Cheap gage blocks...worth it??

[Anko]

Hi to all!

I would like to get a set of gage blocks to make calibrations on my tools and measuring practice, I would like to buy some good brand but they are far out of my reach, then I looked this import set on ebay around US$100 with shipping to my country.

The cuestion is, is this set worth it?? or better save my money and buy some recognized brand loose blocks (for this price maybe only two)

I will apreciate very much any input! Thanks

Saludos

 

[kvom]

I bought a similar Chinese set from Enco, and the blocks are all more accurate than anything I can measure. For a home machinist these are more than good enough.

 

[A1MACH]

An inch is an inch!

 

[winklmj]

The Tool and Die Guy has the answer: http://www.thetoolanddieguy.com/?p=489

I have an Enco set from when they were on sale for stoopid cheap and they are way more accurate than I am.

 

[Entropy455]

This is a VERY good gage block set.

The 50-mm block is undersized by 0.15 x 10^-6 meters, whichis equal to 5.9 millionths of an inch in English units.

Note that the measurement was recorded at 68 degreesFahrenheit.

If you warm that same gage block by one degree Fahrenheit(i.e. if you use it at 69 degrees F) it will grow by 12.8 millionths of an inch– thus making the gage block 6.9 millionths of an inch oversize, in lieu of 5.9 millionths under.

Point being, the gage blocks are manufactured with so tight of tolerances, that a change in temperature of a single degree F will dimensionally change the block more than their manufactured tolerance.

Your biggest concern with a gage block set is keeping them clean, rust free, and preventing dings and nicks. Remember that oils from your handswill damage gage blocks.

 

[Mike N]

Good gage blocks are lapped & designed to ring together when twisted. This will allow you to stack up several blocks without any accumulation of thickness. I have a set of the cheap imports & the finish is too rough to ring together. These are certainly good enough for the work I do!

Oh! buy the way, I think every set gets the same inspection report! We bought 2 sets at the same time, both had the same exact inspection report!

To answer your question, Yes the blocks are worth having around.

 

[terrywerm]

Keeping in mind that most home machinists have limited budgets to work with, we frequently need to look at the less expensive imports. Remember too that we are not using our tools for 40 hours or more per week either. As a result, we can often get just as much valuable use and life out of a cheaper tool as the pros get out of the expensive ones.

 

[jtrout13]

Like said before, this is a good gage block set. I see the largest deviation is 0.5um, which is 0.0005mm. From an engineering perspective (I've engineered a good bit with both US and Metric units,) in the metric system we generally don't dimension past X.XX significant digits. Normally in metric the X.X is good for general work and X.XX for stuff like shaft diameters and close fits. Remember that the standard tolerance for EDM work is around 0.001mm, so this gage block is more precise than you could get with EDM, so it's certainly more precise than anything you'd ever need to measure in a home shop environment.

For gage blocks, there are 4 categories of tolerance grades:
AAA (inspection grade for setting national standards)
AA (calibration grade for calibrating expensive equipment like a CMM)
A (toolroom grade for calibrating standard shop equipment)
B (workshop grade for general measurement work)

Judging by the tolerances on the sheet (the standards are in the machinery's handbook) these gage blocks are much better than grade B. There are only 2 or 3 blocks that are B grade. Methinks this is a toolroom grade (A) set that had a few blocks slightly off, so they sold it as a defective model to a tool wholesaler and you can get a great deal.

 

[Tin Falcon]

Judging by the tolerances on the sheet (the standards are in the machinery's handbook) these gage blocks are much better than grade B. There are only 2 or 3 blocks that are B grade. Methinks this is a toolroom grade (A) set that had a few blocks slightly off, so they sold it as a defective model to a tool wholesaler and you can get a great deal.

I work in the scale industry. my company re certifies mass standards(Test Weight)and we work with weights and measures at times. It is apparently common for standards to be made to a better than stated tolerance. And a few thrown in that makes the set a lower grade. or in the case of weights ,class.

I have been thinking of getting a similar set . Imperial grade B.
And I am wondering if I need the cert. On one hand I know $20 for a cert is cheap. but I can use that 20 for other things is there any real need for my shop to be traceable. Probably will go for the cert.

Tin

 

[purpleknif]

Once you get them you'll wonder how you ever lived without them. The number of different ways to use them is only limited by your imagination.

 

[golddustpeak]

Wouldn't a larger set offer more options and thus more bang for the buck?

 

[jtrout13]

Wouldn't a larger set offer more options and thus more bang for the buck?

This is the standard size for gage block sets. The idea is you can 'wring together' any combination of the blocks to get the desired size. The underlying idea which prevents the need for a larger set is twofold:

1. For calibration work, why require a 500mm gage block, when you could just calibrate over a 100mm length instead?

2. For shop work, generally smaller size work = tighter tolerance work. It's quite unlikely you'd need something over 100mm wide machined to the tolerances a gage block checks. Plus, say you were checking something 500mm wide with gage blocks... By the time you wring together enough blocks to get that width, the tolerances (plus or minus error) on all the blocks you wring will start to add up, and your gage stack might have considerable error on the order of several microns. Also, there's the alignment issue of checking something that wide, you could easily put the gage stack in the slot a bit crooked by mistake and think it was wide enough, but in fact it is too small but the alignment error caused a mistake. In the 'real' world, you'd go ahead and step up to a CMM (coordinate measurement machine) for things outside the realm of the gage blocks.

 

[kvom]

For those who haven't use them before, there's a simple technique for determining which blocks to wring together to get a given dimension. Lets say you are using a sine block and need an angle of 29 degrees with a 6" block. Then the stack size is 6*sine(29) or 2.909". I first select the .109" block leaving 2.800 which leave me to pick the 2.000" and the .800" blocks.

You pick the first block so as to eliminate the thousands digit and bring the hundreds digit to 0 or 5. So for .978" I'd want to select .128" first, leaving .850". This remainder can then be handled by several combinations such as .450+.400.

Wringing blocks is done by placing the two blocks across each other at 90 degrees, and then while pressing them firmly together turn until they are aligned. The idea is to remove all air between them so that external air pressure keeps them together. The blocks need to be smooth and clean. Finger prints on either block will cause failure, but my cheap Chinese blocks will wring when cleaned.

 

[Davo J]

I bought the 83 piece (I think) metric set of ebay for $120 posted and they are fine for home shop use.
If you buy the more expensive sets are you really going to get much more out of them in a non temperature controlled room?
I say go for it and buy them.

Dave

 

[Anko]

Hi people! I'm very happy about all of you for sharing your opinions!

Im very positive about getting a set of gage blocks, the comments are very positive about this set, the precision of these block seems to be just perfect for home workshop, but how about the finish? i'm concerned about the surfaces, the real blocks stick together when you friction one against the other, because of their lapped surface.

but like Mike N said, seems that the surface finish is too rough for this feature?? any more comment about this issue?

Thanks a lot for the help! I have watched ebay for some other option, but seems that this is the only one I can afford, so be it, just want to hear some more input about the surface.


Saludos

 

[kvom]

As I posted before, my blocks will wring if kept perfectly clean. However, for most uses I haven't bothered to wring them. Most of the time I'm using vertical stacks on a surface table.

 

[Davo J]

Mine are finished fine a wring together fine.

Dave

 

[Anko]

Hi to all, after some thinking I came across with a Mitutoyo set of metric mics standars, at least for my porpourse (calibrating my micrometers) this was great.

so I picked up this set and let the gage block ond hold for a while, as the standar are Mitutoyo´s, they are the industrial standards and I expect a very precise tool.

they arrieve today and I make some test, the 25 mm standar sayd 0uM at 20° (I know that Im not in a temperature controlled room)

Then I pick my micrometers and take a try, the results are:
a brand new NSK digital micrometer : 25.003 mm
a used ball tip NSK micrometer: 24.998 mm
a very old used Mitutoyo digital mic: 25.007 mm
and a old and used Mitutoyo mic: 25.00 mm

with an average of 25.002 mm between all.

My cuestion is, for calibrating the nex size micrometer (0.25-50 mm) should I put the Mitutoyo standar as a absolute 25 mm or take it with the error I measured? I ask this because Im very confident that Mitutoyo would give me a very reliable guide.

(I know we are talking about 0.00X mm, but let me be )

Saludos

 

[purpleknif]

Welll... We're talking about microns here. Unless you're working in a metrology lab you won't be able to tell the difference between any of the sets !