Stacking Shaper Cutters

Small, low-horsepower shapers struggle with large-radius tooling or stacked cutters. July 15, 2012

How big of a shaper would I need to stack the stile and rail cutters. Just regular 2 5/8 three quarter bore bits. I have a 5hp but would like to get a smaller one and leave the rail and stile cutters stacked in it. Would a 1 1/2 hp do it?

Forum Responses
(Solid Wood Machining Forum)
From contributor D:
I'd think a 1 1/2 hp should swing a 2 5/8 diameter cutter just fine, 2 5/8 radius not so much. I think most folks on this forum are using industrial grade machines, and 1 1/2 hp is getting down to the hobby horse realm. We have a couple dinky shapers with dedicated 1/2" rabbeting cutters on them that have been running for 15 years without a hiccup. Depends what you expect out of them.

From contributor F:
Personally I'd use the 5hp for the stacked cutters and upgrade to a bigger shaper for your other stuff. My concern would be shaft flex. Generally speaking your smaller 1-1/2 hp shapers are as mentioned more the foray of hobby crowd. As such they aren't necessarily built to work like the big boy shapers are. With the spindle being a 3/4", (which is more than adequate for a single cutter), I'd be worried about flexing under load once you start stacking cutter sets on. I'd also worry about burning out the underpowered motor. Of course this all depends on how much work you’re sending through.

A 3-5hp machine should be more than adequate for cope and stick cuts and assuming it's a decent quality machine should work ok for stacking. These days the cost of a used Powermatic 26/27 shaper is low. I'd at least consider going that route.

From contributor G:
If it has a 3/4" spindle it will work fine.

From contributor U:
I agree with what has already been said about your shaper being on the small side for stacking. If you are going to stack for now and until you get a bigger shaper put the cutter that will be under the most load on the bottom, and the one with the least load on top. That may help eliminate some flexing of the spindle.