Wednesday, March 15, 2017

Month-Going Longcase Clock Project Part 5 - Custom Longcase Hands

Cutting longcase clock hands always seems to be a popular subject. Everyone loves to see raw steel turned into beautifully cut curlicues and then turned a beautiful blue-black.

This is one of those "essential skills" that most clockmakers should learn, but that very few do. There are a few reasons for this. Normally it's a time/money issue. Hand cutting and filing steel longcase hands is a time consuming project, and most clockmakers would prefer to buy laser cut or mass produced replacements rather than spend the time and effort on custom hands. It's also expensive for the clients. Who wants to spend 100$ or more on such small parts? Then again, depending on the clock, you wouldn't want precision-cut copies. When you get into rare early pieces, the value of the clock justifies the price for custom work.

For someone like me, I do this work for fun, so I spend whatever amount of time is needed for the work I'm doing (because it's for me). That said, I will happily cut hands for a client so long as I'm adequately compensated for the work.

Anyhow, I think I'm starting to ramble, so on with it.

Materials Needed for Longcase Hands:

- 1/16" thick steel with a carbon content for bluing (test the steel if needed as not all steel will blue nicely) steel must also be annealed for easy cutting
- Paper pattern
- Saw blades*
- Sand paper and polishes

Tools:

- Jeweler's saw
- Files
- Alcohol burner or small torch
- A bluing tray filled with brass shavings, OR a cast iron skilled filled with fine sand, OR a thick brass plate
- Small vise
- Saw support (a wooden plank with a V sawn on the end)

Step 1: Pattern

Choosing the correct pattern is probably going to be the most important, and the most difficult part of the entire process. If you already know the exact pattern that you need, then give yourself a little pat on the back, and count yourself lucky. If you DON'T know which pattern to use, this is where you will have to do your research.

When I last talked at length about clock hands, it was on the mirror clock project, here: http://jcclocks.blogspot.ca/2015/06/mirror-clock-project-part-7-custom-cut.html. All the same points still apply when dealing with longcase clocks. The wrong hands can seriously affect the overall look and feel of the dial and of the clock. Hands for the period I'm copying (1680s, but with more of a 1740s chapter ring) vary WIDELY in style, shape, and size. It's also important to note that certain style hands look better on certain style dials. There is a huge variety of early square brass dials. Some have large ringed winding holes, wide or narrow chapter rings, centre engraving, seconds bits, etc. Everything needs to be taken into account.

It's also partially left to personal taste. I find that a fair number of clock hands are "ugly" or disproportioned in one way or another. The hour hand may be far too large compared to the hour hand, or I find a certain shape too pointy, too ornate, too plain, etc. Anyhow, after probably a month of debating, I narrowed it down to a particular pair of hands that I found on three similar clocks.

John Knibb London, Circa 1685
John Knibb London Ca 1685 8 Day (ht 6ft 2in, 10in dial) 06

Joseph Knibb Month Duration Longcase with Roman Striking, Circa 1685
Knibb Month Roman Striking Longcase ca. 1685 03

The third clock (not pictured) is another Joseph Knibb ebony longcase, month duration with Roman striking, and also circa 1685. This one was sold in the "Masterpieces From The Time Museum" sale back in 2004. The case is similar to what I want to build (caddy top, 3 finials, ebony case with no trunk door lenticle, but this one has flat Doric hood columns and I want Barley Twist ones).

The pattern was traced freehand on paper based on the dimensions I needed for my dial.

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Step 2: Sawing

The rest isn't rocket science. You saw the hands with a jeweler's saw. All the interior openings have to be cut with a pilot hole to start. I find it easiest to start with the openings. Try to stay outside the lines.

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Here you can see my cutting support block. The end has a sort of keyhole shaped opening.

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I have yet to find a great way to avoid breaking lots of blades. The only advice I can give is to never push against the blade. Let the blade do the work, and turn corners slowly. You can lubricate the blades with wax or oil, but this may ruin your paper template. The blades also become dull from use as you're cutting. *As a general rule, you need 3 teeth for the thickness of material you're cutting. The thinner the material, the more teeth you need. I believe it's 48 teeth per inch for 1/16 thick stock, but I found that slightly finer blades cut a bit more easily. Experiment and see what works. Luckily jeweler's saw blades are very inexpensive. All these broken blades probably cost about 1-2$ for the lot.

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Now, no matter how careful you think you're cutting, the results will probably look something like this:

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It's not great, but everything else can be cleaned up with files.

Here is the minute hand. Note that I'm using the other end of my saw support block (which has a narrower key slot).

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Here are both rough cut hand blanks:

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Step 3: Filing

It's hard to explain filing. I think it's pretty self explanatory. Remove bumps, clean up the lines and shapes, thin areas as needed, and then add any necessary "carved" areas such as leaf grooves, decorative ribbing, etc. Use any file size or shape that's convenient. I used maybe a dozen different ones.

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I gave them a fairly smooth polish, but I also didn't go too crazy trying to get beautiful perfect edges. I also didn't completely remove some of the steel's texture from the annealing process. I want them to look 200 years old.

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Step 4: Bluing

Bluing hands (or other small steel parts) can be a tricky process. The important part is even heat distribution. There are several ways you can blue hands, and some are easier than others. The traditional method is to heat them in a small metal tray filled with brass shavings. This is done over a flame (usually a blue alcohol flame). Alternatively, you can also use a thick piece of brass, and heat the hands slowly (do one at a time). You can also blue hands very slowly in a bed of hot sand. This is how I blued these hands. I used an old cast iron skillet with fine white sand. This method is very slow, but you have the best chance of success.

If you overheat the steel, you will pass blue and go back to straw. If you overheat the tips of the hands, the colour won't be even. If you screw up, just re-polish the whole hand back to bright steel and try again.

The hands are then quenched in oil or water.

If you want more of a black-blue, and you don't want to mess with heat, you can use gun blue. If you have a particularly odd blend of steel that won't blue correctly or evenly, gun blue can also save you. This was the case for a hand I made several years ago.

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Apparently I still had not polished the dial plate at this point. I will have to take more photos later.

2 comments:

  1. A great project JC. Not something I could tackle but I can see how much they add to your project.

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    Replies
    1. Ron, don't sell yourself short! If you can operate a hand saw (ie: move your hand up and down) you can cut clock hands. They may not turn out as perfect, but that's only a matter of practice. This is only the 4th set of clock hands I've ever cut. I did two sets in thin metal (even easier to cut - one set was brass), and one other single hour hand for a 1750 timepiece. If you cut away from the line (leave extra) you can just file up to the line. Filing is also not difficult.

      My friend Jim cuts hands with a metal cutting band saw, and there's also a scroll saw that can be used if you have one that is variable speed and with the correct blades.

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