Threaded Hole Position Tolerance
Threaded Hole Position Tolerance
(OP)
I am a new engineer and am working on a project and am specifying the location of 3/4" ANSI Standard Hex bolts and need to know how to tolerance the position of the holes with respect to eachother, i.e. I have four bolts in a rectangular pattern. If anyone knows a good source for this type of information I would appreciate it.
Thanks,
Dan
Thanks,
Dan





RE: Threaded Hole Position Tolerance
from the minimum hole diameter and divide
by two. This would be the true position
tolerance on each set of holes. Normally
shops can do better than this and you might
want to tighten up the tolerance. This is
a general guideline.
RE: Threaded Hole Position Tolerance
RE: Threaded Hole Position Tolerance
http://ww
or there might be an answer over at the GD&T forum:
http://www.eng-tips.com/threadminder.cfm?pid=1103
Harold
SW2007 SP2.0 OW2006 SP4.0
www.lumenflow.com
RE: Threaded Hole Position Tolerance
between the holes, .70 times the values
that I mentioned earlier would apply for
a rectangular tolerance. Then use 1/2
of that value for the plus and minus
tolerance value on the dimensions between holes
which would be a rectangular pattern
inside of a circular tolerance.
For example: if the holes were .78 and the
bolt .75 would give you a difference of
.030. True position tolerance would be
.015 and the give you a plus and minus
.0105 on the dimension between holes.
RE: Threaded Hole Position Tolerance
Using bolt size at .75 - min hole at .906 you have .156 to play with. You could then allow +/- .060 positional tolerance and you would still have some margin.
All that being said it also really depends on your industry, who is making the parts on what kind of machines, or is it being drilled in the field etc. Hope this helps.
RE: Threaded Hole Position Tolerance
RE: Threaded Hole Position Tolerance
"For example: if the holes were .78 and the
bolt .75 would give you a difference of
.030. True position tolerance would be
.015.."
This is true only if the holes positions are known with absolute accuracy. However, the holes too has positional errors that should be taken into account when specifying the bolts true position tolerances.
RE: Threaded Hole Position Tolerance
If you want to half ass it (as is standard in many areas of industry) then use some of the other approaches given
More seriously though what type of industry are you in, this will affect which option you take. Try and ask colleagues how your company normally deals with it (do they use GD & T or should they) or at least try and look at other drawings with similar features.
We prepared a table at my place based on information ( a chart) in machineries handbook but modified to suit our purposes.
Looking at our chart for 3/4", for what is termed Normal clearance then for 'floating fasteners' (ie both items just have clearance holes) suggested hole dia is .781 +.010 -.002 with positional tol of diameter .029.
We also have a close clearance for more precise applications. .760 (think it should be .766) +.010 -.002 with .014 pos tol.
I'd take a look at the GD&T forum.
RE: Threaded Hole Position Tolerance
Looking at the title of your post you clearly state threaded hole.
As such assuming you can dimension the other part to suit you need to halve the positional tolerance I gave above.
If you only have control over the threaded item you need to do the calcs explained by others above.
www.draftingzone.com may help.
RE: Threaded Hole Position Tolerance
One way is an indirect method by screwing in bolts/studs with an unthreaded shaft. But if such studs are not perpendicular with the work, it will again lead to inaccurate measurements.
So, do not go too fine.
RE: Threaded Hole Position Tolerance
RE: Threaded Hole Position Tolerance
Thanks again, Dan
RE: Threaded Hole Position Tolerance
Cheers
RE: Threaded Hole Position Tolerance
Get a copy of ANSI Y14.5M and/or an equivalent DoD specification. If you don't put ANY tolerance on the drawing, it doesn't mean that the fab shop can just put it wherever they want...there are standard tolerances.
I teach a class on CAD drawings, but I'm also an engineering consultant. The unfortunate reality is that tolerances are specified however people feel like it most of the time...few follow the "right" procedures. James Earle has an 11th edition of his book Engineering Design Graphics that has a great chapter on tolerances (chapter 21). It may be worth a purchase...
For your hole positional tolerances, you have a symbol (looks like the cross hairs through a scope), a tolerance, an indication of whether you are using "maximum material condition", "least material condition" or something regardless of feature size, you may use a datum plane or two for reference and that would have to be indicated, but all of this is only if it falls outside of the standard tolerances. You need to specify which standard you are following...the fab shop will have to know the standard.
My 2 cents...
Garland
Garland E. Borowski, PE
Borowski Engineering & Analytical Services, Inc.
Lower Alabama SolidWorks Users Group
RE: Threaded Hole Position Tolerance
GBor this isn't my understanding. While certain sections of industry have their standard tols I don't think that would apply here. Even if you reference 14.5 that doesn't actually give any tolerance values. As a minimum you need to either reference a spec which does gove tolerance values or have a 'block' tolerance on the drawing.
RE: Threaded Hole Position Tolerance
RE: Threaded Hole Position Tolerance