Machining a replacement jacobs style chuck key?

This topic has 8 replies, 7 voices, and was last updated 19 March 2021 at 15:22 by Howard Lewis.

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19 March 2021 at 12:03 #28055
jon hill 3
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@jonhill3
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19 March 2021 at 12:03 #534868
jon hill 3
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@jonhill3
I just bought a 2nd hand Jacobs style chuck without its key, a Porta AGP 1.5-13mm. I know the sensible option would be to take it back or ask for a key to go with it which I may still do.

Out of curiosity what would be involved if I wanted to machine a replacement key?
19 March 2021 at 12:44 #534875
Emgee
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@emgee
Jon

First you need to match the gear shape/size then decide on the number of teeth required, the diameter of the pin is not so important as you can easily turn it down or add a sleeve if too small.

Perhaps a search for the make and model number will bring up a supplier. (KS2)

Emgee

Edited By Emgee on 19/03/2021 12:50:17

Edited By Emgee on 19/03/2021 12:51:40
19 March 2021 at 12:51 #534876
Nick Wheeler
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@nickwheeler
I found a replacement key for the chuck supplied with my X2 mini-mill 15 years ago at B&Q. They had 3 sizes so I suspect there are standards for these things
19 March 2021 at 13:15 #534880
Jeff Dayman
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@jeffdayman43397
Given the low cost of "4 way" so called "Universal" drill chuck keys such as the one at the link below, I would suggest you save your shop time for your model engineering projects rather than making your own key. There are many sizes, as the data sheet shows. I am sure you COULD make your own, with a lot of careful measuring and multiple trial and error tests, but not sure why your would want to, for a mass produced item.

https://www.mcmaster.com/3175A36/
19 March 2021 at 13:55 #534887
Chris Evans 6
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@chrisevans6
Miss directed energy but a nice project to do. Be wary of the four way keys available cheaply, they are cast and the metal used is soft. I have tried 2 now.
19 March 2021 at 14:47 #534895
Howard Lewis
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@howardlewis46836
Funnily enough, I have a chuck (mounted on a Jarno taper ) which is now operated by a "4 way Universal" key. But not so universal that the spigot fitted the chuck.

It did, after a short time in the 4 jaw chuck on the lathe!

The key is definitely the lower quality part of the combination.

Howard
19 March 2021 at 15:14 #534897
larry phelan 1
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@larryphelan1
Long time since I heard anyone mention a Jarno taper.
19 March 2021 at 15:22 #534900
Howard Lewis
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@howardlewis46836
I picked the chuck, a really nice looking none cheap, (£2 )at a show, but could not find a Jacobs arbor for it.

At home on the back of the chuck saw there was "No.2", so took a wild guess that it was a Jarno. Having found that all sizes of Jarno had the same taper, tried setting over the Topslide, by eye. Blued after the first attempt, and resisted the urge to start backing horses, since it was spot on!

Pity that that the Jarno with its constant 2 degrees 15' taper did not catch on instead of the Morse, which changes with every size.taper. But we are stuck with it now!

Now, what else can I grizzle about?

Howard.
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