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In this article I will describe how I made myself an acme tap for tapping soft materials.

Step 1: Fabricate Guide Blocks

The first item I made for this project was a pair of guide blocks to hold the threaded rod stock with. I made mine uniform, and square, then drilled holes out of the center of each. I used some phenolic cellulose material I had on hand, I am sure other materials are equally as suitable to use.
Interesting your device, pfred2. I have done some of these taps, but in a improvised way, with only one longitudinal channel. As the tap was used on wood, it worked. Never I tried to thread soft metals (alum, copper, etc) with it.
I need mine to thread plastic but I am thinking about making another and trying to harden it.
<p>Don't know what you have to harden in. I have forges, BUT, you can usually successfully do a shallow case harden by heating to a red in a dark shop or shaded area, and melting table sugar on the piece. Do it several to half a dozen times, make sure it is a bright red for only a short period of time and quench in water. Be careful--- you cannot do this if the metal is plated, and heating plated metal is very bad on your health. If it is plated, you can remove the plating in muriatic( 30% roughly hydrochloric ) , put the piece in the acid in a well ventilated area away from ALL iron and steel tools and electronics. As soon as the acid stops foaming, rinse of in water and pacify with baking soda and water, Then case harden as above. If you have a forge type thing, put the piece in a steel tube lightly blocked, (so pressure will not build up) filled with anything from white paper to sawdust to bone meal, rahide scrapps, horsehhof, or sugar, make wsure there is only a tiny hole on each end and make sure you can get the piece out very quickly. Heat to a &quot;cherry red&quot;- 1550 F. or so, for a hour, and open the tube, dump directly into cold water. The surface should be hard enough a file will not cut it. I have made mtal taps out of bolts doing this.</p>
<p>An angle grinder might work to cut the grooves. They wear down pretty quickly, but I've never heard of one coming apart.</p>
<p>What wears down quickly and does not come apart? You can try to cut the gullets by hand, but I doubt you are going to get very even grinds that way. It is fairly critical that the tap be symmetrical in form in order to function properly in use.</p>
Grinding on the side of a grinding wheel is really dangerous because it can cause the wheel to shatter and send shards everywhere.
I've heard that. I've never seen it happen though. Perhaps it happens if a wheel is severely undercut? That I could see happening, so try to keep the wear even is the best advise I can give. That grinder has a shield on it so even if the wheel did break on it, which is not going to happen, it is not going to go all over the place. Some grinding wheels are even designed to be used on their flat faces. I have a couple of those. They are not a whole lot different than plain grinding wheels.

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Bio: I was pfred1 but moved, changed my email address, and lost my password. I suppose worse things could happen.
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