Spiders

[just bob]

As Halloween approaches it only seems right to discuss spiders. A few years back at a knife show a dealer explained his experience with these hideous creatures to me. Though they appear to be on the surface, but when you start digging them out an area the size of a pin head opens up to an area the size of a thumb tack head. Very hard to get out with sandpaper because they spread. I'll guess the one in the pictures that appears to have legs goes very deep. I worked in a steel factory for 35 years and we had a surface condition on stainless plates that was called slivers that was very similar to spiders. It was a lot more common in stainless grades 309 and 310S than in standard grades like 304. You can find an old knife that is rusted shut and it won't have spiders. This knife is a Case Classic from 1991. What causes the spiders - grade of steel? improper storage? Why do you not see them on older knives?
I had a Case Buffalo knife with only a couple of spiders in the blade and kept working on them with a scotch brite wheel and sandpaper and got it looking good again but it took a lot of work. Has anyone dealt with these and developed a removal method that is easy? Can they be polished out with coarse grits?

[TripleF]

I certainly am no expert but have been sanding/polishing knives now every day for about 6 to 12 months.

I have that exact spider on an old Case knife I began work on today.

Sandpaper is the only tool, mixed with countless strokes of elbow grease, to remove these....that I know of....

When facing that type of rust/pitting/patina I created a word: L.O.S.H. (Loss of steel happens). If you don't take care of it
with sandpaper, it'll only get worse....so L.O.S.H happens EITHER WAY! IMO

[steve99f]

I am interested in the responses to the question of why they occur. I don't think its a question of metal maintenance though. Have no basis for that other than so many people can't be that careless. Right???

[kootenay joe]

Could it be that the steel composition is not uniform throughout ?
kj

[just bob]

I'll relay a story about where I used to work. We had a major customer that bought huge sheets of stainless steel to form into tanks and vats for storage. That customer announced they were dropping us and were going to buy imported steel from China because it was so much cheaper. As it would happen the entire first lot of steel they bought was not within quality standards and had to be scrapped. I suppose the Chinese gave them an adjustment? The company I worked for bought it for scrap price and reprocessed it. A lot of it ran through inspection and it was covered with surface defects we called slivers, which are a lot like spiders on knife blades. The QC guy told me the chemical ranges on the steel were way out of whack. For instance 304 type stainless has 18% chrome and 8% nickel - those alloys are expensive. If you were trying to cut corners you would cut back on these and alter the chemical composition of the steel structure. That didn't happen with us because customers got a chemical analysis with their orders. At that time I suppose you only got the word of the Chinese steel makers that their steel was within specs. I'll bet that has changed. Anyway there are many factors that effect the surface quality of steel; chemistry, annealing, rolling, pre rolling conditioning, are only a few. I wonder if the problem with spiders on knife blades is only on Case products and is it only in certain years? I would like for others to point out spiders on other makers and if there are any on much older knives? I really have only seen these myself on Case knives and only a few knives from the 1970's. The Case Classics seem to be bad for spiders. A lot of these knives were outsourced and who really knows where the steel came from for them? I'd also like to point out this is about spiders only - when you grind them they open up and go deeper into the steel. Many surface defects on steel are not spiders, but pits, rust, corrosion, etc.

[steve99f]

just bob:

Google carbide precipitation and see if that sounds like what you saw in your shop.

[hardman]

I would fully agree with just bob:

I have MUCH more problem with blades on CASE CLASSIC knives than on any other.

I had a small display of knives at my cabin on a lake. I put the knives in the display in late May, and they were there until early October. There is certainly high humidity there. All were fine, except one. A Case Classic 51050L Large Stag Locking Coke Bottle with Swing Guard. It had deveoped several large and serious stains and spiders on the blade in the area covered by the Swing Guard when the blade is closed. I recovered it as best as I can, but it will never be perfect again. This is not the first Case Classic I have had trouble with. Bottom line: it is definitely easy to believe that the steel has something to do with the susceptibility to stain, spider, or pepper spot. And the steel used in the Case Classics from the 1990's is very prone to those problems. By the way, I hold myself fully accountable for the damage to that Coke Bottle. Next year, nothing but stainless steel in that display.

[peanut740]

The Case Classic gunboats were made in house by Case and not Queen.

[Landersknives]

I have a Case XX 9333 and it has spiders on two of the blades. New never been sharpened. Don't have a clue what caused them but they are really bumming me out.

[Bill DeShivs]

It usually happens on mirror polished blades. Rust starts in one spot, and then just spreads. It's not confined to Case knives. Any high polished, high carbon steel blade can get them if not oiled for long periods.