Bearing scratches from dial bore gauge

[AC sports]

This question may sound a bit amateurish but I've noticed every time I measure a main or rod bore with bearing shells fitted, I manage to leave small marks where the anvil and guide legs of the dial bore gauge touch the bearing shell.
Am I missing something?

[hoodeng]

You should not be getting marks from the centering contacts or measuring anvil as this end of the bore gauge is stationary when checking ,and its the interchangeable anvil end that does the arc , when checking set the gauge so there is minimal gauge deflection , a couple of thousandths is plenty, less is better ,also oil the bore being checked ,for bores that i regularly check i have made anvil spacers that give me very close to what the bore is.I also compress the measuring end down onto the centering contacts when inserting to keep contact prints to a minimum.

The interchangeable anvils are consumable items ,when the contact pin starts to mark up ,bin it ,they are cheap, i would like a dollar for every bore the one in the picture has been in ,it was replaced when i was picking up a minor bore measurement variation many years ago when the pin was rotated into different locations under the nut.mind you that pin is not marked up ,it's r##ted.

This seems to work for me.

Cheers.

[Charliesauto]

This question may sound a bit amateurish but I've noticed every time I measure a main or rod bore with bearing shells fitted, I manage to leave small marks where the anvil and guide legs of the dial bore gauge touch the bearing shell.
Am I missing something?

What type of bore gauge are you using?


We use Sunnen GR-2000 series gauges for this, the GR gauge is retractable and has a feature that allows you to adjust the spring load.

They are pricey, but if you do a lot of this type work, well worth the money. Even with this type gauge we see cosmetic marks in the bearings, nothing to objectionable. Coated bearings barely show any marks from the gauge.

[AC sports]

Suggestions taken.
I know this one's going to cause controversy. .....does anyone try polishing the marks ?
Or just leave them. I can actually feel the marks with my finger nail on a couple.
My anvils are polished. Bores lightly oiled. Low spring tension on the guides. These bearings seem quite soft.
I know some gauges have retractable guides. I don't have that luxury I'm afraid.

[Old School]

Suggestions taken.
I know this one's going to cause controversy. .....does anyone try polishing the marks ?
Or just leave them. I can actually feel the marks with my finger nail on a couple.
My anvils are polished. Bores lightly oiled. Low spring tension on the guides. These bearings seem quite soft.
I know some gauges have retractable guides. I don't have that luxury I'm afraid.

Leave the marks, they will not hurt anything. The old TRW/Clevite "P" bearings come to mind. They were very soft, enbedable, and marked very easily. Back in the day we did not have "H" bearings or any "race" bearings. After running the old "P" bearings for a season drag racing we would refresh the engine and the bearings would look like they did when installed, dial bore gauge marks and all.

[4vpc]

Isn't this what Plastigauge is for?

[racear2865]

Well I guess Im different. I put .001 feeler stock at top and bottom where gage is going to ride. Main reason is, if it leaves a mark, it imbedded in the bearing and the measurement is NO longer correct. By using the feeler stock, it will not imbed. Just a thought
reed

[PackardV8]

Yes, it bugs everyone that it's almost impossible to measure bearing ID with a dial bore gauge without leaving trace marks.

Yes, agree the marks don't do any harm.

Slightly OT, but when was the most recent time anyone measured the block main bore ID to the desired spec, inserted bearing shells marked and numbered for that application, measured again and got an off-spec result? Even the white box Made-in-Taiwan bearings we have to use for some obsolete engines are dead on spec these days. Of course, shit can happen; that's why we measure everything at each stage of assembly.

[Schurkey]

We use Sunnen GR-2000 series gauges for this, the GR gauge is retractable and has a feature that allows you to adjust the spring load.

Too-stiff spring is the first thing I'd be looking at.

I put .001 feeler stock at top and bottom where gage is going to ride. Main reason is, if it leaves a mark, it imbedded in the bearing and the measurement is NO longer correct. By using the feeler stock, it will not imbed. Just a thought.

I never considered that--but it seems obvious now that someone has pointed it out.

[hoodeng]

Plastiguage is great for giving a net bearing clearance ,but if you are looking for ovality and true a bore gauge is probably the tool most ready at hand to identify these conditions . I would love one of the Sunnen GA or GR with retractable centralizers but its a bit above my pay rate, ill have to stick with the good ole Mitutoyo's and Mercer's that live on the shelf here.

Cheers,

[modok]

Some dial bore gauges have a lever that retracts the wheels and measuring point. if I want to not leave any marks i use this type. I have also considered modifying the very common mitsu-knock offs to reduce the spring pressure, make the spring pressure adjustable, or add a the retracting lever, or use larger radius measuring points......I mean, why not? you can get those things very cheap. But I don't need any more hobbies at this time.

BTW if it is leaving a mark......you need to subtract the depth of the mark, which might be .0002 or it might be ,0005, but it isn't zero.
For the home gamer I might recommend a VERY nice set of snap gauges with large radius ends. if you can get the hang of using those with minimal pressure...... then the measurements may actually be more accurate on soft materials.
however snap gauges are not ideal for measuring all around and finding the true shape of a hole.

[Keith Morganstein]

The newer Mitutoyo dial bore gauges use lighter pressure and are more accurate. They improved them in about 2010. They have about half the pressure of the knock-offs.

There is a Mitutoyo thats good for bearings, the 545-135, it has large radius fingers and doesn’t make marks. That model is discontinued. Its copied from the Standard brand dial bore gauge.