Reply With Quotehave also just seen the attached that states +/- 2 degrees. Does that mean hole doesn't ahve to be spot on 90 degrees but anywhere between 88 and 92 is okay?
notes.jpg
Good morning,
Please be advised my knowledge is very limited as I am not a trained engineer. I have had some aluminium parts milled that include a threaded hole as per the attached image (drawing.jpg) taken from the drawing.
However, when I thread a rod into the holes it appears visually not to sit perpendicular to the surface. I have tried checking the 'squareness' by using a square and measuring with a protractor; you can see from the second image (protractor.jpg) that the angle is a few degrees from 90.
The issue I have is that I do not know what tolerance is acceptable and whether I should reject the part or have to accept it; this is because I do not have the skills to imterpret the symbols on the drawing. I told the supplier I think they are out of square and they say they are fine.
Can anyone please advise? E.g. does perpendicular mean perpendicular, or is there astandard acceptable tolerance, e.g. +/- 1 or 2 degrees? Also, how can I accurately measure the perpendicularity of the threaded hole, or is there a company that I can send the parts to to be analysed or a specific instrument that should be employed?
Many thanks for your time.
have also just seen the attached that states +/- 2 degrees. Does that mean hole doesn't ahve to be spot on 90 degrees but anywhere between 88 and 92 is okay?
notes.jpg
Last edited by rbraithwaite; 09-19-2024 at 10:21 AM.
There's so much to unpack here for you - I'll try..
The geometric tolerance specified on the engineering drawing is the final requirement and supersedes the title block. The title block tolerances are when there are no other tolerance specified for a feature or features.
The tolerance specified for that thread only applies to the thread feature within the material - not any feature or part that projecting out of the part.
The method you show is not how that thread is to be measured - the axis of the thread as derived from the pitch cylinder is where the position a tolerance of dia. 0,2 is measured to relative to datums A, B, and C.
You need a dimensional metrologist (Inspection professional) to inspect / measure this for you using either a CMM or even open setups with dial indicators or micro-height.
You appear to way out of element here - you really-really should read up or get training on ASME Y14.5-2018 and/or ISO 1101.
This engineering forum is not where you should attempt to train your self in GD&T or G&T.
Good luck..
Tell me and I forget. Teach me and I remember. Involve me and I learn.
Agree with all that Kelly said. That being said, that photo shows what in my opinion is an excessive amount of "lean". Are you SURE your rod is straight? Frankly it looks like that hole was drilled and tapped by hand rather than on some shop equipment. Not talking about "standards" but I would expect most shops to do a better job than that.
By the way - there is no such thing as a perfectly located threaded hole. That's just the nature of a threaded engagement.
Now, if your goal is to have your rod sit at a near perfect right angle from the mount surface then you should use some means other than threading to assure that.
For example look up "shoulder bolts". They are designed to provide a little more precision in mounting geometry than a typical threaded fastener. That precision comes from the fact that their design pulls a machined flat surface (the bottom of the shoulder section) down tight against another machined flat surface (such as a spotface or counterbore).
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