Micrometer and Bore Gauge recommendations

[SturdyHSV]

Will be building an engine, recommended way to check bearing clearances is with an outside micrometer and a bore gauge.

Due to the crank size I'll need a 50 - 75mm micrometer. The septics obviously do everything in inches so again recommendation is that it'll read down to 0.0001 of an inch. 0.01mm doesn't quite feel close enough to that, thoughts? As this seems decent enough otherwise:

https://www.amazon.co.uk/dp/B003UATB84/

I can use the micrometer to ensure the dial gauge is accurate so was assuming something like this would be fine:

https://www.amazon.co.uk/dp/B004NOL95O/

I'm not looking to spend £600 on something I'll use a few times, ideally say up to £100, obviously looking to avoid shoddy tat though

Any recommendations appreciated

[Sanchez89]

The micrometer gets a thumbs up from me. Mitutoyo are a great choice for measuring equipment. The dial gauge I cannot vouch for, not sure who would have manufactured it. Do mitutoyo not do an expanding set where you have to measure it afterwards? Maybe slightly better quality than the draper?

The mic will read to 0.005mm normally.

[GreenV8S]

A telescopic gauge plus micrometer would be a better way to measure bore IMO.

[SturdyHSV]

GreenV8S said:

A telescopic gauge plus micrometer would be a better way to measure bore IMO.

I like the sound of that, presumably could get something relatively simple in terms of telescopic gauge and a decent micrometer to then measure that...

First thing to appear:

https://www.amazon.co.uk/Silverline-675092-Telesco...

[SturdyHSV]

Looks like need to go digital to get better than 0.01mm reading (I know I could guess between the 0.01mm gradiations, but I'd really like to do this properly...)

https://www.machine-dro.co.uk/50-75mm-2-3-digital-...

£250 then eh? Anyone with a better alternative? Some of the cheaper digital stuff has a precision of 0.001mm but an accuracy of +/- 0.04mm, which seems hilarious

EDIT:

Have found it for £229 here

https://www.hroberts-di.com/micrometers-c11/mituto...

Edited by SturdyHSV on Thursday 8th October 14:42

[harrycovert]

I have a set of telescopic gauges but find it difficult to get a consistent reading, you need to keep repeating the measurement several times until you get the same reading

[SturdyHSV]

harrycovert said:

I have a set of telescopic gauges but find it difficult to get a consistent reading, you need to keep repeating the measurement several times until you get the same reading

Yeah I'll be doing it a fair few times and in at least 3 or 4 different places to try and get something consistent that I'm happy with. I have some bits of 2.5" and 3" (outside) diameter exhaust around to practice using them on in the mean time which will be helpful

[GreenV8S]

SturdyHSV said:

I like the sound of that, presumably could get something relatively simple in terms of telescopic gauge and a decent micrometer to then measure that...

That's exactly the sort of thing I had in mind. Doesn't need to be anything fancy - it's the micrometer that does the work.

[Evoluzione]

Use Plastigauge.

[SturdyHSV]

Evoluzione said:

Use Plastigauge.

I appreciate the suggestion and I know it's used a lot, but I just wouldn't feel confident trusting some squishy plastic. I'd rather buy the proper tool and take the time to use it properly.

I want to take every precaution I can in trying to build a reliable 600hp+ engine, and squishy plastic and a paper ruler just wouldn't satisfy my concerns.

[Andy RV]

See if you can find a suitable Tesa internal mic on eBay. Ideally one with a ring gauge for calibration.

When your dealing with +\- 5 microns with a mic a lot comes down to feel so take some time practicing. Make sure your moving the mic to feel for the high spot.