Daily Slideshow: Does Your Shop Need an Oven?

Big Square Tool

Like a paint booth or wash tank, you can get by without an oven sitting around taking up space in your shop, but once you do make space, you'll keep finding new uses for it with each passing project. Before we get to a few of those uses, we should probably talk about what kind of oven you'll be wanting for automotive-related projects. We suggest a free one. One that was made before ovens came with energy efficiency stickers, but not so long ago that you can't buy a replacement element for it when you burn yours out or drop something heavy on it. The condition of the top burners doesn't matter because you won't be using them. An oven that won't electrocute you is preferable as well.

Once you procure the oven, and find a safe spot for it, away from flammables and with ample electrical power, you'll probably want to make a couple of modifications to your new toy. To even out the heat inside it, and also to have a place to put heavier or larger parts, it's advisable to buy a sheet of fireproof board to separate the burner from the main interior area of the oven. The board shouldn't fit tight, so that heat can flow around it, but it should shield the rest of the oven from heat directly radiating from the burner. You might want to support it with a brick or two. Larger items won't fit inside the oven with the door closed, so to accommodate those items, build a simple insulated cover to sit on top of the open door to double the oven's size. A framework of angle iron, covered in sheet steel or aluminum, and insulated with fiberglass insulation will do the job nicely. Now that you're appliance-equipped, on to the fun stuff.

Bearing Removal

Some manufacturers never position ball or roller bearings inside blind holes, i.e. inside of a part or casting that has only one open side, but they aren't all that courteous. And even in situations when a bearing or shaft can be pressed out, a little heat can help ease that process—especially since not every shop has a press or a huge selection of specialized bearing pullers. Heat is even more valuable when you need to extract a bearing, bushing or shaft from something old and aluminum, or older and made from pot metal. A particularly neat trick is to heat up soft metal castings that hold a bearing—not so hot that it would distort the metal, a couple hundred degrees Fahrenheit is enough—then, wearing gloves, slap the casting down onto a piece of wood, and the bearing will pop right out. Help from heat always beats pounding or prying parts out when it comes to preventing damage.

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Powder Coating

Since it looks like powder coating isn't going to lose its popularity any time soon, and since you now have an oven in your shop, you might as well make the technique in-house. A number of inexpensive powder coating kits are available that are easy to use and give good results, and they all require heat to cure the coated parts. The curing process is finicky when it comes to temperature, so it's essential that you have an accurate way to measure the actual temperature inside your oven—don't trust the dial! Like anything paint-related, it takes practice to get the hang of it, so try the process out on some throwaway parts first. Once you have it down you'll be coating things you never thought to coat before. Sorry, but wheels are likely too big and too difficult to fit in your new shop oven so you'll probably still have to farm those out.

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Wrinkle Finish

Know what else needs to be heat-cured? Right, partly painted with wrinkle finish—sometimes called crackle finish—paint. As with powder coating, it takes a bit of practice to get the system down, so practice on expendable parts first, or just go into it keeping in mind the very real possibility that you'll end up stripping off your first few attempts. Unlike powder coating, wrinkle painting is a bit of a black art—balancing the number and thickness of coats with the temperature and duration of curing is a skill, but it's like a magic trick once you've acquired it.

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Parts Prep

When working on old metal especially, small cracks, pits, and fissures are a part of the landscape. Before bonding or welding cracks, or before painting especially porous pieces, they must, of course, be completely clean and free of oily contaminants. Often, merely washing parts isn't sufficient to remove all those contaminants. Heating old castings make oil more viscous and coax it out of those hard to clean spots. If you are getting messed up welds, or fish-eyes when painting, try heating up the part in question and you may see the problem come oozing out.

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Press-in Prep

Another situation where heating an entire part comes in handy is when pressing parts into castings, especially aluminum castings. Heating a casting easily and evenly expands its dimensions, and makes size-on-size or press-fit installations possible. Not all engine blocks are aluminum, and not all will fit in your shop oven, but heating up aluminum blocks for press-in cylinder liners is a time-honored technique in some applications, as is heating cylinder heads for press-in valve guides. 

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Weld Prep

Another technique as old as time, or at least as old as welding, is preheating parts that need to be welded. Welding large parts—again, especially aluminum castings—is difficult because the pieces act like huge heat sinks and suck heat away from the weld. Heating the piece up immediately before welding, and wrapping the part in a heat blanket while welding, will make for nicer results.

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Stud Removal

While we're still heating up castings—we said there would be different uses for the oven, we didn't say how different—let's use that heat to take things out, rather than put them in. Torches are great for freeing stuck bolts and other parts you are just going to replace, but some torches are too hot for castings, and others, like butane torches, are too cold. Too much heat will distort, weaken, or crack some castings, and others castings will either just not heat up, or not hold the heat where you want it. You can't bake a turkey by holding a torch to its wing. Heating up a whole piece when you want to remove a stud will save the casting's internal threads, and will break the bond created by chemical threadlockers.

We're sure there are other uses we haven't mentioned—if you have one jump in and post it in comments. Now to the fridge for that beer/Evian.

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