Valve Base

[Darren]

TBH honest John the trepanning came out neater than either the hole saw or simple drilling. I guess it was too low a speed for the drill bit and I gave it very little support.

But the hole saw, though quick was a bit messy on the paintwork. Dragged the swaf around a bit I guess.

Not to worry, it will all be hidden in the end and I'm pleased with the result. Great when I was considering buying a new tool and made do with what I had.

As ever, thanks guys you lot are a real bonus.... 

[Bernd]

Looks good Darren.

I guess I'm going to have to find those pics of me doing a 1/4" thick aluminum plate. I put a 14.25" dia hole in it with a home made tree panning tool. I'll have to put up a thread in the tool area about it. Don't want to hijack this thread.

Bernd

[Rog02]

A couple of suggestions on using a hole saw.  For a neat clean hole without destroying the painted surface start the hole saw from the painted side but stop just after the teeth of the saw mark a full circle.  Withdraw the saw and re-insert the pilot bit from the reverse side and proceed to cut the hole.  The result will be a clean hole on both sides without the normal "tear out" and the swarf will not be harming the surface.  This tip is especially useful when hole sawing wood.

When cutting a hole in a thick piece of material again pierce the material with the pilot drill and cut just enough to mark the perimeter of the saws kerf.  Once the kerf is clearly defined stop the saw and withdraw it from the work.  Drill a "chip relief hole" just inside the outer kerf mark.  Make the relief hole so that its circumference is tangent to the outer edge of the kerf mark.  The idea is to give the swarf an exit when sawing through rather than filling the tooth gullets and plugging the saw.

Also be sure to use plenty of lube/coolant that is appropriate for the type of metal being cut.

I hope the sketch makes sense.  Using the drawing function in a word processor is rather limited.

[Darren]

Nice tips there Roger, I have another to do yet, and prob more after and will take note of what you said, ta....

Onward we march....

Now we have the holes cut in the chassis it's time to mount the valve bases/holders. I need to make some fixtures and incorporate a method of electrical isolation from the valve pins and the chassis itself. These two pins carry the voltage for the valve heater. In this case 10V @ 10A. Nothing too scary here even if it is a tad power hungry at 100VA.

1VA = 1V @ 1A = 1W, so these valves (ok, tubes for you guys over there) consume 100W each just for their heaters and there are two of them to make stereo reproduction.
Quite and expensive amp to run this one, but oh the sound...

Anyways, I took a 30mm SS 303 bar and drilled a 6mm hole through the center



Parted them off and made four pieces, note outer dia not turned to size as yet. That comes later.
You may also note in the picture a collet stop ready to be fitted to the collet also shown. I wanted to make these four pieces identical in length and a collet stop is perfect for this. It allows each piece to be fitted into the collet at identical depths. But,it also serves another purpose.
Because each piece is so short it would be very difficult to clamp them in the collect squarely. In fact it would be almost impossible. Having the stop to push them up against solves this problem.



Here you can see the stop fitted. The depth is set by the thread on the bar and a locknut.



First piece faced off. By zeroing the topslide on the lathe and with the use of the collet stop we can make all four the exact same length.





Now they were turned around, again against the stop and chamfered



All four done



Now I needed to make the electrical isolators. For this I chose to use a bar of Teflon. I got part way through and realised that white teflon picked up dirt like a magnet picks up steel swarf 
Not good, in the final application appearance is everything and dirty white bits just won't do.....



So, I junked that idea, thinking I've learnt something new tonight at least. Save the Teflon for another use later.
Swapped the Teflon out for a bar of Acetal, or Delrin if you prefer.



A bit of jigery pokery and a little while later we have these, some top hat isolators and some washers.



Now I needed to true them all up to the same diameter. Slipped them onto a 6mm allthread and clamped with a nut.



Well that didn't work did it. I suspected it wouldn't, not enough support and too much vibration=chatter = a rough finish.
Well, I was turning 30mm held in a 6mm threaded bar after all.
So I shortened them down and did half at a time. But I still needed to steady the end with a tailstock center. But alas I don't have one for this lathe. I do for the mini lathe but it's not here.
I came up with this. Centered the allthread and used an old center punch held in the tailstock chuck. Crude, but it worked quite well. Scuse the rust, it got left outside at some time.



Well that worked just fine, here is a pic of the washers underneath. The electrical connections will also fix here with a lug.



And the top, all neat and tidy





All in all it's going quite well so far and progressed another stage.

Darren

[Brass_Machine]

Watching this one.

So Darren... when you are done, can you help those of us who want to build a valve amp do so? I would like to tackle one perhaps next fall. I am sure with smaller valves though. Would need help in selecting the right stuff and the electric schematics.

Eric

 

[sbwhart]

Nice one Darren

Your making a nice neat Job of it:- love the improviced centre. 

Shows good use of collets and collet stop, been trying to identify lathe, what bread is it ?.

Have
 
Fun

Stew

[bogstandard]

Darren,

Nice improvisation yet again, use what you've got to get the job done.

One of my collet stops is the same as yours, and I found a problem when using small collets. The threaded rod won't come far enough forwards to act as a stop.

I drilled and tapped both ends of the main threaded rod 3mm, so a long 3mm bolt with the head cut off and fitted into the end can reach up those small collets. You can make all sorts of little stops just by reshaping the bolt heads and screwing into the end.

John

[Darren]

Eric,

No probs, should you want to build a "tube" amp I'm sure I can help. I'm no expert though, but seemed to have managed to have built 20 or so amps to date.
SETs are my flavour, as opposed to PP.

Stew,
Yep, when I was looking for a lathe I just knew I wanted collet facility. Not regretted it for a moment, the chuck gets rarely used on this lathe. It has a "proper" collet lever assembly and is really fast to use when changing parts.

It's a Smart and Brown Model L Capstan Lathe http://www.lathes.co.uk/smartbrown/page2.html

I have a 6 tool possition sliding turret, a double action cut-off slide, a normal compound slide and a normal tailstock. Unusual for this model is a 5c collet nose, most used a smaller Smart & brown collet that is hard to find. Also the spindle is fully hardened and runs on roller bearings as opposed to plain bearings. It's 3ph with a 2 speed motor and I use a rotary converter to get my 3ph supply.
The whole thing sits on a ridiculously heavy cast iron cabinet which behaves as one unit with the lathe.

All in all it's a superb machine, but lacks feeds and screw facilities as it's a "plain" lathe.
Really used for large volume production work before CNC came along.

John,

Yes I can see the limitation there. I was going to make a larger dia end plug for the stop as I thought it was too small to hold small lengths squarely.
This turned out to be not so and it is fine as is. Held those small parts perfectly square with no effort on my part.

I really do like using collets I have to say.

Darren

[sbwhart]

Hi Darren

I recognise your lathe now we use to have some where I work, them and symilar Swiss make:- Saublin, we must have had 30+ all gone now. Very good machines, we use to run them at high speeds making small brass components, depending on what we were doing, they were set up with a capstan head or cross slide etc we had a full kit of attachements. We had women operating them, they were very skilled, and had a great light tuch, they could adjust size just by varying the pressure they aplied, and repeat it time after time. 

Cheers

Stew

[Darren]

Yes the 3,000 rpm is nice for doing brass, esp without auto feed.

Darren

[Brass_Machine]

Eric,

No probs, should you want to build a "tube" amp I'm sure I can help. I'm no expert though, but seemed to have managed to have built 20 or so amps to date.
SETs are my flavour, as opposed to PP.
....

Darren

Valves... Tubes... I work with 2 Brits who are determined to teach me 'proper' English!   

Eric

[bogstandard]

Eric,

I work with 2 Brits who are determined to teach me 'proper' English

You only think you work with them, they are the initial infiltration, preparing you for when we make our comeback, and turn you into a colony again.

Bogs

[Darren]

Shhh, we've almost got them under control John.....see, we got them to set up this site for us and it was done willingly to boot.

Like I said, almost there 

[Brass_Machine]

Eric,

I work with 2 Brits who are determined to teach me 'proper' English

You only think you work with them, they are the initial infiltration, preparing you for when we make our comeback, and turn you into a colony again.

Bogs

If you can fix the economy, you are more than welcome to it.     

Eric

[Darren]

Right you lot, back to the topic   

I need to make some sort of connector for the top to pins of the valve. One pin is at a very low voltage (the Grid) and the other is at a very lethal high voltage.
Lethal as in you'd only get the one chance to touch it cos you won't be around for a second go...!!

So obviously whatever is made for this pin needs good insulation. I was thinking of using some of that Teflon that made an appearance earlier.

At the mo, the following may or may not be the final choice. I'll press on with it and see how it goes.
Suggestions are more than welcome.

Taking a 15mm copper water pipe and sizing it up to the pin in question.



Cleaned it up on the lathe and tapered the end internally.



Onto the miller held in a hexagon collet fixture in order to make three slits at 120deg.



Starting to make the first cut and it's cutting really smoothly.



All three cuts now done



Then turned a bar on the lathe to the same dia of the valve pin to open out the end of the slitted tube. This was to prevent too much force on the valve itself.



Well that's where I'm at and I'm not quite sure where I'm going with this. It's the fact that it needs insulating that adds complications, otherwise it would be a simple matter to make some sort of clamp.
Design in progress......

[rleete]

Just a suggestion:  Those look like minature car battery terminals, so why not a battery cable clamp in miniature?  Then, make a cover/cap out of the teflon (or other insulator) and hide it all.

[Darren]

The valve pin is 14.4mm dia or more prob 9/16

I think I may be trying too hard here, a clamp would be better than something with a push fit ,if only for safety reasons.
I'm having trouble getting my head around the insulating bit.

I will think some more on it, please keep any suggestions coming chaps.....

[rleete]

Well, it originally connected to something.  Do you have any piccs or sketches of that?  Is it possible to replicate?

I like the idea you started with, but maybe modified a bit.  I'll PM you a quick .jpg of a part I whipped up.   Top is threaded, so you can use nuts and washers to sandwich a wire or ring terminal.  Feel free to post or use at your discretion.


Edit, nevermind, I'll find a host and post the pic.  Give me a minute.

Edit again, my spellink stinks!

[rleete]

Something like this?  Sorta what you have, but without the taper on the inside, and a sliding fit.  Adjust to make good connection by squeezing the prongs together.  Maybe use some contact grease or Artic Silver (stuff to give good contact on computer CPU heat sinks)?

[Darren]

OK that is something similar to what would have been used originally,

I'll see if I can sort a pic, depends if I can find sumut in the den 

[Darren]

This is what would have been used, though this one is much smaller it's the same design





Apart from the fact they are no longer avail, and I've yet to see any pop up on Ebay in the last 3yrs, you could say they are a bit difficult to find.

[rleete]

Looks like I just reinvented the wheel, then.  I'm assuming the outer profile of the insulator doesn't matter, just whatever appeals to you.  You ought to be able to machine that up, and so the looks of the connector part aren't so important, just the function.

[bogstandard]

Darren,

Might be a stupid idea, but could you use terry clips.

C-o-C attached

The heat resistant insulation might be the problem.

John

[HS93]

How about a Plug cap (mini spark plug) cut down if need be and the internals of one of the ceramic caps.

peter

[Darren]

Thanks Guys I'm working on something this evening, not ready to show just yet though.

John,
I've seen those clips on the market stall and did give them some consideration.

I have to think about safety foremost but almost as important is the finished looks.
Apart from that I'd like to make something myself, after all, it what we have these tools for init