# A low temperature oven for drying and curing



## GailInNM (Dec 5, 2008)

With the official start of winter only a couple of weeks away my shop gets quite cool between workshop sessions this time of year. Paint, epoxy, epoxy paints, Loctite and other sundry things like it warmer than the ambient shop temperature to dry, harden or cure. I use a improvised low temperature oven to keep things warm while to eliminate this problem.

The oven element is an ordinary electric heating pad like you use to keep your toes warm in bed or relieve the muscle pains associated with showing that you can still do the type of thing you could do 15 or so years ago. Most of us already have one around the house, but if you must buy one, they are 10 to 20 US$ at the local store. If you do buy one, many of the current offerings have an automatic timeout where they turn off after two or three hours. You DON'T want this. Be careful as it is sometimes in fine print on the package that it has this feature. Buy a cheap one as you don't need the moist heat functions or anything of that nature.

The oven chamber can be very simple. In it's cheapest form, use a cardboard box about the same size as the heating pad. I put a piece of styrofoam insulation on the floor, put the heating pad on top of it, then place the part to be kept warm and cover with the cardboard box. If you have something that might drip or stick, a piece of paper or foil between the pad and the part may be a good idea. If you don't have any styrofoam, some cardboard or a carpet scrap will also work. 

For the deluxe version, use last summers styrofoam ice chest/beer cooler. Cut a slit in side for the power cord and build up your stack of heating pad and parts in it an put the cover on. 

The heating pads are safe and will not overheat to cause a fire danger. Remember they are designed to be used under the blankets in bed with you. 

Gail in NM,USA


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## CrewCab (Dec 5, 2008)

Good tip Gail 8)

CC


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## dsquire (Dec 5, 2008)

GailInNM  :bow:

Use an old refrigerator. Remove all the cooling apparatus to make it lighter if you wish. Install a light bulb inside and be sure it stays on. By varying the wattage of the light bulb you can control the temperature. Welders will sometimes do this to keep welding rod dry. 

You can keep all your paint and glue in here and not have to worry about freezing. On top of all that you have adjustable shelves and dust free storage.

Cheers

Don


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## mklotz (Dec 5, 2008)

Look for heating pads in your local Salvation Army (or equivalent) outlet store. Also, while there, check for:

toaster ovens (always handy in the shop)
ugly gooseneck lamps (to convert to machine lamps)
never used treadmills (nice speed controlled DC motors)
etc.


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## georgeseal (Dec 8, 2008)

As Marv said toaster ovens.
I use mine for baking paint. About a hour at 300 F then turn off and let part cool in the oven.


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## Jasonb (Dec 8, 2008)

A lot of figure painters use a crock pot as I think they are termed in the US, I just use a light bulb in close proximity to the paint to loose the sheen on oil based paint.

Jason


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## baldrocker (Dec 8, 2008)

> nstall a light bulb inside and be sure it stays on


The old conumbren.
How do you tell if the light goes on off when you close the door?

I know I know "conundrum"


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## dsquire (Dec 8, 2008)

baldrocker  said:
			
		

> The old conumbren.
> How do you tell if the light goes on off when you close the door?
> 
> I know I know "conundrum"



baldrocker

You Drill a hole thru side so you can see light bulb. Put Duct tape over hole after

Note: This hole can also be used to regulate temp if need be. :

Cheers

Don

(_This message not approved by Red Green)_


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## jack404 (Dec 8, 2008)

A mate here at Jindabine ( cold countryfor here ) has a great rig

he has a fridge set up like dsqire states but its a bit different 
he has a 12volt setup with a small solar panel and motor cycle battery rig to run it
it has a bulb in the bottom with a cheap POT to dim it for the seasons or control
this is in a chamber at the bottom 
the chamber is made by a small sheet of galv. steel 
sheet above the light
the whole sheet gets warmish but not hot 
he has a small hole (about 1/2") in the top of the fridge to let heat out and any moisture
but he has some steel mesh glued in place over the hole so critters and wasps dont get in 

again :big: :big: :big:

cheers jack


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## Andy_B (Dec 9, 2008)

Pictures below are of an upright freezer converted to a kiln that I use for drying wood that I use for turning. Another hobby ;D It has a thermostat that controls the heat at a set level. In winter I have stored my finishing supplies inside and set the temperature to be maintained a 45°. Works very well and the electrical cost is nominal.

Andy


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## raym 11 (Dec 9, 2008)

I use a toaster oven to cure powder coat. It is not really acceptable because of lack of temp control at 400 to 500 degrees . Wrong brand?
Does any one have other ideas short of buying a real oven?.
btw, any ideas on metal heat treating ovens on the cheap?

Ray M


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## Kludge (Dec 9, 2008)

Hmmm ... heating pad ... sounds good. And, yes, even here in Hawaii a little extra heat is nice.

I have a toaster oven that is good for lots of things - heating goezovers for interference fits, tempering steel pieces that will fit in it (around 450o for 1/2 hour or so seems to work 'jes fine), curing powder coat, melting low temperature metals, heating plastics for forming, finding out who swiped my last Twinky etc. It still needs a lot tighter temperature control (pyrometer probe + microprocessor?) but I've learned how to get around the bang-bang method it uses now by observation and appropriately inappropriate language skills.

By the way, Marv, even used treadmills usually have good motors & controllers. They wind up in thrift shops because the owners discovered that even walking can be too much like work. 

BEst regards,

Kludge


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## raym 11 (Dec 9, 2008)

Right on Kuldge, my 9" Southbend is driven by a Sal Army DC treadmill motor and controller. Will never go back to original drive, cause I have stocked up on spares from simular sources.

Ray M


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## Kludge (Dec 9, 2008)

ElGringo  said:
			
		

> Right on Kuldge, my 9" Southbend is driven by a Sal Army DC treadmill motor and controller.



Goodwill et al have been very light in treadmills all year so I'm waiting patiently for the post-Christmas period when things arrive in vast quantities because of "upgrades" or the aforementioned discovery involving work. The gym where I'm getting a membership has treadmills so I may ask if they have any of them that have decent motors & controllers but are otherwise beyond economical repair. 

Once I have one, it's going on my Taig. If I get two, the second one will go on the 6" (AA109, kit built or whatever) I don't have yet but shall one day (soon?).

Best regards,

Kludge


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## raym 11 (Dec 9, 2008)

Yea! I'm lookig for a small one for my Taig mill.


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## jack404 (Dec 10, 2008)

ElGringo  said:
			
		

> btw, any ideas on metal heat treating ovens on the cheap?
> 
> Ray M



Ray 

this is mine sorry for the lousy pics a few did not work 
its currently in a transport yard and needs a new sheet metal cover

this is the gas jet and control






this is the door ( yeah but its only gotta hold in the heat )






this is the best shot of the body it shows the rust and bricks






i built it a few brick at a time setting the fire brick mortar set between each row 
it was framed over a old 44 gallon drum with a side and the ends cut off.

once set start rolling the old drum up



the gas jet a furnace guy set up for me 

i have a good thermo couple and theres a rs232 connection that connects to the laptop and a wire back to the valve control to open or shut it 

its good to hold within 10 deg F at 400-1500 deg F

theres a 1/2 " shelf 2 brick high inside the oven

 the heat goes below this and the plate heats the top level to get a even heat

but i'm annealing and tempering awful hard and largish bits so i went a fit farther than most folks need

inside its 4' 10" long and 2 ' high from the heated plate


cheers 

jack

PS

as seen here IT WAS CHEAP TO MAKE 3x packets of kiln mortar 

kiln bricks fom a old factory site where the rubble had not ben removed (some steel came from there too!)

hardest part was carting the stuff home.. at night   :big: 

with a motorcycle ! ;D 

maybe $18 in cash money and 3 cases of my home brew in trade and a heap of scrounging for materials

i dont think i bought anything that was used on it besides the mortar the rest was industrial waste


my furnace mate rebult the jet from a throw away from a site

the controler for it came off a hot mix road building truck that had died long ago 
the board is a old 14.4 modem with a rs232 connection 
the software is freeware

if you want a themo couple thats not cheap ($60-$1000 OZ) but i traded 2 cases of home brew for one


it costs about 3-4 litres a hour depending on temp and pre mix 
if you wanna run at 300 deg it will do it but you have to fit a collar to the jet and "mud" this closed around the in-hole and let the collar vents control air so it will run steady at lower temps and 1-maybe 1.5 litres a hour

i use LPG its called here. its cheap (ish) too


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## shred (Dec 10, 2008)

ElGringo  said:
			
		

> Yea! I'm lookig for a small one for my Taig mill.


Surplus Center has a few left, but they're running out. I have 'em on my Taigs.

http://www.surpluscenter.com/item.asp?UID=2008121000082627&item=10-1783&catname=electric

$22+shipping. $30 more for a controller.

They started with several thousand and are now down to about 20, although it looks like they have another that's somewhat similar now.


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## raym 11 (Dec 10, 2008)

Thanks Jack but that one is more than I need. Very ingenious design. 

I'll have to do without and drink my homebrew  ;D 

I ordered that motor, Shred. I have a controller off of a 1 1/2 hp treadmill that I think will work 


Ray M


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## jack404 (Dec 10, 2008)

whats wrong with home brew?

 ;D


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## raym 11 (Dec 10, 2008)

Had no complaints from friends and neighbors about my brew

Mayby they could whip me up an oven so I don't cut them off. 

Ray M


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## Loose nut (Dec 14, 2008)

jack404  said:
			
		

> whats wrong with home brew?
> 
> ;D



Nothing, the best stuff is always home made, it's exactly what you want not what someone else wants to sell you and it's more fun to make then buy, well, not always .


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