Question about EGT probe install/drilling manifold

[LarryB]

Hah! We sound like a bunch of lawyers.



Soluble oil? I would think most oil is soluble in gasoline.



In all fairness I did say "light oil" which may not be entirely correct.



I think aluminum is the easiest material to tap if you use the right cutting oil (A9, green can, see pix). Without it, aluminum galls(sp?) so easy and the tap gets stuck.



"Your Honor, I would like to enter exebit A and B. "



Larry

 

[LSMITH]

My vote for the hardest material to tap that is commonly seen is 15 series stainless steel. That stuff is a bear.



Seems that I am the minority on this, but I break far fewer taps using a cordless drill regardless of the material. The key is to set the clutch torque low and maintain the same angle. Forward and reverse the drill until the threads are at the proper depth. The clutch is a very repeatable torque limiter, more sensitive than I am. Using a drill motor without a clutch is begging for trouble.



OK, another possible answer to tapping dry or wet. I have been using a Dow chemical product that works extremely well in every material and it is niether wet tapping or cutting dry. I don't have it here and can't remember the name. It is a Moly dry film lube, coat your drills and taps with it and go. It sprays on wet and drys in a minute or so. The coating will last about 30 holes (6mm tap) in cast iron and about 10 holes (6mm tap) in 15-5 stainless. Aluminum you can go forever it seems without refreshing the lube. I do not tap anything without some sort of lubrication other than plastics.

 

[illflem]

Larry, thanks for the tip on the A9, don't know how many sawzall blades I've thrown away that have been impossibly clogged with aluminum.

 

[JohnE]

I agree stainless and aluminum are both hard to tap.

The worst to drill, tap or machine is copper. It has this nasty property called work harden.



We use the Tapmatic Cream as one can apply it directly to the metal surface. A lot of our drilling and tapping is on mild steel plates behind wood or melamine. Anything applied directly to the tap is wiped by the top layer. It also works on stainless. And yes, all tapping is with power tools.



I ran W&S turret lathe many years ago. The best way to break tools was to run them dry.



What's the beauty of CNC machining? Close the hood and turn on the pump.



Use what works for you.



-John

 

[ZEEEW]

What about inconel? Never tried tapping it but sure takes awhile to cut on the cold saw.

Would a lube "too slick" cause the tap to run into cast iron too easily, and break the casting?



Eric

 

[LSMITH]

Eric the hard part about tapping inconel is getting the chips to break and get them out of the hole before you recut them. There are special taps designed to cut the super alloys that make it quite easy actually. Inconel is tough and stringy, but not particularly abrasive. Hastalloy X, waspalloy, and some others are a lot tougher to tap, but then there are always EDM machines. As far as I know there is no such thing as a tap running too free. In every case I have ever seen where a casting is cracked while tapping the tap was dull and transmitting some of the force radially into the hole rather than directing the force into the cut. The real secret to tapping anything is to get a tap to cut freely without recutting the chips. Hope this helps.