Picture of Measure Cylinder Wear without a Micrometer
I gathered some junk lawnmower parts to build a go-kart for my kids.  The engine needed new rings, but was the cylinder worn in an egg-shaped pattern, or did it simply need slightly over-sized rings?  I did not have a micrometer for measuring inside the cylinder walls.  I improvised.

(I do not have an engine to show in this Instructable, and have decided to use a holesaw to represent an engine cylinder.  The bottom of the holesaw represents the top of the piston.)

Step 1: Measure the cyclinder's diameter

Picture of Measure the cyclinder's diameter
My substitute micrometer uses a wood block 3/4 x 3/4 inch cut in length to the diameter of the cylinder.
crazypj1 year ago
What a brilliant idea, I wish I had thought of it
I have cylinder bore gauge but this would be great for people who only ever rebuild 1 or 2 engines
Phil B (author)  crazypj1 year ago
Thank you.
itchman4 years ago
If there's a Harbor Freight where you live can get dial indicator w/clamp stand for $29.99.Got one to check brake rotor run out.Can't beat it!
Phil B (author)  itchman4 years ago
There is indeed a Harbor Freight store nearby now. Someone else made the same suggestion. However, I believe I mentioned I came up with this about 30 years ago long before I had ever seen a Harbor Freight store.
I for one think the idea is great! I have been looking for just such an item, also if for any reason the guage is off just a little bit It wont matter if you use the same device and method to measure any parts that your going to replace! How ever on engine cylinders where you have preset specs to go by it is nice to have an device that will give the precise measurments like which can be converted or are the same as store bought guages, again thanks this is a great idea!
Phil B (author)  tazmaniac_377525 years ago
Thank you.  It has been a long time since I put new rings into the engine for a go-kart, but I think the cylinder was to be out of round no more than .080 of an inch.  Although this device does not give an absolute measurement (e.g. diameter = 3.8 inches), it did tell me how many thousandths of an inch difference there were between the highest and lowest measurements.  I hope this idea serves you well.
thanks for posting this. im going to rebuild my engine soon so this should be helpful
Phil B (author)  unaffiliatedperson5 years ago
Thank you.  Naturally, it will not tell you the diameter of the cylinder, but it will tell you how much variance in diameter there is.  I used this about 1980.  I had a Chilton manual with a step-by-step section on rebuilding engines.  This device allowed me to know how much out of round the cylinder on my old lawnmower engine was.  It worked quite well.
NachoMahma5 years ago
.  Great idea. Great job.
.  I don't think using the hole saw is a problem. If one has need of your gadget, one should be able to get the idea with ease.
Phil B (author)  NachoMahma5 years ago
Thank you.  You seem to be correct.  Folks are understanding the concept just fine.
chopperdr5 years ago
i love this ible, and im an aircraft mechanic, and i have used profesionaly made gauges like this ont that a shop i worked for a few years back had bought, (you dont want to know the price of them) but these look very similar, and will do the job just fine, so dont worry about people like sypher12616says, they will probably never undersyand the need of a habdmade item like this., but it is a grat ible and i need to go look at your others now ;-)
Phil B (author)  chopperdr5 years ago
Thank you for your support.  This little substitute micrometer should be quite accurate.  The user needs to move it side to side just a little to make certain a measurement is being made at exactly the widest part of the cylinder.  As long as care is taken to find the maximum thickness of feeler gauge blades that will pass between the inside ends of the steel rods, there is very little possibility of operator error.  Feeler gauges are either "go" or "no go" and are accurate to within a couple of thousandths of an inch, probably even closer tolerances yet.   
Beest9215 years ago
Hey Phil, don't listen to that guy! There are times when you're caught in a pinch and you have to improvise. My nearest Harbor Freight store is an hour and a half away, so I don't get there much. I've been wrenching on cars and tinkering since I was 10 years old and I'm 45 now. When I was growing up, our family didn't have much money and there was no Harbor Freight, so If I wanted or needed something, I made it. Now I have money but I still make tools. I'm an automotive restoration technician by trade and have MANY tools, but I still make new ones on a weekly basis because "I need it in a pinch". This instructable, I wouldn't use it on an 8 second drag car, but for a lawn mower or go-cart engine, it's perfectly fine. I would use a hardwood like oak or maple though.Nice instructable and I'm going to check out your other ones!
Phil B (author)  Beest9215 years ago
Thank you.  This is pretty much a one use tool, unless you will rebuild several engines with the same cylinder dimensions.  For that reason, cheap wood rather than good hardwood does fine. 
l8nite5 years ago
this is a really great idea !
Phil B (author)  l8nite5 years ago
Thank you.  It worked well for me.  I would not care to do measurements on a V-8 by this method, but it was fine for a one lung engine.  I wish I had an actual engine to use in the photos, but the hole saw made a decent substitute.
l8nite Phil B5 years ago
well, a dial indicator would be nice but if you didn't have access to one this could tell you if you needed to go find one
Phil B (author)  l8nite5 years ago
As it happened, this fix told me the wear on the engine (old cast iron block) was within tolerances and all I needed to do was install oversize rings.  A dial indicator was out of my price range in those days, and I did not know anyone who had a dial indicator. 
rimar20005 years ago
I see a clever instructable, and it had to be from Phil B!

Almost all yours works are very interesting, Phil.
Phil B (author)  rimar20005 years ago
Thank you, Osvaldo.