Bearing measuring

[400bandit]

Hi there, I'm in the slow process of rebuilding an engine. I need to replace main bearings and probably big ends. What should I use to measure them (and the crankshaft journals). I need to be able to measure to 0.001mm but most of the micrometers I see (admittedly on ebay) only measure to 0.01mm. How do I go about measure an internal diameter without spending loads on dial gauges?.

How do you get an accurate measurement using these;

https://cgi.ebay.co.uk/Telescopic-Bore-Gauge-Gauges-Set-6-/290480946874?pt=UK_Measuring_Tools_Levels&hash=item43a2037eba#ht_1399wt_905

I only ask as I don't see how they measure from the from the very edges of the bore (as the edges of the gauges are flat). Am I missing something stupid?

Thanks,

Joe
____________________
Current Bikes 650 Honda Bros, VTR1000 Firestorm // Past Bikes: Sachs Madass 50/110cc - Bandit 400 - FZR750
(+ a XS650 in lots of pieces in my garage and other places...)

[Nexus Icon]

They shouldn't be flat, that's just a trick of the photo. They're very slightly domed at the end of each arm. They work because they're lightly sprung and open up to the internal diameter of the bore. Then you lock them off by twisting the handle and remove them from the hole to measure with a micrometer or vernier caliper.

Personally, the first thing I'd invest in is a decent digital vernier caliper. That would cover most eventualities as they can measure most internal and external dimensions.

[Ichy]

Your going to struggle to measure down to a micron with hand tools. I've just spent £80k on a machine to measure stuff to an accuracy of a micron. Usually you would use something like plastigauge to see how much clearance there is in the existing bearings and buy replacements accordingly. Just check if the journals and big ends should be torqued to a specific value before measuring.

[400bandit]

I've got a set of digital vernier gauges but they only go to 0.01mm and are quite cumbersome. I've heard the way to go is with a micrometer.

Cheers,

Joe.
____________________
Current Bikes 650 Honda Bros, VTR1000 Firestorm // Past Bikes: Sachs Madass 50/110cc - Bandit 400 - FZR750
(+ a XS650 in lots of pieces in my garage and other places...)

[Ichy]

Generally, in industry, a piece of equipment needs to be accurate to 10 times of the measurement range for confidence in the results. To measure down to 0.001mm you need a piece of equipment that measures to 0.0001mm.

[Nexus Icon]

It's all about technique, Joe. a set of 150mm or even 200mm Verniers aren't cumbersome at all and they're plenty accurate for what you'll need.
These would do 90% of what the home mechanic would ever want.

https://www.tooled-up.com/Product.asp?PID=145125

So, if what you have is similar then I can't see why you'd need a mic. Micrometers can't do internal dims without using extras and, if anything, are even more awkward to use accurately for the novice.

[400bandit]

"Range: 150mm (6in)

Resolution: 0.01mm (0.0005in)

Accuracy: 0.02mm"

An accuracy of 0.02mm is not accurate enough to measure things like journal diameter.

Re: Plastigauge, I saw that when flicking through online, seems like useful stuff but it would be no good for measuring my main bearings I'm afraid.

Cheers,

Joe
____________________
Current Bikes 650 Honda Bros, VTR1000 Firestorm // Past Bikes: Sachs Madass 50/110cc - Bandit 400 - FZR750
(+ a XS650 in lots of pieces in my garage and other places...)

[Nexus Icon]

[Nexus Icon]

Although my point still stands about Micrometers. In fact, all of these instruments are only as accurate as the person operating them makes them. A tiny bit of over or under torquing of the wheel will skew the results by more than 10 microns.

[Vincent]

Bore guages are inherently inacurate IMO - 'nuff said.

I use a dti guage for measuring cranks and a new piston ring to measure cylinder bores.