What are the odds of getting two bad arbors?

[WobblyHand]

McMaster is usually pretty good and Sierra I've not had a problem BUT getting two in a row Yeah that isn't that uncommon anymore because of batch purchasing at our suppliers. A bad run is a bad run. I expect either of these companies will make it right for you but it is of course frustrating as you no what in the meantime.

Has to be a bad run. I will contact both places. Sierra American should be informed of a bad lot. I still need to do some more measurements, but one thing for certain, the screw head contacts the counterbore, in both cases. I don't think it should.

 

[WobblyHand]

CNCs make parts quickly , both good and bad . Have to wonder how QC didn't pick up the issue .

This is really the fundamental issue. QC let the product ship. Or they were told to ship it...

 

[Jim F]

Make your own, that way QC is on you........
I have made 3 so far, need to make another when the weather co-operates.....

 

[mmcmdl]

Make your own, that way QC is on you........

I made a few , the runout was over .050 ! JK
I went ahead and bought the Sierras and am ahead of the game ! JK, again .

 

[WobblyHand]

I made one, and had boring issues, never got it to be right. Furthermore, managed to make a part that I couldn't figure out how to hold any more to machine it. Was a learning experience.

 

[WobblyHand]

Ok, some pictures. This is arbor #2. Arbor #1 is still in a collet on my lathe. As you can see, I haven't even cleaned it.

Screw will not go to bottom of counterbore because it is hitting the CB from 12 o'clock to 4 o'clock. Tightening cap causes cap to tilt and lift. Screw head jams against counterbore. The shadow on seen from 5 o'clock to 12 o'clock is the eccentric counterbore.

If I can clean up the bottom and it appears flat, I could make a shouldered pin with threads and I could indicate off the smooth part of the pin. Kind of like a shoulder bolt without a head. Or I could try to make a tight fitting pin to register against the threads and indicate the pin. I also can measure the TIR of the arbor cap, the screw hole and counterbore.

The issue is not how to fix this. I could fix this arbor. And I could fix arbor #1. It is more of what is wrong, so I can pass that along to the manufacturer.

 

[Jim F]

I made one, and had boring issues, never got it to be right. Furthermore, managed to make a part that I couldn't figure out how to hold any more to machine it. Was a learning experience.

same principle.

 

[WobblyHand]

same principle.

I have seen Joe Pie's video. Doesn't matter, still have a door stop that makes me irritated when I see it.

These youtube guys make everything look easy, when it is easy only when you know what you are doing. I am not there yet. Getting there, but not there.

All that said, I may try again, but making an arbor is not the subject of this thread. This thread is about receiving two bad arbors and determining what is wrong. And maybe informing the distributor and manufacturer of the arbors.

 

[ErichKeane]

Is it only the counterbore that is off-center, or is the hole for the bolt off center too? If the former, I'd just widen the counter-bore to give the bolt clearance. A too-large counterbore isn't going to cause a problem until it gets really big.

If the bolt hole is too large, you might get away with enbiggening it too, as long as you don't have to make it big that the bolt head goes through it (though even THAT could be fixed with a washer).

 

[WobblyHand]

Make your own, that way QC is on you........
I have made 3 so far, need to make another when the weather co-operates.....

Some time, I will do that. My first one was a failure. I really am not quite sure what went wrong. All I know is I hit the cap dimensions "perfectly" and the saw just fits. But the cap interferes when inserting part way into the arbor, and I couldn't figure out where it is hitting. I strongly suspect a boring issue, or even a taper issue. At the time, I was not proficient or knowledgeable enough to determine the problem.