Positioning of PID probe-Toaster Oven

[alamogunr]

I'm finally ready to try powder coat. I even bought a 2nd PID so I wouldn't have to keep moving the one I use on my bottom pour pot. BUT, Where do I place the probe so that it doesn't give bad readings?

[Ausglock]

Under the wire shelf in the centre. Mine is 1/2" below the wire.

[vagrantviking]

I just drilled a hole in the top center and jammed the probe in. Sits just above the pan of bullets.

[Conditor22]

I'm with Trevor on this one.

[Walter Laich]

I came in from the side without the electrical stuff

Probe is between my two shelves.

love the way the PID holds temp to ±1°

[Conditor22]

IF you use a PID to control a convection oven you need to wire the convection fan directly to a power source. The rapid switching off and on done by the PID will burn out the fan.

[alamogunr]

IF you use a PID to control a convection oven you need to wire the convection fan directly to a power source. The rapid switching off and on done by the PID will burn out the fan.

Thank you! The oven I plan to use has the convection feature and that had not crossed my mind. We bought a new toaster oven a couple of months ago and this one is the older one that I took to the shop to replace an even older one.

[Dragonheart]

Just realize the PID is reading and correcting the air temperature in the oven and not reading the surface temperature of the bullets. The PC curing time & temperature is based on the substrate of the object being coated, not the surrounding air temperature. In my 30" oven coating several thousand bullets in a cook, the PID can reach 400 degrees yet it will take 30 minutes or more for the bullet surfaces to reach 400 degrees. That is when I start the timer.

[Conditor22]

I agree with dragonH to an extent.

IF the oven doesn't have a consistent temperature it is impossible to determine/calculate proper bake times

Some PC manufacturers say to start timing when the PC starts to flow, that would indicate that the surface has reached the desired temperature (what that is I do not know, never was important to me) the manufacturers have people that were paid to figure that out . I'm not sure the surface temperature has to be 400°, I never checked.

http://castboolits.gunloads.com/show...PC-long-enough

Not sure if this directly correlates, but you bake a turkey at 425° but you're done when the bird reaches 165°

One way to speed that up is to put some type of heat retaining material on the floor of your oven to help get the oven back up to temperature faster after the door has been opened [DON"T BLOCK THE HEATING ELEMENTS] I use ceramice BBQ briquettes (thats what I had on hand) others use fire brick or ?

I have found that at a consistent 400° 18 min for smaller batches and 20 min for large batches has worked well for me. The PC I tested did not react to different gunpowders but I'll start going 25 min to assure a full cure. YMMV

[igolfat8]

Could you drill a hole through a bullet, slide it over the temperature probe and then you will know the temp of the bullet and not the surrounding air? I’m just posing a question and not stating this as fact. I don’t have a PID for my oven but I am ready to pull the trigger.

[Dragonheart]

Could you drill a hole through a bullet, slide it over the temperature probe and then you will know the temp of the bullet and not the surrounding air? I’m just posing a question and not stating this as fact. I don’t have a PID for my oven but I am ready to pull the trigger.

The easy way is to take your mold, push the sprue cutter aside insert the end of an inexpensive thermocouple into a bullet cavity then fill the cavity with molten alloy. An inexpensive digital thermometer can be had off Evil bay for $5 that is surprisingly accurate. Placing the thermocouple in with the coated bullets this lets you monitor the actual temperature of the bullets. Even taking a shot on the bullets with an IR thermometer is better than guessing.

As far as timing powder coating I know of no powder manufacturer that recommends timing after the powder flow. Don't take my word for it check with the big powder manufactures, MIT & Prismatic powder, not just a reseller. They will tell you the timing starts when the substraight reaches the required temperature. Picking a timing number after the powder begins to flow is just plain wrong, it is just guessing when the substraight reaches the proper temp.

When you have an HVAC system in a residential home it is sized by the energy output of the system (BTU's) to heat & cool a known dynamic load. The dynamic load is the building elements, furniture, etc. All these things are adsorbing the energy. Lets say you have a home of 2000 square feet and the system cool/heats to temperature in a reasonable amount of time. Now you take that same HVAC system and put it into a similar built 3000 square foot home, what is going to happen? The HVAC system is going to run for much longer to achieve the same temperature. What changed, the system energy output is the same, but your dynamic load changed significantly and significantly increased the time it takes to come to the same temperature.

The Thermal Dynamic principles are the same in small toaster ovens. The oven outputs a specified amount of energy, but the load changes with the amount of bullets placed in the oven. More energy is absorbed if more bullets are added and likewise the length of time increases to bring a greater mass to temp. The efficiency of air movement inside the oven also changes as the mass is increased.

A powder starts to flow at approximately 150 degrees and a standard powder cures at 400 degrees, so how long does it take an oven to increase the temperature 250 degrees? The answer for some ovens is never because they cannot reach 400 degrees. For others it varies due to the oven efficiency and load. If one day you cook 100 bullets and the next day 2K bullets the load has increased and so the time it takes to reach 400 degrees will be increased. Adding bricks or other material to the oven in no way helps the oven reach temperature in a single cook. Indeed that just increases the load so it will take longer for the oven to come to temp. The only benefit to energy retaining materials is when multiple batches are done; the reheat time can be lessened due to the stored energy in the materials.

[WardT]

Drilled hole in side of oven 1/2" bellow rack.
Rewired fan with its own power cord so it is not switched with PID

[alamogunr]

I've got to get the oven down and access the fan. Haven't a clue how to get at it yet. They don't put these things together so they can be serviced. Considering the price, that's understandable.

[Conditor22]

I appoligize, Dragon is partially right. my thread "Most people ARE NOT baking PC long enough" h
ttp://castboolits.gunloads.com/showthread.php?370234-Most-people-ARE-NOT-baking-PC-long-enough
has a list of how to determin bake times with for different PC manufacturers. I use a lot of Easwood so the following stuck in my head.

https://www.eastwood.com/hotcoat-pow...ight-blue.html

Eastwood Powders are far superior to liquid coatings. They provide an extremely durable finish that is chip resistant. All Powders are formulated of the highest quality materials and are chemical and fuel resistant. Eastwood Powders are durable enough for under hood applications and heat resistant up to 250 degrees F. They are suitable for any metal surface and most cure at a temperature of 400 degrees F at 20 minutes after flow out. With Eastwood powders, you can be assured of high transfer efficiency and brilliant colors

[Dragonheart]

I appoligize, Dragon is partially right. my thread "Most people ARE NOT baking PC long enough" h
ttp://castboolits.gunloads.com/showthread.php?370234-Most-people-ARE-NOT-baking-PC-long-enough
has a list of how to determin bake times with for different PC manufacturers. I use a lot of Easwood so the following stuck in my head.

https://www.eastwood.com/hotcoat-pow...ight-blue.html

Eastwood Powders are far superior to liquid coatings. They provide an extremely durable finish that is chip resistant. All Powders are formulated of the highest quality materials and are chemical and fuel resistant. Eastwood Powders are durable enough for under hood applications and heat resistant up to 250 degrees F. They are suitable for any metal surface and most cure at a temperature of 400 degrees F at 20 minutes after flow out. With Eastwood powders, you can be assured of high transfer efficiency and brilliant colors

OK I read what they have posted, but also understand they say their powders cure at 400 degrees. A powder achieves it's cure by time & temperature so how can powder on an object cure at 400 degrees if the object has not reached 400 degrees? Flow out has nothing to do with the object reaching the actual temperature of 400 degrees.

Now I do see where you are coming from and I can say Eastwood has erroneously posted information I can assure you does not conform with the manufacturer who makes their powder. Eastwood has made a mistake as companies often do. It is your choice whether you see their mistake and act accordingly or not.

[igolfat8]

Powder Paint coating sits on top of the substrate right? I also suspect it bonds by mechanical adhesion. If you draw an analogy with vacuum forming, the sheet or membrane is heated to a pliable temperature and then it’s drawn over a mandrel or form to take its shape. Wouldn’t this be similar to what powder paint is doing? It’s heated to a specific temperature, then flows out over the substrate and bonds to the substrate by mechanical action. I don’t see how the temperature of the substrate is critical. The exterior temperature melts the paint, doesn’t it and not the substrate. Maybe I am missing something?

[Boomsticks Firearms]

The only reason why I would use the PID would be to monitor the temperature to verify that the oven is at temperature. It’s not like you need to control the temperature like when you are using your lead pot to keep the lead from getting to hot as you are casting. Now some powders does say that once the powder flows out like Eastwood that is when you start the timer. Now I make sure that all of the powder on all of the bullets have flowed out before i start the timer and i go by the time they recommend for that powder. I have tried both ways to start the timer what for the bullet to get to temp and what i just mentioned and i have found that if i just let it flow out completely like they recommend it works out like it should. I don’t know why anyone whould try to reduce the cure time so what if it takes a little longer if want to do more in a day either get a bigger over or get another but you do need to get the powder to cure.

Now for the Probe i would pot it as close to the bottom of the bottom rack or level with it preferably in the middle if possible. It’s not a bad idea if you could have the probe in a bullet but just remember that you probably like i do is cast different sizes of bullets like 70gr 32 auto up to 400 gr 50 cal bullets so it will make a difference and i have done different sizes at the same time so far it has been working for me the bigger bullets does take longer for them to flow out.

[Hossfly]

I just try to be consistent as possible, use a good thermometer, get oven as close to 400’ as it will get, then put in a load of boolits. Watch the temp with probe in middle of group, when it returns to 400’ start timing for 20 mins. Take one to anvil and beat flat with hammer, coating stays on, no flaking or pealing off, use that for standard for that power and size boolit. (K) thermocouple type thermometer. Usually put toaster on bake high to keep at 400’. Not convection, need one. Just use what I have for now, does real good tho.

[jsizemore]

All the kitchen convection ovens I work on have the thermocouple located near the top back of the oven cabinet. I calibrate them with a thermocouple located in the center of the oven cabinet.

[Dragonheart]

Regardless of where you mount the thermocouple and even with a convection oven, if you are doing several racks of bullets the temperature will vary between the racks and on the individual trays.

I have a PID controlled 30" convection oven running two 220v elements that will accommodate as many as 5 racks. It will also easily handle 1/2 sheet commercial baker's pans and a pan will hold hundreds of bullets. I often load all 4 pans with 3600, 9mm bullets total. That's about 65 pounds of alloy plus racks & pans and the inner oven to bring to temperature. I can easily see the difference in heat as the powder starts to flow. The upper and lower trays will start to flow from the outside in while the 2 inner trays have not started to flow. I have also confirmed a temperature variation using a digital k thermometer with the end of a K thermocouple cast into a 200 grain bullet. This probe allows me to monitor the temperature where I need it most and that is the inner pans that come to temperature last. Even with a PID holding a constant oven air temperature of 400 degrees it may take 30 minutes or more for all the bullets to come to 400 degrees. My convection toaster ovens have multiple racks also and I first observed the same thing when multiple racks were used. Before I made my bullet K probe i used to crack open the door and shoot the tray with a IR thermometer; nowhere near as good, but better than a flat guess.

So my answer is where you install your PID probe is up to you because in fact you are still only measuring the air temperature at that point in the oven and not the substraight temperature of the object which is half the equation for a proper cure. The other half is the time the substraight stays at that temperature. Time can easily be extended just to be sure, but if the temperature does not reach the proper cure point, whatever that might be, then proper curing is not going to happen. This simple concept is the reason that timing after flow for 20 minutes would not even begin to work for those doing any quantity of bullets like myself or those using an oven with limited efficiency or airflow to begin with.