Dennis
19-07-2011, 05:17 AM
I mainly make small one-offs , but recently I have fretted about the lack of finish on the insides of my pieces, where hand tools can’t reach. So after all these years, I decided to buy a mini-barrelling machine with a two pound barrel and internal fins. I also bought some mixed stainless steel shot and for lubricant I have been using up my TSP left over from experiments with niobium.
The big problem with plastic barrels is that they rely on the accurate fit of the lids at each end, which means that closing them is quite a struggle. To achieve this , air has to be let out of the barrel by raising one edge of a lid and pressing down on its centre. After several attempts at this and some bent back fingernails, you might find that the opposite lid has come adrift, allowing shot into the gap, which will prevent it from being re-seated.
To avoid all this, I decided to make an air vent with an improvised seal using a stainless steel nut and bolt, which I found in my local ironmongers, two rubber washers punched out of neoprene (tap washers might have done) and some metal washers pierced from stainless steel sheet. I also brazed wings onto the nut, using silver solder and Tenacity No 5 flux, so that it could be tightened with my fingers.
What a relief! The lid now closes easily with a loud hiss of escaping air and the nut can be tightened to re-seal the vent. Dennis.
The big problem with plastic barrels is that they rely on the accurate fit of the lids at each end, which means that closing them is quite a struggle. To achieve this , air has to be let out of the barrel by raising one edge of a lid and pressing down on its centre. After several attempts at this and some bent back fingernails, you might find that the opposite lid has come adrift, allowing shot into the gap, which will prevent it from being re-seated.
To avoid all this, I decided to make an air vent with an improvised seal using a stainless steel nut and bolt, which I found in my local ironmongers, two rubber washers punched out of neoprene (tap washers might have done) and some metal washers pierced from stainless steel sheet. I also brazed wings onto the nut, using silver solder and Tenacity No 5 flux, so that it could be tightened with my fingers.
What a relief! The lid now closes easily with a loud hiss of escaping air and the nut can be tightened to re-seal the vent. Dennis.