I see the how to drill stainless comes up every couple weeks. Here's a variation.
What's the trick to knurl stainless? I was looking at some dental tools that have a beautiful job and are clearly quite hard. Some other stainless parts I've examined have botched up knurl jobs, but for adding friction for a grip, it's good enough.
I've knurled unhardened steels, brass and aluminum on the Sherline lathe. It's takes a couple passes some times, but there's enough fudge factor where the results are fine. I've not bothered to try stainless, but I suspect the multiple pass trick just isn't going to work at all, especially on a small machine.
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Essentially, knurl it to full depth in two or three revolutions. (think SLOOOOW spindle speed) Otherwise, just like in drilling, it will work- harden, and not move anymore after that.
It helps - a lot - to use a clamping-style knurl. Side-pressure knurls often can't provide enough force to do it cleanly in that few revolutions; at least not without creating some undesirable forces on your cross-feed.
Last I specifically looked for them in MSC, they were significantly over $1000.00 -- and my 12x24" lathe was about the same. Granted, the lathe was from 1957, and the cut style knurl was brand new. :-)
O.K. Made by Dorian, $1,188.82 for one with a size range of
0.75" to 5" diameter workpiece. (Not counting the cutters, of course. :-) And -- a bit larger than my toolpost will handle. (3/4" shank, while I need a 5/8" shank max.)
So -- this would not cut small enough to do the knurling on stainless steel dental picks as per the original question (which typically are hollow for ease of control).
Yes -- I have used a scissors style knurling tool to knurl Stainless Steel -- but that was 416 SS -- a lot more workable than something like 304. :-)
And for hollow handles for dental picks, I think that the crush force would be too great and destroy the workpiece. That is why I suggested cut style knurling tools.
And yes -- you *can* get them for less on eBay -- but if you need them right *now* for a paid project, you have to deal with the new price. :-)
Oh yes --- I also did not want to type too much, because I am recovering from the surgery which removed the titanium plate and screws from my arm -- which had been broken and repaired about a year ago. Remember that I was fairly quiet back then, too.
The knurls only press two opposite sides in, they don't shrink the tube - they may even expand and lengthen it. Last week I pounded a home-made swage rod into a steel tube to straighten and expand it slightly, then pulled it out easily after hammering the OD a little.
The picks I examined are solid and a touch over 1/4". I don't need to make new ones or anything like that, but am curious about the good quality work that went into them.
In production world, what sort of oil or coolant would be used? It's not really a cutting operation with conventional knurling wheels, but I suspect it's not an operation done dry either.
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The arm is getting better -- but a lot of PT still to go through.
The shop is usable by now -- with the Nichols mill, the Clausing
12x24" lathe, and the little Compact-5/CNC lathe working along with many other things.
The Bridgeport, where the fire started, is being rebuilt. I got a BiJur oil pump to replace the dead one, and lots of expensive little plumbing bits, and have it all connected except the lube to the head and its ball screw. (Still taking that apart as my arm allows. It is spread out on the floor.
But -- I was able to build a 10-meter J-pole antenna and get it installed before going back into surgery to recover the titanium parts. Interesting screws and plates. Looks like a Torx variant, though I haven't counted splines yet. (The overall length of the antenna is about
Well ... the ones which I have seen are double-ended, with a taper down to each pick insert, and I suspect silver solder to join parts, but yes, you *could* support it that way, cut off a knurled section, and then silver solder the cones in place. (Or perhaps, if it all has to be stainless steel, TIG weld it with a machine to hold the parts and rotate.
Some of the ones I have are small enough, and sold enough, so they could handle the crush, but the better ones are larger diameter and lighter wall thickness, so they are easier to control in the victim's mouth (mine). :-) So, it depends, I guess.
While it could be done with opposed knurls, I suspect that it was done with cut style knurls. They produce sharper diamonds and thus better non-slip grips.
Of course, we don't know what alloys are used for dental tools. I would suspect something like 316 SS (Also used for making photo processing tanks back in the days of the Nikkor tanks.)
I tend to use either Sul-Flo or Moly-Dee -- both good high-pressure lubricants for normal crush knurling. In particular, to keep the pins on which the knurls turn from being worn.
But for a cut style knurler, a cutting lube would be preferred.
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Yep! One titanium plate, and an even dozen titanium self-threading screws (specialized for threading in bone. :-)
It had to be cleaned and sterilized before I could receive the package.
As someone who has done plenty of production knurling I can tell you a little about knurling. When forming a knurl water based coolant usually works fine. For best results the coolant or oil used should be one that has high pressure additives. Especially if knurling tough materials like 316SS. Depending on the knurl type and the material it is possible to form knurls that are quite sharp. If cutting knurls are used then the oil or coolant chosen should be the same one chosen for regular machining. On a screw machine a neat oil or an oil with additives might be used more often than water soluble oil coolant. But in a lathe that runs many different types of work water soluble oil coolant would probably be used. Knurling is not as simple as it appears at first glance and the material being knurled has a lot to do with the type of knurl that will work best. Free machining brass is a material that would seem to be a good candidate for form knurling but it is actually better knurled with a cut type knurl. This is because it work hardens very fast and then starts to flake. On the other hand
304SS can usually be form knurled with excellent results. Eric
DoN, Why was the metal removed? Was it causing problems? I ask because I have LOTS of titanium and SS in both arms, my pelvis, and my back and none of these plates and screws have caused any problems. And all these metal bits have been in place for over a decade. Eric
I will once I tear open the baggie. I did take one shot of the baggie itself, with some of the parts visible in there, but I expect to open it up, spread them out in a nice array, and photograph plate and screws, followed by detail photos of the points and heads.
But I'm keeping it sealed until I use it to convince my dentist that I no longer need to take aitibiotics prior to a tooth cleaning. (Apparently, embedded metal is considered a focus of blood-borne infections stirred up by the tooth cleaning process. :-)
I'll be putting the photos of the screws in my web page about the arm experience rather than trying to e-mail photos to the world.
The heads look like Torx (to be verified by test-fitting to existing drivers once the baggie is open). They appear to be a shape and size so they will mostly bury in the holes in the plate while allowing setting at various angles as needed. (Again, to be experimented with once the bag is open.
Yep -- in a partially clear baggie, with a visible indicator strip which shows that it got hot enough for long enough to be safe to handle -- even if I had ebola. :-)
At least my arm is getting easier to live with much more quickly than last time. No significant bone healing to do -- other than to fill the holes where the screws were -- and after a week I can do a lot of things which it took a couple of months or more (plus P.T.) to reach from the previous surgery.
I hit a platform in the P.T. from the original surgery. In part because the therapist was restricted to avoid work in certain directions until the surgeon verified that the bone had regrown enough, and by the time he *could* attack the other motions, things had set up too much.
In addition -- the top end of the plate was up close to the shoulder socket, and I think that it was hitting there limiting range of motion in at least one direction. Also, I was getting sort of "plucking" feelings in the tendons as I went through certain exercises, suggesting that the head or the point of at least one of the screws was near a moving part in my muscle system.
Already, I cam move a good part of the way with less pain (though I will have to live on pain pills during the PT, which is supposed to be more aggressive this time).
I was just barely able to reach up to the top of the drill press spider, and unbolting and lowering parts of the Bridgeport CNC mill head was a real trick. :-)
I don't expect full range, but the ability to get the right arm up to assist with changing the battery in a ceiling mounted smoke detector (I need to change the batteries again, of course) would be a nice benefit. Last spring was a real pain (literal) changing the batteries. :-)
I really should have done this break earlier, instead of waiting until I was 73 years old or so. Old farts heal *slowly*. :-)
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