Gage blocks

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Mr Ron
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Gage blocks

Post by Mr Ron »

I did a search on this forum for gage blocks and came up zip, so I'm asking this question: Shars has a set of 36 gage (gauge) blocks, economy grade for $64.95. They claim ±.000050 deviation. Is this true or would I be tossing money down the drain? That deviation is way beyond any tolerance I would work to as an amateur.

My 2nd question: I don't have a shell end mill. I assume when using a shell mill, the spindle of the mill has to be precisely 90° to the work. Is this so? Thank you.
Mr.Ron from South Mississippi
John Evans
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Re: Gage blocks

Post by John Evans »

For the home shop guy the cheap import sets are fine, I upgraded to the 81 piece set just because making up the stack to size is easier.Still import though.If the spindle is not at 90* you will have a step where the cuts overlap, even if it is you will see a witness mark at the overlap even if you can not measure it.
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tornitore45
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Re: Gage blocks

Post by tornitore45 »

Gage block are not just a metrology lab item. I have a cheap set of disks around 7/8" diameter with a threaded hole in the center.
They can be stacked, I do not think they can be wringed as Jhonson blocks. Have uses limited only by your imagination.
So what if they are 1/2 a thousand off. Any of my 5 mikes 0-1" have not been calibrated since they left the factory, if even then. Yet my model engines run.
I use them to check piston ring groves width and any kind of slot to small for the inside mike or to awkward to reach.
Use them as removable stop when the carriage need to be moved back and forth to indicate a taper, pick a stack such that the tangent of the angle becomes a round number to read off the indicator.
I use them for layout work.
Against a stop to move a small part in the wise, when making multiple parts, instead of cranking the screws to drill 2 holes at the same distance in all parts.
Mauro Gaetano
in Austin TX
John Hasler
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Re: Gage blocks

Post by John Hasler »

Mauro writes:
> So what if they are 1/2 a thousand off.

Depends. If, like me, you rarely (if ever) make anything that has to fit something someone else made that you don't already have in your hand accuracy is not very important. Precision and reproducibility still are, though. If each of your blocks has an uncertainty of +-.0005" you could easily introduce an error of several thou just by setting up one part using one subset of blocks another part with a different subset. You can avoid this, of course, by calibrating them against your own internal standard (which could be your best micrometer or one of those blocks). Your standard might fail to agree with NIST by .0015". So what?
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SteveHGraham
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Re: Gage blocks

Post by SteveHGraham »

If I were using a whole bunch of blocks stacked on top of each other, I would expect random walk to cancel most of the error.
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GlennW
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Re: Gage blocks

Post by GlennW »

I believe you are reading it incorrectly as they are +/- 50 millionths, not 5 tenths.
Glenn

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Mr Ron
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Re: Gage blocks

Post by Mr Ron »

GlennW wrote: Tue Sep 04, 2018 8:08 pm I believe you are reading it incorrectly as they are +/- 50 millionths, not 5 tenths.
You are quite correct. I'm not used to such big (small) numbers. How about 5x10-5th.
Mr.Ron from South Mississippi
SteveM
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Re: Gage blocks

Post by SteveM »

You might want to consider the 81 piece set. You CAN get any dimension with the 36 piece set, but it will many times involve more blocks than with the 81 piece set. Fewer blocks means easier to use and less deviation (and less chance of dropping a pile of blocks on the floor).

Pick yourself up a sine bar too, if you don't already have one, because using gauge blocks and a sine bar is one of the most accurate way to set an angle.

The accuracy of those blocks is probably beyond what you will need for home shop use.

Steve
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ctwo
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Re: Gage blocks

Post by ctwo »

I bought their 81 pc set when there was a sale, but for $95 I would be happy. I also got a Polish set with a calibration cert from a local reputable service. I knew the owner used them only a couple times for a particular job. They are well in spec and I cannot tell any difference using 10ths mics or dials on a surface plate comparator (I forget the technical name for that small 6x6 surface plate with a round shaft and indicator mount).
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TRX
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Re: Gage blocks

Post by TRX »

I was tidying up my toolboxes earlier this week, found the sine bar I'd never used, and realized I'd never ordered any gage blocks to use with it. Oooh, shiny!... I was looking at prices online, and then started wondering exactly what I'd use them for. Gage pins I use all the time, blocks... I'm going to put that purchase off a while longer.
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Harold_V
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Re: Gage blocks

Post by Harold_V »

An adjustable parallel will suffice when setting an angle with a sign plate or bar. The degree of accuracy is mind boggling, even without gauge blocks.

H
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tornitore45
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Re: Gage blocks

Post by tornitore45 »

With a 5" sine-bar the error at small angle is 0.1145 degrees for each 0.001" error on the block. At high angles is even less.
Mauro Gaetano
in Austin TX
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