I have an end grain cutting board (maple, walnut & purple heart). I want to flatten it with my cnc. I know everyone will say use a large flattening bit like the McFly, but mine is dull as heck and can’t get a replacement in a reasonable amount of time.
I do have 1/4 spiral bits. Up and down cut. Which should I use for flattening the cutting board? I know a 1/4 bit will take some time, but you have to work with what you have sometimes.
If you have a diamond stone take your inserts off and lay them flat with some water or diamond stone fluid and stroke them about 10 strokes per insert. Always do the same amount of strokes on each insert. They will be sharp. It is the edge that wears out and a fine or extra fine diamond stone will sharpen up carbide inserts. I do that on my carbide lathe tools and it works. Hopefully you already have a diamond card/stone. Being Christmas it is too late to get some but most of the carbide inserts are the same size and places like Rockler and/or Woodcraft will have them in stock or order from Amazon or other online retailer if you want to replace them. However a diamond stone will sharpen them right up. Just measure the outer diameter and the hole size and you can get generic ones cheap.
Out of curiosity how much flattening with the mcfly do you do before you need to rotate to new face on the rotatable inserts?
I would concur with guy on a diamond hone. Haven’t run my mcfly long enough to even think about sharpening ( not doing production) but have done the for other things
John
Unfortunately I don’t have a flattening bit that can be sharpened. It’s a crappy one I got when I 1st ordered my machine. I’m stuck with 1/4 bits as of now. Which will work, just take a lot longer.
If you have a diamond stone you can stroke on each flat face of a carbide and/or HHS bit and sharpen it. Sorry you mentioned McFly and I assumed a carbide insert bit. The diamond stone works on regular end mills. Just sharpen the tip.
Also worth mentioning that sharpening a bit used for facing is low risk/high reward. (especially if the tool is going to be trashed anyway 
)
This is one of the few tools with a nice large and simple geometry where the dimensions aren’t terribly critical. Give it a shot and if you don’t have a diamond stone, pick one up before tossing your facing tool (even if you get a nicer carbide insert facing tool…those inserts can be sharpened easily too!)