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Short Motor Rebore / Build - Measuring Tools


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#31 mini-mad-mark

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Posted 16 September 2019 - 10:24 PM

 

The set you are looking at has a vernier scale to allow measurement expressed to the nearest 0.0001" (mentioned above by Moke spider)

You will need practice to actually repeatably measure to that nearest 0.0001" (you could say it was 2.7803" according to the mic but whether it actually was 2.7803"?)

 

This is at least the level of accuracy required for pistons, cranks etc

 

Of note  - metric kit gives better resolution as 0.0001" = 0.0025mm but a metric mic can have a resolution of 0.001mm but whether anyone can accurately measure to the nearest 0.001mm with a mic? 0.001mm = 0.00004" or  just about twice the resolution of a 0.0001" reading mic

 

 

Telescopic bore gauges can be relatively cheap and they are only a means to get something the same size as the hole that can then be measured with the micrometer BUT again getting the TBG to the same size as the bore needs practice and then measuring the TBG with the micrometer needs practice - better ones will have harder tips for longevity: 

 

 

I think there might be some confusion about the bore gauging as people might be talking about these:

 

 

What you actually need are some test pieces of known sizes to practice on.....

 

 

Feeler gauges - buy a reputable brand but some are harder than others (for longevity) but hence more brittle so can snap if bent too much so take care

 

 

Cleaning threads - agreed thread chasers or I heard a way was to grind a slot in the thread of a standard new bolt/screw and use that as a chaser?

 

Thanks for the videos. I did work out that Bore Gauges and Telescopic Gauges were different, but it took me a while.

 

With regards to your comment:

 

"Of note  - metric kit gives better resolution as 0.0001" = 0.0025mm but a metric mic can have a resolution of 0.001mm but whether anyone can accurately measure to the nearest 0.001mm with a mic? 0.001mm = 0.00004" or  just about twice the resolution of a 0.0001" reading mic"

 

Should I have bought the Metric set? The same set in Metric has a resolution of 0.01mm. 

Or are you saying I should have bought a Metric set with a resolution? 

 

The metric set with 0.01mm resolution is not good enough you need 0.001mm but as DeadSquare says measuring imperial stuff in imperial is easiest to be consistent with numbers.



#32 mini-mad-mark

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Posted 16 September 2019 - 10:31 PM

:shy:Apologies I should try to keep to minis - this is meant to be a mini forum not a metrology forum (I bet you can find one of those on the interweb!!!)    :proud:



#33 JonnyAlpha

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Posted 19 September 2019 - 07:52 PM

Having trouble trying to find a thread chaser set suitable, so may get a know AF Tap and Die set.

Could anyone tel me the selection of thread sizes so I ensure I get the correct taps. I assume they are all UNF?

Also is it worth getting an engine build but and bolt set, I have seen some for sale for £45?

#34 GraemeC

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Posted 19 September 2019 - 08:09 PM

I have this set:
https://www.amazon.c...23&sr=8-1-fkmr1

Edited by GraemeC, 19 September 2019 - 08:11 PM.


#35 DeadSquare

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Posted 19 September 2019 - 08:35 PM

Having trouble trying to find a thread chaser set suitable, so may get a know AF Tap and Die set.

Could anyone tel me the selection of thread sizes so I ensure I get the correct taps. I assume they are all UNF?

Also is it worth getting an engine build but and bolt set, I have seen some for sale for £45?

 

No, your assumption is incorrect.

 

They are UNC as well as UNF, plus a special 5/8" for the crank and a BSP  for the pressure relief valve.



#36 JonnyAlpha

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Posted 20 September 2019 - 06:41 AM


Having trouble trying to find a thread chaser set suitable, so may get a know AF Tap and Die set.

Could anyone tel me the selection of thread sizes so I ensure I get the correct taps. I assume they are all UNF?

Also is it worth getting an engine build but and bolt set, I have seen some for sale for £45?

No, your assumption is incorrect.

They are UNC as well as UNF, plus a special 5/8" for the crank and a BSP for the pressure relief valve.
One should never assume 🤣
Oh and I remember the Oil Pressure Gauge is a crazy tapered thread!

Anyone list the exact sizes and types so I can ensure I buy the correct chasers

Edited by JonnyAlpha, 20 September 2019 - 06:50 AM.


#37 DeadSquare

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Posted 20 September 2019 - 07:45 AM

Hang on a minute.

 

What makes you assume that any of your threads will be damaged ?

 

In 59 & 1/2 years of playing around with a Mini or two, the only time that I remember damaging a thread, was trying to get the hub out of the top arm of the passenger side of a Mini Pick-up.

 

Most threads, by their very nature, are protected by nestling one inside the other.



#38 JonnyAlpha

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Posted 20 September 2019 - 10:43 AM

Hang on a minute.

 

What makes you assume that any of your threads will be damaged ?

 

In 59 & 1/2 years of playing around with a Mini or two, the only time that I remember damaging a thread, was trying to get the hub out of the top arm of the passenger side of a Mini Pick-up.

 

Most threads, by their very nature, are protected by nestling one inside the other.

 

These two are definitely going to need some attention - maybe drilling and re-tapping?

And I have read that it is good practice to inspect all thread holes and run a tap or chaser through to clean out any debris as part of the cleaning process.



#39 grizzler73

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Posted 20 September 2019 - 10:54 AM

You can make your own thread cleaner (those threads just need a clean up) by getting an old bolt and grinding a groove perpendicular to the threads then winding it in and out with some degreaser.

But the best thing to do is get a machine shop to stick it in there tank.






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