Trouble Tapping/Threading My Own Aluminum Lugs

finkdigital

Junior Member
Hi all, I'm new to the forum but have done quite a bit of research on here in the past couple weeks and haven't found anything at all on topic. I'm sure a bunch of you guys have tried making your own lugs so maybe someone can help. I'm making my own lugs, mainly because I'm enjoying learning how to work on a lathe and because I want a design I can call my own.

It's not necessarily a novel functional idea... just slightly different looking. I'm using 3/8" aluminum round dowels and making a variation on a tube lug. Creating a pattern in the middle of the dowel is easy enough on the lathe... where I'm having trouble is tapping/internal threading of the dowel. If you think of it like a tube lug, that's what I have to do... get a 12-24 thread on the top and bottom of the dowel. I've had no problem getting a straight pilot hole using the lathe, but when I used a 12-24 tap, I couldn't get it to tap properly and the tension rod wouldn't screw in more than a few turns before getting blocked.

Anyone have any advice on this? What kind of tap to use? Power tapping vs. hand tapping? Fluid? % of thread depth? Anything would help. Thanks!
 
There's a user on here that's a custom drum maker and he's made a few drums for me. His name is Crazy 8's, although I think his internet has been down lately. You could also hit up a user named Gwaco, he's pretty busy though so I don't know if he'll be able to get back to you.

Hope that helps. Welcome to Drummerworld.
 
What you are expierencing is called gauling and is common with aluminum.The steel tension rod is binding against the aluminum.Try using the next size larger drill.It will give you less thread persentage,but should relieve some of the binding.I would strongly suggest using brass or stainless steel rod,unless you are using 4140 or a very hi grade aluminum alloy.Ludwig tried using aluminum on the early Acrolite snare drum lugs with zero success.Try using "Tap Ease" or a lubricant used for tapping only.
Use a hand tap method and use a starter and a bottoming or finishing tap and back off after every couple of full turns.The starter tap will have 2 flutes and the bottoming tap should have 3-4 flutes.Keep well lubed and you should be good to go and......take your time.

Steve B
 
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Hey thanks alot fellas! So Tama, you're saying that the prob is not that the initial tapped hole was bad but that bc the thread % is fairly tight, that the tension rod bonds to the aluminum thread? I wish I could use steel but its too heavy for this design. Im using 6061 which apparently many lug makers have had success with...
 
Sorry I,so haven't used 6061,so i really can't comment on its workability.Like I said,try backing off just a little on your thread % and get some Mothers aluminum polish,and try lapping the threads.That may just do the trick.You may have to experiment,because if the threads are too lose,you'll have tuning problems.Take your time,good luck.

Steve B
 
Ok I found the easiest, and it seems, best method. After tons of research and talking to some of the guys at the local community metal shop (some very experienced and one a metallurgist), I decided to go with cold forming the female threads inside the rod. I got the cold form taps on ebay for $3 and it went super smooth. Using regular cutting taps (high quality plug tap) hand tapping with good aluminum tapping fluid, it took several in/out runs at it to get full threading because you have to back it out to remove the chips. Even still, the threads were not completely accurate and you could feel the rough threads when screwing the t-rod in. With the cold form tap, it was one smooth motion (hand tapping with the rods in a precision lathe using a collet) with no chips and the t-rods screwed in with fluid motion. My research showed that the cold-form threads are overall stronger than cut threads and the metallurgist I spoke to said the he prefers cold for tapping for precision aluminum parts too.

Moral of my story is, if you're going to thread-tap aluminum lugs or anything that requires 12-24 threads, use a cold form tap for the easiest experience and strongest/smoothest threads.

Thanks for all of your help!
 
Hey! Im doing the same thing..well tapping aluminum that is. Would you be so kind as to tell me what the specs on that tap was. I tried going to ebay but there are so many i want to make sure i get the right one and dont waste my money! Thanks so much! How are the lugs coming out? Hope all is well and thanks again!
 
Hey! Im doing the same thing..well tapping aluminum that is. Would you be so kind as to tell me what the specs on that tap was. I tried going to ebay but there are so many i want to make sure i get the right one and dont waste my money! Thanks so much! How are the lugs coming out? Hope all is well and thanks again!


Yes. Don't save money on the taps. It only takes one broken tap in an almost finished job to ruin the whole thing.

You can use a tap extractor but they are hardly foolproof and also cost. So, buy "name" brand taps as they will give a better thread and last longer. Starrett are a good pro brand.

Use lots of lube and as stated earlier, back of the tap every half turn, that is turn the wrench counter clockwise until you feel the swarf "ease" in the thread.

I would also be wary of using anything but high grade alloy as it will be very easy to strip the threads on a soft alloy lug with the steel bolts. Also you can get a chemical reaction between the steel and aluminium that can almost cold weld the two together.
 
Hey thanks alot fellas! So Tama, you're saying that the prob is not that the initial tapped hole was bad but that bc the thread % is fairly tight, that the tension rod bonds to the aluminum thread? I wish I could use steel but its too heavy for this design. Im using 6061 which apparently many lug makers have had success with...

What about creating a pilot and then inserting a Heli-coil for the threading? The heli-coil will insert steel threads into your aluminum tube lug.
 
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