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View Full Version : Interesting way to knurl...



skunkworks
09-29-2015, 07:47 AM
This video impressed me. It is using linuxcnc G33 thread cutting gcode.


http://www.youtube.com/watch?t=5&v=zdCQ0X7b2uo

The gcode.


G8
G53 G0 X0
G53 G0 Z0
M6 T3 G43

#<workpieceDia> = 0.700
#<workpieceRad> = [#<workpieceDia>/2]
#<safeXOffset> = 0.025
#<safeX> = [#<workpieceRad> + #<safeXOffset>]

#<knurlStartZ> = 0.000
#<knurlLen> = 0.25
#<knurlLeadIn> = 0.010
#<knurlDepth> = 0.002
#<knurlPerDia> = 28
#<knurlAngle> = 30
#<knurlEndZ> = [#<knurlStartZ> - #<knurlLen>]

#<rpm> = 100

#<pi> = 3.142

; The surface is the circumference of the workpiece
#<workSurface> = [#<pi> * #<workpieceDia>]

; Given a knurl angle, calculate Z feed given <workSurface>
#<feedPerRev> = [TAN[#<knurlAngle>] * #<workSurface>]
#<feedPerMin> = [#<feedPerRev> * #<rpm>]
(debug, feed per revolution: #<feedPerRev>; per min: #<feedPerMin>)

; thread _width_ is equal to distance traveled in one rev, i.e. <feedPerRev>
#<threadWidth> = #<feedPerRev>
; Thus, TPI will be 1/<threadWidth>
#<tpi> = [1/#<threadWidth>]

; To do a n-start thread, we need to start each thread
; <threadWidth>/n further back (Z+) than the prior thread
#<nStartZOffset> = [#<threadWidth>/#<knurlPerDia>]


M3 S#<rpm>

#100 = #<knurlPerDia>
#110 = [[#<knurlPerDia> * #<nStartZOffset>] + #<knurlStartZ> + #<knurlLeadIn>]
(debug, knurl lead in: #110)

G0 Z#110
G0 X[#<workpieceRad> - #<knurlDepth>]

O100 WHILE [#100 GT 0]
(debug, start Z: #110; feed: #<feedPerRev>)
(calculate the lead in for the knurl AFTER this one)
#105 = #110
#110 = [#110 - #<nStartZOffset>]

;G33 Z#110 K#<feedPerRev>
;G1 Z#<knurlEndZ> F#<feedPerMin>
;G1 Z#105 F#<feedPerMin>
G33 Z#<knurlEndZ> K#<feedPerRev>
G33 Z#105 K#<feedPerRev>
;G0 X#<safeX>
G0 Z#110
;G0 X[#<workpieceRad> - #<knurlDepth>]

#100 = [#100 - 1]
O100 ENDWHILE

Richard P Wilson
09-29-2015, 07:49 AM
Is this quicker than 'put knurling tool in machine, switch on, advance tool into work, withdraw tool, switch off?

JoeLee
09-29-2015, 08:11 AM
That is a pretty cool way to knurl. It doesn't put any stress on anything.............unfortunately it's beyond the capabilities of my Clausing 5900 and most other guys machines too.

JL...............

JRouche
09-29-2015, 12:31 PM
That was pretty cool. I happen to have an Emco 120 (not the 120p as in the video) so I may give her a try. Thanks for the code... JR

rklopp
09-29-2015, 12:36 PM
It looks like there's a lot of rubbing going on, because the insert doesn't have enough clearance to handle the big lead angle on the "threads." I'd like to see what happens on 4140 pre-hard instead of aluminum. Regardless, it's a very slow way to go compared to usual upset or cut knurling. I sometimes cut straight knurls with a thread mill and an indexer when I want them to come out like jewelry, but that is also a very slow method.

wierdscience
09-29-2015, 12:41 PM
Lay the insert tool over to match the helix angle and it would be fine.

Sun God
09-29-2015, 12:42 PM
Yes, it's slow, but it also has no more feed pressure than a cut of equivalent depth, and requires no setup from the operator - on a small lathe, I'd bet a 2-minute 'knurl' cycle is faster than turning the part under NC, then either mounting/setting up a scissor knurler, or moving the part to a second op machine for scissor knurling. All bets are off with a cut knurl.

I have actually done rudimentary knurls using this method before, by indexing the stock in the chuck a fixed amount then doing a left hand, and right hand, threading pass with a relatively coarse pitch. It was *very* slow but it was only ever intended to be an experiment. Shallow DOC; the tool had highly exaggerated side clearance - 30 odd degrees per side, maybe more. I only had the patience to do 4 passes, though.

DR
09-29-2015, 12:53 PM
Is this quicker than 'put knurling tool in machine, switch on, advance tool into work, withdraw tool, switch off?

Yeah, it takes way more time.

I can see a use for it though. Aluminum is difficult to knurl the conventional way. Little flecks of aluminum get pounded into the work piece. If you color anodize a dark color like black, white spot are left on your work where the flecks dislodge in the process. This is why you seldom see diamond knurls on aluminum parts like instrument knobs, etc.

Mike Amick
09-29-2015, 02:17 PM
Nobody seems to be talking results. If its a deeper more crisp knurl, then it doesn't matter how long it takes.
Reserve it for those special projects.

DICKEYBIRD
09-29-2015, 02:49 PM
Pffft...Linux geek showoff.:rolleyes:






VERY impressive!:cool:

The Artful Bodger
09-29-2015, 03:28 PM
This is the Home Shop Machinist site so we need an appropriate mechanical method, something like this driving the lead screw back and forth...

http://www.douglas-self.com/MUSEUM/POWER/gear/Reversing%20gear2.gif

Forestgnome
09-29-2015, 03:53 PM
Seems to me you could do the same thing on a manual machine by bolting an indexer to a faceplate to index the start of each thread. This assumes you have the tpi capability of course.

Doozer
09-29-2015, 07:35 PM
Lay the insert tool over to match the helix angle and it would be fine.


That would only work if the tool cuts in one direction in the Z axis,
but it goes forward and back. It is cool, but I am not sure how not
to make it rub. Agreed, if it were anything other than aluminum,
it might break the insert. A + for effort though.

-D

PS- I mean, yes you could grind the tool for clearance, but it would
have little edge support. Would have to be a symmetrical clearance grind.
I am thinking oil groover tool.
Hey I bet a cnc lathe could cut oil grooves in bushings pretty easily.
A properly grooved for oil bronze bush works very well, given oil.
Hmmm.

Toolguy
09-29-2015, 07:40 PM
It could be done with a rotary tool like an engraver bit or 90 degree point endmill.

Mcgyver
09-29-2015, 07:58 PM
a crude affair. Show me a cnc lathe with live tooling that cuts a knurl with micro features such that from one direction you see an image of James Watt and the other Tesla and I'll be impressed :p

Paul Alciatore
09-29-2015, 08:29 PM
No, that would not work because the tool reverses direction. It needs a large clearance on BOTH sides unless the tool rotates during the cut. That would be a tool axis: "T" axis, if you will. Do any CNC packages do that?

Why is it beyond the capabilities of most lathes? I mean, aside from the obvious fact that most lathes do not have CNC. I would like to know so that when I finally do get or create a CNC lathe I will know more about the limitations while making my choices. Is it the cutting on the back side thing? I would think this would work just as well with the tool up front.




Lay the insert tool over to match the helix angle and it would be fine.

iMisspell
09-29-2015, 10:06 PM
If one wanted to, you could do it with two tools, left and right handed in funky holders using the two different hands to thread right to left and then a second tool left to right.



No, that would not work because the tool reverses direction. It needs a large clearance on BOTH sides unless the tool rotates during the cut. That would be a tool axis: "T" axis, if you will. Do any CNC packages do that? Not sure if this is (https://www.youtube.com/watch?v=sdrZkUUYrBc) what you ment, but some machines can hold square shank tools in the same fashion (but the tool does not contently rotate, its locked into postion). Over the recent years there was a thread on here of a machine, thick it was an Okuma turning a cam shaft of some kind, did alot of work with a single square shank profiling tool (thick it was a right handed tool and held a DNMP shape insert) and instead of doing a tool change for a left and right handed tool, the tool would flip/turn 180deg in the turret "arm".

_

mickeyf
09-29-2015, 10:13 PM
Strictly speaking it's not knurling, since the material is cut rather than displaced. But it's pretty neat.

Doozer
09-29-2015, 10:25 PM
Knurls are a feature on a part.
Any process used to produce a knurl is knurling.
-D

wierdscience
09-29-2015, 11:23 PM
a crude affair. Show me a cnc lathe with live tooling that cuts a knurl with micro features such that from one direction you see an image of James Watt and the Tesla and I'll be impressed :p

If only someone would write an article on a homebrew cut knurling tool......oh wait:D

Paul Alciatore
09-29-2015, 11:58 PM
I wonder if a roller tool with a 90 degree angled edge and that was mounted on an off center shaft (like self steering casters) would work. It could follow it's own course and there would be no clearance problems. You would probably need to trace the same path several times to get full depth.

Doc Nickel
09-30-2015, 12:31 AM
Why is this even a question? Take the insert over to a diamond wheel, and grind a little extra clearance on the other side. Bang, you're done. The knurling isn't going to be terribly deep or put a huge load on the insert, so it should work fine. For that matter, the guy in the video didn't seem to have any real problem at all, so obviously it's not a huge issue.

Doc.

wierdscience
09-30-2015, 01:06 AM
No, that would not work because the tool reverses direction.

He did half,then the other half,put the tool on a pivot.Don't know if a CNC lathe would do that,but it could be done with two separate tools.

Forrest Addy
09-30-2015, 10:20 AM
I could free-hand that on a manual lathe - if I wanted to. The trick is to bunch up or spread out the individual passes so you reach full circle with the knurls looking even. Did I ever tell you guys about my logarithmic knurl? I do another that looks like Arabic calligraphy.

Paul Alciatore
09-30-2015, 08:58 PM
???? The video clearly shows the tool starting from the tail stock end, traveling toward the head stock, then slowing down and REVERSING direction in the SAME cut. I was going by that.

Yes, the tool could be set at different angles for individual cuts in different directions. But that is not what was posted.




He did half,then the other half,put the tool on a pivot.Don't know if a CNC lathe would do that,but it could be done with two separate tools.

Paul Alciatore
09-30-2015, 08:59 PM
Sounds cool! Do you have any photos?




I could free-hand that on a manual lathe - if I wanted to. The trick is to bunch up or spread out the individual passes so you reach full circle with the knurls looking even. Did I ever tell you guys about my logarithmic knurl? I do another that looks like Arabic calligraphy.

wierdscience
09-30-2015, 09:34 PM
???? The video clearly shows the tool starting from the tail stock end, traveling toward the head stock, then slowing down and REVERSING direction in the SAME cut. I was going by that.

Yes, the tool could be set at different angles for individual cuts in different directions. But that is not what was posted.

I'm saying hypothetically the tooling could be automated to change angles at the end of each pass.But why not just buy or build a cut knurling tool and be done with it.

skunkworks
10-01-2015, 11:26 AM
I think it was mostly 'wonder if this will work..' ;)

Late at night - working on a project.. Need a knurl - no knurling tool...

sam

skunkworks
10-02-2015, 09:21 AM
More spindle synced motion/threading videos
http://www.cnczone.com/forums/linuxcnc-formerly-emc2-/283236-cnc.html