Oracle Delphi mk1 Quick Restoration

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Ant
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#91 Re: Oracle Delphi mk1 Quick Restoration

Post by Ant »

For reference for anyone bothered, this is the dial gauge setup, it can be fitted to the mill or the lathe using a simple machined bracket. The compound slide on the lathe is rarely used so I took it off and fitted a decent tool post and used its mounting bolt holes to fit the dial gauge. the gauge bears against a stack of magnets when in use, just a short stack on the lathe and a taller stack using the finger gauge magnetic base when used on the mill. doesn't give a lot of travel, but its just for doing small stuff. the dials on the mill are weird divisions so I tend to get close then use this setup to do the final bits

Image20240512_124319 by anthony cresswell, on Flickr
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Ant
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#92 Re: Oracle Delphi mk1 Quick Restoration

Post by Ant »

Decided to put it on, it just fits. The mounting screw is hard up against the front of the slot so its marginal, there isn't any wiggle room at all. Really the slot needs to be about a mil longer

ImageCx unipivot offset cart carrier plate by anthony cresswell, on Flickr

I cant be bothered to correct it today, its too hot and I'm not in the right mindset, wouldn't do to cock it up :shock:
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Morgan Jones
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#93 Re: Oracle Delphi mk1 Quick Restoration

Post by Morgan Jones »

I like your dial gauge set up on the Hobbymat. I've done similar to you and rarely have the top slide fitted, allowing a more substantial (and quick change) tool post. Looking at your setup on the mill, you ideally want an "elephant's foot" (5mm diameter flat face, made by machining most of the head off an M2.5 socket head screw) on your dial gauge when the tip touches a curved surface. As a general rule, you want one curve only, so an elephant's foot is for centring round stuff in lathes etc, whereas the supplied ball tip is better when you need to centre square stock in a four-jaw chuck in the lathe. What you do not want to do is to casually flick the tip across the garage never to be seen again. (I am still very annoyed that a couple of weeks ago I lost the ball tip of my Mercer dial gauge bought in 1982.)

Going back to the "head shell", it all looks very promising. I've found that metal finger lifts tend to "ting" (although your copper one might have better self-damping) so I cover mine with heatshrink sleeving for damping - which I see you've also done. Also stops the 1/16" silver steel on mine from rusting. However... I have a better solution that will be used on the next arm. Cocktail sticks aren't as round as they might be, but you can buy 2 and 3mm round hardwood, pop that in the lathe (collet chuck) and machine it using a very sharp tool (such as a fresh carbide tip intended for aluminium). Smooth with silicon carbide paper, a lick of varnish and you have something much lighter that rings far less and looks nice. Just a thought. Of course, you can't easily shape it as you did with your copper.

By the way, an alternative way to have finished the top face could have been to face it in the lathe. Yes, I know it's thin, so you take the jaws out of the chuck and stick the work to it with double-sided tape. You'd be amazed how strong the bond can be. Surprisingly, you have to be careful not to use too much tape, or it can be difficult to remove. I stuck a 9" disc to face plate of larger lathe and machined it. I used four 2" strips of tape and it took a lot of force the get the work off!
Ant
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#94 Re: Oracle Delphi mk1 Quick Restoration

Post by Ant »

Ill have to remember that trick, although it might not have worked too well with this one because the centre bore on the 4 jaw i have on it at the moment is 22mm so not a lot to stick the part to. However grabbing a disc or something in the chuck jaws and using that would solve that.
I have superglued small parts to the end of a mandrel before and that worked well enough
Ill have a look in the box for the gauge, im sure it came with some other ends for the finger. Tbh id never thought about it, learn something new in machining practice every time you doit and/or discuss it with others!

I find using the mill and lathe theraputic, dont know why, just like to see something that fell out of my head made real. The massive faff to be gone through to make a simple thing as perfectly as you can appeals for some reason

Playing some stuff with the modified arm, there appears to be a subtle difference compared to how it was, for want of a better description, it sounds 'tidier' than it did.
cant point to what has caused it, the alignment being better than it was, because it is, it dropped straight in bang on with very minimal faffing which was nice, and a good job because there is no further adjustment available. Possibly the extra little bit of mass over the cart, the fact that ive been able to wind the right hand bob weight in closer to the pivot as the mass is offset at the cart end, a slight change to the moi as the counterweight is a little further out, there are loads of possible factors as to why.

Ill take it
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Morgan Jones
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#95 Re: Oracle Delphi mk1 Quick Restoration

Post by Morgan Jones »

Ant wrote: Sun May 12, 2024 8:53 pm I find using the mill and lathe theraputic, don't know why, just like to see something that fell out of my head made real. The massive faff to be gone through to make a simple thing as perfectly as you can appeals for some reason.
Likewise. Making precision swarf makes all worries fall away. Very calming.

Glad to hear it was worthwhile.
Morgan Jones
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#96 Re: Oracle Delphi mk1 Quick Restoration

Post by Morgan Jones »

I was making some swarf and just had a little thought about your cartridge carrier. There is room (just) to put an arced slot in the carrier behind the cartridge screws. That slot could be rebated underneath to take either the hex head of a screw or a nut. Ideally, you'd do a job like that on a turntable, but you probably don't have one. However... You know that your arm is designed to have a specific offset angle, and you don't need a huge amount of adjustment, so a short straight slot and rebate would probably do just fine. You can even mark through as the cartridge is presently set. The point of the exercise? Your carrier is now firmly anchored to the arm.

Today's swarf is making a jig for measuring the distance between cartridge mounting centres and stylus tip. I machined a couple of 2.68mm diameter pins from 1/8" silver steel, drilled and tapped them M2 and these will screw to a plate (1/2" apart) for the cartridge to locate on. The far ends have been machined to cones to make finding the centres easy (first time I've put the top slide back on the Hobbymat in four years!) Plate will have a pair of bosses to engage with slots on XY table under microscope. Plate can then be clamped and X and Y twirled whilst noting readings as bits pass the cross-hairs in the eyepiece.
Ant
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#97 Re: Oracle Delphi mk1 Quick Restoration

Post by Ant »

I could do that easily enough, i have a couple of rotary tables. The little teeny proxxon one should be just the job. The carrier is 4mm thick so should have enough meat on it to rebate it underneath for a retaining nut. If i needed to i could either superglue a nut to a bit of stud so i could skim a bit off to thin one down, or use a second jam nut too i suppose

Plenty of ways and means

The weight reduction from taking the material out of the carrier should be made back up by the second nut and bolt so it should end up about the same

Im not entirely happy with it as is, i need to extend the slot in the stub so there is some meaningful adjustment, so its coming off anyway. I am not looking forward to trying to remachine it because i really dont want to have to dismantle it again if i dont have to. Wether ill get around to it this weekend is another matter
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Ant
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#98 Re: Oracle Delphi mk1 Quick Restoration

Post by Ant »

I did pretty much the same to measure the at cart, ground a point on a couple of cart bolts and put them in the mounting slots facing the bottom so i could get a reasonably accurate centre to measure from.
I just bolted the cart onto a bit of 3mm acrylic using the pointy bolts and used a minature square lined up with the stylus to measure from.

Quite a bit more heath robinson and not remotely as accurate as your method. And quite a bit more risky in terms of potential cart damage.... at least i managed not to break it
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Morgan Jones
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#99 Re: Oracle Delphi mk1 Quick Restoration

Post by Morgan Jones »

Wow; a choice of rotary tables! Yes, if you use a hex head nut, You will have plenty of meat in your carrier for head. And a skim off the head to remove the proud lettering will help.

Is it really essential to remachine the stub? I suppose you know for certain, but I can understand your hesitancy.

I was a little bit more fancy with my cartridge jig and used the mill's XY table to get accurate 1/2" centres. Cartridge slid on tightly and I was able to align it on the microscope's XY table. Except... I have discovered that the microscope does not move up and down squarely (focus). When I adjust to move the focal plane from the tips of the pointy pegs to the stylus tip, it moves to one side. It just so happens that the microscope moves up and down a 25mm diameter column, just like my tapping fixture (jig for tapping holes accurately without breaking expensive taps). So I could put the microscope on the tapping fixture's column. I've measured the errors on the tapping fixture and it's 0.2 degree off from side to side and 0.06 degree off front to back. Perfectly good enough for tapping. I haven't yet worked out whether that's better than the microscope's column. This will be investigated tomorrow...

By the way, I bought some carbon fibre vernier callipers (Calimax) specifically for measuring moving coil cartridges before I thought of doing it optically. The scope for expensive damage is considerable.
Ant
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#100 Re: Oracle Delphi mk1 Quick Restoration

Post by Ant »

I got the proxxon one for the mf70 i used to have and kept it when i sold the 70, the other one is a 4 inch soba with a 4 jaw bolted to an adapter plate so i can use it as a reasonably accurate dividing head without having to shell out for an accurate dividing head
For my acheivable accuracy its pretty good for the money
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