Tapping Aluminum

[DPeterson]

Thread tapping experts please help.

Spent 4 hours machining a special part out of normal 6061 aluminum bar stock. The part needed 4 holes with 4-40 threads. On my third hole I snapped the tap off. Part ruined. Happens to me all the time.

Used a 4-40 Titanium Carbonitride Hss Sprial Point along with a number 43 drill bit as called for. I took my time. I tap in slow until I feel a little resistance and then I back it out and clean the tap. On the third hole I was almost all the way through but I felt a little resistance so I began to back it out. Well it snapped. (a lot of choice words came next)

What am I doing wrong? Wrong taps? Thought I was using the right one or best one. Should I be using cutting oil? Is there a trick to this?

Thanks for any advice. Doug

[JimClark]

there is a special lubricant for tapping alum
here is what I uesd when I used to make aluminum sailboat masts

6200128-11.jpg

[kendt]

Its been a while since my metal shop days. But I can offer a couple suggestions. I think lube is a must. Even though aluminum is relatively soft there is still a lot of friction and that is likely whats causing the breakage. Especially when you get the tap all the way in. Also if you don't get it started perfectly straight its going to break for sure. My personal way of starting is on a drill press that you know has been squared up. On smaller taps put turn the spindle by hand while putting just enough pressure on the down crank to help feed it in.Just far enough to get a good staright start then loosen the chuck and finish the normal way. If its a larger tap I start the drill press and when its spinning at speed shut it off and feed the tap in until it stops turning then loosen the chuck. And always lots of lube.

[blizard05]

WD 40 does a good job

[Basstronics]

Tap magic for Aluminum.

Period. Problem solved. Threads come out looking like chrome.

Under $10 for a little bottle that will last a hobbyist a lifetime.

http://www.ebay.com/itm/TAP-MAGIC-Aluminum-Tapping-Drilling-Milling-4-oz-20004A-Cutting-Fluid-/310678134160?pt=LH_DefaultDomain_0&hash=item4855dc1d90

Also I think you are using the wrong taps. Those are good for CNC but not so good for hand tapping. just a good #4-40 plug tap should do the trick perfectly. I have tapped many holes in my days. For a #2-56 all the way up to 2"+ in all sorts of materials. For aluminum there is no better than tap magic- period.

http://www.ebay.com/sch/i.html?_odkw=%234-40+tap&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.X%234-40+plug+tap.TRS0&_nkw=%234-40+plug+tap&_sacat=0

[DPeterson]

Geez - Looks like I missed the boat a long time ago.

I assumed soft metals didn't really need lube. Wished I had not been so shy about asking a few years back.

I'll be buying new taps also.

Thanks guy's. Doug

[JimClark]

also are you using a tap handel?

[Peter A]

Hi Doug, make sure your taps are sharp, as in new. Blunt taps will bind and snap easy, especially small ones. You could try a slightly bigger tapping hole also if you can get away with it. Lube oil definitely, wd40 as suggested works fine.

[T.S.Davis]

Bet I know what your making. You're welcome. haha

I use plane ole 3 in One oil.

[photohoward1]

Nice soft cheese works perfectly too.

[DPeterson]

Ya - I have a nice tap handle.

Interesting how even soft aluminum will dull the taps. I even changed taps before I broke what I thought was a new one.

Terry - I guess you should have patented your idea. Too late. I actually found a good method that uses off the shelf materials with about 30 minutes of assembly that I am going to pursue. I had lots of fun milling and machining my part, but way too time consuming compared to the other. Will be putting the unit through some testing this weekend.

Howard - That gives me an idea for a book. 101 ways to use cheese - not always for eating. I'll sign the first copy for you.

Thanks again guy's for the tapping instructions. Doug

[T.S.Davis]

Just don't tell anyone what you're up to. We'll argue about it later I'm sure anyway.

I may have a contribution or 11 for your cheese book. I'm pretty creative with food.

[egneg]

Nice soft cheese works perfectly too.

I believe cheese curds would be great for this!

[PatrickM]

The softer the alloy the more likely it is to gall and bind. Wisconsin venison fat will work on all aluminum varieties....

[viper1]

Turps