Performax/Jet 10- 20 Design Problem

Next over to the Pedestal drill to complete machining on this part.
PICT0033-3.jpg

And after a little fettling here's the completed part.
PICT0039-4.jpg
 
I ran into a problem with this job...I made a cast iron threaded bush i tapped it out in the lathe at 9/16 UNF 18 TPI but the spindle was a loose fit when I screwed it in with about 10 thou slop ....not good enough for this project..I searched the web and looked at all the thread form charts on the planet..but the only standard thread sizes close to this spindle were 1/4 NPS and 9/16 UNF..NPS was slightly too small and UNF too large..So the only conclusion that I could come to was that this spindle was undersize and Pete and I got some from a bad batch in our machines..and thats what most likely caused the problem in the first place.
So i fixed the problem by slitting the bush with the saw and adding a couple of adjusting screws to squeeze it in a bit.
PICT0012-6.jpg

Next job was to saw off the stripped lug.
PICT0019-5.jpg

PICT0022-4.jpg
 
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Next i did a trial fit on the sander..I fitted the new bit first complete with spindle...it fitted together very easily (note magnet to keep all the screws from getting lost during assembly)
PICT0025-1.jpg


Then I added the (now lugless) arm and bolted it in place with some longer 1/4" UNC screws through the top two holes of the motor mount slide into the arm..then I wound the rise and fall handle up and down a few times and it worked fine...nice and smooth just like it should...But when i wound it to the top it would not go all the way, due to a foul up with a lug sticking out on the top beam, that I had overlooked.
PICT0028-1.jpg

No big problem I just machined a bit off and tried it again.
And thats about it, up and running again, it should last for years and years..I'll start on Petes parts now that I know whats what..only i'll make his a slightly diferent way, due the the thread size problem.
And i'll profile the new bit so it blends in better with the design.
here is a view from the rear of the sander
PICT0035-5.jpg

And finally a pic of the finished job
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Great documentation of the fix Ken.

I've got one of these too, and like most others ran out to check if mine was going to fail on me any time soon. Couldn't see any problem at all, so as you said, it's probably a batch of mismatched parts that caused the problem in some machines.
 
That's an amazing repair Ken. I'm glad the replacement part for my 16/32 is cheap enough to just replace it. Mine has developed almost 1/4 turn of slop in the screw. You might be finding a lot of 10/20s showing up on your doorstep!
 
Looks about 100,000,000 times stronger and better than the original. I'll be taking this thread down to the machine shop if my 10/20 ever fails. Thanks Ken.
 
I have to say this will come in handy if the one I get fails. Thanks for your work and you will be the first I ask if i have a failure.
 
Interesting diversion for those who read it. Am champing at the bit now Ken has solved the problem. Good job production work has been on hold this week :)
 
Has something been going on while i've been busy in the shed???????
Anyway..GOOD news.

PETES JOB IS DONE
It will be in the post tomorrow :cheers: and it's a posher job than mine. (I put the micrometer in the picture to look more technical):eek:
PICT0003-19.jpg


Petes new bit looked better than mine, so I modified mine as well to match his...this is what it looks like now.
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I believe undersized spindles is the problem.. co's half the thread is still there..I put the 9/16 UNF tap down what was left of the lug just by hand (No tap wrench) and it hardly removed any material and fitted the outer diameter of the thread nicely...so if you ever have to get a new arm supplied under warranty make sure you get a new good fitting spindle with it.. co's if you use the old one it will just strip again :(
 
I thought Jet was a Swiss brand. And that they'd use mm threads. But I'm rubbish at these codes, maybe UNF is European. An Italian motorbike I once had used, and this is rather close to the truth, a different thread on each fecking screw. Made me bonkers. But I still miss that bike.
 
Sven said:
I thought Jet was a Swiss brand. And that they'd use mm threads. But I'm rubbish at these codes, maybe UNF is European. An Italian motorbike I once had used, and this is rather close to the truth, a different thread on each fecking screw. Made me bonkers. But I still miss that bike.
Click to expand...
Svens Bike folks. :rolleyes:
svenbike.jpg
 
Thank You

How many other places have resources so freely shared, so professionally thorough, so accepting of beginners, so welcoming of professional difference? Thank you, Ken, as a prime representative of the larger group that I also thank.
 
How many other places have resources so freely shared, so professionally thorough, so accepting of beginners, so welcoming of professional difference? Thank you, Ken, as a prime representative of the larger group that I also thank.
Click to expand...

Well said. +1.
 
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