# Doubt about straight pattern bits



## splintered (Feb 23, 2011)

I wonder if anybody can shed some light here. I'm trying to figure out what bits I need and have this newby doubt... Are all straight top bearing pattern bits able to flaten/carve the bottom of cavities besides working on the sides of the piece... or are there some that do and others that don't? 

This doubt came up while considering these bits
http://www.infinitytools.com/Top-Bearing-Pattern-Router-Bits/products/1056/
and seeing their "plunge point option". Thanks in advance


----------



## Cherryville Chuck (Sep 28, 2010)

You are looking for advice to make your choice simpler and what I am going to say will make it more complicated. I noticed an old post that came back to life in the last day or two. Someone badly cut the end of 2 fingers trying to cut a piece on a router table using a bottom template and top bearing. This made me realize that if you have a top bearing on a table setup, then you have to have all of the cutting edge up so that the bearing is above the table. For a router table, a bottom bearing is probably better so that the template is on top of the workpiece and there is no exposed cutter. You can't see what is happening but then the template is supposed to take care of that problem.
I don't know if this helped but I thought it was something worth considering.


----------



## Quillman (Aug 16, 2010)

3 pathway choices for a trimmer with a bearing on its shank.

A) 3 sided, 1 diameter (or more) pathway across the stock, dado e.g.
B) Shouldered edge cut, rabbet is classic and
C) Full thickness edge, wasting to templet, (a copy of the pattern).
Some examples (in plastic and the cut below it).


----------



## splintered (Feb 23, 2011)

Thanks Chuck, warnings are always welcome, as is Quillman break down of cuts.
However I'm still not sure if all bits in the link above, besides cutting along edges, are also able to cut bottom of cavities or only the ones described as "plunge point" can work/flaten also bottoms? thnaks


----------



## Quillman (Aug 16, 2010)

Some HSS and all Solid carbide straight bits can plunge without moving the router.
Most garden variety 2 fluted brazed-on carbide trimmers demand that you sweep the machine whilst plunging. So blind excavational work is possible with bottom cutting trimmers, exotic or ordinary. Don't sweep (move the router) whilst plunging (brazed-on carbide) and you will destroy its bottom cutting capability.
That won't kill its full thickness trim function but expect to burn stock on inside cuts.


----------



## bobj3 (Jan 17, 2006)

Hi

I can't think of a quicker way to wipe out router bits than use them the wrong way.

========


----------

