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Don't know if you are still looking for an answer to this question, but yes, variation in hardness is likely, probably even between different lots from the same manufacturer. The brass will work harden as it is formed. Assuming that different manufacturers use different grades of brass, different starting diameters, different starting hardness (or heat treatment), then the finished pins will have different hardnesses. Unless the manufacturer has to maintain a specific standard for the finished pin properties, they likely will only care about forming the pins to the correct dimensions. If they have to hold to a required finished hardness, then they will probably anneal the pins after forming to get the hardness required.

Try Googling long stitch binding. This is a technique that sews the book sections to the spine area of the cover material, which works well with thinner leather. It requires that you used folded sheets to make the pages, but the books open pretty much flat and you can do some nice design things with the cover material and thread.

That was an interesting talk about luxury goods and the dumbing down of the market. Gotta love corporate greed. It does give one hope for making a living in the handmade goods market, though. Thanks for posting it.

You can do quite a bit in QB. Even though it is not set up specifically for custom work inventory tracking, it can be made to do it. The most useful thing is the group item, which is completely flexible, and can be changed on the fly within an invoice or sales receipt so that you can deal with custom things without having to create individual items for every custom product you make. For example: I can create a group item, "Notebook", and define it as having an item "cover leather", and item "lining leather", and item "labor". When I use the group in a sales receipt or invoice, I can fill in the actual amount of each item used and the price I want to apply, add additional items or remove unused items. It will only affect the information on this sales receipt or invoice, and the next time I use it I can do different things with it as needed. Totally flexible. QB will reduce the amount of "cover leather" and "lining leather" in inventory (if those items are inventory items) and add their values to COGS account, and the total sale amount goes into whatever account you defined for the income. You can also use this with non-inventory items, QB just handles the information a bit differently. You can try out the technique easily enough by abusing one of the sample companies that QB has (at least in the old version I use). What will mess with your head is trying to decide what to track as inventory and non-inventory parts without spending all your time bookkeeping, yet provide accurate enough cost info (how many rivets can a project use before they become a significant part of the cost tracking? Ahh, ahh!!!). Feel free to pm me if you want more info.

Ha ha, it depends on the engine. Most of the US passenger car intake valves are low to moderate alloy content martensitic steels hardenable at 1550F for 15 minutes followed by oil quench (air cooling won't harden fully and plain water will likely crack the part, but if you have access to PAG quenchant at the proper concentration, that will work). Tempering temperature will depend on what final hardness you want, but generally 1 hour at 300F -500F will temper without much loss of hardness. If you are going to harden this using a torch, you want to get to a medium reddish-orange color with just a hint of speckling (oxide forming and popping off the surface look like black speckling flecks)

How ironic, I spent 16 years involved in the manufacture of engine valves... At least in the US, most engine valves are not sodium or sodium-potassium filled. These are typically for air cooled piston aircraft engine valves, and certain high performance engine valves (think very pricy). If you know the engine the valve was intended for, or have the part number (might be etched into the stem), you can probably get the information by checking the aftermarket listings for replacement parts. Typical passenger car intake valves are one piece hardened alloy steel. Truck intake valves often are hardened alloy steel, but it depends on the engine and operating conditions. Sometimes they are two piece construction, with an austenitic steel head welded to a hardned alloy steel stem or tip. Exhaust valves generally are an austenitic stainless steel or superalloy welded to a hardened alloy steel stem or tip. On some valves where seat wear is an issue in the application, there will be a weld hardfacing in the over Rockwell C 50 range. I would think a one piece intake valve would be usable to make tools from. You could reharden and temper it after fabricating your pattern.

If these are not going to be suprises to the recipients, just ask them their opinion. I can't say I have experience with collars, but having sensitive skin makes me look hard at whatever I think about wearing. If the choker/collar is made of a stiffer leather, I would think it would chafe the more delicate skin of the neck. Also, I would wonder about potential skin sensitivity to any dyes or leather treatment products on bare leather or even leather lining. It is not necessarily a problem for most people. FWIW.