Measuring Cylinder Bore Diameter

[Mad Professor]

Yes absolutely right and well said mate, I wanted to get one, but really you need a few to get a range of measurements, then you should buy gauge blocks to test their accuracy periodically. Then you get into temp fluctuation. How far into the rabbit warren do you go. Thus my desire to stick with verniers But no, you are absolutely right, micrometers will read to .001 and better.

I learned a lot about this when I rebuilding a small block chevy engine years ago. To check rod and main bearing clearances, they sell stuff called plasti-gauge. You put a strip of the material on the bearing, install the parts to torque, then the amount the plastic squishes out gives you a crude clearance. I was not happy doing things that crudely.

My uncle was one of the master machinists at General Electric areo-space back when they made the guidance parts for ballistic missiles. They had the best measuring equipment that could be purchased, along with gauge blocks, and temperature controlled rooms where they stored the equipment and brought the parts in to be measured. He snuck out a complete set of mics and snap gauges in his lunch box, for me to work on my car. They weren't the best they had, but best as what a decent machine shop would have. It took me quite a while to fit all the rod and main bearings, and pistons.

I got the engine rebuilt and he snuck the tools back into the shop.

 

[Mad Professor]

Hey mate, I’m literally just trying to learn new skills honestly. i like the challenge I guess, or maybe it just satisfies my OCD? These snap gauges have been pissing me off since I got them, until recently since figuring out a few little changes to what I was doing.

An analogy. I use to teach chemistry students. They had to learn to use various analytic equipment (balances, volumetrics, etc...)

I'd ask them " does anyone already know how to use this equipment?" Some hands would raise. Then I'd ask, "do you know how to use it correctly?"

 

[Vintage Engine Repairs]

I learned a lot about this when I rebuilding a small block chevy engine years ago. To check rod and main bearing clearances, they sell stuff called plasti-gauge. You put a strip of the material on the bearing, install the parts to torque, then the amount the plastic squishes out gives you a crude clearance. I was not happy doing things that crudely.

My uncle was one of the master machinists at General Electric areo-space back when they made the guidance parts for ballistic missiles. They had the best measuring equipment that could be purchased, along with gauge blocks, and temperature controlled rooms where they stored the equipment and brought the parts in to be measured. He snuck out a complete set of mics and snap gauges in his lunch box, for me to work on my car. They weren't the best they had, but beat as what a decent machine shop would have. It took me quite a while to fit all the rod and main bearings, and pistons.

I got the engine rebuilt and he snuck the tools back into the shop.

That’s insane, what an amazing contact to have and I’ll pm you to find out more about your mechanical background. I would absolutely love to learn from guys who build and race custom engines, it would be the most amazing experience even if I had to start with cleaning the toilets, I wouldn’t care. I went to the drag strip the other week for the finals but also got a pass to get into the pits so I could chat to the mechanics

Here are some short clips
Of that day





And lastly door slammers, I have never experienced anything quite like the sound and power of those things.. 5.7 seconds 1/4 mile and 412kph

 

[Canyon Angler]

Yeah, my dad was a mech engr, and he told me about something they were measuring in a factory that had to be dead--nuts "on" and they had to measure it by peering through a telescope, lest the heat radiating from your body change the sizes/configurations of the things being measured...is Schroedinger's cat dead or alive?

It's a bottomless rabbit hole and past a certain point becomes pointless. How many Angstroms of slop are allowed in the track for a bulldozer?

 

[Vintage Engine Repairs]

I guess in summary as to why I’m learning something (even though I don’t have the right tools, equipment or skill) that’s probably completely irrelevant to chainsaw engines is that one day I hope to be able to put these skills I’m trying to learn now, into practise on engines that really require it and glean what I can. I don’t know, maybe it’s all a big waste of time honestly.

 

[Canyon Angler]

I guess in summary as to why I’m learning something (even though I don’t have the right tools, equipment or skill) that’s probably completely irrelevant to chainsaw engines is that one day I hope to be able to put these skills I’m trying to learn now, into practise on engines that really require it and glean what I can. I don’t know, maybe it’s all a big waste of time honestly.

Hey, more power to you! I enjoy that kind of stuff too. But in my own case, I need to keep the OCD in check or wind up chasing my tail over non-issues.

 

[Vintage Engine Repairs]

Hey, more power to you! I enjoy that kind of stuff too. But in my own case, I need to keep the OCD in check or wind up chasing my tail over non-issues.

Thanks mate I appreciate you saying so. I guess that’s exactly what I’m doing right now because you are absolutely right, all of this is just “fluff” and pointless in real world chainsaw use. I guess I just hope these skills will be transferable with hobbies / jobs / my passions in the future

 

[Mad Professor]

I guess in summary as to why I’m learning something (even though I don’t have the right tools, equipment or skill) that’s probably completely irrelevant to chainsaw engines is that one day I hope to be able to put these skills I’m trying to learn now, into practise on engines that really require it and glean what I can. I don’t know, maybe it’s all a big waste of time honestly.

You have certainly learned quickly on chainsaws and lots of the tools you've acquired will be useful for other work. I like the fact that you fix things the right way, rather than the quick way.

I started out as a child fixing lawnmowers, and lawnmower engines that powered our "mini-bikes". All my tools fit in a small toolbox. From there it was: farm equipment, dirt bikes, and trucks and cars we paid nearly nothing for. The tool boxes multiplied and many years later there are still tools I wish I had.

 

[ericm979]

What you need is a bore gauge. I find that easier get consistent results from than the snap gauges. They're not that expensive. This one costs about what I paid for mine 30 years ago: https://www.penntoolco.com/fowler-xtender-2-to-6-bore-gage-set-w-carbide-anvils-52-646-300 Of course you'll want a smaller one for saw work and that might cost a little more.

Someone up thread mentioned measuring new parts. That's a good idea. I have found some that were mis marked from the factory. That was motorcycle parts, you can imagine that cheaper saw parts would not be handled as carefully.

 

[Vintage Engine Repairs]

You have certainly learned quickly on chainsaws and lots of the tools you've acquired will be useful for other work. I like the fact that you fix things the right way, rather than the quick way.

I started out as a child fixing lawnmowers, and lawnmower engines that powered our "mini-bikes". All my tools fit in a small toolbox. From there it was: farm equipment, dirt bikes, and trucks and cars we paid nearly nothing for. The tool boxes multiplied and many years later there are still tools I wish I had.

Thank you I really appreciate that. Sometimes I’m so caught up wanting to learn the next thing / challenge I forget just how much I have been able to learn from you guys on here and put into practise on the saws I have, and for that I’m so appreciative.
That’s an awesome way to learn and build up experience you have, nice!

 

[Vintage Engine Repairs]

What you need is a bore gauge. I find that easier get consistent results from than the snap gauges. They're not that expensive. This one costs about what I paid for mine 30 years ago: https://www.penntoolco.com/fowler-xtender-2-to-6-bore-gage-set-w-carbide-anvils-52-646-300 Of course you'll want a smaller one for saw work and that might cost a little more.

Someone up thread mentioned measuring new parts. That's a good idea. I have found some that were mis marked from the factory. That was motorcycle parts, you can imagine that cheaper saw parts would not be handled as carefully.

That’s an awesome tool and very reasonably priced! Let me see what I can get here in Australia. I’ll be back shortly. Thank you!

 

[sean donato]

What you need is a bore gauge. I find that easier get consistent results from than the snap gauges. They're not that expensive. This one costs about what I paid for mine 30 years ago: https://www.penntoolco.com/fowler-xtender-2-to-6-bore-gage-set-w-carbide-anvils-52-646-300 Of course you'll want a smaller one for saw work and that might cost a little more.

Someone up thread mentioned measuring new parts. That's a good idea. I have found some that were mis marked from the factory. That was motorcycle parts, you can imagine that cheaper saw parts would not be handled as carefully.

Been using bore gauge for years now. It's all we were allowed to use at the machine shop. They can be deadly accurate if set up properly. Wouldn't ever go back to a snap gauge.

 

[Vintage Engine Repairs]

Been using bore gauge for years now. It's all we were allowed to use at the machine shop. They can be deadly accurate if set up properly. Wouldn't ever go back to a snap gauge.

Thanks for sharing your experience Sean, would this suffice ? 35-60mm essentially it will measure everything from an ms 170 to an 880 (or under slightly because the 880 is 60mm dia cylinder)

https://generaltools.com.au/product/accud-dial-bore-gauge-35-60mm/
Or would you say buy once and cry once and get a larger set?

https://www.paengineeringsupplies.com.au/product/dial-bore-gauge-set-18-160mm-10mmx0-01-indicator/
I want something that will be considered acceptable for future ventures within mechanics too.

 

[lone wolf]

Thanks for sharing your experience Sean, would this suffice ? 35-60mm essentially it will measure everything from an ms 170 to an 880 (or under slightly because the 880 is 60mm dia cylinder)

https://generaltools.com.au/product/accud-dial-bore-gauge-35-60mm/
Or would you say buy once and cry once and get a larger set?

https://www.paengineeringsupplies.com.au/product/dial-bore-gauge-set-18-160mm-10mmx0-01-indicator/
I want something that will be considered acceptable for future ventures within mechanics too.

I dont know about the expensive one based on as little as you might use it.

 

[Vintage Engine Repairs]

I dont know about the expensive one based on as little as you might use it.

Yes very well said Lone wolf.

 

[Vintage Engine Repairs]

So are snap gauges not relied upon within mechanics generally? Too much room for user error?

 

[lone wolf]

Yes very well said Lone wolf.

I have the one that was first posted for you from another member it works good but I don't use it much . You may not need this item.

 

[Vintage Engine Repairs]

I got them out again to try different objects with really good consistency, but I can see why a bore dial gauge is far superior..

 

[Ted Jenkins]

I think the focus point here has been lost. Two stroke pistons and cylinders are not high tech stuff. As far as performance of engines chainsaws are at the bottom. The chromium plating on a typical cylinder is very thin two to eight thousandth with some exceptions. If the plating is good the cylinder is fine and not out of tolerance. The factory specs On my Ford 460 CI stated if the taper is 9 thousand or less it is in factory specs but I would prefer less. I have a bore gauge that is very precise and expensive but never use and not even sure where it is. If you want to know accurately a bore stick a new or used ring in the bore then square it up with a piston and put your feeler gauge to see what it is then move it to see the difference. Or stick a piston in the bore with a feeler gauge and you will know what needs to be done. Thanks

 

[Ted Jenkins]

I got them out again to try different objects with really good consistency, but I can see why a bore dial gauge is far superior..

Bore gauges are not a great tool in that it takes pretty good skill to come up with the exact same measurement every time, ask me how I know. Thanks