Is this steel bar considered mild unhardened steel?

I have only found one source for these taps Victor Machinery. One style and Chinese made. No flute options. The company was bought out by another one and future availability is in question. These taps have been out of stock for months. I did just grab a used one on ebay made by an American company, no longer in business.
 
If you don't own a number drill set you might consider investing in one. I often use a slightly larger drill size than recommended for tapping steel.
I wouldn't be without my 115 piece set (numbers, letters, fractional)
-Mark
ps import taps and other cutting tools are often quite brittle compared to domestic ones
 
Have you tried ordering your tap from a proper supply house? I find it hard to believe that 12-20 taps are only made in China. Gunsmith suppliers would be another good option, since 12-20 is in the range of gun screws over the last 150 years.
 
Did some research and OP is correct about this being a rare thread size.

12-24 is the standard coarse pitch. 12-20 is a wildcat and looks to be used on old Stanley tools.

Victor Tools does seem to have the only supply I could find, albeit out of stock.

Rutland Tool lists a 12-20 tap- Model#:21440079 Catalog Page#:110
 
I'd recommend trying a test hole with a less expensive tap. Hillman does sell a hardenable steel for a much higher price at hardware stores. One of the people there said is was drill rod. Spark test says it is mild steel. If your steel is difficult to tap, try known good mild steel. If that doesn't work, get help. Otherwise, give that piece of troublesome steel a lick with a propane torch until it cycles all the colors to gray. Do not heat it to cherry. Let it cool. It should do fine.
 
I don't know about your particular tree, but when I do similar with the blast cabinet I use wood to hold bolts, screws etc.. Some times tapped sometimes press fit.
Dave
 
If all you need is a threaded hole to hold screws for bed blasting it certainly is not necessary to use up rare taps. Using wood or plastic you could just drill a hole a tad smaller than the screw and then drive the screw into the hole.
 
The tap drill for a 12-20 is #19 (.166") for 77% thread form. If you used a 3/16 (.1875") drill, that would result in only 44% thread form.
If you broke a HSS tap using such an oversized tap drill, something is WAY out of wack.

That Hillman stock is the poorest quality I've ever experienced and there certainly may be hard spots/impurities, but with a 44% tap drill ???
Another factor is that you may have bought hot rolled material which has the mill scale present on the surfaces. That scale can be very hard and abrasive. It's a good idea to, after tap drilling, chamfer (countersink) both sides of the hole to larger than the major diameter of the thread (.216") so the tap will never touch the scale.

As far as the availability of replacement taps, I would Google "special taps" and contact some of the many USA options. If they won't sell direct, ask for contact info for some of their major distributors.

Good luck.
 
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Any reason why you need to use steel for your "tree"? Can you use aluminum or other soft materials or methods as mentioned above?

I use something similar for shortening small screws on the belt sander. I use aluminum cause it's easier & quicker to tap plus these things are sacraficial for me. I was down to one left & made some more recently.

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Just noticed this thread. I’ve purchased some Hilman rods from big box and hardware stores. Personally I think most of what I had was some of the nastiest plain steel I’ve had in my lathe. It’s like turning stainless steel except it doesn’t even clean up good.
Buy some decent stuff from one of the Online Metal sales websites. I really like the 4140 and 1144 grades. Also McMaster has a great selection of metals. They describe the grades and even have descriptions like..... “easy to machine “
All of the leaded steels machine very nicely.
That Hilman stuff will make you think something is wrong with your lathe or your skill set.
It’s garbage steel.
 
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