Smallest Reeds...

[d.elliott]

May I offer this suggestion for heat-treating small pieces of metal, such as feeler gauges?

 

Clamp the end of the feeler gauge between two small blocks of steel, an old pair of ‘Mole’ grips should suffice, and heat the blocks of steel to ‘cherry red’ and allow the heat to transfer to the feeler gauge, this will give you more time between reaching the required temperature and quenching. Once quenched gradually re-heat the blocks to the required pastel colour frequently wiping the feeler gauge with some fine sandpaper on a stick so that you can see the colour change as it takes place.

 

Tony,

 

The feeler guage is already hardened, so it does not need re-hardening, and I think that by introducing heat sink blocks as you are suggesting, then you are adding a level of complexity where the reed steel is actually soaking longer at temperature than it needs to with all the issues of grain growth etc.

 

However if it works then great, have you tried this technique?

 

Dave

[Dana Johnson]

Just remember you cannot do this to a single reed, or a thin strip of steel, not without specialist kit.

 

A domestic oven can reach the temperature required for tempering. I have successfully heat treated home made cutting tools by heating to cherry red then quenching, followed by tempering in the oven to a dark straw shade.

For cutting tools I like the light (file hard ) to dark straw shades depending on what I am wanting to cut. (Light straw for metal dark straw for wood) but for reeds I feel these colors are still too brittle and prefer the purple flecked with blue stage, which is in the upper range for spring tempering which is after all what reeds are, not cutting tools. I can't get my oven ( except in the cleaning cycle ) to get hot enough to do this but other suggestions given especially the sandwich method which makes the heating more controlable is a good one. Regarding how hot to heat metal for the hardening stage, different alloys require different temperatures. This first stage is called normalizing, where all the constituents of the alloy are "dissolved" in the metal. High carbon steels like the 1095 spring steel normally used for reeds only need to be heated to about 1450 to 1500 Degrees F. which is an orangeish red color to reach the normalizing temperature. with a quench from there. I prefer oil for quenching really high carbon steels since they are a little crack prone when quenched in water. Reed steel is so thin that oil quenching is plenty fast enough. Tool steels with chromium or tungsten in them need much higher temps with high speed steel getting into the white range above 2000 degrees F. If you heat spring steels that hot, you will lose so much carbon that the outside will become quite soft ( unless you do it in an inert atmosphere ). Even in tool steels you often have to grind off the surface de-carburized layer to get to the truly hard surface after hardening.

All this is just for reference sake since starting with spring tempered steel ( clock spring, spring tempered band saw blade, chain saw springs or the like will make workable reeds without any heat treatment whatsoever. I prefer harder tempered spring steels since they retain their set better than the softer ones but they are harder to file. Blue tempered shim stock is something that is available to places that supply machine shops and the like and works quite well. The alloy is right and the temper is relatively easy to file.

Regarding fitting reeds, what is required is practice and you'll find a hand lens or low quality stereo microscope for geology (10-20X )incredibly helpful if you plan on doing any number of reeds. If you are going into the biz, get a really good geology type microscope. It will be much easier on your eyes for the hundreds or thousands of reeds you'll do.

While there are special tools that make fitting reeds easier, you generally have to have them made at fair expense. Not worth it for someone who isn't making concertinas for a living. Practice works pretty well and comes a lot cheaper.

[tony]

Tony,

 

The feeler guage is already hardened, so it does not need re-hardening, and I think that by introducing heat sink blocks as you are suggesting, then you are adding a level of complexity where the reed steel is actually soaking longer at temperature than it needs to with all the issues of grain growth etc.

 

However if it works then great, have you tried this technique?

 

Dave

 

 

Dave,

 

I only mentioned the heating to cherry red because of your reference to raising the temperature to white heat and its consequences. Heating the blocks of steel and allowing this to transfer to the ‘reed’ (heat sink suggests the reverse of this) gives far greater control over temperature since it changes less rapidly.

 

Yes I have used this technique, albeit not on concertina reeds, and was indeed taught to use it when ‘in the field’ and only a blowlamp was available as heat.

[d.elliott]

Tony,

 

The feeler guage is already hardened, so it does not need re-hardening, and I think that by introducing heat sink blocks as you are suggesting, then you are adding a level of complexity where the reed steel is actually soaking longer at temperature than it needs to with all the issues of grain growth etc.

 

However if it works then great, have you tried this technique?

 

Dave

 

 

Dave,

 

I only mentioned the heating to cherry red because of your reference to raising the temperature to white heat and its consequences. Heating the blocks of steel and allowing this to transfer to the ‘reed’ (heat sink suggests the reverse of this) gives far greater control over temperature since it changes less rapidly.

 

Yes I have used this technique, albeit not on concertina reeds, and was indeed taught to use it when ‘in the field’ and only a blowlamp was available as heat.

 

 

Thanks Tony,

 

My question related to if you had tried to temper a reed using blocks, I don't doubt that the use of blocks as thermal 'stabalisers' is a useful technique in many applications, I am just trying to think through the implications to a thin strip of reed spring or feeler steel. Certainly a blow torch, subject to controleability, would be quite fierce and may well demand some stabalising on the item being worked.

 

Dave