Gage blocks

[whateg0]

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

That's what I use for all of my requirements. With my tenths indicator, I can get pretty darn close to what I want.

Dave

[mklotz]

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.

Want to try that again?...

http://www.homemadetools.net/forum/sine ... rors-27695

[tornitore45]

Decimal error. Read 0.011 degree error for a 0.001" over 5"

[whateg0]

Decimal error. Read 0.011 degree error for a 0.001" over 5"

I think the use of bold type is inferring that you are incorrect about the error being less at high angles, because in fact, it gets worse as the angle increases closer to 90.

Dave

[mklotz]

Decimal error. Read 0.011 degree error for a 0.001" over 5"

I think the use of bold type is inferring that you are incorrect about the error being less at high angles, because in fact, it gets worse as the angle increases closer to 90.

Dave

Exactly!

[tornitore45]

I stand corrected.

[Mr Ron]

Thank you all, especially to SteveM. That sounded like good advice which made good sense; the least number of blocks, the less any deviation. I learned something new today. Thanks!

[mklotz]

Thank you all, especially to SteveM. That sounded like good advice which made good sense; the least number of blocks, the less any deviation. I learned something new today. Thanks!

The trick now is to decide which blocks to use to obtain a desired size with the minimum number of blocks. Starrett has a procedure...

http://starrett-webber.com/GB49.html

A minimum block program, SPACEBLK, is available on my webpage if you prefer to go that route.

Note that, even with the 81 block set there will be sizes that cannot be constructed. Try making a 0.1234" stack, for instance. You need to use the 0.1004 block to obtain the 0.0004 but when you do you're left with 0.1234 - 0.1004 = 0.0230 and the smallest block in the set is 0.0500.

[John Hasler]

Thank you all, especially to SteveM. That sounded like good advice which made good sense; the least number of blocks, the less any deviation. I learned something new today. Thanks!

The trick now is to decide which blocks to use to obtain a desired size with the minimum number of blocks. Starrett has a procedure...

http://starrett-webber.com/GB49.html

A minimum block program, SPACEBLK, is available on my webpage if you prefer to go that route.

Note that, even with the 81 block set there will be sizes that cannot be constructed. Try making a 0.1234" stack, for instance. You need to use the 0.1004 block to obtain the 0.0004 but when you do you're left with 0.1234 - 0.1004 = 0.0230 and the smallest block in the set is 0.0500.

You just need to put some of the blocks in backward so that they subtract.

[pete]

Hmmmf, depends on who made and just how trustworthy the manufacturer is if that 50 mil accuracy can be believed or not. Measuring even to that 50 mil level isn't exactly fast, cheap, or all that easy. Laser measurement would get the fast but not the cheap. Exact temperature control would make it easier but again still not cheap or even fast if you factor in the time for temperature stabilization. And there doing it all for $65? My guess is the manufacturer gets maybe half or less than that. So imo I wouldn't bet any large money on those numbers being anything real. Calibration to recertify out of date gauge blocks costs from what I've read about half the price of what a full set of good brand name blocks will cost you. So who's ever going to spend the money to have a cheap set checked? Yeah ok for a whole lot of what most of us need then absolute trust in your gauge blocks dimensions might not be really needed most times. Except when something comes along that does need it. Then wot? Years ago I bought an offshore grade 2 imperial 81 pc set. Cost me almost $600 landed at my door after money exchange, customs, Fedex etc all got there piece of the pie. That set looked pretty good. Came with an official "looking" certificate showing each blocks exact size and how much each one deviated from from the true size. Odd thing is when cleaning them and putting them all back in each numbered position in the box two of them measured and were factory marked with the exact same size. Funny how that official looking certificate somehow missed that little detail.

It seems to me that for very hard to easily and accurately verify any items exact size to millionths, surface flatness (offshore surface plates) rotary or dividing head accuracy to seconds of arc etc then it really invites cheating by any less than trustworthy manufacturers if they want to do so. That first set of gauge blocks are now my shop blocks for use where it's not really a good idea to risk more expensive gauge blocks. I still double check any stack height using Mitutoyo digital mikes that also get calibrated to a set of NOS Mitutoyo grade 2 gauge blocks that cost me a bit more than twice what the offshore set cost. I've seen a few times when multiple measurements gave me 2- sometimes 3 /10ths and always over what the cheap blocks say they should be. Maybe temperature? But measuring those Mit. blocks in the same way then they show at most within 1/10th. 3-5 measurements almost always averages out to what the measurement should be to remove a bit of my own human and any micrometers errors.

It still all depends on what you normaly do or what might show up in your shop someday. Even knowing that a drill does and will wander a bit, if I'm drilling entry and exhaust holes from the top of a steam cylinders edge it gets set up on a sine bar and I expect the drill to hit that valve cavity almost exactly centered of where I want it every time. The uses and accuracy of good trustworthy gauge blocks are almost endless. Testing and matching unknown angles would be just one of them where your sine bars exact roll distance (double checked with those good gauge blocks) and the blocks used while trial and error checking that taper had better be very good. To me buying lower accuracy is relatively cheap and easy. Adding accuracy when you really do need it sure isn't. So how does my first cheap set compare against the far better Mit. set? The Mitutoyos wring together much easier and certainly hold a lot tighter. And I trust the Mits at least 10 times more than I'd trust the cheap set.

I certainly don't expect anyone to think the same as myself, but it took more time and effort trying to learn the little I think I have than I'd ever like to add up. I now think there's a minimum of 3 reference surfaces in a shop that should be the best you can afford. Gauge Blocks, a Surface Plate and at least one Cylindrical Square. With those 3 you can then check and verify almost anything else your buying for the shop. And for myself checking and adjusting any machines to there best alignment is important. So add a very good 10ths indicator to that cylindrical square and I can do so. From what I've seen and yes my experience is with only one set, but if I had to do it over I think I'd hunt down a good used Starrett, Mit. etc set on Ebay or Craigslist instead of buying the offshore set I did. I also realise most HSM types won't agree with me.

[tornitore45]

Pete, do you have an idea of the performance difference of that steam cylinder port drilled with sine bar set up with certified blocks compared to the same cylinder drilled by simply eyeballing with a plastic school protractor?
I am sure there are industrial processes that can not be done without a fully equipped state of the art metrology lab, but then again there is nothing a home shop need that level of accuracy.
A friend of mine built a model of the Merlin engine complete with supercharger, oil and water pumps and starter. The engine runs well and he is a stickler for doing thing right, yet no precision blocks were used.

Sometime we fall in the trap of worshiping something loosing sense of practicality. If one is pressed to define engineering with the shortest sentence it should be: Engineering is the art of compromise in construction.

[Mr Ron]

Since I'm an amateur machinist, I don't think an expensive set of blocks is a necessity. I can look in awe at the precision work turned out by journeyman machinists. If I can get within .001", I consider that good for me. I guess the question is: if I can get .001 precision with what I now have, do I really need gage blocks.