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Thread: What did you learn today?
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9th May 2019, 09:48 PM #736Golden Member
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I got the parts together for the treadmill motor drill press and wired it up yesterday, It works and will probably be fine for my purpose but it definitely doesn't sound like clean voltage is powering the motor, it runs with a bit of a buzzing hum to it.
I just need to clean up the old drill press and mount the SCR to it, then I can test drill some holes
DSC_1205.jpg
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10th May 2019, 09:52 AM #737Most Valued Member
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Is that silver solder or soft solder?...looks like soft ie lead/tin?
anyways, both soft and silver flow towards to heat.....on small stuff with silver soldering use smallest tip......a mapgas type will not give you adequate control so you need to back away and try and concentrate heat where you want silver solder to go
practice makes perfect
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10th May 2019, 11:59 AM #738
Hi Bill,
Your silver solder effort is not looking too bad at all, Bill
Silver soldering is nearly an art form. It takes a while to pick up the nuances in managing the heat input.The filler wire must be melted by the heat held in the parent metal. This has been with Oxy acetylene heating not LPG.
Good flow of the metal is promoted by good cleaning and fluxing which allows the required capillary action.
Half the trick is to deposit just the right amount of filler volume. Note that my comments following pertain to uncoated filler wires.
Much can be gained by observing the flux after it is applied. Silver solder flux is borax plus some other chemicals and applied as a creamy texture in areas where you want the silver solder to travel and adhere to.
When the flux dries out in its container it can be brought to a cream like consistency with water. It is well worth noting the visual signals that the applied flux displays when applied and heated.
The flux ,when heated will change from a wet condition to a crusty 'dried toothpaste" appearance and when further heated will change again to a clear liquid.
Shortly after that stage the work is ready to receive a stroke of the filler which immediately should be absorbed or sucked in to the joint via the capillary action.
Knowing how long to heat is determined by the conductivity of the different types of metals.There is a learning curve.
I always used blue tip which was 45% silver but I realise the silver solder available today is not the same as it once was. I had difficulty with the cadmium free SS as it does not wet and flow like the former.
The other respiratory hazards are in the flux which contains all sorts of flourates and fluorides etc. which are harmful. Good ventilation and respiratory protection is good idea.
I hope this can help someone.
Grahame
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10th May 2019, 06:11 PM #739Golden Member
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Graham and Eskimo,
Thanks for the tips.
Am using solder sticks, 45% silver, with Cadmium, 1/16" thick.
Got so excited when it started melting that I kept at it watching it melt and put far too much on hence the big blob.
Realised that 1/16" is far too thick for my current jobs, so for any novices stumbling across this thread, get the 0.5mm solder sticks for small scale jobs.
Have since learned how to flatten it with a hammer and snip off tiny pieces - that works and controls consumption.
Have also realised that holding the workpiece in the right orientation can sometimes be a challenge ie I did read somewhere that I should try to get both gravity and capillary action going the same way by combination of workpiece orientation and applying heat in the appropriate place.
Bill
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10th May 2019, 06:45 PM #740Member: Blue and white apron brigade
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Hope you have really good ventilation or fume extraction.
Info extracted from a couple of MSDS for silver solder with cadmium.
Where the solder includes cadmium, the evolution of cadmium fumes during heating contains the greatest hazards. The effects of inhalation are throat dryness, cough, headache, vomiting, chest pains, extreme restlessness and irritability, pneumonitis and possibly bronchopneumonia. Long term exposures may cause kidney dysfunction and lung injury (emphysema) as well as other symptoms. In severe cases death may result. Cadmium is classified as carcinogenic.
Just in case
If breathing is difficult, trained personnel should administer emergency oxygen if advised to do so by the Poison Control Centre/Doctor. DO NOT allow victim to move around unnecessarily. Treat pulmonary edema as a priority, even if no symptoms (i.e. wheezing, coughing, shortness of breath, etc.) are apparent. Symptoms of pulmonary edema can be delayed up to 48 hours after exposure. Quickly transport victim to an emergency care facility.
OHS limits for Zn0 are typically 5mg/m^3 (same as softwood sawdust)
OHS limits for Cd vapour or fumes are 1000x lower 0.005 mg/m^3
Hexavalent Cr is 10x lower again so 0.0005 mg/m^3
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10th May 2019, 07:30 PM #741Most Valued Member
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10th May 2019, 08:19 PM #742Most Valued Member
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Is cadmium free silver solder available?
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10th May 2019, 08:40 PM #743Member: Blue and white apron brigade
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Yep, Most welding places sell Cd free stuff
eg https://www.boc.com.au/shop/en/au/we...ng-alloys-flux
Here is an MSDS covering a range of Ag solders from 5 to 88% Ag
https://www.hswalsh.com/sites/defaul...g%20Alloys.pdf
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11th May 2019, 09:49 AM #744Most Valued Member
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Yeah I bought some from Brownells over 20 years ago. Bob's right, this is a known issue and I wouldn't use silver solder with cadmium unless I had full breathing gear. It's a risk not worth taking when there are readily available alternatives.
Of course those who think carbon monoxide and water vapour are things only academics would care about will pooh-pooh the whole thing.
FKT
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11th May 2019, 10:10 AM #745Member: Blue and white apron brigade
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The other thing about Cadmium is that like Lead it will accumulate in the body and it takes about 30 years of life to eliminate half of any intake.
It also screws with your testosterone levels and "induces testicular interstitial cells hyperplasia" which I think means "makes your balls swell on the way to becoming cancerous". It also "decreases density, volume, quality and number of sperm, decreases libido and general fertility"
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11th May 2019, 02:21 PM #746Most Valued Member
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I melted 1.6 tonnes of lead scrap into blocks for my boat and I'm damn sure my lead levels have gone up a *lot* because I wasn't real careful. But I knew what I was doing to myself and I did keep the pour temperature down, wear gloves all the time and wash immediately I'd finished for the day.
Still got 2 bags of dross to dispose of at the local tip where you put dead batteries. I don't want the stuff getting into the soil.
PDW
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11th May 2019, 03:18 PM #747Member: Blue and white apron brigade
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I agree with your handling of dross.
Unfortunately the reality is we have already contaminated the top half meter of a lot of our soils, especially alongside roads and in cities through the use of leaded petrol. fortunately it currently just sits there as relatively inert/immobile lead-oxide There is apparently a time bomb awaiting us if the air/rainwater gets more acidic - this will dissolve the lead and send it into the water table.
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12th May 2019, 12:34 PM #748Golden Member
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BobL and PDW,
Thanks for the tips about the Cadmium. Will investigate further regarding better ventilation and breathing gear. Have asked on the UK forum as well as they do a lot of boiler building, will report back if they have any stunning revelations regarding best ventilation and breathing protection.
I had assumed it was banned in Australia and was so happy to find some silver solder locally that it was only after I started using it that I read on the packet it was Cadmium bearing. It is banned in Canada UK and Europe.
Anybody out there built their own simple fume extraction cupboards for dealing with any and all potentially poisonous shed activities ? I think BobL did and will do a search now.
I guess the danger is no matter how well ventilated the shed is if you somehow happen to breath in a slug then it is in your lungs. One of the issues I have seen discussed is particles settling out of the air and settling upon surfaces in your shed and then getting disturbed and into your lungs via breathing.
Bill
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12th May 2019, 02:31 PM #749Member: Blue and white apron brigade
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I have and can verify it works really well for ZnO fumes (can weld a bit of galv and have white fumes pouring off it and it doesn't seem to affect me) but I wouldn't trust it for Cd. Recommended Cd levels are 1000x lower and one simply cannot see any fumes at these low level.s
I guess the danger is no matter how well ventilated the shed is if you somehow happen to breath in a slug then it is in your lungs. One of the issues I have seen discussed is particles settling out of the air and settling upon surfaces in your shed and then getting disturbed and into your lungs via breathing.
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12th May 2019, 11:22 PM #750Golden Member
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