Custom Tallcase Suspension Spring

upstateny

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I have an old English? clock movement on which the opening in the foot of the crutch is much too wide for commercially availabe suspension springs. I have some brass bar stock that is the correct thickness for the opening.

I am wondering how I might cut the slot for the spring?
 

novicetimekeeper

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I'm sure somebody will be along in a minute but isn't it a jewellers' piercing saw you want? They have a range of really thin blades.
 

Uhralt

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I have an old English? clock movement on which the opening in the foot of the crutch is much too wide for commercially availabe suspension springs. I have some brass bar stock that is the correct thickness for the opening.

I am wondering how I might cut the slot for the spring?
Do you have a picture of your pendulum and the crutch? Usually there is a brass block screwed to the pendulum rod with a slot for the suspension spring. Timesavers sells a suspension spring for English tall case clocks with the brass block already attached. It might fit your movement.

Uhralt
 

upstateny

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Thank you Uhralt, I already have a wide selection of commercially made springs, none of which have a thick enough lower block for the crutch. (See attached photo)

I have a blobk that fits well but need a way to cut the slot for the spring. The crutch opening is 8.5mm most of the commercial springs have a block thickness of around 5mm.

20190927_111133.jpg
 

Uhralt

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Thank you Uhralt, I already have a wide selection of commercially made springs, none of which have a thick enough lower block for the crutch. (See attached photo)

I have a blobk that fits well but need a way to cut the slot for the spring. The crutch opening is 8.5mm most of the commercial springs have a block thickness of around 5mm.

View attachment 550124
If you have a mill and a thin slitting saw, that should do it. A thin jeweler's saw could also do it but I find it difficult to cut a deep slot straight with them. Somehow the blade always wants to wander.

You could also beef up the 5 mm block by attaching thin brass shims to both sides of the block.

Uhralt
 

bruce linde

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ok, wait... are we talking about cutting a slot for the top of the suspension spring? where it hangs from?

or are we talking about a new block that fits in the crutch slot.

if the top... jewelers saw, yes?

if the pictured crutch slot... a new block, pinned to the bottom of the suspension spring material, and drilled and threaded on the bottom for the pendulum rod, yes? or, you could just build up a stand block to the desired thickness with shim stock.

it sounds from the original question like you're talking about doing something with the crutch foot... if so, why? the suspension spring and pendulum should just slide up through the crutch foot, with the bottom block giving just enough clearance/slop so you can hook the top of the suspension spring in the suspension hanger... yes?

late night last night... sorry for any confusement on my part!
 

bruce linde

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and of course i see that uhralt already suggested building up the the thickness of the lower block...
 

shutterbug

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It's difficult to see in the photo, but it looks like the crutch loop has been soldered in place? If so, it may be the wrong size and could be replaced with one that's narrower.
 

R&A

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If you had a mill you could use a slitting saw . I had to make one of these last year for a 200 year old movement.
 

upstateny

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Yes, was speaking of cutting the slot in the lower block for the spring. However I will probably do as Uhralt suggested and build up the block. I do not have a mill, so am left with building up the block. Shutt, I will look perhaps the loop is soldered on!

Just checked, loop is not soldered on.
 
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Willie X

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Unless you need more than about 1.5 mm a single shim on one side will be fine and make sure to make your shim cover the whole face. Not very notacable if the whole face is covered and all the edges filed to match. Willie X
 

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Rockford's early high grade movements by Greg Frauenhoff