Member postings for Max Tolerance

For many years I have used a similar method for tramming my mill head, except that instead of turning a piece of steel I use a large bearing inner ring. The one I have is around 220mm diameter and came from a scrap taper roller bearing at work. Needless to say these rings are ground to a very close tolerance and they are also hardened which is a bonus. The inner rings usually don't have any numbers engraved in them so there are no indentations to throw the readings out. Also of course you avoid the T slots in the table.

I have designed and made many "pouch" machines in the past. As well as doing repairs and maintenance on them. As a previous poster has described there are generally two different sealing operations. The plastic film is usually supplied as a single web on a roll. This is first formed into a tube by folding it over a hollow metal former and sealing the overlap, creating a continuous plastic tube. When the tube has been formed and before it leaves the former, the desired contents of the pouch are fed down the hollow former. As the film leaves the former it is first of all gripped by a pair of heated jaws and pulled down off the former. The action of these jaws is to make a seal in the tube and the distance the film is pulled will determine the length of the pouch.The jaws then release and return to the start position ready to pull the next pouch down off the former.

Now, both sealing operations are done using heat. There are a number of parameters to consider such as the temperature of the sealing head, the pressure applied and the time the heat is in contact with the film. The film itself will be extruded using different layers of various types of plastic. that is to say that the seemingly single layer of film will actually be composed of a number of different plastic types extruded and bonded together. The inside layer will be of an easily welded polymer and the outer layer will generally be a barrier film, typically a type of nylon. With probably, other layers as well to give the film strength or other properties.

The sealing heads can be either solid metal with an internal electric heating element. Or it can be a narrow flat band of ni-chrome heating tape heated by resistance to electric current. Sometimes the current is continuous and sometimes it is pulsed. Which ever type is used there will be a temperature control to keep it at the set temperature. This is generally in the region of 130 to 230 degrees C.Each method has advantages and dis-advantages and the type will be determined in the machine.design stage. All sealing heads need to be aligned properly so that contact is continuous and even, all along the contact point. The pressure applied should be equal at all points. The crucial thing is that the heated head MUST NOT come into direct contact with the film or the film will stick to the head and melt and burn. To prevent this a piece of PTFE coated glass fiber cloth (known as teflon in the trade) is placed over the heads. The grade of teflon and its quality will determine its life span.As always quality and cost are related!! When new, teflon looks like a shiny buff coloured ( it can come in other colours) fairly stiff material. If it gets too hot or burnt it will have a distinct line where the heat has been applied. Therefore it has to be monitored in use and changed regularly. If the teflon is damaged or burnt you will not get a seal. If the temperature is too low you will not get a seal. If the temperature is too high the film will stretch or burn through. If the head is damaged or mis-aligned you will have partial seals. If the pressure applied is too low you will have no seal. A perfect seal should be even, flat and have the imprint of the woven glass cloth visible when held up to a bright light.

The local mechanics should be able to maintain one of these machines when they understand how they work. However local supplies of the specialist materials Ni-chrome wire, teflon, silicone pads etcetera may not be available. If not, you will not be able to run the machines.

Joseph Whitworth did a lot of things during his life. He had at one time the largest machine tool manufacturing company in the world This was in Manchester. He also had a large house built in Fallowfield set in 52 acres. He became interested in fire arms when he was asked to look into the problem of accuracy of the current smooth bore rifles and whether it was possible to make a a rifled barrel. At the time the science of ballistics hadn't been invented. So, Joseph had a long brick building erected in his house grounds. Where he would hang sheets of paper from the ceiling and fired various guns etc. The bullet (or more accurately the ball) would leave a series of holes in the paper and show the trajectory of the projectile. From this he designed the hexagonal bore as a way of spinning the bullet and improving the accuracy.

He also built larger guns for trails for the navy and army. The trials were carried out on Southport sands but his rival Lord Armstrong was also trying for the contract. Needless to say a Lord trumps an uneducated northerner and the contract went to Armstrong even though his guns were less accurate. Interestingly another witness to these trials was a German by the name of Krupp. But that is another story.

Be very careful about claimed magnification in any optical device. The real test of an instrument is its resolution. The ability to show details and resolve minute differences in size, shape, colour etc. There is in microscope circles something called empty magnification where the view may be bigger but no more detail is revealed. There is a definite limit to the resolving power of even the finest optical microscopes. This is one of the reasons why different techniques such as dark field,oil immersion, polarization etc. are used.

However, for the purpose you intend it for you would not need such high magnification. And in all probability a cheap electronic device may well serve your needs. As always with these devices the sensor, and the screen will decide the quality of the image. A large magnification with a very poor screen will not show anything worth having. A lower magnification but with a high definition screen will reveal much more.

As the previous poster says, look at real world images taken with the camera, microscope , whatever and decide if the quality is sufficient from that.

I have a full workshop in my cellar.I have lathes, mills, grinders, drills etc.etc. All my machines are three phase and I am fortunate to have a three phase supply so I don't need converters / inverters. The normal house hold electrics are of course single phase. I have most of the house on red (Brown) phase. The kitchen is on Yellow ( gray) phase and the only use of the Blue (Black) phase is my workshop. I also have three meters, one for each phase.

This makes it easy to see how much I typically use running my workshop. And it is a surprisingly small amount. Typically I use around three units on the Blue phase per month. Since the load is always balanced it follows that I use nine units in total. this is despite running some hefty motors etc. In a quiet month I may use three units total and in a very busy month I have been known to use 15 units. Though I must stress the last one was a one-off where I had some serious metal removal jobs in hand.

Compared with the total house usage around 650 units per month it is not worth bothering about.

As the name suggests these rollers are embossed. A single tool is made something like a knurling wheel only more robust. It is then forced under pressure into a softened roller. The embossed roller is then hardened or more frequently hard chrome plated. If a pair is required the first roller is made and hardened and used to emboss the second roller. Ensuring a perfect pattern match.

It shouldn't be a surprise that the electricity consumption was low during the second world war, compared with 2010 or 2021. Not many homes in the UK or Europe had much in the way of electrical appliancies For example refrigerators were very rare and the one's that did exist would have been gas powered. No-one would have a freezer,washing machine, dryer, electric iron, microwave,television etc. etc. Many didn't even have electric light in many rooms of their house. Typically they would have a light in the main rooms with a single lamp (bulb) in each. Some had a mains radio but many (if they had one at all) ran it off batteries.

Industry also relied to a great extent on a central power source and line shafting. Many still had steam or oil engines running their machine shops. The machine tool with an integral electric motor was a novelty. They did exist but were not common. No-one had their own hand power tools they just had hands and elbow grease. Or in a factory they may have had air tools. Ships, artillery guns, tanks were still riveted or screwed together not electrically welded.

Blast furnace's were fired using coal (coked) as were railway locomotives. And of course the humble horse was still a common means of moving equipment and people.

One of the things that most people don't realise is how important the horse was to the army. Many think of the German (and British) army with their "mechanised" divisions with Tanks etc. as per the propaganda news reels and believe that this was how the armies were equiped during WW2. When in fact horses where still the main stay not motor lorry's and tanks. During the Russian campaign a typical German army division would have an allocation of 911 motor vehicles, and 5375 horses!!!. Over 200 divisions were used in the initial invasion. Do the maths.

The real game changer in mechanisation came with the US involvement during the build up to D-day but that is a different story.

I got my first fully electric car in May this year. It has a 64Kw battery pack which it is claimed will give me around 300 miles range. However, because i use regen on braking and because I am not interested in "performance" driving I exceed the figures by about 10 percent. I reckon in summer to get around 330 miles range in general motoring around town. I do use the car on motorways occasionally and have done the trip from east Lancashire to Hull the full round trip a number of times without having to recharge en-route. I can't remember the exact mileage ( it will have been around 130- 140 miles each way) and I still had 45 miles range when I got home. So, even at motorway speeds I reckon the mileage is pretty much the same. One thing that isn't generally realised is that when travelling down hill the car uses very little power from the battery. In fact on my daily commute of around ten miles to work, most of the way there is actually up hill and the range will drop by about 18 miles, Even though the oddometer recordsonly ten miles travelled. However on the way home I actually end up with more miles on the range than when I set off. Simply because the regen braking puts more juice back into the battery than I am actually using.

Now it is winter the range is a bit less probably around 280-290 miles on a full charge. BUT i have the lights etc. on plus the heating (set at 22 degrees) plus the heated steering wheel and drivers seat. I can recharge at work for free or at home for around nine quid, once every three weeks. Even when the front windscreen has been covered with ice over the last week or so, I can clear it without prior heating in around a minute using the cars own front screen heater which is like a fan heater and comes on instantly without having to wait for an IC engine to heat up.

What's not to like? There is too much negative press given to EVs most of which is in-accurate. I agree the first cost is high and problems may start to show when the car gets older. But I have no road tax, no fuel duty to pay, free parking in many places. And free charging as well at many places. Plus the greatest (to me) advantage of quiet driving with only minimum road noise. No reving petrol engine or rattly old diesel sounding like a bag of spanners. No gears or clutch to worry about and even the brake is optional most of the time. It is the easiest car to drive I have ever had.

Briefly, in the beginning there were no standard threads. Joseph Whitworth was the first to recognise the advantages of having a standard set of threads that could be used on fasteners and so make the mass production of nuts and bolts possible and cheaper. Joseph based his thread to give the best results on typical steels and cast metals of his time. These were the days before high tensile and tool steels etc. were available.

These were a real improvement on previous threaded fasteners and since the British tool and manufacturing industries were the largest in the world . So these threads predominated through out the Empire and then the world.

It was recognised that there were problems when the bolt size got below about 1/8th of an inch . When the pitch became too course relative to the diameter. So, in the late nineteenth century a scientific team got together to design threads for small mechanisms, scientific instruments, time pieces etc. They came up with the BA series. which is actually a metric thread form and does follow a fixed ratio between thread diameter and pitch.

Around the same time separate series of threads where brought out for bicycles etc. Where large diameters but fine threads were needed Brass ware and pipe fitting threads where also needed. Auto manufacturers also needed special threads for various components and most developed their own standards.

During the second world war problems were found when US equipment (built to US imperial standards) needed to be repaired in Europe. Where a mixture of old metric and UK imperial was the rule. So was born the unified series meant to be an approximation between the old metric and UK / US imperial.

By the time the ISO standards came out it was decided to standardise on a small number of metric threads designed to offer the greatest strength in the more modern steels now available. There were proposals for around twenty different thread pitches to cover all sizes between 1 mm up to 100 mm. Of course they then needed the "specials" for cameras etc. and so we end up with the wonderful variety of 'Standard ' threads we see today.

Generally the ISO metric thread form offers the best choice for modern steels. Cast iron is probably better with Whitworth form though metric is good too. if you are repairing old cars them you are stuck with whatever was used during manufacture. And watches etc. BA if older and metric if newer. Though BA gives a larger range in the smaller sizes.

Sounds a very odd arrangement to me. Normally grinding spindles, both internal and external would have matched opposed bearings of some type at the business end. In my experience these would be angular contact and would be separated by a spacer and some spring type arrangement to take up the bearings as the spindle warms up and expands. I have never seen one fitted with deep groove bearings of the "normal " type. They are simply not accurate enough or precision use. I suspect the spindle you have has been messed around with at some point and has has these bearings fitted simply because the internal / external dimensions were the same.

Generally if you fit specialist bearings they tend to be wider and this might explain the gap in the spacer. Jones and Shipman made many different spindles over the years and the designs altered over time. They also made "specials" and you may ave one of those. However they would never fit bog standard deep groove bearings to a quality spindle.

As a side note angular contact bearings can be ordered as a matched set with a defined amount of preload. These are matched at the factory and I have used them on precision adjusters etc. where microns matter. However, they come at a price!!!!

It is not generally recognised, but at the end of the nineteenth century and early twentieth there were more electric cars built than IC engined cars. Particularly in America. The electric cars were easier to drive, needed less maintenance and were particularly aimed at the female population who were not capable of understanding how to drive anything else. (From period literature, Not my opinion in these woke days). Believe it or not there were even coin in the slot street chargers available in major cities.

The IC engined cars (petrol) in those days were very prone to breakdown and needed major attention and engine rebuilds etc. every two thousand miles or so. Petrol wasn't leaded so pre ignition was a major issue and explains why they used low compression ratios and large cylinders in banks of six or twelve. Lubrication oil also was primitive and not very effective hence low rev. counts.

The Achilles heal of the electric car was of course the short range (lead acid battery technology) which was even more of an issue in a big country like the US.

The first world war was the turning point in IC engine design but this wasn't aimed at cars it was aimed at aircraft engines. In order to get better power to weight they needed high compression ratios and to do that they found adding lead to the fuel would control it. Better bearings, tolerances, steels and lubricating oils meant the IC engine could come of age and replace the electric and steam cars. The steam cars held on until the early 1920's. After that it was all IC.

The carpenters mate was writing in the late 20's and maybe the very early 30's. As I recall some of his articles and letters were somewhat at odds with the main views of modellers at the time. I remember coming across these articles etc. when reading back numbers of the magazine a few years ago. I can't give any more accurate info. but if you can look at the indexes for these years you should be able to find him. |there used to be two indexes to every volume, one was a subject index the other was an author index.

'In my book , an engineer is someone who has completed to least to university level'

Typical elitist remark. I left school at sixteen. I worked and still work in engineering to this day. I design and build machines that many industrial companies describe as impossible. I did not go to university. However every year I get an invite to Cambridge Kings College where I spend time with some of the brightest young minds in the country. Not to mention the heads of the physics and computer departments and various other professors.All are very interested in what I can do and what I have achieved in my life.

I always tell them that EVERYTHING they eat, drink , touch, watch,or use, from the clothes on their back to their transport and communications, houses and entertainment........ has been designed by an engineer. The whole world as we know it has been shaped and modified by engineers.

But we get our hands dirty so we are not worthy of consideration in some circles. In Japan I would be a mega hero. But I won't get invited to tea with the queen in the U.K.

The plugs are still available and used widely in industrial heating applications. Typically on injection moulding machines and plastic blown film lines, but also on any item where things get hot. Try R.S. or google industrial heating element suppliers. They are normally two piece ceramic with the brass or plated socket pins sandwiched between the two halves and with a stainless or aluminium shell. Though some can be found made of a temperature resistant plastic/ fibrous material instead of the ceramic. They are available in male and female forms though the female is most common. I have found old versions of these made with imperial pins 1/4" but your furnace obviously has the metric pins. Normally silicone sheathed heat resistant cable is used with these plugs and in some cases glass coated high temperature wire. The silicone stuff is good for maybe 250 degrees C and the glass covered wire can easily stand 800 / 900 degrees C. Important if you accidentally drop some hot metal on it.

All the plugs I have seen are rated at 250 volts,

Cellar every time. I have a large one under the entire house so there are a complete suite of rooms. Access from a wooden stair case at the end of the hall but also from outside since the garden is built at a lower level than the front of the house making one wall of the cellar an outside one. There are two external doors and a couple of windows in this wall, so I have been spoiled. I generously allowed my wife to have one room with a window as a wash room and she said I could have the rest. I have a modest !!! workshop with millers,lathes, grinders, drills etc,etc. and three phase power. Benefits are most notable on those filthy winter nights with the rain and wind lashing outside. Just pop down the stairs into the cellar where it is warm (never below 60 F even in the coldest winter) dry, so I have no rust issues, and everything is hidden from the prying eyes of our fellow criminal elements.

How I got all this down there is another story.

Plastic /acetal / polyamide Bearings have been used in engineering for at least the last thirty years to my knowledge. They are used in all sorts of consumer items including vacuum cleaners. Other users are washing machine manufacturers, computer printers, medical equipment, office machines, the car industry and probably a host of others too.

The advantages are cheapness, lightness and the ability to run without lubrication, they are also non rusting. There are companies who manufacture these in the same range of sizes as conventional bearings. Although they normally only cover the smaller sizes. They do not perform well in very highly stressed applications and of course for high temperature work. They can however run at very high speeds if used correctly.

The ceramic bearings mentioned in earlier postings are intended for extreme applications such as high temperature or where there are problems with lubrication etc. Typical uses are turbo chargers model jet engines etc. They are hideously expensive especially in larger sizes.

Many model engineers and home mechanics were encouraged to make parts in WW1 particularly shell bases. A local group would be set up usually with some worthy such as the local vicar in charge. He would send off for the blank bases, normally drop forged, and these would then be sent to each individual worker to be finished turned, threaded, etc. Then collected and posted back to the factory to be fitted to the shells.

As can be imagined many of these bases were no use. The problem was that without gauges and factory methods of Q.C. it was just hit and miss if they fitted or not. It should be remembered that the modern tolerances achievable with today's electrically driven lathes and cheap ( relatively) micrometers where not easy to obtain when many home lathes were treadle powered and calipers and a rule where as accurate as it got. Thread gauges in a home workshop were unheard of.

Some groups proudly produced many thousands of these and were congratulated by the dignitaries of the day for their patriotism and contribution to the war effort. But when you look at the countless millions of shells and other ordnance discharged during the war it must have been a drop in the ocean.

The real work was done on Herbert and Ward capstan lathes using "unskilled" female labour.

When I bought my first house, an end terrace. It had an access path running past the side of the house to a housing estate situated behind the terrace. At some point probably in the mid twenties the local council had installed a street light on the path. However due to the narrow width they were unable to use a standard lamp post so it was fastened to the exterior of my house wall. They set up a payment as "rent" on the patch of wall at one shilling and sixpence (7.5 pence) per year. In the twenties this would have probably been enough for an evening in the pub but by the time I moved in it was not worth having. However every year I received a first class stamped envelope complete with a typed account letter and a hand written cheque to the value of 7.5 p signed by the borough treasurer, the accounts dept and the official who had raised the cheque in the first place. What this must have cost the local council I don't know but I would have settled for a small one off payment. I had one of the cheques in a frame in the hallway as a talking point for many years. I would have been embarrassed to present it to the bank.

I had three phase fitted many years ago by the then Norweb local supplier. It is a long story but I was fortunate to have it done for free. One problem that I have found is that since the de-nationalisation of the supply industry it can be quite difficult to find a supplier who will support a three phase supply to a domestic property. Most of them now require meter readings via a website or app. However they only have a system for a single reading on the afore mentioned sites.

This leads to difficulties especially when contacting them over the phone. When you mention three meters they think your property is divided up into flats or that you have an ordinary meter, an off-peak meter, and can't count properly. Other problems can arise if one meter has a lower reading than the other ( normal on a mixed three phase / single phase supply) they then think you are doing something dodgy. It means for me that I am tied to one company who do seem to be able to cope. It also helps that I can work quite happily on three phase and fit my own wiring etc.

I have never had a problem running the domestic system alongside my three phase. Everything was done to sixteenth edition regs. originally and seventeenth edition later (not much difference in three phase) The main advantage of the three phase is the loading on a higher voltage is less than by using a VFC on a lower one. And it does depend on the number and types of machines you want to run. Some of my machines especially the specialist swiss types would be extremely difficult to convert or run on a VFC because of the integral multi pole motors used. Although I have fitted a three phase 415v Input inverter onto one of them for the speed control.

Not sure why you would want to strip one down but they are not really user repairable. The bottom bearing is made as part of the shaft with the inner ring machined as one with the central part and the outer ring as one with the belt pulley. Between the two is a complete compliment of steel balls with no cage. The bearings were greased using a special type. If the spindle is damaged i.e bent it is nearly impossible to do anything with it. If the balls are worn then you will find the inner and outer ring will also be damaged. If there are balls missing then these can be replaced but you will probably find the spindle runs eccentric especially at the higher speeds necessary for fine engraving. Finally the end float adjustment is obtained by careful tightening of the internal screwed parts of which there are a number.

Taylor Hobson used to offer a service repair but obviously this isn't available any more. However Pantograph services employ a number of ex Taylor Hobson people who should be able to help at a price. Unless you can be sure of the provenance of the parts offered on eBay there is a large risk of getting a dodgy unit and I personally would be wary of obtaining one from this route.

I don't think the spindle from a K type machine fits the D machine. But the A,C and D machines all take the same type.