[Coco] [coco] Coco CNC

[Gene Heskett]

On Wednesday 13 February 2008, George Ramsower wrote:
>From: "Gene Heskett"
>
>> On Wednesday 13 February 2008, George Ramsower wrote:
>>>I have that lead screw nut fitted to the slide now..
>>>
>>>http://coco.thetinbox.com/NewMillPageTwo.html
>>>
>>>It's fun to watch this thing work, especially knowing a Coco is operating
>>>it. So far accuracy on the Z axis is dead on and side milling is within
>>>.003
>>>inches. Not too bad for a dremmel.
>>
>> Looking good George.  Are you going to need to deepen the other end of the
>> groove too, to clear the screw as it protrudes from the nut?
>
> The groove is done and no further action is necessary. The end block on
>that slide needed a groove also, and room for the coupling from the stepper.
>I did that this afternoon on my manual lathe. I also made the coupler on
>that manual machine. Damned Chinese. When I drilled the 1/4 inch hole for
>the stepper shaft, the hole was .013 oversized and the shaft was .002
>undersized.

I've found that the drill bits I sharpen with a drill doctor are both 
considerably sharper, and very very uniform in the hole size they drill, 
primarily because the grind is so precisely balanced from one edge to its 
opposite edge.  The sharpness is amazing.  And where you normally get a 3 
cornered hole in light gauge steel with a 1/2" drill bit and only an 1/8" 
pilot hole, I found that by the time I was ready to hole through a piece of 
1/16" strap, the drill had contained itself and the through hole was round.
I used to pride myself on my ability to sharpen a drill bit by eyeball, but 
that machine is amazing.

>So I dug around to find a small enough 1/4 inch drill bit that 
>would make that hole. Got it within .003. Close enough!
> Right now, I'm brain working on mounting the stepper to the end block on
>that slide. Once done, I can put it back together and do the
>drilling(actually just making the pilot holes) for the working work surface.
>I figure I can mark the slide for the holes, and then use double sided tape
>to temporarily stick the working table to the slide and use the same routing
>to mark the hole positions on that, then take the slide and table back out
>to the shop for drilling a tapping. Should be error free this way.
> Can't beat automation for precision!!
>
>> I am getting closer to having the 4th axis working on my mill, a motorized
>> 4"
>> rotary table.  For a drive coupling, I re-used the coupling I originally
>> made
>> for the first rebuild of the z axis, but had to bore half of it out to
>> 10mm
>> from 8mm, which turned out to be fun.  I'd made those originally out of
>> some
>> sort of worn out mine shafting I'd found at the scrap metals place &
>> bought a
>> few feet of, and had fun making in them in the first place cuz it was such
>
> Most of my raw material comes from scrap yard/recycling centers. Pay by the
>pound stuff. I go in with a back pack, gather up anything that looks good
>and stuff that back pack until I had enough or couldn't find anymore good
>"stuff". Then go to the scales and check it out.
> For larger items, I will take my truck.
> All the roller bearings in my mill came from old VCRs. The steel bars the
>bearings ride on came from old dot matrix printers. The angle iron is from
>bed frames and the steppers, if I remember correctly, came from an old IBM
>hard disk >14" < and one came from a laser disk player.
> The transistor arrays to drive the steppers, I think, came from that laser
>disk or perhaps some other device that used steppers.
>
>> hard steel.  I pretty well wrecked a drill bit that was about 9.5mm but it
>> did go thru, but when I hit it with a small carbide tipped boring bar to
>> finish up the fit, the bar just slid off, so I wound up making a strap
>> bolted
>> to one of my quick change tool holders with a tab sticking out with a 1/2"
>> hole in it, put the hand piece of a flexible cable for a Dremel through
>> the
>> hole, and mounted a 1/8" diameter diamond coated ball burr from one of
>> those
>> ten dollar kits, and made about 20 passes through it to center up the hole
>> and enlarge it to fit the 10mm shaft.  Dremel set for about 5 thou, lathe
>> at
>> 50 rpm with its slowest gear feed.  Very very slow, but it worked.
>>
>> The last time I dealt with steel this hard was when drilling and tapping
>> my
>> P17 Eddystone Enfield action for a scope 45 years ago, where we had to
>> spot
>> the top of it with a grinder before a carbide tap drill for 6-48 screws
>> could
>> touch it, and the carbide tap had to be sharpened about every turn.  I
>> still
>> have whats left of both of them!
>
> That's the very reason I obtained a new drill press. Those bed frame rails
>are hard as heck. My old drill press would only go down to 650 RPM. A 1/2
>drill bit would smoke once it got into it. My new drill press is a floor
>model with something like fifteen speeds. It will go down to 300 RPM whis is
>just right for 1/2 drills.

I got one like that from Big Lots a few years ago, goes down to a couple 
hundred rpms, and up to over 5000.  The motor vibrates ANYTHING not clamped 
to the table off in 3 seconds flat though, so I get my deep bending 
exersize's picking up the chuck key from wherever it fell this time.  Its a 
vertical vibration at the table surface even with the belts off.  
Weirdsville.

> Any bigger than that, I'm sure I can bore it out on my lathe, if I fit it
>in there.
>
> Did you know that T-Posts, bed frame rails and something else(can't
>remember) are made from extrusions of old railroad rails? Yep! Saw it on
>"How It's Made" a couple of months ago.

No, but I've known for 40 years that bed rail was very high carbon stuff, so 
it doesn't surprise me.  Rather hard to weld with a smith wrench because the 
puddle is so explosive.

-- 
Cheers, Gene
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