A really 'fun', tiny pocket

[lloydsp]

I'm making a precision blade-holder on a client's project for an X-Acto #11 blade, and need to mill a pocket in 6061 about 0.020" deep that retains the 'locater stud' all X-Acto blades have.  As such, the only endmill cutter I have that will fit between the stud and the edge of the blade is only 0.0625" in diameter.  And yes, it's an actual end mill, not a router bit.  They recommend 12K rpm and no deeper than 0.030" per pass at 10 ipm with flood for 6061.

That wouldn't be a problem at 12K rpm, but my mill won't go faster than 4200 rpm.  So BOY, and I going to have to cut gently and slowly!

I'm too tired this afternoon to be as attentive as I must be, so it'll wait until the New Year!

Happy New Year, ALL!

Lloyd

[Bob La Londe]

I remember when 1/16 was scary.  Putting myself in your shoes I share a little of your trepidation.  I used to use a .026 ball nose for slotting regularly, but I found a way to do that particular job with a massive 1/16 SE, and only use it occasionally now.   I do still 3D machine some features with a 1/32 ball nose.  Smallest I've run was 1/64.  I was running it in 4140HT for some press dies.  I broke a bunch of those. 

[Bob La Londe]

I'm thinking my way through a knife cutter right now for shortening shotgun hulls.  I'm thinking utility knife blade though.  More edge, tougher, and maybe cheaper. 

[Bob La Londe]

Happy new year.  May the new year bring you everything you need and a little bit of what you want.

[lloydsp]

Yeah, I've cut smaller than .0625" on my bed router, but it'll do 24K, so even tiny bits aren't a problem, so long as you get your feeds'n'speeds right.

There's a nifty paper tube cutter for pyro guys that uses a Fiskars rotary blade for the cutter.  They're saying they can get 400-500 'hard-wound' tubes with 3/16" walls cut with one blade.  A hard-wound tube is almost as hard as OSB;  the virgin kraft paper is impregnated with glue before parallel-winding, and the glue becomes part of the matrix.  The cutter's assembly is indexable so you can cut multiple tubes to the same length.

Lloyd

[Dragonfly]

I use a 0.9 mm 2 flute end mill for a batch of small parts to cut an elliptical slot  1.6 mm wide and 2 mm deep. But my spindle is high speed. So I use 12000 rpm with 0.125 mm depth increment and 80 mm per minute feed. In 6082 Alu. Blown with air and a bit of liquid spray. Made hundreds of them and only 1 or 2 broken.

[lloydsp]

Thanks, Fly.  I've converted your feeds and speeds to Imperial, and it'll be slow as heck at 4200 rpm (only 1 inch per minute or 25mm/minute), but it looks like it's 'doable'.

Your 0.9mm cutter is about half the size of mine, so I can probably (nearly) double the feed-rate.  I have five cutters, so doubling it is worth a try.

Lloyd


Lloyd

[lloydsp]

Well, that was a treat!  The job cut perfectly, in terms of the cutter's ability to handle it, and the pocket with island turned out clean and pretty.

I might even be able to increase the feed rate some.  The CAD of the X-Acto blade I received was wrong, so the blade doesn't quite fit in the pocket, but very nearly-so.  And now that I have a 'gauge', I can adjust my profile.

Thanks for the advice!

Lloyd

[lloydsp]

And... it fits!  Yay!  Now, I can actually mill the entire blade keeper.  I wasn't going to try, until I got this pocket figured out.

I was able to double my feeds, with no adverse effects.  These little cutters were designed for the task, and cut very aggressively (if you can call that tiny of a cut 'aggressive').  They throw clean chips, without a trace of clogging, with just mist coolant (aluminum specific fluid).

I call this a neat adventure!

Lloyd

[Dragonfly]

Glad I was of some help. Lloyd.
And that you did the job.

[Garyhlucas]

If you haven't broken a cutter by increasing the feed you don't really know what is possible.  More than once I've gone for 'broken' and cut the machining time by huge amounts AND the tool that didn't break lasted way longer too, because it actually did a lot less cutting.

[lloydsp]

I did a couple-more iterations of that pocket, because I want the blade to fit without more than 0.002" of 'wobble' in the holder.  I was able to almost triple my feed-rate with this style cutter, and it still didn't seem to have any issues.  I also did one 'deep' pocket with it (almost the full cutting depth of the cutter), and it never had a problem.  I even used it to pilot-drill a bunch of small clamp screw holes.

For only about $6.00 per cutter (in packs of 5), I'm pretty impressed.

I had another fun thing today.  This one was actually fun, not said in sarcasm.

I have an old BoreRite electric edge finder.  I keep it, because it has a rigid sensing pin, instead of a flexible 'wobbly-ball', so it's good when you need really precise detection.  But the bulb was burnt out.  They sell them, still, but they're all three days to a week out for delivery, and I needed it today.  So, I took a penlight bulb, some 2-mil brass shim stock, and some heat-shrink tubing, and made one.

Yeah, I wasted a whole lot more time than the $6.00 cost of a bulb, but I got it made today, and it works.

I've got a Starret gauge, a wobbly-ball electric edge finder, and a spindle-mounted rotary bore gauge.  But all of them are only accurate to a half-thou' or so.  My mill can position accurately to a tenth, so with the rigid pin of the BoreRite I can actually index to a tenth.

Lloyd

[Bob La Londe]

Aluminum with coolant will take as much chip load as the cutter can handle.  Just have to clear the chips. 

I use about the same speeds and feeds for aluminum and hard woods... okay I back off a little with ironwood, but ironwood has earned its name.  Mesquite (very hard when dry) cuts nicely dry at about the same speeds I cut aluminum wet.