Burnishing

Hi Guys

I am just finishing the main wheel and barrel of my JW 8day clock. I did turn the barrel arbor down to 5/16" on the ratchet end as per the drawing. I have reamed the hole in the main wheel to 5/16" as described by JW. The problem I have now is after burnishing the arbor its .003" undersize. Should I have allowed for this when turning and made it oversize?

I have read on the forum that we engineers make things tight, am I worring too much or will I have to remake it?

Thanks

Bob

I wouldn't worry about it. The usual way to correct this would be to bush the plate. A clock must rattle. Engineers usually make things too tight for clocks.

You will always loose a couple or three thou when finishing an arbor so it is best to turn to a couple of thou over and then use the pivot file/arkansas stone/ burnisher. The wheel should then be drilled (or preferably bored for a main wheel) to a few (say 3-5) thou undersize for the finished arbor. The hole is then brought to size using a five sided clockmakers broach - this is used carefully from each side of the wheel until the arbor will fit freely but without shake.

Yes, clocks should be a "rattling good fit" but you should try to get a good fit between wheels and arbors - the main wheel should NOT wobble about! The main source of "rattle" should be between the pivots and bearing holes in the plates - these must be completely free but not too loose - all a matter of experience and careful fitting during construction and assembly. Better to make things a little tight at first as you can always use a broach to ease a bearing.

To fit the collets of the other train wheels onto their arbors you can make your own reamer from a spare piece of the arbor - simply file or grind one end at about 30° to make a long flat taper - and use this to ream the collet holes precisely to size (pivot steel is hard enough to do this but you may find silver steel needs hardening and tempering first - you should get away with using it unhardened if your reamer is sharp!).

If you look for "clickspring" on you tube you will find some really good videos about his construction of a great wheel skeleton clock (another of John Wildings designs).  These are really good and cover just about everything you need to know to help you build your clock.

Edited By Bizibilder on 26/11/2020 11:27:56

Edited By Bizibilder on 26/11/2020 11:29:00

Edited By Bizibilder on 26/11/2020 11:31:37

Don't worry about it. Just note it down for the next time.

regards Martin

Hi Guys

Thanks for that. I'll check out the Clicksprings on you tube.

Thankfully I have only machined one end of the arbor at the moment. There is only a very minimal amount of play on the main wheel. I have not started attacking the frame arbor holes yet.

Regards

Bob