|Andrew Tinsley||15/01/2017 14:08:36|
|1630 forum posts|
I have the task of repairing a Victorian church key. It has two mirror image pieces (the ones with slots in them to engage the tumblers). One of the pieces has broken off and I need to replicate a mirror image of the existing one and weld it to the key shaft.
I intend to use a slitting saw on an arbour between centres, to cut the slots. The slots vary in width, the measurements being 3/32", 1/8" and 1/4" The steel will be held in a vice mounted on a vertical milling slide on the saddle of the lathe.
Now that sounds professional. BUT I do not have a clue about the arbour and how the slitting saw is fixed thereon! Most of the small slitting saws have an ID of 1" which would do me nicely. Help on this one would be much appreciated!
The key had been repaired before and the broken (now missing) piece had been brazed on. I shall get rid of all traces of bronze and mill a slit in the key shaft to receive the new part and I intend to weld it in place.
What type of steel would one be advised to use? Bearing in mind that the final welding operation will probably soften the new steel replacement.
Edited By Andrew Tinsley on 15/01/2017 14:15:18
|511 forum posts|
Your arbor should be greater than 1" diameter, say 1.5" - ordinary BMS should be adequate, length about 6 - 7".
The saw will sit somewhere in the middle of the arbor, so you will need to machine down the area to the right of where the saw blade will sit so that it is a nice sliding fit. This should be done between centres, so first job will be to put in a protected centre in each end. You will have to consider how you will drive the arbor. Simplest way would be to drill/tap a hole for a drive dog which will locate against your catch plate.
It would be better to put a collar on the arbor about 1/2 the diameter of the saw blade. This can be butted up against the 1.5" and Loctited in place. With the collar in place and running true, keep the 1" length for the expected maximum size of saw blade you expect to use. To the right of that, reduce the diameter to about 3/4" and screw cut, this will be for the locking nut. You will now need to reduce the remainder of the length to 5/8".
Make the locknut to suit the thread you have cut and relieve one side to allow the nut to tighten against the thinnest saw blade you expect to use.
Sorry about it being a bit long winded, and hope you understand everything.
6324 forum posts
There are multisize slitting saw arbors available with an half inch shank from the usual supplier ie China. Forget that as they have the usual quality and are made for a guaranteed fit ie small so the saw will run off centre. You are better off biting the cost bullet and getting one of these for the size required. It will also hold some gear cutters and side and face cutters. There are removable spacers and you then secure it with the nut on the end. (some other versions have a set screw in the end.
Think I might get one myself while there is the discount.
The cheaper option is one of these if you can machine it carefully to provide a shoulder then a cup shaped clamping washer held by an axial bolt. The cup will allow for different width saws.
In my view mild steel will do as our church locks are nice and smooth from a couple of hundred years use.
Edited By Bazyle on 15/01/2017 14:55:34
|Roy M||16/01/2017 12:02:04|
|104 forum posts|
I have posted a thread on slitting saw arbor.
|Martin Kyte||16/01/2017 12:22:21|
2755 forum posts
My dad refers to Allen keys as church keys. His dad was a coffin maker amongst other things. They were used to fasten the lid down.
"more useless information"
|John Reese||16/01/2017 18:28:07|
1035 forum posts
In the US Church Key generally referred to the piercing type of can opener needed bedore the advent of pop tops.
|Mike Poole||16/01/2017 18:34:45|
3343 forum posts
Some slitting saws have a key way but I would resist the temptation to use it. When hand feeding it could save you if the arbor spins in the saw but if you use auto feed then something is probably going to break if you get a jam up.
|2426 forum posts|
How long is the deepest saw cut to be ? Which thickness is that ?
|not done it yet||16/01/2017 19:06:31|
|6812 forum posts|
Vertical slide on a mill? Why use a slitting saw? An end mill in the chuck would do the job?
Probably better to fix the key blade to shaft before cutting the slots, as well. Brazed would likely be better than welded? And key shaft likely better if slotted first?
How big is this 'church key'?
|463 forum posts|
/\ /\ What he said /\ Might be wrought iron ... which is why it was brazed before..
|Cyril Bonnett||16/01/2017 20:31:28|
|244 forum posts|
In the past I have welded wrought iron fence posts and kennel bars using a hobby welder, some dating back nearly 100 years, my garden gate is made from wrought iron bars welded together.
|Andrew Tinsley||18/01/2017 15:57:32|
|1630 forum posts|
Thanks for the help so far. Let me answer a few questions that have been raised.
I am using a slitting saw and arbour together with my vertical slide, because I don't have a mill. The smallest width slot is just under 2mm and I suppose I could use a milling cutter in the lathe chuck. However I suspect the number of broken cutters would be too much for my patience or pocket.
The second (new) blade, if I can call it that (the part of the key with tumbler slots in it) appears to be either welded or more likely silver soldered into the keyshaft. The blade does go into a slot on the keyshaft and my preferred method of fixing it would be silver solder, on second thoughts.
I have to produce a mirror image of the existing blade and they are separated by 10mm on the shaft, hence I cannot silver solder a blank in and then use a slitting saw. This is because the "blades" have slots on both sides. Milling would be OK but not for me!
The size of the blades is 20mm long (from the shaft), 12mm wide and thickness varies from 10mm at the shaft to 16mm thick at the other end (it tapers both sides). To finally cheer me up, the end furthest from the shaft is finished in a neat semicircle.
The narrowest slot is just under 2mm wide and 6mm deep. There are 14 slots in all, 7 on each "blade" (Can someone tell me what the correct name is for my "blade"?).
1159 forum posts
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