CLASSES

Bellow is a sample of the course description and syllabus for a class. This class is available as well as any custom class you want. Let me know and I will write you up a course description, and syllabus.

Check out our page on Parts Modification to see what all the fuss over Polishing is all about.

 

Polishing parts 101

Course description:

An introductory class on bicycle parts polishing.

This course will be one to two hours, including theory and lab. The shop will stay open for another hour for supervised lab time if you wish to practice polishing your own parts. We can use your parts for class, or use parts we have laying around the shop.

Cost $100 all material provided

This class will cover why we buff out, or polish parts, identifying parts that are good candidates for polishing, why and why not: such as the difference between anodized alloy, raw alloy, and non alloy parts.

Basic theory of stripping existing finishes: Removing anodizing and sanding out small damage and scratches with chemicals, files and sandpaper, and mechanical de-burring wheels.

Different types of buff wheels and compounds and there uses. Stages of de-burring, rough buffing shine buffing and final buffing.

Syllabus

Identifying parts that are good candidates for polishing:

If you’re planning on putting all the time and effort into polishing out a part it’s a good idea to make sure that the part is in good working condition and the right fit for the project at hand. There are a million things that can go wrong with a part; it can be bent, bushing or tapers can be worn out, it can be cracked or have deep scratches that can’t be polished out without making the part so thin as to be too week for its intended use. A common example for this is polishing out scratches on a seat post. Not only can a thin wall seat post get week if you sand and polish out a percentage of its thickness to get rid of deep scratches, it can also change the size of the post and make it ill fitting in your frame.

Identifying the finish of the parts you intend to polish and what preparation they will need before polishing begins:

Steel:

Sometimes it can be difficult but you have to develop an eye for metals and metal finishes. The first step is to identify the metal at hand; is it Stainless, Steel/Cro-mo, or alloy? Is it chromed, painted, or anodized?

Generally you won’t be polishing cro-mo unless you’re prepping it for chrome plating, such as restoring hi end vintage bikes with handmade racks or if you are a frame builder making custom cro-mo racks. Cro-mo is magnetic with a strong force and will need to be chromed or painted to keep it from rusting. Cro-mo will rust so you may see red specks, or if you sand an area and get the area wet it will start to turn red.

Stainless:

Stainless is generally heavy compared to alloy, but weighs about the same as cro-mo. It is either non magnetic or has a weak magnetic force. It generally doesn’t rust when bare or raw, but may have some tiny red rust speckling if older and has been left out exposed to the elements for years.

Alloy:

Alloy is generally easy to identify, although it can be difficult to tell if it’s been anodized or polished, or is raw. Alloy is light, like really light. It has no magnetic force. Most modern medium to high end bike parts made over the last forty years have been made out of alloy. Low end parts are made out of chromed or painted steel, while much of the extremely high end modern parts may be made of carbon fiber, or alloy with a fake carbon wrap around it.

You will spend most of your polishing time on alloy bike parts. The trick is to identify the finish. You can only do this by identifying this by sight. Raw parts will be dull and unfinished with blemishes and casting marks. A smooth part with some sheen can either be polished or anodized. With bare alloy, or previously polished alloy there is no problem and it’s ready for the next step.

Anodized alloy will need to be stripped if you intend to polish it. If it’s already in good shape just a little old and dirty you can get an anodized alloy specific final buffing compound and just hand rub it out and get a pretty good or acceptable result. If you’re unsure if the part is anodized you can try polishing if for a few seconds. If nothing happens, or the metal starts to look mangy it’s anodized if the part is pretty scruffy and you need to polish it the anodizing will have to be stripped. This can be done chemically, or mechanically. It’s hard to sand through anodizing, and chemical stripping is recommended.

Stripping anodizing:

The easiest way to strip anodizing is to soak it in a chemical that will react to it and remove it. The best chemical I’ve found so far is a de-greaser called Grease Lightning. It works pretty quickly needing usually about 4 minutes of soak time. You will see the alloy bubble and turn black. The black will wipe or wash off after soaking. If the parts is mangy looking or not completely clean you can soak it for a few more minutes, or just get the last little bits of mange off with a little extra elbow grease during the polishing process, but this is no fun.

De-burring and sanding:

Once the metal is clean and bare it’s time to prepare it for polishing. This involves de-burring and sanding the part out to a fine enough sand-scratch for the polishing to be effective. A freshly anodized stripped part may be ready to go straight to polish if new. If it’s old and beat up it should go through the sanding possess like any scruffy old part.

De-burring:

The fastest and easiest way is to use a de-burring wheel. These are made by 3-M, expensive and well worth it. They are basically a thick more firm Scotch Bright on a wheel that can be attached to your buff motor. De-burring wheels are an all in one step that lets you run the part back and forth under it just like during the buff process and it will slowly remove material. You must keep the part moving as the wheel will remove a lot of material and can scoop out a lot of material making peaks and divots that will be hard to remove without making the part too thin. It is strong enough to remove casting marks and deep scratches and will allow you to skip all other filing and sanding steps.

Sanding:

The longer and harder way is to file and sand the part out. This starts with a medium to fine file and carefully files off high spots, and casting marks, and takes the metal down around the scratches. This effectively makes the metal thinner. You then move to coarse sandpaper wrapped around a file to remove the file scratches. You then move to finer and finer grits of sand paper wrapped around you file to keep removing the old sand scratches of each progressively finer and finer sandpaper. This needs to be done to at least 320 grit.

You cannot skip steps while sanding. You can’t go from a coarse file or sandpaper to a fine one as the fine one will not be coarse enough to remove the file scratches or coarser sandpaper scratches. The general rule of sandpaper is to skip no more than its number between sanding. For example if you start with 80 grit sandpaper the next finer grit should be no more than 160 grit, then 320 then 640. If you skip from 80 grit to 240 grit you will have to give it a lot of extra elbow grease to try and get rid of the 80 grit scratches, and you never really will. You will still see the scratches deep down no matter how shiny you get the metal.

Buff Motor wheels and compounds:

There are several different buff wheels with different stitching and stiffness characteristics. The same goes with the buffing compounds. The wheels are typically soft felt, the stiffer the wheel the coarser the buff compound it’s meant to be used with.

It’s essential to keep the wheels and compounds separated out. I recommend using a sharpie to label the cloth buff wheel as to what compound you use, and keep them in a Ziploc bag so they don’t get contaminated. It’s a bummer when you have all this work done and then some contamination puts a huge scratch in a part and you have to go back a few steps.

Compounds come in many names for many materials. You will work with three mainly for bike parts, especially alloy parts. A coarse for stainless and cro-mo, and medium for alloy, and a final white compound for shine.

Buffing techniques:

The most important thing to know is to only use the bottom half of the wheel. If you get to high on the wheel it’s likely the part can get caught and flung out of your hands. Most people hang soft material behind their buff motor to catch and keep from damaging any parts that get ripped out of your hands.

Buffing is very dirty and puts tons of particulates in the air and all over any other stuff you have in the room. Wear a respirator. In addition I use a full face shield and thick welding gloves as the parts get hot.

It’s important to move the part back and forth to keep any one area from getting more buffing than the rest so you don’t create divots. It’s generally good to polish down the long way of the part, but I will often buff in several directions to help hide scratches left by the sanding or even the coarser buff compounds, or just to be able to hit all the complex angles and tight spots on a part.

With any part I usually start with the courser stainless polish, even with alloy, to help get out the last sand scratches. With alloy I just do a light buff over the whole part. Then change the wheel and use the alloy compound, the alloy compound will be the work horse of most buffing work. You will spend more time with this really bringing out the shine of the part and letting you see your work. You will be able to see any coarse scratches or file marks left at this stage that will need to be gone back over with sanding or de-burring.

Once the part looks uniformly shiny and flat and scratch free you will go to the final wheel and compound. This compound is for shine. It doesn’t do any real work on its own and won’t take out any scratches. It only needs a few minutes evenly distributed over the part.

There are coarser and even finer compounds you will need for auto or jewelry work, but not for bike work.

Practice practice practice. You need to learn the feel for the motor, wheels, and compounds. Parts will fly out of your hands, or get caught up and hit the shaft and nuts of the buff motor adding more scratches. You will get to the final stage of polishing and see spots that needed to be taken out back at the first step, and you will have to go back and touch it up and re do the rest of the steps. You will need to get a good eye for how to nice the part needs to look before continuing on to the next step in order to avoid backpeddling.

Resources:

The Eastwood Company sells great buff motors, wheels and compounds.

Ebay is a great way to get deals on NOS de-burring wheels.

You tube has some great videos on buffing especially the Eastwood Company channel.