Chicago Brand Micrometers

[Tummler]

Anyone have any hands on experience with Chicago Brand outside micrometers? I have an old 1 in. Starrett that has served me well, but it doesn't have sufficient resolution for my needs, plus I need additional sizes going forward. Intended purpose will be for engine building. This is in the context of a hobby, so frequency of use will be very minimal. As such, they don't necessarily need to be built to stand up to decades of daily use, but they do need to be accurate when used on occasion.

From my past experience, the "value oriented" precision measurement tools are real hit or miss, with some being damn good, with others being junk. Anyone have insight on where Chicago Brand falls on this spectrum?

http://www.chicagobrand.com/outside_micrometers.html

 

[davethorik]

Junk.

Not enough resolution on the Starrett...do you need to hold .0001 tolerances for hobby work?

 

[kd3pc]

Starrett, even an old/vintage one is far better than the stuff sold today.

You do get what you pay for.

Look elsewhere, than the chicago stuff.

 

[Tummler]

Junk.

Not enough resolution on the Starrett...do you need to hold .0001 tolerances for hobby work?

Yes. For example, the ideal main bearing clearance for my next project will be 0.0025 to 0.0028 in. Using a micrometer limited to .001 resolution, while better than plastigauge, still leaves too much margin for error for my taste.

 

[6PTsocket]

Yes. For example, the ideal main bearing clearance for my next project will be 0.0025 to 0.0028 in. Using a micrometer limited to .001 resolution, while better than plastigauge, still leaves too much margin for error for my taste.

Are you saying that your Starrett mic does not have a verneir scale to resolve the .001divisions into .0001divisions? I would like to see a picture or at least a model number. Any mic I have used has that scale.

Sent from my SM-G900V using Tapatalk

 

[Bob-B]

Starrett made many mics with and without "tenths" scales. A "T" in the part/catalog number denotes a tenths scale. I have a few of their 230 1" mics both with and without tenths.

 

[Tummler]

Starrett made many mics with and without "tenths" scales. A "T" in the part/catalog number denotes a tenths scale. I have a few of their 230 1" mics both with and without tenths.

Yeah, it's an old Starrett that I picked up for a couple a bucks at a yard sale. It is very old, but in good shape and produced repeatable readings all day long.

 

[jeeper46]

I'd look on ebay for a good mike

 

[leg17]

You should be able to 'read between the lines' and get within .0002.
Tolerances to .0001 or less require technique as well as equipment.

 

[californiaHank]

What you're trying to do is very very hard. That's a very small clearance. Seems too small for a normal- sized car engine.

You'd better shop for a high end bore gauge as well. The bearings have tolerances, too. Maybe up to plus or minus .00025, which is what you're saying you want for clearance. And crankshafts don't stay perfectly round when they're spinning under load.

 

[davethorik]

What you're trying to do is very very hard. That's a very small clearance. Seems too small for a normal- sized car engine.

You'd better shop for a high end bore gauge as well. The bearings have tolerances, too. Maybe up to plus or minus .00025, which is what you're saying you want for clearance. And crankshafts don't stay perfectly round when they're spinning under load.

That is what I thought as well. In a climate controlled shop holding .0003 can be challenging enough. You can check tolerances like that with a mic, but set it down after every measurement. The warmth from your hand can make the mic expand around .0002.

 

[94_C/1500]

I've got a set of Mitutoyos and they work good. Measure down to tens.

 

[Tummler]

What you're trying to do is very very hard. That's a very small clearance. Seems too small for a normal- sized car engine.

Serious question, how do you think people build well-balanced engines to precise specifications? Plastigauge and otherwise assumimg everything was built exactly to spec?

 

[Firebrick43]

Serious question, how do you think people build well-balanced engines to precise specifications? Plastigauge and otherwise assumimg everything was built exactly to spec?

Define precise? 1/4" is precise to a rough carpenter. .0005 to a toolmaker making test tooling. And anything in between

Really many specs go right out the window after the first heat cycle. You would be amazed how egged shape the crank end of a large Diesel engine gets when you have a CMM that measures in microns. To the field mech with telescoping Gage's everything looks great. Reality is that clearances are large to deal with less than perfect situations. But checking prevents tolerance stack up problems.

If you have to know, buy a name brand mic. Tesa, etalon, Swiss brown and sharpe, mitutoyo, USA brown and sharpe, and starrett.
Quality listed highest to acceptable.

Cheap mics give you a number, but is it correct. You can check it closed and zeroed, you can check it with a one inch standard, but what about in between? Do you have a set of A grade gage blocks that have been certified?. Cheap mics typically can have inconsistent treads per inch down the barrel. The only way to check it is to have a gage lab check it, then you might as well have paid for a good mic that has been done reputably by the factory. I have seen some accurate chinos with mics but have seen many bad ones. All of them have a paper listing specs of what you want to hear.

 

[Adam.C]

Cheap mics give you a number, but is it correct. You can check it closed and zeroed, you can check it with a one inch standard, but what about in between? Do you have a set of A grade gage blocks that have been certified?. Cheap mics typically can have inconsistent treads per inch down the barrel. The only way to check it is to have a gage lab check it, then you might as well have paid for a good mic that has been done reputably by the factory. I have seen some accurate chinos with mics but have seen many bad ones. All of them have a paper listing specs of what you want to hear.

The problem with cheap mics isn't typically the inconsistency of the threads. Its the surface finishes. Just a tiny bit of drag will change the answer. Micrometers are only accurate in skilled hands sensitive to how much force they are applying.

Measuring tenths with any mic accurately takes SKILL. A good mic helps. A cheap mic needs an EXPERT to function acceptably. If you are building engines as a hobby, you need the best tools you can afford, not the absolute cheapest junk on the market.

 

[tombell572]

An annoyance of mine is vendors who peddle cheap tools with names identified with the U.S. such as "Chicago" and "Pittsburgh" that are made offshore.

But to the point, I find that when buying instruments on Ebay, "Starrett" commands a premium because of its name recognition while other fine but defunct and lesser known manufacturers such as Brown and Sharpe and Lufkin tools are a bit cheaper and every bit the equal of Starrett. Tenth-reading mic's and DTI's by these makers are generally available on Ebay or Craig's List.

As everyone above has said--invest in the best you can afford.

Tom B.

 

[BDT/NWMN]

If you are doing a hobby project in your home garage, I would suggest having the machinist who is doing the machine work on the block and crankshaft measure the crankshaft journals and write down the measurements for you. The bearing inserts will have to be installed in the block and the main caps torqued to specifications, and then the bearing bore can be properly measured..... and then compare the two sets of numbers................................... or you can do like most people do.. use plastic-gauge. GM, Ford, or some company "built" that engine.. What you are attempting to do is properly assemble it.... plastic-gauge will be your best bet.... it is done all the time, and has been for decades... keep in mind that there is a proper way to use plastic-gauge, and many people lack the proper skills.

 

[MushCreek]

I'm a toolmaker, and often required to hold ridiculous tolerances. My go-to for round work is a dial micrometer, set with gage blocks. A dial mike has a small dial, typically with a range of +/- .001. You 'zero' it with gage blocks, then take a comparative reading. Spendy, though. I got my 0-1" for $35 at an auction; I don't think anyone knew what it was.