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Dimensioning bores
2

Dimensioning bores

Dimensioning bores

(OP)
I'm currently designing a parts catcher for a machine. Doing detailed design work is something relatively new to me so I'm unsure about drawing standards and dimensioning.

I have a shaft that is 45mm in diameter. A 'sleeve' will slide over the shaft. I require a clearance fit (H11). According to my Zues book a H11 fit for a hole in the region of 45mm dia would result in a bore size of 45.160mm.

My question is this:

In the drawing do I label the bore to be machined to 45mm with a H11 fit or do I label the bore to be machined to 45.160mm.

Also, could anyone recomomend a good drawing standards and geometric tolerancing book (SI)?

How do I then go about giving the machinists a tolerance?

Would the 45.160mm be my maximum bore size or would I have a tolerance +/- either side of 45.160?

 

RE: Dimensioning bores

Are you in the UK?  If so you're probably best off working to BS8888, which is essentially a compendium of ISO standards http://www.roymech.co.uk/Useful_Tables/Drawing/Drawing.html
has some usefull information.

Having worked in the UK, the old H11 etc fits seemed a bit of a hit and miss on if they'd be understood by machinists/vendors so I always used to give the actual dimensions on the print.  Exception was on screw threads where I did just give the fit class info.

The tolerance on the bore is given in the fit tables.  The fit tables give a range.  So in your case I believe it's 45 to 45.16 HOWEVER for this to work properly the shaft will have to be toleranced similarly based on the same shaft/hole fit standard.  Not sure what class your shaft as you don't give it.

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RE: Dimensioning bores

KENAT,

I was just going to go there, and you beat me to it.  

Something like "Oh, so you've attended a Y14.5 meeting, have you?"

Evan Janeshewski

Axymetrix Quality Engineering Inc.
www.axymetrix.ca

RE: Dimensioning bores

KENAT,
I resemble that remark.
Gringy,
What is zues? I have heard that someplaces (ISO people)do not specify tolerance limits just like you referenced, are you ISO?
KENAT is right, the American standard is to explicitly specify tolerances (do the calculation for them).
 

RE: Dimensioning bores

KENAT,
Thanks, Now you just had to rub it in ;), I am jealous.

RE: Dimensioning bores

Wow, I can't even get that on the internet it converts it to zeus??

RE: Dimensioning bores

(OP)
Thanks for the info, jokes and link.

I am UK based.

The shaft is 45mm to 44.96mm dia. An H11 fit is stated to be 0 to +0.160mm. Therefore if on the drawing I state the tolerance to be 45.00 to 45.16 and the machinist cuts the bore at the lower end of the tolerance then I will end up with very little clearance. So should I bring the minimum closer to the maximum tolerance? 45.10 to 45.16?

Can any of you recommend a good book for drawing standards and geometric tolerancing (ISO)?

RE: Dimensioning bores

If you change the tolerance it won't be H11 anymore, your looking more like an E9 or a D10.  Which class you choose depends on how you want it to function.

RE: Dimensioning bores

Your question on fit really depends on your function.

The shaft fit tables only really work when you pick both parts based on them.  I don't see the fit you state for your shaft in my zeus book.  Certainly it doesn't seem to be a c11 witch is the suggested match for an H11 to give a loose clearance fit.  The clearance fit comes from both parts not just one.

Now if you want to emulate the minimum clearance from an H11/c11 fit you can achieve that by setting your min sleeve dia as 45.14 if I'm reading my chart right.  However, since your shaft doesn't even match the tolerance range of a c11 you don't emulate the fit across the full tolerance range.

So, if your shaft dia is fixed then I'd use the chart for guidance, check with manufacturing what tolerance they can hold on the sleeve, check against your real functional requirements and go from there.

As to books, I used to just read over the standards but they aren't the most user friendly.

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RE: Dimensioning bores

(OP)
I hadn't taken the C11 into account when designing the part. I simply picked 45mm dia as that was the round bar size available and I don't have the ability to turn the shaft to the required size. (I'll now remember to match tolerances in future)

I'll have to make do with making the sleeve dia min at 45.14mm. For the function required of the shaft this should be fine.

Thanks again for the help and advice.  

RE: Dimensioning bores

Grindy,
I are you new to the profession? Are you ISO schooled (non-US background)? Company standards inch or metric based normally?

RE: Dimensioning bores

(OP)
Hello fsincox,

I've been in the profession 11 years, in a maintenance engineering role. So I haven't really had too much to do with the creation of 'correct' technical drawings and the standards associated with them. I'm starting/trying to drift away from maintenace and take a greater role in the (mechanical) design of various parts for different machinery. (Although at the moment I appear to be making the odd mistake)

I am ISO schooled and my company is metric based.    

RE: Dimensioning bores

Are you using stock bar rather than machined shaft?  In that case you may have another issue, the straightnes of the bar, that you'll need to look into, as well as the bar dia tolerance.  In fact, while I'm rusty on some of the implications, ISO generally treats size and form control separately so you'd need to think about it even if it's a precision shaft plus maybe how round it is.

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RE: Dimensioning bores

(OP)
I'm using stock bar (cost reasons, i'm on a very tight budget). I have measured the bar at various points along its length and have found the bar to be between 44.96 and 45.00.

For the application a stock bar is acceptable although I understand that there are potential issues relating to varrying dimensions and accuracy.

  

RE: Dimensioning bores

Grindy - If your shaft is 45.000 - 44.960 you have a 45h8 shaft. If you want a 45H11 hole you will not have a clearance fit. You will have anything from a fine to a wide sliding fit. H on h is the best you can have without interference.If you want a clearance fit you need to go to lower on the shaft. More like a 45e8.
You give the dim on the print as: Shaft 45e8 and on the hole 45H11. On the bottom of your print in a special box you list all ISO Tolerances that are on your print for the machinists use. I.e. 45e8 = 45 -50/-89
          45H11 = 45 0/+160
The reason for this will be clear to you once you get deeper into ISO tolerances and I do not want to get into this at this time.
As for a good book  order the reference guide book "Tolerance Table for Nominal Dim.s 1 to 500mm as per ISO/DIN 286 from "Beuth" in English. ISBN 3-410-12677-5. Specify "English". It is a small and handy booklet for everyday use. Order some for the shop.
Go here for good info: http://www.roymech.co.uk/Useful_Tables/ISO_Tolerances/ISO_LIMITS.htm

And here: http://www.beuth.de/cn/J-7CFB1F358C9D80CB101C856731F9B25A.2/bGV2ZWw9dHBsLWhvbWUmbGFuZ3VhZ2VpZD1lbg**.html
 

RE: Dimensioning bores

Jergenwrt,
do you know ISO?
Jergenwrt & Grindy,
I have a thread on ISO 2768 and general tolerancing mehtods it in the ISO standards, I would like to know how you feel about working in that envioronment. Can you still use position on surfaces?

RE: Dimensioning bores

fsincox - I can not answer your question on "position on surfaces". We manufacture mostly small precision parts ( Industrial Sewing Machines) and on our prints we will have a note: "Unless otherwise specified all tolerances are ISO 2786 -m" or f, c, v.
Tolerances under ISO 286 are given as for instance 12H7 or 12h6. Of the two systems "Standard Shaft and Standard Bore" most will use "Standard Bore (Hole)" since this system will save you money on gaging equipment and it is easier to produce a shaft at a tolerance required for a specific fit.
Reamers for instance are marked H7 and that is all you need in most cases and coming from a tool room background - one set of H7 reamers (2H7, 3H7, 4H7 etc.)is all that you will need. Reamers are not marked 12 +18. If you mark your print  with the tolerance listed i.e. 12 + 18 the shop may not know that this is a standard 12H7 reamer tol..
Also by listing a tol. as for instance 12H7 for the hole and 12r6 for the shaft the shop can look at a DIN 7157 (sorry I don't know the ISO #)table and they will know what type of fit is required. In this case a light press fit.
In a separate block on the bottom of a print we list all ISO 286 tolerances on this print with the +/- call out.  

RE: Dimensioning bores

They do not specify the sizes in your shop either? I assume you interpret these drawings then, and have no issues? I would like to experience an environment like that, just to see how it works. Guys, can we take this to the ISO section? Envelope or no envelope?

RE: Dimensioning bores

Do you want and ISO based book or ANSI book on GD&T? there is ANSI in metric here.

RE: Dimensioning bores

Is Zeus not a good reference for GD&T? Is it just the fit tables?

RE: Dimensioning bores

KENAT
used it in anger? I didn't catch that at first, what do you mean by that?

RE: Dimensioning bores

juergenwt,
I mean does the ISO still allow the use of position tolerances on surface locations shown with basic dimensions?

RE: Dimensioning bores

fsincox,
Yes, ISO still allows the use of position tolerance on surface locations with basic dimensions. The meaning of this concept is the same as profile of surface tolerance in Y14.5.
 

RE: Dimensioning bores

Thanks, pmarc. Are you ISO too? I knew ISO had profile, now, so I wondered if they still allowed position usage on surfaces. I really never understood why it need to be different, conceptually. My guess is politics. One thing that pops up in debates here is this whole feature of size vs feature issue, which seems to complicate it for us, if we had just stuck to looking at features it wouldn't make any difference, would it?

RE: Dimensioning bores

fsincox,
I work for company that follows ISO 1101 standard regarding GD&T and I am not so happy with it as I think Y14.5 is much better, precise and logical (even despite few unclear issues like feature of size definition).
 
If I understood you well, you would like to consider all features of size simply as features?
 

RE: Dimensioning bores

pmarc,
I am not sure, I am really trying to understand why ISO doesn't have the issues using position on surfaces and we did. I do think the feature of size issue for us has created a problem that I feel was not necessary. In the 2009 standard now we broadened features of size probably because we limited it's definition in 94.
Shall I assume an American based foreign company then?
 

RE: Dimensioning bores

fsincox, you're taking this way off topic from Grindy's OP.  If you want folks to join one of your discussion threads on ISO/GD&T etc. then I suggest you put the link to that thread rather than just vaguely asking them to join the discussion such as thread182-247563: A different perspective on ISO 2768 or which ever one it was.

Also, I re-read this my posts and didn't see where I said anything about "used in anger", I suggest you give date & time reference in future.

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RE: Dimensioning bores

Kenat, This is the post where you said it. 18 Dec 09 10:15

"Zues is typically a pocket guide for machinists.  I have one here on my shelf though I haven't

used it in anger

since I came to the States."



 

"Wildfires are dangerous, hard to control, and economically catastrophic."

Ben Loosli

RE: Dimensioning bores

Oh, now I see it, thanks.  Yeah, it mostly being metric based I haven't used it much in the US.  Plus for some of the stuff that is in there I have internet bookmarks or stuff posted on my cube walls.  

I also got burnt early on trying to use some of my old references even for US metric stuff since there are some differences.  For instance head height on metric panheads found in North America is typically taller than in most other parts of the world.

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What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Dimensioning bores

kenat,
The "in anger" part was the part that thru me.
Obviously, you can see I am trying to move my stuff else ware.
I do not know how to paste threads like you do
 

RE: Dimensioning bores

Quote (KENAT, 18 Dec 09 10:15):

Zues is typically a pocket guide for machinists.  I have one here on my shelf though I haven't used it in anger since I came to the States.

V

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