how to cut a 0.002 slit

scphantm · Jan 7, 2015

Im playing with pen nibs. Quick question, how would you cut a 0.002 slit in about 10-20 thou material (brass, steel most likely) without an EDM?

I found a video of a commercial company doing it and it seemed like they had slitting saws and a fixture in a very custom looking machine. I gotta think that for a saw that thin it would need some kind of support or it would flutter.

You guys have some ideas on how you would pull it off?

EDM JOE · Jan 7, 2015

How about a laser?

jmcvo · Jan 7, 2015

Laser sounds like a good choice. Or, could the working end of the nib be sheared part way, with the sheared edge ending at a hole? And then, each side of the nib aligned in an operation that would also form the curve?

jkopel · Jan 7, 2015

Carbide slitting saws are available down to .002
Not cheap though.

Spyderedge · Jan 7, 2015

Awhile ago somebody posted about running a .0015" wide saw, so it is possible. You need high speeds though to keep the cutter from warping under it's own weight. (He was running 10-11k RPM)

rustytool · Jan 7, 2015

At 1:30 in the first video and 7:50 in the second a slitting saw with side support is shown cutting the slit.How is the slit cut in the nib of a fountain pen? - Quora

Hazzert · Jan 7, 2015

We've ran robbjack carbide saws down to .006" thick. Like jkopel said they weren't cheap at around $80 a pop direct.

Ken hosford · Jan 8, 2015

I would think you could shear them then compress material at root to open

Lakeside53 · Jan 8, 2015

It's interesting to me that we are now wondering how they made the billions of pen nibs only a few decades back

Heck, we weren't allowed to use "ballpoint pens" at school - had to use a fountain pen and ink. 1970's...

I suspect they were sheared and biased to open slightly.

sandiapaul · Jan 8, 2015

This is not my idea...I read about it in a book by Guy Lautard. A guy needed to cut a .001 slit, he took a .001 feeler gauge, clamped it in a vise and broke it off so the broke edge was rough, clamped it in a jewelers saw then used diamond paste and sawed the slot. Always seemed like a neat rick, but I never needed to try it.

dgfoster · Jan 8, 2015

Possible method based on imagination but not previously tried.

I would think it might be interesting to take a disc of soft steel,say, 3" diameter and .3125 thick. Then put a 3" spigot in the chuck of your lathe and turn the face of the spigot true. Then adhere the disc to the spigot with cyano glue. Now face the 3" blank with a true shoulder from its periphery to a radius of .5 and futher relieve it deeper from .5 to zero diameter. Drill a 3/8 hole in the center. Now cut down the periphery of the disc to a depth of 25 thou but leave about ten thou uncut and forming a ridge on the periphery of the disc .010 wide and .025 high and beginning at the faced surface of the disc. Remove from the lathe and then beginning with the freshly faced side of the disc down, surface grind each side of the disc by a thou or two alternating the ridged side and the unridged side until a .002 wide ridge is left on the periphery and standing .025 high. Now place the disc on an arbor with a freshly turned face that runs true and with a center raised portion to fit in the centrally relieved portion of the disc. Fix the disc in place with a 3/8 screw drilled and tapped into the spigot. Charge the disc with diamond past that is fairly coarse (10 micron?) and run the disc at 300 rpm but turning away from the operator.. Lay the nib on the disc and watch the disc/lap neatly slice a polished slit in the nib. A jig could be fashioned to accurately align the nib so the slit ran true to the center line off the nib. I do think there is a good chance this would work.

Denis

juergenwt · Jan 8, 2015

Wire EDM. .002 wire is available.

dgfoster · Jan 8, 2015

juergenwt said:
Wire EDM. .002 wire is available.

That would be the easy way. I think he said no EDM in the OP.
Denis

KMoffett · Jan 9, 2015

Photo etching.

Ken

anoldcrank · Jan 9, 2015

Lakeside53 said:
It's interesting to me that we are now wondering how they made the billions of pen nibs only a few decades back Heck, we weren't allowed to use "ballpoint pens" at school - had to use a fountain pen and ink. 1970's...

I suspect they were sheared and biased to open slightly.

I think it was done with an abrasive wheel.

Think Dremel.

rwbaldwin · Jan 9, 2015

Isn't the hole at the top of the slit the key element? It allows you to shear the slit without deforming the nib too much and allows you to open up the slit.

dgfoster · Jan 9, 2015

rwbaldwin said:
Isn't the hole at the top of the slit the key element? It allows you to shear the slit without deforming the nib too much and allows you to open up the slit.

If youu look at the video, at about 3 mins into it the hole is said to be for stress relief. Again, the video shows the slot being abrasively cut, not sheared---a siamond wheel was used. The video was very interesting and a useful source of accurate information.

Denis

D.D.Machine · Jan 9, 2015

There was some REALY simple plans out years ago on building a cheap EDM power supply. one of the shops I worked at had one for burning out taps, I remember swapping out light bulbs to get the power we needed then we just used it on a drill press with coolant as the cutting fluid.

Scottl · Jan 9, 2015

rwbaldwin said:
Isn't the hole at the top of the slit the key element? It allows you to shear the slit without deforming the nib too much and allows you to open up the slit.

I remember some really low cost pens. I doubt they were cut with an expensive slitting saw. Some of the cheapest pens were nothing more than an artist's brush handle with the nib built into the ferrule. They had to be dipped in ink. In those days a lot of the cheapest stuff was "Made in Japan".

blcksmth · Jan 9, 2015

I heard somewhere that someone used dental floss with diamond dust to cut a narrow slot in steel. Don't now what diameter floss is but maybe some other flexible material with abrasive.

Bob
WB8NQW

how to cut a 0.002 slit

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