Correct use of a dial indicator

[Dangermouse]

Well I've never used one before. Picked up a pre-loved one the other day for the purposes of measuring endplay and deck heights, a Mitutoyo with 1" range and 0.001" resolution. Like this fellah...



First dumb, newb question - what does this thumbscrew do? Apparently nothing?



I haven't sorted out a magnetic stand for it yet but hope to pick one up soon. When using it to, say, measure endplay, is it a question of sticking the base to the flywheel, pulling back the flywheel, preloading the indicator somewhat against the case, setting the dial to zero and then measuring away?

Gotta be an improvement over my previous, ghetto measuring...

[helowrench]

the thumbscrew usually locks the pointer or dial after you rotate to zero before measurement

Rob

[aircooledtechguy]

Actually, the thumb screw allows you loosen and rotate the outer gauge face so that you can set it to zero once you have the indicator mounted. Once you are ready to pull a measurement, you gently lock the thumb screw so the outer graduations stay in place and only the dial moves; giving you the distance between one position and the other.

[fusername]

what they said.

how to check endplay:
assemble engine far enough to do so (preferably prior to heads and such)
position in TDC
give the crank a whap with a mallet backand forth once to make sure it slides free
push on the gland nut nice and hard to force the crank back as far as possible
stick the mag base of the dial indicator as close to the center of the flywheel as possible
position the end of the dial indicator against the bellhousing of the engine, making sure it is perpendicular to the face
zero the dial by loosening the thumb screw and turning the face of tine indicator till it points to 0 or any good round number
push the crank forwards with your palm on the pully end
record the largest number seen
repeat 12 times till you think you have a consistant number
pull the shims and fight to make it behave and actually give you the clearance you want

remember, no oil on the shims till you are done, it will eat a thou if you oil em

[Dale M.]

We actually use a dial indicator that is mounted to a rod that bolts into belhousing and pointer just touches flywheel face.... It mounts dial indicator more securely and you do not have to deal with a magnetic base which may or may not anchor to flywheel with ease.... Its just one less place to get any extra motion to complicate measurements...

Very similar to ghetto mount pictured above used with feeler gauge but replace bolt towards flywheel with dial indicator...

Dale

[few2many]

I use a harbour freight magnetic dial indicator. Attach to the flywheel and put the dial pointer on the case.

[72 1300]

Would these be ok ????

http://cgi.ebay.co.uk/KENNEDY-LEICESTER ... 3f050033de


http://cgi.ebay.co.uk/Mercer-Dial-Indic ... 1e5fdae0f5

cheers Luke

[few2many]

Normally, You'd probably want mounting hardware to firmly hold it in place. So you dont have to make youre own. Although, as long as they work ok, you could make do.
If you can fab mounts to hold it during measurement, go for it.
If not, buy a new kit, if even from a cheap tool store.

[Dale M.]

Here is a picture "similar" as to how we do it.... But our mount bolts to case (through tranaxle mount thole) and does not use a pair of vice grips ...



More like this...



'Nother concept, but I think I like doing it on flywheel end better...



All you really need to do is know the numbers between the two different readings on Dial Indicator as you move crank (push-pull) back and forth...

Dale

[DWP]

Take a look here for how to read
http://www.stefanelli.eng.br/webpage/en ... lator.html
DWP

[Dale M.]

Take a look here for how to read
http://www.stefanelli.eng.br/webpage/en ... lator.html
DWP

Pretty cool site... Wish more of it was in "English", looks like a neat place to explore....

Dale

[Dangermouse]

And for measuring deck height?

This was the best I could come up with...



The dial indicator obviously found TDC really nicely. I took the measurement pictured, then placed a straight edge across the top of the cylinder (a chisel as it happens...) and measured that, then subtracted the width of the straight edge from the total to give the depth of the gap between top of piston and top of cylinder.

Is there a less contrived method other than buying the correct deck height measuring tool?

[Dale M.]

Actually for deck height dial indicator needs to be mounted through a flat bar... Then bar + indicator is set on flat plate and "zeroed". Once bar + indicator is zeroed it is then placed across cylinder and dial indicator plunger touched piston then you will have a "difference" on dial (other then "0") this difference will be deck height (+/-)...

You need to set up dial indicator just like a "depth micrometer"





Different "application" but exactly same concept (below) base straddling cylinder and plunger on piston top..



As done as in your pictures above, there is to may variable and you have to move indicator from piston top to cylinder rim to get difference and once you move indicator (mount) all reference is lost and any measurement means nothing.... About the best your setup is good for is finding TDC....

Dale

[Dangermouse]

As done as in your pictures above, there is to may variable and you have to move indicator from piston top to cylinder rim to get difference and once you move indicator (mount) all reference is lost and any measurement means nothing.... About the best your setup is good for is finding TDC....

No, I wasn't suggesting that once set the dial indicator gets moved about. I was asking if it could properly be used like this for getting a deck height measurement...

Set piston at TDC and take an initial reading -


Take a nice, inflexible straightedge -


Lay it across the cylinder rim and take another measurement -


Subtract width of straightedge from first measurement -


equals distance from piston top to cylinder top?

[Dale M.]

To complicated, to many numbers, to many chances for error..... But it would work...

Just make single bar that will mount dial indicator (rod at 90° to base) and do away with magnetic base.... Only requirement is bar has to be flat (smooth) and wide enough to span cylinder.

Your way still relies on magnetic base on cylinder stud and whole concept is subject to flex and movement....

Dale