Bore gauges/dial indicators etc.

[2stroke1971]

I am looking to get a better way to measure the bores of the single cylinder motorcycles that I work on. I am talking about the style that has the two rounded balls on one end, and the interchangeable rods for the third point of contact. I see all over good name brands that are sold "without the dial indicator"....I guess that is the most expensive part perhaps. And in the used market---I have seen some good deals where "dial indicator is not included".

On that note, I suppose the indicator itself could be a separate consideration. I read one instance where someone bought a lesser brand bore indicator set from amazon and replaced the included indicator with a quality piece, and he reports consistent measurements. SO that tells me that the indicators can be replaced/swapped out.

I have some decent dial indicators already...I am wondering if I should pull the trigger on a nice Mitutoyo set that doesn't have an indicator, hoping I can make one of my Starrett indicators work on top of it. It is a 511 series Mitutoyo I am looking at. Has anyone had any experience interchanging indicators like this?

Thanks

 

[Ricky Joe]

I have not. I use an old Ames.

 

[2stroke1971]

I am looking to get a better way to measure the bores of the single cylinder motorcycles that I work on. I am talking about the style that has the two rounded balls on one end, and the interchangeable rods for the third point of contact. I see all over good name brands that are sold "without the dial indicator"....I guess that is the most expensive part perhaps. And in the used market---I have seen some good deals where "dial indicator is not included".

On that note, I suppose the indicator itself could be a separate consideration. I read one instance where someone bought a lesser brand bore indicator set from amazon and replaced the included indicator with a quality piece, and he reports consistent measurements. SO that tells me that the indicators can be replaced/swapped out.

I have some decent dial indicators already...I am wondering if I should pull the trigger on a nice Mitutoyo set that doesn't have an indicator, hoping I can make one of my Starrett indicators work on top of it. It is a 511 series Mitutoyo I am looking at. Has anyone had any experience interchanging indicators like this?

Thanks

Replying to myself...I did a little research and it seems that the dials in this case only show movement; you dont get a direct measurement from the dial that is sitting on top of one of these....you wind up measuring this tool with an outside mic anyway. So, any indicator should suffice since the repeatability of my MIC is all I care about....in getting the clearance.
In other words, I wont be pulling a direct meaurement from the bore indicator tool...just setting the zero, and then running the outside mics on the tool until getting back to that zero. Since the same mic is used on my pistons then I should be able to get a reasonable clearance measurement.

I have an old Lufkin inside mic that I have been using and then measuring that with the outside mics, but with only two points of contact (even though its the larger tubular style) its hard to get a repeatable meaurement. The three point tool should be better.

 

[whateg01]

The better way is to use a calibrated ring to dial in the bore gauge. But using an outside mic will do the job.

 

[Steve_P]

I have multiple internal dial bore gauge sets that you measure it with a micrometer like you mentioned. It's far more accurate than a snap gauge, as that's mostly by feel. The internal dial gauge sets are mostly similar so I wouldn't worry about brand too much, just get an accurate set of micrometers. And practice using it- you need to rock it back and forth inside the bore to find the "minimum" reading on the dial where it's perpendicular to the bore.

 

[dnschmidt]

The approach of using a cheaper gauge and a better (in my opinion that mean digital) dial indicator seems like the way to go to me.

I had, and misplaced, (I know the damn thing is somewhere in my house I just don't know where it's at) Johnson Level digital dial bore gauge and the beauty of this was that it kept automatic track of min and max reading. When using a dial bore gauge you want to know the minimum reading as that's the true value. Using an analog dial indicator this isn't very easy to determine as you are trying to measure 0.0001 of an inch and the needle is fluttering all over the place. With a digital it's no different than using a Fluke meter that automatically tells you the maximum voltage, Push the min button and you have your answer.

 

[mogandave]

Am I missing something? Why not get a set of telescoping gauges to measure the diameter with your micrometer(s)?

Aren't the indicator type more for measuring taper and runout and whatnot?

 

[Chris_Hamilton]

A good dial bore gauge is not cheap. Cheap options are not nearly as accurate. The Sunnen dial bore gauge is considered the industry standard. You can find one with fixtures used for about $1K. Like I said not cheap. If accuracy matters that type of gauge is the only way to go. If you are just referencing then the cheaper options would work.

One of the things about using a snap gauge or inside micrometer is that it takes an experienced "feel" to get an accurate measurement. If you know how to use a mic then you probably already have that, but if not it takes time to develop.

This thread may be of interest to you.

dial bore gauge - Don Terrill’s Speed-Talk

www.speed-talk.com

 

[RoninB4]

I've been using indicators for decades as a toolmaker. An indicator is rarely used for a quantitative value due to cosine error, mostly an alignment issue. An indicator is used for a comparative value. When used for target size bore work it's set to "zero" with a ring gauge or a stack of gauge blocks. Yes there is still a cosine error involved but this is minimal enough to not matter. A lot depends upon the tolerance you're working with. If your tolerance is +/- .001 with an indicator that reads to .0001 then the cosine error is fairly negligible. How close to that "zero" you work is also a factor. Consider the error factor to be a percentage of your indicated reading, the farther the deviation from your "zero" the larger the error is. Your pre-set "zero" is the only reading that can be trusted, all deviations from zero are a percentage of that error factor.

I won't go into indicator resolution (based upon order of magnitude) that's another topic. Resolution is NOT the same as accuracy. Accuracy can mostly depend upon the quality of the instrument and current condition. Better quality brands usually gets better accuracy, it used to before outsourcing anyway. Buying used is a **** shoot just like with other things. There are some brands/models of indicators that are really poor designs from brand new that I wouldn't purchase. A digital instrument is NOT inherently superior to an analog instrument. A digital instrument has potential problems unique to an electronic device compared to a mechanical one, they also share some potential problems. A digital device can be considered superior for some things but an indicator isn't one of them. Brand quality means more.

Haven't used a Sunnen indicator not attached to a honing machine but the bore gauges are considered superior to all other types. I don't have one, I've got a Mitutoyo rig I'd like to use some day. I have several tri-lobed micrometers and they also should be set against a ring gauge like any other micrometer. Snap gauges checked against an OD mic have been used for decades, I don't trust them but that's just my personal opinion and lack of technique.

Thermal expansion, cylindricity, taper, and consistency/repeatability are also factors to consider but are topics for a separate discussion. I've been on the podium long enough, hope this helped someone.

 

[dnschmidt]

That's what I like about the digital indicator, it basically eliminates what you're calling the Cosine error if you can lock in the min value as this is the point where the gauge is perpendicular to the cylinder wall.

 

[RoninB4]

That's what I like about the digital indicator, it basically eliminates what you're calling the Cosine error if you can lock in the min value as this is the point where the gauge is perpendicular to the cylinder wall.

-You certainly have a right to an opinion and I can understand what you're saying about alignment correction. You also know the application to use this on better than I would since I'm not there to see it. I also have not seen/used every piece of metrology equipment out there so there may be something in the way of a digital bore gauge. I'd classify such a device as a probe but now I'm delving into nomenclature.

Measuring anything has variables to be considered. Not wanting to be splitting hairs but accurate measurements below +/- .001 is splitting the thickness of a human hair. I still feel that my contention of using an indicator for a comparative value rather than a quantitative value is a "best practice". Can you use an indicator for a quantitative value that can be a trusted reading? I guess that depends on indicator resolution, distance traveled, model accuracy, and how critical the dimension is. You can estimate a reading in .0001's on an indicator with a resolution of .001 but I wouldn't trust it. Same goes for a digital unit that reads to .0005 if I needed +/- .0003. That's more about order of magnitude so perhaps I'm splitting hairs again.

I still don't feel a digital indicator is "better" than an analog type. You can prefer it and that's fine for you. Digital has it's own problems, (particularly with repair) it isn't more accurate than analog, and is often more expensive/bulky than analog. That doesn't sound like "better" to me. This is just an opinion so it's not "The Gospel". Apparently all the makers of quality bore gauges feel that analog is good enough to still offer, even Sunnen. We can agree to disagree and I appreciate you posting.

 

[BillK]

I am looking to get a better way to measure the bores of the single cylinder motorcycles that I work on.

It depends on exactly what you want to do. If all you want to do is measure the basic size then almost any method will work. But if you want to get a good indication of how much wear, taper and out of round there is in a cylinder then you really need a dial bore gauge. You set it with a micrometer or setting fixture and then you can pretty quickly go up and down each cylinder and get a good idea of its condition. You can do the same thing with an inside micrometer, snap gauges etc but it takes forever.

For a hobbyist the ones on E-bay for $100 will probably work fine. I have two Sunnen ones that are probably $1k each now days.

One of mine reads in thousandths (.001") and the other in "tenths" (.0001") To be honest with you I basically never use the "tenths" reading one. It will drive you crazy because of the amount it moves. I bet I can get a cylinder within a couple of tenths with the thousandths one.

Also, I agree with RoninB4 in that you dont want a digital one for this purpose. Its much, much easier to watch a needle move as you sweep up and down a bore than to watch the numbers on a digital gauge.

This one would be perfect for your use:

Pardon Our Interruption

www.summitracing.com

 

[mogandave]

I think cosine error relates to the use of a lever, not whether a gage is mechanical or electronic.

As (I think) bore gages typically use plunger type indicators, I don’t think it would be an issue.

 

[dnschmidt]

The biggest problem with a dial bore gauge is getting it perfectly parallel to the cylinder wall. Finding this value with an analog gauge can be done obviously but it's not as simple as it sounds. With the min feature of a digital indicator, I have a Mitutoyo, this stores the min value and from that you can tell when you are perfectly parallel and do you measurements of out of round and taper from that number. Clearly analog works as Sunnen gauges have been used for a hundred years. Here's how this typically works:

1) You look up what the diameter of the cylinder, connecting rod or whatever should be.
2) You set your 0.0001 micrometer into a micrometer vise and then lock the micrometer to this value.
3) You put whatever attachment you need onto your dial bore gauge to measure in that range and then set your gauge to read zero at the specified value. With an analog gauge you do this by rotating the bezel with a digital you press the zero button.
4) You place the gauge into the cylinder and find the minimum value. This is when the gauge is parallel to the cylinder.
5) The deviation between this "new zero" to the original set by the micrometer zero gives you the out of round, taper and wear from the original size of the cylinder as you move the gauge up and down and around the cylinder.

 

[zmotorsports]

As others mentioned, a telescoping gage (snap gage) can be used as a transfer method of measurement. I've done that with good results but you are right to want a dial bore gage as it is the preferred method for measuring bores, especially cylinder bores.

I have a mid-priced unit packaged by Stef's that I have used for many years now and works well. It came with the dial indicator, which isn't a Starrett or Mitutoyo level, however it is a decent quality dial indicator and although I don't use mine as often as I once did, it has served me well for many years now. Used it just a couple of weeks ago when honing a Jeep 3.8 liter engine in fact. Measure the piston diameter with micrometer, set the bore gage to zero and then measure the bore, easy peezy lemon squeezy.

 

[alfadan]

I'm just a hobbyist, but I think just a telescoping gauge set and outside mics would be just fine and economical. Measure in multiple spots down the bore writing them down with a sharpie, turn 90 degrees and do it again.
They do take great care to measure right, but practice, practice, practice.

 

[BillK]

The biggest problem with a dial bore gauge is getting it perfectly parallel to the cylinder wall. Finding this value with an analog gauge can be done obviously but it's not as simple as it sounds.

Not sure exactly what you mean by this ? You rock the gauge back and forth and when it is at the smallest measurement it darn well should be parallel to the cylinder wall ? With the analog gauge you can sweep up and down the cylinder and around pretty darn quickly and get a good idea as to its condition. You can easily tell if its tapered .001 or .010 with just a glance. I cant imagine doing that with a digital gauge.

Dont get me wrong, I have digital instruments and they have their place but I prefer the analog bore gauge.

 

[vanapplebomb]

Am I missing something? Why not get a set of telescoping gauges to measure the diameter with your micrometer(s)?

For engine cylinder work, telescoping gauges don’t really cut it. I will use them for quick measurements to track progress of my roughing passes, but there usefulness ends there.

Aren't the indicator type more for measuring taper and runout and whatnot?

Yes, which is exactly why you use them for engine work.

For measuring cylinders, you need the repeatability of a proper bore gauge, and ability to watch taper, out of round, etc. my 0.0001” bore gauge tells me a lot more about a cylinder than a T gauge and micrometer can, and far quicker.

 

[solo machinist]

I've been a machinist for 47 years, I second the bore gauge. I use telescoping gauges only when I have to. You gotta have a feel for them.

 

[dnschmidt]

Not sure exactly what you mean by this ? You rock the gauge back and forth and when it is at the smallest measurement it darn well should be parallel to the cylinder wall ? With the analog gauge you can sweep up and down the cylinder and around pretty darn quickly and get a good idea as to its condition. You can easily tell if its tapered .001 or .010 with just a glance. I cant imagine doing that with a digital gauge.

Dont get me wrong, I have digital instruments and they have their place but I prefer the analog bore gauge.

A bore gauge has to go down to 0.0001 of an inch as my Mitutoyo digital does or it's worthless as bearing clearances on modern engines are 0.0015 inch. An analog 0.0001 indicator is moving all around very quickly and determining where it hits true zero might be easy for you but it's not that easy for me. To each his own. I like my way and you like yours.

 

[RoninB4]

I think cosine error relates to the use of a lever, not whether a gage is mechanical or electronic.

-Cosine error is a factor with any measuring device, even a tape measure, it does not matter whether the measuring device is mechanical or electronic. It is most often associated with lever type indicators but not exclusive to them, even a plunger type indicator can be subject to cosine error.

"As (I think) bore gages typically use plunger type indicators, I don’t think it would be an issue."

-Cosine error has nothing to do with what type of indicator is used and everything to do with whether the reading should be trusted as a quantitative or comparative value. Does it really matter? Only as a percentage of the deviation from your "zero" setting, indicator resolution, and indicator accuracy. That's all I've been saying. Everything else is mostly just personal preference.

 

[laser3kw]

I got a tenths indicating Mitutoyo dial bore gauge back when I started to build engines. I come from a machinist background and learned the attitude towards tools as "Precision - you either want it or you don't".
Buy once - cry once.

 

[BillK]

A bore gauge has to go down to 0.0001 of an inch as my Mitutoyo digital does or it's worthless as bearing clearances on modern engines are 0.0015 inch. An analog 0.0001 indicator is moving all around very quickly and determining where it hits true zero might be easy for you but it's not that easy for me. To each his own. I like my way and you like yours.

The original poster was asking about cylinder bore measurements, not bearing clearances. You are correct that something more accurate is needed for bearings but for cylinders a .001" dial type works just fine. And to be perfectly honest with you I still prefer the analog .0001 for bearing clearances. My Sunnen connecting rod hone has a .0001" analog gauge and it is very easy to check size and out of round with it. A digital gauge for that use would drive me crazy

 

[Aileron]

isnt the Sunnen dial bore gauges the gold standard for cylinder and rod end bores?

 

[dnschmidt]

isnt the Sunnen dial bore gauges the gold standard for cylinder and rod end bores?

Yes, it is. But I'm a digital guy and for digital precision instruments Mitutoyo is the best by far. Check out Subi-Performace on YouTube he uses all Mitutoyo digital equipment to build 1000 HP Subaru engines. One slight problem is that his channel is in German.

 

[alfadan]

The original poster was asking about cylinder bore measurements, not bearing clearances. You are correct that something more accurate is needed for bearings but for cylinders a .001" dial type works just fine. And to be perfectly honest with you I still prefer the analog .0001 for bearing clearances. My Sunnen connecting rod hone has a .0001" analog gauge and it is very easy to check size and out of round with it. A digital gauge for that use would drive me crazy

I believe David Richards on Youtube has one and said its the most accurate thing in his shop.

 

[vanapplebomb]

You are correct that something more accurate is needed for bearings but for cylinders a .001" dial type works just fine.

I would strongly advise against this mentality, especially more modern engines.

There was a day when engines regularly ran 0.003 - 0.006 clearance, but those days are long gone. Some more modern engines, particularly those with plated or coated aluminum cylinders, run piston to wall clearance less that 0.0015.

Also, using a 0.001 indicator makes it more difficult to identify taper and out of round. There is no reason a good hone job should be more than 0.0002 tapered top to bottom (if you can go all the way through) or out of round. Your not going to detect that with a 0.001 indicator. I know these numbers sound really small, but nothing starts to chew up rings and ring lands faster than tapered cylinders… and it doesn’t take much.

 

[Aileron]

Yes, it is. But I'm a digital guy and for digital precision instruments Mitutoyo is the best by far. Check out Subi-Performace on YouTube he uses all Mitutoyo digital equipment to build 1000 HP Subaru engines. One slight problem is that his channel is in German.

Lol , I guess that's why mines only 926 hp naturally aspirated. I used a old Sunnen when we built it back in 97.

 

[Steve_P]

My bore gauges have a .0005" mark in between the .001 graduations. It's no problem to interpolate to within ~+/-.0001" as the .0005" spacing is substantial. I can for sure get to within +/- .00015".

All you need to do is rock it back and forth and watch the gauge to get it perpendicular to the cylinder wall to eliminate the "cosine error". It's not that hard to get accuracy that's more than enough to build engines.

The 2-6" set I have looks like the one in Zmotorsports pics, but mine is in a wooden box and was from Enco.

I know this is GJ, but this is not that big of a deal to learn how to do this, and you don't need to spend thousands of $ on the best measuring equipment to build engines.

 

[vanapplebomb]

I am definitely a budget tool buyer. You can definitely get repeatable tools for reasonable prices. I have a Fowler 1.4 - 6 inch, 0.0001 bore gage new for around 200. Works great.