Tapping/Threading aluminum

[The_Apprentice]

I am going to practice with my cheap carbon tapping set on some aluminum roundbar soon. I the problem is I do not have any standard tapping lubricant (yet). But I do have standard cutting oil /machining coolant. Is this ok to use instead for just aluminum, or still bad idea?

 

[David S]

Not sure what size you are considering, but when machining aluminum, if I didn't have any of the specific fluids, I would use WD-40 or kerosene.

David

 

[f350ca]

As David said WD40, or if Im out straight kerosene.

Greg

 

[pdentrem]

Same as the rest! WD40 or Kerosene.

 

[The_Apprentice]

Seems I have another problem here on my first attempt at using dies.

As I understand, if I am making my own M8 nut, I need to drill about %20 smaller than the tap size. However, I am confused when it comes to using the M8 die to thread an M8 bolt. Should I start with an 8mm roundbar and just thread, or am I supposed to change the size of the shank. I ask this, because it seems damn impossible to get the M8 die on an 8mm roundbar.

 

[Dave Paine]

It is not easy to get a die to start on the bar unless you file or machine a taper. This may mean tapping the thread longer than needed and machining off the excess. I make a taper for aluminium or steel. If I do not make the taper, the die tries to bite but then the small thread breaks off before the die is able to get a good hold.

The taper ideally begins about the base diameter. The length of the taper in my work depends on the material and diameter.

 

[T Bredehoft]

Even in aluminum, I chase threads to about 70% of depth then run a die on them. The die always starts straight.

 

[brino]

it seems damn impossible to get the M8 die on an 8mm roundbar.

......and since this is the "beginners forum" one side of the die starts much better than the other!
-brino

 

[benmychree]

Tap Magic works fine on aluminum and does not stink like kerosene.

 

[mikey]

However, I am confused when it comes to using the M8 die to thread an M8 bolt. Should I start with an 8mm roundbar and just thread, or am I supposed to change the size of the shank. I ask this, because it seems damn impossible to get the M8 die on an 8mm roundbar.

8mm = 0.3149". You want to turn the blank down to about 0.310" OD, put a 30 degree taper on the end and you'll have about a class 2 fit.