How would i mill copper/delrin with miniature tooling? Please help a novice.

[touser]

Hello everyone, i recently purchased a small three axis cnc mill to begin a new hobby in machining, and one of my first projects is to machine a custom waterblock for cooling a computers cpu. However, part of my design calls for "jets" to be machined into 1/2" of white delrin with their diameter being about .05", however the spacing between them will only be about 1/64". My machine is only capable of spinning at about 6000 rpm, so my question would be: what type of tooling would be optimal for cutting delrin? hss,carbide, 2 flute, 4 flute and at what feed and depth of cut would i be able to run at assuming coolant is being used? The next problem is the base will be made out of copper where small "cups" will need to be drilled directly below the jets emerging from the delrin top with an outer diameter of about 1/16" and another small "cup" within the first with a diameter of about 3/64" of an inch. I know most of this information is probably uneccesary but i am very new to machining with no formal education and the only experience i have is with the internet coupled with trial and error. Any help on this matter would be greatly appreciated because from the looks of it these miniature tools are very expensive and i cannot afford to break too many with my trial and error learning

[High Seas]

http://www.boedeker.com/fabtip.htm may help
like Brilcream - a little google goes a LONG way! Cheers - Jim

[txcowdog]

High Seas
Although I wasn't looking for such a web site, I'm going to tuck that one away for later use. Thanks.

[fredhh47]

Delrin is not bad to machine, but don't crank the RPMs as that will result only in melted delrin. Spot, or center drill your holes with a #0 center drill, to avoid drill-point wander. Use a .050 diameter drill and a "full-retract" type drill cycle. This will prevent the flutes from becoming filled with delrin chips and reaming the hole out a good bit bigger than you want. An Air-mist aimed directly at the top of the hole will also be of great value, but be careful that the pressure of the mist spray doesn't cause the drill to deflect. Use about 1000 RPM and a "peck" of maybe 1/16" at a time. Watch the drill when it retracts. If the flutes are full of chips, reduce the peck amount. If you're just getting a little bit of material in the flutes at the end of the drill, try increasing the peck. As for your 1/16" and 3/64" cups: if I read that right, you're going to end up with a 3/64" hemispherical depression with a .0075 countersink around it? Anyway, you can "drill" with "ball end" mills. They have the radius ground on the end of the mill, so you can make the spherical depression you need. I'm sure that you can get them from industrial suppliers like Travers Tool (www.travers.com) and McMaster-Carr (www.mcmaster.com). Fred

[touser]

Thank you for the replies i really appreciate it! I should have included pictures of about what i am trying to do. Here is a picture of the cups i was referring to:
except my design will have a 2nd smaller cup within the ones already there. For the "jets" i am going to make something very similar to this:

which is why such small tooling is going to be required to make the islands where the jets stand. I have been scouring the forums and google sense my post trying to figure out how to calculate a safe feed rate for such miniature tooling in delrin and copper sense ME Consultant does not support anything smaller than 1/16" but so far all it has done is confuse me. Does anyone have any suggestions on what my depth of cut should be with 1/64" and 1/32" bits in delrin and copper? Will half the diameter of the radius do? How do i determine the appropriate rpm/feeds for those two materials sense the only material i have any minute experience in so far is aluminum. Thank you all for the help i really appreciate it, without this forum i would be truly lost!
Also, here is a link to the article which the pictures linked above came from which shows more pictures of the final product: http://reviews.pimprig.com/cooling/c...old_blocks.php

[NeoMoses]

I really have no experience milling delrin, but I do have a little experience turning it. In the waterblock days, I was using all copper, aluminum, and brass. If I recall correctly, delrin doesn't chip very well. With these tiny endmills, chip clearing will likely be your biggest problem. A good rule of thumb I used to use was to cut no deeper than 50% of the endmill diameter per pass. If I wanted to be cautious, 15%-25% of the tool diameter is a good starting place. So, if you're using a 0.015" diameter endmill, 15% * 0.015 = 0.002" would be a good starting depth to ensure you're clearing chips.

Feeds & speeds in delrin I'm not so sure about. My real experience is pretty weak here.

I'm a little rusty since it's been almost 3 years since I was producing waterblocks. In copper, though, you'll want to use 2 flute endmills. Pure copper is really soft and doesn't chip well. I'd recommend carbide endmills.

Double check this info before using, but IIRC, I was using something around 400 SFM with carbide in copper, maybe 100-130 SFM with HSS in copper. I was using a soluble oil flood coolant to lubricate/clear chips. I don't honestly recall the feed speed or chip load I was using... Maybe 10 IPM with a 1/8" carbide endmill, 5000 RPM. I think I preferred about 0.030" per pass with this setup to get good chip clearing.

As always, double-check this info, and your mileage may vary. Hope it helps!