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I finished the scissor knurl introduced to us by coal miner. I'll post a video of the build later, in a new topic.
Here is a picture of my very first result in a 1.125" diameter piece of aluminum. To me, it does not look "crisp." What did I do wrong? Not deep enough? Feed to slow? Something else?
Maybe a pin in the tool holder in the center, sticking out to catch the scissors will stop it swinging around and hitting the work, if you run off the end...
Last edited by ctwo on Mon Feb 24, 2014 9:36 pm, edited 1 time in total.
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...
Looks fine, Bill, with the only change I'd make is to make it a full knurl. It's a personal thing with me, as I don't much like flat top knurls, but many don't share my opinion. There is no right or wrong where knurls are concerned, unless otherwise specified.
If you're looking for a full knurl, increase the depth slightly, until the crest of each knurl is to a point. Right now you can see a small flat area on each of them.
If you go too deep, it will usually just continue to create a full knurl, shedding aluminum in the process. It comes off looking like aluminum paint. No harm done, just more time and effort involved, with no benefit.
Harold
Wise people talk because they have something to say. Fools talk because they have to say something.
I'll experiment more tomorrow. Thanks for the "full knurl" advice, Harold. I'll play with power feeding it, as well.
--Bill
In regards to feeding, if you dwell, the knurl will generally get deeper, assuming you have the rolls tightened fully. If you're creating a shallow knurl, that may or may not be true, as the pressure to create a shallow knurl is much lower than one for a full knurl, so it may already have established depth. Power feed tends to provide a more uniform knurl---but use what works for the project at hand.
You may discover that a knurl will have a nicer appearance by feeding a given direction. Or not.
Harold
Wise people talk because they have something to say. Fools talk because they have to say something.
I created a picture-perfect knurl by doing two things differently. First, I brought the axial center line of the scissor knurl up to the axial center line of the lathe spindle. Second, I power-fed at 0.02937" per revolution. (That was a guess based on a PM exchange with Harold and the fact that it was the fastest I could feed without swapping gears.) I decided to make several--or at least two--passes on the piece, although I REALLY liked the fine look of the one-pass effort. (As Harold said, to each his own preference in knurls.) I reversed the direction of the feed, re-engaged the spindle and engaged the power feed. The top knurl on the scissor locked solid! Smushed aluminum!
Thinking about the issue, I realized that the only lubrication I had applied to the knurls was the WD40 used in yesterday's and today's test knurls. I imagine that is why one of them locked.
I pressed the axle of that scissor's knurl out. I could see marks. I built a new axle out of another 1/4" dowel pin. Hmmm. It wouldn't insert completely into the knurl. The bore of the knurl must have also been damaged. Inspecting it, I saw the tiniest mark. Having nothing to lose, I hand reamed it with a 0.2505" reamer. The new axle now fit.
But, it lasted no longer than re-engaging the feed.
That was a $16.95 lesson. A supply of knurls are now on their way from McMaster-Carr. I'll lube them with 3-in-1 oil. Do you have a better suggestion?
I WISH I had taken that picture!!! It really was perfect. (Reminds me of a fish story.) At least I know the scissor knurl I built with coal miner's mentoring works well.
seal killer wrote:That was a $16.95 lesson. A supply of knurls are now on their way from McMaster-Carr. I'll lube them with 3-in-1 oil. Do you have a better suggestion?
Yes. Don't use 3 in 1 oil. Use an oil recognized for heavy loading. While it's not generally considered a great lubricant, I've always just used cutting oil, which has a much heavier body than 3 in 1. I've never had rolls seize---but maybe I've been lucky.
I'm not much of a believer in the claims that WD-40 promotes rust. I've used it in adverse conditions to prevent rust, and it has served perfectly well, assuming a generous coating. My observation indicated that once the solvent had evaporated, there was a film left behind that very much resembled paraffin, which, regardless of what it is, did all I asked of it. However, seeing how little was deposited, and understanding that knurling is demanding of heavy loads, I'd hesitate to think that it would be adequate for lubricating a knurling tool. That was most likely a mistake. If you have nothing else at your disposal, use some Vactra.
Harold
Wise people talk because they have something to say. Fools talk because they have to say something.
Bill,
Knurl Job 
