Up spiral.. Down spiral.. What the heck?

IIRC, the down spiral is used when cutting something like laminate where you want to minimize chipping.

todd

Got it..!! Thank you very much.. Now it makes sense..

The idea behind down spiral is to reduce chipout on the surface. Particularly good for plywood. These spiral bits are direct copies of two flute metal cutting end mills. End mills are what I use. They are less expensive (about $25.00 to $30.00 dollars for a 1/2" end mill as opposed to $50.00 to $60.00 for a spiral router bit) and work great. The only real advantage to the spiral router bit is shank size. They are ground to fit the average router. The most common sizes in spiral router bits are 1/4, 3/8, and 1/2 and are ground to fit either a 1/4 or 1/2 collet. With end mills, about the only thing available to fit a 1/4 collet is a 1/4 cutter. 3/8 has a 3/8 shank. 1/2 is of course 1/2 shank. In between sizes have the next size larger standard shank. Example: a 5/16 end mill will have a 3/8 shank. Most routers have 1/4 and 1/2 collets. If there is a 3/8 collet available for your router (there is for PC routers), you have the size range covered from

Interesting.. Thanks for cost saving tip..

Keep in mid that if the router is mounted in a table, the down spiral is now an up spiral when looking at it so plan your cuts accordingly. Up spiral bits will help remove material better when cutting a groove too.