Where to buy a 1/8" diameter test bar for measuring TIR on a CNC ER8 spindle?

I've looked high and low, and so far I've found only one place (precisebits) that seems to carry them (they call them calibration blanks). For due diligence reasons I'd like to compare what they have against what others may be offering so that I can have a better idea of both market pricing and what else might be available. Any suggestions on who else might be selling this kind of test bar?

Why not use a 1/8" dowel, or the shank of a broken cutter.

It only need to be round & a ground finish.... you may not have a dial indicator that is fine enough.

If you are checking the holder assembly "trueness", I hope you start by checking the ER8 taper first

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Originally Posted by Superman

Why not use a 1/8" dowel, or the shank of a broken cutter.

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First of all, thank you for your reply.

Well, suppose I did that, and suppose that when I measure the TIR, it comes out too high. To what should I attribute the high TIR? If it's a broken cutter, then who knows for sure whether or not it is the source of the high runout? Whereas if I had a precision test rod instead, then I could have a higher confidence that' its not a meaningful source of the errors.

As for checking the ER8 taper first... maybe I won't need to if I use a precision test rod and the TIR with it in measures out acceptably low. Yes, maybe it won't, but I'm betting that it will, as it's all brand new precision 60K RPM CNC motor-spindle with precision collet (Rego-Fix ER8 MS) and ultra high precision Rego-Fix compression nut (allegedly balanced for use up to 80,000 RPM) tightened to the Rego-Fix specified torque. If it doesn't, then at that point I might have to pull it all apart and do it then, but if it does, as I'm betting it will, I've saved a measurement step. Anyway, the measurement I most care about is the TIR with the test bar mounted, and which should be quite low. That becomes the baseline TIR. I then have that number to compare against all future TIR measurements taken with whatever cutting tool is installed, which (I hope) can tell me whether the mounted cutting tool is likely at fault if a future TIR measurement is too high.

Ultimately, test bars exist for a reason, and I don't see a downside to owning one. I'm just asking where good places are to buy them. i.e. I don't think we need to rehash TIR measurement protocols here in order to justify owning one or before getting answers to that simple question. I'm not saying that it isn't worthwhile topic, I'm just saying that to me it seems like a topic for a different thread. i.e. for this thread, let's just assume there's a good reason to have one, and the topic of this thread is merely identifying some good sources for where to buy them. i.e. the very title of this thread.

hy white, i don't know exact sources for seeling such stuff, but they exist

however, you may craft your own; it does not matter if you have 1,2, or you just crafted them; is all about how you quality check :
... the test bar
... the spindle
... the test bar inside the spindle

for example : what tir did you noticed inside the spindle ? how much of it comes from your test bar alone ? if you can't control those, you may end up on a buying spree

test bars have to be made from stable dimensional material over time, heat treat, not rushed machining, transported without shock, and keeped in conservative package; i prreffer to craft them, considering that most things nowadays are low quality

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Well, suppose I did that, and suppose that when I measure the TIR, it comes out too high. To what should I attribute the high TIR?

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if you are lucky, maybe you will notice low tir with a new test bar

if you can't find one, you may ask for such a thing at a local tool/gauge manufacturer in your area / kindly :)

Well, OK, how do I craft a test bar? I don't own a lathe, and test bars cost a lot less than a lathe that could make a good test bar--or so I assume. You're right that a purchased test bar could be crap by the time it's delivered (or maybe even before its delivered), but at least I could measure it on a test plate to hopefully see whether it is good or not. Well, OK, maybe I could do that with a broken endmill bit or a dowel too.... but if they fail the measurement plate test and straight-edge tests--as crude as they are--then I'm back to square one. I mean, if dowel pins made for good test bars, then they would be packaged and sold as such, and test bars would cost about the same as a dowel pin. But AFAIK dowel pins and broken endmills are not sold as test bars on the open market.... Right? i.e. there's a reason why they aren't, and it's because they don't meet the criteria for that purpose. I don't mean to be obstinate, but this isn't new technology and would therefore seem to be a matter of settled fact for many decades now. To me the whole point of a test bar is that it should meet certain minimum specs and that it therefore removes uncertainty, not add to uncertainty because of a dubious pedigree.

I really do hope that a test bar would be properly packaged before shipment to avoid shipping damage... but thank you, you are right, I should check to see if that's the case before ordering any.

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I don't own a lathe, and test bars cost a lot less than a lathe that could make a good test bar--or so I assume

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hy white :) interesting point of view :) what if you make a test bar, and sell it, so to buy a lathe ? haha

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Well, OK, maybe I could do that with a broken endmill bit or a dowel too

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if your test bar is not a single piece, then errors will appear; maybe you can tolerate those errors up to a point, but is not ok for alingment :)

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but if they fail the measurement plate test and straight-edge tests--as crude as they are--then I'm back to square one

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i am sorry, i don't know exactly what you are refering to ...

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I really do hope that a test bar would be properly packaged before shipment to avoid shipping damage... but thank you, you are right, I should check to see if that's the case before ordering any.

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when something is delivered with a quality certificate, it simply means that it was ok before packaging

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okey, back to the test bar; pls check attached image; i made rough drawing, but i hope you can figure out the idea behind it; if you wish, i will explain the reason and advantages off all those differencies

upper half has normal quality conditions ( some missing, but all criticals are there )

the lower half has derogated quality conditions, so to be crafted easier, and still deliver accuracy when inside the spindle

you simply check tir on side at the far end, and as far as the far end is crafted within spec, you can trust your test

is late for me, if you wish for specific details, etc, we may talk tommorow; you need a lathe and a grinding machine to create it

maybe you should check your actual test bar before crafting a new one ? you don't need to check also the new one, because it has in process alingments, so if you craft it well, the process itself should be the guarantee that the product is ok / kindly :)

I just now noticed that you live in Antarctica, so, yes, good on ya, being entirely self-reliant and crafting your own when nothing can get to you in the thick of winter would make perfect sense there.

I appreciate everyone's post. Thank you, I really do. However, with two pushbacks and no leads I'm at wits end about arguing whether to buy a $3- $20 item, which is frankly chump change, rather than to make it from scratch or scrounge for something else. I mean, do you guys make your own endmills too? Because some endmills cost more than that. Sorry, that's a rhetorical question. So, bottom line, If no one has any purchasing leads in the next 36 hours, then on Monday morning I'm just going to place an order with the source I named in the OP and wash my hands of this.

If someone in the future (after Monday) reads this and has a lead, then post it anyway. Maybe it will help others in the future.

If you can't trust that an end mill shank is precision ground enough to test spindle run out , then how can you trust that any end mill will run true after you've tested it with a precision blank .
your over thinking a 5 minute job

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Originally Posted by WhiteHare

I've looked high and low, and so far I've found only one place (precisebits) that seems to carry them (they call them calibration blanks). For due diligence reasons I'd like to compare what they have against what others may be offering so that I can have a better idea of both market pricing and what else might be available. Any suggestions on who else might be selling this kind of test bar?

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Just buy a quality ZZ Gauge Pin the size you need, they are .0001" true to size perfect for testing spindle runout, and for Gauging Holes

Most machine Tool suppliers have Gauge Pins, in sets or individual, these are easy to find, just have to know what to look for.

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Originally Posted by WhiteHare

I've looked high and low, and so far I've found only one place (precisebits) that seems to carry them (they call them calibration blanks). For due diligence reasons I'd like to compare what they have against what others may be offering so that I can have a better idea of both market pricing and what else might be available. Any suggestions on who else might be selling this kind of test bar?

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https://www.travers.com/product/verm...age-58-101-250

The cost is $3.39, for this .i25 Pin, this is just one of many that sell them, the Class ZZ Plus is - 0.000" / +.0002", the Class Z Z Minus is -0.002" / +.0000"

There are other classes of Gage Pins with different tolerances you can choose from

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Originally Posted by mactec54

https://www.travers.com/product/verm...age-58-101-250

The cost is $3.39, for this .i25 Pin, this is just one of many that sell them, the Class ZZ Plus is - 0.000" / +.0002", the Class Z Z Minus is -0.002" / +.0000"

There are other classes of Gage Pins with different tolerances you can choose from

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Thank you! That's a very solid lead, and I don't think I ever would have found it on my own. Also, its 2" legth adds to its desirability, since the measurements I'll be taking (described here: https://www.precisebits.com/tutorial...dle_runout.htm) aim to be at least an inch apart, but the more the merrier!

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when I measure the TIR, it comes out too high. To what should I attribute the high TIR?

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hey white, i just got an idea :
... do this a few times : mount the test bar, check tir, unmount it
... rotate the test bar 180* ( thus mount at diff spindle phase ), and repeat as before
* if test bar ok, then those 2 sets should overlap regardless of spindle condition

some infos ( would you like to read more ? haha ) :
... best result is with test indicator, with the palpator in xy plane, tangent to test bar
... may sound a bit ?!?! but it matters if mounting the test bar delivers repetability; after mounting, check elasticity : put a dial on it, then pull the test bar with your hand, and see if it's reversing to it's original position; you may actuaally use 2 dials, opposing each other; this is a rough test, thus will tell if spindle is really in 'good' condition or not; is possible to have a spindle in good condition, and still see lack of rigidity; is normal up to a point
... if you use a pin, or whatever, thus if your test bar is not a single piece, then errors will appear; even if a pin on it's own has low tolerance, etc, when you mount it in somenthing, and so on, assembly tolerances will sum up

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bottom line, If no one has any purchasing leads in the next 36 hours, then on Monday morning I'm just going to

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tick tock tick tock :)

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Originally Posted by WhiteHare

Thank you! That's a very solid lead, and I don't think I ever would have found it on my own. Also, its 2" legth adds to its desirability, since the measurements I'll be taking (described here: https://www.precisebits.com/tutorial...dle_runout.htm) aim to be at least an inch apart, but the more the merrier!

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Get another larger size as well, or as big as your spindle can take, like .250, these Gage Pins are used for doing what you want to do and much more, to check collet runout, they do come in different lengths, 2" long Pin is a good length length for this test as you can have what ever amount out of the collet you need for the test.