# Emery Cloth And Tolerances



## One-match fire (Feb 6, 2016)

G'day mates,
No, I'm not an Aussie but that greeting has always sounded friendly so....
My question today has to do with emery cloth.
Background:
while attempting to repair a frostproof hydrant out in the barn yard, the plumber I hired used his "vice grip" on the body of the extension rod that connects to the 7 foot rod with the plunger at the bottom of it.  The extension rod is connected to a threaded brass connector on the bottom of it and penetrates what is called the"packing nut" which is a threaded brass bushing on top of the handle of the hydrant. (He also grabbed the threads with the same vice grip but I was able to spin a die on that and clean them up.
He scarred the extension rod and it would NOT pass through the packing nut so I put it on my lathe and took a small piece of coarse emery cloth to polish down that scar.  After about a minute at a pretty moderate speed, I was able to pass the "packing nut" over the rod. The rod passes through two "O"rings between the packing nut and the brass connecter.  
My question is: Did I polish off TOO MUCH with that emery cloth and should I have used a fine grade rather than coarse grade?
The amount of scarring on the rod wasn't all that much but it did prevent passage through the packing nut until I polished it.(It was out of round by a bit in "machinist standards" but not THAT noticeable when assembled in the hydrant.
I am still not good with the tool on the lathe.  I was afraid with the rod out of round like that, the tool would cut deeply on one area and not at all on the other side of the rod. AND my lathe still has a good bit of backlash that I am not all that skilled in getting out so that I can believe a .002 change in depth of the tool.
Any suggestions/comments will be much appreciated.
Cheers,
Trim sends


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## stupoty (Feb 6, 2016)

If it's a packing gland with some sort of rope or compressive seal it should pack down nicely onto the slightly smaller size,  much better than having it not fit.   

Stuart


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## royesses (Feb 6, 2016)

It doesn't sound as though you took too much off the rod. Not having an example to look at makes it tough to judge. For something like that I usually use a smooth cut file to remove the part of the furrow that protrudes from the shaft. Then I use some fine wet or dry paper 400 grit to lightly smooth out the surface. If the surface you repaired has to seal against the o'rings your best test is does it leak? If it works and does not leak you did a good job. Sounds like maybe the plumber needs to be more careful.

On the backlash. Back off your cross slide a turn or more first. Then advance the cross slide to take up the backlash. Use a thin piece of paper or cigarette cellophane as a feller gauge between the tool cutting edge and the part. Advance the cross slide carefully until there is resistance to pulling the paper out. At this point you are very close to the part and if you only turn the cross slide wheel in the same direction (advancing) there is no backlash to worry about. You can then turn the lathe on and place the tool bit where the scar is. If the tool does not touch then advance it until it just barely touches and zero the hand wheel. Now when you take off .001 that is what you should get. Remember that .001 on the hand wheel will remove .002 from the diameter of the part(unless your hand wheel is marked to indicate the amount removed from the diameter. That is how I do it. Takes a heck of a lot of time to explain it, but less than a second to do it. Soon it becomes second nature and no real thought is involved.

Roy


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## RJSakowski (Feb 6, 2016)

If your frost proof hydrants are like ours, the shaft travels a fair distance.  Considering what vise grips can do to a shaft. You probably removed  a fair amount of metal.  If the repaired area doesn't enter the seal area during use, no problem.  If it does and you tighten it down so there is no leak, it may be too tight where you didn't polish the shaft.  The remedy would be to polish the entire seal contact area to the same reduced diameter. 

IMO, you were right not to attempt turning the shaft.  I would have used a file to knock the burr down first and then clean up with the emery cloth as you wouold have less wear on the undamaged surface.


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## mattthemuppet2 (Feb 6, 2016)

you have to really push things with sand paper or emory cloth to take more than a thou or at most 2 off the diameter, at least in my experience, so I doubt you've done any harm. For raised burrs like that I tend to lightly file or stone them off first, that way there's less chance of taking much of the surrounding material off. You can also keep a careful eye on the burr and see when the filed/ stoned area starts to meet the surrounding material.


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## FOMOGO (Feb 6, 2016)

I think you are probably fine, as mentioned above it's pretty hard to to over do on something like that with emery cloth. Calling this guy a plumber is most likely a disservice to real plumbers out there. Hope it all works out for you. Mike


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## derf (Feb 6, 2016)

I guess the real question is ......Does it hold water?


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## kingmt01 (Feb 8, 2016)

Most trades involve replacing parts instead of repairing them. Plumbers 10 years ago cost $60-100 an hour. Those frost proof hydrants cost $60-100 if your hiring the work done I'd rather hire him to replace it then repair it. They don't come apart easy ether. I've repaired a few & they take a while. As much as I hate buying replacement parts when something can be fixed these are one of those things I believe is money well spent to replace.


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## One-match fire (Feb 27, 2016)

The shaft I polished was attached to the main shaft by a coupling that penetrated the handle to activate the hydrant. No water (AFIK) cpmes through that spot ( I could be wrong about that cause they do have those two "O" rings on either side  of the packing nut.  What I didn't mention was the depth of the frost line.  It was over 30" deep.  That is for all intents and purposes, solid rock when you are digging.
Since things did NOT go well that first day, I managed to get a small, tractor mounted backhoe out and start digging  after we noticed that water was  coming up from the bottom now.  The PVC pipe that the hydrant shaft went through, had a frozen spot about 20" thick so things were just freezing at that point and that was why no water was coming up.
The guy who had come to help is a good, indoor plumber, but admits he doesn't know anything about these outdoor items. The guy who DOES know them finally came out late in the day, dug the hole through the frozen soil and by the time he had the hole dug it was dark so we quit till the next day. He came early the next day, got the soil back out of the hole so it wouldn't freeze over night and eventually hand dug down deep so that he could just replace the entire hydrant.  It now works perfectly with the exception of the appearance of a "newly made grave" in front of the building where my hogs live.
Lesson learned: Get the right guy for the job the FIRST time.
The owner of the company is a stand-up guy.  I went to talk to him about the entire thing and he cut the bill in half (the 6 hours posted by the first guy) and I paid him on the spot.
That is one of the advantages of living in a small town and having a reputation for paying your bills "in full, and on time, every time".
Thanks for your help with the emory cloth question.  The .001-.002 I probably took off did not damage to speak of so I guess I got lucky on that one.
Cheers,
Trim sends


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## bandaidmd (Mar 25, 2016)

One-match fire said:


> The shaft I polished was attached to the main shaft by a coupling that penetrated the handle to activate the hydrant. No water (AFIK) cpmes through that spot ( I could be wrong about that cause they do have those two "O" rings on either side  of the packing nut.  What I didn't mention was the depth of the frost line.  It was over 30" deep.  That is for all intents and purposes, solid rock when you are digging.
> Since things did NOT go well that first day, I managed to get a small, tractor mounted backhoe out and start digging  after we noticed that water was  coming up from the bottom now.  The PVC pipe that the hydrant shaft went through, had a frozen spot about 20" thick so things were just freezing at that point and that was why no water was coming up.
> The guy who had come to help is a good, indoor plumber, but admits he doesn't know anything about these outdoor items. The guy who DOES know them finally came out late in the day, dug the hole through the frozen soil and by the time he had the hole dug it was dark so we quit till the next day. He came early the next day, got the soil back out of the hole so it wouldn't freeze over night and eventually hand dug down deep so that he could just replace the entire hydrant.  It now works perfectly with the exception of the appearance of a "newly made grave" in front of the building where my hogs live.
> Lesson learned: Get the right guy for the job the FIRST time.
> ...


here in eastern Maryland we only need 4' frost frees so a lot less digging.


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## One-match fire (Mar 25, 2016)

Spent some time living in Salisbury myself. Seems we have more than one thing in common,eh?


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