[turbotoys]

I searched all over and cannot find my answer. I am a total newbie - just got my machine running this weekend. Its a RF-45 by the way

I used the G-Wizard and set my feeds and speed accordingly and am wrecking bits faster then I can put em in there... lol

Here is how I had my last run setup.

3/16" flat end mill HSS-Co8 - 4 flutes- feed rate 6.737 - spindle speed 3,119rpm - plunge rate 1.6 - depth of cut .0188 - cutting cold rolled steel - Good Ole WD40as a lubricant.

The issue I am having is the tip turned black and wont cut no more. The run before that on a different bit turned bright orange and melted the bit.

What the heck am I doing wrong???

[turbotoys]

Oh - I am cutting a slot by the way.

[kjk2002]

I suggest annealing the CRS and trying again.

[turbotoys]

If it is just too hard can I just lower my feed rate? or do i need a better grade cutter? I don't want to lose the hardness of the steel because I am trying to make a wrench with it.

[freejep]

hi there,
burning cutters out is a heat problem....either too high on revs for the material or not enough lube...

Generally a 4 flute cutter is not very clever at producing deeper slots(deep in relation to cutter dia) because of restricted flute clearance for swarf evacuation.....you are also in trouble with lack of constant lube....if the cobalt cutter is all you have then try reducing the depth to 1/2 dia...and doing it in 2 passes....

If it was my job and without lube....I'd use a 3 flute solid carbide cutter at 3000 rpm in 2 equal depths of cut at 6" feed(simply because of lack of lube)

If you aint got carbide cutters to hand then you could use a method I used on my mini router......sounds silly but use plasticine or blutac around your slot area if its not very long to create a wall and fill it with any oil you have to hand to create a pool...engine or cooking oil will do....messy but will get you out of bother for a few slots....but drop the revs to 2000 and still do in 2 depths at slower 4" feed for your 4 flute cobalt cutter....

Books and programs are a guide only....cut it....see what happens...alter it to suit

good luck....and if its a production run then invest in carbide with your lack of constant lube...similar price to hss or hsco these days anyhow

Jep

[awerby]

I don't see your wrench being worth the cost of the tooling you'll burn up trying to make it that way, although carbide tooling and flood cooling will help. Aside from the hardness on the surface of your CRS which is due to work-hardening in the rolling process, it will also have a lot of internal stresses built up because of that which will make your parts warp as they're cut. You can fix that by normalizing it, which involves heating it up and cooling it slowly, but it won't be very hard afterwards, so you might as well have used HRS in the first place.

If you want it made from hardened steel, learn more about how steel works. Get some tool steel and anneal it (same as normalizing); heating it up to red hot and letting it cool down as slowly as possible (burying it in some kind of refractory insulating material like perlite or vermiculite works well). That will make it soft enough to cut. Once you've cut the part, then harden it by heating it up to red heat and quenching it in the proper fluid (this varies depending on the type of steel it is; some wants water, some oil, others will cool in air.) Once it's hard, you'll want to temper it, which means reducing the hardness so it's at the right degree of hardness for the job. You do that by reheating it to a specific temperature, far short of red hot, and then quenching it again. These temperatures can be roughly gauged by noticing the oxidation color attained by the steel when hot (it helps to have a clean section to observe). For a wrench, you probably want a purple color.

Andrew Werby
www.computersculpture.com