STAINLESS STEEL TIPS
Stainless steel love it or hate it?
There are a few things to know about this mysterious material, which will make life much easier.
Stainless steel has become the easy choice due to its corrosion resistant properties. The byproducts of metal plating have been proven to he harmful to human health. Poor disposal of plating bath solutions have allowed heavy metals to leach into groundwater. In many countries: cadmium, hexavalent, and trivalent chromium plating processes are now highly regulated. In many cases cadmium plate is only accessible to those in the aviation industry as international standards still require it.
Not requiring plating, stainless components can be produced more economically. This is why more and more of the parts we get are produced in stainless rather than chrome plated steel. Check out our article on chrome plating for more information behind why polished stainless is displacing chrome as king of the metal finishing world.
It seems like anyone and everyone has a different claim to being labelled the ‘inventor’ of stainless steel; from Britain, Germany, France, Poland, the U.S.A, and even Sweden. The UK claim seems to be well accepted. In 1913 Harry Brearley, of Sheffield, England created a steel with 12.8% chromium and 0.24% carbon, argued to be the first ever stainless steel. Metallurgist discovered that lowering the carbon content of steel and adding chromium gave the resulting metal special properties. Many of these properties have made the world we enjoy today possible. Such as the Delorean and time travel. Any Back to the Future fans out there?
There are now many types of stainless. Too many to mention in this article. As this subject pertains to motorcycle repair we will not give this much attention. Most likely you will encounter types 304/303. Type 304 is prone to hardening when cold worked. This is important to know if you plan to drill or thread a part made from stainless. Working with 303 is not bad as it’s composition is designed for machinability.
Click here to learn about the different types of stainless steel.
Most stainless steel is non-ferromagnetic. This means you can us a magnet to identify if a material is stainless. A magnet is not attracted to stainless steel due to the low carbon content. A few type of stainless are only slightly magnetic. There will be a noticeable difference when compared to a part made of mild carbon steel.
Challenges you might encounter:
- Drilling stainless sheet
- Galling of stainless fasteners
DRILLING STAINLESS: The right way to drill stainless with standard High Speed Steel (HSS) drill bits
Stainless is actually a relatively soft metal, at least in its initial state. What stainless tends to do is “work harden” fairly quickly. When the material is heated the chromium will harden the metal, and drilling at high speed creates a lot of heat. When stainless steel work hardens, it becomes very hard and extremely difficult to drill.
Start with a sharp drill and have it turning as slowly as your drill or drill press will allow. I set my drill press to its slowest speed or run my portable drill as slow as the trigger will allow.
You need to exert a lot of pressure on the drill bit—as much as it will bear. Small bits can be a challenge because pressure can cause them to bend and break, but you can put a lot of pressure on any drill bit that’s ¼in or larger. You will know if you are exerting enough pressure if a continuous spiral of material comes off the bit as it turns. Short drills also known as screw-machine and stub-length bits are great for this. They provide maximum rigidity for drilling straighter holes when using in a lathe or drill press.
You must keep the drill bit and stainless material cool. Machine shops have a continuous stream of lubricant that they spray onto the tip of the drill bit to both cool the drill bit and the stainless and to lubricate the cut. When you’re drilling stainless on a bike, in a boatyard or a home shop, that is not possible.
However, what you can do is regularly stop drilling and drip some oil onto the bit and in the hole. If you have a helper, you can also have them place a few drops on the bit as you are drilling to speed up the process.
Ideally, you want to use cutting oil, although motor oil or even WD-40 will do the trick. I even used olive oil once. The key is to stop often for cooling and to make sure there is plenty of oil.
If you follow these suggestions you can quickly drill stainless using a standard highspeed steel bit that you can buy in any hardware store. I recently drilled 16 quarter-inch holes through 3/16in stainless using a standard HSS bit and when I was done, the bit was still sharp and usable.
But Be Careful! While this procedure will allow you to drill stainless, you need to take some precautions. Drill bits can snap when you’re working on any material, but the high pressure used to drill stainless can lead to a drill bit snapping and sending metal shards toward your eyes. Everyone involved in or watching the drilling must wear safety glasses.
As the tip of the drill begins to come through the bottom of the hole, there is a tendency for the edge of the drill to snag the metal and spin the piece being drilled, sometimes with considerable force, which can cut you or even break bones. Always firmly clamp the piece you are drilling to a substantial work surface.
THREAD GALLING:
Thread galling is a common, yet seldom understood problem with threaded fasteners. Galling, often referred to as a cold-welding process, can occur when the surfaces of male and female threads are placed under heavy pressure.
Stainless steel fasteners are particularly susceptible to thread galling. During the tightening of the fastener, pressure builds between the contacting thread surfaces the increased friction can generate enough heat to fuse and seize the nut and bolt together.
Minor galling may cause only slight damage to the thread surface and the installer may still be able to remove the fastener. However, in severe cases galling can completely weld the nut and bolt together and prevent removal of the fastener. If the tightening process is continued once galling begins, the fastener may be twisted off or have its threads stripped.
Unfortunately, even with an understanding of the mechanism of galling, little is known on how to successfully control it. However, galling can be minimized with the following measures:
- Use a fastener or nut of a different material. IE Stainless bolt with a zinc plated steel nut. If this is not possible see the next option.
- Thread lubrication is one of the most effective measures to decrease the potential for galling. The lubricant reduces friction, which is a key element in thread galling. The operator must be aware that the torque-tension relationship will be altered with the use of lubrication. (This is why the stainless spoke kits are supplied with a container of anti-seize.)
- Heat contributes significantly to thread galling. Fastener installation alone generates friction and therefore heat. An increase in speed during installation increases the friction (heat) between the threads. Lowering the wrench speed during installation and removal can help avoid galling.