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Custom endmill questions.

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Scruffy887

Titanium
Joined
Dec 17, 2012
Location
Se Ma USA
I machine thousands of HDPE parts on a vacuum chuck. Currently I finish the perimeter with a .75 HSS endmill and top edge with a 1/8 round over.
I would like to do both in one operation and the cutter needs to be a spiral because it will also do a pocketing operation.
3/4 shank tool with the correct profile will have a 1/2" emill cutting diameter.
Any ball park ideas on cost? I would buy more than one.
Carbide is an option too because once in a great while the part comes off the vacuum chuck. Most of the time it just ruins the part. But once the pocketing operation grabbed the part and spun it at 6000 rpm. Much damage from high velocity heavy part. A carbide cutter would snap, that would be a good thing.
 
Check AB tools. Click on their product catalog, they list prices for 'base' tools. Should at least give you ballpark price.
 
I would get a couple quotes as custom tooling prices can have a huge swing from high to low. If you go with carbide I can't see it being under $100 if they have to start with a 3/4" blank, and I wouldn't be surprised to see a quote around $500. I could be totally off but that is what I would expect to see.
 
If I’m following you want a 3/4” endmill with radius corner rounding edges? If I’m right I would think I could provide something like that for $200 or so.
 
If I understand correctly, the 1/2" 'endmill' portion would need to be of significant length. You don't say how wide the perimeter is, but that would be essential information for an accurate quote. A 3/4" blank 4" long with 2" straight at 1/2" prior to the corner-round is going to cost a lot more than something ground to treat a 1/4" perimeter. Is the pocket depth the same as the perimeter? If its shallower, I don't think you can do all ops with one cutter unless the pocket top doesn't need to be rounded.
 
Since you are cutting HDPE and I assume you need it to have a decent finish the tool you are looking for is pretty special so be real careful. Everyone will say they can make what you are asking for but damn few can make the tool you are asking for that will actually work. If I was looking for it I would be real cautious. In carbide, might as well as it won't affect the price much, you are probably looking at over $300 a tool if you get 3. It would really suck to get your new tools and find out the end mill portion has very little rake and doesn't cut worth a shit.
 
For HDPE you could make a corner round cutter that would slip over the shank of 3/4 end mill. It could be held in place with set screws, silver brazed, or welded.
 
gbent said:
For HDPE you could make a corner round cutter that would slip over the shank of 3/4 end mill. It could be held in place with set screws, silver brazed, or welded.
Click to expand...

That is sort of the current plan. But I am thinking along the lines of using an extra long drill bushing .501 ID by .75 OD. Grind the cutter shape and slit the bushing like a collet to clamp onto an ordinary .5 end mill.
 
Having a surface grinder and a radius dresser you might grind an end mill end with a 1/8 radius straight across at 90* straight up held in a V block. Then rotate it to the left .055 and grind up to a land and the just wipe out the land to sharp. it will grind a little one side but not enough to hurt the 1/8 radius. then by hand grind a secondary to look reasonably straight. likely take an hour or less. Yes you can cant the V Black 2* for a little end axial clearance..

Yes with not having a radius dresse you might just hand hone dress a 1/8 radius with the likes of a Norbide stick of blade of carbide to the whaal. likely a 60 L would be a good wheel,
 
Last edited:
If you spin a 3/4 down, you're gonna wind up with one of the problems of regrinds, on steroids ... the rake in the flute gets reduced. You're probably better off with the bushing idea. I kinda like that one.

To add: A 1/2" ID bushing is going to be a feather edge to get a full radius. Might need to machine something up with some nubs extending into the flutes. Or a 3/8 shank tool.
 
I had a custom carbide router bit made at my last job for cutting HDPE to do 20 degree valve flange under cuts, plunge into center to remove the center and a little tit on the end to cut an o-ring face groove. Worked really well for us. I also had a cutter like you want ground from a larger center cutting end mill. They simply ground the diameter down and left the radius at the top, then relieved the flutes on the reduced part. Used it on aluminum.

Send the vendor a solid carbide end mill that is already dull on the end, it gets ground off anyway!
 
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