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How To Make A Clock In The Home Machine Shop - Part 20 - The Crutch Assembly And Eccentric Bushing

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Published on Aug 27, 2016

Making The Crutch Assembly And Eccentric Bushing, by Clickspring.

In this video I make a start on the escapement of the clock, starting with the crutch assembly and a component that permits a slight adjustment of the pallet depth of engagement with the escape wheel.

If you would like to help support the creation of these videos, then head on over to the Clickspring Patreon page: https://www.patreon.com/clickspring
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A very special thank you to Patrons Dan Keen, Samuel Irons and Sean Kuyper.
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You can also help me make these videos by purchasing via the following Amazon Affiliate links:

Cameras used in this video:
Panasonic GH5 - https://amzn.to/2rEzhh2
Panasonic X920 - https://amzn.to/2wzxxdT

Tools & Shop Products:
"Solidworks 2013 Bible": http://amzn.to/2FObS1D
Sherline Lathe: http://amzn.to/2pnXM19
Dykem 80300 Steel Blue Layout Fluid, Brush-in-Cap (4oz): http://amzn.to/2HGPaJJ
Generic Dial Indicator 0.001": http://amzn.to/2FOFTyF
Dormer A190202 Jobber Drill Set, 1.0 mm - 6.0 mm x 0.1 mm Size: https://amzn.to/2DR5fdb
Dormer A190203 Jobber Drill Set, 6.0 mm - 10.0 mm x 0.1 mm Size: https://amzn.to/2ITfeTa
YG1 NC Spotting Drill 8% Cobalt HSS 1/8 to 1/2" 120 Degree 5 Pc Set CNC Machine: https://amzn.to/2G7ylv6
Hegner Scroll Saw: https://amzn.to/2IhteVW
Super Pike Saw Blades Size 4/0 pkg of 144: http://amzn.to/2IO6aPw
Blue Matador Abrasive Paper - https://amzn.to/2IAFiBT
Saint Gobain (Norton) - 4 Arkansas Stones + case: http://amzn.to/2HCOAMX
Loctite 231097 603 Retaining Compound, 10 mL: http://amzn.to/2pid6vR

Abbreviated Transcript:

00:21 Generally speaking the escapement is considered to be the pallets and the escapewheel, but there are usually a few extra components required to make the whole thing work, and its those related components that I'm making in this video. There's an eccentric bushing that permits a small adjustment of the pallet depthing with the escape wheel, enabling fine tuning of the escapement.
00:41 And then there's the crutch assembly, which receives the energy released by the escapement, and transmits it to the pendulum to keep it moving.
02:17 With the taper formed, I transferred the work to the mill, to put in the other features. The embryo part can now be cut from the parent stock, to form the small clamping slot. But before I make the slot, here's a closer look at the fastener hole. One half has been drilled for clearance, and the other half is at the correct diameter to be tapped for the fastener thread.
05:30 I've got the work set up on this pumice stone to protect the bench, and the heat is being applied using a small butane torch. Up close, you can see the flux run, leaving behind a tiny matrix of silver solder adjacent to the join. A little more heat, and then that solder melts and wicks into the small gap between the parts, while the excess solder forms a nice fillet.
06:56 And I'm happy enough with a tool finish for this part, so I'll leave that as the final surface. The spigot has done its job, so that can be taken off with some abrasive paper, leaving a grained surface finish on that underside surface. The final step for this part is to use needle files and abrasive paper to bring the perimeter to final shape and dimension.
09:06 The bend locations are positioned roughly one third in from each end, and it really is just as simple as getting a good hold of it in the vise, and giving a careful push until its about right. The 3 parts of the crutch assembly are now complete, so a small spot of Loctite on each end is all that's required to bond them together. OK, now on to the eccentric bushing.
10:57 The central axis was located with a wiggler, and then a tiny offset was introduced to the spindle, so that the hole would be formed off center - as the name of the part suggests.
12:46 All three were made in the same way that you've seen in previous videos, using the small lathe. They were then hardened, tempered, and then polished and blued. Ok, so with the fasteners complete, I can start to put a few of the bits and pieces
14:56 Particularly since the eccentric bushing can an additional offset angle depending on where it sits in its rotation. Once it looked about right, I put the frames back together to give it all a test fit.
15:37 I've left the barest clearance between the crutch fork and the pendulum block, to minimise energy loss, and the eccentric bushing is ready to be adjusted as required in the next episode. Which leaves just a few key components to be made, before I can set the clock running.

References:

John Wilding "Large Wheel Skeleton Clock" construction book can be purchased online from Ian T Cobb:
http://www.clockmaking-brass.co.uk/cl...

Making The Crutch Assembly And Eccentric Bushing, by Clickspring.

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