cutting threads in aluminum?

is there a secret to tapping threads in aluminum? maybe some special sauce? in the past i've had problems with the tap or die galling and wiping or pulling out the threads as i cut them in aluminum. i don't know which brand of cutting oil i'm using, but i always make sure to use plenty of it.
i asked a trucker friend of mine who visits plenty of machine shops and was told to try this magical solution one guy mixed up. it seems to be made up of graphite and deisel fuel. i don't want to mess up this piece and have to use a helicoil or start over.

 

I use Cool Tool cutting oil. I also make sure the tap is new, or at least very sharp. A dull Tap will screw you up all the time. Also if it is a blind hole, make sure you back it out and clear the chips several times. Good luck.

 

http://www.tapmagic.com/TMaluminum.htm

cc

 

i have a real old can of tapmagic, but i didn't know they made a solution specifically for aluminum and other soft metals. i have a new tap and die set. maybe part of the problem i had in the past was using my old man's set.

 

I have always just used regular cutting oil but as dugbred stated I take my time and only cut a few threads at a time before I back the tap up and go back at it. If it is a deep hole I will even take the tap right out and flush out the chips a couple of times. I'm no machinest but it has always worked for me.

 

I back up just enough to break the chip every half turn, just to be safe.

 

methylated spirit

works also great when cutting thick aluminium with a electrick saw.

 

Sounds like a dull tap. Soft metals require a nice sharp tool.

Flatman

 

Ya I go half a turn then back a quarter turn

 

That works for me, too. I've tapped threads into LOTS of aluminum parts that way with no problems (and I just used WD-40 for lube!!)

 

a drop is dish deturgent on the tap helps sometimes?

 

I hand tap aluminum.With lots of cutting oil

 

Any kind of oil, aluminum is really forgiving, are you going straight in or backing up a 1/2 a turn every couple fo turns

 

Hi Rick,

Like said above, make sure your tool is good and sharp. Ask some else if you're not sure if a tap is sharp. For aluminum, your cutting tools need to be really keen.

The cutting fluid I use on aluminum is WD-40. I'm not joking, the stuff works great. Also, be careful if you are backing the tap out a lot. If you apply any side loading when removing the tap over and over, you'll end up with a tapped hole that's "lose" or over sized. An over sized hole will not have very much holding strength.

Take care,

David

 

If possible, use a tap guide, or chuck it up in a drill press(NOT under power!)and turn the chuck manually; this will keep it straight.

 

In aluminum use a shinny tap not a black one the black seem to stick more often and make sure its sharp and just about any oil or cutting lube will work. I ran and programmed CNC machines for about 8 years . In a cnc machine you can tap with a ¼-20 @ 1000 rpm when you ridged tap witch meant no type of taping head just tap collet and the machine. Good luck man.

 

Another great tip! I made a cheap and easy tap guide after seeing one in STREET RODDER years ago (Tom Vogel made that a very technically usefull mag back in the day!)...using a drill press (with lotsa patience and WD-40!), I just drilled different sized holes in a piece of thick aluminum stock. Works like a charm!!

 

Depends on what thread pitch your cutting, and always use lube...tap magic...Make sure your taps/ dies are sharp, depends a lot on what temper alloy your threading also. I have seen a lot of people cutting a 5/40 pitch on T6 and burn the threads even thou the back cut ever quarter turn aluminum is bad about building up on the cutting face. What I do is cut a 2-3 turn ** based on pitch cut & alloy/ temper** at a time back all the way off blow out the cutter and material, and start over tell i get the depth or length I need.

 

I hate to ask this, but are your taps good American high speed steel or cheap made in India high carbon steel? I worked in an aircraft machine shop for 33 years and tapped lots of aluminum. I liked gun taps best for through holes. Don't usually need to back them up as they push the chip ahead of them. I have used both black and shiny taps. Both work fine if they are good sharp taps. I like Bo-Lube best as a tapping compound.

 

I power tap aluminum tubing in the lathe all the time to make radius rods. I like sharp two flute taps with plenty of cutting fluid (just the plain old mix with water milk looking stuff).
Eric

 

If you're designing something out of aluminum that needs to be tapped for threads, use coarse threads whenever possible. Softer metals like aluminum do better with coarse threads than they do with fine threads. Also, drill the hole all the way through the part if possible, or at least drill it a lot deeper than the threads need to go. Some taps tend to shove the shavings forward, and if your hole is too shallow, the shavings wind up wadded down in the bottom of the hole. Before going all the way down with the tap, back it out and blow the shavings out of the hole with an air hose, and blow the tap clean, and put clean cutting oil before you start tapping again. Keep the tap perfectly perpendicular and turn very lightly until you're sure the tap is following the previous threads.

Sometimes it helps to get the tap started more easily if you drill a slight countersunk hole leading down to where you want to tap it. Like if you want to tap a 1/4-20 hole in aluminum, drill a #7 hole first, then countersink it about 1/8" deep with a 1/4" bit. Doing that also keeps the top surface flush once you've tapped it (rather than having the top thread pucker out from the surface a little).

I like using tap-magic for all my tapping in steel or aluminum. I used to use cutting oil, but the tap-magic seems to cut down on friction more and my taps last longer with the tap-magic. It wicks down into the hole better and it's easier to clean the oil back out of the hole because it's less viscous. A little 4 oz can of the stuff lasts a really long time if all you use it for is tapping.

 

They also have a special Tap-Magic for aluminum.

 

+1 on the Boelube. If its good enough for Boeing its fine for me.
Push-up tube like stick deodorant,teeth on then tap will grab and
hold it, then the heat from cutting will melt it right were you need
it. Makes my sawzall blades last a lot longer too.

 

One other thing...I usually put a slight chamfer on the outside edge of the tapped hole. It's a little thing, but it looks nice and seesm to work good, too.

 

I learned using the drill press method as well. Apparently I was a little shakey in my youth...

If I were you I'd have Jeremy do it. He'll do it better than you anyways... just ask him.

 

In my shop we use plain old Pale oil (light mineral based cutting oil) diluted about 30% with solvent. An old timer once showed me the solvent trick, and it really helps when doing anything with aluminum. In 48 years of running screw machines I've never had great luck with sulpher based cutting oils on aluminum. For diameters 3/8" and over spiral fluted taps are available. They work great on aluminum. They really pull the chips out of the hole, great for blind holes.

 

Something I do use a lot on aluminum that didnt hit me tell now is heli-coils.

 

All I ever use on aluminum is WD-40. Works great, and like David says keep it straight. Use both hands and it will help you from rocking the tap...
Jeff

 

Chamfer, tap magic for aluminum, sharp tap, blind hole..high helix tap (pulls the chips out as you tap. Thread forming taps are the way to go in aluminum IMHO. Just make sure you use the recommended drill size. Probably have tapped more holes than one guy should be allowed .
Fitysix

 

Everything Rich said except I've never used Bo-Lube. Handtaps suck, use a GOOD quality spiral point gun tap. Also, do not use the OLD regular version of Tap Magic on aluminum, it will get hot and smoke and weld your tap in the hole, it must be the aluminum flavor.. Been there, done that. Also the old version contains 1,1,1 tri-chlorathane, which eats your liver.