Measuring internal diameters

[routercnc]

Thanks everyone, very informative.

I asked around at work as well and they gave similar responses:
The budget/entry telescopic ones are not that nice to use unless they are high end such as Mitutoyo which are much smoother
Three point internal mics are great but expensive
Verniers were not favoured in general (nick named Very-nears)
Two point internal mics were reasonable (as per 1st photo)

But critically, and as you mention Boyan, even with reasonable tools it comes down to the operator and the feel of the gauge when taking the measurement. This is something only experience can give - i.e. when the interference fit part just falls off under gravity you know your method needs a bit of work. I'm sure I can dial myself in as per all the other tools I've got.

In all I'm homing in on the 2 point internal mic. Reasonable price, just one measurement to take, seen them used a bit (Youtube etc.) to make good parts. Maybe one for the Christmas list . . .

Thanks again

[Lee Roberts]

Thanks everyone, very informative.

I asked around at work as well and they gave similar responses:
The budget/entry telescopic ones are not that nice to use unless they are high end such as Mitutoyo which are much smoother
Three point internal mics are great but expensive
Verniers were not favoured in general (nick named Very-nears)
Two point internal mics were reasonable (as per 1st photo)

But critically, and as you mention Boyan, even with reasonable tools it comes down to the operator and the feel of the gauge when taking the measurement. This is something only experience can give - i.e. when the interference fit part just falls off under gravity you know your method needs a bit of work. I'm sure I can dial myself in as per all the other tools I've got.

In all I'm homing in on the 2 point internal mic. Reasonable price, just one measurement to take, seen them used a bit (Youtube etc.) to make good parts. Maybe one for the Christmas list . . .

Thanks again

Before you do that:

All the boys I watch on YouTube...

Use the telescopic ones to get them close, an external mic to measure the scope and get them even closer...

Then! they use there own skill to find a piston fit "pop" :)

It's normally in the flavour of Starrett though on the scopes, so yeah they do operate nicely, I can't see that a cheaper set would give you that much of an off reading that you couldn't recover from it using your learned skill on the last op.

[mekanik]

Before you spend a lot of cash try using internal calipers, i used to work as a Mechanical Inspector in a Machine Shop and used these a lot, it takes some practice but you can get a good reading.
Regards
Mike

[routercnc]

Cheers Mike, Lee, Komatias

The guy I've been watching a lot recently is Stefan Gotteswinter and he likes to use the internal mic. But yes many others use the telescopic gauges and then mic them.

In the work discussion calipers were mentioned as a very cheap way to measure bores (I already have the external mic), but takes some feel/practice. I forgot to mention that above so thanks Mike. Great to hear you worked in the inspection area - that's what I like about this forum, such a wealth of experience to tap into. So I'll most likely get an internal caliper anyway and have a play - not that expensive.

Dial bore gauges look interesting, one to think about.

I'll sleep on it and bit more . . . .

[mekanik]

Dial bore mic's are expensive and you still have to check them with gauge so in all honesty i don't think its a very good investment unless you pick up something cheap on ebay.
with spring loaded internal calipers you can get a good feel ( polish the tips to form a nice ball end) and as long as you duplicate the same touch when brushing the anvils of your external mic you will get a good reading.
Good luck
Mike

[magicniner]

When I found these I thought of this thread



;-)
You can pick up sets of Diatest Gauges for reasonable money on ebay from time to time, they are very quick and easy to set up as you slip the assembled gauge into the standard and set the dial gauge in the sleeve to read the exact size, repeatability is fantastic and you can check the bore at various depths if necessary, I use them for assessing chamber wear in barrels.
To swap to metric you just use a metric dial guage and a calculator to convert the standard size to metric for zeroing,
- Nick

[routercnc]

Cheers Nick,

Another one into the mix . . .