1) little bit of both
2) probably mostly cast iron or aluminum (tapping) or steel (dies) as the vast majority of stuff I do is on cars
Thanks for listing brands, because of those only Greenfield is familiar to me. Do you have any opinion on Westward (mentioned above)?
In the case of these small sizes that we're specifically discussing, I have no idea what I'd be using them on. In the most recent instance I needed the #8 UNF tap to fix a slightly munged up chromed brass *** bolt that held the handle on an old Wagner Ware Magnalite saucepan that I'd picked up at a thrift store.
1) little bit of both- That can make it more complicated. I have multiples of almost every cutting tool and try to keep the newest/sharpest separate from the "been used a few times". The new/sharp are for cutting new threads only. The others are for restoring/cleaning out existing threads. Yes it's more complicated but there's a big pucker factor when tapping a new hole in SS and the only tap you've got has been used a few times. When it starts squeaking and increasing the torque required and you watch the tap flex ever so slightly with each rotation.....Is it going to snap off down in the hole? This is an expensive piece and.......I wish I had a newer/sharper tap. Some materials work harden during drilling/milling and that last sharp tap is the only hope you've got. It's an anxious moment and the money saved on cheaper tooling seldom helps reduce the anxiety. Your first "Custom By Snap-Off" will be memorable and likely expensive.
2) probably mostly cast iron or aluminum (tapping) or steel (dies) as the vast majority of stuff I do is on cars- Aluminum is easy to tap but you darn well better use some tapping fluid or it can/will micro-weld itself to the tap. I'd almost wager that more taps have been broken off in aluminum than steel due to the relative softness of the material. It's soft, gummy, and sticks to tooling like shyte to a wool blanket.
Cast iron is often fairly abrasive and dulls a tap/die/cutter quicker than most other metals you'll encounter. Do you know how to feel the difference between a sharp tap and a somewhat dull one? I do because I've had to do this for every hole I've tapped in 35+ years and sometimes it can still fool me. I recently had a job at home I was doing that called for 1/4-20 in a blind hole. I selected some of the newer looking taps and got the telltale resistance that told me the tap wasn't cutting properly. I went through several others with no better success. I was about to give up and hope for the best until I ran across an old (20 years at least) Putnam I had ground to be a bottoming tap. I had large doubts but it cut better than the others and I completed the job with no worries.
My point is that when you encounter (not if....when) a difficult operation the last thing you want to rely on to pull your chestnuts out of the fire is some marginal quality tap from a dubious manufacturer. The more expensive stuff used in professional machine shops is more expensive because saving a few bucks on some silly tapped hole can make/break the job. Sure, use the cheaper stuff for cleaning/restoring but when it's new threads it's time to tap the hole and move on to the larger priority. It's not just the type of steel or the heat treating used in cutting tools, it's also the finish grinding that determines how many holes you'll get before it goes dull. Taps used in rigid machines with perfect axial alignment can last for hundreds of holes. Taps used by hand are NOT in axial alignment, work harder than they should, and go dull faster because of the previous two conditions.
Do you have any opinion on Westward (mentioned above)?- Never seen them used in the machine shops I've worked in so they may be ok for home use but I wouldn't want to trust them. Like I said above, the final grinding after heat treating makes a big difference. I once ordered a 1/2-20 UNF die from a company in Wisconsin to thread some SS rod and told the rep what I was going to do with it. It was the worst non-Chinese POS I've used, I attribute this to insufficient relief in grinding after inspecting it under magnification. The companies I listed may be new to you but they commonplace in professional machine shops. Sometimes what the pros use is what you want.
In the most recent instance I needed the #8 UNF tap to fix a slightly munged up chromed brass- Anything that has been chromed will give you problems due to the hardness and abrasion resistance of chrome. It's sometimes difficult even with a good sharp tap. This is an instance where knowing your materials is of importance. I prefer heavy sulfur cutting oil (smells bad) or some of the synthetic tapping fluids for tough jobs like this. Run the tap in to just start, use only a 1/2 rotation, back out, re-lub, and repeat. Long lead type taps will help ensure you don't cross thread.
fix a slightly munged up chromed brass *** bolt- You had to repair a "*** BOLT"? Use plenty of lube....
My apologies for the long winded reply, I'll go sit down in the back row now.
