How to use a die?

It is interesting to note that both silver steel and gauge plate contain chromium............

Andrew

Aren't the percentages of Chromium very different though between Stainless and silver steel/gauge plate?

I must admit I always put the non-sharpness of HSS down to the presence of Tungsten Carbides which cannot be made very sharp due to their size.

Jon

> It is interesting to note that both silver steel and gauge plate contain chromium............

Yes but less than 1/2% rather than about 5%.

> I must admit I always put the non-sharpness of HSS down to the presence of Tungsten Carbides which cannot be made very sharp due to their size.

You may be right, I would tend to believe a chef on how to make a souffle, rather than alloy science.

Neil

There are variations in composition (alloy) of both carbon steel and HSS, the choice of tap or die is dependant on what material and the type of operation. I threw all the cheap carbon steel taps and dies I had in the scrap bin as they were no good at cutting anything like a clean thread, could not see any point in trying to evaluate any carbon steel tap or die and have stuck with main stream makers like Dormer but even that is not as straight forward as it depends on the material to be threaded, stainless steel can be a bit problematical but with the correct tap or die reasonable easy.

Bob

Given the number of 'save my restaurant' and 'kitchen disaster' programmes on the television, I'm not even sure I'd believe a chef on making a souffle.......

Thanks for the information. It seems that there is no real scientific explanation for carbon steel taking a sharper edge. It is certainly a fairly widespread belief within the knife making community that carbon steel is better, and it may be, but I don't think it is applicable to machining. A thin knife edge isn't going to last long when cutting metal. Cutting metal is more of a shearing process, where other factors are also important such as BUE and wear on the top of the tool.

While there is a correlation between tool finish and work finish it is not necessarily unity, it depends upon the purpose of the tool. Certainly for a form tool the detail surface finish of the tool will be reproduced in the work, but for something like a standard knife tool the correlation between tool finish and surface finish is less clear. When grinding HSS toolbits I normally run a diamond hone across the tool after grinding, but I do use quite a coarse grinding wheel. I would agree that the smaller the work the more important the tool finish, but I don't do small stuff! All these tools were made from carbon steel (silver steel or gauge plate):

The reliefs on the taps were ground but the spline and hob cutters were used straight from machining without any honing. They cut fine on steel.

I have the book on hardening and tempering by Tubal Cain, and agreed there is a lot of useful information in it. However I think he is wrong on carbon steel being harder that HSS up to a given temperature for cutting tools. A search round the internet gives a range of hardness for HSS from 63-67 Rc. I've made a rough measurement of hardness on a couple of bits of old HSS, and they are both greater than 65Rc. The datasheet for Stubs silver steel gives a maximum hardness of 66Rc; at the upper end of the range for HSS. However, once the silver steel is tempered at, say 200ºC suitable for cutting tools, the hardness drops to 60-62Rc. The data that comes with my gauge plate doesn't give a maximum hardness, but I would think it would be similar to silver steel. For tempering at 200º it gives a range of 60-61Rc. The maximum and tempered hardness figures for silver steel and gauge plate are borne out by the measurements I have made when making the cutting tools shown above. Given these numbers I don't think it is justified to say that carbon steel is harder than HSS at low temperatures. The measurement of hardness is not an exact process anyway, certainly when using the indentation method, as it depends upon how the hardness varies with depth.

One last snippet, Swann Morten surgical scalpel blades can be bought either in stainless steel or carbon steel. Presumably the choice is up to the preference of the individual surgeon. My last major operation didn't involve scalpels, so there would have been no point in asking the surgeon. And I'd already niggled him by asking too many technical questions about the equipment to be used which he couldn't answer!

Andrew

It seems to me that there are two points being missed in this interesting debate:

1. That one difference between Carbon and HSS taps is that Carbon taps, being at the cheap end of the market, are not ground after heat treatment. This means that any distortion is not corrected. HSS, being more expensive anyway, is ground, so the thread is (should be) more accurate and smoother.

2. The chef debate is not about HSS at all, but rather the distinction between Carbon steel and stainless, for kitchen knives which need to hold a good edge. Chefs don't like rust, and they work in hot damp atmospheres.

Hope this helps

Tim

This, on the development of High Speed Steel, may be of interest.

MichaelG.

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Edit: changed hyperlink; to land on the summary page, instead of directly downloading the thesis.

Edited By Michael Gilligan on 18/03/2015 14:12:04

Update: Based on all the advice I bought an adjustable, HSS die, and used a drill press to apply pressure and keep the die straight.

The die I bought was only AUD 10, and I was able to thread a brass rod first time.

I will give stainless steel a try later.

Thanks for all the help!

Tom

I have had a lot of problems with HSS tooling because it seems to dull so easily

At the moment I use carbide for nearly all my lathework and I have a cobalt HSS tool which is fantastic for the shaper

On the tap front I dont have sufficient experience to offer an alternative to HSS which has always done its job for me

Interestingly, the people who build really competitive indoor free-flight models (F1D) swear by carbon-steel blades for precisely cutting indoor grade balsa without crushing. I once imported a few dozen packets of 'Candidus' blades from the U.S. and had no trouble trading them at the (Oz) National Champs.

I was lucky enough to be given a brand new pre-WWII Swiss 'Allegro' razor blade sharpener. It's a very interesting tool that sharpens and hones a blade, flipping it over to do both sides. I can organise a photo if anybody is interested.

As a builder of indoor models myself, the difference between carbon-steel and stainless-steel razor blades is readily apparent when one attempts to snap a blade to a point.

My finest (sharpest) scalpels (used for eye surgery) are also made from carbon steel so maybe it all boils down to the refinement of the grain size. The surgeon who gave them to me is also now using ceramic blades and a laser for some jobs.

I suppose that it's 'horses for courses' but I reckon that carbon steel still has it's uses, even though quite specialised.

* Danny M *

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Yes please, Danny

MichaelG.

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P.S. ... To perhaps slightly confuse the Carbon vs Stainless debate; the best razor blades I know are Merkur [a subsidiary brand of Dovo, Solingen], and these are described as Platinum coated High Carbon Stainless Steel.

Edited By Michael Gilligan on 25/03/2015 08:28:36

I don;t think carbon steel takes a 'better' edge necessarily than other steels but it definatey holds that edge way better than the kitchen knife comparison with stainless steels used. I observe the same with modern cheap pocket knives or even a large Bowie knife I bought recently. Brand new that bowie knife could shave the hairs on my arm but just cutting a couple of bramble trails to free a sheep was enough for the edge to be dulled.

I can't recall any surgeon who used carbon steel scalpel blades since the availablity of stainless. rarely in any op is one doing enough cuttng to dull a blade and they're not going to be reused. If it did dull you'ld just bin and swap.

Scalpel blades are used in all sorts of crafts and the market is there for that too. The only other reason for wanting a sterile bade holding an edge for longer (if the carbon scalpels do?) might well be in plant research and propagation with woody stems and the like.

Indeed you can (or could) get scalpel blades in paper spaced ot foiled packs of 10+ compared to the single wraps of surgical stuff. In prehistory I;ve worked with shonky folk that would chuck a wrap of those in spirit to save a half-penny

My woodcarving chisels get honed to extremes and then hold a decent edge.. carbon steel again. And for the ultimate in sharp I once had a freezing microtome for cutting histopath sections from a CO2 frozen chunck of patient. The lab that resharpened them for me used to check the quality of the edge with high-power microscopy after lapping/honing the edge with fine paste on a rotating glass disc. they'd cut many thin slivers through frozen tissue before showing any signs of going dull - so thin were these few micron slivers that they could only be hadled with a very soft wet brush to manipulate them through to fixing them on slides.

Ok, as this is getting away from the subject matter I started a little thread of its own about my razor blade sharpener as it is a fascinating device.

* Danny M *

Final update: With the new die and technique I was able to thread stainless steel as well -- in fact I just started the thread with the new die, and then used the old cheaper die to continue cutting it, so it looks as though the lack of expandability is the problem, rather than the sharpness of the cheaper die. Or perhaps the cheap die would cut from the beginning now that I am using a drill press for pressure and angle. Have to try that.

Tom

..just another nostalgic snipet into the debate:

Surgical scissors and needleholders are available with tungsten carbide slivers inserted for the cutting/holding edge and marketed with gold anodised handles. Undoubtledly they hold an edge way better than surgical stainless.. until staff drop them and kick them around the theatre. In practical terms way cheaper to buy cheapo pakistan made surgical stuff and sling it at any signs of wear beyond a simple slick-up with a stone.

Who remembers the travellig knife sharpeners with a wheel on the front of their bicycle - up on it's stand and peda away withe the stone wheel spinning between the handlebars as they sharpened?

( and apologies for hijacking the thread again)