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Thruthefence
01-06-2009, 05:11 PM
Is there a technique for cutting serrations? I am interested cutting serrations on a sort of washer, ( tho rectangular ) and a matching set on a part that would slide under the washer, (when the tensions on the washer is released ) The material is aluminum, and this is part of a locking device.

thanks in advance

ERBenoit
01-06-2009, 06:18 PM
I can read, but not really see what you are trying to do. Do you mean serrated, as in a serrated step block, or something like a ratchet wheel? A dovetail cutter might work. Though the "washer", if it is relatively thin, holding such to machine may pose somewhat of a problem.

SGW
01-06-2009, 09:02 PM
Are these cuts radial, or parallel? (For the record, I don't know of any particular way to do either one, but the radial would be a lot more difficult, I think.)

BobWarfield
01-06-2009, 09:23 PM
People do what gunsmiths call "checkering" with a milling machine. I've seen posts on the web, though I don't have any links.

Pretty easy to take an engraving cut and mill a set of parallel grooves. Turn the piece and mill another set and you've got a crosshatch.

It seems like matching grooves on the two pieces would do the locking you describe. Not sure what scale you want the locking to occur on. In other words, we could be talking about a lot of small grooves or a few big strong grooves. Different cutters would be needed in each case.

Thruthefence
01-06-2009, 10:26 PM
Let's see, visualize a piece of aluminum stock .75" wide, 1 " in length. the thickness, say .125". What we want, is a series of serrations, cut across the width of the stock, leaving say .125 at each end unserrated. now we will drill a .25" hole, centered on the extruded area.

Now take another piece of 6061, .75" wide, ,.25" T, length to be determined, but for our purposes, lets say 10.0". Now, cut an identical set of serrations across the width of the stock, beginning say .5" from one end, for a distance of 2.0" along the length of the stock. The pitch of these serrations must match those previously cut on the 1" stock above, so when the two pieces are laid face-to-face ( or serration-to-serration, if you like ) there will be no relative sliding motion between them, that is in the lengthwise direction. a slot will be milled .25" wide through the long piece's serrated area.

I was thinking of putting a threading tool in the mill, and sort of cutting across the stock using the crossslide. Maybe using thread pitch info for moving the along the y axis? I will try to find a pic of a similiar setup.

Brian H.
01-06-2009, 10:43 PM
So this would be something like two gear racks placed so that the teeth mesh (sort of)?

Hmm... maybe you could use a carbide die grinder bur, if you could find one the right shape. Or, if your mill head rotates, you could rotate it 45 degrees and use an end mill to cut grooves with a 90-degree included angle, using your y-axis.

Does this give you any ideas?

-Brian

Thruthefence
01-06-2009, 10:56 PM
yeah, sort of like two gear racks placed gear to gear, but much finer pitch.

wierdscience
01-07-2009, 12:10 AM
Quick and dirty,pick a thread pitch that looks right for the job.Take a tap(larger diameter the better) lets use 3/4-16 tpi as an example.

Grind the threads off all flutes except one,use it as a fly cutter in the mill.I would also cut the length of the tap down eliminating the start on the flutes making it shorter and more ridgid.

I've used this method several times and it works well,it's just a little slow,although on AL you can spin the spindle up full tilt and make the cut.

If a 60*seration won't work,then another option would be to form grind your own cutter,time consuming,but doable.

chief
01-07-2009, 03:29 AM
Use a threading tool mount in the mill and cut it like you are doing a graduated scale.