Here is a list of all the postings Nigel McBurney 1 has made in our forums. Click on a thread name to jump to the thread.
|Thread: Blacking engraved lines|
In my instrument making days.long ago,scales and verniers in brass or nickel silver were made on linear or circular dividing machine ,depth was approx 4 thou ,any slight burrs were removed with a water of Aire stone, the divisions were filled with black sealing wax applied hot, the excess scraped off with scrapers made from old hacksaw blades or when getting close to finishing ,aluminium scrapers then finishing up with extremely fine polishing grade emery paper,the finished scales were then sprayed with clear cellulose varnish, Engraving wax could not be used as the wax and varnish did not agree with each other. Items which required deeper marking ie nickel silver micrometer thimbles were filled with black engraving wax and just left polished.I aquired on of my old companies products a measuring microscope at least 55 years old and the engraving is still in good order.All sounds a bit laborious and rather trying,especially if a scale was scratched,it meant that the whole scale was machined to remove the markings and start again, batch quantities could be up to a hundred,with even more work on the circular scales of 100 batches of spectrometers.All a bit tedious and the reason why I moved on to get wider experience in other more interesting aspects of engineering .
|Thread: A gas engine question|
Regarding engine cooling,the water outlet must be from the top of the cylinder, then slope upwards the top of the cooling tank to ensure the thermo syphon operates effectively,when setting up an engine ,do not make a posh tank arrangement just try various size containers when an optimum size is achieved make a good tank of the same volume.old (non Diesel)stationary engines did not run on high compression ratios,lower ratios give nice slow running and do not produce so much waste heat. Now valve overlap,I have found ,even on early engines there is always some valve overlap,there was a comment that hit and miss engines would run hard and and not be allowed to hit and miss,which would allow air only to be drawn through the engine and help with cooling, there are numerous instances on work where the engine does idle then pick up again, instance log sawing the engine idles when the operator has to pick up the next length of wood,but you must wait for the engine to fire before pushing the wood into the saw otherwise it will stall. Throtle governing was used on petrol /paraffin engines to keep the cylinder head /vapouriser hot to ensure the fuel was vaporised. Most owners of full size gas engine prefer to use propane set at about 3/4 to 1 pound per square inch read on a gauge mounted close to the gas cylinder regulator and then a gas bag in the fuel pipe,setting up and adjusting the air gas fuel ratio can be difficult,unlike petrol ,gas will not run weak or rich so a petrol set up is far easier, i have 3 gardners,two are gas with hot tube ignition and the other is petrol and magneto ignition,the early 1906 gas engines runs beautifully but the lamp for the hot tube can easily get blown out on a windy rallyfield,the petrol engine keeps running if its blowing a gale,and it is noticeable that the 1910 petrol Gardner has a higher compression ratio and a lot more power.
|Thread: Myford 33t and 34t gears for metric threads|
I trained and worked for six years as a scientific instrument maker and I never saw anyone screwcut a BA thread or indeed later in my life of engineering ,thousands of BA threads were cut using split dies and they did not wobble,provided a sliding die holder was used,I can recall ,that in our works some 60 years ago only one job ,a steel 1 BA screw was produced in batches of 2k that used the self opening dieholder. on a Ward 2A capstan, I can never understand why BA was ever thought of though I gather that it was instigated by a commitee and we well know the rubbish committees invent. In the smaller tooth sizes I do not see any problems with running mixed tooth angles together at slow speeds and relative short running time.
|Thread: Cast Iron Straight Edge|
Natural "weathering ' iron castings was a very good way of stress relieving iron castings there was the daily temperature cycle and then the annual cycle from winter to summer temperature cycle,this produced very stable casting in good quality iron and was quite common practice 50 years ago, the very best makers of precision tools would leave them out longer,iwas informed jig borer makers would leave them up to 3 years, its no good telling the buyer of a very expensive tool expected to be accurate to within 2 tenths of a thou over the capacity of the machine that its not as accurate as specified because the accountants did not like the slow procees,I once was in technical contact with a swiss jig boring company,their machines had a normal life of 40 years before reconditioning was reqired ,when a borer table was machined and scaped in a minimum of 3 millimeters was machined from the table as it was found that a stress was built up in the surface of the table dues to years of clamping work to the table and they found that it was essential to remove a least 3mm to remove this local stress.The company where I did my training made a range of optical benches up to 2 metere long and these castings spent a long time in the stores prior to machining and were used in a first in first out arrangement. The problem with car cylinder blocks is that the bores tend to go out of round as the motor industry did very little in in stabilising the castings in the 1960s it was found that if the cylinder head of one popular car was removed for say a decoke ,some of the engines would tend to burn oil,and it was believed at the time that the removal of the head removed a clamping force ,the block relaxed and the internal stresses released tended to cause bore ovality.When of a visit to Massey Fergusson at Coventry I found that there was no stress relieving of the iron castings,but on the other hand ,all steel bar material and steel forgings were stress relieved at red heat and there were massive chain bed furnaces which must have cost a fortune to run. Years later I was involved in machining LM25 gravity die castings which had recieved a very precise heat treatment and the metalurgy was strictly controlled,plus machining was under temperature control, I found that even with this control about one in a hundred castings distorted slightly when the clamps were released after machining,I would add that the clamps were not causing the distortion,eliminating distortion caused by internal stress be relieved during machining can be a problem,Perhaps with modern very accurate manufacture very few assemblies are dismantled during the life of a product and a bolted up assembly has no chance to distort,Cars for instanceare now rarely decoked or totally stripped.
|Thread: Progress No2 GS Pillar Drill|
I used to buy old drilling machines do a refurb and paint and sell them,I never found one with a double row race bearing,all were single row,the drill was no doubt intended for industrial use ie 8 hrs a day all week,for hobby use a single row ball race would be adequate just machine up some spacers to accomodate a smaller bearing,lot cheaper. To remove the chuck it needs a brickies club hammer ,the spindle resting on something big and heavy, like an anvil, with a strip of brass between anvil and spindle to prevent bruising then use a home made extractor wedge with about half the taper of a normal morse taper wedge,easiest way would be to modify an existing wedge with an angle grinder, also make sure the wedge is resting on top of the chuck tapered arbour and not on some small shoulder or burr in the extraction hole of the spindle,then give a hard single blow rather than a series of lighter blows, you get similar problems with extracting taper gib head keys from flywheels,take time in getting the key drift set up correct then give the drift one almighty blow, lighter taps or blows just have rivitting effect.
|Thread: Brass Hex Socket Set Screws|
Assuming you are using HSS toolbits these will not mark or burr when secured by socked head grub screws,should you be using hss steel butt welded to tough but unhardened shanks then steel grub screws will burr the shank,brass screws would be suitable for this securing method, one way would be to make up short lengths of round bronze which would be a push fit in the tapped hole and then insert hard steel skt head screws,so that the bronze is sandwiched between the tool and the screw.
|Thread: Cast Iron Straight Edge|
Better to get an old English made straight ,where the castings were allowed to "weather" to relieve the internal stress and were often rough machined and then left to stand for some time before final finishing,Using new "green" castings is not a good idea,Try the second hand tool dealers.
|Thread: Bending copper pipe|
For stationary engine work I use thick walled copper pipe which when annealed forms easily around a round steel of brass bar ,the pipe is available from ME suppliers who stock cu pipe ,tube and plate for loco boilers.
|Thread: First attempt at threading on a bantam - all didn't go well|
En1A leaded is even better, single phase motors do not like too many stop /starts or forward to reverse,most larger motor s have a rating of so many starts per hour,usually specified in the manufacturers literature but not on the motor plate.
|Thread: Siezed Drill Chuck in a Tailstock|
If you use wedges or some pulling arrangement ,ensure that it engages between the back of the chuck and the tailstock barrel,if the force is exerted against the tailstock casting, the resultant force will be applied to the screw and nut of the tailstock resulting in lots of damage,ie the screw,or the nut which is just pressed into the inner end of the the barrel(Myford),The opposed pairs of wedges work well,a single wedge with its unequal leverage could in the extreme bend the drill chuck arbour.
|Thread: More help please|
Have seen it happen when I was an apprentice,and have had it happen to me once ,the set up was rigid and on a good Adcock and Shipley mill. I had bought a lot of gear cutters at an auction all in good condition except one ,one gear was cut ok, the mating one of different size and change of cutter ended up with a small tooth,the reason after carefully examining the cutter was that the cutting edge on the teeth on one side of the cutter had rubbed slightly against something hard when used previously to my purchase,so as the cutter went into the cut the blunt side pushed the metal rather than cut and the sharp side cut deeper probably only around a thou per tooth which after 40 teeth is around 40 thou (1 mm) at the last tooth,it was soon corrected on the Clarkson cutter grinder but it meant a new blank and if there is any doubt with a new to me cutter it gets sharpened. The slippage error can be more common when cutting spiral gears,I use stepped and threaded mandrels ,with the nut done up very tightly so there is little chance of the gear moving and a peg fitted to the mandrel to engage with the the keyway if a keyway is specified.
|Thread: Drill quill lube|
All a drill quill needs for lube is some is motor oil not the top grade ,some 10/40 part synthetic is ok and readily available ,Thats all the plain sleeve of the quill on my Fobco drill has had since new (1968) Why go to extremes with lots of fancy sounding oils which are not needed,I have used the specified Hydraulic oil on my square head Colchesters as it can be bought easily in bulk ie 25 litres and cheaper than motor oil.The designs of our model engineering machine tools dates back to the 1950/60/s. just think ,millions of BMC engines and gearboxes used the same oil,similarly a lot of motor cycles used straight 30 oil in their gearboxes so why not use motor oil in our machine tools,though I would not use anything lower than a viscosity of 10 w . One oil to avoid on slideways is the so called heritage and classic oils equivalent to 1920/30/s motor oils,they are ok on machine tools where there is no contact with soluble oil,when those oils are used on lathe slides with a pumped supply of slurry the oil stiffens and the saddle does not slide easily,yet there is no problem with a cheap 10/40 motor oil.
|Thread: Setting lathe top slide angle accurately.|
When using a machined face on the side of the topslide,just check that the face is parallel to the top slide vee slides before setting up any angles.
|Thread: Reverse thread cutting|
My first lathe , a 2 !/2 inch EW way back in 1960 had a fixed leadscrew nut,though a previous owner had cut the leadscrew near the headstock and fitted a dog clutch. Quite a nice small lathe .Some years later I bought ML7 ,vast improvement,since then I have read of some ingenious improvements to an EW particularly those by Martin Cleeve and more recently a method ( found on the net) of using one half of the leadscrew nut ,split horizontally and a mechanism to lift the nut into engagement with the leadscrew. I have thought about reverse screwcutting but never tried it as I cut a lot of threads using HSS thread chasers, and that would not work too well if reverse cutting. one thought if an old lathe had a worn leadscrew ,some are/were quite bad at the headstock end of the screw,if the cutting was in reverse the right hand flank of the threads would not have had much use and the pitch of the screw being cut would be far more accurate, unless of course the lathe had been used for a lot of left hand threads.
|Thread: Modern efficiency !!!!!!!!!|
I have the same hobby as Martin Perman and need 4 wheel drive to tow a trailer plus up to 3/4 ton of engine on wet rally fields ,and when I had a 6 inch Burrell there was close to 31/4 tonnes on the back hook, which a Discovery 4 took in its stride though its expensive to buy and run ,and comfortable but with too many electronics to go wrong and AA relay membership essential,though my wife stated that she would not come to shows unless we bought a new Discovery,(a nisasan x trail was an awful tow vehicle, If I lived in Aus or other foreign partsI would pay the extra for a Toyota s reliability.I started on the roads on motor cycles (a reliable Greeves Scottish with its super rubber front suspension remember those) and then bought an1950 A40 Devon pick up ,(to carry the trials bike to events further afield)oh happy days, that Austin handbook stated lubricate the suspension every 500 miles !! In those days one learnt to be able to use the spanners,understand how it worked, and carry lots of tools plus spare plugs,points,condenser ,tape wire and string, This gaining of knowledge and the ability to get home after minor breakdowns taught mine and earlier generations a certain mechanical abilty which allowed us to tackle poblems and repair on household and other items, Nowadays vehicles are far more reliable,and items which do go wrong are difficult to diagnose and repair without some computer input, but later generations never had the chance to learn on simpler less efficient mechanics and nowaday do not have a clue how to tackle anything other than a keyboard.So whats the point of making household items repairable An awful lot of people cannot change a wheel,Oh I forgot cars dont have spare wheels now!! ( mine Do) and the trailer.Though modern vehicles are far more reliable, I have found that my old mk 1 range rover was a far better off road vehicle than my discovery with its crap electronic controls which are supposed to improve traction but dont.
|Thread: Best way to turn long, thin brass job|
It is not adviseable to turn down brass rod of this length from 1/4 to 1/16 ,the core of a drawn rod is very weak. if you take a piece of 1/16 brass rod say brazing rod it can be bent and twisted without breaking,now turn a piece of 1/4 rod and turn say a 3/4 inch length down to approx 1/16 dia does not matter if its tapered or a bit rough and try bending it ,it has nothing like the strength of the brazing rod and easily breaks. In this case of a long needle a two piece fabrication is essential, you might say that the original was one piece,but they were probably made in high volumes and used some heading process to form the larger end. This weakness in the centre of round or hex bars occurrs in other metals so be aware of the problem ,It does not ocurr when making one off bolts as the reduction in diameter is about half, but in the case of the needle the reduction of four times is too great and down to a ery small diameter.
|Thread: harrison m300, spindle run out...bearings?|
Interesting ,particularly the cracked bearing cage on you tube, Trouble is one never knows with used lathes their life history,there are a lot of idiots about who attempt to adjust mechanical items without the handbook and make things worse as they do not attempt to look at the cosequences of "if I tighten this nut will it affect anything else ?''So I still think a complete strip down is essential. The only other snag is to consider is the cost of one or both Gamet bearings more than the lathes value. ? Has anyone tried o replace the Gament bearings with sav top Quality timkens or are Gamet bearings made so they cannot be replaced with cheaper bearings,because does the averager modeller really need super precision bearings,I believe Boxfords use top grade Timkens
You mentioned possible restoration and repaint ,do not use a shotblaster to clean any parts on machine tools with the possible exception of sheet metal covers . If you must clean off the paint use a rotary wire brush in an angle grinder.Regarding your spindle problems,the bronze particles in the oil and the severe overheating of the spindle sound serious and a strip down is essential,on a normal lathe the spindle never gets that hot, I read through this thread yesterday and waited to have a good think,the reader who suggested the bearing cages may be breaking up may be close to the truth,I have seen cages break up on old motorcyles,and once saw the table lead screw bearings cages on a large cnc mill break up and and produce oval grooves rather than circular grooveson the workpiece. When the lathe handwheel was broken it may have been a minor shunt with a forklift or a big bang ,ok the hand wheel is away from the spindle,but if the four jaw chuck or a faceplate was fitted at the time that may have also come in contact with some immovable object and given the spindle bearings a big shock,I have also seen machine movers put a lifting strop on the spindle behind the chuck or another favourite is to thread a strop down the spindle bore,put a large spanner into the loop and lift by using the loop at the other end of the stop,both methods putting 2/3 of the lathes weight on the spindle bearings. I would get a handbook,some websites sell handbooks /copies, shop around as some dealers are a bit greedy,assuming Harrisons are still in business,try a phone call.Also when stripped check the straightness of the spindle,if there is a slight error ie bent this may have caused bearing damage in the first place,and it would be a waste of time time fitting new bearings to a damaged shaft.
|Thread: Ever seen this "Drill Pad" as described by Workshop Practice Series?|
I have a vee pad that fits my Colchester tailstock, very good for quickly drilling split pin holes central in clevis pins,and pins found on stationary engines eg valve rocker pivots,governor pivots etc, Headed small clevis pins such as found on classic m/cycle brake linkages will not sit in the vee,so I drill the rod before it is machined down to form the head,Before I found my tailstock pad I used to mount an old angle plate on the Myford cross slide,the plate had a vee machined at centre height,I usually hold the pins in place with a toolmakers clamp. The cross slide method does allow two or more cross holes to be drilled parallel to each other,looks better if the split pins are in line,
|Thread: How far to be off tool centre before a turned finish becomes poor?|
when turning O/dia with tool below centre front clearance will increase and rake decrease so the tool will cut, When facing below centre will leave a pip at the centre. With the tool above centre,front tool clearance will be zero or less and the tool will rub and not cut,rake will also be reduced,the detrimental effect will be serous or failure at small diameters and the effect decrease as diameter increases. when facing with a tool above centre the tool will try to ride over the centre pip. Some years ago there was a letter in the model engineer about the writers experience when working at a company in Manchester and no doubt his experience was with a lot heavier engineering,it was stated that the turners when trying to get good finishes on diameters on tougher steels would set the lathe tools above centre height and halved the cutting speed ,Curious ,I tried it on some EN 8 bar a couple of inches in diameter and it worked though the tool must only be set a small amount above centre and plenty of lubricant. With model engineer sized work regarding boring I always set the tool slightly above centre to ensure there is a bit extra clearance as it is all too easy to loose all clearance
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