Brass - machining a large slot

[hespj]

What do you think the chances of me being able to machine the brass item shown in the attached images is? The piece is about 5' long (1500mm) and has a 4" (100mm) wide by 0.08" (2mm) deep trough machined along its full length.

Actually there isn't one piece there are 48 pieces of similar but varying shape. We'll probaly get them laser cut to shape (leaving screw down tabs at regular intervals along the edges).

The trough doesn't have to be that accurate side to side. In fact the trough is on the inside hidden side of the piece, and won't be seen when installed so finish isn't an issue either. It's just there to provide clearance.

I've got a small sample of brass to practice on. I'll know what sort of brass it is in a day or two. My worry is that this is a lot of material to remove and is asking a lot of a ShopBot.

Thanks in advance for any advice,

John

[hespj]

Looks like it is possible. I've now cut 18 of the 48 pieces. I'm machining the "slot" (approx 1.25 hours each), engraving some identity info on the inside of the slot (5mins), then profiling them (1.25 hrs).

Then there's the actual getting the sheet of brass (6.5' x 3.5' x 3/16") onto the ShopBot, drilling holes for hold down, and screwing down. Not to mention toolpaths. Oh, and trips to London to take templates from the structure these brass pieces will hide.





John

[Brady Watson]

Good thing it's cheap, John

Nice work.

-B

[hespj]

Thanks Brady.

Yes, it'll need 9 sheets at least. Good job I'm not paying.

But I see the scrap price is quite good. I've already got about 100lbs of swarf, and then there are offcuts. In the top photo there's a whole area towards the left of the sheet which is unused.

John

[Brady Watson]

But I see the scrap price is quite good.

Oh yeah...that is a nice little bonus. I was pleasantly surprised when I took some in for scrap.

-B

[hespj]

Finished this back in April, two years after I started this thread! I wasn't cutting full time - it just felt like it. Slow, noisy work. I would go into the office and draw whilst the ShopBot cut, but it was noisy. Here's a video of it being cut:

www.youtube.com/watch?v=23sV9kyqmXA

I got $500 for the scrap and I've still got a couple of sizeable offcuts in the workshop.

In conclusion - It can be done - get the right cutter cutter and it'll cut just fine. CNC milling machines aren't usually over 5' long, so if pieces over this length are required you might be able to charge a good rate.