Taperred Capstan

Know what you mean. 100F today. all time record was 101. similar day expected tomorrow. very dry. we are about 8 inches behind for they year in precipitation.

If taper will be not there then wire will slide here and there & it will directly effect on your final die.your die get wear out & you will find lot of wire vibration at enterence of die.Because capstan is taking the wire and releasing it on same time, so some space is also required for this process.This angle also gives a straight path to the wire in wet machine capstan. But in dry machine this angle helps only for sliding of wire.

vikas Pandey
Usha Martin Ltd
india

I have no idea why the taper is there. Fleeting is the only thing that sounds logical. Also, not everyone wraps the cones, except the final outside capstan ofcourse.
I actually find wraping the step cones as a bad practice ( draw machines are designed to slip, period. ). Unless, the draft is higher than 18% Ar and your running 20 awg or less.
Everyone has their own idea on what should be. Unfortinately, the manufacturers of the draw machines have been doing the same thing for over 50years, making machines. Us ( the wire manufactures ) make wire. The typical draw machine has not changed mechanically ( it does the same thing, the same way ) it has done for over 50 years. On another note, some draw machines with tapered capstans have traversing die boxes. This would rule out the notion that when the machine is at speed that the wire line stays in one spot on the capstan ( ofcourse it will go back and forth ). I just have no idea why the some capstans are tapered. I can tell you that not all step cones are tapered and function identically the same though.

Hello Tech 1,

I’m sure that there is someone out there older than all of us that might remember but fleeting is logical and an obvious reason for the taper.

You guys draw fine and very fine wire don’t you? Isn’t 35awg or so about your largest and a lot of what you guys do is 40 awg smaller?

I know that sometimes we did not use the first few capstans but it was because we were only using 4 or 5 dies in a machine built for 10 -13+ dies. This was because our desired finish wire was only 4-6 die sizes smaller than our input wire/rod.

When drawing large wire and rod, you need the wraps so that you can pull the wire or rod. If you don’t have enough wraps all you get is “wheel spin” so to speak. As you mention, unless your draft is 18% or higher. Guess what, most of the people out there drawing wire are doing a full B&S reduction with each die. It is only the people that are drawing finer wire that are doing less.

Some of the older Niehoff machines and Herborn machines had 4 step capstans. The first two were full B& S and the last two were ½ B&S. The smallest size these machines finished was about 45 awg. There were other machines that finished about the same size and/or smaller that were either all ½ B& S or started at ½ B& S and then went to ¼ B& S. Of course the European machines had a totally different % reduction scheme.

The ultra fine machines we used to have were (a) home made and (b) extremely simple (c) were full slip. We used them for about 46 to 55 and specialty things like gold, silver, silver plate and copper. At those sizes you needed full slip so that you could run the wire. Typically we used bottled water and liquid dishwashing detergent and some times minimal quantities. Some times the wire was so fine and had such a low tensile strength, that we nearly drew it dry because too much lubricant (and not enough lubricity) would cause so much drag the wire would break. These machines were really simple; a single tapered capstan or one with 10-12 steps. Smallest step about 1-1/2” in diameter at the small end and about 2” at the big end. There was a tank with an idle roller which was no more than a piece of copper tubing that could freely spin in the lube tank. Between the tank and the capstan there was a bar that held the dies. It was extremely simple and it worked as we drew what over the years totaled millions of feet of wire.

At these F and UF wire sizes, it doesn’t matter a whole lot as to if there is a taper or not.

There is much logic in both a tapered capstan and tapered step cone. Suppose you need a reduction 14% in final die. After drawing 1 or 2 tons of wire, the die size and the elongation will increase. Then, the wire will become looser on the capstan and it will try to shift towards the larger diameter of the capstan. If you do not taper the capstan there will be more friction and more heat generated and your capstan will wear faster because of this heat. After 6 or 8 months of running this way, you will find grooves in the capstan as a result.

Yes, you are right, not all step cones are tapered but if you analyze the life of tapered step cones and flat step cones you will find actual wear differences between the designs.

If taper is not there, groove formation will be faster because wire will not fleet as easily on capstan.

Thanks for the interesting discussion!