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View Full Version : How many ways to repair a damaged thread







RANGER1
29-12-2014, 09:20 AM
This is just general, not relating to anything specific, but a few examples.

Damaged or bruised thread on screw compressor thrust bearing lock nut thread

Phillips bulls eye thread, maybe a bit corroded or gummed up. Remove but on assembly thread not smooth to assemble after replacing rubber gasket or cleaning.
Very fine thread.

Mycom A or B shaft seal lock nut thread bruised or tight to assemble.

A mild steel bolt & nut tight to assemble.

What are some good methods to repair these back to working order in the field?

HVACRsaurus
29-12-2014, 01:08 PM
i) Threadfile, useful for female threads

ii) Needle File, run it along the (male) thread grooves to restore shape best as possible.

iii) Metal Polish / Valve Grinding Paste, apply liberal quantity & run nut / fitting back & forward, start off slowly & work into thread depth as it loosens up...

RANGER1
29-12-2014, 08:00 PM
i) Threadfile, useful for female threads

ii) Needle File, run it along the (male) thread grooves to restore shape best as possible.

iii) Metal Polish / Valve Grinding Paste, apply liberal quantity & run nut / fitting back & forward, start off slowly & work into thread depth as it loosens up...

Hit the nail on the head.

Had to use the valve grind paste several times last week on old Phillips bulls eyes when installing new glasses.
Never had much luck with high tensile bolts though.
Best to use very fine lapping paste with a bit of kerosene.

Thought it was worth a mention as thread files also not a lot of people know they exist for all different thread pitch sizes.

PaulZ
29-12-2014, 11:05 PM
Another option is a very small 3 corner or triangular file. All metric and UNC and UNF threads are 60 degree thread angle and if you come across Withworth it is 55 degrees, this is only good on male threads.
Have used all the other things mentioned at some time, all good.
Paul

Magoo
30-12-2014, 08:26 AM
Hi Ranger1
a good post

Hemp and brasso is good after the thread file, to clean up male thread. Hemp that fibre stuff old plumbers still use. Hemp rope is also good for polishing crank shafts seal areas and crank big end lobes, add some brasso.
Those Philips bulls eyes threads are right pain to clean up. I have a seriously small brass wire wheel thingo that I put in the battery drill, and of course some brasso.

glenn1340
30-12-2014, 09:59 PM
For cross threaded internal thread cut four slots along the axis of a bolt; this will allow the bolt to act as a tap and with a bit of luck the bolt thread won`t follow the damaged internal as the slots will skip them and pick up on the original pitch. I`ll take a bit of patience and a keen eye to ensure the bolt is running in true but if you`re stuffed on a Saturday night it might just get you out of trouble.
Another idea an old steam loco fitter told me many years ago is if a bolt hole is out of line with a flange etc grind a lead on the bolt as this will enable it to work its way into the internal thread.
While we`re on the subject of bolts how about everyone`s favourite job: removing that sheared off bolt. Ideas anyone?

RANGER1
31-12-2014, 08:10 AM
For cross threaded internal thread cut four slots along the axis of a bolt; this will allow the bolt to act as a tap and with a bit of luck the bolt thread won`t follow the damaged internal as the slots will skip them and pick up on the original pitch. I`ll take a bit of patience and a keen eye to ensure the bolt is running in true but if you`re stuffed on a Saturday night it might just get you out of trouble.
Another idea an old steam loco fitter told me many years ago is if a bolt hole is out of line with a flange etc grind a lead on the bolt as this will enable it to work its way into the internal thread.
While we`re on the subject of bolts how about everyone`s favourite job: removing that sheared off bolt. Ideas anyone?

Glenn,.
Thanks for input
Your question is it in general like with an easy out? give us an example.

MikeHolm
01-01-2015, 04:00 PM
I second the use of hemp. I use it all the time for threads of all types especially to seal 100year old threaded pipes but very useful for cleaning up threads. I think it may still be banned in the USA, though.

glenn1340
02-01-2015, 03:42 PM
Not an Easi out, more if an internal thread is cross threaded. It doesn`t always work but as I said if you`re up sh*t creek it might be the paddle your looking for.

MikeHolm
02-01-2015, 08:35 PM
And for the more common threads, I keep some taps with me and redo it. Don't know how big the one you are dealing with is anyway.

glenn1340
04-01-2015, 04:26 PM
Size of my nuts!11916

monkey spanners
04-01-2015, 05:57 PM
I've cleaned up rusty threads on milk tank legs with a junior hack saw, use the blade angled so as to saw at the side of the thread.

sterl
12-01-2015, 08:07 PM
Piano wire and valve grind compound together for male threads.

Some big female threads quite some time ago: Doctored up a cylinder hone with a die of same pitch....Drove it with a brace, in and out, not terribly fast.

Have a small collection of bottle brushes for smaller female threads. A little penetrating oil and a little lapping compound. Drive with a hand drill with a pin chuck extension.

sterl
12-01-2015, 08:14 PM
And Mike's right about Hemp rope and the US though most of what they call Hemp commercially is not made from that plant, wherever you buy it. Manila is real close and has very similar utility in terms of applying it to threads...