Thread Specification

Why are you asking us? You should either be asking the engineers/designers of your company that specified this precision part if the burr is critical. It also matters if this is a truly unique piece, one of a lot of 1000 pieces, all of a lot of 1000 pieces or a sample lot that have an excessive number of possible defective lengths.

The engineers feel that that area is not strong enough to call it part of the functional screw. I stated that the print did not say if the burr was acceptable or not. Is there any standards that cover this area of the screw? I could not find any. We are talking 25,000 screws all the same. I am trying to find out if we have any recourse for return of the screws or is our lack of detail going to bite us.

Well if your engineers did not specify any military or ASME code that limits the dimensions to the range you wish for the size of a burr, then you're just out of luck. What you contracted to purchase and what will properly work in your system is in your paperwork in front of you and not in front of me.

If you insist though you can reference the ASCII code of 65 115 115 104 111 108 101 to your employer as a possible ground for immediate action.

I'd call it an undefined feature.

Without seeing all the drawing notes, it's hard to say.

If it is outside the OA length tolerance, you may have a case.

What does the supplier say?

Are there any statements on the drawings such as:

Per the requirements of..................

Meets the requirements of..............

In accordance with................

As specified in.......................

that would invoke requirements of any specification?

How about Machinery's Handbook?

OK, can you show us a photo of the screw?

Is this supplier, "off shore"?

Would a reasonable person have shipped the screws with an obvious potential defect?

I guess the question could be, did you go with the lowest quoted price?

"My print did not call for the end to be flat or de-burred" - think you've shot yourself in the foot, then. In fact, you left it open for all parts to be 0.050 under, with 0.050 burrs.

I would say without actually seeing the drawing and notes, and the fact that you say "special" 4-40 2A flat head screw, the drawing or print that you provided would take precedence over any screw thread standard, unless you tied your specification/drawing specifically to a standard. That being said, if you specified a specific O.A.L. tolerance of (+ or -) .010 and the screws are .010 over the maximum length specified, they do not meet the drawing requirements. By "special", are you referring to the pitch diameter or the length of thread engagement? If so, that would not have ant effect on O.A.L.

Your drawing stated that the length of the thread needed to be within .010 which is less than half a thread for a 4-40 screw at maximum material for your tolerance. According to your information this is not a reference to the overall length of the screw, apparently that is what your company is expecting, but the length of thread. Is that usable full form thread or from the bottom of the flat head to the very end of the screw?

Perhaps the batch of screws you recieved missed an additional step the manufacturing company intened to finish the end of the screw to the final length.

Its a fastener mass produced. Your drawing called for a 2A and perhaps if you went to a 3A you may get closer results.

With out knowing the application that these screws are intened for, I am having a hard time understanding the realistic need for .010 total tolerance for the thread length on a 4-40 screw and the mating part/aplication that may even be toleranced tighter.

In your specifications/quality requirements do you specify room/part temperature and range, length of time for part normalization, method of inspection?

I thank all for the input. Especially bigg for the reference. A costly lesson has been learned and the drawing has been updated.

I would agree, "Machine screws normally have plain sheared ends but when specified may have header points as shown above." as referenced by bigg pretty well sums it up. Not specified, not performed.

I will do the customary thing and hit the Rate button in his post #7 and vote GA.

"it appears the manufacturer rolled the thread." Thus explaining why the thread form over rolls the sheared end. I believe that if you specified cut threads the thread would not extend past the end. Milo