Hi guys, looks like I may be helping someone with a re-ring job; I'd like to pick up a tool that I could eventually use on my Firebird too! So to check the cylinders for out-of-round & measure the bore, should I buy myself a bore gage? Or would it be better to pick up a set of micrometers and snap gauges instead?

I'm thinking with the bore gauge (looking at a Fowler), I could just raise the gauge up & down in the cylinders to see if/how the gauge moves. But then I was thinking that may not be accurate (depending on how I'm holding the gauge)? Could I use my dial indicator stand to hold the bore gauge steady?

Or I could buy snap gauges and a large micrometer set, but I think I'd have the same trouble with holding the snap gauge "level & straight" in the cyls.

It'd be great if I could buy all three- but my wallet doesn't agree with that.

Thanks!

 

i wonder where Ede is now....
I would just use the micrometers and snap gauges, as i've heard they are more accurate. I agree, trying to move a bore gauge up and down would kill the accuracy since you'd have a tough time keeping your hand perfectly straight up and down.
I actually just want to hear the opinions of the other machinists on here, as i'd like to only buy one set of tools too.

 

I am a toolmaker by trade, and a bore gage will be more accurate in finding an out of round condition, and doesnt require a mic set to use. Most come with an attachment that can be used to get down deep into the bore and allow you to "feel" your way around. Telescoping gages are fine as well, but you have to take about 8 different readings around the bore to pick up an out round condition. There is also the chance of increased error from using two different measuring devices. The best way to check a bore is with a bore gage that picks up the bore in 3 places, these are a bit pricey for the novice however, but will provide the highest degree of accuracy. If the motor is apart already, just send it to a shop, and they will bore and hone it withing .0002" of out of round, and you wont have to worry about a thing. For just a new set of rings, a regular 2 point contact inside mic ( bore gage) will work fine.
----------
You dont have to hold a snap gage straight, its actually the opposite. Pitch the gage at a slight angle, with the thimble a bit on the tight side, then roll the gage upward. This will kind of self center the gage, and give you a consistant reading. Try getting something of a known inside diameter, and practice a bit. Although they are not the most sccurate, you can get nice repeatability from tools such as these.

 

Thanks, Timespy! That's a slick tip about having the snap gauge centering itself; I think I see how it'd work. What about centering a bore gauge? Would I just move it around until I got the "smallest" measurement? Then I'd spin it around a little in the bore, and try to get the "smallest" measurement again? And the diff between those two would be the out-of round?

The Fowler I'm looking at is here: http://www.toolsurge.com/prodView.asp?idproduct=957 There's another one that does a depth of 9" but I think that's overkill for my needs.

I did more 'net searching last night and looks like I'd also need a micrometer, along with the bore gauge, if I wanted to measure the bore's diameter- is that true? From what I understand, I'd set the mic to what the bore size should be (say 4.0), zero out the bore gauge, and then try the bore gauge in the cyl to compare against the 4.0 reading?

 

I've been a machinist for 20+years, the bore gage is the winner here by a long shot, they will self center and most will reach plenty far to measure a cylinder bores, main caps and cam bores, they take some skill to set properly. A gage like this on eBay is plenty good for light automotive use...
http://cgi.ebay.com/2-INCH-TO-6-INCH...QQcmdZViewItem

And a set of micrometers can be had cheap these days too...
http://cgi.ebay.com/0-6-MICROMETER-S...QQcmdZViewItem

These are cheap Chinese tools like the Fowler gage you were looking at but Fowler just gets the same thing and charges twice the price to put it's name on it, but they work "OK" for occasional use, I have Starrett and Mitutoyo tools myself but expect to pay 5 or 10 times the price for quality made in USA or Japan made tools. But they can be found used on e-Bay too with a little looking.

 

Thanks for the info, DartByU- That's two votes for the bore gauge so I think it's the winner! And that's disappointing about the Fowler... the wooden case threw me off! (laughs) I was hoping that it was a mid-range brand. I hate cheap tools but I can't see investing in a top-quality set (like the Starrett/Mitutoyo class) if I'm not using it daily (or even yearly).

Do you think those no-name brands are still accurate? Or are they complete junk?

 

I've used the ones I linked too, they are OK for light use, if your making your living with them you will want to invest in better stuff.

 

With the 3 point contact bore gage, you wont need a mic set. You put the attachment on for the size range you need, and take the readings off the dial. You may set it up like this...range 3.5 4.5. so the min size of the attachment is 3.5, the reading is the 3.5 + whatever you see on the dial. 3.5+ .5025 on the dial would equal 4.0025. check that in a few places, and the difference between the highest and lowest divided by 2 is the out of round condition you have.

 

So that's how it works; cool! Looks like I have a few options now; thanks again guys for all your help!

 

As an update; I went with the 2-point Fowler bore gage (72-646-300) and a 0-6 inch set of no-name micrometers. Now I see how that bore gauge is self-centering; it has a spring-loaded slide with 2 wheels at one side, with the measuring tip poking thru the middle. So it'll get three points right against one cyl wall, and the anvil side will touch the other cylinder wall. Not as cool as a 3-point bore gauge but it'll be enough for what I'm doing!

Two of the no-name micrometers don't quite read zero when closed; if I nudge it a little, they do- but I don't think I'm supposed to do that! (laughs) So I think I have to use one of those wrenches to rotate the whole spindle to line them up with zero. Hopefully they'll be accurate enough for my use!

Thanks again guys!