[How-To] Tapping Aluminum (M3x0.5)

[MyLilMule]

I am working on a bracket to hold the DRO reader head for my mill. I need to tap these two holes M3 x 0.5. I don't have metric drills, so I used a #40 drill (closest I had) but my taps I have are just junk.

I need to find a decent and appropriate M3x0.5 tap and a tap handle that will actually hold it. Any recommendations and any tips you can give to help me along the way?

This is my first time machining aluminum. TIA.

 

[WobblyHand]

I am working on a bracket to hold the DRO reader head for my mill. I need to tap these two holes M3 x 0.5. I don't have metric drills, so I used a #40 drill (closest I had) but my taps I have are just junk.

I need to find a decent and appropriate M3x0.5 tap and a tap handle that will actually hold it. Any recommendations and any tips you can give to help me along the way?

This is my first time machining aluminum. TIA.

View attachment 402424

Since you seem to buy from McMaster, you can get a decent M3 tap for less than $9. I'd buy a tap handle elsewhere. I'd use a small Starrett 93A. I have never had them slip. I'm sure there are other decent tap handles, but I don't know of them.

Another piece of advice is to use a tap follower in your mill.

Line up the mill to the hole. Install tap follower and install spring loaded point into the dimple in the Starrett. Your tap will now be centered in the hole. Use WD40 for a tapping fluid. Turn some, reverse the motion to break the chip, repeat until done. Lower the mill head to keep spring pressure on the tap holder. If the tap seems to get tighter, it's time to back off to break the chip. These little taps are easy to break, especially in aluminum, and doubly especially if you don't use the tap guide. Hope this helps.

 

[MyLilMule]

I buy from McMaster when I need to buy from McMaster. They're about a 45 minute drive for me, not likely to make that trip for a $9 tap. I do have a couple shop supply stores here in town. I'll see what they have.

I guess part of my question was (in my head, anyway, since I didn't type it out) is there a type of tap that is better for aluminum? I see all kinds of taps, and quite frankly, I don't know what I should be looking for.

 

[WobblyHand]

There are taps that are better for aluminum, but the question for you is, how many holes are you doing? If just two, get a general purpose HSS tap. The tap really doesn't need to be coated, either. I've done lots of M2.5, M3, M4 & M5 holes with general purpose HSS taps in aluminum. Only tap I have ever broken was a 6-32 in aluminum and it was free hand. Don't do that. Use a tap follower, tap lube and a gentle touch.

I don't live close to McMaster, so I have to have their orders mailed. So I tend to wait a while between orders to make it worth the postage. Having a McMaster store being only 45 minutes away would be great.

 

[mmcmdl]

For aluminum and only 2 holes , no need for a special taps .

WH and I typing at the same time .

 

[WobblyHand]

@mmcmdl I still remember that stupid 6-32 tap breaking. That little crack, more of a tink. It always seems to happen in a piece that you were so happy that it came out well. Still haven't been able to extract the 3 flute tap. It's somewhere here, couldn't bear to toss it out. Oh well, learned my lesson.

 

[maspann]

I have had a lot of luck with Hertel taps from MSC. Great quality and reasonably priced.

 

[mmcmdl]

@mmcmdl I still remember that stupid 6-32 tap breaking. That little crack, more of a tink. It always seems to happen in a piece that you were so happy that it came out well. Still haven't been able to extract the 3 flute tap. It's somewhere here, couldn't bear to toss it out. Oh well, learned my lesson.

I haven't really broken many taps over the years most likely because I had access to the best taps available . Where I am now , I re-tap hardened dies once I machine out the broken bolts etc . Doesn't matter what taps are used , they break . I cut them out with carbide end-mills , ream to .249 , press .251 stainless tubing in and drill and tap to size . Now when they break the bolts , I just press the inserts out and re-install new ones . The dies never see the actual machine shop any more as I do it in the maintenance shop nightly . Big savings for the company .

I have sets of taps down below in the for trade/sale section Mule . Nothing special about them but they are cheap .

 

[woodchucker]

Even a HF set of taps HSS will do it. Aluminum is a piece of cake, just use WD40 or TapMagic for AL.
I have a set of HF Taps because of the Metric taps and dies. They have worked well. I also have all USA made taps that I use for my daily tapping. The HF kit has filled in on stuff I rarely need and don't have.

Also, make sure you countersink to start the hole/tap

 

[MrWhoopee]

Tap followers work well with taps large enough to allow it. I like a piloted spindle tapper myself.

Piloted Spindle Tap Wrenches - - Pilots Spindle Tap Wrench Set

www.msdiscounttool.com

@Charles scozzari posted a neat idea that I like so much I ran out and made one.

Direct tap handle mount

Good morning, This is a manually operated tap handle that mounts directly to the chuck after you lock smaller taps in your mill or drill. One handle is stationary while the other slips threw the ring and into one of the chuck key holes and is locked in place so as to not launch when spinning the...

www.hobby-machinist.com

Use WD40 or kerosene in aluminum.