The Shop > Finishing

Parkerising technique

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redshift:
While the cat's away!!!. I have the brew on as I write.
Will know in 20 -30 mins if it worked and will measure any increase in size when it has cooled.
Regards
Dave

redshift:
Managed to finish the first experiment before she got home, the kitchen was sparkling, here is what I finished up with:-




I was somewhat disappointed with the result
1) the colour was lighter than I had expected
2) the finish on the parkerized areas was worse than before the job was started.

 In answer to the question of changes in size before and after here are the measurements and how they were arrived at. I used a reamer which was covered in surface rust and de rusted it in Citric acid and then glass bead blasted it to a clean finish, I then masked part of the parallel shank above the cutting head. The shank measured perfectly parallel as you would expect.
After Parkerizing the masking was removed and the shank was measured.
Here are the results:-

Parkerised diameter... 13.732 mm
Untreated diameter.... 13.758 mm
So in a nutshell, it was opposite to what was expected.
Also if you look carefully, (click on picture), you will see some markings along the length of the teated section these are fine grooves that can be felt with a finger nail. What's all that about as they are not present on the untreated area.

I'll leave it at that for now and have a think before I do some more experimenting
Regards
Dave.

awemawson:
Those are grain lines showing up as effectively the part has been etched. At least it confirms that the grain in the steel lies in the right direction! Possibly a forging to start with before machining, but that could also be grain from a drawing out process.

Andrew

redshift:
Here we go with the second attempt. Andrew put the idea in my head that I probably had used too much acid and had caused the surface
finish problems so I reduced the acid content to 60 : 1 ie. 50cc of acid in 3 litres of water. This was mixed over 5 tea spoons of manganese dioxide and a piece of steel wool about 100mm x 25mm x 20mm. (not very scientific I know but it will do for now).
After a bit of internet reading I decided to let the acid dissolve the steel wool before heating the mixture, after a few mins. fizzing all the steel wool had vanished and the mixture was heated to a simmering/boil.
The parts were dropped in and 20 mins. later were removed and rinsed in hot water.
Result, A lot blacker than last time but still a change to the original surface finish, this time the finish was about equivalent to 600 wet and dry using the thumb nail test.
So at this stage I am thinking less acid in the mixture will have less of an etching effect and may help to preserve the original surface finish.
One question before tomorrow's experiments, are twist drills parkerised?
Regards
Dave

vtsteam:
Thanks for these experiments redshift. The photos are really good. Following with great interest!  :thumbup: :beer:

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