's 1942 edition of Machinery's Handbook that mum bought him as a (I think) birthday pressie.

Chock full of useful (And historic) info. Most is probably obsolete now, but some is probably still relevant.

[JamesF]

A fair bit of my learning has been from books such as Sparey's "The Amateur's Lathe". I think that was published in 1948.

James

[Ajohn]

The way to handle a Boxford is in pieces. Mine is an ME10 and that has a rear drive rather than the underdrive on the other models. The head is held on by 2 bolts on all of their models. Taking that off and the tailstock makes it a lot more manageable for 2 people. The saddle can also be taken off. The stands on most lathes if they have one are always heavy.

Personally I wouldn't buy a Myford 7 unless I saw it working and it produced a nice smooth parallel finish. It was a good option when the bed and saddle could be sent back to Myford for a regrind and saddle fit if it was needed. 2 people can manage a Myford 7 off it's stand but it's easier with the tailstock and saddle removed. The headstock is best left on. The Myford ML10 and Speed 10 are better options in a number of ways. For their size they have an adequate distance between centres so there are unlikely to be problems drilling holes. I owned a Hobbymat for a while - good job it came with a lot of stub drills. I also repaired the screw cutting drive on it several times. The main gain of the Speed 10 over the ML10 is a higher maximum spindle speed. That makes it easier to hand feed when turning very small parts but really for that sort of work 4 ot 5,000rpm would be a lot better. If power feed is used that aspect doesn't really matter. On my Boxford for instance it's usually running at 500 rpm and I make M2 screws by sizing them in one cut.

It's a case of buyer beware buying used lathes. Even Boxfords can be worn out. The main gain is a back gear. The Chinese lathes minimum speed is usually 100 rpm and that can be far too fast for screw cutting at times. Back gears can reduce the minimum speed a lot. For instance the min speed of my Boxford is 38 rpm. That is still fast for very coarse threads really but these seldom need cutting - in my case anyway. Boxford's pluses over a Myford are a better over all design - especially the bed and a proper power feed system. It can be a problem obtaining the gears for a slow feed speed on a Myford. The Boxford doesn't use the lead screw pitch for power feed so an imperial one for instance will feed at 0.0015 per rev as it comes if it has a screw cutting gearbox which they usually have. They also tend to wear better than Myfords. The ML10 and Speed 10's often haven't been used much.

Old books - nothing has really changed in respect to manual machine tools from way way back other than there being more options available re carbide tooling. More recent copies of the Machinery's Handbook even give details of metric threads. Many other types too. All the other data in them is still valid as well. These days CNC is usually used.

I started with a Peatol ( Taig in the USA). They can do very precise work until the heads bend. Unimat next for something bigger. Then a Myford ML7. Then finally the Boxford ME 10. There way also a Raglan before the ML7 but as that was exceedingly heavy it had to go in the garage and rust was a problem. I also fitted the ML7 with a Super 7 head. All over a period of over 20 years but I must have had the Boxford for over 10 now. It would probably have been better to get it right 1st time. The initial reasons were bits for small telescopes and odd bits and bobs. More recently bits for microscope and other bits and bobs. I need to modify modern tap heads shortly so that we can retain our now rather old taps on the kitchen sink - or replace the entire sink and unit it's on. The sort of work a lathe can do? Lots of components so that it could be made. Some think I polished it all or used emery cloth..

John

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[glowjet]

Nice bit of turning work James, you will find a lathe most useful for those odd bits in Astronomy, apart from alloy and brass, you can turn some useful bits out of Acetal bar, available in all sorts of diameters