# Measuring TIR, which measurement do I believe?



## WobblyHand (May 29, 2020)

Been having some issues with my drill press.  Either bent drill bits or something else.  Thought it would be good to measure the TIR.  Used a ground 3/8" rod mounted in my drill press chuck, using a  DTI and a dial indicator.  DTI was a no name thing.  It seemed to indicate a lot of runout. 0.003" or so.  I then used an old Federal dial (plunger) indicator (0.0001" per division), it measured 0.0012" TIR (I think, but see below).  Both held by my Noga holder. Made sure neither of them were bottomed out.  The DTI has a little ball, whereas the old Federal has a relatively large hemispherical contact point.

Contact point was 1.5" down from chuck.  Like to believe the Federal.  Have an old Enco (made in Japan) DTI that I can try.  Since I'm just a newbie, I'm well aware that technique (or lack of it) can change the answer.  Like when I forgot to tighten all three points on the Jacobs chuck - that reduced the TIR from 0.005" to 0.003 on the no name DTI.  

Perhaps I don't quite know how to use the DTI.  It was relatively flat to reduce cosine errors.  How flat does it have to be?  For measuring a rod, does it have to be 90 degrees to the axis of the workpiece and the lever tangential to the surface?

When using the Federal dial indicator I noticed the run out didn't strictly repeat.  By that I mean the low point never got that low again.  The high point always seemed to repeat.  So say it started at 0, then went to 0.0014", keep rotating until it should have been 0" again.  Instead it read 0.0002".  Rotate some more and 0.0014", keep going (in same direction) down to 0.0002".  If I change direction or rotation, the Federal will drop to 0.0001, but not 0.  (But if I keep rotating, I get 0.0014 and 0.0002) So is it sticking, or this is sort of what happens?  (0 wasn't really zero,  it was 0.1000")  I put a drop of oil on the tip of the "ball" and the behavior stayed the same.

Don't know if this belongs here, or in the measurement forum.  Either way, I'm a little puzzled.  Can someone enlighten me?


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## Asm109 (May 29, 2020)

With the indicator in touch with your rod in the chuck, grab the chuck and wiggle it around.  You could have slop in bearings, or clearance between ram and drill press body. All can lead to non repeatability.   Second point 3 thou runout on a drill press, CELEBRATE and get on with making chips.
Spindle on lathe, or mill sure you should expect better.


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## Winegrower (May 29, 2020)

It’s a drill press.  You’re good.


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## benmychree (May 29, 2020)

Near enough is good enough.  Unless you need to do exceedingly fine work it quite good enough.


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## WobblyHand (May 29, 2020)

The reason for the exercise was me blowing a press fit.  Maybe I didn't tighten the chuck correctly on the drill bits.  All I know is the reamer did nothing, because the hole was already too large.  Hole was supposed to be reamed to 0.1875, but was already at 0.191.  (After drilling with a 0.185" drill). Honestly, the TIR is better than expected.  Guess the drills are not true, or there's slop in the bearings.  I'll try @Asm109's suggestion to see if there's more movement than a gentle rotation of the pulley provides.

If I can't drill decent holes, won't be any celebrating here...


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## GunsOfNavarone (May 29, 2020)

And since drill bits don't drill perfect holes....it all makes sense. Out of curiosity, what size drill bit did you use and what size reamer?


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## Bob Korves (May 29, 2020)

Drill bits and drill presses are not precision machines.  You can used them to remove bulk metal to an under size dimension and then finish the holes to final size with a different machine or method.


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## WobblyHand (May 29, 2020)

Yes, I know they don't drill perfect holes...  The plan was to use a 0.182, then a 0.185, followed by the reamer to 0.1875.  One of the drills didn't look right - can't remember which one.  Like the tip was fuzzy.  That drill must of been bent, or I just plain didn't tighten the chuck correctly.  Probably was tired or distracted.  I'll look at the two bits again.  It would be nice to replace the bad bit, so it doesn't happen again.


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## WobblyHand (May 29, 2020)

Bob Korves said:


> Drill bits and drill presses are not precision machines.  You can used them to remove bulk metal to an under size dimension and then finish the holes to final size with a different machine or method.


Indeed, as I have found out the hard way!  Hoping to fix that by changing the machine.  And perhaps improve the tooling.


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## benmychree (May 29, 2020)

That allowance for reaming was clearly not enough, I would have allowed 1/64 for reaming.


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## WobblyHand (May 29, 2020)

Live and learn.  Thanks for the lesson. 

So to get the final hole to 0.1875, I need to drill to 0.171875 (0.1875 - 1/64) #17 (0.1730) and then use the reamer?  Or am I missing the forest from the trees?  @benmychree did I get this right?


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## GunsOfNavarone (May 29, 2020)

Wasn't something like drilling a hole so much easier before picking up the machinist bug? It was for me....ditto on the live and learn.


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## WobblyHand (May 29, 2020)

GunsOfNavarone said:


> Wasn't something like drilling a hole so much easier before picking up the machinist bug? It was for me....ditto on the live and learn.


Who knew making a hole was so hard to do?  It isn't, if you don't care about precision.  Once you start to care about precision, even the simple stuff gets a little harder.


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## benmychree (May 29, 2020)

WobblyHand said:


> Live and learn.  Thanks for the lesson.
> 
> So to get the final hole to 0.1875, I need to drill to 0.171875 (0.1875 - 1/64) #17 (0.1730) and then use the reamer?  Or am I missing the forest from the trees?  @benmychree did I get this right?


More or less; I would use an 11/64 drill then ream.  One must recognize that no drill or drill press is going to going to drill a hole that is right on size, especially, if the drill has been resharpened


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## WobblyHand (May 29, 2020)

Yes, 11/64" is better, exactly 0.171875".   For some reason, I had number drills in my head.


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## benmychree (May 29, 2020)

nother thing is to not baby the feed of the reamer, if you do not agressively feed it, it may cut oversize.


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## GunsOfNavarone (May 29, 2020)

So you ARE saying to aggressively feed the reamer?


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## rwm (May 29, 2020)

What RPM would you use here for the reamer?
Robert


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## GunsOfNavarone (May 29, 2020)

Damn @rwm I swear we have the same profile image...


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## rwm (May 29, 2020)

Ha! I never noticed that.
R


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## Asm109 (May 29, 2020)

You should allow 1/64th inch for the reamer on small hole.   Larger you can allow 1/32"


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## benmychree (May 29, 2020)

GunsOfNavarone said:


> So you ARE saying to aggressively feed the reamer?


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## benmychree (May 29, 2020)

Yes, I am saying to agressivly feed the reamer, it forces the reamer to center itself in the hole, instead of wobbling around in it.


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## Aukai (May 30, 2020)

Good to know!!!


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## WobblyHand (May 30, 2020)

Remeasured slop in drill press.  If I push the chuck near the spindle, I can get 0.010" movement from side to side.  (Using my Federal 0.0001/div.  One full rotation of the dial!)   Not good for metal work.  Makes me feel better, I wasn't imagining the "fuzzy drill".  When I measured only 0.0012" TIR by gently rotating the bearing, I thought I could live/suffer with it.  At 0.010" run out (static) I need a better solution.  For me, this is justification to buy a mill.  Yeah, I know, some folks have to learn the hard way...


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## MrWhoopee (May 30, 2020)

It's a drill press, nothing more. It is perfectly fine for its intended purpose. An oversize hole is the fault of an unequal grind on the drill. Once the point is established, the drill will follow it regardless of spindle runout.  The looseness of the spindle just means that it will follow the drill.

Not that I'm trying to discourage you from buying a mill.


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## WobblyHand (Jun 1, 2020)

MrWhoopee said:


> It's a drill press, nothing more. It is perfectly fine for its intended purpose. An oversize hole is the fault of an unequal grind on the drill. Once the point is established, the drill will follow it regardless of spindle runout.  The looseness of the spindle just means that it will follow the drill.
> 
> Not that I'm trying to discourage you from buying a mill.


Is it possible to inspect drills ahead of time for this defect?  What does the defect look like?  

No, you haven't deterred me at all.  Have one coming my way soon.  I'll still need to be able to drill decent holes, so how does one 'inspect the drill bits'?  Or do you spend the day drilling holes with all one's bits and measuring them with gage pins?


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## MrWhoopee (Jun 1, 2020)

Unequal cutting edge length (point off center) is the culprit.  A drill point gage is the tool, though it's only as good as your eyes.




The ultimate test is drilling a test piece and measuring. A drill will always cut on size except when you need it to. Just like a drill press, twist drills are not a precision cutting tool. That's why we bore and ream.


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## Janderso (Jun 1, 2020)

benmychree said:


> nother thing is to not baby the feed of the reamer, if you do not agressively feed it, it may cut oversize.


Good to know, I have watched youtubers reaming very slowly (slow feed)


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## Janderso (Jun 1, 2020)

This is timely


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## WobblyHand (Jun 1, 2020)

MrWhoopee said:


> Unequal cutting edge length (point off center) is the culprit.  A drill point gage is the tool, though it's only as good as your eyes.
> 
> View attachment 326012
> 
> ...


Why is it that a drill isn't a precision cutting tool?  Is it a materials problem, insufficient rigidity, or something else?

While looking up drill point gauges, I found practically no hits on 135 degrees.  I have some cobalt drills and they are 135 degrees.  I did find a reference to Mechanix-Mate drill point gauge with 118 and 135 degree head, but it appears they are no longer made.  Lots of 118 and the corresponding half angle of 59 degrees.  Either that, or my google-fu is weak.


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## MrWhoopee (Jun 1, 2020)

WobblyHand said:


> Why is it that a drill isn't a precision cutting tool?  Is it a materials problem, insufficient rigidity, or something else?



For the very reason that you discovered, it's just too easy for them to cut oversize. A new drill will _probably_ cut on size, once re-sharpened, all bets are off.

Here's an option for a gage.


			Amazon.com
		


and another








						UNION DRILL POINT GAGE TOOL 711181146455 | eBay
					

Find many great new & used options and get the best deals for UNION DRILL POINT GAGE TOOL at the best online prices at eBay! Free shipping for many products!



					www.ebay.com
				




and one more








						(2) Drill Point  & Hole Gages (INCH)Best Drill Gage Ever! 118 &135 degrees  | eBay
					

This is a combination drill sharpening and hole gage. Plus,much more. Also, has a drill hole gage gage built in with sizes of 3.0,4.0,5.0,6.0,7.0.8.0,9.0, 10.0 (mm) and 1/8",5/32",3/16", 7/32",1/4", 9/32", 5/16" and 3/8" (fraction).



					www.ebay.com


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## WobblyHand (Jun 1, 2020)

Hmm, must have hit the drill anti-lottery.  It was a _new_ drill, and it drilled oversized.  C'est la vie...  I'm coming to grips with the reality of big holes.  I accept that the bits drill wide.  Tough lesson for the newbie.

Still, I really wonder what the actual technical reason they cut wider.  Is it a design defect?  Tolerance issue?  Rigidity?  Is there a design that could work?

Since I mostly have new or slightly used drills, it doesn't seem like these drill bit gauges are that useful.  The gauges sound more useful if I were regrinding the drill bits.  Currently don't have a setup to grind the bits.  In any case, couldn't one just use calipers to measure/estimate the lengths?  What would be the allowable mismatch in length?


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## GunsOfNavarone (Jun 1, 2020)

I'm guessing someone more knowledgeable will say, that lobe action yo see on the backside of sheet metal is the inherent problem. Cuts one way, kicks the other all the way down. I'm sure there are many possible reasons, but I'm leaning towards boring bars when I have enough size, but I need to get a mean set of reamers. That in itself is a whole other Oprah. Adjustable, hand, chucking and come in about every size to the thousandth. Ugh.


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## Janderso (Jun 1, 2020)

The only way to get an accurate hole is to bore it. In my limited experience.
An option that you may try is an end mill. You won’t find them in the wide range of sizes as you will drill bits Imho.


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## WobblyHand (Jun 1, 2020)

Using reamers kind of limits one to few standard sizes, just to protect your wallet.  Boring sounds like the way to go, but is darn difficult for smaller sizes.  Above 3/8" seems to be doable, at least for "not too deep" holes.


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## westerner (Jun 1, 2020)

GunsOfNavarone said:


> Wasn't something like drilling a hole so much easier before picking up the machinist bug?


This is soooo true! Just like the shooting sports. I was generally content with my marksmanship and equipment until I started reloading


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## Dabbler (Jun 1, 2020)

No drill drills a hole on size, factory grind or not. On holes up to .500, i expect .002 oversize.


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## MrWhoopee (Jun 1, 2020)

WobblyHand said:


> Still, I really wonder what the actual technical reason they cut wider.  Is it a design defect?  Tolerance issue?  Rigidity?  Is there a design that could work?
> 
> Since I mostly have new or slightly used drills, it doesn't seem like these drill bit gauges are that useful.  The gauges sound more useful if I were regrinding the drill bits.  Currently don't have a setup to grind the bits.  In any case, couldn't one just use calipers to measure/estimate the lengths?  What would be the allowable mismatch in length?



Think of it this way, for every .001 the center is off, the hole will be .002 larger. Any number of very small differences can cause one flute to cut more than the other. An optical comparator is probably the only practical way to measure drills precisely. You can't be certain what size the hole will be without drilling it. That's why there are still reamers, and even a reamer can be made to cut oversize. 

Here's something dealing with the subject:










						Machinist Drilling Mechanical Tolerance Capabilities Chart - ANSI Size Drilled Hole Tolerance, ISO Metric Drill Sizes
					

This chart defines drill manufacturing process capabilities for ANSI size machinist drills. Drilled hole locations and size variations are cumulative of several manufacturing variables. Tool sharpness, accuracy, tool and machine rigidity, machine spindle bearings wear, general quality of...



					www.engineersedge.com
				




Perfection is impossible, that's why we have tolerances.


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## WobblyHand (Jun 2, 2020)

Dabbler said:


> No drill drills a hole on size, factory grind or not. On holes up to .500, i expect .002 oversize.


Wish I could do that well.  I'd be quite happy at 0.002 oversize.  It's the randomness that's hard to deal with.  (Standard deviation of hole size.)  Some drills seem to do better than others, and chucking (is that a word?) tolerances (operator error?) seem to make the actual hole size vary more than is desirable. 

Reducing this by upgrading to a mill, which will reduce TIR of the chuck and bearings, but the variation of the drill bits won't change.  Are there _known good_ drill bits that won't break the bank?  Or is this a crap shoot where one slightly increases the likelihood of good drill bits by sprinkling more money about?


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## WobblyHand (Jun 2, 2020)

MrWhoopee said:


> Think of it this way, for every .001 the center is off, the hole will be .002 larger. Any number of very small differences can cause one flute to cut more than the other. An optical comparator is probably the only practical way to measure drills precisely. You can't be certain what size the hole will be without drilling it. That's why there are still reamers, and even a reamer can be made to cut oversize.
> 
> Here's something dealing with the subject:
> 
> ...


Thanks, this was helpful!  

Someone could probably make a lot of money by inventing better drill bits.  I'd imagine it would reduce machining costs quite a lot.  (I had to resist saying _it would reduce machine costs quite a bit_.)


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## Janderso (Jun 2, 2020)

WobblyHand said:


> Using reamers kind of limits one to few standard sizes, just to protect your wallet.  Boring sounds like the way to go, but is darn difficult for smaller sizes.  Above 3/8" seems to be doable, at least for "not too deep" holes.


Agreed, The , Micro 100 line has some really cool super sharp small boring bars. You can make the holders that fit into your QCTP.


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## GunsOfNavarone (Jun 2, 2020)

AND.. when you sharpen a reamer it loses diameter, cutting smaller. I'm gonna make a laser hole cutter. Easy, peasy, lemon squeezy.


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## Diecutter (Jun 3, 2020)

What about adjustable reamers?  Each one is supposed to be adjustable within a small range and they come in sets covering all sizes within a max and min. sort of like ER collet sets do.  I'm curious whether anyone has experience whether they work well or not? I often thought of buying a set.


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## Bob Korves (Jun 3, 2020)

Diecutter said:


> What about adjustable reamers?  Each one is supposed to be adjustable within a small range and they come in sets covering all sizes within a max and min. sort of like ER collet sets do.  I'm curious whether anyone has experience whether they work well or not? I often thought of buying a set.


Adjustable reamers, by the way they are designed, are not strong or robust.  They must be kept sharp, carefully used, and never forced or they can easily be tweaked, ruining them.  They are definitely not bulk removal tools in stronger metals like steel or similar.  I only use one on ferrous metals when it is the only solution at hand, and then with a gentle and careful touch, no hogging.  They work pretty well when used correctly on brass, bronze, and aluminum bushings...


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## Diecutter (Jun 3, 2020)

Bob Korves said:


> Adjustable reamers, by the way they are designed, are not strong or robust.  They must be kept sharp, carefully used, and never forced or they can easily be tweaked, ruining them.  They are definitely not bulk removal tools in stronger metals like steel or similar.  I only use one on ferrous metals when it is the only solution at hand, and then with a gentle and careful touch, no hogging.  They work pretty well when used correctly on brass, bronze, and aluminum bushings...


Thanks for the explanation, Bob.  I never fail to learn useful information when visiting  this site.


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