Problem with press fit plugs

[mtarrant]

The parts I'm making require holes to be plugged. I'm using slightly oversize aluminium plugs, press fitted to the holes. The face is milled and polished. At this stage it is impossible to see the plug. After anodising the plug becomes visible, but when dying the color wont take at the edge of the plug. (See pic).


Possible causes?

1. Metal charateristics altered by the compression effect of the interference fit of the plug.
2. Residue citting oil in the hole leaching out in the hot dye
3. Acid penetrating the seam between plug and body

Anyone have more than a guess as to the cause.

[sswee]

Sorry I can give a definitive answer but I would figure a contamination problem for the dye not to take on the edge. The plug showing after anodize is most likely due to your #1 cause listed. The last parts I did with repair plugs in them showed the outline of the plug after anodize but dyed evenly.