An unfortunate learnt something new lesson

[savarin]

As some will know I have been doing a lot of straight knurling in stainless steel of late.
I use a cam jack knurler to really apply the pressure required to get full depth knurls with no double tracking.
I'm very happy with the results but learnt a valuable lesson unfortunately the hard way the other day.
I wiped the finished knurl along its length with a rag to get a good look at it and all was well untill I picked up another tool whereupon I felt the splinters in my thumb that had gone clean through the rag.
BUT, I couldnt see them or even feel them lightly passing a finger over where I thought they were.
Nope, they hadnt gone, just so fine they couldnt be seen.
Even with a 10x loup I could barely see them, I swear they were finer than prickly pear hairs and even more irritating.
I checked a couple of the finished knurls that still had oil on them and there they were, long but ultra fine hair like swarf sitting in the grooves.
I usually use a very thin oil for lubricating the knurling and I think this flushes the fine swarf out but this time had run out and used a thicker oil.
A good wash got rid of them and the ones in my thumb appear to have eventually worn away.

 

[T Bredehoft]

Fortunate you are that the wires in your thumb didn't stay behind to cause problems.

 

[WCraig]

I've never knurled (is that a proper expression?) but I'd like to know more. I think I saw a video where the presenter brushed the freshly knurled and still rotating part with a stiff brush. I believe this was to knock off any swarf and such splinters. Is this a good approach?

Craig

 

[NortonDommi]

WCraig, yes it's a good idea. I have a short narrow scratch brush that gets run over a fresh knurl running at slow speed then in reverse.
Savarin, #metoo.

 

[savarin]

For cross hatch knurles I usually use a wire wheel running along both diagonals in a drill whilst the part is rotating first one way then the other.
This removes all the sharp edges. I havnt done it to these straight ones this time because they are quite small.
I will do next time.

 

[mmcmdl]

One of my first experiences with stainless splinters was jumping up and sitting on a bench where someone was cleaning up welds with a carbide burr bit and die grinder . You won't make that mistake twice .

 

[cathead]

Have you ever noticed that sometimes a knurl just doesn't cooperate very well? I have found that certain diameters
work better than others. If I am having a problematic knurl, I will machine off a couple thousandths and try again. Usually
it goes better on the second try tracking better and producing a nicer knurl. In theory, knurling is not a machining operation
but rather metal forming.

Savarin, sorry you got the splinters. We have all been there and it isn't much fun. That needely stuff is the worst.

 

[BGHansen]

Savarin,

So glad to hear the outcome was just splinters. I started to cringe when I read "rag" and "knurling", was sure hoping the two didn't meet while the lathe was running. Thanks for the tip on the splinters.

Bruce

 

[Superburban]

Have you ever noticed that sometimes a knurl just doesn't cooperate very well? I have found that certain diameters
work better than others. If I am having a problematic knurl, I will machine off a couple thousandths and try again. Usually
it goes better on the second try tracking better and producing a nicer knurl. In theory, knurling is not a machining operation
but rather metal forming.

Somewhere there is a math formula that takes into account the spacing of the knurling tool, that gives you the best diameter to start with to get a perfect knurl.

 

[Shootymacshootface]

Sometimes you have to wait 2 or 3 days for the splinters to turn black to find them all. I know that you said that you were working with stainless. I would expect that to darken as well, unless it's a higher grade of stainless steel.