Basic Lathe Ops with Special '79 Fab & Barnstorm Cycles


Making a functional and bulletproof motorcycle part out of a raw chunk of metal on a lathe is a rewarding experience for the self-sufficient motorcyclist with such a machine at his disposal. In this installment of Metal Shop, Jay from Special '79 Fabrication uses a taillight project to illustrate some simple but effective machining methods. Jay took inspiration for this taillight construction from Gabe at Afterhours Choppers 


The above video is just a quick look at part of the process, for full details, keep reading...

From Jay: Ok people, this is some raw step by step instructions on how I go about spinning up a piece of solid aluminum into a nice small taillight shell to house a 1” mini led cluster. I’ll be touching on basic lathe operation, pretty much what you’d need to know in making such a light if you have access to a decent lathe.



First, I like to cut a chunk off the solid 1 ½” aluminum solid round that allows me to clamp at least 2” in the lathe chuck.  I like to make sure I have at least 4” of the solid aluminum bar to start the project.  I’ve found that I need to have about 1 ½”-1 ¾” for a finished length, accounting for all the light guts and threaded mounting section of the shell.



There are so many cutting feeds/speeds to remember when working on a lathe that it’s best to have a printed reference or a copy of “The Machinery Handbook” for anything you’d ever need to know about the subject.  I’ll only be speaking about the ones being used in the aluminum work being done.  With that being said, aluminum like a nice fast turning speed (1200 rpm) to get a smooth finished surface.  I use straight wd40 as a cutting fluid for aluminum with very nice results.  







There are many cutting tools used in lathe work, I’ll be using a basic diamond shape carbide bit in a left handed bit holder for facing and tuning down the aluminum to the needed diameter. Depending on the particular cutting tool set up or workpiece material you will be using, placement of the tool's cutting edge on the workpiece will vary a bit. The basic rule of thumb is between 9 o'clock and 3/64ths above 9 o'clock. The cutting tool itself should be set up with about 3-10 degrees of side rake and side clearance from the workpiece  I used some machinist blue to scribe a center mark in the face and down the length of the piece so this could easily be seen.







The lathe carriage face has the longitudinal carriage adjust, the bottom dial on the cross feed is the cross feed compound adjust, and the top  dial on the cross feed is used in angled cross feed adjust. The first process I do is called facing the piece.  This ensures that the face is perfectly machined surface before I start any other process.  Using the longitudinal carriage dial, I bring the cutting tool to the 9 o’clock position barely off the face of the piece.  Turn on the lathe, make sure it’s at the correct turning speed and direction for facing your material. Use the carriage dial and compound adjust dial to set the bit onto the outer edge of the face of the aluminum. Start with cutting minimal amounts of metal off the face, traveling in towards the center of the piece’s face using only the compound adjust dial.  Back off the piece and travel back to your starting point and repeat until you have a nice even, faced end piece.










Next is drilling a center hole in the aluminum.  Use a centering bit in the drill chuck being used in the lathe’s tailstock.  I slide the tailstock up to the piece I’m drilling so the centering bit is about ¼” off the aluminum.  Lock the tailstock with the locking arm and use the dial adjust at the back of the tailstock, bringing the bit into contact with the aluminum and drill the centering hole.  I change out the centering bit with a 3/8” drill bit to drill to the depth needed.  Back the bit out often to re-lubricate and brush metal chips off the bit.  I’ll repeat with the size drill bit needed to tap a ½” 13 tpi hole.  When done, it’s time to talk about power tapping in a lathe.

Next is drilling a center hole in the aluminum.  Use a centering bit in the drill chuck being used in the lathe’s tailstock.  I slide the tailstock up to the piece I’m drilling so the centering bit is about ¼” off the aluminum.  Lock the tailstock with the locking arm and use the dial adjust at the back of the tailstock, bringing the bit into contact with the aluminum and drill the centering hole.  I change out the centering bit with a 3/8” drill bit to drill to the depth needed.  Back the bit out often to re-lubricate and brush metal chips off the bit.  I’ll repeat with the size drill bit needed to tap a ½” 13 tpi hole.  When done, it’s time to talk about power tapping in a lathe.







Tapping in a lathe is fun, but you can screw up easy if you’re not paying close attention.  I make sure the lathe speed is turned down as slow as it will go for tapping any holes.  Make sure your drilled hole is chamfered so the tap will start threading easily.  Tighten the tap in the tailstock chuck and lubricate with tapping/cutting fluid.  Turn the lathe on and make sure it’s rotating counter clockwise, slide the tailstock so the tap goes into the drilled body hole.  DO NOT LOCK DOWN THE TAILSTOCK, you want it to slide freely while tapping.  I like to turn the lathe on and off while tapping, only threading a little at a time.  Reverse the lathe rotation from time to time to break free any metal chips.   Back the tap out of the work piece and check your new threads.  










Next, I’ll turn the sides (diameter) of the aluminum down to size with the same cutting bit in the tool post.  This will give me a nice surface to layout the design/shape of the shell.  On this piece, I’ll be freestyling it and just spinning the shape by eye with a rounded cutting bit for the details.

Now, you can either cut the piece off in the lathe using a cut off bit/tool or remove the piece from the lathe and cut to a rough finished length with a bandsaw or something similar.  Chuck the piece in lathe the opposite way in which you’ve been machining to get ready for boring a hole to fit the led cluster. 


I usually drill the hole for the cluster close to finished size and then use a boring bar to fine tune.  The aluminum is so easy to machine, I’ll just jump to the boring bar and directly bore to size.  Change to the boring bar (and lathe speed back to 1200 rpm) and make sure the boring bar is set parallel with the hole drilled in the work piece.  I like to work backwards, from the interior/bottom depth of the hole, to the outside of the face of the piece.  I measure often and continue to bore until I reach my finished dimension for the led cluster.

























Once you get a good fit, measure the thickness of the stack of lower o-ring/led cluster/upper o-ring/lexan lens/stainless mesh so you can determine where to cut the interior groove to put the internal snap ring in to hold the mess together.  Mark with sharpie, chuck it up in the lathe and use the boring bar or similar cutting tool to cut the groove. Assemble the light guts and check to see if you need any adjustments. 















After boring a  ¼” hole in a stainless ½” 13tpi cap bolt for mounting and running the wires through, this light is done.  Finish the light’s surface as you see fit, mount, wire, and go ride your chopper to glory!






You can see more of Jay's work on his blog here and on the Barnstorm Cycles site here.

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Commented on 12-28-2011 At 05:51 am

Just like his blog, another sharply photo'd project. Great stuff. thanks for sharing.

Commented on 12-28-2011 At 07:22 am

excellent! i was gonna try my hand at some breather bolts to get back into the swing of things on the lathe but this looks way more fun!

thanks for such a detailed and well photographed write up Jay!

Commented on 12-28-2011 At 09:07 am

Excellent write up

Commented on 12-28-2011 At 09:25 am

great tech stuff...keep it coming, lets see some mill work next.

Commented on 12-28-2011 At 09:34 am

I just got a 1932 South Bend lathe - I hope I can turn out stuff half as good as this!

Commented on 12-28-2011 At 11:15 am

Very nice, great detail shots. Thank you.

Commented on 12-28-2011 At 11:23 am

looks good nice and bright with that new bulb too

Commented on 12-28-2011 At 11:44 am

Lathework is fun & relaxing when you can find the time to play around. There's an another video of the entire taillight lathe process on the SPCL'79 blog right now.

Commented on 12-28-2011 At 12:23 pm

This is bitchin. I bought a small lathe from a co-worker just before the Twine Ball Run and really had no idea what I was going to do with it. I'm a little inspired to say the least.

Commented on 12-28-2011 At 12:44 pm

Just started messing with a lathe, so many ideas. This helps alot. Thank You

Commented on 12-28-2011 At 03:07 pm

dude, really, you couldn't do this with a grinder and file............

Commented on 12-28-2011 At 07:09 pm

This is a great article well done. To get a cleaner hole with the boring bar, make several passes with the boring bar with the last pass taking off very little, then with spindle in reverse use some scotch brite to really smooth the bore up.
Hey Roland, I'm no no-it-all but wanted to answer your question if I could. When taping you want to keep your left hand on the forward/stop/reverse knob. Make a mark on the shaft of the taps shaft at the desired depth of thread (use liberal amounts of oil on the tap) you want to cut. When the mark gets close to part your taping turn the knob to stop (Depending on your lathe it will either coast to desired mark or you can bump the knob from stop to reverse. Remember you are taping with spindle on slowest speed.) Now turn the spindle knob to forward and it will back the tap back out. Aluminum will smell like sulfer when taping but you can tap the whole way without stopping when using larger taps. It helps to have your drilled hole slightly deeper than you want threads to go.
Taping steel you need to cut some then back tap out to remove chips, then tap a little deeper and back out each time until you reach the mark on tap shaft.

Commented on 12-28-2011 At 07:49 pm

Thanks Wooley. Im going to try that when i get a chance.

Commented on 12-28-2011 At 08:45 pm

Perfect stuff for chop cult. A lot of time goes into a project like this and more when you take the photos and write it up. Thanks

Commented on 12-29-2011 At 02:35 am

So stoked over this write up. Just scored a smithy lathe, perfect timing.

Commented on 12-29-2011 At 04:52 am

Roland, for anything smaller than 5/16" 18, I'll use the tailstock to line up the tap and start the threads, finishing the full thread by hand.

Commented on 12-29-2011 At 10:51 am

Jay, I see you are giving all our secrets away again! If you keep on making machining work look like fun there will be all kinds of garage machine shops popping up, just like the all the new Chopper Shops after Jesse James showed everyone how to hammer their own tank. All kidding aside nice job on the write up. Did you ever think about being an industrial arts teacher if the Bike, Art thing does not work out? Tim

Commented on 12-29-2011 At 01:36 pm

***Good job Jay. You are my hero***
It takes practice, kids, to get good finishes and be consistently accurate with your dimensions. And you will need to learn lathe tool cutting clearances before you even touch a lathe. Be careful as with all machinery and have fun.
For those that asked about power tapping, I've power-tapped down to 8-32 in aluminum but I've been doing this a while. Get yourself a spring center and a tap handle and tap holes manually before you get too wild. Last thing you want is a broken tap in a part you have 6 hours in.

Commented on 12-29-2011 At 01:41 pm

gota get one!

Commented on 12-29-2011 At 05:24 pm

great write up. thanks.

Commented on 12-29-2011 At 07:26 pm

Great tech write up! Always nice to read these and get new ideas.
Thanx much...

Commented on 12-29-2011 At 08:26 pm

Awesome!! Great products and a fantastic tutorial.

Commented on 1-4-2012 At 03:30 am

Ahhh yeah this is good shit. I'm about to buy a mill lathe combo and goin to try to make All kinds of stuff. Thanks, be cool!

Commented on 1-19-2012 At 03:09 pm

ya i would like to see some more.

Commented on 2-7-2012 At 07:01 pm

I am new to this site and this was the first tech tip I came across. I really enjoyed it and am looking forward to starting the project.
I did some quick I-net searching for the LED cluster but did not feel comfortable with what I found. Can you let me know who you get you LED's from.
Thanks for the great tip, looking forward to seeing more.

Commented on 2-15-2012 At 04:26 pm

I'm in the same boat as G4, does anyone know where he got that LED cluster? I'm making my own rendition of this for my bike and i can't continue till i find them

Commented on 5-2-2012 At 02:21 am

just made one ,thanks jay for the vid , total cost 25bucks (i have a lathe ) led was 13$ got some stock at scrap yard for 12$ ! took me about 2h's

Commented on 5-2-2012 At 02:24 am

led clusters are aviailable from parts unlimited and custom chrome got mine thru local shop 1" brake &light

Commented on 5-17-2012 At 12:59 pm

Just finished a couple of lights for my self using the same technique as described above, one similar to the one in the video and one a little larger similar to the Afterhours Choppers product . Even designed a couple of lights to fit into a filler between the bags and fender on a Road King.

In all cased I used LED Clusters form They have many different sizes and light options to choose from. Quick shipping, no hassles.

Commented on 2-25-2014 At 10:24 pm

I'm surprised the dude from after hours is pissed because they used a clip ring to hold the screen in... He invented that idea....

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