TIW Aluminum Pen

In this Instructable you will learn how to make an aluminum pen on the lathes at Texas Inventionworks at UT Austin. All the materials and tools you will need can be found in TIW so you don't have to buy any supplies yourself. Make sure to be safe with all of the equipment, follow all necessary safety measures, and feel free to ask Joe or anyone else in the shop anything if you have any questions. It is assumed you have completed the lathe training so basic lathe operations will not be explained in detail.

Supplies

Let's start by getting familiar with all the tools we'll be using. You can find any drill bits either in the box on the table right in front of the lathe or in the metal cabinet right outside the machine shop. The chuck and the chuck key (2nd pic) can be found in the 2nd drawer of the tool desk to the right of the lathe. You can find the taps and dies(4th and 5th pic) in a blue box on top of the large wooden cabinet(4th pic). There are calipers on the tool desk next to the lathes. Finally, you can find the Allen keys on the tool desks by the mills.

For the ink cartridge I will be using a Pilot G2 .7 cartridge and spring but you can use whichever pen components you want and adjust the dimensions of the inside diameter and length of the pen accordingly.

Step 1: Part Drawings

Let's start with the drawing of our part. We'll first start by making our cap, then the body of the pen, and then the tip last. Refer to this drawing for all dimensions. All dimensions are in inches.

Step 2: Setting Up the Lathe

First get your piece of Aluminum stock from the yellow bucket by the table in front of the lathe. Get a piece of stock that's closest to a 1/2" diameter. Clamp the stock down in the lathe leaving at least 1.25 inches of stock sticking out. Place your turning tool inside the tool post and make sure to lock it by rotating the lever towards you. Check your speeds to make sure that you are cutting at a reasonable RPM. For turning and facing, 460 or 755 is reasonable for Aluminum. Now you should be ready to begin taking off material from your part.

Step 3: Turning the OD of the Cap

Begin by zeroing your X and Y axes on the face and the outside diameter of your part. We will be using these zeros to get close to the dimensions of the pen. Measure the outside diameter of the stock, then subtract your desired diameter from that number (which in this case is .48") to get a goal number for the DRO. Now you can start taking 20 thou passes with a shoulder length of .75" until you reach that goal number for the outside diameter of the part. Once you are within 20 thou from your goal number, take a measurement of the diameter of the part and adjust your final pass depth so that your final diameter is as close to .48" as you can get it.

Step 4: Drilling the ID of the Cap

Now that we have the outside diameter of the cap finished, we can start working on the inside diameter of the cap. For this, grab a 5/16" drill bit from the box of drills on the table in front of the lathe and a center drill, which you can find on the top of the tool desk next to the lathe. Since we will be drilling, turn the speed of the lathe down to190. Insert the chuck into the tailstock by lining up the taper with mating taper inside the tailstock. If you can't find the mating taper, that means you have to lengthen the tailstock by rotating the wheel until the mating taper appears. Put the center drill inside the chuck and tighten it down with the chuck key. Using the center drill, begin drilling into your part until the center drill is about .1" deep. After that, switch out the center drill for the 5/16" drill bit. Move the tailstock until the drill is roughly flush with your part(like in the first picture) and lock the tailstock down. If you're finding it difficult to slightly move the tailstock, I like to use my fist and lightly tap it to move it a little amount. Adjust the dial on the tailstock to be zeroed at that position. Now using the indicator on the tailstock, you can start drilling into your part to a depth of .35". Each big dash on the indicator is equivalent to 10 thou so in order to cut to a depth of .35", you need to make 3.5 rotations of the tailstock. You will end on the .5 marker as shown in the last picture. You can now remove the drill from your part.

Step 5: Tapping the Cap

To finish off the cap, we just have to tap threads for the body to screw onto. To do this, you will not have to turn on the lathe for any of these steps. Start by finding the tap follower (3rd pic) in the drawer in front of Joe's desk above the drawer that says edge finder. You can also find the tap holders inside the metal cabinet by Joe's desk(1st picture). From the tap box, get the 3/8-16 tap. Put the tap into the correct size tap holder and tighten the fastener to secure the tap in place. Now go ahead and put the tap follower inside the tailstock chuck on the lathe and line up the tap between the drilled hole and the tap follower as shown in the fifth picture. For tapping, since you aren't using the lathe, I like to lift up the safety screen to make sure the lathe doesn't turn on accidentally. To start tapping, apply some cutting oil on the tap and the part and wind the tailstock out so that you preload the spring in the tap follower. You can now start rotating the tap away from you to begin cutting the threads. With the tap, you want to ensure that you are breaking up any chips that build up, so for every 1 full turn you make, unscrew it by half a turn to break the chips and then continue onto your next turn. Keep on repeating this until you feel the tap has reach the end of your part and has a lot of resistance. You can now full unscrew the tap and your part should now have threads. Feel free to check out this video in order to get a walk through of how to tap: https://youtu.be/769r9jE4Phs?si=Kiz9ggUnppbFjKkX.

Step 6: Parting the Cap

Now that you are done tapping, grab the parting tool and put it in the tool post. Make sure that the tool post is perfectly perpendicular to the chuck before you start cutting. Zero the turning tool on the front face of your part, measure the thickness of the parting tool, then re-zero at that number you just measured so the back face of your parting tool is flush with the face of your part. Now go to a length of .5" from your zero and begin parting. Make sure to go slow and apply pressure based on the feedback the lathe is giving you. Once your cap is parted, you can put it back inside the lathe chuck backwards to re-face the little nib that was left from parting. Your cap is now done.

Step 7: Starting the Body

Start with another piece of stock that is close to .5" diameter and at least 3.5" long. Begin by putting your stock in the lathe with at least 3.5" sticking out and zeroing your turning tool on your stock. Also ensure your speed is increased for turning. Then begin machining the diameter down to .48" with a length of 3.2". Once you have that down, using the parting tool, part off your part to a length of 3.025" using the same procedure we used for parting the cap.

Step 8: Creating the Shoulders of the Body

After you have parted off the stock, put the stock back into the lathe, re-zero your turning tool on your stock, and turn down a shoulder diameter of .37" with a length of .35". Repeat on the other side of the body. When you're done machining the shoulders, we'll need to add relief cuts for the threads. You can do this by getting your parting tool and lining it up with the shoulder and creating a groove at that point. For this operation, don't part through the entire stock, only part to a diameter of .3". Repeat this for the other side of the pen too. Refer to the drawing for what the grooves will look like.

Step 9: Creating the Threads of the Body

Once the shoulders of the body are created, you can use a die to create threads on them. You can grab a 3/8-16 die and a die holder from the blue box that we got the taps from. The die has a set screw that you can use to tighten the die. Make sure the side of the die where the cutting grooves are slightly chamfer is the side that you put up. Grab the knurling tool or any of the other large tools with a flat face and put it into the tool post. Line up the die and the tool post so the die is concentric with your part and is flat against the tool post(as shown in pic 2). Using the die is similar to using the tap - use cutting oil, rotate the die away from you and for every 1 full turn, back the die out by half a turn to break up chips. As you rotate the die, also move the tool post in the y axis so that you're applying pressuring on the die to keep it straight. Keep going until the die runs into the shoulder and you can't rotate it anymore. Once you have done that, back the die out and flip the orientation of the die inside the die holder so the side without the chamfered grooves is on the top. Then line up the grooves of the die with the threads on your part and repeat the process with the new die orientation. This is in order to cut the threads by the shoulder of the part since the original die orientation didn't fully cut the threads since the die was chamfered in the front. Repeat this for the other shoulder of the pen.

Step 10: Drilling the Hole for the Body

Grab a 1/4" drill bit from the box and a center drill. Drill a center hole through your part and then drill a 1/4" hole until you're at least half way through your part. Then flip your part over in the chuck and repeat the process until you have made a hole which goes through your entire part. You are now done with the body of the pen.

Step 11: Beginning the Tip

Begin by turning down a piece of stock to a diameter of .48" with a length of 1.5". We are now going to begin the angle at the end of the tip. We are going to cut an angle of 20 degrees for the tip. To do this, we first need to adjust the angle of the compound slide(the angled slider) and the angle of the tool post. We can adjust the compound slide angle using the hex heads on the plate that the compound slide is on(In the first pic by the angle marks). Once you loosen both screws on the plate, you can freely rotate the compound slide angle. Rotate the plate until the hash mark on the compound slide lines up with the hash mark at 20(as shown in the second picture). Now you can tighten the bolts to lock the plate into that position. Chances are your tool post is now also angled. To fix this, loosen the large nut at the top of the tool post using the large crescent wrench by the lathes. Now get a 1-2-3 block from the cabinet by Joe's desk(second to last picture) and line of the tool post with the chuck and the 1-2-3 block so that the tool post is parallel to the chuck(last picture). While holding the chuck against the 1-2-3 block, hand-tighten the nut, then you can set everything down and tighten the nut with the crescent wrench. You can now begin cutting the taper.

Step 12: Cutting the Taper

For this step, rather then a turning tool, we will be using the large boring bar. In order to do the taper, since the angle is cutting away from you, you need to be cutting on the side furthest from you(as shown in the 1st picture). Because of this we will need to be running the lathe in reverse. To do this, rather than moving the handle down to start the lathe, pull it up instead and this will cause the lathe to spin in the other direction. Now to start cutting the angle, we'll be using the compound slide. First, zero your tool on the outside diameter of your part(zero on the face away from you). Now, don't move the axis that moves your tool left and right from here. Start up the lathe in reverse and take a cut at the diameter you zero'ed at using only the compound slide. Take another cut by bringing the x-axis towards you by 20 thou and taking another cut. Keep on doing this and measuring the diameter of the tip until the diameter reads .2". Your outside of the tip is now done.

Step 13: Drilling the Inside of the Tip

For the final step of the pen, we will be drilling the holes. The hole dimensions are quite precise so make sure the depths are as close as you can make them. We'll start by drilling a center hole and then a through hole with the 1/8th" drill. Next, using a 1/4" drill, drill to a depth of 1.26", using the tailstock indicator to keep track of the depth. Finally drill a 5/16" hole to a depth of .88". Once you have the 5/16" hole, tap the hole with the same method we use for the cap using the 3/8-16 tap, going until the tap goes to the shoulder of the part. Your pen should now be completed!

Step 14: Assembling the Pen

To finally assembly the pen, simply thread the tip onto the body, insert the spring into the hole, and insert your ink cartridge afterwards. Final thread the cap on until your ink cartridge is revealed. In case your parts don't fit flush together, try cutting your relief grooves slightly deeper or by rethreading your parts with the tap or die. You can also add any knurling, chamfers, and polish your pen however you like. In order to retract the pen, simply unthread the cap and/or the body and it will hide the ink tip.

In order to get rid of any seams between the different parts, put the assembled pen back on the lathe and turn the diameter down til you pass the seam.