precise measuring tools and techniques

[sime66]

I split away from the other thread to ask about this whilst you concentrate on getting vespasco’s barrel finished.

I’m after some advice on precise measuring tools and techniques.

I reckon, at a push, I can still read a scale-rule to .25mm with glasses, though my eyesight is fading fast, but were talking about 0.1 mm adjustments; I can see how you get the static head height with feeler gauges, and the volumes with oil, but how can you possibly measure a port height, or other dimensions looking down a barrel? With the depth bit on a digital vernier? I can’t see that being anywhere near accurate enough in dark confines with old eyes, nor can I see how you’d get any precise tool in the barrel without risking scratching it, and being certain it was perpendicular to the face or at the right point on the edge of the port and head. I think we've established already that degree wheels aren't accurate enough either. I've also discounted trying to measure from a port-map drawing, which can't be accurate enough either, when such tiny mms are big differences.

I could really do with some guidance on tools (links, brand names if possible, - photos of your tools?), and techniques for doing this job accurately enough for all our lovely calcs to be worthwhile.
I need to buy some appropriate kit, and I need to know how best to go about the measuring jobs too.

Cheers, chaps.

[henri]

sorry mate ,my eyes are shot but still rely on a 6" rule an calipers an non-digital verniers ,an "feel" , an a dial gauge indicater an feeler gauges , its what i was taught to use an with practice an always measuring twice n then checking again an averaging the results is accurate enough.you only have to see what the victorian engineers could do with that sort of stuff to know its possible to do work to +-2-3 thou,
for close readings on my best vernier ive a jewellers loop in my shed ,an a magnifying glass aswell , useful for close inspections of bearing surfaces/paint finishes/plugs allsorts.
an a degree wheel can be made more accurate by increasing the diameter an sub-dividing the degree marks ,
end of the day a measuring device is only ever going to be as accurate as the care taken to use it, H

[sime66]

For example; Vespasco’s figures:
· Deck height 0.38mm
· Top of exhaust port to top of cylinder - 37.3mm
· Transfer port height 47.7mm
· 42mm arc measured across the arc of the 69mm bore/ 39.5mm measured straight across
· - Adjusting deck height either 0.1mm or 0.2mm

My question here:
What tools and techniques to get accuracies of 1/10th & 1/100th mm like those stated above, for use in calculations.

Reply:
6" rule an callipers an "feel" , an a dial gauge indicater an feeler gauges an always measuring twice n then checking again an averaging the results is accurate enough. a jewellers loop in my shed ,an a magnifying glass aswell

Does anybody feel inclined to add anything to that?
Bearing in mind the direction of the other thread in which we acknowledged that Garbage In leads to Garbage Out, and that ya need to be careful of what ya measure n record.

[henri]

digital verniers are for wooses , i'm stickin to my old slide vernier scale type ,it measures to a thou n dont let me down with flat batterys , H

[sime66]

………and by eye and feel, you are confident that you can measure, for example, Vespasco’s ‘Transfer port height at 47.7mm’ and be confident that it isn’t 47.64mm or 47.76mm, and subsequently carry out the calculations, and make decisions to a degree of accuracy of moving a port by 0.1mm based on your care (and precision) of what you’ve measured and recorded? Your eye can divide a 1mm distance into ten equal increments (twenty in fact for 0.05)? And your ‘feel’ can divide it into 100 increments?

Would you say that, you, pxguru and vespasco would each measure the same barrel to the same accuracy and get the exactly the same results to within 0.05mm? Because unless those figures are absolutely exact to the degree of accuracy stated, the subsequent calculations and decisions aren’t worthwhile, as you previously stated in the other thread.

Vespasco, if you read this; rather than discussing the pro’s and cons of anaologue, digital, or divided-scale, which wasn’t what I actually asked; could you say how you judged exactly where inside the barrel the top of the port was, and what specifically you actually did to make a measurement of 47.7mm to within 0.05mm. My thinking is that as we need to be so accurate in our calculations and decisions then we must be at least as accurate in our measurements, and I’m unconvinced that I currently have a measuring method that would make my calculations worthwhile, which is why I asked if anyone might offer advice on tools or techniques to achieve it.

[sbwnik]

I recognise those calipers - Aldi finest! The battery holder is crap

[vespasco]

Nov 7, 2014 15:26:47 GMT henri said:

sorry mate ,my eyes are shot but still rely on a 6" rule an calipers an non-digital verniers ,an "feel" , an a dial gauge indicater an feeler gauges , its what i was taught to use an with practice an always measuring twice n then checking again an averaging the results is accurate enough.you only have to see what the victorian engineers could do with that sort of stuff to know its possible to do work to +-2-3 thou,
for close readings on my best vernier ive a jewellers loop in my shed ,an a magnifying glass aswell , useful for close inspections of bearing surfaces/paint finishes/plugs allsorts.
an a degree wheel can be made more accurate by increasing the diameter an sub-dividing the degree marks ,
end of the day a measuring device is only ever going to be as accurate as the care taken to use it, H

Totally agree h!
My other main tool amongst the above is a small strong LED pocket torch, helps to see everything muh more clearly!
And thats exactly what im looking for right now! Then Ill take a pic of how i measured the ports....we aint talking Star Trek here either, more Scrapheap Challenge ... However accurate it is/not, it is consistant....
I didnt include n the pic the depth gauge on the verniers i use (old school ones) to actually measure but you get the point i think. 
Right way? Wrong way? As ever....you decide!
I just need to find that torch as theres no flash on this tab  i use (and camera is rubbish - (Lenovo 3g 5500? If youre wondering))

I wont post anymore measuresments as yet, on other thread, not until ive got engine together and measured it all.



Right. Ive changed devices. ...




Can you tell what it is yet?

[vespasco]

Nov 7, 2014 20:56:36 GMT sime66 said:

………and by eye and feel, you are confident that you can measure, for example, Vespasco’s ‘Transfer port height at 47.7mm’ and be confident that it isn’t 47.64mm or 47.76mm, and subsequently carry out the calculations, and make decisions to a degree of accuracy of moving a port by 0.1mm based on your care (and precision) of what you’ve measured and recorded? Your eye can divide a 1mm distance into ten equal increments (twenty in fact for 0.05)? And your ‘feel’ can divide it into 100 increments?

Would you say that, you, pxguru and vespasco would each measure the same barrel to the same accuracy and get the exactly the same results to within 0.05mm? Because unless those figures are absolutely exact to the degree of accuracy stated, the subsequent calculations and decisions aren’t worthwhile, as you previously stated in the other thread.

Vespasco, if you read this; rather than discussing the pro’s and cons of anaologue, digital, or divided-scale, which wasn’t what I actually asked; could you say how you judged exactly where inside the barrel the top of the port was, and what specifically you actually did to make a measurement of 47.7mm to within 0.05mm. My thinking is that as we need to be so accurate in our calculations and decisions then we must be at least as accurate in our measurements, and I’m unconvinced that I currently have a measuring method that would make my calculations worthwhile, which is why I asked if anyone might offer advice on tools or techniques to achieve it.

I some how missed this post....
I think, like to believe, that, for eg, (without meaning to compare myself to the Henri the Great here;) Henri, comin from i beleive an 'engineering' background by the sounds of it, and i also do, so I am confident, using old skool verniers, and for eg, that we would both reach the same masurements using the same tools and methods, to +/- 0.05mm (but im metric)! Certainly to +/- 0.1mm
Feel does come into it too. Trying to determine for eg the very centre/ top of an arched exhaust port is quite difficult. Yet ultimately, without the use of lab euipment and lasers, feel does actually play an important role. You need to be confident that you are indeed at the top of the port, otherwise, why bother taking the time to measure at all? So , you do a good job until you are satisfied you are correct/consistant. How long is a piece of string? It could be about 13" or it could be infinite in the quantum world. I think for our purposes, in each of our own unique workshop conditions, that we should all be able to achieve +/-0.1mm with verniers. A magnifier and light help considerably if conditions are not like they used to be
But we wont all necessarily get the same results if we all measured our own unique different cylinders of same size,make, spec


For things such as these, tools that would not get used too often, but need to be accurate, i tend to go for somethin in the cheaper leagues without going all chinese, like Draper, even Silverline (pro)?  So long as you treat them right they wont go astray 1 set of good verniers will last you a lifetime.
I wouldnt waste my / our time posting figures i wasnt sure about. Typos and blonde moments excluded!

[pxguru]

Easy to get carried away with all the measurements. Accuracy of 0.1mm is enough for what I do. If you can get this kind of linearity across the width of a port ground by hand then you are doing pretty well.
Ports heights should be measured a 2 mm back from the barrel wall. The thing I use most for ports is a cheap digital vernier similar to Gaz's. To get it to measure on the edge of the port I took a saw to it and cut the back off and a little off the nose. Now it fits in fine
I don't consider a degree wheel is accurate enough for porting, as you have to guess where the port is open after the port chamfer is visible. A degree disks only real use is for checking rotary inlet timing, where it's the best thing ever.

[sime66]

Thank you chaps; that’s a lot of very useful info in those last couple of posts.
My question arose from henri stressing how garbage any work would be without accurate measuring, and me having already asked myself if I could confidently measure my own barrel to the degree of accuracy that vespasco had attained in his measurements. I had already decided that a degree wheel, or trying to measure from a tracing/port-map would be insufficient for the accuracy required for those calculations, so some tools and different techniques would be needed. My question was partly about what kit (brands, quality etc.), and it was equally about method, to achieve the required accuracy; but it just went into a discussion of old-school vs digital, which really wasn’t going to get me measuring accurately enough. Now, this morning, I feel considerably more enlightened:
· I see that you do put the jaws of the vernier (whether it is digital or old-school) actually into the barrel itself; I had imagined that the piston would be brought up to the port and somehow the depth to the piston was measured, (with the depth part of the vernier) which leaves loads of areas for error. So, it’s the jaws of the vernier down inside the barrel, as your lovely photos vespasco – thanks. I wasn’t sure it was wise to do so (noted the paper shield – I think?), and I wasn’t sure they would fit down there.
· I was concerned about the edge of the port (chamfering etc) and where to measure to; pxguru has answered that you go deeper into the port, and suggested how to achieve it; perfect info.
· I was concerned about light and eyesight looking at a piston moving over a port inside a barrel, but the description of the method has dealt with those concerns.
· I was concerned about any radius to arched port tops, and this, if it is a problem, has to be done by judgment and care, but to the high point of the port;
· I was concerned about measuring perpendicular to the barrel face, and parallel to the barrel body, but again this is care and feel, experience and skill.
· I was unsure whether I needed to spend £50+ on a Swiss/Chinese vernier, calipers, dividers, rules or whether a tenner on a digital cheapy is good enough. I don’t have beautiful old precision engineering tools in my toolbox to use, so a decision has to be made on how much quality to buy - and there's no point buying quality if i don't know how to use it. Where we were going last night was like arguing over a digital vs analogue speedo, without considering the quality of manufacture, or method of measuring.

I was not questioning anyone’s care or accuracy; I wouldn’t dream of it, and I’d be foolish to ask you if I didn’t respect your skill and experience, I was hoping to learn enough to achieve adequately similar precision, so that I can complete the job that vespasco is doing, without my efforts producing garbage. I stated 0.05mm because that would be required to settle to the nearest 0.1mm by eye. I was questioning whether I had enough information to do that job that accurately myself, and asking for guidance; this morning, on reading those later posts, I do feel that I have made some progress towards that. I doubt that I’m the only person reading this thread who has learned a little about how to do this job. Thanks again.

[pxguru]

Thx Gaz, I don't think we are going to get into grinding barrels here. Too easy to make mistakes and ruin them. And when you are learning you do ruin a few! I spend weeks/months grinding my own kits to get them just right, far beyond what the "professionals" have time to do My Polossi is still going strong and been running 2 years at least but I have a Malossi 210 I am doing at the moment and another PX200 tourer to do soon (might do the same as Vespasco on that one. We'll see).

For here, I am just happy to help with the blue printing exercise, getting engines set up right and jetted in properly really makes a lot of difference. Not that they were not generally ok before but a few tweeks here to set them up to how you use them can make the whole experience that much better

My Mrs just brought me a 2 stroke leaf blower. That's getting tuned soon too!

[henri]

whoops ,seems my flippant answer didnt explain what i meant , if your going to get into accurate measuring your going to get lost in it,its a seperate science with world standards n governing bodys ,
your best tools to measure with an then cut too are a pot of engineers blue,sharp scribe,an old feeler gauges ,an a bit of plate glass.
the blue is a spirit based paint that is brushed on an drys in seconds ,giving a even coat bout a micron thick,
a proper sharp scribe is then used to scratch this layer exposing the shiny steel underneath ,giving a line 1-2 microns wide ,a cd pen or pencil gives 1mm-2mm wide,propelling pencil .5 ,a angled scriber can be used to mark a "washed barrel" ,
the feelers can be bent an held square to bore an give you a straight edge to scribe to ,also they can be marked an placed across a port an port width measured accurately or increased to distances already marked on the ,ie max width = 60% of dia ,its just maths after that to find the length of arc an mark a feeler an then centre it over a port n transfer marks to bore ,
earlier you mentioned a worry about marking/scratching the bore with measuring tools , so long as ya dont go crazy any slight marks will be removed at the last stage where barrel is de-burred/glazed by honing .
you also mention swiss/chinese mics/verniers , if you want accuracy it costs ,its why i avoid digital verniers as ive found them unreliable if cheap,i own 3 verniers ,1 from poundland that sits on the bench for "guesstimating" , 1 clarkes that lives in its box above bench, an 1 dial gauge super accurate 1 i was givin that lives in a felt lined box in a de-humidfyed cuboard n only comes out rarely. same with rules ,a 6" n 12" that hang over bench for everyday an a engineers 12" with inches in 64ths n first 20mm in 1/4mm ,that lives in a oilskin sheath in above mentioned cuboard ,1 tip if using a rule ,dont measure from the end if ya can avoid it ,ends wear n get damaged use the 10mm line .
same with dividers an calipers ,bit anal retentive i know but at the dockyard where i did some training we spent days been showed how to measure ,then measuring bits of steel til we got it right .only then was we allowed within touching range of the holy of holies a "surface table" ,basically a lump of iron thick enough to be thermaly stable an then ground n scraped to be "flat" ,which is where the plate glass comes in , surface tables are mega expensive ,but plate glass is just as if not flatter an strong enuff to have a barrel plonked on it an gives a flat datum to measure from ,an can be used to "lapp" gasket surfaces ,first with 1500-2000 wet n dry then with valve grinding paste ,with patience an care you can change deck height an squish that way ,rather than paying for a skim .
some do porting by degree discs but its more hit an miss ,they spin crank to degree they want n use a scribe to mark barrel along piston edge n then try n dremel to that ,its a art form to get right an mostly guys doing that will quote 2 port timings ,1 they wanted n 1 they got , an as pxguru said to learn you destroy barrels til ya get it right ,thats why i suggested in other thread getting second hand crackered barrels to practice on .as cutting ports straight when the tool obscures most of the view takes practice .
just count yaself lucky you arent thinkin of bike tuning ,where ya got 2/3/4 cylinders n sets of ports that have to match ,
whatever measuring devices you choose ,buy a new set of decent feelers an measure them til ya develope the feel an your numbers match the ones on feelers . H

[henri]

an use em as drifts to knock new bearings in aswell,
an to answer vespaco's question about string length in a infinite universe ,thats easy , you measure from middle to 1 end an double it , easy , now thats "great" thinkin , an yes i did train as a engineer ,a long time ago but never worked as 1 prefering to "runaway with the circus" instead , H

[vespasco]

I just spotted,my verniers are also 'Clarkes' brand!
I also use old bearings as punch/drifts for knocking in new bearings.
In the qunatum world, where would the end of the piece of string actually finish???
I think im sounding more intelligent than i really am, so will leave it there but like your thinking!! String theory makes my head hurt.

[henri]

yep, my middling accuracy verniers are "clarkes" aswell , machine mart specials , have checked em an there pretty accurate , but the thumb wheels not brill so "feel" is important . am afraid my "best" 1's dont have a makers name ,bought at a engineers close down by my dad coz any tool that comes in a felt lined cabinet made box has got to be top quality ,an they are , just wish i had a mill/lathe n the excuse to use em more .
sime if your looking for good quality measuring stuff that isnt super expensive ,auto jumbles n closure sales of garages/engineers an also schools/colleges that are upgrading/closing up. careful inspection to see there not worn out an bargains can be had . i got my calipers for 2-3 quid each at a auto-jumble from a pile on a stall, just looked for makers names over unmarked an extra fancies like milled or graduated thumb wheels an fine thread on the adjustment , when you hold decent next to not the quality will shout out at you .
whichever type you get like torque wrenches they have all to be stored properly an periodically checked/calibrated,H

[sime66]

Now, a little ahead of planned purchase, but I can’t resist a bargain; new listing overnight - I bought two sets of 150mm Mitutoyo Absolute Digimatic Calipers on Ebay this morning, with a view to re-selling one of them to recoup the cost. These are very good quality ones; £80 new in UK, so if anyone is interested PM me. I’ll take some better photos of jaws etc. when they arrive, and leave on here for one week in ‘For Sale’ before putting one set back on Ebay.


www.mitutoyo.co.uk/small-tool-instruments-and-data-management/calipers/500-171-30



Might also be interested in swaps for other quality measuring tools – calipers, dividers, scribes, rules…. that kind of thing to the value of about £30 if anybody has anything, or any suggestions.

[henri]

sorry sime when i get my hands on decent measurers i hang on to em, thats not a brand i recognise but looks good enough quality to do what you want .if ya take care off them the 1 ya keep should last ya , H