[woffler]

I have a part that i am cutting with A carbide 1/8 dia. end mill 2 flute 3/4 loc through 5/8 6061 alum. Problem is no matter how i hold it if on a tool plate or in a vise .I am breaking end mills on the final pass may cut out two or three and then one will cock and bind and snap goes the wiesel .Any one have an idea how to elimanate this problem? Thanks

[jalessi]

Woffler,

What is your DOC, spindle speed and feed rate?

Jeff...

[woffler]

Spindle speed 1750 feed rate 3ipm doc .15

[jalessi]

Woffler,

I neglected to ask what step over you are using?

Your spindle speed seems very slow for what you are cutting.

Jeff...

[jalessi]

Your depth of cut is three times to much by the way, try 1/3 the diameter of your tool.

[diggityds]

CRANK THE SPINDLE UP TOO MORE THEN 3000, GO EASIER ON THE DOC MAYBE .020, SPEED UP THE IPM BETWEEN 15 OR 30, AND FLOOD THE LITTLE SUCKER COOLANT IS IMPORTANT. IN GENERAL KEEP THE CHIPS SMALL ON TINY FLUTED END MILLS

[jalessi]

http://www.datrondynamics.com/pressroom/RPM004.pdf

[diecutter]

I think woffler is saying that on the final pass the PART will move and jamb the cutter against the aluminum plate just as it seperates from the plate.

If this is the case you need to add bridges to hold the part, or secure it in another way before the full profile is cut. If the part has a hole in the design, you can machine all the parts except for the final pass, then pause and run a bolt through each hole and then make the final separation cut. I'm sure others will chime in with more methods.

[woffler]

Thanks to everyone for responding The speed is limited to 1970 rpm and you are right it is on the last cut that it jams aginst the plate .I will boost rpm all the way up and i am looking for a faster motor to get my spindle speed up geared head mill .I am using full flood cooling i will will reduce my depth of cut and make more passes there are no holes to anchor the part .The part looks like a long shaft with a hook on one end only .125 wide and 4.0 long lots of room for vibration on final bottom pass .

[jalessi]

Woffler,

Post a picture of the part, maybe someone will have a solution.

Jeff...

[davereagan]

A picture would be priceless. I strongly suspect the slot is closing up and pinching the endmill on the final cut.

[LeeWay]

On my steel sheet parts, I leave tabs or just a little foil under the cut. IOW, leave out the very last breakthrough pass. I then just bust them out with a bandsaw. It does need a little deburring afterward, but don't have any movement of the fixtured part.

[wildwestpat]

Hi Folks

I recall one guy solving this sort of problem from way back with double sided sticky tape to mount the thin sheets he was cutting to a scrap sheet of what I think was MDF or hardboard that he had soaked in something - probably celulose paint as a lot of the work was dipped prior to storage / inspection at a later stage.

Also sounds as if you might do better holding the part and the scrap down with clamps moving them as necessary but not removing them. The scrap has to be held as well as the wanted part or else the cutter gets pinched and breaks.

If my memory serves me right the stuff being machined was a lattice work of aerial support stucture for a small satelite dish that was to be an investment casting after machining from the solid had proved the dimensions etc. The sections were very light and in consequence the cut depth and rate of feed were comensurately light.

I think the jewellery fraternity make use of what they call dopping wax for similar purposes to mount difficult to hold parts for machining or hand work. The way is warmed and used to stick the part onto a backing piece which becomes scrap as it is also cut on the final run.

Hope this helps before you run out of tools or patience. Take care as these sorts of part can get picked up by a fast moving tool and can inflict real damage.

Good luck.

[wildwestpat]

Hi Folks

Forgot to add that the parts we about the size of a half pound of butter and there were the ocasional screwup with the tape giving up. The jobs were aditionally held using conventional pivot clamps but in the latter stages ther would not be sufficient metal remaining to permit mechanical clamping. I don't recall the final cuts as being the problem as the breakaways were during the initial roughing out.

Hope this helps and you can find some suitable double sided stick tape.

Good luck and stay safe.

[woffler]

Thanks for all the help still working on it here is a dxf file for those that can open it .Ill try and get a pic as soon as i can find the dang camera!!

[woffler]

Ok here is a jpeg image could not figure out how to get a thumb nail in the reply though hopes this helps . And again thanks for your very kind and genoures help.

[MrWild]

Fixturing is everything. I'd make it with a thicker material, make it to size, then lip it, set it in a female fixture and machine the back side off.

[mc-motorsports]

Are you trying to just "drop" that out of plate or bar? As in hanging it out of a milling vice and profiling? You'll have problems trying to "drop" anything thicker than 3x your EM diameter.

[jalessi]

I would make a fixture as Mr. Wild suggested.

Machine part to finished thickness + .025

Make Delrin fixture with a pocket that flipped part fits in.

Flip part, insert part in fixture and face part.

The fixture could be designed to expand and hold the part if needed.

Jeff...

[LeeWay]

I did something similar when I made a few guitar pickups for a Buddy.
I just held the parts in a vise. Then flipped and faced. I didn't need an extra fixture as you would, but you can see how well that should work.

The speeds and feeds on this video were less than about half of what I could use.
[ame="http://www.youtube.com/watch?v=9eyA2kq7lDM&feature=channel_page"]YouTube - Milling Brass guitar part[/ame]