Flying Dutchman makes a Spiral Reverse. (SPREV) I have not used them. I almost always use a scrap piece under the ply I am cutting when using spirals. Here is some information on spirals I posted in Feb 2017:
Posted February 9, 2017 (edited)
If My memory is correct and if I understand what I just looked up:
Spiral Blades came first and are pretty much a flat blade that has been twisted into a spiral. Pretty much needed to use pliers to un-twist the end to get it to stay in the holders. hard to control - hard to get into holder but the best there was at the time.
The Flat End Spiral was brought out (The flat end spiral - as stated above is not really flat. It is close to half spiral and half flat making it easier to get ready to place in the holders.)
To bring about better control, The New Spiral Blade was developed several years ago and has teeth on both sides of the blade - a flat blade with teeth on both sides and twisted into a spiral. better control. Still has some twist on the ends. Sometimes I flatten the ends some and sometimes I put them in right out of the package.
Spiral Reverse is latest design of the spiral. - spiral blades for all around cutting with reverse teeth on the bottom for a close to sand free finish.