Member postings for Ajohnw

The problem with annealing and buckling is failing to apply and even heat all over - hence suggesting a domestic oven but pass if it will achieve anything. However some control can be exorcised by heating slowly and moving the flame around all over the sheet - just like when aluminium is annealed with a torch.

Brass can only be hardened via cold working as far as I am aware and softened via heat.

John

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You took that seriously ?

As to the rest we are all victims of what is called the precautionary principle these days. The problem is that people apply it themselves and that in some areas it's applied by people that can't look at it logically and just think about what might go wrong and ignore any positives. In the extreme it might result in some people preferring not to even go out of the house or take extensive precautions if they do. There has even been signs of it on here - angle grinders. They can cause harm. They don't if used sensibly - that's the catch with many things. Lathes and milling machines are disappearing from schools because they have exposed rotating parts. Rather curious guards are fitted at times but the machines still go and get replaced by totally enclosed cnc machines. This happens because some one is worrying about what happens if some one stupidly grabs hold of a rotating part or runs the machine so fast that red hot swarf is flying off the machine so safety glasses are no longer adequate. And so it goes on and on.

There is a related side issue as well. One famous example is people at work being sent on a training course to teach them how to use a step ladder. Why - because a company may have to demonstrate that they have done everything they can to prevent people from falling off them. The lack of common sense by users isn't considered at all.

John

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Edited By John W1 on 02/09/2015 09:59:18

These days people drink a lot of coke - that makes an excellent job of cleaning pennies. Probably useful after brazing copper too. Why not use coke instead and drink it afterwards. No point in wasting citric acid.

John

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I'd agree about handles. I had a needle file go most of the way thought the palm of my hand. Not because of it's cutting pressure but because it caught on something.. Another bad idea - it was sharpened so that it could be used as a scriber - really helped it on it's way. I was lucky that nothing was damaged. I had a rather strange dull ache for weeks.

I generally use good quality warding files with handles and a couple of larger ones 10in 2nd cut. Vallorbe from Axminster but they call the warding files miniature and come in a set. They are a bit pricey but having removed serious amounts of metal with stubs files of old they seem to be the only ones that measure up.

John

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It's possible to make a decent job of folding metal with maybe in your case a small engineers vice and 2 pieces of thick bright drawn angle iron and something long to fold it with. If brass is too hard it will split so I'd guess you may have half hard.

According to my law fully annealing brass involves heating to red heat and quenching in water. That's all I have ever done with it. For that I will stick to that too. Some reckon that the heat it's raised to determines the degree of softening. This might be true. It might be worth trying an extended period in a domestic oven running flat out. From a uni educational paper.

John

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The bottles were all translucent Michael. The first to look odd was the sulphuric. The nitric is now pretty opaque. Hydrochloric (80% ??) is still as it was but that probably came from a chemical supplier initially as it was to order. The others from an industrial supplier out of a tank.

There is also a small quantity of saturated oxalic acid solution in there but I don't think it would cause any of these problems at all. That's in a lab bottle anyway. That particular one will attack stainless to a certain extent. Also remove rust.

If I noticed that mercury had disappeared while in my pocket I would probably be a worried man. It's nasty stuff.

My father did the explode on touch stuff from iodine at school. I spent hours once trying to do that at home in early school days but did manage to make some nice fireworks, flour and coal dust explode but gunpowder just wouldn't work. Certain fertalizers too that didn't work. I'd guess no one does any of this sort of thing these days either.

John

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I thought so and checked. Water in nitric acid raises the boiling point. I also think but haven't checked that both it and sulphuric acid are hygroscopic in concentrated form so absorb water from the air so 100% is nearly impossible to obtain. I vaguely remember seeing mention that 100% sulphuric is actually oily so concentrated doesn't usually mean what it suggests. Some nut cases process diatoms by boiling them in both to get round that. It wasn't a too bad a practice when people had coal fires as the fumes went up the chimney. Not sure what happens now.

John

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No. I think aqua regia is nitric and hydrochloric. I have noticed while using it that hydrochloric acid fumes and steel aren't a good mix.

It's pretty clear to me that the acid themselves are attacking the plastic without any help from the others. Sulphuric much quicker than nitric.

I'm currently waiting for another demijohn to dry for the nitric acid as tipping any concentrated acid into it wet wouldn't be a good idea at all.

John

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I thought that Nitrocellulose lacquers were used from around 1920 or so. It did get rather thin on the ground but does seem to be around again. I believe heat is sometime used with it but I think it's more associated with drying. The problem was probably that it's one step away from explosives.

I have seen mention of shellac based with a mix of things like turmeric being used. Eg this one

**LINK**

There are also epoxy type things around that are mostly used on musical instruments

**LINK**

I have a slight interest in restoring a brass microscope. Looking around nitrocellulose seems to be used most often but if pre circa 1920 that probably isn't authentic.

John

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Your comments sound entirely sane to me Andrew - stick with it.

John

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Still tidying up and sorting things out I went into my acids cupboard. Model engineers and pickling metals used to be pretty common. Dealing with them one at a time

I noticed some time ago that sulphuric seemed to be slowly eating into the plastic container that it was supplied in. I transferred it to a wine makers style demijohn and fitted a lab type rubber stopper some time ago. All ok.

When I did that the nitric was ok. Now it looks like something is happening to the plastic containers again. It has taken a long time, years.I think it's time to transfer that to a demijohn.

Hydrochloric which wont be concentrated but will be high strength no problem at all. Probably 80%. For what I need that for cement cleaner would probably do really.

I noticed an odd smell around the cupboard last week hence looking further. There were some metal parts in the same cupboard, all corroded suggesting fumes do escape even from screwed tight plastic containers.

My main reason for having these substances is diatoms and microscopes and I have received extensive training in the past about using them. Processing diatoms also involves mixing highly oxidising chemicals as well which really does need some care so please don't be concerned.

I am rather surprised about what has happened to the plastic though and some model engineers probably do still use strong acids and are also probably fully aware of what to do and not do with them. Odd thing is that some lab reagent bottles are plastic lined - I now wonder what happens to them. The one I have with sulphuric in it still seem ok. Why not make the containers from the same material. Cost I suppose plus most people who buy it probably use it quickly and or pour it into a vat of some sort.

John

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Levers - probably have to make yourself.

Swarf does get on the screw cutting lead screw - depends on the lathe.

Having it get on the compound slide screw can be very bad news it if it gets into the nut. It may cause it to start to jam - move it in the opposite direction if that happens.

Seriously I would also add a screw cutting indicator to the list. In practice they aren't cut that often but ......... An imperial one can also help cut metric threads on an imperial lathe. Still have to stop and reverse but the indicator can be used to allow screw cutting to be disengaged when working up to a shoulder. It goes - disengage, stop lathe, reverse lathe, re engage using the indicator when it's in the same position as it was when disengaged. This work out providing that the indicator doesn't revolve too much during the just disengaged period. It's easy to do in practice but sounds a pain / impossible.

Another thing that it might be worth asking a supplier about is if it's possible to turn work right up to the end of work when it has a centre in it. Not being able to is an easy way of making the centre distance 2" or more than it actually is. Going on a visit to one well known supplier they will know about this and may smile or even laugh. In this case it ruled out several machines they had especially certain ones that looked pretty good in all other respects. These were earlier designs that had been "improved". Much cheaper than making the bed longer.

I'm looking for a small fully metric lathe. Just about everything I look at is lacking in some respect. This might include statements on the web like this is for illustrative purposes, actual machines may vary plus all sorts of things I read and notice about them. My ideal really all considered would be 18" or near centres, even 15, Centre height allowing 2in dia plus space over the cross slide and hopefully T slots even if these are only just at the edge. Plus a cross slide travel that allowed the full swing to be turned with a bit spare. I'd probably find that if the T slots were used the cross slide would lock up so really they are better on the top even if only Myford size. To much tightening will break those but better than the cross slide locking up because the casting has distorted. I should also mention sensible sized chucks for the lathe not ones that are rather small for what the lathe can swing.

Forgot the quick change tool post - a decent one with the lathe - as far as I know highly unlikely.

John

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Edited By John W1 on 01/09/2015 15:30:25

That is a very good point for beginners Brian. There actually is some sense in buying just to find out. Costs of doing that are actually fairly low because it will sell on the 2nd hand market. I'd guess with this one that you already have mixed feeling about swarf getting on an open lead screw on the compound slide. Your comment on brass and aluminium doesn't surprise me at all. The last person I know that went out and bought one even against advice turned round one day and said it's only any good on plastic to me, not really sure what it's any good for. He bought one because of the low weight. He also had worries about the strength of his shed floor - silly really if as bad as he the implied he wouldn't be able to stand up in it.

The wattage they quote does seem to have it's catches. I've long suspected that input power is quoted, expect up under 1/2 of that coming out in that case. The other aspect is electronic speed control. It really is difficult to get a grip on what that means in terms of torque on the cutting edge of the tool. It might even be extremely low at low speed settings. Speed reduction via belts and gears increases torque - even good electronic speed control doesn't because motors can only take so much current so as the revs go down so does the horse power. Some of the variable speed lathes do have a belt to give 2 speed ranges. The belt ensures that there is more torque in the low speed range. Frankly I feel they should have 3 belt settings not 2. I'd guess some people modify them. Some of these lathes use a gear to provide the lower speed range. Initially metal gearing which can be rather noisy. More recently plastic with metal replacements available if they break. I've no idea if they do.

I suspect as many people are happy with mini lathes you would have been pleased with the next model up - the mini lathe rather than the baby one. This and other reasons is why I sometimes say don't buy a lathe unless it weighs circa 60kg or more - unless you want to do pen turning for instance. Even then swarf will get in that lead screw. The slide that is on wont locate very well either as it's so short.

There are catches with the mini lathe as well. Power seems to vary. Some now come with brushless motors which might be better over a wider speed range. Probably for the same reason that a 6 cylinder engine produces more low speed torque than a 4 and an 8 even more. I've not seen what they have done so can't be certain on that aspect. They will still have a maximum current rating.

Metric versions of the mini lathe sometimes come with screw cutting indicators that allow metric threads to be cut without reversing and stopping the lathe etc - some don't. If you ever get to screw cutting you most definitely will appreciate an indicator even if it can't be used on all of the pitches the lathe can produce. Imperial lathes come with and without as well. This aspect seems to apply to all metric lathes. When provided they usually have several gears which can be meshed with the lead screw and drive the indicator dial.

As to what needs doing to them after they are bought ArcEuro provide a guide. This is why some people call them casting kits and even rework the saddle fit on the bed at times. The arceuro guide is very likely to apply to all of them even Opti - have you looked to see how well the underside of the slide has been machined? Or the fit on the cross wise adjustment of the tailstock if it has that. This is how the costs are kept low - or margins high - not sure.

Well I should add that a lot of people do decent work with mini lathes despite all of this. It seems to be the smallest size where this can be done. I have no idea how often the correct things with files and emery cloth etc.

By the way. Did you check that you haven't pressed the emergency stop button in by accident. Easily done and they latch and need rotating a little to release. On the other hand the variable speed drive electronics do fail sometimes. Often on early a machines so they started fitting an American design which might be better.

The best source of reviews on the web really are blogs and youtube all by ordinary people who are actually using them. Some however will be supported by the suppliers.

John

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Some might suggest buying a used machine. Not an easy thing for a beginner to do as they might buy a load or rubbish. There is plenty about and they can be used but a new machine is likely to offer better general performance even if it has some catches.

John

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It's been through the listings more than once. Rumour has it that they aren't really rigid enough for serious work so are something of curiosity but can be finished rather well.

The ship type things with a lathe and a miller in one unit are a somewhat different kettle of fish. They have appeared on ebay from time to time but weight wise are rather hefty. Those did do real work.

John

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Production rates do rule but having heard huge machining centres being set up the job sometimes limits that and speeds a feed rule again. They can only go so far and need balancing according to the work and the machine.

The red hot aspect is interesting. Hadn't thought of that but would wonder about some alloy steels. I once asked some one at work about what steel supplier they used, just to try another. He phoned up and asked them to supply a certain alloy steel as a joke. I'd guess it was some sort of relatively low temperature low distortion hardening material so you can guess what happened when I treated it like mild steel. It's one of those materials where HP really matters and I hadn't got enough. It also made short work of HSS due to that and brazed tip carbide wasn't keen on it either after it had hardened. I'd wonder if that sort of stuff could be got red hot quickly enough. I have machined nitriding steels at work with HSS without any problem at all. Even moderately hardened plug gauges.

When he asked me how I got on just said fine and he looked surprised and walked away. I think the piece is still in the garage. At times it might be useful to know what it was.

Another link that shows what Pb free cutting and others do machining wise.

**LINK**

John

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There are lots of them about in all countries. Some local in engineering areas some far away but in terms of what people get there is a need to be realistic price wise within reason. Some only sell the dearer machines and nothing else at all. They often also sell a range of cnc machines which can make them easy to find via google. Those are pricey though - really pricey.

John

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The best thing to ask for if finish is really important on mild steel is leaded free cutting. Ideally black bar as bright drawn will have a skin on it that wont machine as well. The only catch with it is that it can't be case hardened. I assume it's still available. It will vary according to where it comes from and the state of the moon etc. All steels do so both good and bad can turn up. I think standardisation hasn't helped that aspect. I worked for a large company and they produced a booklet on metals listed for specific purposes and brand named rather than ISO numbers etc. It worked well because quality of what came in was more controlled.

I suspect the speed aspect often mentioned in relationship to carbide tips really relates to feeds and speeds and cutting pressure removing play and sources of vibration.

One thing that is bugging me at the moment is why my grinder in the garage produces better tools than a cheapo one I have bought for use in the house. The grade of wheel in the garage is obviously not ideal for HSS. The one in the house appears to be better. It cuts a lot cooler so more can be done in one go. More slowly as well. I reckon it has something to do with wheel wobble. Brief periods when the wheel cuts more and also generates more heat that I don't notice. Great fun because not much can be dressed of a wheel at a time otherwise the diamond is likely to fly out. The wobble also makes it more difficult to feel the angle being ground accurately back onto the wheel.

John

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Speed change appears to be via a hinged end cover on the lathe I linked to. For belt changes not as nice as a rear countershaft arrangement and probably a bit more fiddly but manageable. What I have done with my lathe is fit a 6 pole motor and inverter. That in itself gives me fairly safe 4 to 6 pole speed range where full motor power is available and zero risk of the motor overheating or bursting and those figures can be pushed a bit further if needed.

A year or so ago I was tempted to buy some metric coventry die chaser inserts complete with a holder for hand chasers. Not many pitches so I asked about other more and was told that there weren't any and that these were the ISO standards. I'd guess they probably relate to threads that should be used for none standard parts. These might be what the gearbox offers. In any case the odd gear change isn't really a problem.

There are chinese lathes about where screw cutting is all via switches but you wont buy a new one for 2K or anything like it. People who sell items like that usually expect people to visit so details can be scant. This one may have that type of screw cutting gearbox. From last time I visited some of the other larger ones they do will have. Some years ago and on a cast iron stand weighing in at over 2 tonne for a relatively small lathe. They had several of them on their way out to customers. They seem to have settled on a circa 600mm swing now.

**LINK**

John

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LOL Some of the major microscope manufacturers have departed from the standards Neil. I think that even the objective threads may vary now from make to make.

Screw cutting ? We all know that lead screws are made from super hard material that never wears out and is temperature controlled on the lathe to 1 billionth of a degree C and that manufacturers get every lead screw checked by a national physics laboratory so microns must matter.

John

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I mentioned the effect of side rake in another thread Rod. Probably a waste of time but maybe some will try playing around to see what happens. That and top rake can almost make a machine self feed - wish people luck trying to do that with carbide. It's all pretty simple really the top and side rake form a wedge. The the side rake tends to prevent the tool from just feeding itself into the work. There aren't any formulae to work out the angles and model engineering pundits as far as I am aware don't even mention what the rakes do. The sharper the wedge the less cutting power is needed which is where carbide falls down. Deep cuts with carbide tooling needs more power. The problem with hss used like this is that it will wear out more quickly because the wedge is sharper so the cutting edge is finer - that's where the various angles come from in tables that say so much of this for that material etc. They are trying to make the tool last longer.

I have to admit that the rake tipped carbide inserts do improve carbides performance in this area because the allow a more acute wedge but the degree of side rake that can be added is limited. If some one want to use indexed tips though they are ideal for small lathes and allow big sods to work better as well. They also wear out. The only time I have had chipping problems is on a lathe with rather loose head stock bearings. I have had the coating wear off, the finish deteriorates. In fact the drop off is noticeable even before that can really be seen. All HSS needs is a quick polish with stone which can be done in the lathe taking care not to round the cutting edge off. That's best done before there are real any signs of wear. Say just before every finishing cut.

What I have done in the past when I need to remove a lot of metal is grind some top rake into the cut. Say 20 degrees. I then grind the side rake on it and hand feed. If it seems to take a lot of effort I add more side rake and so on. I don't go too far because the tool will tend to grab and self feed at some point especially on softer materials. Fortunately I don't have to do it very often as I hate all of that swarf - it's wasteful. The last time I did it was on a Peatol which really did need help removing a lot of aluminium from a 6in dia start. I should have made the part from 2 pieces really.

John

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Edited By John W1 on 01/09/2015 00:35:00