Lathes & M/C tools

[AndyID]

For a 5 inch chuck Pratt show .0005 TIR , it only increases on 20 inch plus sizes

 

Not on the economy models. What would one have to pay to get half a thou TIR?

[Guest Isambarduk]

Lovely design, far to good for just making models!!!

 

Stephen

 

Thanks.  Interestingly, although I would describe my father as a model engineer who had a great model engineers' workshop, he never actually built a model!  No, he was quite happy making jigs and fixtures to make other tools for his workshop but he often made useful things for around the house and garden.  

 

Occasionally, particularly when we were working together on machining something a bit large for one of my projects, he would comment that he thought that he was a bit odd in his workshop hobby but I well remember the day that he and I were stewards at G0G Bletchley (the predecessor to Guildex at Telford) and he came rushing up to me waving a magazine, the first issue of Model Engineers Workshop, which was written for others just like him.  He was very happy to realise that he was not that odd and he subscribed to the magazine until he died.

 

David

 

Edited January 9, 2017 by Isambarduk

[Izzy]

Sieg CO 'baby' lathe re-motor

 

In early December my little Sieg CO lathe bought in Feb 2012 failed.

 

Thanks to this thread: http://www.rmweb.co.uk/community/index.php?/topic/93330-re-motoring-unimat-sl/  I have been able to re-motor it for about £45 and a little bit of modification, considerably less than the £90-190 it would have cost to obtain the replacement parts which seem to be the cause of the failure, the control board PCB (£89) and /or motor (£98) - nearly as much as the cost of the lathe originally.

 

I thought that perhaps a few shots and some notes might be useful to others as Richard Jones info has been to myself and many others, and for which I will always be grateful.

 

The first job was stripping out all the existing control parts, and re-using those bits needed. Not much really.

 

The 24v 6812 scooter motor I obtained (a 150watt version) has 3 120 degree 3/16" BSF holes in the end plate which I used to bolt it to a fitment end plate made from 4 layers of 2mm acrylic sheet. This was glued together using Plastic Weld glue and tapped for the M6 bolts which hold it in place and allow belt adjustment. As the pulley on the Sieg's motor was 8mm bore (keyed on the shaft), all I had to do was take it off and fit it on the replacement....... getting the belt pulley off the 6812 needed a hammer and cold chisel .............The Sieg pulley was a good fit on the 6812 motor shaft and I have yet to find the need to make/fit a key to lock it onto the shaft - which has a flat on it. The circlip fitting isn't used as the motor shaft is shorter and the pulley needs to be on the end of the shaft.

 

 

 

 

 

Reading the instructions that advised not to switch the LED/CCTV SMS power supply on and off too often for reliability I have fitted this into a box made of more of the acrylic sheet (for electrical insulation and also shows the power/on LED easily) and this sits well away from the lathe on the floor. It's a 230v/4Amp - 24v/15amp/360watt unit with automatic fan so has plenty of holes drilled in the case to match those in the metal case for air flow. It connects to the lathe via a 2-pin plug - with a adapter to ensure it only connects the correct way (since the feeds are +/- DC not AC and I didn't want to blow the speed control PCB with a wrong polarity supply). With hindsight a 3-pin plug connection type would have been better, (automatic correct polarity because of offset pins normally) I just didn't think when I originally got the 2-pin one.

 

 

 

The original DPST on/off power switch is fitted between the power supply and speed control board, as the motor turns slowly on the minimum setting but often stalls or when starting at this setting. A green 3mm LED indicator has been added to show when the power switch is on (using two 1k5 resistors wired in series for the 24v supply) as I find I sometimes need to rotate the lathe/motor to get it to start - but never to be done under power!.

 

Modifications were needed to the ABS control box to fit the speed control PCB unit, cutting a hole in the bottom and raising it slightly to clear the motor casing.

 

 

 

Once past the minimal rpm below which the stall/start problems arise - 1 on the dial - the motor is very powerful if a little more noisy and vibratory than the original 230V/150watt DC one. This may be down to the 12v-40v PWM speed control since these motors are usually powered by 24vDC batteries. It's something I can easily live with, a big bonus being, to my mind anyway, that mains power is now nowhere near the lathe.

 

Izzy

[Vecchio]

be careful that no metal chips or shavings enter your box when it is on the floor - they could easily make a short on the PCB board....

[bertiedog]

If the PWM is too noisy, the output can be suppressed by a capacitor on the output BEFORE the reversing switch. The value is a bit open because of the motor variability in resistance and inductance, but start at 50uf and upwards, trying each value, my guess would be about 500uf ... it acts as partial smoothing, and could be switched in and out of the circuit. Make sure they are rated at 50 volt min, or more.

 

The motor will be quieter on pure DC, but there is a trade off point where a mix of DC and semi smoothed will work to reduce noise

 

 The max capacitor size should be under 3000uf, at that the PWM will be smoothed out I should think. Any capacitor will not affect the overall power available, it may move the power band on the control knob towards the max end. 

The only effect of excess PWM would be in turning a large diameter slowly, where the tip will leave a pulsed mark in time with the pulses. This is only visible rather like looking at a record and seeing the variable groove reflecting.

 

Even precision lathes with a gear drive train will cause the effect, a pattern caused by the gear teeth! Sometimes it is best to get the low speeds by using the belts to allow the motor to run faster for the required turning speed.

Stephen

[Izzy]

be careful that no metal chips or shavings enter your box when it is on the floor - they could easily make a short on the PCB board....

 

Thanks. That's an aspect I had not considered before and suppose it could really be applied to anything similar with air vents in the casing. I'll be careful where I situate the SMS in future. Thankfully the lead to the lathe is fairly long.

 

 

If the PWM is too noisy, the output can be suppressed by a capacitor on the output BEFORE the reversing switch. The value is a bit open because of the motor variability in resistance and inductance, but start at 50uf and upwards, trying each value, my guess would be about 500uf ... it acts as partial smoothing, and could be switched in and out of the circuit. Make sure they are rated at 50 volt min, or more.

 

The motor will be quieter on pure DC, but there is a trade off point where a mix of DC and semi smoothed will work to reduce noise

 

 The max capacitor size should be under 3000uf, at that the PWM will be smoothed out I should think. Any capacitor will not affect the overall power available, it may move the power band on the control knob towards the max end. 

The only effect of excess PWM would be in turning a large diameter slowly, where the tip will leave a pulsed mark in time with the pulses. This is only visible rather like looking at a record and seeing the variable groove reflecting.

 

Even precision lathes with a gear drive train will cause the effect, a pattern caused by the gear teeth! Sometimes it is best to get the low speeds by using the belts to allow the motor to run faster for the required turning speed.

Stephen

 

It's not too bad, and the lathe sits on hard rubber feet which help absorb some of the effect. If it becomes annoying to any great extent I'll certainly follow your advice re trying another smoothing capacitor. There are already two on the PWM PCB, but perhaps they perform other main functions or it's just the nature of the motor design. It's very 'coggy' when turned by hand compared to the original with which I am making comparison, and might be unfair given the differing specs, i.e. 230v DC v 24v DC and the main duties they are both designed for.

 

Interesting about the precision lathes. No doubt the result of the on/off loading nature of spur gears. Metal ones in particular can tend to produce an audible 'tapping' when at anything above minimal tolerances and slow rotation because of this.

 

Izzy

[bertiedog]

We were making test cones to drop into oil to get the viscosity rating for SAE type testing to BS standards, the cone was like a 4 inch funnel, and the tip was a steel spur made to microns accuracy. They were timed to fall down a test column of glass tube filled with the test oil sample.

 

The surface of the cone had to be perfect from the lathe, but then was polished through several grades of diamond paste to a mirror finish. The trouble was the cone"rang" like a bell when cut, suppressed by lumps of blutack!, but any tooth vibration caused a ripple we measured at under a micron, on the reflection it showed a pattern. So the Harrison lathe was tried with thick grease in the gears, then it was fitted with a temp belt drive which cured it. The cones even had to be adjusted and to be accurately weighed by the National Physics lab before sending to the customers.

 

The other thing that affects finish are ball races, they may be precision but not enough for some jobs, which was why Lorch etc., stuck to tapered cones for the main bearings. A ball raced lathe leaves a visible pattern if you know what to look for.

 

Do not worry about it for model work, as most should be second finished anyway, with abrasives, papering, or polishing etc., after which any stray patterns vanish.

 

 i had an interesting experience with the National Physics lab, when they queried the weight of a batch of cones, and said whatever our scales were they were .05% out. Well the scales were second hand, and Polish made, but had a certified set of weights for the simple beam arm scales. I told them, yes , we handled the weights with gloves, and cleaned the bearings on the scales, and with a test weight we though it was near perfect at the 135 grams that I was reading.

 

They suggest that they send them back and we re-weight them as our scales must be wrong, how can the National lab have a worse scale than a Polish ex school design. I pointed out that it was placed for use on a perfectly flat, (earth corrected ) iron table surface at 30C held permanently at that level. Anyway I re-tested the returned set and they came out exactly the same as before, plus or minus nothing.

 

Sent them off to the Lab again and a phone call came in, and a very sheepish gentleman at the lab said he apologised and that I was correct when they weighed them, it seems the first test were done on a brand new electronic scale system from Nikon in Japan, which could work to very close standards. He said they were sending it back to be checked as the source of the error was the electronic scales, which they assumed that they could trust. It beggars belief that they at no point put BS weights on the machine to test it!

 

It shows that experience and skill work better than machines, I was never "taught" to use the scales, just knew from experience what to do after seeing them in use over the years in labs and test stations..

[bertiedog]

If you want a little project that will amaze people when shown it, make a Japanese magic mirror, it is a small metal plate, usually round, that has a copper or silver face on one side and a plain backing plate of copper on the other side.

 

On the closest inspection the front mirror surface is absolutely flat and no markings on it. To clean the mirror it can be done with Brasso and a cloth, nothing special.

 

But take the mirror to a window with bright sunlight falling on it, and then point the reflected light at a wall in shade, and amazing pictures, text or drawings appear in the reflection. A favourite with the Japanese was an engraved looking picture of a Buddha.

 

At this point people suggest that it must be a mirror that is transparent in some way, not solid metal,. but any examination shows solid with no glass etc.

 

The secret is simple, the disc of metal is annealed in a flame to soften it, and then quenched. This does not harden copper or silver, and you then turn the disc over, and with a punch and gravure tools engrave the design into the surface. it must be done with reasonable force.

The disc is then turned over and soldered to a backing plate of the same metal. The marks are now in the middle of the metal sandwich.

 

The secret is to polish the front perfectly flat on stones or grinding plates, using finer pumice stone til the front is absolutely flat and brilliantly polished. It is tested with the sunlight, and nothing will show,

 

But there is another step,and that is to polish it by hand on leather, testing it till the image appears on the wall, in sunlight..

 

The reason it works is the tiny difference between the un-hardened metal and the work hardened metal that the tools created. The soft polishing wears away more in the areas with no hardening, and leaves minute peaks where the marks are.

 

These differences are minute, well under a hundredth of a micron, but enough to deflect the beam of light from the sun more in some areas than others, making the image visible.

 

Although the Japanese used this trick most, it was used by European silver smiths to add secret messages to silverware, especially Church Chalices and plate. It can come as a surprise that old silver reflects in this way, not common, but it does turn up.

[JeffP]

Well I never! You learn some stuff on here, but that beats most of it.

[polybear]

The miniature Peatol lathe produces accurate work, and there are plenty around.  My criticism is that it does not have a driven leadscrew for surfacing work-although a computer counter can be added.  For my 4mm scale work, it is quite capable.  Moving up towards model engineering work, I favour the Colchester Student as a compact, versatile, accurate and reliable unit.  I have found that model engineering machine tools are generally quite expensive, and small ex-industrial machines, such as the Colchester can be a far more economical proposition.

 

The Peatol Lathe (manufactured and sold in the USA as the Taig Lathe) is now available with power feed; the good news is that the power feed attachment is available as a separate kit for retro-fitting to existing Taig/Peatol lathes.  See the following links for info etc:

 

http://www.jeffree.co.uk/Peatol/pricelist.pdf

 

http://www.cartertools.com/

 

http://www.soigeneris.com/taig_lathe_power_feed_kit__1016-details.aspx

 

There's plenty on the web, including videos on YouTube.  The examples and quality of work being produced by some has to be seen to be believed - the links on the CarterTools website should show some.

 

HTH

Brian

 

p.s. Taig also produce a CNC variant of the lathe

Edited January 12, 2017 by polybear

[Daddyman]

Hello, 

I'd like a bit of advice if I may: I don't own a lathe but have been considering getting one, and I've been offered a Simat 101 lathe dirt cheap. I think these were quite good in their time, but would I be able to get spares? Is there anything else I should consider when taking the plunge with this lathe? 

 

Many thanks in advance! 

[raymw]

depends on what dirt cheap is, whether with motor, belts, tooling, etc. Provided the bed is not cracked, virtually everything else can be fabricated. Do you know any body who knows about stuff to give it the once over for you.

[Daddyman]

Thanks. I trust the chap who's giving it away - he's a friend - and if I was going to take someone to see a lathe to give it a once-over, I'd take him. 

 

So no question about the state of the machine, just the availability of spares if I needed any. I've seen a few people say that you can fabricate parts, but - seriously - as a beginner? The first job on a new lathe would be to finish the lathe?! 

 

The motor may or may not be present. The chap is awaiting an operation at the moment so I don't want to pester him too much with questions. If there were no motor, what would my options be? 

 

Please bear in mind you're talking to a literature Ph.D here, so use very small words! Thanks. 

[PatB]

No cheap or free lathe should ever be refused.

 

As for finishing the lathe as a first, beginner project, whilst it may seem a little ambitious, you wouldn't be the first by any means .

[Guest Isambarduk]

Amazing!  What fun!    David

[Izzy]

I believe the Simat was the forerunner to the current Cowells so some spares might be available that way. However I doubt they would be cheap given the basic cost of a Cowells these days, and of course specifications may well have been upgraded/changed in numerous ways so parts appear similar but don't fit.

 

Doing basic web searches should bring up quite a bit of useful information on which you can muse.

 

There is a lot of useful knowledge and help online on which you can draw. My earlier posting on re-motoring my little Sieg shows that this was key in helping achieve that.

 

Just keep asking, I am sure help will always be forthcoming, whatever the nature of the question.

 

Izzy

Edited January 19, 2017 by Izzy

[Daddyman]

Thanks! And thanks for using small words - I understand everything you all said! 

[bertiedog]

The Simat was a descendant of the Zyto type, and usually has a longer bed than the Cowell, which is the same pattern layout. Spares should be no problem for a Simat that is complete, only a broken bed would affect it. The Simat was offered as a self assembly kit of parts as well as complete.

 

All fittings are as standard as you can get, it should give no trouble at all. The main type of motor would be a reversible mains type as used by most small lathes or a DC type as described earlier.

 

You would have to make a pulley frame to take different pulley combinations, parts are done by Picador, but once the lathe is running on a single belt at about 250 RPM, then other pulleys can be machined to extend the speed range.

 

Tools are standard as is the tailstock which will take chucks and centres. The nose is the same thread as a Cowell or small Zyto, so no troubles with backplates or Chucks.

 

Stephen

[bertiedog]

The history of the Simat, Adept, and Flexispeed lathes is on   http://www.lathes.co.uk/flexy/index.html

 

It shows all the models and the accessories made, and gives an idea of the pulleys required.

 

Stephen.

[raymw]

What you have to do, is form 'relationships' with local manufacturers/repairers  of stuff, big and small. Not so easy these days, but still possible. Then you can blag bits from them. In exchange, you can offer them your literature skills, say, or offer to sweep the floor/whatever. Then you will find that quite often the odd bit of scrap metal, free machining time/whatever will come your way, if what you are trying to do interests them. Many folk will go out of their way to help, provided they are approached in the right way, and they are not being exploited. They only thing is, I hope you live far enough away from me, that you don't end up stealing my suppliers.

[Daddyman]

The history of the Simat, Adept, and Flexispeed lathes is on   http://www.lathes.co.uk/flexy/index.html

 

It shows all the models and the accessories made, and gives an idea of the pulleys required.

 

Stephen.

Thanks! I think I know what a pulley is. Now I just need to work out why a lathe would need one.... 

[Izzy]

Thanks! I think I know what a pulley is. Now I just need to work out why a lathe would need one.... 

 

Just in case you were serious regarding pulleys, they are used as the most common and effective means of power transfer between whatever provides the power (electric motor, steam engine, treadle, etc), and the lathe. As variable speed motor control via electronics is a fairly recent development for general use the usual way of providing a range of mandrel speeds has been to use stepped pulleys in various combinations. Often this may involve an intermediate layshaft between the headstock and drive shaft/motor, usually arranged to lock at the correct belt tension, and of course releasing to allow the belt to be moved to another pair of pulleys. The lovely lathe in post #829 has this arrangement.

 

Izzy

[Daddyman]

Just in case you were serious regarding pulleys, they are used as the most common and effective means of power transfer between whatever provides the power (electric motor, steam engine, treadle, etc), and the lathe. As variable speed motor control via electronics is a fairly recent development for general use the usual way of providing a range of mandrel speeds has been to use stepped pulleys in various combinations. Often this may involve an intermediate layshaft between the headstock and drive shaft/motor, usually arranged to lock at the correct belt tension, and of course releasing to allow the belt to be moved to another pair of pulleys. The lovely lathe in post #829 has this arrangement.

 

Izzy

Thanks. I thought that's what purpose they served, but nice to have confirmation. The pulleys work like sprockets on a bike, with different sizes producing different speeds? And the difference between an old lathe like the 101 and a modern one is that speed control is done by manually changing pulleys? There's no "derailleur" in old lathes? 

 

I'll check out post 829, thanks! 

[Izzy]

Thanks. I thought that's what purpose they served, but nice to have confirmation. The pulleys work like sprockets on a bike, with different sizes producing different speeds? And the difference between an old lathe like the 101 and a modern one is that speed control is done by manually changing pulleys? There's no "derailleur" in old lathes? 

 

I'll check out post 829, thanks! 

 

Some lathes can have all geared heads with a range of speeds, it's the same with milling machines and other similar tools, but changing speed whilst machining isn't normal simply because of the effect it can have on the quality of finish. All this type of cutting/machining needs smooth and constant power delivery to ensure good surface finish and prevent damage to cutting tools through 'snatching' at the cutting edge which can ruin both cutting tool and workpiece in a worst case scenario.

 

A lot of lathes today e.g. the current Cowells - the modern Simat 101 - still use multi-step pulleys for speed choice.

 

see here: http://www.cowells.com/90e.htm

 

and here is the price list: http://www.cowells.com/pricelist.htm

 

enjoy!.......

 

Izzy

[jrg1]

Photographs of machine shops prior to electric drives show installed drive shafts with pulley take offs for individual machines.  The shafts woud be driven by a steam engine at one end. Apart from the noise, the maintenance of shafting and belt replacement would have been eye-watering.