Thread: Mini screw chuck

Nice work F&E.

So what's the burl going to end up as? Something to ream the ear out? ;-}

Have heard of VCR bits used for mounts too.

Definitely nice work!
How'd you get the dovetail for the jaws to grip, in the aluminum? Was the groove turned and then you faced the aluminum to run true? I'm just dense enough to need instructions. I have an old computer I'm going to dig the drive out of.
Ern, I have two that I made from an old VCR. I use them as sticky chucks. One grips in expansion and one in contraction mode. They work well. I turned the grooves, then remounted them and faced the front surfaces.

What a clever idea F&E. Well done that man

Hmmm; fridge magnets, mobiles, wind chimes, now chucks.

Thanks guys. I am not "that" smart, though: it did not occur to me that the dovetail could be a problem: I just put the disc down flat and expected it to self center. The groove was already there, I did not use it to engage the jaws. The pic is the small knob that came out. Don't know if it will be good for anything yet, it was just for the exercise.

Your advice is taken on board, if I notice any problem that needs addressing I will certainly report it for discussion.

Proof positive that good luck always beats good management: without me realising it, the existing groove perfectly engages the jaws! (Supernova 2 standard set) On the other hand, does this (as in sketch A) provide a better mounting than the way I did it (sketch B)? I am not sure.

I don't want to be rude, this is a genuine question:

If you need to put the timber bit in, why bother with the aluminium? I always use a timber "plug" with a screw in it the same way you have shown, I just wonder what the advantage is?

Cheers.

P

Originally Posted by bitingmidge

I don't want to be rude, this is a genuine question:

If you need to put the timber bit in, why bother with the aluminium? I always use a timber "plug" with a screw in it the same way you have shown, I just wonder what the advantage is?

Cheers.

P

Yep, totally agree, I asked myself the same question. I could come up with only two advantages: more durable and more precise centering of the screw, because the pilot hole, that you can assume precise to the micron, is already there.

Here it is. Selected a self-tapping screw of appropriate length with a wide worm. Drilled the centre of the aluminium disk to the diametre of the screw shaft. Turned and drilled a disc of MDF as a buffer to avoid hitting the metal with the tool. Slowly threaded the screw through the aluminium disc so that it made its own groove.

Good innovation!

Dont need one at the moment, but have stored it away for another day.

F&E, figure A would be my way of mounting it. The dovetail on the 50mm jaws is the "true" spot, according to all I've read. The instructions always say "don't make the turned spigot long enough to butt against the bottom plate of the jaws" - or something to that effect. However, if it centered perfectly the other way, who's to say which will be better? Maybe the aluminum disk is precision made throughout... which a wooden spigot may not be as precision.
Good on ya.

Thanks Al, I'll keep this in mind. The instructions of the Supernova do not mention that a spigot should not touch the base of the chuck: should they? They do mention that in expansion mode the piece must "be seated properly on the bottom face of the jaws" to run true, which makes sense. I applied the same principle in a "compression" mode, but maybe it is wrong in this situation. To be honest, I shaped the little knob with a rasp and sandpaper (I still haven't received the #$%^ tool rest, it's almost three months now!), so it is not perfectly round, can't really tell whether the centering was perfect... Must try it again both ways to make sure.

A wooden spigot often isn't truly squared on the end, so it won't seat squarely in the chuck if bottomed out in the jaws as in method A. On the other hand, method A will hold out-of-balance pieces more securely than method B, as the metal disk doesn't have a significant shoulder to butt the ends of the jaws against.

Personally, I'd go for method B 'cos A could still be thrown out of square by a small bit of sawdust, wood-chip or even a loose jaw screw at the base of the jaw, and it's a mini-chuck after all, so the lack of a shoulder is of less importance.

ie. I'd take the small risk of it going UFO in order to make sure it seats square in the chuck in the first place. But that's just me.

Thanks Skew. I think I understand your explanation but, if I do, it means that you have inverted the reference to A and B. (Otherwise, I am lost!)

Hi

....BUT! Can't you already buy screw type centres that fit directly into the lathe spindle? Thus avoiding the Chuck > Aluminium > MDF > turned item?

Originally Posted by MrFixIt

Hi

....BUT! Can't you already buy screw type centres that fit directly into the lathe spindle? Thus avoiding the Chuck > Aluminium > MDF > turned item?

BUT! What's the fun in that?