Milling Krell Metal?

Doug White fired this volley in news:Xns9FC7D58A54875gwhitealummitedu@69.16.186.7:

At an inch a minute, you're taking only 1/4-thou per tooth. You probably want to take two or three thou, at least.

I had the same problem with a cutoff tool that wouldn't fit my B toolpost. I had to mill it, and it was tougher than my wife's worst snarl.

I cut about 5-thou deep at 20 ipm, and it cut very cleanly with oil-free coolant using a carbide insert facing mill with zero rake inserts. (a few yellow and white sparks, though, even with flood!!)

Lloyd

I have the cheaper import copy of the scissors knurling tool and an 8525.

The shank sparks like a medium carbon steel with possibly some alloy content. A file barely cuts it.

Generally when my mill balks at a disreputable hunk of steel I toss it in the wood stove overnight to anneal. Finished pieces can be wrapped in a flattened tin can containing charcoal, sawdust, paper etc to partly protect them from scaling. If you have to pay for your heat source, like a propane torch, it seems adequate to heat the steel to a moderately bright red glow, let it cool to black and quench in water. That may leave some gummy steels just hard enough that they don't tear, opinions vary.

A tin can on its side, floored with charcoal, holds the heat in better than an open torch flame. Beware of carbon monoxide.

Scrap flame-cut steel thusly treated mills very sweetly on my little Clausing with 1/2" HSS end mills at 600 RPM.

jsw

Well, get indexable end mills. You can index the inserts a couple times when dull, then replace the inserts. WAY cheaper than chewing up entire end mills on tough jobs like this.

Jon

The Clausing mill is limited to 1/2" MT2 or B&S7 collets which restricts the choice of indexable tooling. Mine holds a single insert.

jsw

Considering that the top of the shank if of no importance, just cut it with angle grinder cutoff disc so it fits..

Kristian Ukkonen wrote in news:P_iKq.2040$ snipped-for-privacy@uutiset.elisa.fi:

I thought about attacking it with my bench grinder, as I don't have an angle grinder. It actually works out better to remove the bottom of the shank, because that lowers the tool closer to the centerline of the lathe. As it is, it will probably be tipped slightly in use, but for a scissors style tool, it doesn't really matter much.

I suppose I could grind it down a ways, and clean it up in the mill. The grinding would presumbly take out some of the temper as well.

Doug White

Or you could make another shank the right size and center height, and leave your expensive tool intact for when your heirs sell it.

jsw

...for a penny because they don't know what it is.

-- [Television is] the triumph of machine over people. -- Fred Allen

"Lloyd E. Sponenburgh" wrote in news:Xns9FC7D99474ABlloydspmindspringcom@216.168.3.70:

OK, it sounds like I should try a shallower cut, but with a much faster feed. I'm off to MSC to pick up a couple cheap carbide end mills.

I'll also grind off what I can, partly to remove as much metal to start with, partly to see what the sparks look like (crude alloy test), and partly to try to soften the area before I hit it with a cutter.

Thanks!

Doug White

Why not grind it down.

Why didn't you buy the Aloris or other AXA tool post. That sounds like a B or larger one.

Mart> I recently bought an Eagle Rock scissors type knurling tool like this: >

Take the chunk of Mystery Metal to your local scrapyard. They have these fancy Laser Spectrography Metal Analysis guns that they put up against the sample and pull the trigger, and in a few seconds {Bada-Bing!} it tells you exactly what you are dealing with.

And if it says "Titanium Alloy" or something exotic and expensive... You machine a new one out of steel, and sell them your mystery gear for surprising amounts of coin. And bring in the shavings you've already made, too.

-->--

Martin Eastburn wrote in news:mAwKq.224872$ snipped-for-privacy@en-nntp-15.dc.easynews.com:

I have an Aloris AXA tool post. The Eagle Rock knurler used to come with a cast shank that would fit the standard AXA holders (a friend has one), but they changed the design of the shank. I used to have an Aloris AXA knurler, but it was a pain in the neck to use compared to the scissor design. In order to get the knurls even, you have to get the center height just right, and it doesn't have nearly the size range of the scissor design.

I ground down the bottom of the shank most of the way, and will clean it up when my new carbide end mill arrives (hopefully later today).

Doug White

Doug White wrote in news:Xns9FC98A2C118C7gwhitealummitedu@69.16.186.7:

My MSC order arrived, and within minutes I was cutting metal on the mill. I'm not sue what did the trick, but the stuff cut just fine. When I was done, the end mill was still scary sharp.

Things that were different:

No sign of strain on the machine, nice finish, and the job is done. I blued the shank, reassembled the knurler, and mounted it in a tool holder.

I did my first knurl with it. I installed straight knurls, and I think I need some practice with them. They did the job, but I think the two knurls got out of sync, and I ended up with a finer knurl than I expected. I didn't bother checking the diameter, but I suspect that is much more crucial on a straight knurl than a diamond. The forces were also enough to move the cross feed around, so I need to lock that down. This was in 303 SS, and I suspect that it work hardens fast enough to make knurling it a pain.

Thanks for all the suggestions. On to the next project...

Doug White

I counted 48 teeth on a 3/4" diameter knurl, which if it were a gear would mesh with a 1" gear with 64 teeth. To me this suggests that the workpiece has to be an integral number of 64ths in diameter. Many even and a few odd millimeter sizes like 19 and 25 are very close to x/64"

jsw

"Jim Wilkins" wrote in news:jdg6ut$ru5$ snipped-for-privacy@dont-email.me:

Hmm. In this case the rod was 5/16" OD, so it should have been OK. I'll have to count the teeth. I bought the knurls quite while ago, and I thought I ordered "medium", but the Eagle Rock web site doesn't list them that way. They have quite a range of pitches.

Doug White

What you really want is an AXA-19. (I've got the BXA-19 on my lathe.) It is a scissors style knurling tool made for the quick-change toolposts. It has two parallel arms traveling on a vertical dovetail, with a knob on the top and a leadscrew which is right-hand thread on one end and left-hand thread on the other end to move the arms together or apart. This design maintains the center point between the arms, so all you need to do is take the time *once* to adjust the height adjust nut on the main body, and it will be centered every time you use it (presuming only a single lathe, of course). Since it is a scissors style in function, it relieves the cross-feed leadscrew of the excess load which a bump style knurler imposes.

O.K. I do have an Eagle Rock which came with a 1/2" shank and even works on my little Compact-5/CNC lathe (5" swing.)

But I have modified quite a few 3/4" shank tools to fit my BXA

Enjoy, DoN.

I haven't done any straight knurling of stainless in a number of years, and I would expect that trying to use 2 straight knurls at the same time would be problematic.

I was able to straight knurl 316 SS with a single knurl (just crossfeed pressure) fairly consistently at low RPM on workpieces of about 1/2" dia. without traveling along the workpiece. Straight knurls should be capable of travel, but probably only easy if the knurl ID holes and the pins are very smooth, and well lubricated (not just flooded with watery coolant-type cutting lube).

Diamond pattern knurls need the same characteristics and lubrication to be able to track properly.

Attempting to see how well 2 straight knurls can sync is probably easier done with some aluminum or leaded steel material.. if they won't sync easily in these materials, the best choice may be diamond knurls, otherwise the anticipated results may be a matter of luck rather than skill or method.

There are the common metal-displacing type knurls and less common cutting knurls

Displacement-type diamond pattern knurls should be able to work properly without concern for matching the pattern size to the diameter of the workpiece.. that's where the good bearing surfaces of the pins and proper lubrication come into play, as the knurls can creep a little to keep falling into/track the same pattern. The helical shape of diamond pattern knurls helps them track because they can slip sideways a little while they're working.. if they don't have a gap between the knurl and the holder (and good lubrication), thay can't slip which will most likely produce poor results and lots of frustration.

The method taught when I was in high school was to carefully bring the knurls into light contact with the workpiece and rock the chuck back n'forth by hand, adjusting one of the knurls until the pattern was properly spaced to produce full diamonds (not smaller parallelograms).. then bump the cross feed in a bit and rotate the workpiece over a wider arc while establishing a bite into the workpiece with the correct pattern. After applying adequate cutting lube, it was a matter of feeding into the workpiece as soon as the spindle motor was switched on. The knurls would displace the material and establish a pattern to track, so the operator could travel the workpiece and continue to feed until the desired results were attained. We didn't have scssor-style knurling tools back then.. but the same principles apply. We were students.. I'm sure experienced machinists develop/utilize different methods.

Straight knurls should also track an established pattern, although this could be a little more difficult when working with work-hardening alloys.. it may require the operator to make CNC-like movements to be able to attain consistent results for a large number of workpieces.