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Thread: DIN ISO 2768 mk tolerances
03-26-2009, 09:13 AM #1
DIN ISO 2768 mk tolerances
I have some drawings from Germany that use the DIN 2768 tolerances and I am having trouble understanding it correctly. I do not have a full copy of the DIN but I do have some notes and a brief discription of how the tolerances are supposed to work but I still dont quite understand it.
The parts are shafts and couplings and have to fit bearings so I know some of the tolerances are going to be plus and some are minus. Could anyone offer a simpler explaination of what I am seeing.
One of the external shafts has a f9 while most of the other shafts have a h9 or h6. A keyway has a N9 and the internal keyway has a j59. One of the internal bores has a M6. Most of the tolerances use lower case but some are upper case, I dont know if that makes a difference or not.
Anyone know of a source for a simpler explaination of these that is in english?
03-26-2009, 09:19 AM #2
The internal bore with M6 sounds like it`s threaded M6 x 1.0 pitch.
Are the other tolerances not in Machinery Handbook?
03-26-2009, 11:51 AM #3
A bearing catalog will have a table with the tolerances. You can also find everything you should need here at this link
Basically, a small letter is the tolerance for a shaft and a captial letter is the tolerance for the hole. The M6 is the tolerance for that bore and is not a thread designation. The tables write the tolerance in micrometers, or the number given / 1000 is the tolerance in mm.
Last edited by MBensema; 03-26-2009 at 11:53 AM. Reason: clarified info
03-26-2009, 01:19 PM #4
about the din 2768 i think its a standart in europe over here
can give you a ling to the table with all the seizes but its a dutch chart but i cant look it up atm but basicly its
and so forth
the h6 is for a schaft for example 25.4mm h6 would mean 25.4mm-25.387mm
if you pm me the seizes you want to know i can give you the dimensions in metric later this evening.
03-26-2009, 06:44 PM #5
Thank you for that link, it doesnt offer everything I need but it does come closer than I had gotten by myself.
I do have a shaft dimention that is not on the chart, it is for an OD 12mm h9. The chart skips over h9 for some reason. The other end of the shaft is 10mm h6 which should be +0,-.009 if I read the chart correctly.
03-26-2009, 07:20 PM #6
I sent you a pm,
03-26-2009, 07:34 PM #7
The chart skips over h9 for some reason.
h9 is in my version of the Machinery’s handbook (21st, page 1561)
Its telling me 11.957 / 12.000 It would pay to check that with one of the other members.
This link often gets put up with questions about ISO tolerance. That doesn’t include h9 either.
The same MHB, gives me a slight difference to your h6. It gives +0 / -0.011 or 11.989 / 12.000
03-26-2009, 08:59 PM #8
Yes I got that too, but there are a lot of other tolerances that are not listed in my handbook. I just need to find a better source and I am hoping to not have to buy all the standards if I dont have too. I am just quoting the job and I am still waiting on some answers from the company I got the drawings from. I thought I could get a head start and educate myself at the same time.
One shaft has a dim 25mm f9, a bore is marked M6 and to me that seems super tight, more than the part requires but I am hoping I just read the chart wrong. There are keyways and snap ring grooves and I just cant seem to find all the information I was hoping for in the MHB but I will keep searching.
03-26-2009, 09:28 PM #9
you have some weird tolerances on there, those are very rare for bearing fits.
I have an ISO Tolerance book my company published, but it looks like it is not available any longer.
12mm h9 +0 / -43
25mm f9 -20 / -72
10mm h6 +0 / -9
Is the M6 hole tolerance also 25mm? If so, it would be -4 / -17
By the way, DIN 2768mk is a general tolerance table that provides the tolerances for anything that is not toleranced on the drawing, it does not refer to the diameter tolerances you are asking about. You can find info on the DIN 2768 at the link below.
03-26-2009, 09:45 PM #10
I just found the tolerances on the keyway, and no the M6 is on a 47mm bore which makes me wonder why so tight a tolerance, I was hoping I was reading it wrong. I didnt see where you got the -17 from, at least that would allow me to have a little more room to work.
On the 12mm my MHB must have a typo because it says the tolerance is +43 -0? I didnt think that correct for a shaft but that is what is in my book. Now you know why I wanted to ask others, this doesnt really add up.
I really do need some reference that I can point to for these just in case there is any problem I need some printed version of these tolerances. I will check out the general one you mentioned.
03-26-2009, 11:18 PM #11
bearing tolerances are usually fairly tight since that controls the amount of internal clearance of the rolling elements to the race of the bearing when installed.
An M6 tolerance on a 47mm bore should be -4 to -20 according to my book. I'm using a book published by FAG Bearings that lists the complete tolerance range for each designation, I don't have my Machinerys Handbook here to check and see what is in there.
The +43 on the h9 tolerance is definitely wrong, all the h tolerances are +0 and a negative number. Are you sure you are not looking at H tolerance tables? The capital H is for holes and all of those are 0 to a plus number.
After you have used it a bit, these tolerances get easier. I wish I had a copy of the complete tables I could email you, the following link is mounting and dismounting catalog that has tables in the back, but does not have all of what you are looking for.
If I find some time tomorrow, I will see if I can scan my tables and send them to you.
03-27-2009, 09:32 AM #12
Thank you all for your help, this has been quite an education so far but it does seem to follow a pattern and I am glad I have decided to follow up with it. Your help at least lets me know where I was right and where I need to work a little harder.
If anyone knows of a techical reference that might be more inclusive and useful I will gladly pay a little for the effort to copy and email or mail it to me. I was thinking of a Text book? Something some engineer in training might use or perhaps a machining student might have access to? I have several booklets on GDT and similar subjects but nothing on the european or DIN standards. Even if it was in German I could work with the tables or have one or two locals translate for me.
Thanks to all
03-27-2009, 09:50 AM #13
the first one is for the shaft toleranties (normal letters)
the 2nd one is for borings capital letters
you can either download them or watch them online and its free
http://www.zyxtek.se/iso2768_eng.htm gives you a table with the tolerances
devided in 4 catagories
m= mediuml work and this is the one you need to see since you need the iso 2768 mk
c= course work
v= very course work
03-27-2009, 09:27 PM #14