import gage block questions

I operate a small machine shop and I need some gage blocks for setting tools and general shop use. My shop isnt temp controled so shop grade should be just fine for my needs. I have been looking on eBay and there are some good deals on Starrett gage block sets but they are still a little higher than I can budget right now. I was wondering if anyone has had an oportunity to check out the cheaper, "allmost too cheap" import grade sets.

Some of the advertisers are claiming that the B grade sets meet current standards but I just have that feeling of you get what you pay for. If this saying is true, how bad can they be...? Anyone have any personal experiances with them?

Charles

The cheap import setss are probably pretty good but will likely have subtle issues like the faces not being quite flat enough to wring, and perhaps not as parallel as the good sets. OTOH they will probably be fine for calibrating regular micrometers, etc.

I got one of the cheapie sets at a flea mkt, most of the blocks still wrapped. Few of them perceptibly wring and the "cert" is just an inventory of the sizes and contains a bald statement of conformance, no per-block measurements, etc.

Even so, testing the mikes and calipers with them was an eye-opening experience, I'd strongly suggest you get a set even if small and cheap. One of the ~30 block sets is fine for basic calibration. I wouldn't buy a cheap import set of blocks on the basis of its advertised conformance though.

Might be worth getting a cheap set at first, then a nice one later and move the cheap set to the mill table to aid setups.

Regards,

Greg

Aren't all gage blocks imports these days unless you find NOS?

I wanted a couple Starrett-Webber croblox a couple winters ago fr wear blocks to make up a set, and 2 reputable sources implied they were not sure how much if any was still made on shore unless they were old stock. I did get them drop shipped through LI indicator after about a month (faster than they predicted) but still not clear if there is current production in the US?

smt

You don't say you close you want to get
If your choice is a small set of high quality of a large set of "cheaper" blocks my choice would be the cheap set. Stacking lots of blocks will kill you. My gage studies have shown me that even two blocks are gonna cost you at close to a tenth in repeatability no matter how careful you are (I'm sure many will disagree) .

I buy lots of cheap sets which we check then laser engrave with the actual size (in a carbide shop you go through gage blocks like water).

Even though I buy cheap sets on sale by J&L and Enco I've never seen one off by more than a .0001. If you think you are going to calibrate your mics or DTI to better than that without a controlled gage room you are dreaming.
Not to say you don't need traceable standards but it seems many don't understand how much a gage changes just by holding it in your hands.

This is one of my favorite demos for a newbie. Zero on a block, carry the block around while I show him the shop, then stick the block back in the gage. I've got another nifty demo that involves pointing the laser interferometer at the concrete wall and then leaning on the wall. Gives them a little idea of what it's like to work when you are "splitting tenths" .

If you seriously want to have real traceable measurements in the +/-.0001 range things get expensive real quickly. I've spent almost as much on gauging as my machines but I used to sell gages so I'm kind of a nut on accuracy.
Bob

Thank you for your comments, I am sure what I get will be good enough for my current needs. At the current price I wont cry if they turn out to be c..p. But it sounds like I have a good chance of being happy with what I get. I do prefer to keep money in the local economy and have been looking for months on craigslist but nothing is showing up and now I really do need them.

If I find the ones I get are no good I will share my experiance.

Charles

CarbideBob said:

Even though I buy cheap sets on sale by J&L and Enco I've never seen one off by more than a .0001. If you think you are going to calibrate your mics or DTI to better than that without a controlled gage room you are dreaming.
Not to say you don't need traceable standards but it seems many don't understand how much a gage changes just by holding it in your hands.

This is one of my favorite demos for a newbie. Zero on a block, carry the block around while I show him the shop, then stick the block back in the gage. I've got another nifty demo that involves pointing the laser interferometer at the concrete wall and then leaning on the wall. Gives them a little idea of what it's like to work when you are "splitting tenths" .

If you seriously want to have real traceable measurements in the +/-.0001 range things get expensive real quickly. I've spent almost as much on gauging as my machines but I used to sell gages so I'm kind of a nut on accuracy.
Bob

Click to expand...

It amazes me how clueless some folks are WRT gaging required to achieve reasonably precise results, and the lack of appreciation for thermal effects, both gage setting when the gage was set in another part of the shop, and part temperature, particularly with alum and mag.

Thanks for reaffirming what I knew but couldn't seem to get across to the blockheads that run the shop I last worked at (they shall remain nameless).

I bout a $79 set of chinese Jo blocks several years ago. A cal lab owed me a favor so they calibrated them and provided a cert. They were grade B and the cert paper from the Cal lab agreed with the Chinese cert: about 90% of the time and the other 10% they differed only by a microinch or so. New gage blocks are customarily made to the upper side of the tolerance to provide a wear allowance. So it was with ths set I bought for not much.

All that said, having a set of Jo blocks is great. They are very handy simply as a wrung stack. Add to this set a box of accessories containing a clamping system, terminal accessories (base block, long jaws, scribes, etc) and you have a nroad spectrum metrology resource in two boxes.

http://www.opus.co.uk/html/gauge_block_accessories.html

Management types are generally clueless about the difference between "a couple of tenths" and a quarter of an inch. One place I was at checked my Jo-blocks with a mic and announced that "They're all off by a half-thousandth" ! At one place, the inspector would allow parts to go out bored up to .005 over the high limit "looks OK to me" until warranty claims started coming in.
I know Managers can do math, they can figure out how much their bonus should be in their head.

Do some of you realise that

yesterday, today and tomorrow, measurement tooling is manufactured
no different than any other tooling.

They don't decide on thursday to work sloppy and make shop-grade.
Then on monday, get real fussy and go back to making lab-grade.

The wheels of progress just keep turning out, what ever they were
intended to make. You are paying for the level of scrutiny that was used
in gathering the complete set of items you purchase.

The actual level of quallity will vary most, more by just buying from
new entrants into a given industry. Remember how unbeleivably awfull
some of the early Bridgeport copies were!!
Then after a few years even the low-grade copies were just about
as good as those Textron BP's.

I asked for some "Lab-Grade" Helium recently, for a pilot program
with Tig on aluminum. The supplyer's rep, informed me that for all
that extra ca$h, it was just a matter of sampling. They draw a sniff
of all the run of bottles, and the very purest get labeled "Lab-Grade".
They might be only one or two % purer than "industrial grade".

Again the level of scrutiny, is what we pay for.
M1M

machine1medic said:

yesterday, today and tomorrow, measurement tooling is manufactured
no different than any other tooling. purer than "industrial grade".

Again the level of scrutiny, is what we pay for.
M1M

Click to expand...

That, and in some cases a little extra care in choosing the raw materials and then the extra steps like normalizing and stabilizing the blocks so they don't grow with age.
Having cases put together with glue that doesn't dissolve when in the salt air on those shipping containers is just gravy!

Well, I got the cheap blocks so I thought I would post about what I got. The name on the box is Shears, there is a label on the inside which has each block listed by its own SN and lists the deviation from the standard in microns. Some of the deviation is quite large, but still within standards for shop grade? If you stack several together you do have to take the variation in account or else you will be off by a bit. Most that I have tried do wring together, but not as nicely as others I have used in the past.

I suspect these will do fine for my immediate needs, several used sets available as well and some on this board so perhaps I will get something else later.

Charles

Congrats on the new blocks. If you have to control size it's nice to have a calibration source immediaely on hand.

Summing the individual block variations from your cert sheet with the nominal block size aids in closer actual stack height. I guess you'd call the summed stack height a "presumed" stack height. You can't do this with blocks heavily used since the last calibration because wear will thin the blocks from their last calibrated deviation. New and freshly calibrated blocks however can be stacked to closer tolerances than the grade would otherwise suggest.

Don't discount millionths. Add enough of them up and you can get significant departure from nominal block size. Take a stack of 7 or 13 blocks and you have 7 or 13 calibrated variations to sum. Since shop grade tolerance is +/- 50 millionths and gage blocks are commonly made to the upper side of the tolerance band several tenths variation over set-height can easily result.

Not that it matters for most stuff but when you set-up a stack of Jo block you probably have reason to consider all error sources.

Yes, Forrest, that is good information and so true in this case. I am glad that the set came with this paperwork, I would never be able to measure them myself. My main reason for them is to set my bore gage. I only need to read to .0005 with the gage for most things but I only had a few sizes of gage blocks around and I could never quite set the bore gage the way I wanted to.

Now I have a larger range of sizes of blocks to use to get closer to the nominal size I want to measure. That makes using the bore gage a lot easier. For now I use a very nicely made grinding vise that I got on ebay. I stack up the gage blocks in between the jaws and then use that gap to set my dial bore gage. Not the 100% best way to do it but it works well so far.

Charles