The stroke sander is one of the machines that some may not have ever even seen before. Then there are some that will have seen one in the past but were not sure what it was for. Lets dip into what a stroke sander is and what its for. I will just touch the high points to give a general feel for the machine. Never hesitate to ask questions as its the best way to learn more.
There are two general types of stroke sander, I will give a little information on each.
The single belt stroke sander.
These tend to be lower cost and for the most part are smaller over all. These can often be found in their natural habitat of A wood working shop.
The twin belt stroke sander.
The twin belt tends to be a larger more robust machine over all. These machines tend to be found in metal shops or in fabrication environments. Why two belts? As an example, you can fit an 80 grit belt to sand down a weld seam, and fit a scotch brite belt to blend the finish. You can sand your weld and then move to the scotch brite to blend in just a few seconds. It cuts handling and it speeds up the process as a whole while producing a great finish.
What position do stroke sanders fill?
Stroke sanders are a jack of all trades. While you can do a simple task like put a finish on square tube, they can do much more. If you are fabricating parts, Doing weld seams on boxes? Fabricating doors? Do you need to put a finish on formed parts? Do you need to get some scratches out of your last piece of stainless material? They work well as that point between hand work and full on automation. The flexibility they bring to any shop will quickly make them a favorite.
Belt length matters.
In metal working the length of the abrasive belt matters. The longer the belt the more run time you will get between changes. This is one of the reasons driving the overall shape of a twin belt. Going to the A frame shape adds length to the abrasive belts vs the flat single belt. The larger frame also adds weight capacity to allow for working with a wider range of materials. The other additional effect is the ability to do longer parts like square tube due to the open frame.
The working table.
Another point is the working surface or "table" of a stroke sander. Most single belts will have a flat manual table due to them being mainly used in woodwork. With a twin belt machine you move to powered tables that are not simply flat in better machines. Having a fixture to hold parts that are more complex helps with many of the issues in finishing fabricated parts. These fixtures will pivot to store out of the way allowing for the full flat table to also be used very easily.
What are some parts that get done on a stroke sander?
Boxes, boxes and more boxes. Seriously finishing the welds on boxes and blending the finish is a super common application. The machines work incredibly well for this making it a very common application. Twin belt machine are just about required here due to the time they save and better finish they can produce.
Finishing square tube is another common application. The open frame means you can work with tube longer than the table. This method tends to put less heat into the part reducing the chance of warping versus other options.
How about doors? Fabricated doors are a common application. When doors are fabricated they tend to have low spots and a stroke sander works great at removing spot welds and finishing the uneven faces.
If you end up with defects in your material a stroke sander is great for removing them. The added plus of a twin belt in this case is the ability to do the second step and blend the finish. You cut the very last piece of stainless you had and it now has a big scratch in it. Toss it on the stroke sander and in no time its good as new, defect is sanded out and finish is blended in.
Final points.
Stroke sanders are much like WD40, the back of the can gives you a few suggestions on what its for but people have found far more uses than that. Stroke sanders are just a flexible way to finish so many things its near impossible to name them all. Flexibility and adaptability are the main traits they have that other machines will not. If you need to do a little of everything its tough to beat a good twin belt stroke sander. When many shops face a mixture of jobs and materials the twin belts tend to fit right in. They are the WD40 of finishing.
I hope this provided a few things that help to understand what a stroke sander is and what they are for. A good twin belt will get used as much as the gas pedal in your car. They are just that handy to have if you have the space for one.