# What Do All Those Zeros Really Mean?



## Cactus Farmer (Mar 13, 2015)

I'm having some internal unease with some folks use of the 4th and 5th digit when talking about machining parts. Most folks can't measure to the 0.0000 with precision, and surely not to the 5th place. By including this place holder you are implying that you can actually measure that accurately . Most can't. I have a comparator and it measures to the 1/10,000 and I can infer to the one hundred thousandth. But I would be very cautious about writing it as such. Do they not understand that to 0.000 is pretty close to perfect. I have pin gauges in minus sizes and a few in the plus range. With a mike you are hard pressed to "see" a difference. The comparator will allow me to "see" it but only with the shop warmed up to a "standard" 70 plus or minus degrees. And then only it has had time to make the machine reach the same temp. The base of the comparator is BIG cast iron and warms very slowly. Is there a need for a lesson of accuracy? Most folks know "ain't" is not proper but "irregardless" is not too. Both are double negatives......Flammable and inflammable? Is one capable of burning and the other not? No, both will toast your behind if handled carelessly.
It just irks me no end for the language to be used poorly. I want to be accurate in my making of things but I want to convey what I did as concisely as possible with a common understanding as to
what I mean with a written explanation.
It seems like the most measurements that bug me are bore diameters of barrels. And sizes of the bullets that are fired through them.
To restate the idea, 0.10 implies accurate to 1/100 of an inch. 0.100 is accurate to 1/1000 of said inch , and 0.10000 is accurate to 1/10,000 if that inch. As I stated above, my comparator has a 2 1/2 inch thimble to to move the stage but it is still 0.025 per revolution just like a standard micrometer. That spreads the 1/1000 marks to about 1/2 inch apart. There are small marks between the 1/1000 marks that corespond to 1/10,000 if an inch. If I need a quick check on a tap for size and TPI it is not a big deal to measure the needed dimention. If "class of fit" for that same tap is required I need to wait for the shop to stablize temperature wise before attempting a measurement. Temperature makes things move!
So, adding zeros after the first three places is you impling have measured something with this degree of precision.
Most jobs require 0.001 accuracy or so. Putting that extra digit after the one thousants place is not adding precision if you can't measure it with sureity. If I need a tight fit on ,say, a bearing fit, -0.002 will surfice.
0.125 is an eight of an inch. Now measure 0.124 or 0.126 with that steel rule and tell me the difference. You are better than me if you can see that little change. The same applys to micrometers. 0.0011 and 0.0012 look a whole lot alike in your warm hand.  
What I am trying to convey is adding a 4th digit may look cool as everything, your work will not be any better that your measurements.


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## John Hasler (Mar 13, 2015)

Cactus Farmer said:


> Most folks know "ain't" is not proper but "irregardless" is not too.



I wouldn't show that sentence to my high school english teacher...


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## RJSakowski (Mar 13, 2015)

In a professional setting, I would agree with you.  

But for my own personal use, I use four decimal places, because my DRO's are capable of four decimal places resolution and because it eliminates some of the ambiguity in the conversion of millimeters to inches and common fractions to decimal fractions.  But I realize the capabilities that I and my machines have and I know what fit and finish is required to make a serviceable part. I also over-define features by multiple dimensions.  I do this for my convenience even though it is a drafting transgression to do so. 

I have seen instances where metric measurement was rounded to three decimal place inch measurement and the rounding error compounded over a number of dimensions in a chain to the point where the machined part was unusable. (12 iterations of holes spaced on 9 mm centers; rounding down to .354"  produce a .004" offset).  This can avoided to a certain extent by proper use of ordinate dimensioning.  But I realized the capabilities that I and my machines have and I know what fit and finish is required to make a serviceable part.

The important thing is to properly, unambiguously, and efficiently convey the design intent.  "Ain't" may not be proper use of the English language but there are far worse transgressions in our modern day communication that need to be fixed first.


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## Boswell (Mar 13, 2015)

for me I have no illusions that I can consistently hit 0.001 accuracy. I am not a machinist or an engineer but I thought that accuracy was defined separate of the target dimension such as 2.0 Plus or Minus .0001 .    On my Lathe with a DRO my drawing often come out with 3 or 4 places after the decimal. This is because the number of places to print is a default setting that I don't see the need to adjust. Just the same, If I am on the Lathe turning to 1.5" diameter, I am going to turn it down until the DRO says 1.5000  Not because I believe that I will be that accurate but because I think I will be as accurate as I can and most likely better than if I stopped with the DRO read 1.502.


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## Holescreek (Mar 13, 2015)

Use of excessive zeros means you're delusional. But who isn't?  It's not against the law as long as no one gets hurt.  Drop your guns or I'll start adding zero's 'till the whole place blows up!


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## chips&more (Mar 13, 2015)

In a machine shop, if you propose to have a part made with a bunch of 5 place and more 0’s, you are going to pay dearly for that part. Holding that kind of tolerance in a machine shop is not easy and it will cost you. And IMHO a DRO with 5 places is kinda silly, especially on a manual milling machine. You might as well tape over that last digit…Good Luck, Dave.


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## Whyemier (Mar 13, 2015)

Leave it to a Texan to get to the point in a round-about- way. Cactus (even sounds Texan...I like it) has made a good point.  My micrometer and vernier caliper can read tenth of a thousandths (1/10000") but how sure am I of their accuracy in doing so...don't know.  Also I too believe the local temperature can affect them adversely.  Though the engineers at NASA supposedly work in hundreths of a thousandth (1/100000) or millionths (1/1000000) so somebody knows how to go there.  Not me, I'm satisfied with + - .001 on my work. What are we trying to do?  Rocket science?


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## John Hasler (Mar 13, 2015)

Whyemier said:


> Leave it to a Texan to get to the point in a round-about- way. Cactus (even sounds Texan...I like it) has made a good point.  My micrometer and vernier caliper can read tenth of a thousandths (1/10000") but how sure am I of their accuracy in doing so...don't know.  Also I too believe the local temperature can affect them adversely.  Though the engineers at NASA supposedly work in hundreths of a thousandth (1/100000) or millionths (1/1000000) so somebody knows how to go there.  Not me, I'm satisfied with + - .001 on my work. What are we trying to do?  Rocket science?


We need to be careful to distinguish between repeatability and accuracy.  You probably can make two parts that match to within a few tenths.


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## nobog (Mar 13, 2015)

Accuracy and resolution are completely different, I made a post as such:

http://www.hobby-machinist.com/threads/metrology-101.22521/

Jim


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## Cactus Farmer (Mar 13, 2015)

Mr. Hasler, sir,
     I have never claimed to be an english major. I AM a geologist by profession and a gunsmith by avocation. I wrote this as a pet peave. I know my limitations, (as Mr. Eastwood said). 0.000 is way close. Now with scraping you  can, with three surfaces and alternating them, approach nil, the virtual penaplane. Flat an the preverbial flitter.Left to erosion alone,the earth will eventually be flat, but due to the movement of the earths plates and a few pesky volcanos it will very likely never happen. I just want things to work smoothly. And if putting a butt load of zeros behind any actually acheaveable measurement, and it toots your horn plus makes your projects work any better, go for it. As for me and mine, I'll enjoy the 75 degree day in shorts and a t-shirt. I hope you have the day your deserve.........


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## Cactus Farmer (Mar 13, 2015)

Whyemier said:


> Leave it to a Texan to get to the point in a round-about- way. Cactus (even sounds Texan...I like it) has made a good point.  My micrometer and vernier caliper can read tenth of a thousandths (1/10000") but how sure am I of their accuracy in doing so...don't know.  Also I too believe the local temperature can affect them adversely.  Though the engineers at NASA supposedly work in hundreths of a thousandth (1/100000) or millionths (1/1000000) so somebody knows how to go there.  Not me, I'm satisfied with + - .001 on my work. What are we trying to do?  Rocket science?


 
Thanks, I'm proud to be a Texan, although I was born in New Mexico, it was in the part that was part of the Republic of Texas before statehood.
And close enought to theTexas border to shell it with an 87mm mortar. Hobbs to be exact. Have a great day.


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## gt40 (Mar 13, 2015)

chips&more said:


> In a machine shop, if you propose to have a part made with a bunch of 5 place and more 0’s, you are going to pay dearly for that part. Holding that kind of tolerance in a machine shop is not easy and it will cost you. And IMHO a DRO with 5 places is kinda silly, especially on a manual milling machine. You might as well tape over that last digit…Good Luck, Dave.



I did exactly that and taped over the last digit with gaffers tape.


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## tertiaryjim (Mar 14, 2015)

Many measurements are comparative and need to be read to the forth decimal place.
If the components are at the same temperature when the measurements are taken there is no problem unless one will have differing expansion rates.
Some bearings need a large press fit to expand the inner race to the proper DIM. and to keep them in place. Others need only a couple tenths to retain them and to be certain they are centered.
In scraping two surfaces to be parallel and flat or measuring a dovetail or.....
There are far too many examples to name where measuring a part or machining a part to within a tenth or two tenths or less than a tenth is needed and many people in the forum are capable of it.

I've met others who would only use three decimal places and that's OK for you.
Sorry it bothers you so much!


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## VFM3 (Mar 14, 2015)

If four decimal places bothers you so much, switch the resolution to metric!

As stated before, resolution and accuracy are two different things.


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## GK1918 (Mar 14, 2015)

OH this is good!   And I aint no book writer either.  So when I write my chicken scratches I write  .5  not .500 or .50000 I'm saving ink.  Then 
I understand todays micrometers all have plastic on the frame for the .00000 readings cause of the heat of your hand ? wonder bout that.
Really I think its all about what you are doing( the job).  Such as we deal a lot with something like  .0015 to .002 like bearing clearances.
And then there is a machine shop 500 feet from here that does deal with the .000000000's  they have contracts for the big guys
like Boeing and others...  so its job related  so is my oldest,  a union carpenter with a  16th  ruler & he can't read a mic. job related....


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## stupoty (Mar 14, 2015)

GK1918 said:


> OH this is good!   And I aint no book writer either.  So when I write my chicken scratches I write  .5  not .500 or .50000 I'm saving ink.  Then
> I understand todays micrometers all have plastic on the frame for the .00000 readings cause of the heat of your hand ? wonder bout that.
> Really I think its all about what you are doing( the job).  Such as we deal a lot with something like  .0015 to .002 like bearing clearances.
> And then there is a machine shop 500 feet from here that does deal with the .000000000's  they have contracts for the big guys
> like Boeing and others...  so its job related  so is my oldest,  a union carpenter with a  16th  ruler & he can't read a mic. job related....



So thats what the lumps of plastic are for, you live and learn.

Saying about bearing fits, making nice press fits for small (10-12mm od) ball bearing races is a 0.0001" thing, i managed to get a couple to fit nice then realised i needed to change the design.

Surface finish starts to become more important with smaller tolerances.

Stuart


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## GK1918 (Mar 15, 2015)

Yes Stuart,  but don't you think Starrett would have found that out yrs ago.  And then the logic, how long
does one hold a mic in hand to raise the temp. of a mic?  So I think the plastic is for looks or maybe
an easy way to put their name on it. 
sam


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## Walsheng (Mar 15, 2015)

I agree 1,000% (just had to be said.)

John


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## Mark_f (Mar 15, 2015)

interesting conversation. I spent years working with close tolerances to .0002 ALWAYS in a temp controlled environment. The dimension is only good at that temperature and the part must be inspected NORMALIZED at that temperature. In a home shop environment, no you cannot consistently achieve these tolerances because the size will change several times a day with the temperature, but you can achieve that dimension at THAT moment ( and that may make some folks feel good).

I am guilty of adding all those zeros, only because I was used to it. I also know they don't really matter in my little shed of a shop in the back yard, but I keep using them. The little zeros are pretty and make the print look nice. And if i knew they bothered someone, I would add a few more just to watch them wind up and explode. 

I have enjoyed reading this thread, Have a wonderful day in your shop


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## Whyemier (Mar 15, 2015)

NO! NO! My head has a tendancy to EXPLODE! Don't do it!
 Well...mayB not, interesting post anyway.


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## RJSakowski (Mar 15, 2015)

What I get a chuckle out of are the the news releases where they will give quantity in metric measure with zero significant digits and in parentheses give the English value to three decimal places.


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## n3480h (Mar 15, 2015)

Accurately machining parts while accounting for the thermal expansion rates of all the alloys we work with will most certainly drive one 99.9999997% crazy.

Tom


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## Terrywerm (Mar 15, 2015)

I've always taken the attitude that each and every one of us can use the number of zeros that we prefer, but I can see Cactus Farmer's point as well. Myself, I simply ignore the extra zeros on my DRO and when reading something in print, and I typically only use three places after the decimal when writing down measurements.

When it comes to my paycheck, on the other hand, I often wish there were more zeros thrown in just ahead of the decimal point!


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## mcostello (Mar 15, 2015)

Wife worked with a guy that got a .001 of a cent raise per year, He posted His paycheck on bulletin board at work to prove it. Company policy said everyone HAD to get a raise every year, did not say how much.


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## astjp2 (Mar 16, 2015)

We bend sheetmetal to a .001 tolerance, I am still amazed at watching the benders on a brake use a dial/digital calipers for validating bend lengths.  Tim


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## kd4gij (Mar 28, 2015)

Hay the more zero's on the print=more dollars on the bill. Works for me


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## ariscats (Apr 21, 2015)

RJSakowski said:


> What I get a chuckle out of are the the news releases where they will give quantity in metric measure with zero significant digits and in parentheses give the English value to three decimal places.


When calculators got cheap!!!!!!.I can remember times when you had to convert dollars to,lets say,pounds a cent was precise enough even for much money.


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## OldMachinist (Apr 21, 2015)




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## Cactus Farmer (Apr 22, 2015)

OldMachinist said:


> View attachment 99993



Now , that is funny. And a better explanation than I ever saw before. I am 66.0000000 years old. BaBaBaBahahahaha


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## Bill C. (Apr 22, 2015)

One of my collage professors worked for Cincinnati-Milacron years ago as lead engineer.  He told the class he had to get on junior engineers for marking pipe hanger hole locations to a +/-.000.  Designers get in the habit of marking all their dimensions +/- .000.


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## RJSakowski (Apr 22, 2015)

Cactus Farmer said:


> Now , that is funny. And a better explanation than I ever saw before. I am 66.0000000 years old. BaBaBaBahahahaha


Wow, great timing Cactus Farmer!  That last decimal place in your age represents 3.15 seconds.


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## DanLins (May 2, 2015)

As a professional land surveyor in a previous life, I heard various discussions concerning accuracy versus precision. Here is a  quick and dirty example of the distinction: http://www.honolulu.hawaii.edu/instruct/natsci/science/brill/sci122/SciLab/L5/accprec.html

There are plenty of other, more in depth webpages on this, but you get the idea.
I am assuming from previous posts in this thread that the precision being discussed relates to resolution of the DRO or vernier scale.

I do agree with the OP, dealing with most of our day to day measurements to greater than 0.001" is neither easy nor necessary for hobby machinists.

Dan


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## ariscats (May 2, 2015)

The real joke happens when,using a CAD program, you convert from imperial to metric and you let the presentation to
the 8 decimal digits.Once, making a printed circuit board,i was asked to position two holes at a distance of 1.96850393
inch.It was actually 5cm.The man insisted to this "specification" because the 'computer had calculated it precisely'.
Ariscats


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## cathead (May 2, 2015)

Happy Birthday Cactus!


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## Tony Wells (May 2, 2015)

± 0.000 is fine (but usually unnecessary IMO) as long as it is accompanied by the appropriate GD&T notations. I have seen it a number of times.


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## Bill C. (May 2, 2015)

It drove my crazy trying to hold a dimension using DRO with .0005 readout.  Every time I tighten the table clamps the setting would change on those old machines.  I would put a piece of tape over the last digit.


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## 4GSR (May 2, 2015)

Did a drawing package for a customer of mine.  All the proper dimensions and tolerancing were used.  Months later, started getting emails from their machine shop on the other side of the world.  "We can't machine to these dimensions, and the tolerances, OMG!".  Found out, my customer has taken my drawings to another vendor and had them put in Solidworks.  Solidworks pretty much has one way to deal with tolerances, either every dimension is +/-.0005" or +/-.005".  Can't do +/-.010".  Oh, some of the dimensions I had place on the drawings were nowhere to be found!  They placed all the linear dimensions from one end only, the end opposite of where a cutting tool starts!


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## redgalvin (May 2, 2015)

I'm an old carpenter, an aged aspiring machinist. 40 years ago, we built a prototype cabinet for a Sony TV. (It was obsolete before it went into production.) The engineers, from Japan, had 6' long calipers measuring our cabinet, scowling and expressing their disapproval of our tolerances.. A 64th of an inch (how many thousandths is that, is pretty good in a cabinet shop.


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## Bill C. (May 2, 2015)

4gsr said:


> Did a drawing package for a customer of mine.  All the proper dimensions and tolerancing were used.  Months later, started getting emails from their machine shop on the other side of the world.  "We can't machine to these dimensions, and the tolerances, OMG!".  Found out, my customer has taken my drawings to another vendor and had them put in Solidworks.  Solidworks pretty much has one way to deal with tolerances, either every dimension is +/-.0005" or +/-.005".  Can't do +/-.010".  Oh, some of the dimensions I had place on the drawings were nowhere to be found!  They placed all the linear dimensions from one end only, the end opposite of where a cutting tool starts!



That is a shame they would do that to your finished drawings.  Those machinist were blaming you for all errors.  I had a few prints sent back the project designer for clarification.  I have messed up some short run production parts because I misinterpreted a print.


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## astjp2 (May 2, 2015)

I just installed a DRO for a mill at work, the 10uM scales were .0001 and the 5uM scales were .00001 on the Newall DP7 DRO dispaly.....


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## astjp2 (May 2, 2015)

Measure with a micrometer and  cut it with an AXE!


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## 4GSR (May 2, 2015)

Bill C. said:


> That is a shame they would do that to your finished drawings.  Those machinist were blaming you for all errors.  I had a few prints sent back the project designer for clarification.  I have messed up some short run production parts because I misinterpreted a print.


It's all good, they didn't know that I did the drawings.  But I notice it when the questions came up and the NCR's started coming to my mailbox!  I deal with several shops all over, including this one in China.  The people over there are very helpful in dealing with problems like these.  There are a couple of people over there that are very fluent in English, they are the one's I talk to through email.

I have a digital readout I mounted on my Sheldon lathe last year.  Drives me nuts, it goes out to six places!  I can't even count that far, much less get the movements to zero out to six places!


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## sgisler (May 3, 2015)

astjp2 said:


> Measure with a micrometer.....


, mark it with a crayon 


astjp2 said:


> ...and  cut it with an AXE!






Stan,
Sent from my iPhone using Tapatalk


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## Tony Wells (May 3, 2015)

Measure with string
Mark with chalk
Cut with axe or torch
Beat to fit
weld in place
paint to match


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## ariscats (May 6, 2015)

astjp2 said:


> Measure with a micrometer and  cut it with an AXE!


You forgot.Mark with a chalk.
Ariscats


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## The Liberal Arts Garage (May 6, 2015)

Cactus Farmer said:


> I'm having some internal unease with some folks use of the 4th and 5th digit when talking about machining parts. Most folks can't measure to the 0.0000 with precision, and surely not to the 5th place. By including this place holder you are implying that you can actually measure that accurately . Most can't. I have a comparator and it measures to the 1/10,000 and I can infer to the one hundred thousandth. But I would be very cautious about writing it as such. Do they not understand that to 0.000 is pretty close to perfect. I have pin gauges in minus sizes and a few in the plus range. With a mike you are hard pressed to "see" a difference. The comparator will allow me to "see" it but only with the shop warmed up to a "standard" 70 plus or minus degrees. And then only it has had time to make the machine reach the same temp. The base of the comparator is BIG cast iron and warms very slowly. Is there a need for a lesson of accuracy? Most folks know "ain't" is not proper but "irregardless" is not too. Both are double negatives......Flammable and inflammable? Is one capable of burning and the other not? No, both will toast your behind if handled carelessly.
> It just irks me no end for the language to be used poorly. I want to be accurate in my making of things but I want to convey what I did as concisely as possible with a common understanding as to
> what I mean with a written explanation.
> It seems like the most measurements that bug me are bore diameters of barrels. And sizes of the bullets that are fired through them.
> ...


Danger: You have brought up some thing an early math teacher I had long ago would
carry on about .  Do not report result more accurate than you sources.


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## Optic Eyes (Apr 28, 2021)

I would see guys using files, emery paper and not realising a file gives you a bunch of diameters so one might be right, if you want accuracy on a lathe put a tool post grinder on it, that changes the game


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