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cutting a thin brass disc

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Dave Jones 114/06/2010 15:18:47
85 forum posts
5 photos
Afternoon all, i was wondering if someone could help.  I need to make three thin brass discs 1" in diameter out of 20g brass.  How would you go about doing it?  The ideas I have come up with so far are as follows; 
1. Loctite a piece of brass to a faceplate and trepan tool (dont quote my spelling of it! but plunge a tool into the brass at the correct diameter producing a disc.
2. mark out the shape and cut/file using a jewellers hand saw/files
 
How would everyone else go about it, and are their any other methods I havent thought of? I dont have access to a mill or a rotary table.
Dave
KWIL14/06/2010 16:12:07
3681 forum posts
70 photos
Araldite the three rough discs to the end of a previously turned mandrel held in a chuck. When set, turn all at once "lightly" in the normal way, heat to remove. 
Dave Jones 114/06/2010 16:25:56
85 forum posts
5 photos
Many thanks, ill give it a try
Dave
NJH14/06/2010 17:41:48
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2314 forum posts
139 photos
.......or maybe buy ready made from clock makers supplies?
 
Try here :-
http://www.clockmaking-brass.co.uk
 
 
 
 
mick14/06/2010 17:51:47
421 forum posts
49 photos
Instead of glue, try holdind the discs in position with a preasure pad slightly smaller that the finished size.  This is supported by a revolving tail stock centre.   By only taking light cuts  you should be fine
Ramon Wilson14/06/2010 18:02:43
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1655 forum posts
617 photos
Dave, I have used  the following way before.  Certainly works for small discs providing light cuts are taken and you have a revolving centre
 
1 Cut out material -  octagon or rough circle. Best to get it as close as reasonable to keep the number of cuts down
 
2 Chuck a piece of steel the same or just above the diameter required, Face and deep centre. Turn to diameter of disc if required then part off the end about 3/8 long.
Face the end still in the chuck. Hold material against face and bring the other piece up to bear applying  pressure with the tailstock. This will allow light cuts - if it does slip a piece of paper between face and part will help.
 
Very sharp tool and very light cuts.
 
Just another variation
 
Hope this is of use to you
 
Regards - Ramon
 
 
Touche Mick my apologies for repeating your advice

Edited By Ramon Wilson on 14/06/2010 18:03:46

Jeff Dayman14/06/2010 19:13:34
2356 forum posts
47 photos
Hi Dave,
 
It's a bit of work, but if you've got an arbour press you could make a simple punch and die. If you make the die from air hardening tool steel and the punch from drill rod you've got the Cadillac of disc makers.
 
Die should be 1" id and punch a couple thou under 1".
 
Some work as I said but now you have a way of making blanks for all future requirements for disc turning by the methods others have mentioned.
 
You could also have the disks laser cut or waterjet cut but that's a bit old fashioned for me 8^)
 
 
 
 
Terryd14/06/2010 21:32:58
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1946 forum posts
179 photos
Hi There,
 
I've done this before by using a faceplate with a birch plywood facing and the brass fastened to the plywood.  I attached all with plenty of double sided Sellotape (Scotch tape in the USA)
 
Using a sharp pointed lathe tool with one face (the inner one) set at 90 degrees to the brass sheet, I took a series of light cuts and did the whole job in minutes.  I was even able to turn the outer diameter of the disc while attached to the plywood.
 
Double sided tape has an incredible hold in shear. The parts are easily separated with a sharp blade between them and the Ply backing can be used over and over for several components.
 
Terry
Terryd14/06/2010 22:47:14
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1946 forum posts
179 photos
P.S I've used the same Faceplate/plywood/Sellotape trick when cutting copper discs up to 150mm dia and turning the outside diameter of MS discs up to the same size.  Copper is much more tenacious material to cut than Brass and I've never had a problem.
 
I should point out that I cut the discs roughly to shape first on a hand shear before mounting.  But it still takes only a few minutes from start to end.
 
Terry
Bogstandard15/06/2010 06:48:23
263 forum posts
Try this
 
http://www.homemodelenginemachinist.com/index.php?topic=1510.0
 
Bogs
Terryd15/06/2010 08:20:10
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1946 forum posts
179 photos
Hi Bogs,
 
there is also an example, on the same site, to machine the endplates of a copper boiler here  scroll down the thread to see the pictures.
 
This example uses the double sided tape method I discussed above.
 
Terry
Ian S C15/06/2010 11:01:33
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7468 forum posts
230 photos
Jeff Dayman,for three discs Dave would proberbly get away with mild steel, punch and die. It might be best if the cutting face of the punch is not parallel, ie., it starts cutting at one point and shears as it advances into the die. I did two hundred .007" by 5/8" od 1/4" washers from hard brass using mild steel tooling, using the vertical mill as a press. Ian S C
Bogstandard15/06/2010 11:42:56
263 forum posts
Terry,
 
I too use double sided tape for when making multiple blanks. As long as you get enough end pressure from your live centre, you can cut dozens at a time.

I made a whole load of brass dog tags for a chap who ran a breeding kennels.
 
It is about the quickest method to produce discs of almost any size, thickness or material.
 
I have been doing friction turning for many years, and have even friction turned 2ft diameter  by 2.5" thick cast iron lapping plates, refacing them. It saved a fortune over what the manufacturers wanted to charge for doing the same thing, but by surface grinding. What you are turning won't go anywhere, as long as you use the live centre.
 
Here is another one of mine from the same site, but using much thicker material
 
http://www.homemodelenginemachinist.com/index.php?topic=1809.0
 
 
Bogs

Edited By Bogstandard on 15/06/2010 11:57:17

Jeff Dayman16/06/2010 12:47:09
2356 forum posts
47 photos
Quite right Ian SC, mild steel tooling would be fine for brass disks. The tool steels and hardening recommendation was force of habit from my work experience I guess!
 
As to the shear angle on the punch you are again right, but while this will lengthen the shearing time and reduce force required, it can sometimes distort the slugs being cut. If the punch is flat square ended you have the best chance of a clean flat blank. Since in this case we want to keep the blanks, it might be best to keep the punch square.
 
In high speed dies I used to design and make, all punches for holes (where the blank was scrap, and we kept the surrounding metal) had double shear angles or four shear angles on the faces, concave shaped ie depressed toward the punch centre. It worked well and extended press crankshaft bearing life considerably by reducing shock of impact. Another trick we used was to stagger the punch lengths slightly acress the dies (sometimes these dies had hundreds of punches).
 
But getting back to our brass disks I second the double sided tape method, I've used it several times with success, as well as shellac.
Ian S C16/06/2010 13:47:49
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7468 forum posts
230 photos
The last time I used the method of sticking an artical onto a stub was when I was wood turning (gave that up in the late 80s), I used to stick a bit of paper between the block of wood on the face plate, then stick a block of wood to make a large bowl, just used PVA wood glue. When finished put a chisel to the joint-wack, the paper splits, some water on a cloth, the papers gone. So glues OK. The idea of the angeled punch was to reduce the pressure required, Dave proberbly does'nt have a press, so the drill press could be used.Ian S C
Geoff Theasby16/06/2010 15:03:47
615 forum posts
21 photos
Hot melt glue also works.   I used it for turning some wooden buttons for a cardigan my wife knitted, but it is very strong and should work for brass discs.
Ian S C16/06/2010 15:08:19
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7468 forum posts
230 photos
Thanks Geoff, never thought of that, there's a hot glue gun some where around here, must try it. Ian S C

Edited By Ian S C on 16/06/2010 15:09:45

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