2 legged bore gauge

[stevieturbo]

Which one to buy ?

Not looking to spend a fortune. But I'd cautious about the very cheap, no doubt Chinese offerings from as low as £35.

Although I also see a cheap digital one on the dreaded ebay, which has the advantage of offering easy mm or inch measurements as opposed to the more traditional rotary dial gauge which will only be a single unit.

Starret seem to do a decent looking one for around £150, mechanical dial.

it is only for light usage.

Anyone bought or used any ? 50-150mm range

[Simon says]

This looks right up your street http://www.uktools.com/draper-expert-160mm-bore-ga... good quality at a reasonable price

[Stu R]

Mitutoyo or Sunnen. Bit pricey but they'll last forever.

[Yuxi]

Simon says said:

This looks right up your street http://www.uktools.com/draper-expert-160mm-bore-ga... good quality at a reasonable price

This should be OK for occasional use, as long as you have 50 to 160mm micrometers (and calibrated gauge blocks) to set it up.

[stevieturbo]

I seen the draper, just not convinced it will be anything over and above the Chinese stuff.

The Starret one does look at least better packaged

http://www.starrett.co.uk/shop/precision/dial_bore...

Or the dreaded digital ebay item. But from an ease of use point of view. It has to be better, plus both easy metric or imperial units.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&am...


I just dont see stretching to the price of Mitutoyo being worth it for me for something that will only see very light usage as a hobby.

[Steve_D]

For infrequent use how about these.

They are spring loaded so you let them expand in the bore then lock them, feel if you are happy with the setting in the same way you would with a set of feelers then remove and measure with your digital vernier. Avoids the hassle of calibrating the other type.

For £18 including the VAT you could try a set and see how you get on with them.

Steve

[Pumaracing]

stevieturbo said:

I seen the draper, just not convinced it will be anything over and above the Chinese stuff.

The Starret one does look at least better packaged

http://www.starrett.co.uk/shop/precision/dial_bore...

Or the dreaded digital ebay item. But from an ease of use point of view. It has to be better, plus both easy metric or imperial units.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&am...


I just dont see stretching to the price of Mitutoyo being worth it for me for something that will only see very light usage as a hobby.

The Rotagrip is actually cheaper direct from their website.

http://rotagriponline.com/index.php?option=com_vir...

If I didn't already have a 0.0001" Mercer dial bore comparator which has performed sterling service for 20 years or so I'd be very tempted by the digital Rotagrip.

I bought my Mercer second hand but in brand new condition from a metrology company that reconditioned and calibrated measuring equipment. Sadly too long ago to remember who. You might search on Yell and phone a couple up to see what they have in stock.

However, don't confuse resolution with accuracy. A gauge might indicate to 0.0001" or less but not actually be accurate or repeatable to that. Even my Mercer varies by a tenth of a thou or so if I repeat a measurement. However a tenth is nothing when normal piston/bore clearance tolerances are about 1 thou for most engines. I just like to work to finer tolerances.

The digital gauges offer many more options over analogue dial gauges such as absolute or incremental readings so I'd go that way if I had to buy again.

What I can promise you though is that when you actually start measuring the bores of engines that you think have been running perfectly well how big the differences are in bore size, ovality and taper. What this will tell you is that either OE production tolerances are ste or that engines don't really care much about bore dimension. Piston rings do a wonderful job of masking production tolerances.

[Pumaracing]

Steve_D said:

For infrequent use how about these.

They are spring loaded so you let them expand in the bore then lock them, feel if you are happy with the setting in the same way you would with a set of feelers then remove and measure with your digital vernier. Avoids the hassle of calibrating the other type.

For £18 including the VAT you could try a set and see how you get on with them.

Steve

A complete waste of time and money for engine bore measurement and comparison. Slow and tedious to use and only accurate to maybe half a thou or so even with experienced use. With a dial gauge comparator you can gauge a bore from top to bottom and in both axes to a tenth of a thou or two in seconds. With telescopic gauges you can take half an hour and be no wiser once you're finished.

If you'd ever actually performed this task you wouldn't be suggesting these.

[anonymous-user]

Pumaracing said:

What this will tell you is that either OE production tolerances are ste or that engines don't really care much about bore dimension. Piston rings do a wonderful job of masking production tolerances.

So tell me, how did you measure the actual bore dimension when the engine was running and under load??


i.e. OE engine dimensions are NOT set by static measurements, they are set by hrs and hrs of development and durability running that defines the correct bore profile that minimised piston noise, wear, and blowby. Typically, modern ally blocked engines will be tapper finished (because the top bit of the bore is a lot hotter than the bottom bit of the bore) and the might not even be round, depending on piston expansion kinematics.

Generally, on modern mass produced engines the tollerancing is more than sufficent for the application, as generally speaking modern engines simply do not really have gross mechanical failures.


Now sure, if you're pushing the limits you might want to tighten up the tollerances, and why not, but i can tell you that measuring the bore to 0.001mm whilst the block is cold and unstressed tells you absolutely nothing about the shape of it when it is running ;-)

[stevieturbo]

Pumaracing said:

The Rotagrip is actually cheaper direct from their website.

http://rotagriponline.com/index.php?option=com_vir...

If I didn't already have a 0.0001" Mercer dial bore comparator which has performed sterling service for 20 years or so I'd be very tempted by the digital Rotagrip.

I bought my Mercer second hand but in brand new condition from a metrology company that reconditioned and calibrated measuring equipment. Sadly too long ago to remember who. You might search on Yell and phone a couple up to see what they have in stock.

However, don't confuse resolution with accuracy. A gauge might indicate to 0.0001" or less but not actually be accurate or repeatable to that. Even my Mercer varies by a tenth of a thou or so if I repeat a measurement. However a tenth is nothing when normal piston/bore clearance tolerances are about 1 thou for most engines. I just like to work to finer tolerances.

The digital gauges offer many more options over analogue dial gauges such as absolute or incremental readings so I'd go that way if I had to buy again.

What I can promise you though is that when you actually start measuring the bores of engines that you think have been running perfectly well how big the differences are in bore size, ovality and taper. What this will tell you is that either OE production tolerances are ste or that engines don't really care much about bore dimension. Piston rings do a wonderful job of masking production tolerances.

I googled and googled and the only place I could see a digital one was eBay. The seller wouldn't offer a brand name, so I just couldn't trust it. I ordered the starret one last night. I envisage the dial gauge being awkward, but it'll be better than nothing.
And I've little doubt my bores could be all shapes.

[Yuxi]

Max_Torque said:

i.e. OE engine dimensions are NOT set by static measurements, they are set by hrs and hrs of development and durability running that defines the correct bore profile that minimised piston noise, wear, and blowby. Typically, modern ally blocked engines will be tapper finished (because the top bit of the bore is a lot hotter than the bottom bit of the bore) and the might not even be round, depending on piston expansion kinematics.

I work on lots of high volume engines in current production and have never seen a cylinder bore that is not specified as round and parralel. Some have a different roundness spec at different depths in the bore, this is usualy due to the increased support around the bore once the water jacket finishes on open deck high pressure die cast blocks which resists the honing forces more than the relatively unsupported part of the bore around the water jacket.

Pistons arent round, cylinder bores are.

[Pumaracing]

Max_Torque said:

So tell me, how did you measure the actual bore dimension when the engine was running and under load??

i.e. OE engine dimensions are NOT set by static measurements, they are set by hrs and hrs of development and durability running that defines the correct bore profile that minimised piston noise, wear, and blowby. Typically, modern ally blocked engines will be tapper [sic] finished (because the top bit of the bore is a lot hotter than the bottom bit of the bore) and the might not even be round, depending on piston expansion kinematics.

Blither and nonsense. Bore finishing equipment i.e. abrasive or diamond hones, is designed to achieve bores that are perfectly round and non-tapered. There isn't a honing device ever made AFAIK that can deliberately make a bore out of round to a specified amount not that you'd ever want to and it's damn near impossible to make a bore smaller at the top than the bottom. In fact it's almost certain to be the other way round because the hone can't stroke right through the bottom end of the bore because it'll hit the main journal webs so you tend to get a bit less material removal there.

In fact bores ending up smaller at the bottom than the top is a major PITA with hand honing equipment which I spent years trying to overcome with cut down stones to just work the bottom couple of inches and other shenanigans. Usually I could get bores parallel to within a couple of tenths without undue effort but the occasional one caused problems. Machine honing does a better job here.

For engines with monstrous specific power outputs you can find people (in the USA mainly) who go to extreme lengths like honing blocks that have hot water pumped through them to simulate running conditions and torque plates fitted to simulate cylinder head stresses but no one in their right mind would bother doing that in OE production. It's worth half a percent of potential power output if that. Piston rings happily accept small amounts of taper and ovality and as you say the shape of the bores under operating stresses bears little resemblance to the shape when stationary so it all becomes pretty academic.

Back in the 70s and 80s the Ford Pinto was specified with three grades of OE pistons in increments of a couple of tenths of a thou to best match the bore size. When I got the chance to measure a brand new factory Zetec block some years ago I thought it might be even better than that. I was surprised to find a whole thou difference between the biggest and smallest bore average diameter and in both taper and ovality. I concluded they'd given up bothering about tenths because it makes too little difference to notice.

I'll bet you've never actually honed a bore. Try it sometime and then get back to those of us who have.

[dudleybloke]

Steve_D said:

For infrequent use how about these.

They are spring loaded so you let them expand in the bore then lock them, feel if you are happy with the setting in the same way you would with a set of feelers then remove and measure with your digital vernier. Avoids the hassle of calibrating the other type.

For £18 including the VAT you could try a set and see how you get on with them.

Steve

theyre ok for jobbing use but hopeless for tight tolerance work.

[Yuxi]

Pumaracing said:

- torque plates fitted to simulate cylinder head stresses but no one in their right mind would bother doing that in OE production.

The new 3 cylinder engine in the new Micra has bores that are finish bored and honed with a torque reaction plate, nowadays its all about reducing friction wherever possible, a rounder bore allows rings with a lower tangential load to be used.

Roundness and cylindricity/straightness is taken very seriously in volume production, typical values being 0.008mm for roundness and 0.01 for straightness

[Pumaracing]

I stand corrected Yuxi. Thanks for the info. I didn't know OE production had finally got that concerned about the last few drops of engine efficiency but I guess it's an inexorable trend given the focus on emissions and fuel economy.

[Pumaracing]

stevieturbo said:

I googled and googled and the only place I could see a digital one was eBay. The seller wouldn't offer a brand name, so I just couldn't trust it. I ordered the starret one last night. I envisage the dial gauge being awkward, but it'll be better than nothing.
And I've little doubt my bores could be all shapes.

I'm sure the Starrett will be fine but I'd far rather have the digital Rotagrip that resolves to 0.00005" for £117 inc VAT than an analogue dial gauge tool resolving to a tenth of that and costing £155. Not that I'm saying you need resolution as fine as the Rotagrip or even that it's likely to be repeatable to that but digital stuff is easier to use and more functional.

Also remember that a bore gauge is only a comparator not an absolute measuring device. You still rely on the accuracy of your micrometers to set the bore gauge to nominal bore size first and doing that to better than a couple of tenths is not easy or even likely. It's hard enough taking a direct micrometer O/D measurement of something solid like a metal bar to better than a couple of tenths. It relies on feel and how tight the micrometer ratchet is, how well it's been calibrated etc. Add in the complication of transferring a micrometer setting which has been arrived at without using the ratchet to the bore gauge and then transferring that to the bore and the tolerances mount up even further.

The primary use of the bore gauge is to show up differences in size. i.e. taper and ovality which it can do to very fine limits rather than to indicate absolute size which it can only do as accurately as your micrometer regardless of the resolution of the bore gauge dial.

So I can say with some certainty with my Mercer that one part of a bore is say 1 or 2 tenths bigger than some other part but to say what the absolute diameter is to that level of accuracy is not really possible.

On that basis, and for your limited use, I'd have probably just gone with the cheapest gauge I could find. It'll still probably be at least as accurate as your best mike if the carbide anvils that align it across the bore are accurately positioned. On that topic I do like the design of the current bore gauges which appear to have replaceable anvils. In fact they seem to be rotatable ones so if they wear you can loosen the lock screw and turn them to a fresh spot. On my old Mercer they're an integral part of the measuring head so if they wear too much you're buggered not that mine seem to have done at all. Carbide is pretty extraordinary stuff. However even if they wear the device will still show up bore size variations just as well, it just might not be measuring exactly across a diameter.

For really accurate absolute bore size measurement you use the three legged type gauges which cost a small fortune and have no real place in run of the mill engine building work.

[anonymous-user]

Pumaracing said:

I didn't know OE production had finally got that concerned about the last few drops of engine efficiency but I guess it's an inexorable trend given the focus on emissions and fuel economy.

and that just about sums it up don't it..... When was the last time you designed, developed and production engineered a modern production IC engine???? (and i don't mean some old nail of a zetec etc! lol)

Everything has now become critical in OEM production due to increasing pressures on fuel economy, emissions, NVH, and of course, COST !!


(i have just finished a program for a 2012 series production engine that develops >115kW/litre, and guess what, it has tapered non circular bores..........)


I have a huge amount of respect for the UK's "shed" engineers, working miracles on std engines, tuning them, improving them etc, but for the sake of reality, i need to point out that you guys don't hold all the aces (in fact, in terms of access to stuff like CAD,FEA,CAM,Process developement etc you lot are nowhere!) For example, when did you last modify a plasma spluttered parent metal bore??


If you write on a thread "bloody OEM's they are sh*t at everything" then expect to get some response............ ;-)

[Pumaracing]

Max_Torque said:

If you write on a thread "bloody OEM's they are sh*t at everything" then expect to get some response............ ;-)

If I did write that then I'd expect to get some response but as I didn't......

[stevieturbo]

Impatience always gets the better of me when I order stuff. I wanted to buy the digital, and I'm fully aware it will be far far easier to use, especially for a dummy like myself.

But when I could only find it on ebay, and the seller couldnt give me a brand name. I just thought it safer to opt for a branded product.

It is only for light usage, so no big deal. It will never wear out, that's for sure !

[Yuxi]

Max_Torque said:

(i have just finished a program for a 2012 series production engine that develops >115kW/litre, and guess what, it has tapered non circular bores..........)

Out of interest, who is supplying the production honing machine?

The last one I bought was design for 2 different blocks, it was 2 spindle, variable pitch by CNC, manual tool change, 3 stage process (actualy 2 stage for one block, 3 stage for the other), it also had a crank bore spindle which came in after the cylinder bores were finished came from Nagel but was assembled by Nagel India. The control system was capable enough to make different parts of the bores different diameters but this functionality was present to allow for the affects of head bolt load and the different amount of support around the bores rather than make tapered bores.

I would also be interested to know how muach taper and ovality is required.

Thanks