Brass shaping

How does one set about cutting a figure of 8 in a brass plate 16mm thick. with the two 0s of the 8 cut to a depth of 8mm, and a neck between the two circles of the 8 ? I have a piece of brass plate 100mm x 50mm. The outer diameter of the circles is 45mm for one and 30mm the other. The total length of the 8 is 85mm.The neck being 10mm x 10mm.

I have drawn it out on a piece of paper but I don't know how to form it. I could hacksaw it out roughly and file to shape but I think that would be called butchery !!

bandsaw outside, boring bar in mill for o's. (or find a water jet cutting house nearby and ask them to do it - price may be very reasonable)

Ideal job for a cnc mill

Or if you want to do it yourself

make print of job stick to brass and cut with whatever you have file outer edges

do the centre of the 0's go right through or just 8mm deep?

you will need a mill to do that if they dont go through

Thankyou Jeff. Unfortunately I live in a fairly remote area of mid-Wales and water jet services are not available. I only have a small horizontal mill and I am not sure if I could do the boring bar operation, but I can try.

Like most things Roger - I think it depends on what equipment you already have, like a bandsaw (for instance) or a vertical mill and rotary table?. If you only have a lathe and a drill then your options are more limited.....

However, I think you could still carefully mark it out, pop mark your centres, then simply chain drill the outside before you bore the internal recesses to size (easier to hold in this order) before finally cutting through the hole 'chains' and filing smooth the outside

Two small 'radius' chain drilling jigs might help you here and I wouldn't use a very small a drill as the brass is fairly thick (at 16mm - a 2mm drill will still be drilling x8 it's diameter). You could also turn a couple of simple circular filing guides if you filing isn't that hot (rather like mine!).

If you've a mill and rotary table - then life is much easier...

Regards,

IanT

Would a Dremel with a burr head cut out the 'O's.

16mm plate and 8mm depth suggests not all the way through.

I would do the inner O on the mill with a rotary table and as much of the external O as possible then while still on the R/T do the tangental cuts towards where the X is in the middle. If you are not doing tangental cuts but just having two "O" shapes butted together than even easier with the Rotary table

Edited By JasonB on 30/10/2017 13:26:46

You can "bore" the internal holes in the lathe Roger using the 4-jaw or faceplate - and it's really just a facing cut from the centre (outwards) at that kind of required depth - use a facing tool pointing towards and slightly inclined toward the headstock, with the cutting edge facing you. Take light cuts to almost the required internal diameter and then a cleaning cut to final size.

Regards,

IanT

It might be possible to do this on your horizontal Roger (with a boring bar in the spindle) but without a vertical head it would be tricky. Provided you can hold the work, I'd use a lathe for this part of the machining, much simpler in my view.

Regards,

IanT

Could you use two layers of 8mm plate and sweat them together? Then the cutout could be made with hand tools.

Brian

Mount your rotary table on it's side with the table facing the spindle, centre rotary table to spindle centre and lock the Z slide. Leave enough gap for the material and tool projecting from spindle.
Clamp brass to table with 1 circular recess centered, use a slot drill or plunging milling cutter to cut the circle to depth and diameter by a series of X axis moves to increase diameter and Y axis for depth to that required.
Move clamps to suit 2nd circle required and repeat above.

Emgee

As an extension of Brian G's idea Roger - turn and bore two 8mm thick rings of the required diameter, then machine two flats on their edges and sweat them onto a back-plate!

IanT

Thankyou for all of the suggestions. I think I will try the rotary table on my horizontal mill first (using some scrap ally) and if not successful the lathe solution . I cannot braze two disks together as there has to be a hole joining the two Os of the 8. The set up is for the base of a carburettor with the larger O for the float chamber and the smaller for the base of the mixing chamber. Again,thank you all for your ideas.