Why a "reverse"?

[John Miliunas]

OK, so my ignorance is floating to the top, but I just can't figure this one out. Router bits, molder cutters and shaper cutters are obviously designed and built to cut in one direction. Why then, do most shapers have a "reverse" on them? Even on a drill, where the bits are cut for one direction, I can understand the "reverse" to help back out of a hole, but why on a shaper? I'm stumped. HELP!:confused: :cool:

[David Eisan]

Easy,

With a router bit, there is only one way you can install it, with a shaper cutter, you can install it "upside down" requiring you to run the shaper in reverse.

Rather than running your panel on "top" of a panel bit and feeding right to left, some people like to power feed left to right with the material "under" the bit and the shaper in reverse.

David.

[John Miliunas]

Thanks David! You see there, it WAS a pretty ignorant question with a very simple answer. Like you referenced, I guess I was too much in the "router mode" to think of flipping the cutter. Makes sense. :cool:

[Tony Pearson]

This brings to mind a very important safety issue. We all become acustomed to working in one direction with routers....and in most cases shapers. However, when using a shaper with reverse. Be Sure and remember to reverse the feed direction A shaper throws a very mean punch.

:eek:

Tony

[Rob Russell]

Sorry Tony,

You generally don't reverse the feed on a shaper. The point of reversing a shaper is, indeed, so you can flip a shaper cutter upside down and trap the piece between the cutter and table. Most shops would also run the shaper in what's called a "climb cut" where the cutter rotation is in the same direction as the feed.

This is done in conjuction with a power feeder that keeps the stock from flying away and should never by tried by hand.

There are 2 big advantages to climb-cutting a piece and trapping something like a raised panel between the cutter and table.

1) Climb-cutting gives a better finish with less tearout.
2) Trapping the piece gives a dead even tongue for raised panels and eliminates any uneven spots in the panel edge.

Rob

[Tony Pearson]

Rob, thanks for your response. I stand erectly corrected Thanks for the "climb cut description" I think you will agree with me on one issue......THINK SAFETY FIRST

Thanks again, Tony

[Rob Russell]

Tony,

You're dead on about safety and shapers. They're probably the most dangerous machine in the shop if you don't treat them with the respect they're due. There are really 3 big reasons that power feeders are used so widely on shapers.

1) Better cut - the stock feed rate and pressure of the piece against the shaper fence and table are consistent through the whole work piece.
2) Productivity - you can be grabbing the next piece as the current piece is being fed through/milled.
3) Safety - the shaper covers the cutter and keeps hands away from the cutter area.

To put things in perspective when it comes to the amount of momentum in a large cutter - I measured one of my cutter heads. It's a rebate cutterhead for milling rabbets on stock. It's about 6" in diameter, 2" tall and weighs 13-14 pounds. When that thing is spinning at 7500 rpm (with a high HP motor behind it) - the energy sorta doesn't compare to a saw blade. Think about hitting start with that on a machine and you really double and triple check things from a safety perspective.

I did, however, think of an occasion when you might reverse the rotational direction and feed "backwards" and that's when freehanding a piece. An example of this is if you had a cathedral raised panel that you were milling. The curved top profile is typically milled by clamping the workpiece into a big jig with handles and the piece is then hand-shaped. The jig allows you to keep the workpiece under control and keep your hands well away from the cutter head.

Rob