# Gage blocks...What are the differences?



## HMF (Sep 27, 2011)

So I realize that, to check measurements, I will need a set of gage blocks?

I see there are different grades, 1, 2, 3, class A, B

What do these grades and classes mean and what exactly are the differences?

Thanks,


Nelson


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## Tony Wells (Sep 27, 2011)

As a general statement, those are categories of accuracy. There has been some changes in the naming convention for blocks, and I don't believe the letter grades are being produced now. 

From Starrett's Webber division:

The B89.1.9 standard became effective in July, 2002.  On January 6, 2003, Webber began to sell gage blocks to the new 
B89.1.9-2002 standard. The Federal standard, GGG-G-15C, has been withdrawn. 


So, the B89 standard is what you will see for sale in catalogs now. Here is a link to the Webber page where the tolerances for each grade and size are given. 

http://www.starrett-webber.com/GB40.html

They explain it better than I can. There is also a link to the old standard, for reference.

As far as using them for measurement, they of course aren't used for direct measurement, but as a comparison. You can stack them for use on the surface plate and transfer measurements with a height gage. You can set up a sine plate or sine bar with them. You can setup a fixture to set a bore gage. You can use them to verify a micrometer or caliper. And other things. I believe that every machine shop, whether pro or hobby, should have a set. Unless you have a controlled environment, no point in getting the tight tolerance block set.


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## HMF (Sep 27, 2011)

For a home shop machinist, what grade of Gage blocks is good enough?
These sets aren't cheap, after all, from what I see?

Nelson


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## Tony Wells (Sep 27, 2011)

It can be a bucket of worms, so I'll start by saying that you can get by just fine with the lowest grade. It will be more accurate than most anything you have to measure with, and certainly more accurate than anything you will be making. I used to see them on sale at places like Enco for around 100 bucks. Probably more now, but still not too bad, if you get a discount code or something.


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## Tony Wells (Sep 27, 2011)

Good price.....Nelson, put them in your buggy, and press the button! Those are sufficient for most any use at the home shop.


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## Magnum (Sep 27, 2011)

I opted for a CMM setup instead of gage blocks. I know, I know a little pricey compared to actual blocks, but I like having something that can be used for a host of things. Can also be used for reverse engineering or prototype design....

And yes, I actually paid $11K for one. 

http://www.gomeasure3d.com/microscribe.html#mx

And I know this is *WAY *beyond what is needed for a hobby based setup, but it can get you thinking about other ways to check dimensions.


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## Tony Wells (Sep 28, 2011)

I would also agree with that. I keep 0.011 thru 0.500 on hand. I have used a few other places where we had up to 1.000, but I didn't think I could justify the expense of the larger ones. They are quite handy for gaging holes, and can be used to locate holes for measurement, and even for low angles, same as blocks....sine bar or table. And other things I can't come up with off hand. But once you have a set, you'll find places to use them.


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## brucer (Sep 29, 2011)

i have a set of the import gage blocks in my toolbox at work, think they are "B" grade. seems like .0002 tolerance.. i've used them for about 20yrs now, from anything from measuring keyways, setting tool length offsets, stack ups and so on.. my set goes up to 1", seems like i paid around $100 for mine back in the late 80's early 90's...

 a cheap set of import blocks will work fine for home hobby use... when you get them, just clean the cosmolene off of them, sit down, take a micrometer and double check all of them, and make sure they are all etched with the correct numbers... i had a couple blocks that were the same size, and a couple blocks that weren't etched..


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## HMF (Sep 29, 2011)

> author=Tony Wells link=topic=3720.msg27317#msg27317 date=1317161894
> Good price.....Nelson, put them in your buggy, and press the button! Those are sufficient for most any use at the home shop.



I will. They are fine for my uses. Can't afford them at the moment, but when I can I will pick them up. By the way, in the General Forum, the Coupons thread has the code for 10% off shipping until 9/30 for those who want to buy from Enco, don't forget to use it. 

http://hobby-machinist.com/index.php?topic=92.100

Nelson


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## HMF (Sep 29, 2011)

I'm glad to hear that. I'm out of money at the moment. 

I had the rougher Starrett calipers I bought as part of the 5 piece deal for $51, but saw a set of 4 in a wooden case for $90 so I picked them up. I will probably keep the others as spares- I don't sell my stuff usually. 

I still need Gage blocks, V-Blocks, 123 Blocks, and one day I want to buy that Mitutoyo Digital Coolant-proof calipers. So many things to wish for, so little cash! LOL!  ::bludgeon::

Nelson


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## Kevin45 (Dec 30, 2012)

Both pin gages and gage blocks have their place and both are very useful in checking different parts. If you have to have precision holes, you need a set of pin gages, normally on the -.0002 side. Reason being you need the pin gages on the minus side is that a .750 pin gage will not go in to a .750 diameter hole, size for size. So for any small hole boring jobs, pin gages are almost an absolute must.

Gage blocks also have their place for setting up sine bars and sine plates. Checking slot sizes, checking slot locations, and dozens of other things I can't think of right at the moment. I use gage blocks at home all flr the fact that what I do, I use more setups using sine bars and sine plates. That, combined with the fact that I don't have any pin gages yet:rofl:

But any home shop should have a good set of gage blocks, Johnny blocks, Jo blocks, whichever name you want to call them. As far as the accuracy is concerned, you don't need a set that measures to the .000005 tolerance. The reason being that a home shop is not climate controlled like a lot of inspections shops in the workplace. On place I worked the temperature was set at 70 degrees with a certain amount of humidity year round and never changed. Most home shops are in a garage or in a basement where temperature fluctuates and relative humidity fluctuates on a daily basis.

Here is a good little article explaining the different grades:  http://www.qualitymag.com/articles/84769-quality-measurement-graded-gage-blocks-serve-a-purpose

A grade A is used for inspection and a Grade B is for the shop floor or workshop. One thing to remember is the higher Grade you go, the more expensive the set. You start going from hundreds in $$$ to thousands in $$$. If you are just building a general tool in your garage shop, a Grade B will be more than adequate. But is you are building another Hubbell Telescope in a climate controlled area, you want the best there is.


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