Valve Base

[Darren]

As promised here is a picture of the valve that I'm designing a base for. In the picture you can see some bases and top caps that I made over a year ago.

I decided that for the final build of my amplifier I need something with a more "engineered" look as well as function.

More pic's coming soon, this is just a teaser.......  ;D

[Bernd]

Nice Darren.

 Now I've familar with tubes, but you got me on this one. What does it do or supposed to do?  ???

By the way. Welcome to Madmodder.

regards,
Bernd

[Darren]

It does this



Part of my music hobby...this is a test build just to get the circuit right. It worked so well it stayed like this for almost a year, then I moved.
That was over a year ago and what with renovations etc I'm only just opening up the boxes again.

[Brass_Machine]

Wow Darren. I am impressed! That is definitely one of the styles I like. Care to elaborate more on this? I would love to learn some audio stuff.

Eric

[Darren]

Hi guys,

Well to go into it deeply would be a whole new subject, simply I build valve amps for stereo hifi reproduction. Been doing it a while and this valve is one of the "Big Boys"

It's an 833 triode, operating voltage in this picture is 1,100 Volts DC, DC is far more dangerous than AC btw. It produces a glorious sound that has to be heard to appreciate fully.



Ok, so what have I been doing in respect to this, and what does it have to do with forum. Well as I said earlier I've been making some new bases for the valve. It needs something to make it stand up and somewhere to connect the cables to.
I found this forum after I'd started so the pics are a little jumbled. I'll put some info up bit by bit as I sort some photo's and all will be revealed slowly.

Everything in this mini-project is machined from a 20mm 303 stainless bar.

The thumbscrews------------In this pic I'm putting a chamfer on, initially I mounted these on a 6mm thread held in the lathe collet. But it didn't go too well as the thread wasn't quite central. I think this is just the way it goes with threading. So here I'm doing it again but holding the part on a shoulder instead. Worked perfectly.
You can see another on the spindle nose to get a better idea.

[Darren]

The Pillar.........

In the background is a prototype that I'm making more of in the lathe. I'm making them back to back as this makes holding them easier and there is little waste this way.



Here you can see I'm marking the bars with the cutoff tool. In the collet is a collet depth stop. This enables me to mark the bar, change the workpiece and mark another bar in exactly the same place. Makes my life easier as I had four to do and two marks on each end making eight marks altogether.




Here you can see a length of 20mm SS bar in the milling machine. I'm using a center finder that arived in the post only yesterday, so first time out with this one.
It's so simple yet it works very well.

[Darren]

Now I need to put some flats on the ends of those two bars. I could do this in the mill, but, my mill is not so clever and I can't hold the cutters that I have left in it !!

No matter we can use the lathe instead.

Here you can see several things going on, the 1" cutter is being centered in the 4 jaw chuck with a dial gauge, the workpiece is being held in a tool holder that just happened to be the right size. To the right of the tool holder you should just be able to make out a square...



Having marked the bars previously with the parting off too gave me a clear indication of where to mill to.



And now for the other side, squaring it up with, well urm a square....



Almost done



There, that's that job done



Darren

[Divided he ad]

Hi Darren,

Well I like what your doing even if I haven't a clue about these valve thingys   ???

I've heard of valves and even seen old footage of them in various things.... Well pre-birth date! So I'll see if I can't pick up a little knowledge along the way  ;D

I'm going to have to e blag some stuff in order to get the together to purchase an E36 collet set for my mill and a 5c collet set and chuck for my lathe.... It's no good I just really think these items will make my machining more interesting and occasionally less frustrating! (Tool variants do my nut in... I have some metric and some imperial and can't hold all with the MT3 collets that I have!)

I do like that centre finder do-dad I've seen them advertised etc but never knew that was their use.... Never really investigated though either!


To finish my little blathering... I'll just say this. I'm glad your posting and look forward to seeing what you make and learning a little on the way 




Ralph.

[Darren]

Ralph, blather away by all means. It can be a lonely hobby otherwise...

TBH it's nice to be able to share, I've done very little of this sort of stuff but do enjoy it. No idea if I'm doing it right or wrong ??? Like I said before I'm learning as I'm going along.
If you have any tips please fire away.

I used the 4 Jaw cos I didn't have a 1" collet, milled at approx 460RPM and I've been turning the bars at 1800 RPM. That seems to be the sweat spot.

For the life of me I can't get a good finish on steel, Stainless is great. Turn it and it's done, OK maybe a quick run over with a Scotchpad and it looks really nice.

Brass of course is easy, I tend to turn that at 3000RPM with high feed speeds too.

Plastic is cheap and nice to use, esp for prototypes.....

If you can afford it you should seriously consider a collet set-up. They are a dream to use compared to a chuck for smaller items. The runout is almost non existent, even if you take the work out, rotate it and put it back

Darren

[Darren]

OK for those interested a little tutorial for you.... ;D

The valve I'm making the bases for is what's known as a triode (as in three elements) Simply it's an amplifying device that amplifies the flow of voltage/current which is the flow of electrons. (electricity, voltage=pressure/current=flow)



We have a heater which we typically connect to a low voltage of around 6.3V, though this can vary from valve to valve. This heats the cathode which is sitting at a negative DC voltage potential. The anode is sitting at the positive DC potential. (voltage potential typically 250-500V DC)

Point to note, electrons move from negative to positive and not the other way around as most people believe. This is important.

Our heater heats up the cathode, this makes the electrons become a little excited and thus easier to leave the cathode. Some will hover around and just off the cathode, this is called the "space charge"

Now, opposites attract, and equals repel, remember that girl from school?

Electrons are no different, they want to flow across the vacuum inside the glass envelope and hurtle towards the positive anode, bit like us young men on our first date ;D 

We need to control these electrons into some sort of order, Slow them down a bit if you like.
We do this by applying a negative low voltage on the grid, typically 60-100 volts, but can be as low as 1 or 2 volts. If we increase the negative voltage (more negative) the flow of electrons will slow from the cathode to the anode (equals repel), if we make the grid more positive more electrons will flow.

So there we have it, we have a low voltage controlling a much larger voltage,

Now imagine that the low voltage is coming from your CD player output.......music modulates, so we have a negative voltage modulating the grid of the valve which in turn modulates the higher voltage flow and thus amplifies a low signal into a much larger one.


I hope you can follow that? It sounds complicated, but it's really very simple 

Darren

[Bernd]

And then came the transistor!  ;D

I should have know what you were talking about Darren. A long time ago I took a home course on electronics. It started out with the triode tube and advanced to the transistor. I now know what you are doing.

Bernd

[Darren]

Transistors, is swearing allowed on here  ;D

OK, they are good for general circuitry, better than valves......but, for music they just so harsh, give me a valve any day  ;D

Ok not much done today on these bases, but here's a pic all the same.



 

[Bernd]

Transistors, is swearing allowed on here  ;D

Sorry about that Darren.  :-[  Didn'y know I was swearing.    ;D

Yes, so I've heard that the tubes make a better amplifier for music for the true audiophile. 

Bernd

[Darren]

Oh I'll prob be doing some "technical" swearing myself as time goes by....

Be sure to correct me too Bernd  ;D

[bogstandard]

Hi Darren,

Seeing as it isn't your first hobby, you are doing great on what you have done already.

If these bits are going on public view when working, I would suggest you have a few lessons from Ralph, he can get plain bits of metal looking like works of art, and would compliment your artwork with glass.

So going by your replies to Bernd, 'a pile of dog transistors' is swearing?

Nice terminology.......... 'Holy transistors!'.

Yep, that could be put to good use in the right context. Well, that gets around the swearing rule on this site, now what's next? Capacitors?, thyristors sounds good, or maybe a little bit of resistance now and again.

All in fun BTW.

John

[Darren]

That looks good Dave, a lot of people really favor these Boxfords from what I can tell.

Alas I have an ambitious project in mind for the future in that I wish to turn a new 12" or even 13" platter for my record player.
On those lines I'm thinking a Colchester Student for example, I also wish to turn 30mm S bars up to around 300 or 400mm long and drill and tap the ends.
I can do the last bit on my S&B if the new lathe isn't able.

I know from experience, that I want the next lathe purchase to be my last, famous last words.


Thanks John, I will speak to Ralph hopefully face to face sometime. I have been playing with metal for a long time.
It's the machining/engineering that's new to me...loving it though.

Did you see the link to my now very old web site? http://homepage.ntlworld.com/darren.dean/index.htm

[Darren]

"House work" today was clearing ground at the top of a high and very steep ground against a wall for preparation to planting a hedge. 100 Copper beach in this case.
Is that modding?


Ok, so taking a break from that this evening I thought that it was about time I got back to my amplifier build.
Tonight I laid out the various pieces on top of a chassis box.



At the back is the output transformer. Upside down in this instance. This connects the circuit to the speakers. One speaker in this case as these chassis are built as a pair in the form of two mono blocks for stereo reproduction.
At the front is the valve secured by the parts I've been working on in previous posts.
The orange wire is just stopping the valve from falling over. These fittings will be secured with a 6mm bolt from underneath. They will need electrically isolating from the chassis so I'm thinking of making "top hats" to facilitate the insulation. They will be subjected to some high temperatures, enough to singe wood so the top hats will be fabricated from Teflon rod as seen in the pictures.

A closer view



And one from the side showing more detail.



Transformer the right way up



Now then, I need to cut a hole in the chassis for the transformer connecting wires. I have a hole punch as shown in this picture, but it's a little small. I need to be careful here as the highest voltage is 1,200 volts DC. So a clearance gap from the connection to the chassis needs to be large enough for the voltage not to be able to jump the across. The hole punch is 50mm and I need a min of 55mm. 60mm would be better and tidier.
The chassis is 1.25mm thick steel and is hard work for a hole punch which can cause distortion, otherwise I would make one the correct size.



So I'm thinking of purchasing a Bi-metal hole saw of the correct size required.

But maybe someone here can suggest another way? I'd like the result to be tidy, spose that goes without saying.

[Bernd]

Have you ever heard of a "tree panning" tool? I think that's the American name for it. It's used to cut out holes in wood if the hole is bigger than the biggest drill you can get and also to make wooded wheels.

I know I've got several. I'll go look and update this post when I find them.

Bernd

[Darren]

Do you mean something like this Bernd?

http://cgi.ebay.co.uk/1-New-Hole-Saw-Kit-Adjustable-Metal-2-pc-Circle-Cutter_W0QQitemZ190275185971QQcmdZViewItemQQptZUK_Home_Garden_PowerTools_SM?hash=item190275185971&_trksid=p3286.c0.m14&_trkparms=66%3A3|65%3A7|39%3A1|240%3A1318

Cheap enough, but are they ok with steel, those blades look like they would snap at the slightest provocation.

Saved a pic for future ref when the auction has long gone !!

[bogstandard]

Darren,

I have some of those hole punches up to about 3", but as you say, at the thickness you are working with, they are very hard work. RS do a range of all sorts of sizes and shapes, but are rather expensive.

The hole saw method would be favourite, but stick with a good quality one if drilling thru steel, the cheaper ones have a tendancy to go blunt rather quickly. The Starrett range, to me, are the better end of the bunch for general steel drilling work.
But you will need to make sure you have a very rigid setup for the plate holding as they can be rather fierce on start up and break through.

The trepanning tool will work, but you have to take it v-e-r-y steady, and use only a fine feed down handle, a normal drill press handle will be putting you in the 'trouble area', and could easily break the tip off or rip the cut off centre, especially as you are breaking through. That system is very flexible for sizing, but a bad 'not very rigid' design.
You could easily make a more rigid trepanning system yourself, if you were doing a fair amount of the same size. Base it around a flycutter design but rather than an angled base, have it flat on the bottom with a rigidly fixed robust cutter in a fixed position for the job.

John

[sbwhart]

Hi Darren

Another way to open the hole out would be to mount it on a face plate up against a sacrifical plate and just bore it out, the technique has been shown elsware on MODMODDER I think it was Bernd who posted it, but I stand to be corrected on this.

Have Fun
 
Stew

[Bernd]

Darren,

Yes, that is what I was thinking about. I said for cutting wood because it would give an idea of approximatley what I was suggesting. Bog's has elaborated further on this.

Stew has another idea which I think would work if it is possible to mount the plate on a faceplate. Yes Stew I believe I've mentioned that some were on Madmodder.

The last thing I would resort to is the chain drilling method. Punch out the center part, file the sharp edges and then if you have a mill, use a boring tool to bore to size. Ofcourse if you have many parts to do then this would be a pain in the you know were.

Just some different ways to get the job done. I guess it will depend on what tooling you have at your disposal.

Bernd

[Rog02]

The trepanning tool Bog shows is basically the same as I use to cut inspection holes in aircraft panels.  I think mine is a General Tool which is a pretty decent quality tool and if I remember correctly I think it set me back about $15 USD.  I turn it either by a cordless drill or with an old fashioned wood brace and as others have stated, it requires a steady hand when free handing a hole.  I also have used it to cut instrument holes in a panel blank that could be placed in a drill press.  That works much easier!  Turn the tool slow and have the material well clamped as the cutter can and will try to dig in.  A slow feed is required with enough back force to prevent the digging in.

A Google search turned up a lot of high dollar versions for mills, but for the infrequent use this tool will normally see those are way overkill.

The other alternative, if you have a boring head for your mill, would be to make an offset bit for that and use it to cut the hole. 

[Darren]

Thanks for the tips guys, after reading all the suggestions I had a dig around of what I had that may do the job. But first a picture to show some scale of the project.
As you can see, mounting on the faceplate may have been a tad difficult in this case.



So digging out some candidate tooling from the lathe I gathered these. They are turret tooling for the Smart and Brown lathe.
The two outer ones didn't have enough adjustment to go to 60mm. But the center one though not having fine adjustment looked promising.



I am of course holding the tool bit in the wrong direction for lathe work, but should work as a trepanning tool on the mill. My only reservation was the fact that the tool bit was only held with one screw. However, this proved more than adequate when it can down to it.



You can see that I have marked the work out by drawing up in CAD and then printing onto an A4 sheet. held to the work with sticky tape. If you have several identical pieces to do this can save a lot of work in marking out time. For me, well it's just more accurate, center punch through the paper as normal.

Just beginning to take a cut, working ok but I decided that the tool tip was a bit too wide, so reground it to a point. You can see that I have a 45 deg chamfer on the tool. My thinking was that if the cut came out a little rough I would always lower the quill to tidy up the finish by increasing the size of the hole. Again this worked quite well.



The result, quite tidy I'd say, took minimal cleaning up and didn't burn the painted finish at all.



Then to drill the two valve base mounting holes with a 19mm hole saw. This was easy of course.



Transformer now the right way up and in position, Lovely jubley !!!




The trapanning was done at the slowest speed of my mill. Cutting proved to be stable if a little on the slow side.
(112rpm digitally tested with my new "cheap" tool from the far east. I had no idea what speeds my mill was giving me and the belt positions were very confusing to say the least)

[bogstandard]

Nice one Darren,

A clear case of making do with what you already have.

Using dedicated machine tooling for use to do other things is a method I use.

I remember a couple of years ago, when ball turners started to become popular. I hacked together a fixture that used the boring head off my mill to do the job about 10 to 15 years ago, with very good results.

Use what you have got and keep the pennies in your pocket.

John