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Method of joining for chuck key?

How would they have, how should I??

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Chris V28/05/2020 15:07:39
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222 forum posts
31 photos

Thanks Mick B1,

Yes all good & valid points, though the chucks I 'need' them for are drill chucks that will mostly be used in the tailstock.

Regarding wear, is SAE 660 bronze more difficult to turn than CZ121 brass? And is it generally a harder material, ie likely to dent less????

Chris.

Nick Clarke 328/05/2020 15:24:14
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779 forum posts
27 photos
Posted by Chris V on 28/05/2020 13:56:54:

Brilliant!

I had in my mind dismissed a brass cross pin as not strong enough but as several of you seem to think that would be ok I think that would be my preferred method. Of course a steel cross pin could look nice too, matching the top of the shaft, but clearly that's not how this particular example was made.

Should the cross pin also be tapered, I don't suppose you can buy imperial brass taper pins..or can you?

Chris.

Yes you can, but only in small sizes and with non standard tapers I suspect - clockmakers use them to hold clocks together.

eBay Brass Taper Pins

 

Regarding wear, is SAE 660 bronze more difficult to turn than CZ121 brass? And is it generally a harder material, ie likely to dent less????

It all depends what you want to dent with it devil

 

 

 

 

Edited By Nick Clarke 3 on 28/05/2020 15:25:45

Chris V28/05/2020 15:54:56
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222 forum posts
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Ah yes I had seen and wondered what clock makers tapered pins were, I think they use them to secure the pillars to the plates like an engineer might use a cotter pin, only more refined!

Mick B128/05/2020 15:57:53
1580 forum posts
84 photos
Posted by Chris V on 28/05/2020 15:07:39:

Thanks Mick B1,

Yes all good & valid points, though the chucks I 'need' them for are drill chucks that will mostly be used in the tailstock.

Regarding wear, is SAE 660 bronze more difficult to turn than CZ121 brass? And is it generally a harder material, ie likely to dent less????

Chris.

I don't really know it - it's a leaded bronze that's said to be free-machining and resistant to wear. I've machined a fair amount of phosphor bronze PB102, and that's much tougher than CZ121, with a continuous chip and darker, more coppery colour. You need more clearance for tapping and good lubrication.

Robert Atkinson 228/05/2020 16:38:35
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651 forum posts
16 photos

The X-ray suggestion was tounge in cheek. No metal will completely stop X-rays so thicker or denser metal just needs more exposure. But you rapidly get into unrealistic times. Dental X-ray generators are at least 70 kVp and the thickness of brass that will reduce the intensity of 70kVp by a half is only 0.01mm. 10 half value thicknesses is normally considered to reduce it to negligble levels so yes a dental machine is unlikely to do the trick but it depends obn the sensitivity of the sensor. Older dental X-ray units were lower energy 50-60kVp which on the face of it seems safer, but it isn't. The lower energy means longer exposure and the dermis absorbs more energy at the lower kVp. (its actually a spread of energy and on dental machines a aluminium disk is used to filter out the lower end of the spectrum.

Robert G8RPI.

Chris V28/05/2020 18:38:42
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222 forum posts
31 photos

Thanks Mick, Ok I will stick with brass, good to know phosphor bronze PB102 is the darker of the two bronzes though, and bronze being a fair bit more costly too.

Chris.

not done it yet28/05/2020 20:40:57
4662 forum posts
16 photos

Has anyone suggested it being shrink fitted?

Chris V28/05/2020 22:28:00
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222 forum posts
31 photos

Thank you, no, how would that be achieved then?

Cheers

Chris.

RobCox28/05/2020 22:42:05
28 forum posts
19 photos

Turn the hole to be smaller than the part it's to be mated with, at a ratio of about 1 thou per inch. Heat the female part with a gas torch (doesn't have to be red hot). Press together quickly! If the male part heats up before its fully driven home, game over!. The resulting fit is stronger that a press fit.

Gary Wooding29/05/2020 07:56:52
703 forum posts
183 photos

This is the way I'd do it.

chuck key.jpg

Chris V29/05/2020 09:05:34
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222 forum posts
31 photos

Thanks for the explanation Rob, Ive learnt a lot from this thread.

Yes Garry I like it, so for me its a toss up between cross pin or thread & rivet the end.

Do you think it likely the peened end would show when finished an irregular circle due to the thread?

Cheers

Chris.

not done it yet29/05/2020 09:55:07
4662 forum posts
16 photos

If the male part heats up before its fully driven home, game over!.

Not true where the coefficient of expansion of the outer is sufficiently greater than the inner, particularly where tapers are concerned.

Carbide cutters are fixed in position, with some systems, by shrink fitting - and easily removed after heating the holder sufficiently, at the end of the cutter’s life.

Gary Wooding29/05/2020 10:17:15
703 forum posts
183 photos

This method will prevent an irregular shaped circle.

chuck key2.jpg

Chris V30/05/2020 10:53:16
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222 forum posts
31 photos

Thanks Garry, yes that covers all bases for me. When you drew that did you made a side on drawing first?

Steel for the shaft?

GLR offer EN1A, EN8, EN24T & EN1A.

The square section that's to fit the chuck is to be 1/4". So the shaft maybe 3/8"-1/2" dia.

I have an Amolco Mill.

I'd rather not have to harden it, so reading up on it EN8 would be what i'm inclined to go for, but I really don't have enough experience to have a strong opinion, so any input most welcome!?

Regarding Loctite 270. Does this go off as quickly as the stuff bought in the local post office etc?

Cheers

Gary Wooding30/05/2020 14:11:17
703 forum posts
183 photos

Hi Chris,

Yes, I did a side-on drawing first.

I've made an extra key for my individual 4-jaw chuck (2 keys make it so much easier to centre work) and didn't bother to harden it. I've never seen anything to suggest that I made a mistake, though I'm sure many will say I'm wrong.

Chris V30/05/2020 14:22:09
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222 forum posts
31 photos

Thanks Gary, wish I had those drawing skills, if you had posted the side on image I'd have used it scaled as my pattern! (-:

Oh yes that's a thought Ive read about using two keys on a 4 jaw, Oh and presuming that's at least 4" dia that's way more torque than on my little drill chucks, so that's great to know,

Cheers

Chris.

Gary Wooding30/05/2020 15:38:25
703 forum posts
183 photos

Hi Chris,

Is this what you wanted?

chuck key3.jpg

Chris V30/05/2020 15:43:15
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222 forum posts
31 photos

(-: Yes! thanks so much!

Chris.

Mick B130/05/2020 16:30:37
1580 forum posts
84 photos

I think cross-pinning is better than threading and much better than shrink fitting.

There could be considerable torque on the joint, tightening and releasing the chuck. With shrink fitting you're dependent on interference friction, and with threading a tight releasing could throw much of the stress onto the peened countersink.

Still, if you get a problem it should be easy enough to cross pin it afterwards.

Michael Gilligan30/05/2020 17:11:17
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15768 forum posts
689 photos

I hadn’t contributed to this because I thought the big question was ‘how were the original parts secured?’

Now that we’re onto ‘how do I build something similar?’ the answer seems obvious :

Loctite 638 or similar

... and yes, I am confident that [properly used] it would take the torque.

MichaelG.

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