If only I could go back in time.  Woke up this morning realizing since I already had a 1/4" hole center where the 12mm hole needed to be, I could have created a toolpath to plunge in the hole with no need to ramp into the aluminum, and then have it pocket out down through the block.  Even if the 1/4" hole wasn't perfect the 3/16" bit would still drop into it then make a perfect 12mm hole.  Two things I wanted to avoid were ramping in and full width passes. While I don't plan to make another aluminum stop I've put the almost perfect last one back on the CNC to correct the slightly wrong 12mm hole.  Yes what I'll have is a slightly oversized hole, but at least it'll let the post pass down through the button which should be perfectly centered. 

4D

Got the elliptical pocket and spring socket cut.  Other than softening the sharp corners with a little filed chamfer this part is done.  I drilled a center hole using my drill press before putting the part on my CNC so I could plunge into the center then move around to cut the perimeter.  22 steps and about .75" of depth.  Last thing is to cut the button that slips into the elliptical hole.  Still contemplating the best way to cut it. 

4D 

Looks pretty darn good from where I sit 4D. I just cleaned my glasses too.

Having a little more trouble making the elliptical button for this depth stop collar. A spinning bit likes to take advantage of any weakness in how the part being cut is clamped down. 

I started with a 5/8" diameter aluminum dowel. 

3D rounded off the end, then cut a flat on the side with the dowel clamped vertically.  No problem so far.   

Then clamped it in my low profile CNC vise with the flat spot up to have the CNC mark with a V-bit where the M12 tapped how was to be centered. 

Took it to my drill press vise, and drilled the center out with a 1/4" drill bit.

Back to the CNC to have the 10.8mm hole cut.  Worked fine. 

Took it off to tap that hole with a M12 tap.  Worked fine.

Back on the CNC to cut the 12mm hole next and overlapping the tapped hole. Worked fine.

With all the holes done, the last task was to cut it into an ellipse shape.   Clamped vertically, but apparently not well enough. CNC gabbed it, knocked a C-clamp off, twisted the dowel before I could hit the e-stop.   

Rethought how to clamp it solidly.  Moved my low profile vise to my vertical jig.  Put the dowel in that vise and added a couple clamps to hold it there with the end sticking up.

Slowed down the same CNC file that had bit me before, and finally succeeded in getting the end cut into an ellipse. 

 

All that was left was to cut the elliptical button off the end of the dowel.  I have a metal cutting chop saw,  I can cut aluminum on my band saw, but not as cleanly. Gave the chop saw an unsafe try proven by the nip it took from the tip of my finger as I tried to hold the small part to be cut. Would have cut it if I could have held it tight, but I didn't. 

To clean up the end I went to my disk sander.  Need a new disk apparently as so far all I've made the little aluminum button is too hot to handle. Left in my chilly garage to cool down. 

 

4D

4 minutes ago, 4DThinker said:

by the nip it took from the tip of my finger

OUCH!

Button cooled down.  Took it to my bench vise to see if I could file off the last bit of the bottom surface.  Got it close enough to see if it would work with the collar,

Answer is Yes.

Not without a few scars that you can't see when in place.  Seems better of a stop than the HDPE version I started with, although that may just be because it makes more of an audible snap when the threads engage than the HDPE version did.  Some play due to the slightly oversized hole I started with, but that doesn't seem to effect its functionality.   A little rough in a close up view, which doesn't seem to effect its functionality either. 

 

I have enough aluminum left to make another.  Likely won't.

Having followed through with #2 to where it works OK I have confidence now that I can make aluminum parts on my cnc,  I just can't rely on all the experience I have cutting wood. It took actually trying to make something from aluminum to point out the differences.  

4D

2 hours ago, 4DThinker said:

Gave the chop saw an unsafe try proven by the nip it took from the tip of my finger as I tried to hold the small part to be cut. Would have cut it if I could have held it tight, but I didn't. 

To clean up the end I went to my disk sander.

Would that be the button or the end of your finger?  Seriously, glad you're OK.

14 minutes ago, Grandpadave52 said:

Would that be the button or the end of your finger?  Seriously, glad you're OK.

The saw blade kicked the part out of my grip,  Didn't realize any damage until i saw some blood on the table of my disk sander.   Apparently when the button went for a flight it (the part not the blade) scratched the tip of my forefinger.  No stiches required. Just a band aid.  

4D

A side note, related to how the cnc software works.  In the photo above I'm surprised how faceted the ellipse surface is on the button.  When I import vector files from other software curves are almost always broken up into many short straight vectors.  In Aspire, when I draw an ellipse or a circle they both are made from 4 arcs/4 nodes.   When cut on my CNC arcs are cut with a continuous smooth motion from node to node.  Yes, there is a tiny amount of pixilation in X/Y stepping,  but with resolution accuracy down to 1/1000" no faceting should be showing.  Somewhere between the vectors being drawn, and toolpaths being made, and the cnc controller interpreting and turning commands into stepper motor movements the elliptical shape got converted into a sequence of short straight vector movements.   Yet the elliptical hole in the previous photo shows no evidence of faceting. 

I've looked carefully at the files used for both cuts.  Node editing shows no ellipse with more than 4 nodes.   I've apparently found a ghost who teases me with results I'm not expecting. Faceting where there should be smooth surfaces.  No explanation I can find otherwise. 

4D 

A few days have past. I've had time to reflect on my adventure cutting aluminum with my CNC, I have concluded that I truly enjoyed the adventure and feel good about having learned something useful I can apply to future projects. 

There was a moment in my teaching past that a student asked if I could cut brass with the CNCs we had. He  wanted to cut a small pocket into a brass buckle so he could inlay something into it. A 1/16"d bit would be needed to get into the tight corners of the pocket shape.  Clamping his brass part down was no challenge. The task broke 2 bits before I gave up.   I blame the bit breaking on the known fragility of tiny router bits.  The students was disappointed, but as the request was for a personal project and not a class project he understood. 

This brings me to wondering if I CAN cut brass on my CNC if I apply what I learned about cutting aluminum. Anyone know off the top of their head how hard brass is compared to 6061 aluminum?  Is copper softer?   I might see if I can make a brass or copper version of my depth stop collar for the fun and educational challenge. 

4D 

Brass should cut fine.  I would suspect the broken bits came from vibration and lack of lubrication which is usually sprayed on the bit while it is working.  Brass will also adhere/braze itself to the bit if it gets hot enough.   

Thanks Dan.   I just ordered some 360 brass from McMaster Carr to play with. A .75" x 1" x 6" bar and a 12" length of 5/8" diameter round 360 brass.  I've been searching Google to see if anyone makes router bits for cutting brass and so far have only found one 3 flute 1/4" upcut coated bit that was suggested for aluminum.  I'll have enough brass to make several tries.  The 1" wide bar means I'll only have to cut the beveled corners and round top as profile cuts from it, I'll pre-drill starting holes for the 12mm hole through the top and elliptical hole through the side of it so no ramping in will be needed.  I've got some thin machine oil, and possibly some WD-40 I can use while cutting if needed. 

4D   

Brass arrived today. I've been contemplating what steps I need to cut the parts from the brass bar and dowel.  Small steps. No full width passes.  No ramping in. 

Step one render from my CNC software. Cut the corners, chamfer the top perimeter, and mark the center where the hole will be.   I'll see how reality turns out tomorrow morning. 

4D

Step one done.  No casualties. a little harmonic vibration from the bit when climb cutting the angled corner toward the block but not on the other side.  Any artifact of that was erased with a final conventional full depth pass.  I should have cleaned up the front end of the block as the chamfer cut reveals it is a tiny bit out of square.  I'll add that to step 2 which will be to drill a starting hole using that divot for the 12mm hole the part needs that will be CNC cut.  After this photo was taken I remembered to flip the part over and run that chamfer toolpath again on the bottom side.  The part is held in my low profile bed vise, with an end stop on the far end so I can take it out and put it back in exactly the same place. 

4D

Should have stopped when I was ahead. I had the part cut from the 6" block. My wood cutting bandsaw didn't seem challenged by the brass. I bolted it down to the t-track, with a 1/8" scrap of plywood in between it and the track. Lock washer and nylock nut bearing down tight and a scrap of plywood against the flat face to make sure it couldn't turn. 

I climb cut the curved end.  22 passes and only some more of the harmonic vibration on the x+ moves, which I think may be due to some backlash in the X axis.  I had a conventional direction full depth pass programmed to do a finish pass just to clean off any material the climb cuts may have deflected over. Half way around and hell broke loose. Suspecting the backlash again as before I could react the bit had grabbed the part and jerked it down the t-track to make a perimeter mess of the part.   Lesson one: plywood doesn't make a good shim material. Lesson 2: I've got some backlash in the X direction I need to consider as well as look into fixing.  I've replaced the feed anti-backlash nut once already. 

This part isn't ruined, just transformed from what was a shiny smooth brass perimeter to a choppy "texture" in the blink of an eye.  I have a drill press that senses unusual forces and stop the process.  I'd love to see a similar feature for CNCs.  Even if I'd had my hand on the e-stop there was no way I could have reacted quick enough to hit it once this cut went awry. 

4D  

I wish I'd been recording that last cut in slow motion.  Love to watch and learn exactly what happened and when in the cut,   I have 5" of that brass bar left, so I'll start again.  The first step is done with the bar in my vise.  First try everything worked out fine. I've had no problems with any cuts when using the vise to hold the material.  I'll have to re-think the second step which is when the part is held down with a center bolt.  I'm pondering how to deal with the backlash.  Every failure point so far, in both the aluminum and the brass I see now could be blamed on that backlash. Conventional cuts that tend to deflect toward the part I need to eliminate all together.  I had this first try looking great just before that one conventional pass which I didn't really need to do. 

4D

Edited January 25, 20233 yr by 4DThinker

Well, with serrations it will be easier to grasp. At least my S&W's are easier to grasp and "rack".

1 hour ago, Grandpadave52 said:

Well, with serrations it will be easier to grasp. At least my S&W's are easier to grasp and "rack".

True, but in use you just squeeze the button in with fingers on the back and thumb on the button.  The origin depth stop nut had a knurled perimeter because you had to spin it. 

I've redone the toolpaths so all but cutting off the part can be done with the part in my low profile vise.  Once cut off the part is reclamped with the flat face up to cut the holes for the elliptical button.  I'm going to wait until tomorrow as my mind often comes up with problems I hadn't foreseen or simpler solutions overnight. 

4D

With metal working a strong hold is required and increases with hardness of the metal.  My Unimat Hobby Lathe cuts brass well but can be a problem when pushed over it's limits.  Move up to my 6" metal lathe and I get a lot more work out of it but it can be pushed over its limits too.  Not sure how strong your frame is but you need to find it's limits too.  I turn found brass and never bought any to turn.  I have noticed some pieces turn easier and it seems cuttings are brittle.  I think it may be bronze.  I'm glad you are doing this and following this thread to see what I can learn from your endeavor.  Carry on.   

Edited January 25, 20233 yr by HandyDan

When I was student and a professor I had access to a milling machine.  Put a block of aluminum or even steel in a big vise bolted to a heavy X/Y bed.  Use 4 flute milling bits made for the task. Hand crank the bed handles to move the material relatively slow into the relatively slow spinning bit. Flat surfaces/faces easy. Complex shapes were done with metal cutting band saw, files, grinding tools, etc..  Something that 

My CNC does fine with any wood.  I did occasionally come across learning opportunities when the CNC would pull up or push a board sideways unexpectedly.   Something those who now have use of the CNCs I oversaw will eventually learn too. 

Cutting metals I never expected to do with my CNC.  When I needed a metal part made I had access to machines I don't have access to any more.  There was a moment in time I found a company that took small milling machines and added stepper motors to each axis making them CNC controllable. I tried to get the college to buy one but they claimed they had that ability in an ancient bridgeport milling machine that just needed figuring out.  I knew the controller on it was simply a numerical readout and not capable of controlling the 3 axis with G-code. The motors it had you could jog by pressing buttons on the controller, but there was no method or port for adding a toolpath sequence.  No computer interface.  

What intrigues me is the potential of making more complex parts using my CNC than I can make using the other tools in my shop.  This push button depth stop collar is a good example.  I designed an elliptical hole for an elliptical button so there would be no need to rotate the button to align with the post hole when assembling.   I have no other machine that makes elliptical holes or method for machining a round dowel of aluminum/brass into an ellipse.