Scratches

[banaari]

With regard to notch sensitivity - what counts as a "serious" scratch in 6061-T6?
Does sanding/polishing out remove the problem?
And recommended methods?


cheers,
John

[gyropilot]

John,

Your question really can't be easily answered because you didn't supply all the variables needed, and even if you did, any answers you did get would be a guess! A qualified engineer could spend hours doing stress analysis on a single part / scratch.

In general, deep scratches... stress risers... are to be avoided in all critical parts, because of the possibility of eventual cracking.

Scratches can be smoothed out by any number means depending on the location and depth. On aluminum I use 2" diameter 3M Scotchbrite Rol-Loc deburring wheels on an air-powered angle head die grinder. They come in course to fine abrasive levels, and work very well... not to mention fast. I start with the least abrasive level needed to adequately blend out the scratch.

Obviously if a deep scratch is in a critical part... like a mast tube for example... it would be best to go ahead and replace the part rather than significantly reduce the material thickness of the part while trying to blend out the scratch, thus weakening the part.

It's all a judgment call... when in doubt, you can't go wrong just replacing something. On the other hand, many parts are so over engineered to start with, and little material removed off the surface isn't going to matter.

Regards,

John L.

[banaari]

Scratch is (was, it's almost gone with reasonably light polishing) in the flat surface of one of the seat braces. I think it looked far worse than it actually was. Am now fairly certain I can get rid of the remains with no meaningful loss of material.

many thanks :)
John

[birdy]

Hell,if I polished all the scratches outa my ferel,there'd be no material left. :eek: :o

I gota hand it to you blokes,you certainly keep very clean machines ;) ,I don't know how you fly without git'n a BIT dirty. :confused: