Member postings for Ajohnw

There is a rage on tooth belt drives Michael Even a claim that they even out tooth error and don't stretch etc and can be used up to 10,000 rpm so must be wonderful. Really the base problem is the number and size of gears that are used up to the final axis drive. They tend to be rather small early on so rotate at pretty high rates in terms of astro photography exposure times so the slightest wobble causes drift. People with good technique and autoguiding still produce amazing results with them. Some spend more and more on mounts. Some stick with exposures that are as long as possible. People also get good results without even doing that particularly with dslr's.

The old rule on ideal worms wheels was diameter >= the diameter of the scope being used.

Neil, many have made them with a fair degree of accuracy, allowing them to rotate freely as they are cut seems to be the key and that goes back to pre wwii. At some point I will try a trapezoidal tap with a good tapered lead in which should get round initial engagement problems. Old advice using home made hobs was to wind in quickly. A metric tap as they are cheaper from china than acme usually is.

I own a mount by Meade that Astrophysics used to work on and rebadge - they did 2 main things. Lapped the worm and changed the goto software. Also mounted it on a hefty pier. Considering what is around now I decided to stay with it for if I need a mount this substantial. People are locked into tripods too. Any one who has owned a Vixen GP pier would realise that they are light portable and very stable. In fact I reckon they are quicker to set up too. Trying to get the top of a tripod dead level is a real pain.

John

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This cropped up some where recently, Might not have been on here however a pretty good video on the process

Where ever it cropped up some one hack sawed the slots needed in the wheel before cutting it by eye.

They can be lapped and polished afterwards with another worm. Astro people don't seem to appreciate the advantages of huge worm wheels with lots of teeth. Dividing heads etc do. If perfect they reduce the error in what ever is rotating them by their ratio. When they have an error things aren't that simple but given the way they are produced they tend to be pretty accurate anyway.

John

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If I am feeling manic as I can usually manage with reading glasses I use a pair of this sort of thing of Russian origin

**LINK**

I'm not sure I would recommend the pair I use as they zoom and focus independently and that is tricky to set up. The working distance is very good though. The link will probably bring up a lot of chinese optics. From my experience they can be surprisingly good. The big advantage they offer is true stereoscopic vision. I have used headband types mostly the ones that RS Components sell which are basically industrial parts but I think they are not as good as these. I'd be inclined to risk buying a cheaper pair of binoc's. Maybe some have dioptre matching for people who have unbalanced eyes. It's important to relax the eye when using these and not to inadvertently try and focus at the working distance - usually more of a problem for the young.

I also find a desk magnifier very useful. I found some of these very seriously discounted

**LINK**

They are little odd hence the discount I suspect. There might still be some about on the web. They have an on off switch and a PRESS to START button. No idea why as the tube does start as soon as it's switched on. It may help when the tube has aged but I've used 3 tubes over 5+ years probably 10+. If I was buying again I would try to get one with a flip up dust cover but I've had no problems from regular cleaning.

For really find work one of these comes out

**LINK**

They crop up now and again and have very crisp optics and a decent working distance even for things like soldering, even working on watches at times. I'm sure if needed a model engineer could mount one on a boom stand. I also have a couple of very capable stereo microscopes but these tend to be a lot more expensive.

John

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That's a long way from Bristol H

The way I have found them around me is via google but it can be very frustrating. Such searches as none ferrous stockholder or supplier might bring something up, same with steel and cast iron. Also yellow pages. The none ferrous supplier I use didn't have a web page some years ago. Some of the smaller ones still wont have them. Many will cut to size and have a trade counter.

Off cuts though - of late wish you luck. They tend to keep them until some one asks for the size they are. I did know one with an off cuts room, pick, weight it and pay 5% over scrap. They were taken over and the lot thrown away. As the man behind the counter had taken great glee in telling a number of model engineers that I have never gone there again. William Gab used to supply a lot of model engineers and I am sure that their business was worth while.

John

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I think Chrome can opt out of Google Anal ............... Ketan. Others too.

**LINK**

I suspect this is an interesting aspect of concerns in some quarters about what the EU may eventually do about this area in general - if they dare. It wouldn't surprise me if they did do something about companies storing persistent data on peoples machines but then they have been doing that in a round about way for a long time - certain services store the data instead. Who ever came up with the nice name of Cookies was clearly a comedian - well by now most people know he is.

John

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If you do go for a linked belt I would avoid buying the cheap black one. (RDG I think) In use it's a bit like trying to use toffee.

The T and nut types that use metal link joiners are fine but not the easiest thing to join up. Fenner make one that doesn't use metal joiners but have chosen to only sell it in rather long expensive lengths. Maybe that one is ok.

Not sure what section your belt is but if you look here for instance at A section the steps in size get smaller as the belt length goes up. This is the way I would probably go, Cheaper and efficient - even if you have to buy 2.

**LINK**

John

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Edited By Ajohnw on 21/01/2016 09:39:05

Must admit I never power feed when I am parting off or facing - I'm usually using a boxford with a gearbox so setting the rate is easy and quick.

It's a bit strange that they haven't allowed for belt tensioning. Maybe there is some scope in the motor mounting. They shouldn't need to be that tight with sensible pulley sizes as they tend to pull in and grip on the side that is transmitting the power.

John

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Jason's spread is just about ideal for the majority of work really. I'd guess they have gone that low to ease screw cutting to a lower speed than many may need unless they want to cut an extremely coarse thread.

They have done this on a Wabeco 2000 too. I wouldn't be surprised if at some point I changed it. I'd probably go for a top speed of about 800 rpm if I did that.

John

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Well I did say that it had been a long time since I bought an ME. CNC, I vaguely remember a brief article where some one had added cnc to a dore westbury.

Frankly if it has gone entirely like that it just can't be good for model engineering. At times I have gained the impression that people come along wanting to get into model engineering and start off looking for a large lathe which might well be a clapped out colchester etc and bridgeport milling machine - which might also turn out to be clapped out. Some people haven't got the space or the money and it's a fact that lots can be done on a lathe along with some other bits and pieces.

One good thing though is gear of that sort is definitely still in use even if the mags don't cover it any more. A lot can be done with 3 jaw, 4 jaw, face plate, steadies and maybe a few collets. A vertical slide adds even more. A milling machine may add more capacity but lathe set ups can be surprisingly rigid. Add a tool post spindle, easy to make, not so easy to power, and maybe a slotting attachment and even more can be done. The only problem really is the prices of some items even used especially for myfords - £999 for an ML7 dividing attachment for instance - some one having wet dreams I suspect but there are other ways and mags have covered them. Or did at times once. A lot of this is all about set ups.

John

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The steady is good for parting off drain pipe. I had to angle the peatol so that the rest of it could go out the back door. I got lovely smooth square ends on lengths up to 10ft.

John

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If I remember correctly Jason mentioned 400 rpm and I assume in the low speed range. Have you tried that?

Angle the tool and take a facing cut with it so that you can check what the centre height is. Say around 30 degrees. Also looking out for the work lifting - loose headstock bearings but that would be more noticeable if the tool was nearly square on but it will bend. The pip usually breaks off if this is happening when facing if it's extreme. Don't have much tool sticking out so that you can vary the feed rate with less risk of breaking it. It might be a good idea to sharpen it first.

John

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If some one can push their cross slide moderately easily by the amount mentioned I'd be inclined to adjust it. It's nice to have sufficient resistance to ensure the nut is more or less fully home when the cut starts. It's best adjusted with the lead screw out to that some resistance to movement that's even across the whole travel can be detected by hand. Often impossible on used lathes that have done even normal rates of work for some years.

It's important that the nut is fully home when parting off - usually done by the feed rate. Jason posted a shot that shows a significant thickness of swarf coming off. Pussy foot about and parting off generally wont work out. To fast a feed and the blade may break. If there is too much play in various parts of the lathe parting off can make a lot of noise. Usually a short sharp increase in feed gets rid of it, sometimes it wont go away so just grin and bear it. Even a well set up lathe may do this if the feed rate is too low.

It's not a good idea to have a parting off tool above centre and not too far below either. They need setting up with more care and square to the axis of the lathe. I usually do that against the chuck but something a bit more extreme might be beneficial on lathes that face a lot of dish.

Personally I think that the top of HSS blades are best left flat as they come. The front clearance angle is about right too. This is inclined to increase cutting pressures and help keep the lead screw hard back on the nut - an even feed wont grab then. The HSS used on these is sometimes a load of crap so best not temper it when sharpening it. They do need to be sharp. I wanted some recently and had to buy from the USA to get the size I wanted and a reasonable amount of cobalt in them.

A modern lathe bed shouldn't need a rear parting off tool but they are convenient as they can be left in place on lathes that have sufficient cross slide travel. Myford 7's often benefit from them because the cutting forces tend to lift the back end of the saddle and press thing home reducing play.

A variable speed lathe is likely to have to be run at a speed where it still has a reasonable amount of torque available. Most have a lower speed belt setting which should help but people might find that they need to run at a pretty fast speed. That might make a disposable tip parting off blade attractive. These are usually 1" deep and come in various widths. RDG do a holder which should fit many lathes providing they have a Myford sized tool post. On some lathes the side of that may need to be very close to the end of the compound slide in order to get the tip low enough.

John

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I haven't taken either magazine for a long time now but I suspect that ME will still give more details on actually making things. That makes the articles rather long. MEW was generally more short and quick with varying amount of detail.

I was trained as a toolmaker. That's ok and useful but working at home is a little different. The toolrooms I have been in have every conceivable piece of equipment. There is no need to make do with what's about.

Where I would be inclined to point people is towards certain books. The workshop practice series for instance. Some are a bit indifferent but many for the cost are pretty good. A good book on "making do" that covers a number of things is one of the Projects for a Unimat books. It includes plans for a small traction engine.

ME as I see it is largely concerned with making everything on a Myford lathe along with a vertical slide and one or two other bits and pieces. Maybe milling machines are expected now. No idea as it's a very long time since I bought one. If everything is going to be made on a lathe the difficult aspect is just how to set the work up. There are plenty of ideas concerning that aspect in ME articles especially for making tooling. Some have been reprinted into books. From what I have seen these can be a bit mixed.

I haven't much interest in chuff chuffs on rails either so can appreciate the OP's feelings. Actually I did know some one that made some of the difficult bits for people making these. He made jigs and took no notice of what was in the articles as he knew it would cause problems. He was a toolmaker. Covering making a loco in fine detail would take rather a lot of editions.

People like Neil have a tough life when asked to keep everybody happy. At one level people just want plans and at another lots and lots of detail.

Google can be useful eg making model ic engines bought up this page

**LINK**

Youtube can be too but there are some people about that have some strange ideas. It pays to take info from a number of sources and spend some time thinking about it. I suspect a lot of the problems people have comes down to confidence really and wanting to be told exactly what to do. There are lots of ways of cracking an egg. Some are better than others.

John

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I find them ok for all sorts of things especially if they are tightened onto any nut I want to use them on. Easy to do one handed on the smaller sized spanners.

The bung might have come out if a decent pair of stilsons had been used on it - the right way round so that they self tighten. These sometimes need tightening on the nut as well. The hex nuts on bungs are sometimes too short to do that safely or the spanner made too poorly. I had to drill and add a couple of dowels on a Shogun once and undo with them on those - with a 3ft tube on the end. It must have been done up by a Sumo wrestler hanging on the end.

John

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Actually Neil it looks like things can go wrong. I wanted a best form plano convex lens. The flat side is slightly curved. It's come and it's only coated on one side !

Not sure if that is a one off or normal for this lens. It probably doesn't matter for what I want it for and I have to bear in mind it costed £2.58. Knightoptical would charge me 10 times that plus vat and probably a ridiculous postage price. Cheapest on ebay around £21.

John

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Useful that Jason.

John

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Just a note for any one who buys lenses from Astromedia. The lenses are coated as they state but that isn't immediately apparent. They are broad band and don't really have any colour at all. Some colour can be seen by looking at the reflection of a fluorescent strip light at various angles. This happens because the thickness of the coatings is what gives them the anti reflection property so at some angles it appears thicker as far as light is concerned and the surface will reflect.

Some one bought one and thought it wasn't coated. Actually I think it's a fairly high quality coating.

The other way to tell is to compare the reflection off them with a plain piece of polished glass.

John

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Sometimes when the mic's are adjusted to align the scales with a hook spanner the sleeve slides back a bit. It might be possible to work it back down again.

Really though a photo would help to show exactly what you mean when you refer to the nuts. The only nuts I am aware of on mic's are used to set the fit of the spindle in the actual micrometer thread.

I'd be interested in a link to this Chinese manufacturer.

John

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There may be enough photo's for Jason to carve out one from scratch.

John

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I raised it because unless things have changed they don't attract any VAT at all. Also because I had a feeling that even if there were any charges HMRC's doc's in all probability don't mention what they actually are. I found out that they were zero rated at the time from some one in the USA who asked a USPS agent. The tax free aspect seemed to apply to all major countries in the west.

It's an area that might interest people who collect old microscopes.

Really from my experience if some one wants to know specific details about import taxes it's probably best to phone up and ask them. There may even be different rules for gifts and commercial samples.

John

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