Ghetto Knurling

[JavaDog]

Sawman had some questions about knurling in another thread, and it reminded me of something I had been toying with.

See, I have some projects in mind that I want to make some custom knurled knobs for - but I don't have a lathe. So I was trying to come up with a way to do basic "industrial" (ie - Not fancy) knurls with my CNC Machine (once it is done!). So, I came up with this idea - which could be done on any CNC mill with a rotary.

Check it out:


Step: 1
Chuck Knob in Rotary and Chuck V-Bit in Router.

Step: 2
Plunge V-Bit while rotating knob to make 'troughs'.

Step: 3
Step/Increment knob set number of degrees, stop, then plunge and move V-Bit horizontally.

In my head this could make some nice knurls, of varying depths and styles (using different bits). Now, I am sure I am not the first to think of this - but if I am - feel free to tell me how crazy/dumb of an idea it is.

[dannystooblue]

i understand what you want your end result to be, and it may work well but if you can in some way get away from using the tip of the cutter you will get better looking cuts and better tool life. what you are cutting is alot like a straight knurl with grooves cut in it, it may look nice even without the grooves just the straight cuts then you would have alot less to deburr.

[Mcgyver]

Java, why bother with a rotating tool? you can grind a bit to the V profile and set the machine up to act like a shaper. cnc controls the indexing and depth of cut - forget step two, proceed to three and you've go beautifully cut straight knurls, high class stuff!

[JavaDog]

Originally Posted by Mcgyver Java, why bother with a rotating tool? you can grind a bit to the V profile and set the machine up to act like a shaper. cnc controls the indexing and depth of cut - forget step two, proceed to three and you've go beautifully cut straight knurls, high class stuff!

You lost me.

[Mcgyver]

you can do this manuallyl, but cnc would take a lot of drudgery out of it - i'll describe the manual process and you figure out the cnc

A rotating cutter is going to be pointed, right? as you approach the centre of the cutter, its speed approachs zero, while the periphery is going around so fast its making dust not chips - its a really inefficient cutting action. My idea, is don't cut with a rotating cutter, cut with a simple little hss cutter ground to a V and locked in the spindle and not rotating.

mount the work in line with an axis in what ever you were going to use to index it, or if you've got it the 4th axis. rock it back and forth feeding z axis down to the desired dept of V and index to next V - this is like shaping, ie what this http://metalworking.com/DropBox/_200...r-Finished.jpg tool does.

repeat until a very nice straight knurl is formed. for some jobs, knobs etc, a straight knurl just looks right - better than a diamond

see photos

http://www.hm-thread.com/hmknurl.html

[JavaDog]

Ah, Ok...I get ya now. That is interesting, and that big machine is pretty crazy looking.

I like diamond knurling more than straight knruling though, especially for knobs. I guess some of it is just personal preference.

Looks like there are many ways to knurl a cat!

[Mcgyver]

that big machine, a shaper, is a very small one. It's a nicely restored atlas bench top model - its more common to see floor models. A shaper is virtually obsolete in industry because the momentum of the ram requires a slow speeds compared to a mill and it only cuts on forward stroke (50% of the time). The machine however prized by home shop guys because cutters are single point, cheap and easy to sharpen. For some some rare jobs, like a blind internal keyway they are just the thing - I wouldn't turn one down.

I agree on the diamond knurl for the most part, on some things though the straight just looks right. then again they are both for peasants compared to Rivetts collection http://www.cnczone.com/ub...=007412#000000

[DieGuy]

Yeah shapers are cool, I used to use one in a tool and die shop to "chase the line" when making dies. Many times the line you built the die from comes from a developed pattern in sheet metal created from forming samples in the form section of the die. They are never a straight line, so you take the final pattern and scribe the upper and lower trim sections and then "chase the line" You finish and harden the lower half and get it mounted and doweled in the die set and with the upper being still soft you can "fit" the upper to the lower. By sneaking up on the line you can then dial off the amount of clearance you want on the shaper. The clearance on a sheet metal die is important in that it controls the "break" on the punched part. By mounting the upper in a soft state you can take it to the press and make a "light" hit on the lower to get an impression line of the lower half. There is a bit more to it than that but you get the idea. It is nice cause the uppers usually have an integral foot for mounting, making the cut blind and the shaper stroke is adjustable to that blind cut. Shapers also leave a nicer finish than a mill in the drop through section of the die making it wear much longer.