Friday, January 05, 2007


Never leaving well enough alone...

I decided to try a few new things with the Mk 2.1 extruder barrel. First off, I decided to braise the barrel into a heavy bar of copper and bolt that onto the PTFE bar laid sideways 37.5x25x25 mm. If I passed the 5/32 inch copper pipe about 5 mm beyond the bar instead of making it flush against a flared fitting as I did before I'd be able to tap the 3 mm filament channel through the PTFE out to 5/32" and seat the barrel directly into the PTFE thus insuring a smooth fit that wouldn't slip.

Finding 1x1/8 inch copper bar wasn't possible, though. I double checked my braising rods and discovered that they would do brass as well as copper, so I decided to do the whole show in brass instead of mixing and matching.

I just bought the yellow brass bar stock, very hard and stiff 5/32 inch yellow brass tubing and some .127 mm yellow brass sheet. I have great hopes for that very thin brass sheet. I can certainly make it thicker, but I'd like to see if it will work at that thickness. It seems quite strong and the braising will give me a very strong joint between the tubing and the sheet.

The point of the .127 mm brass sheet is that it is VERY easy to tap with those wire gauge drill bits. I managed a 0.5 mm hole in about 5 seconds then went for broke and used a #80, which makes a 0.3429 mm hole. That happened with no complaint whatsoever.

I also discovered a new trick. If you place your sheet over a piece of chipboard, when the drill bit penetrates the brass the chipboard prevents burrs in the brass from catching and binding the drill bit. It seems to be much safer than drilling through brass into air in terms of avoiding breaking the bit.

your last tip there is a good one =)
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