What are the odds of getting two bad arbors?

WobblyHand

WobblyHand

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So I received a poorly made saw arbor from McMaster. After reporting this to McMaster, they sent me another SA-1000 arbor. It has the same problem! The screw hole in the arbor is not in the center. The first arbor screw hole had a TIR of 0.036". I haven't yet measured the second arbor. Just like in the first arbor, the second arbor's SHCS jams against the counterbore of the arbor cap. This causes the arbor cap to no longer to be square to the arbor critical surface.

I don't want to keep bothering McMaster, when it is Sierra American's quality problem. McMaster sent me this replacement arbor at no charge. I received the replacement in one day! Too bad it is not a good part.

I'd like companies like Sierra American to survive, but they won't if they continue to ship junk. I think I will end up contacting them to complain. I know I can fix this by boring a hole in the right place and putting in a larger screw, but I shouldn't have to, especially a product that is selling for over $50. The second arbor as received did not have the screw seated fully. It couldn't be seated, because it was jammed against the counterbore. I would think the screw should go freely in until the cap is firmly seated against the arbor. Is it possible this is a valid design element? I did measure the TIR of the saw mating surface on the first arbor, and it meets the product specification.

Don't know what my approach will be with Sierra American. For that matter, don't know what to say to McMaster. I'm not mad at McMaster. It's not good for McMaster to stock crap product. Have to say, I am disappointed with Sierra American.

Anyone have some insightful feedback? What would you do?
 
Do you have pin gauges? I’d find a pin that fits the threaded hole and then check the runout. Checking with the screw compounds any problems.
What happens if you put a standard bolt in? Eliminate the counterbore does it solve the problem? Chuck the cap in the lathe and check mounting hole to OD contricity.
 
Open up the CBore ? Can you post a pic of this arbor also ?
 
I can post a picture in a little while. Good experiments. Don't have pin gauges. Maybe I can turn a pin to fit.
 

What are the odds of getting two bad arbors?​


I would think the odds would not be great , kinda like the Orioles winning the World Series . But , maybe the 2 came off the same run with a set-up issue . I just can't figure out how it was machined so far out of concentricity . :dunno:
 
Nothing readily fits well. But the hole is between an H drill and an I drill. I drill is too large by a little bit.
 
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.
 
These arbors are probably from the same lot. With the original arbor I tried a different screw and the head of the SHCS is eccentric with the cap counterbore. Both arbors seem to be made the same. Tomorrow I will turn a pin to fit the hole. The original cap measures 0.996".
 
Contact both companies and explain that a lot of members are watching !
 
CNCs make parts quickly , both good and bad . Have to wonder how QC didn't pick up the issue .
 
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