Powder coat issue

P

popper

Well-Known Member
Triboelectric effect -- friction resulting in the flow of electrons from one material to another!
The ability to retain that charge is determined by the material, in our case, lead and polyester. #5 container is decent, (PP), doesn't retain moisture and is durable. PVC can retain moisture. H2O is polar, captures electrons that 'kill' the process. Swirling powder gains charge and is attracted to the lead. Shaking gets the charged powder to float in the air where it settles on the bullets. ASBBs (IMHO) get charged and help to swirl the powder. Try swirling only powder - doesn't work well. I tried HF and Smoke's gloss black, didn't do well, results like the OPs.
As to time, make/buy lube sticks and lube sizer, vs shaking 2 min and another 10 to stand them up? Walk away and let them cook. No brainer! If they pass the smash test will shoot OK.
 
KeithB

KeithB

Resident Half Fast Machinist
I'm looking forward to trying powder coating at some point in the future. It seems as if there are a lot of positives as well as some negatives to the process. I view it as a possible alternative, not necessarily a replacement for traditional lubes. Same as dry lubes, paper patching, etc., it's nice to have choices!
 
H

hornetguy

Active Member
Success! It appears that the powder makes a huge difference in the static buildup.
I got my two bags of Smoke's powder in, and found some 45 swc's I had cast a few years back.. in fact, when I was trying PC for the first time.
I did 24 of them (one rolled away that I didn't notice before I put them in the tub :rolleyes:)....
I did not heat the bullets any, just preheated the oven for about 6 or 7 minutes. Over the years, the bullets had started to oxidize a little bit, more like a light patina, which worried me a bit.... but, nothing ventured....
I put them in the tub with a small handful of bb's and about 1/4 teaspoon of OD Green powder. I swirled them around with an occasional shake, for right at 1 minute. Opened it up, and they looked pretty well coated to me.
I used a forcep to pick them out and stand them on end. I looked in the tub, and there was no powder left in there at all, which indicates to me that I should have used more like 3/8 to 1/2 teaspoon. There were still a few small spots that didn't cover with the powder, but nothing like the old powder.
I heated them up to about 300-350 and started seeing them shine... after a couple of minutes of that, I turned up the heat to what the dial indicated would be about 400, and let them bake for almost 20 minutes. This is what they look like.... the next batch will be better, I'm certain.

I almost forgot, I ordered a convection style oven today, should be here Friday.... startin' to feel like Christmas... now I need to cast more bullets..

PC OD green 45 swc.jpg
 
Last edited:
fiver

fiver

Well-Known Member
get you a 7-8 dollar oven thermo at the wal-mart and go by it.
my oven is off like 75 degrees low.

i spent the day making 3105 bullets 3085 so i can coat them to 3095-310.
dunno why, i could have just not flipped the switch on the star [off] and put lube in the ring in the same amount of time.
guess i'll find out when i start shooting them and comparing them to the ones i put through the machine 10 minutes previous.
 
H

hornetguy

Active Member
Oven temps are difficult to verify. Position of the probe/gauge, convection/not, accuracy of thermometer.... etc.... We have precision lab ovens at work, and we have to "map" them when validating them. Putting a highly precise thermocouple at 10 or 12 different locations in an oven is an enlightening experience.
I think the best we can hope for is "pretty close" for most ovens.... convection should make that better.
And, look at the oven thermometers.... are they truly accurate? If you don't have a precision thermometer to compare them to, you really don't know. I suppose you could buy 2 or 3 of them and put them all in the oven to compare them to each other, just to give yourself a warm fuzzy about their "accuracy"....
 
RBHarter

RBHarter

West Central AR
To about 200° it's pretty easy to verify one in a gallon of distilled water with altitude adjustment. Probe types anyway .
 
KeithB

KeithB

Resident Half Fast Machinist
Well, pure water boils at 212F if the pressure is 14.7 psi absolute. Temp will vary a little for different pressure but not much and can be compensated for.
 
Tomme boy

Tomme boy

Well-Known Member
I use the temp probe on my fluke multimeter. Works perfect. I had it calibrated back when I worked at the metal forging factory. I used it all the time to check the tanks that had different chemical in them to put the phosphate on the parts. And in some of the presses to check oil temps. I had the QC dept do it just because. It was off 3-5 deg throughout its range. That was close enough for my uses.

My oven is off about 50 deg low to the setting. Problem with mine is the 75 deg swing. It would over shoot the setting. I then added a 3/4" thick 3"x8" aluminum plate to the bottom of the oven. That created a nice heat sink that really helped stabilize the temps. You just have to preheat it for about 20-30 min to get it warm before actually using the oven.
 
H

hornetguy

Active Member
I have a digital temp readout with a thin probe TC on it... I've been using it as a thermometer for the garage... If I can figure out how to get it into the oven, in position, without having the door cracked open, I could use that. I'm not sure I want to drill a hole through the side of the new oven to allow insertion.... still thinking about that.
 
CWLONGSHOT

CWLONGSHOT

Well-Known Member
59BFAC2B-7097-495D-9622-6078056C717B.jpeg

I use lava rock in bottom of the oven. Thermo inside like Reloader showed and checks with a HF Digital Laser thermo.

Cause bottom line is oven temp is one thing but actual bullet temp for time required (after flow) is whats important. Small quantities of small bullets aint the same as larger quantity of big heavy bullets.

CW
 
Last edited:
Brad

Brad

Benevolent Overlord and site owner
Staff member
CWLONGSHOT said:
Cause bottom line is oven temp is one thing but actual bullet temp for time required (after flow) is whats important. Small quantities if small bullets aint same
As large quantity of big heavy bullets
Click to expand...
Man, if this is t the truth!

I bake 45 cal longer than I do 35. I want to make sure the bullets get hot enough to let the powder really flow and bake properly.

When I doubt, bake for another 5 min. My 45 cal bullets go for 32 min. Give them plenty of time to come to temp and give a good 20 min for proper cure.
 
H

hornetguy

Active Member
I tried out my new convection oven, and it seems to work very well... it showed to be about 20 deg above setpoint, according to my wally-world oven thermometer.
I did two batches of 35 bullets each (.45 235gr) and both came out very nicely... in fact, in whirling the bullets for only 1 minute, I almost had TOO much powder on them. I was tapping each bullet on the side of the yogurt tub pretty briskly to knock off all I could, and they still ended up with a pretty thick coating. I only used about 3/8 tsp of powder for the 35 bullets, and still had a little powder left in the tub afterwards....

I'm considering getting a Harbor Freight vibratory tumbler to see how that works, compared to shake and bake. Anybody have any experience using a tumbler? I watched a utub video where a guy used one, and his bullets came out very evenly coated, a nice thin, but complete coat. He picked them up to put them on the tray for the oven, and he couldn't knock the powder off.... he was manhandling them, with no ill effects....
 
H

hornetguy

Active Member
Hmm.... I've wondered, do you see the powder "slumping" downward when you just dump and bake? Gravity being the law that it is, I was afraid that the paint would tend to slump downwards, making the low side of the bullet thicker than the top side....
 
Rockydoc

Rockydoc

Well-Known Member
I suppose that might happen if there was an excess of powder on the bullets but that is what the shaking of the tray is far. You can't shake all of the powder off if you tried, just the excess.
 
Reloader762

Reloader762

Active Member
hornetguy said:
Hmm.... I've wondered, do you see the powder "slumping" downward when you just dump and bake? Gravity being the law that it is, I was afraid that the paint would tend to slump downwards, making the low side of the bullet thicker than the top side....
Click to expand...
Individuals coat their bullets using various amount of powder to get the desired coating they like. You can find photos all over the internet of coated bullets with various degrees of coverage. Individuals use several ways to remove any excess powder, as in shaking it off in a basket or picking up the individual bullets and taping them on the side of the container.

Personally, I just figured out over the years through trial and error just how much powder I need to put in the container to coat whatever bullets I'm coating and get the coverage I desire without having to use a basket or taping the bullets to remove any excess powder. Once I do the shake and bake, I simply stand the bullets up on the baking sheet with a pair of tweezers, no shaking or taping necessary. Nothing is perfect and on occasion some of the bullets in the bottom of the container under the BB's I use have a little excess powder, I can usually just give them another few seconds of shaking and it gone or I just tap it off.

Here is the Lyman #357443 which has a hairline crimp groove on the front driving band, if any excess powder was on those bullets using those colors and it slumped the line would basically disappear.

100_3343.JPG
 
Last edited:
fiver

fiver

Well-Known Member
i dump the bullets into a little pan i drilled holes big enough to let the BB's go through.
they will sometimes let a short 30 cal bullet slip through too.
but the shaking and rolling knocks the excess powder through too and evens everything out.
 
You must log in or register to reply here.