Step 7: Undercutting + Chamfering

Time for the undercuts.  This is very similar to roughing the bores.  This time around, we want power feed on the X axis, as we won't be doing much on the Z axis.  Note that the X axis feed is about 1/3 to 1/2 of the Z axis feed, you can test this with a dial indicator on the carriage and watching how the cross slide moves when the power feed is turned on (example, if the feed is set to 0.010, and the cross slide only moves 0.005, then you know that it's 1/2.  I'm sure you can guess what It would move if it was 1/3. Easy stuff.)

1) Put your undercut tool in, set it to centre height, touch it off on the face of the cube with paper, just like we did last step with the boring tool. (Picture # 1)

2) Move it to the side, set up the dial indicator again, yet this time move  to full depth (0.625 + 0.003 for paper), and set the  indicator to 0.

3) Now we need touch off on the edge of our bore and set the cross slide hand wheel micrometer collar to 0 (since we know that the bores have to be 0.200 and 0.350 bigger).  Move the tool to depth (we only cut to 0.615, so the dial indicator should be at 90) and move the tool to touch the edge of the bore.  I just turn the chuck by hand, and bring it closer and closer till the tool JUST scrapes the edge.  We're going to be cutting here, so don't worry about ruining the finish or anything.  You could try and use the paper again, but it's an awkward place to get to, and makes it more complicated then it needs to be.  Once you touch, set the collar to 0.

4) Now we can turn on the lathe (you can bring the tool out, we know where it needs to go.) Move the tool into the correct depth, and turn on the power feed, so it begins facing off the back to leave a nice finish.  Watch the collar, so you know that when it passes 0 you're at the edge.  Turn off the power feed and continue by hand.  Make your undercut now, by expanding the diameter 0.200.  Once you get to 0.200, pull the carriage 0.010 back towards you, and bring the tool out.  This is so you don't scrap back along the nicely finished face you just made.  Pull the tool out, and your first undercut is complete! (Picture #2)

5) Do the same thing for the next size.  Touch off on the face of the cube, move in 0.316 (0.313 + 0.003 for the paper), set 0 on the dial indicator,  touch off on the edge of the bore (1.500 bore), set 0 on the cross slide collar, turn on the lathe, cut the depth, power feed face cut to 0, hand feed the undercut so the diameter becomes 0.350 bigger, retreat the carriage 0.010, and bring out your tool.

6) Chamfering time, to give nice edges on your bores.  You can make these chamfers as big or as small as you like.  Mine are about 3/64.  For the outermost cube, you can do it on the mill when you are making the cube, or just do it with a file.  For the inner cubes, follow along here.

7) Use the countersink to put a chamfer on the 9/32 hole first.

8) Using the 90 chamfer tool we made, set it to centre height, and chamfer the other two bores.

9) Voila!  Side 1 of your cube is complete!  That wasn't so bad, was it?  All you have to do now is repeat the same operations on the other 5 sides.  I find it best to do opposite sides (Imagine a dice, do side 6 and 1, 2 and 5, 3 and 4.).  I think that it keeps the most material in the right places, and its easy enough to dial in each time.

- When you get a few sides done, you have to balance the shims so that they cover the holes, yet leave enough room to dial in
- Always work on the smallest cube first, then the middle cube.  Work from the inside out.

For the final side:

10) You have 5 sides done, the cube is looking excellent, you've finished the bores on side #6, now you're ready for undercutting. STOP!!! Here we are switching things up a bit.  As soon as you undercut, the cube will fall apart.  So we need to chamfer first.  Chamfering the biggest bore is the same as always, but chamfering the middle bore and countersinking the 9/32 hole need to be done a little differently.  You're going to be facing these two surfaces off (removing 0.010), so make the chamfers a little bigger then the others, so when the surfaces are faced, they become the right size.

11) Now proceed as normal, cut to your depth with the undercut tool, begin power feeding the face, when you reach the edge of the bore (0 on the collar) TURN THE MACHINE OFF, LEAVE THE POWER FEED ON.  I learned this the hard way.  When you try to turn the undercut, as soon as you reach the final diameter, the cube will fall off.  Now, when your machine is spinning at 600 RPMs, that little cube begins bouncing around inside and smacking into your tool and gouging the heck out of itself, ruining all the nice finishes you've put on it.  My idea to solve this was drop the RPM to as slow as it can go, and get ready to stomp on the brake as soon as the cube fell off. My teachers idea was much better, so we'll be using it here.

Now you should be touching the edge, ready to undercut 0.200. Just start spinning the chuck by hand.  Since you left the power feed on, the cross slide will continue moving along, and you can make your cut this way.  Now, as soon as you hear/see the cube fall off, you can stop spinning.  No ruined finishes!

Note:  Sometimes the cube will not fall off right away, even once you get to the 0.200 undercut (or 0.350).  This should be fixable, its just the slight errors accumulated, and there may be a few thousandths left on some of the corners, holding the cube on.  Just use something soft to smack that cube out.  I used a piece of wood and hit it with a hammer a few times. (my middle cube got stuck on one of my prototypes).  When you are cutting the undercuts on side #5, you'll be able to see if they will be big enough to break the corners.  You should be able to see the corners free floating, ready to fall apart when side #6 is cut.  If the corners are still attached, then you messed up somewhere.  Recheck your calculations.

12) Do the same thing for the next undercut, use the "hand feed".  Power OFF, power feed ON.  Spin that chuck!  It's really not so bad, you may think that it'll be horrible spinning the chuck by hand, it's really not, but if you want you can just use power feed to get it close, then spin it by hand for the last little bit.  Or try my stomping on the brake idea.

Now you have your very own beautiful Turners Cube!  Not one built by a robot (CNC), but one built with your own flesh and blood and manual power (hopefully not too much flesh and blood!)

How much width for under cutting tool?
<p>Approx 1/8 in.</p>
<p>if you were to make this from steel rather than alloy, you could be really cheeky with the center ball by using physics. if the finished cube set was evenly heated the metal would expand enough to be able to trap a ball bearing in the center,. best option would be to heat in a brine, that way you would get even expansion. just find the right size bearing and chill it before fitting. the brine would also colour the metal as it is how firearms are blued. just a suggestion from an engineer with a nerdy side.</p>
<p>the heating process would also remove any hot glue used to secure the cubes for finishing.</p>
<p>i want to download the attached file i don't want to go with pro registration any way to get it????</p>
<p>This is great reading! I don't have a lathe but if I did, I'd certainly be spinning up some aluminum in short order. There's another YouTube video out there somewhere in which the machinist filled the first five bores and undercuts with hot glue. You can see the care he used, as the metal certainly absorbed a good bit of the heat, making the cube a bit more challenging to handle while he filled the remaining bores. It allowed him to perform normal speed cuts on the sixth side.</p>
Hello. It is very inspiring work. but i dont have any talent for it. Can i order a turners cube from you to turkey? :)
<p>Really Nice instructable, can you please explain what a PLANAR Bar is , I haven't heard of it before.</p><p>thanks.</p>
Planar bar is basicallt a round bar with one edge ground flat.<br><br>The flat end rests on the vice, the round end touches your piece, and makes sure that there is only one point of contact, forcing the other side of your work to be parallel with the other side of the vice
You can also make a set of step-cylinders which nest into the bores. These hold everything in place as you do the final undercuts, and generally reduce the risk of damage from clamping forces.
You can make a sphere in a cube... Using an inverse ball endmill plunged from all six sides.
I was wondering how to do that... We saw an example of that, but it was made on a CNC. I imagined it was just a small endmill (&lt;1/4 in) and some fancy programming to get the angles required for the circle. But inverse ball endmill would be perfect! <br> <br>It would still be a bit tricky though, because you'd have to make the hole smaller the the diameter of the ball, and that would make it tricky to get the endmill in. <br> <br>I may be getting some more time in a machine shop.... Perhaps I should try it to see how it works out.
The endmill dictates the hole diameter.<br><br>When I was in machining school (Warren Occupational/Technical Center in Lakewood, CO), we learned to grind the radius into the endmill. The trick, for this part, is to cut a larger radius than the cutter. The resulting ball will be larger than the hole when plunged through from six sides. But will remain attached to small support surfaces at the corners.... This is serendipitous, as you wouldn't want the aluminum ball coming free and bouncing into your fragile cutter anyway.<br><br>Once the manual machining is complete, Go back in with a jeweler's saw and free the ball.
Ahhh.... But then you'd have rough saw marks on the ball... <br> <br>If you did plunge in fully on 5 of the sides, on side 6 you could stop, and do similar to what I did in Step 7, for the final side. Just stop the mill, and turn it by hand, so the ball falls off nicely and you dont have to deal with it spinning at upwards of 1000 RPMs :D
If you plunged it completely on 5 sides, you'd have a sphere that isn't very spherical.<br><br>You clean the jewelry saw marks up by hand with your trusty needle files and maybe sandpaper. A machinist worth his salt can turn file marks into replica machine-tool marks. I do it often... And polishing the whole assembly to a bright finish is even easier.
VERRY GOOD! <br>i use to do this by hand in Wood.
Do you have and pictures of wooden ones you could share?
these are my Uncles. My mother has mine <br>i have done copies of all of these Except the 3-interlocking rings on the left <br> <br>
Pretty wicked! Should try making some of these out of metal
it MAY be possible. I'd love to see it if it is. <br> <br>however, the wooden models are only possible because of the ability to use a knife and the sheering properties of woodgrain. <br> <br>One whittles down most of the joint, SNAPS the remaining web, then uses the knife and sandpaper to smooth out the roughness. <br> <br>To achieve the same results in a machine operation, using metal, would probably require an EXTREMELY delicate bit, a very high rpm machine spindle, and a 5-6 axis machine. The very fine, fiddly work your hands do naturally with a knife blade are impossible to replicate in a 4 axis machine. And nearly impossible in a 6-axis. <br> <br>Check out the 5:30 mark on this youtube video for the sort of fiddly maneuvers needed by a machine tool to replicate a fairly simple hand-tool woodworking process. http://www.youtube.com/watch?v=GU32Q6QXtWQ <br> <br> <br> <br> <br>You COULD replicate these in metal, fairly easily, but it would involve casting, not machining.
here are some better photos of the plier joints
Looking at this actually makes me giddy. I love it.
This is really cool, I took a manual lathe class as a pre-req for a bunch of engineering classes a few months ago, I think I'll try this.
Do it!
now I know what I'm making when I gain access to the lathe at my college (and learn to use it). I remember the first time I saw one of these, I just thought and thought and thought until I figured out how it was made. it's shockingly simple, you just need good spatial sense.
Most things are a lot simpler then we think they are. Just take it one step at a time, and before you know it, you're done!
Little typo: &quot;Male it Real&quot; challenge. Thought that I was reading Cosmopolitan for a minute...
Oh my! Thank's for pointing that out. Fixed!
WONDERFUL!<br><br>You beat me to it, but glad to finally see a REAL turners cube!<br>Not saying the &quot;attached nested cubes&quot; aren't fun to look at, but this requires a great deal more skill. And make better playthings for when you have grandkids.<br>Also glad to see you did the double nested version(so much more impressive than a one-in-one)<br><br><br>As I understand it, this was an apprentice job way back in the day.<br>And it was done entirely on a lathe(this being WELL before computers, heck most shops at the time didn't even have electricity!)<br>It was a testament to the young man's skill, to be able to make the 6 facing cuts, to get a cube. Ok, it was a REQUIRED BASIC SKILL. :-)<br><br><br>Step 11, on the final side cutting... that's an interesting technique!<br> Sure would have been quicker than how I did it.<br> I ended up making 5 stepped plugs, with 1-2 thou clearance.(4 jaw chuck, plus a backing plug). Obviously, all 5 plugs were turned on the same lathe.<br>The main advantage to having plugs is, you can have the machine running the whole time. You don't have to turn the chuck by hand for the last bit. Also eliminated the need for using your shims :-)<br>
I'm just finishing up my final project at school, then I'm going to make the &quot;attached nested cubes&quot; (4 cubes) and a free floating one like this, but with 5 cubes instead of 3 :D I'll be sure to add them to this Instructable!
@Xyver; tweeted! Love the arcane vocabulary (is not a miller) Cheers! : ) Site
Thanks for sharing a very detailed and well presented instructable. though it's rarely done now, it certainly USED to be a very common way for a turner to show his skills. When you talk about using a &quot;manual&quot; machine you are of course only adjusting the machine manually,consider doing the same kind of thing with a &quot;Pole Lathe&quot; or &quot;Treadle Lathe&quot;, it HAS been done, but not my me.
I'm mainly talking about manual vs CNC, where we control the machine as opposed to robots controlling the machine.<br><br>I can only imagine how tiring a treadle lathe could be.....
you might be surprised how NOT tiring it can be ;-)
I made one of these when I was training. They are quite impressive and I'm still pretty proud of it :) <br>Thanks for sharing, I hope it inspires people to make one.
Nice and detailed instructable, thanks for sharing.
Glad you liked it :D

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Bio: I like working with all mediums, but so far my speciality is machining and electronics. I try to make all my Instructables from a "design ... More »
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