From Shopbot Wiki

When using a compression bit is it neccessary to cut through in one pass? If you do it in two passes do you still get the benefit of the down cut for the top of the piece?

Only if the first cut is deep enough to engage the down spiral. You might want to look at a mortising bit. It is similar to a compression but the upcut part is only a much smaller portion at the very bottom of the bit.
Onsrud has some compression bits in which the upcut portion is short enough that you can use the same bit for a 1/4" dado or a 3 pass cut on 3/4" goods and get clean cuts.

Why do I keep breaking compression bits?

With the compression spirals pay close attention to your chipload. We found that they are much more likely to break due to heat than a straight flute bit if your chipload is off.

Are there options to using a compression bit?

If I make multiple passes in melamine coated particle board, I use a down-cut spiral cutter for the first pass and an up-cut spiral for the final pass to minimize chipping.

Are compression bits good for everyone?

The extra cost for the compression cutters is mostly wasted if you don't have a spindle because the Porter Cable router just wasn't big enough to make a one-pass cut.
Personal tools