Saturday 14 November 2009

Making the Anchor

To mark out the steel for the anchor I either clamp the scape wheel directly to the high carbon steel sheet or mark it on paper then scribe from that. This Escapement is a square recoil escapement, square because the pallets span 7 1/2 teeth of the scape wheel which has 30 teeth.
So mark (on the paper) the 7 1/2 points (with a dot of your pen)
Coincidentaly (and this is not critical) the inner circle of your crossed out wheel is approximately right for finding the degree of angle for the two impulse faces (radius= .71). So scribe/draw a line from your dots and across the inner circle so it just touches it, one across the top from the left pallet and one down the right from the right pallet. Next put in the drop-off face angles; from the centre of the wheel draw a line outwards directly to both dots and past, shade in to make clear this is metal to keep.
Next find the position for the anchor arbor. The distance between the arbors is X.
X divided by the radius = 1.41 ~ so the radius multiplied by 1.41 = X.
In this case 1.15.
Use a compass to scribe this line, it doesn't matter too much where along the anchor the arbor hole goes. Place it centrally to look good.
Carve all this out of the steel keeping clear of the scribe lines as it can be shaped little by little in the depthing gauge. Hopefully it should jam as you have made it too big and when it is nearly there finish it off by planting it in the clock. When it is nearly there remember to file/polish down the drop-off faces which shortens the pallet instead of taking too much off the impulse faces making it 'drop' too far.

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