Any industry-retail store should have replacement blades, but it depends on what kind of saw you has. Since certain blades are more popular and known verse other types of blades.
You can find bow saw replacement blades at hardware stores, home improvement stores, or online retailers that specialize in outdoor equipment and tools.
There is one site where you may be able to find a blade. =I've added the related link below.
Engineers refer to it as high speed steel.
I think a good store that sells tree pruner saw blades are probably either Lowe's or Home Depot. They usually have the best selection available out of everybody.
Diamond blades are mainly for cutting tiles.
You can find 10-inch dado blades for a table saw at hardware stores, woodworking supply stores, or online retailers that specialize in tools and equipment for woodworking.
Sears
Those types of blades and bits are mainly for cutting tiles and stone.
There are different types of saw blades available for cutting various materials, including wood, metal, and masonry. Some common types of saw blades include carbide-tipped blades for cutting wood, bi-metal blades for cutting metal, and diamond blades for cutting masonry. Each type of blade is designed to provide optimal cutting performance for specific materials.
There is a great new glossary for circular saw blades here: http://www.toolstoday.com/t-saw-blades-glossary.aspx The Toolstoday Saw Blade Glossary defines the many different saw blade terms that you need to know when you purchase, or start working with saw blades.
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Jig saw blades can be purchased at many locations. Some of these include Amazon, The Home Depot, MSC Direct, eBay, Bosch Tools, Sears, Walmart, KMart and many others.