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Keyway question ???

rockfish

Titanium
Joined
Aug 27, 2006
Location
Munith, Michigan
If the relationship of a keyway to any outside features is required, should it be stated on the print, or just drawn that way ???


I have some parts with a keyway drawn on centerline at the bottom of the bore. There are some tapped holes on the face of the part, drawn 50 degrees from the centerline. We machined all of the features and sent the parts out to broach the key. Because the relationship was not specified, my vendor simply eyeballed the key.
My customer is now rejecting the parts, because they say they aren't to print. They say that because the key is called out to be central and that the tapped holes are called out 50 degrees from the same centerline, that it is already spelled out on the print. I disagree.




Frank
 
I hate to say it but he is correct, if it specifies 50 degrees then it needs to be 50 degrees. That should have been resolved in the quoting process as far as I'm concerned. And the customer is never wrong! :D
 
The customer is always right Frank (even if their print is wrong)
IMO if the keyway is just put anywhere the part doesn't look very professional, even if it would still work.
It's a poor effort by your broaching crowd.
Make them again and get the broaching done before you drill & tap. No big deal.
 
See........there's the rub. The 50 degrees is held to the centerline of the part. The key is central to the part. That is what is specified. Nowhere does it specify that the key must be on the same centerline, if you follow what I'm saying.

I didn't resolve it, because it wasn't an issue. I have never worked on a part that, if the relationship was "key", that it wasn't specified as so. I assumed, as usual, that the key location wasn't critical, as it's not called out as so.
 
The customer may always be right...........but if I keep chucking out $200 parts in the trash, it won't much matter to me how right he is while I'm in bankruptcy. I simply can't afford to keep throwing shit away because their drawings are poor.

It takes a BUNCH more time to get that lined up perfectly. If it needs to be so, I can understand that, but if not, why take the time ???





Frank
 
The customer may always be right...........but if I keep chucking out $200 parts in the trash, it won't much matter to me how right he is while I'm in bankruptcy. I simply can't afford to keep throwing shit away because their drawings are poor.

It takes a BUNCH more time to get that lined up perfectly. If it needs to be so, I can understand that, but if not, why take the time ???





Frank

Ask the engineer which ASME reference is applied to his drawing.
 
That one has caught so many people before.

Sadly, from my experience... they're right. A lot of products I make for a customer have keys and they nearly all require to be at the proper relation for the assembly of many of the same parts that stack together each with a key. A lot of the drawings don't have a proper note on them saying its critical, but it is, and I remember hundreds of parts made by other shops being scrapped because of it.
Now there are of course many instances where stuff just gets drawn that way cause you gotta put it somewhere and orientation shouldn't matter, but if they're being picky about it they might well have a reason that it needed to be 50°. If they they're rejecting them just cause they're off a bit and it does nothing for the function, then they're just being a PITA.

Oh and the more outside processes you use, the more problems like this you're gonna have.
 
Was the part drawn with different views? If it was drawn with the holes 50 degrees from the center line and the center line shoots through the key then it's implied and doesn't need to be stated. We have a very strict inspection department and we get our balls busted on everything so that would have been my first question when planning the job. I feel your pain Frank but at this point sounds like you need to re make the parts or lose a customer and possible more through word of mouth.
 
They aren't necessarily being picky. They called their customer, and it IS required. Back to my point though, the print is wrong and they refuse to accept that, nor will they go to their customer and point out that the print should be changed. A relationship that is required MUST BE SPECIFIED, otherwise it is just implied. So...if their print is wrong, why should it be my responsibility to remake the parts at MY cost ??? Why would I want to keep a customer that refuses to admit that their print is wrong ??? This isn't the first time that they have refused to admit that their prints suck.



Frank
 
If the relationship of a keyway to any outside features is required, should it be stated on the print, or just drawn that way ???


I have some parts with a keyway drawn on centerline at the bottom of the bore. There are some tapped holes on the face of the part, drawn 50 degrees from the centerline. We machined all of the features and sent the parts out to broach the key. Because the relationship was not specified, my vendor simply eyeballed the key.
My customer is now rejecting the parts, because they say they aren't to print. They say that because the key is called out to be central and that the tapped holes are called out 50 degrees from the same centerline, that it is already spelled out on the print. I disagree.

Frank

To me this is pretty obvious that they wanted the relationship of the keyway to the holes held true to form. This is how I would have done it even though it may not have been obvious to you. This issue could have been averted with a phone call in the quoting stage.
 
I don't think the print is wrong.
If there's 2 holes shown at the same angle each side of the centre line and the keyway is shown on centre line then it's implied that there's a relationship.
You said the broacher "simply eyeballed the key", so he moved the hub around until he thought the 2 holes were in line. If it didn't matter why did he bother.
You should be pissed with the broacher not the customer.
 
The only thing that matters now is how fast you make them 2 new ones that are bang on, and don't get caught twice. A pissing match with them will not solve the problem or get you any money no matter who is right or wrong.
 
Well.......... so far I'm in the minority here. I'm not pissed at my vendor, because he and I both believe that just drawing the keyway perpendicular to the part center doesn't mean that it's required without a callout that the relationship must be held. That's the way it's been done on every single print I've ever seen.......... until now.
I also called around and asked a few of my customers and a few friends that own shops, and they all agreed with my interpretation as well. My vendor is a gear manufacturer, so he does a TON of keys, and unless the print specifies that the gear teeth need to be tied to the keyway in some way, it is always assumed that the relationship to the keyway is not important, even though the keyway will almost always be drawn perpendicular to the centerline. It is simply drawn on the bottom of the bore, and perpendicular to the centerline because that's the easiest way of drawing the feature.




Frank
 
Frank Hi,
You need to be a pain in your customers ass about making absolutly clear what is expeted of your finished parts since this perticulure customer does not understand mechanical drawing asme style. This is the future of producing machined parts in the U.S.A. Good luck Frank. Stpwade.
 
Based on what you described, I'd say they adequately specified the relationship and no further note was required. If, instead of showing the part as they did, they'd drawn it just the same but just showed the two holes were 100* apart, rather than 50* each, then you'd be right that there was no specification of the relationship between the keyway and the holes.
 
So........given your take on this. If a gear drawing shows one of the teeth in line with the internal keyway, then that tooth must be held in relationship with the key ??? The answer to that is, NO, unless it is specified that the relationship must be held. You would be spending a whole lot of extra time and set up trying to line up a feature that didn't mean shit.
I guess you fellas learned how to read blue prints a whole lot differently than I did.



Frank
 
I think the moral of the story is, "When in doubt, make a note". If it's ambiguous, specify to avoid confusion.

That way you don't get into existentialist debates with your machine shops about what came first, the centre line or the key way.
 
rockfish;

I agree with you completely. I work at a large gear company and we do a ton of keyways.

Normally when they autocad drawings it is just lined up center.. the only time we waste time dialing the part in so the keyways are timed with the other features if there is a note on the drawing specificying the keyway to be timed to say a bolt circle, ect.

Thats the way we've always done it at least.
 
I spent a few years in a gear shop, then moved on to a machine tool manufacturer. Both places, if a key location was critical, it was spelled out as such. Otherwise, it was eyeballed and broached. All keys were drawn on the centerline, regardless if they mattered or not. End of story.



Frank
 
I don't suppose you're able to share a pic/pdf of the print here?

If you could, I'd be really interested. We make parts where the key location is relative to external features on a regular basis, but since we do it all in house I don't rely on prints to state so. I trained the guy broaching the key and he knows where I want it ;). The other reason I'm curious is because I'm trying to work through the ASME Y14.5 2009 dimensioning standards right now. I'd love to see how your customer called out the dims. Not taking sides, just curious because we do similar stuff.
 








 
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