Homemade measuring tool inner diameter

[minh-thanh]

Hi All !
My homemade measuring tool inner diameter
It's cheap and okay with me
Unable to upload images, although I have reduced the size

https://drive.google.com/open?id=1gPbecMYe8PVKG01tk7bHgvSE-_uf9ILR

 

[tornitore45]

Do not understand how it works.

 

[minh-thanh]

tornitore45 !

When I need to measure the bore diameter, I put the tool into the bore and I adjust the bolt 1, the number 2 will come out and come in contact with the cylinder wall, then I take it out and measure it again with my caliper

 

[tornitore45]

Got it. Was the spring that threw me off.

 

[BaronJ]

Interesting concept !

The reason that I went with three balls is the self centering. Two certainly makes construction simpler.

 

[ajoeiam]

Interesting concept !

The reason that I went with three balls is the self centering. Two certainly makes construction simpler.

Agreed - - - - construction MUCH simpler.

Except with only 2 balls you're right back at the 'feel' problem.

It is so very very easy to be a small distance off of the 'exact' centerline.
That distance will result in a dia measurement error.
Generally not a problem if you're only working to +/- 0.002" (0.05mm) but if you're doing things like cylinder bores or even more so on injection pump bores
you rather should be working to tighter tolerance - - - just imo though.

 

[Gordon]

So how do you measure the diameter with three contact points? You said with a caliper but a caliper will not measure over three points.

 

[BaronJ]

Hi Gordon, Guys,

This thread is getting confusing, because there is another thread where bore measuring is also being discussed.

https://www.homemodelenginemachinist.com/threads/bore-gauge.35663/page-3
If I can refer you to that thread.

Thanks.

 

[ajoeiam]

So how do you measure the diameter with three contact points? You said with a caliper but a caliper will not measure over three points.

If that question was for me - - - well - - - you just don't measure using a caliper.
At this level its micrometers only.

It is possible to measure but you need to measure more than just one measurement AND use some trigonometry so its not for everyone.