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Machine PDM30 table nut stripped

Machine
trlvn

trlvn

Ultra Member
Brian H said:
the lead screw/table nut and all is piss wobbly slack (the nut will almost slide over the lead screw).
Click to expand...
The threads on the lead screw don't look bad in your picture. That only leaves the threads in the nut as the problem.

Is it possible that the factory screwed up machining the threads in the nut casting? Or that it was a bad casting--maybe maybe a sloppy core or voids or whatever?

The King page does say that there is a 2 year limited warranty. I would hope that King will put things right.

Craig
 
Brian H

Brian H

Super User
UPDATE--So, after close inspection, I discovered that the lead screw has a few long "scrape/gouge" marks along the threads. It appears this is what has caused the premature failure of the lead screw nut.
I am assuming this took place during the manufacture/assembly process, however, any suggestions as to what to look for so I won't have to deal with this again would be appreciated. I don't see anything I would blame during all the clean up after disassembly, but, I am a newbie...
I have contacted King Canada and they will be sending me the new parts I need.
 
YYCHM

YYCHM

(Craig)
Premium Member
Brian H said:
UPDATE--So, after close inspection, I discovered that the lead screw has a few long "scrape/gouge" marks along the threads. It appears this is what has caused the premature failure of the lead screw nut.
I am assuming this took place during the manufacture/assembly process, however, any suggestions as to what to look for so I won't have to deal with this again would be appreciated. I don't see anything I would blame during all the clean up after disassembly, but, I am a newbie...
I have contacted King Canada and they will be sending me the new parts I need.
Click to expand...

Post pictures of the lead screw blemish please.....
 
Brian H

Brian H

Super User
YYCHM said:
That doesn't look bad enough to chew up the nut..... IMHO.
Click to expand...
I have to agree with your thoughts, but I can't see any other imperfections or reasons why it would completely strip the threads on the nut either. If you rotate the lead screw in your hand it feels just like a coarse file would. I feel that as that is pulling the table along the pressure on the edge chewed the threads out.
Can you suggest any other areas I should be looking at?
 
YYCHM

YYCHM

(Craig)
Premium Member
Brian H said:
Can you suggest any other areas I should be looking at?
Click to expand...

No, not really. I guess if it feels raspy in your hand then it may very well be the culprit.

How much is the replacement screw and nut costing you?
 
Brian H

Brian H

Super User
UPDATE:
I received the new lead screw from King today. All I can say is WOW, QC is slipping, this is as rough as a coarse rasp. I'm going to attempt to polish it in my little lathe.
Should I try to find a die to clean this up or just send back/reorder???
I have to say I'm a bit disappointed...

EDIT: I just looked, a 1"-10 tpi die is $107... don't think I'm going that route...

Any suggestions you guys have would really be appreciated.
 

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Proxule

Proxule

Ultra Member
Put some lapping compound in your old nut and shove your new lead-screw into it back and forth a couple of times?

Perhaps ask them if this warrants a partial refund??

gluck
 
D

Downwindtracker2

Well-Known Member
The first thing I would do would be to hit the rod with a knotted wire wheel on a mini-grinder . That will remove the burrs. Next, Only If Needed, I would use Clover valve grinding paste, a lapping compound, and the new nut,powering it back and forth. A hand held drill motor for power, you might need an adpter ? I worked downstream of jobber shop machinists. I'm pretty sure the maintenance head got kick backs so the parts we got required fitting.
 
Susquatch

Susquatch

Ultra Member
Administrator
Moderator
Premium Member
Brian H said:
I received the new lead screw from King today. All I can say is WOW, QC is slipping, this is as rough as a coarse rasp. I'm going to attempt to polish it in my little lathe.
Should I try to find a die to clean this up or just send back/reorder???
I have to say I'm a bit disappointed...

EDIT: I just looked, a 1"-10 tpi die is $107... don't think I'm going that route...

Any suggestions you guys have would really be appreciated.
Click to expand...

Wow Brian......

Ya, I'd send it back along with an objective assessment. As hard as it might be, I'd try to avoid getting nasty.

I'm not in the camp that says to try and repair it. In my mind, that would only happen if I was backed into a tight corner by an angry CFO.

I might try to find an equivalent elsewhere though.
 
F

Former Member

Guest
Couple of comments.

Very light nut on the mill. There is very little material there for wear.

The photo of the original lead screw shows rough outside edge but what condition is the bearing surface, smooth or rough? This is where it is important. Don't forget on this type of thread the outside doesn't (shouldn't) contact. If the outside is rough who cares.

Good luck with the repair.
 
Susquatch

Susquatch

Ultra Member
Administrator
Moderator
Premium Member
Degen said:
The photo of the original lead screw shows rough outside edge but what condition is the bearing surface, smooth or rough? This is where it is important. Don't forget on this type of thread the outside doesn't (shouldn't) contact. If the outside is rough who cares
Click to expand...

@Brian H - Degen makes a VERY good point here. On this type of thread, and this kind of application, the part of the thread that really matters most is the bearing surface where the nut and the shaft bear against each other. If the outside diameter of the shaft bothers you, you can cut off a few thou or even sand it without seriously affecting its performance.

Could you please post a close-up photo of the thread so us back-benchers can see what you see?
 
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