Member postings for Andrew Johnston

I think that the 40 thou per millimetre approximation is good enough at all levels. Let us assume that the gnat is unusually large, and we need to make a final reduction of 0.2mm on the diameter. If we set 8 thou on the cross slide dial, we'll be 0.0032mm undersize on the diameter. The 1 thou divisions on my lathe cross slide dial are about 40 thou apart; so I doubt I could set it more accurately, at 7.874 thou, anyway.

Regards,

Andrew

CB: Yes, I do have drawings. The whole thing was designed in Alibre, so I have 3D models of all parts, plus a 3D assembly. I also have 2D drawings of all parts, although they are only dimensioned sufficiently to allow me to make the parts. The design was based around material, and gear cutter, that I already had. The gears are 13 tooth, 5DP, 20ºPA. The geared rolls are 2.475" in diameter and the free roller is 2.5".

If you want drawings PM me an email address.

Regards,

Andrew

I don't know what thickness the rolls will bend. They were designed to be used with 3" by 3/16" and 5-1/4" by 3/16". Time will tell if my calculations are correct. The design is essentially upside down, ie, the material bends downwards, rather than upwards. That makes the adjustment of the third roller much simpler. The rolls are designed to be bolted to the table of my horizontal mill, the wheel rims eventually forming around the rolls and table.

Jason: I'll stick the rolls in the back of the car and bring them down on Saturday.

Regards,

Andrew

Edit note: The original design had deep 1/4" grooves incorporated so that I could also form the T-piece rings. However, I ended up buying these as laser cut quarter circles to weld together, so the grooves were not needed.

Edited By Andrew Johnston on 24/08/2012 14:35:37

Quite right too! The original 555 had a few problems, high current consumption, taking large current pulses during switching, and was prone to double triggering. A lot of these issues were sorted out when the CMOS versions became available, although you need consider capacitor leakage carefully. Even worse are circuits where one 555 triggers another, and so on. Still, the 555 is better than the original TTL monostable, the 74121.

Regards,

Andrew

Like this?

Andrew

Annoyingly a branch of the same scrap company, but in Biggleswade, which is closer to me, and just down the road from the toolshop I use, said they didn't take turnings, for that I'd need to go to Bedford or Newmarket. There were some large piles of turnings in the scrapyard, probably several tons of steel and aluminium. It looked like the depth of cut on the steel was about 0.25", and 0.5" for aluminium; makes my efforts look rather pathetic. Having said that most of the scrap steel there seemed to be industrial plate and construction sections. While there were some cars and vans delivering scrap most of the vehicles were large lorries, including one from a large local builders merchants.

It never occurred to me to ask about buying. If I was doing my own castings I think I'd prefer to start with virgin metal. Initially some-one looked at my bronze swarf and rather dismissed it as 'class 3' as it was contaminated. However, on the weighing ticket it says class 2, which I assume is worth more per kilo.

When I was machining a lot of aluminium on the CNC mill I enquired of a few local machine shops about getting rid of swarf. They mostly did the same as JohnS, put everything (and I mean everything, metal, oil, dirty rags etc) in a large container, and a man with a van came round and took it away for free.

From a commercial point of view I guess it's not worth taking swarf to the scrapyard unless you're producing large amounts of the stuff, and it's clean and separated into the various metals, in which case the yard may collect it anyway.

Regards,

Andrew

Looking good Stub, I'll bet you're as pleased as punch! When do you break out the bubbly, and do we get a glass too?

Regards,

Andrew

Finally got to test the Haimer Centro this evening, now that I have a 16mm R8 collet to hand. I followed the instructions and centred on a hole in an aluminium plate. The hole had been previously bored in the lathe as part of a jig, so I am assuming that it is round to a better degree than I can measure. Once the movement of needle on the Centro was minimised I zero'd the DRO in absolute mode. I then replaced the Centro with a 3/4" collet and a short length of 3/4" silver steel. Having put the DRO in incremental mode I then zero'd on the hole centre by using my normal method. In other words, touch the silver steel on one side, by trapping a fag paper, and zero the DRO. Then touch the opposite side and use the '1/2' function on the DRO to go to half way, ie, the centre. Repeat for the other axis.

I then turned the handles until the DRO showed zero according to the Centro and switched from absolute to incremental mode to see what the difference was. The answer was 0.025mm in X and 0.05mm in Y. I would have hoped for better than that. The question is, which one, if either, is accurate?

Some possible errors are: the runout on the silver steel at the tip is about 0,01mm. Judging the degree of 'trap' on the fag paper is open to error. The fag paper measures 0.02mm thick. If you overshot the touch point with the silver steel slightly, one might change the alignment of said silver steel very slightly.

I've had a think about how I check the results. This is what I've come up with. I bore a recess in a flat plate on the lathe. I then use one or other of the centring methods to set the DRO at zero on the nominal centre on the mill. I then drill/bore a smaller hole right through with the DRO set on zero. Then replace the plate in the lathe and set it to run true using the original bored recess. The DTI can then be used to measure the runout of the smaller bored hole. This should tell me what the concentricity between the holes is, and hence the accuracy of the initial centring.

Regards,

Andrew

I took a load of scrap metal, mainly swarf, to a large commercial scrap yard yesterday. It's the first time I've got rid of scrap metal in return for cash. It was an 'interesting' experience, but not one I will be rushing to repeat. I had the following in the car:

45kg of cast iron swarf and discarded castings

35kg of steel turnings

6kg of aluminium turnings

7kg of gunmetal/brass/ bronze turnings

After a hiccup about the sequence I realised I had to queue up to go onto the ingoing weighbridge and then go into the office. During my trip to the office the computer fell over, not a good start. I also needed a photo driving licence for ID; no license no cash, that simple. Eventually I got a paper slip, plus a hard hat and hi-viz jacket and was told to 'go over there' and wait for the man in a white hat. After having to ask again on the way, I did eventually see a man in a white hat, who directed me to dump the cast iron and steel in one of several huge heaps. There were some old cars, but it seemed to be mostly industrial scrap; thousands of tons of it.

I then did a 'tour' of the scrapyard one-way system to the non-ferrous section, where a forklift eventually dropped off a large steel container at the back of my car. I put the aluminium and bronze in this, and it was then taken into the nearby shed and the scrap weighed separately. At the end of this, plus a few 'choice' phrases from the operator, as he'd just made a boo-boo and was expecting some interesting words with his boss, I got a second ticket detailing the weights of aluminium and bronze. Then back to the entrance to queue for the weighbridge on the way out.

Once on the weighbridge, back into the office, hand back the hard hat and jacket, and all the bits of paper. After a magic calculation cash was handed over.

In total I got £29, which was rather more than I was expecting having talked to the yard before going there. It broke down as follows:

Cast iron/steel - £11

Aluminium/bronze - £18

I was there nearly an hour and half and it's a 30+ plus mile round trip. Was it worth it; probably not. Apart from anything else I count myself lucky to get out with four functioning tyres on the car, given the amount of scrap lying all over the ground.

In future I think I'll make more regular trips to the closer council tip to get rid of steel scrap. It's just not worth enough to make a trip to a proper scrapyard worthwhile. However, I plan to keep aluminium and copper alloys separately and once I've got enough then visit the scrapyard again. Two advantages of non-ferrous scrap are that it's much more valuable than ferrous weight for weight, and it's weighed individually so you don't need to queue to go on the weighbridge. So the whole sequence should be quicker.

Regards,

Andrew

Edited By Andrew Johnston on 18/08/2012 18:04:48

As has been stated, you cannot 'zap' lithium batteries. Lithium batteries do not suffer from dendrite growth, so 'zapping' will not achieve anything useful.

Early lithium batteries contained metallic lithium, so the results of overheating could be a spectacular fire. The best part of 20 years ago I designed a laboratory grade battery monitor system for NiMh and lithium batteries. When we visited the client (multinational battery company) they had all their lithium batteries outside in steel shipping containers. Apparently they'd had so many fires that the local fire brigade insisted that all the lithium batteries must be outside. As far as I'm aware the newer lithium battery chemistries do not contain lithium metal.

Lithium batteries generally require a CC-CV charging regime; that is constant current up to a certain voltage, followed by constant voltage to end of charge. One problem is that the end of charge voltage needs to be accurately controlled, better than 1%, which has proved to be difficult to achieve in integrated form, across temperature, and at reasonable cost. See here for a discussion **LINK**.

Regards,

Andrew

One thing that hasn't been explicitly mentioned is the material type. Some steels (EN1A) turn like a dream, others (EN3B) can be a pig if the feeds and speeds are wrong. It can also depend upon where the steel was sourced; all suppliers are not equal.

Best Regards,

Andrew

I have always assumed that the US water hardening steels are roughly equivalent to silver steel in the UK, ie, a plain high carbon steel. It generally turns and mills easily, with a slight tendency to tear when turning if conditions are not right. See here for an informal discussion,**LINK**.

Likewise I assume that the US oil hardening steels are roughly equivalent to gauge plate in the UK. I've never turned gauge plate, and have had limited success milling it with HSS cutters. It seems to cut ok and then suddenly it all goes wrong, and the cutter is completely badgered. I surmise that the material gets hot locally, hardens, which blunts the cutter, which heats the material more, and so on. I've had no trouble milling gauge plate with uncoated carbide cutters on both manual and CNC mills.

I have no practical experience of the air hardening grades, and I hesitate to disagree with Gray, but I don't think that air hardening steels are classified as HSS. Unlike HSS it should be easy enough to harden the air grades in the home workshop. I suspect that these grades are unlikely to available from the normal ME suppliers, but are available from specialist steel stockists, see here **LINK**.

Best Regards,

Andrew

A Britan Lathe Company in Newmarket appears on internet searches but the links always end up at useless websites claiming that all they've done is gather publicly available information. Complete waste of electrons! I did a search on Companies House and the Britan Lathe Company was dissolved in 2005. That would square with Andrew Engineering claiming to have acquired the assets of BLC in 2004. Mind you, looking their website **LINK** they don't seem to have done much since.

Mike: Thanks for explanation of the motor controls. It's funny you should mention Pye. The chap I bought the lathe from said he did a toolmaking apprenticeship at Pye Unicam, probably in the late 1950s. I must say that cycles and radios seems a funny mix of things to sell. Maybe they missed a chance to invent the Walkman. Once we decamped from the Isaac Newton we used the County Arms on the opposite side of the road (still there) and the Cow and Calf (replaced by flats) on the corner of Pound HIll. In my time there the Cow and Calf was a small, slightly tatty and disreputable Irish pub.

Steve: Now that brings me onto another technical question. What is the best way to sling the lathe for lifting? Are there specific slinging points, or it is a case of aranging the slings in a sensible manner and hoping for the best?

Regards,

Andrew

I'm happy to carry on a discussion on Britan lathes on the forum. May be I misjudged the potential interest. I don't think the Britan lathe is quite history yet. Internet searches throw up a number of engineering companies who list them as part of their inventory. I doubt they'd list them if they weren't using them.

Here's a first technical question. The lathe uses two types of collet I think.; dead length collets for the stock and smaller clockmaker style collets in the tailstock indexer. My lathe comes with a fair number of collets, but does anyone know if these collets are to a standard design, or did Britan invent their own, proprietry, standard? In other words, is there a possibility I can buy new collets that will fit, or am I stuck with what I've got?

Just to clear up one point. As has been stated the lathe runs in 'reverse' in normal operation with the tool bits behind the work. If you want to turn and drill at the same time then you will need left hand drills. I assume this is one reason the lathes are so fast at production, in that you can have two tools working at the same time. However, if the two operations are carried out separately then normal drills can be used, with the lathe running in a 'conventional' direction. I'm sure somebody will correct me if I've got that wrong. Left hand drills seem to be readily available, albeit at a slight premium in price.

Websnail: When I first spoke to the vendor almost the first thing he said was that it was a 1-1/4" version, so clearly more desirable! Did you set up the lathes as well as operate them? I assume that it's fairly simple, in theory. In practise I assume that there are a lot of trial cuts and adjustments of the screws before operating in anger?

Mike: That's really interesting, I'm always keen to hear stories about working in engineering companies. Can you remember which firm in Bedford made the castings? Bedford is my home town; the only casting company in Bedford that springs to mind was Georg Fischer? As I explained to Mike in my PM I used to work in Poseidon House, on Castle Park in Cambridge, which is exactly where Gloucester Street is shown on my street map of Cambridge. My map must date from 1980, when I first came to live in Cambridge. Sadly the street is no longer marked on current maps. On the corner of what was Gloucester Street is the Isaac Newton pub, which I assume was built around 1990 when Castle Park was developed. Does anyone know if there was a pub there before the redevelopment? I used to drink in the Isaac Newton, before I fell out with the landlord.

Steve: Interesting picture; I guess the key questions are what collet capacity and how much tooling is available? For anybody thinking of buying, and moving, a Britan, it's quite a small lathe. I measured the footprint of mine at roughly 38" by 24", weight about 1000lbs I'd guess? So, easily moveable with a car and trailer.

Right coffee break over, back to work!

Regards,

Andrew

Hi Hansrudolf,

Thanks for posting the pictures. It looks like a lovely lathe; in pretty good condition too. Does it have a removable gap piece? The gap seems quite wide. If there isn't a gap piece I wonder how you get on turning near the chuck; it looks like the saddle will come off the bed ways?

Best Regards,

Andrew

Hi Mike,

Wow, never thought I would get a reply from somebody who actually worked at the Britan factory! I'm sure you've got some interesting stories. I understand that the company started in Gloucester Street in Cambridge? Were they still there in your time with them? I'll definitely be interested in getting any help I can with understanding the set up and running of the machine.

I'll send you PM, rather than clog up the forum with a discussion of what is clearly a rather specialised piece of machinery.

Regards,

Andrew

Edited By Andrew Johnston on 08/08/2012 13:32:35

Thanks for the links. I've read the lathes.co.uk page, downloaded the manual and a few years ago I bought the manual on CD from lathes.co.uk. Sadly the CD seems to have gone AWOL as it cannot now be read properly by either my home or business PC. Rather annoying, as it wasn't cheap.

Anyway, I'm now the 'proud' owner of a Britan repetition lathe, complete with pneumatic bar feeder, loads of collets, several boxes of left hand drills, and lots of other accessories and tools including a couple of rather nice Coventry dieheads and loads of dies. I also bought a large angle plate, a pair of large V blocks, a pair of small V blocks, assorted Morse taper drills and a rather neat 1"-2" M&W internal micrometer and a Wolf double ended grinder. I passed on a Colchester Bantam 1600 (too small for me), a superb Bridgeport in much better condition than mine (fair price but too expensive for me), a compressor (just bought a new one - dooooh) and a Meddings pillar drill.

David: I'll need all the help I can get when learning to run the Britan! I have a proper three phase supply at home, so at least that shouldn't be an issue.

Regards,

Andrew

Edited By Andrew Johnston on 06/08/2012 23:32:03

I've made a few more measurements using the Haimer Zero Master; same technique as before.

On the CNC mill the maximium runout was 0.02mm. It is difficult to tell exactly, as I'm relying on the Mach3 screen readout for comparison. At each step one can hear the stepper motor clicking, and the display increments, but the Haimer needle doesn't move. After a few clicks the table might suddenly move 0.005-0.0075mm. I guess this is a static friction versus dynamic friction effect, plus a little bit of free play in the drive system.

I also did a measurement on the Bridgeport, but with the holder not pulled up tight on spindle nose. Total error in this case was 0.03mm. Again not easy to judge as the resolution of my DRO is 0.005mm.

From these tests it seems clear that the spindle nose on the Bridgeport is a bit out. As for the rest of the measurements I feel that I'm operating at the limits of my equipment. Time to cogitate; I feel that if I jump in a try to adjust the errors I'll end up chasing my tail as some of the 'errors' will be in the measurement system itself.

I have adjusted the Z axis zero on the Haimer and I tested that against a 10mm gauge block on the CNC mill, pretty much spot on, better than 0.005mm indicated.

Regards,

Andrew

I'm going to have a look round a professional machine shop tomorrow evening where the two owners are retiring and selling up. I've already had a chat with one of the owners to get an idea of what they have. Among the machine tools is a Britan repetition lathe, which they assumed I wouldn't interested in. Wrong!

I've always been fascinated by them since I saw one working a few years ago. Depending on the overall size I might just be able to squeeze it in, if I re-arrange things, or may be get rid of another machine tool.

Has anyone got any esperience of using these lathes? I understand that they are not easy to set up, so am I just being an idiot for considering it? Also any idea of price? It's a 1-1/4" collet size machine and is supposed to be well tooled. I seem to recall that Britan lathes on Ebay go for low hundreds of pounds, albeit not generally well tooled.

Regards,

Andrew

No, but I have recently bought the equivalent from Haimer:

In due course, once I've tried it out, I'll report in.

Regards,

Andrew