Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Jan Mon 27, 2020 11:42 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 34 posts ]  Go to page 1, 2  Next
Author Message
 Post subject: Random machining tolerance question
PostPosted: Apr Tue 23, 2019 4:51 am 
Member

Joined: Oct Thu 02, 2014 5:57 am
Posts: 743
Location: Memphis, TN
I understand that in the machining world things are pretty much always said in thousandths of an inch. 0.1 inches wouldn't be said as a tenth of an inch but rather said as "one hundred thousandths" of an inch. My question: How would you say/express .00015?


Top
 Profile  
 
 Post subject: Re: Random machining tolerance question
PostPosted: Apr Tue 23, 2019 4:54 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 33750
Location: SoCal, 91387
Damn small... :wink:

_________________
\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins//////////////////


Top
 Profile  
 
 Post subject: Re: Random machining tolerance question
PostPosted: Apr Tue 23, 2019 5:34 am 
Member

Joined: Mar Sat 23, 2019 10:57 am
Posts: 43
Location: Lincoln Nebraska
That is 15 hundred-thousandths. Very small and very, very, very few machines are capable of that kind of work.
Eric


Top
 Profile  
 
 Post subject: Re: Random machining tolerance question
PostPosted: Apr Tue 23, 2019 6:34 am 
Member

Joined: Oct Thu 02, 2014 5:57 am
Posts: 743
Location: Memphis, TN
Thanks guys! That's good stuff to know but not for the reasons you'd probably expect.

The reason I was asking was because this afternoon the UPS man dropped off a small table saw that I ordered and I just finished setting it up. It's a really well built little saw with tilt and elevation/depth but unfortunately there isn't an adjustment to square the blade's angle with the table/rip fence or the miter gauge/channels. Measuring mine, I was off .00015 of an inch from one end of the blade to the other. 8)

Here's a picture of the saw. There's a 5U4 on the table for a size reference. :lol:


Attachments:
saw.JPG
saw.JPG [ 87.43 KiB | Viewed 691 times ]


Last edited by jack.estes on Apr Tue 23, 2019 6:43 am, edited 3 times in total.
Top
 Profile  
 
 Post subject: Re: Random machining tolerance question
PostPosted: Apr Tue 23, 2019 6:38 am 
Member

Joined: Aug Wed 24, 2011 4:35 am
Posts: 4673
Location: Sunnyvale CA
jack.estes wrote:
I understand that in the machining world things are pretty much always said in thousandths of an inch. 0.1 inches wouldn't be said as a tenth of an inch but rather said as "one hundred thousandths" of an inch. My question: How would you say/express .00015?


One and a half tenths, or tenth and a half, usually. That is a very small number, on the order of the ability to measure it with even pretty good shop tools, and easily altered that much by temperature or the lightest of light contamination. Take a properly zeroed micrometer, rub your finger on the anvil, attempt to re-zero it, and the residual oil will change cause it to be off by maybe that much. wipe it with a cloth and IPA, and back to zero again.

A few tenths is about what the tolerances can be generated in a typical machine shop, but only when absolutely necessary, since that sort of precision work is not required for the vast, vast majority of of applications,

Brett


Top
 Profile  
 
 Post subject: Re: Random machining tolerance question
PostPosted: Apr Tue 23, 2019 7:54 am 
Member
User avatar

Joined: Oct Sun 18, 2009 5:38 am
Posts: 3833
Location: Tyler, Texas 75707-4212
Kind of depends on the type of shop. Typical job shop or smallish production shop that would be a tenth and a half, as Brett says. In shops that specialize in such close tolerance work, that's not all that small a number. That's a whole 150 millionths. Brett pointed out several hard truths to working in those ranges. Everything you touch changes sizes because of heat transfer. Sitting product on a cold (relatively speaking) or warm floor, near a drafty door, anything like that can easily throw a part out of tolerance. Handling it too long, or incorrectly....same thing. There are very few materials that don't move much due to temperature change.

Then there is the problem of measuring it. I have a bench micrometer that reads directly in half-tenths, but of course it's no good unless both it and the product are allowed to soak at the proper temperature for a given time. Shops doing this tight of work are generally temperature and humidity controlled and in the inspection area precautions are taken not to allow things to get out of spec on the basis of temp. There are specialized instruments that can measure things without human contact, such as a laser micrometer. I also have an electronically amplified test indicator that reads in half-tenths (aka 50 millionths), which exerts a limited pressure on the stylus to provide repeatability.

And you won't find shops using conventional cutting tools and equipment to control size to this level. This is where grinding, lapping and superfinishing are done. Usually because parts requiring this close control on size also are required to be very smooth, flat or round....whatever the shape. It's a specialty. Metal removal rates are as you might expect, rather slow. So the process is usually to rough out the part, then move it into the specialty area for finishing. Sometimes with a heat treat step between.


I could ramble a long time on all of this, just like some of you can on radios. I was my primary profession for my working career. But I've said more than needed to answer the OP, so I'll stop.

These are but a few things left over from another shop, as even though my shop has air and heat, it does not qualify as a controlled environment for the type of work we're talking about. I've no doubt that if I am careful, and take the necessary steps, I could come close to hitting sizes with those tolerances, but I could never get the shop officially qualified to be a vendor for that type of work. Nor do I have any I interest in it. I have retired from all that.

_________________
I'm right 97% of the time. Who cares about the other 4%!

-.-. --- .-.. -.. / ---.. ----- --...


Top
 Profile  
 
 Post subject: Re: Random machining tolerance question
PostPosted: Apr Tue 23, 2019 9:56 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 34393
Location: Maryland 20709, USA
jack.estes wrote:
How would you say/express .00015?
Two possibilities:

Point one five thousandths.

Fifteen hundredths (probably most common).

- Leigh

_________________
73 de W3NLB
http://www.AtwaterKent.info
Click "Grebe Stuff" for Synchrophase info


Last edited by Leigh on Apr Tue 23, 2019 10:03 am, edited 2 times in total.

Top
 Profile  
 
 Post subject: Re: Random machining tolerance question
PostPosted: Apr Tue 23, 2019 10:01 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 34393
Location: Maryland 20709, USA
jack.estes wrote:
Measuring mine, I was off .00015 of an inch from one end of the blade to the other. 8)
Extremely unlikely.

It takes some very special instruments to accurately measure such small dimensions.

While your two readings may vary by that much, that does not mean the true error is such.
More likely there are just variables in your measurement accuracy or technique.

Accurate resolution of such measurements would require very special equipment used in a climate-controlled environment.

I'm a master tool & die maker, and own a machine shop specializing in precision work. We could not measure dimensions to that accuracy.

- Leigh

_________________
73 de W3NLB
http://www.AtwaterKent.info
Click "Grebe Stuff" for Synchrophase info


Top
 Profile  
 
 Post subject: Re: Random machining tolerance question
PostPosted: Apr Tue 23, 2019 2:37 pm 
Member
User avatar

Joined: Oct Sun 18, 2009 5:38 am
Posts: 3833
Location: Tyler, Texas 75707-4212
Leigh wrote:
jack.estes wrote:
How would you say/express .00015?
Two possibilities:

Point one five thousandths.

Fifteen hundredths (probably most common).

- Leigh


Leigh, your decimal point slipped once to the right. Look again please.

_________________
I'm right 97% of the time. Who cares about the other 4%!

-.-. --- .-.. -.. / ---.. ----- --...


Top
 Profile  
 
 Post subject: Re: Random machining tolerance question
PostPosted: Apr Tue 23, 2019 2:38 pm 
Member

Joined: Jul Fri 10, 2009 10:13 pm
Posts: 1149
Location: Weymouth,Massachusetts
Did you cut a piece of stock and find a problem?
If there is an adjustment to be made you would likely make it by adjusting your rip fence and not the table.
Also when you made your measurement from the blade to the fence did you rotate the blade and measure from the same point on the same tooth?
I think you need to cut a piece of stock and check it with a square looking into a light.
Just my $.02.
GL,
Henry


Top
 Profile  
 
 Post subject: Re: Random machining tolerance question
PostPosted: Apr Tue 23, 2019 2:39 pm 
Member
User avatar

Joined: Oct Sun 18, 2009 5:38 am
Posts: 3833
Location: Tyler, Texas 75707-4212
Jack, I too would like to know how you came to that conclusion. What instruments did you use to arrive at that figure?

_________________
I'm right 97% of the time. Who cares about the other 4%!

-.-. --- .-.. -.. / ---.. ----- --...


Top
 Profile  
 
 Post subject: Re: Random machining tolerance question
PostPosted: Apr Tue 23, 2019 3:25 pm 
Member
User avatar

Joined: Aug Tue 28, 2018 9:22 pm
Posts: 1479
Location: Sanford Fla 32771
Quote:
Point one five thousandths.

Fifteen hundredths (probably most common).

As a hobby shop some times machinist, that 1st one makes sense, but the 2nd one confuses me.

_________________
Paul of Florida ….I had my patience tested. I’m negative.
https://paulsironhorse.smugmug.com/


Top
 Profile  
 
 Post subject: Re: Random machining tolerance question
PostPosted: Apr Tue 23, 2019 4:03 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 34393
Location: Maryland 20709, USA
pauls.ironhorse wrote:
Quote:
Point one five thousandths.

Fifteen hundredths (probably most common).
As a hobby shop some times machinist, that 1st one makes sense, but the 2nd one confuses me.
Yeah, I agree.

Perhaps "one point five tenths".

But more likely "one hundred fifty millionths".

Regardless of how you say it, it's ridiculously small.

- Leigh

_________________
73 de W3NLB
http://www.AtwaterKent.info
Click "Grebe Stuff" for Synchrophase info


Top
 Profile  
 
 Post subject: Re: Random machining tolerance question
PostPosted: Apr Tue 23, 2019 4:06 pm 
Member

Joined: Oct Thu 20, 2016 3:54 am
Posts: 285
Location: Missoula mt
How did you measure.00015 .?, I have been a machinist for 55 years with thousand of dollars in mics, gauges, dials ect and I would have a very hard time to check .00015 if I had to. My measuring machine is only good to .0001 +-.0001. My guess is you saw .015....WA7OPY :D


Top
 Profile  
 
 Post subject: Re: Random machining tolerance question
PostPosted: Apr Tue 23, 2019 4:30 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 34393
Location: Maryland 20709, USA
wa7opy wrote:
How did you measure.00015 .?, I have been a machinist for 55 years with thousand of dollars in mics, gauges, dials ect and I would have a very hard time to check .00015 if I had to. My measuring machine is only good to .0001 +-.0001. My guess is you saw .015....WA7OPY :D
It seems two experienced machinists share the same opinion.

- Leigh

_________________
73 de W3NLB
http://www.AtwaterKent.info
Click "Grebe Stuff" for Synchrophase info


Top
 Profile  
 
 Post subject: Re: Random machining tolerance question
PostPosted: Apr Tue 23, 2019 4:53 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 8707
Location: Litchfield Minnesota USA
When I had my automatic machining business I would call .00015 exactly that... Point zero zero zero one five. I rarely had to deal with something that fine. Almost everything was seldom over three figures.
The work I did wasn't rockets or nuclear stuff.
Mark D.


Top
 Profile  
 
 Post subject: Re: Random machining tolerance question
PostPosted: Apr Tue 23, 2019 7:28 pm 
Member
User avatar

Joined: Jun Wed 08, 2011 2:33 am
Posts: 9736
Location: Ohio 45177
I used to have an old Swedish instrument for measuring stuff like that. A gnat's gnat's nose hair stuff. Round dial and a steel ball on the end of the feeler or probe or whatever that is. But I find my calipers and micrometers are plenty for anything I do and I did not have the fixtures to utilize such a thing so I floated it off on the 'bay to someone.

_________________
Reddy Kilowatt says; You smell smoke? Sorry about that!


Top
 Profile  
 
 Post subject: Re: Random machining tolerance question
PostPosted: Apr Tue 23, 2019 7:47 pm 
Member

Joined: Aug Wed 24, 2011 4:35 am
Posts: 4673
Location: Sunnyvale CA
wa7opy wrote:
How did you measure.00015 .?, I have been a machinist for 55 years with thousand of dollars in mics, gauges, dials ect and I would have a very hard time to check .00015 if I had to. My measuring machine is only good to .0001 +-.0001. My guess is you saw .015....WA7OPY :D


Maybe, but certainly readouts to 0.00005 are common/ubiquitous on digital micrometers. Of course that's just the resolution, not the accuracy, but if you naively stick your Mitutoyo or Starrett digital mic on a piece, it will give you a number to .00005.

I would bet on a misread, but it's entirely possible that he got that reading (although not with any of the things in the picture!). What it means, in this context, is that his blade is effectively perfectly straight, and he should move on with his life, since shimming it by .00015 is out of the question, and you could probably tighten a bolt here or there and have it move .001-.002 (and it would be pointless because .005-.010 would be plenty close enough).

Brett


Top
 Profile  
 
 Post subject: Re: Random machining tolerance question
PostPosted: Apr Tue 23, 2019 8:04 pm 
Member
User avatar

Joined: Jul Mon 24, 2017 3:27 pm
Posts: 309
Location: 01450
I prefer mm, um, nm, pm etc. for the small stuff.

_________________
- http://www.nixies.us/


Top
 Profile  
 
 Post subject: Re: Random machining tolerance question
PostPosted: Apr Tue 23, 2019 8:37 pm 
Member

Joined: Mar Wed 16, 2011 10:44 pm
Posts: 1101
Location: Peekskill, NY
Correct answer to the original question:

0.00015 inch = 150 microinch


Top
 Profile  
 
Post New Topic Post Reply  [ 34 posts ]  Moderator: Alan Voorhees Go to page 1, 2  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: Dennis H., LBF ARSR, Phonojim, qmavam, Shanabiom, tubesrule and 15 guests



Search for:
Jump to:  


























-->


Privacy Policy :: Powered by phpBB