Need Help Cutting 3/16" Wide Slot

sanddan

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I am making an adapter to engage the knee crank so I can use a drill motor to move the knee. I am setup to make the first series of cuts that form the cogs, 3/16" cutter .150" deep at 1100 RPM. The cutter is HSS and for this job. I am getting a lot of squealing even with very minimal pressure. I tried both a 4 flute and 2 flute end mill, same amount of noise but the 2 flute did seem to do better. I am using cutting oil, dabbed not flood. Does this seem to be about right for speeds and such? I haven't used small cutters like this before though I did make an aluminum proto and didn't experience any squealing. Any suggestions from the more experienced would be appreciated.
 
Sometimes I work too many steps into building something. and may have considered pre-drilling the layout and cleaning it up with the end mill. I would have thought the aluminum prototype would have worked well. Hard to find the right speed for me sometime but I bet I would start around 12-17 hundred and tweaked around until it felt right. Let us know what you end up with and may the force be with you.
 
sanddan,

Much depends on your stock material, which you did not mention.

For cutting mild steel with HSS I usually aim for 80 sfpm. For a 3/6" cutter that gives 1630 rpm.
What cutting oil are you using?
Let us know how it goes.

-brino
 
brino,

It's cold rolled. Sounds like I should kick er up a notch and see how it feels. I was hoping for a direction up or down, that helps a lot. I'm using some cutting oil I got from a local hardware store. Not sure of the brand. I used WD for the aluminum which worked good.

Dan
 
3/16" and smaller cutters require some experience to use efficiently. Too much load and they flex and wobble, too little feed and they can dull.

I would ramp up the speed and take .050" deep passes and see how it goes.
 
Agree with Andre. Cutting speed for an end mill taking a slotting cut at 1/4 the cutter diameter is about 105 SFPM. This works out to just over 2000 rpm with a 0.050" DOC when using a 3/16" end mill. Because you do not have the chip clearance potential when cutting a slot, use the 2-flute cutter instead of the 4-flute. If feeding manually, feed to maintain a slight positive feel and you'll do fine.
 
I recently completed a similar job for my Cinci Toolmaster (which came to me without a knee crank). There are lots of replacement handles on ebay, but the only one to fit was the drill adapter version. I had a couple old crank handles from a wrecked machine, so I modified one for the Cinci. I faced off the original drive pins and set up an interferance fit for a small stub. I made the stub, with face spline first - then pressed the two together (with a bit of Loctite). I ought to have taken some pictures of cutting the spline. Anyway, I too used a 3/16 end mill. I was probably only running at 950 or 1200 rpm. It seemed to cut nicely at 0.04" DoC. The material was 1018 cold rolled.

DSCF5598.JPG DSCF5599.JPG
 
Thanks for all of the help, the pins are all cut and the fit is perfect. I ended up running the first cut (3/16" 2 flute HSS end mill) at 1950 RPM and .150" DOC. It liked to be pushed a little bit, only squealed if I slowed the feed too much. I tried 1800 and 2000 RPM but 1950 was the sweet spot. The next two passes are with the 1/8" 4 flute HSS end mill at 2100 RPM which cuts the taper in the pins. Each side of the pin gets a cleanup cut, also at .150" DOC.
P1030378.JPG
 
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