Tuesday, December 27, 2011

Utility of a Router Bearing Kit

I'm finishing up a gift box for my mom's Christmas present.  Yes, I know, today is the 27th... anyway, I had to raise a small panel twice with a big honkin' 3.25" coving panel raising bit.  Those things generate a healthy amount of respect, I tell you.  But me fessing up to being way more frightened of a panel raiser than a rabbetting bit is not the topic of this post, if nonetheless true :)

A reader brought up a valid concern: the photos below were all taken the day after I raised the panel; they are staged photos to show how I used bearings to accomplish the panel and to highlight a caution.  Use push pads, stock holders or even a coping sled to keep yourself safe from the bit...

I raised the panel twice with a cove to create a unique shape; this is for the top of her gift.  As an aside, get creative with the profiles you have as "stacking" them can make unique profiles you don't see elsewhere; this is especially useful for boxes.  In my case, this stacking of a simple cove panel profile mimiks the "linen fold" bit I used for other parts of the box.

To accomplish this profile, I had to change the bearing on the bit to set the inside shoulder distance from the edge. The two bearings right in front of the panel were the keys.  I had these bearings in a Slot Cutter Survival Kit from Eagle America.  Panel raisers stack their cutters on a shank used for stacking slot cutters, which is why this bearing set was so useful.  Note that it wouldn't be useful to replace the bearing on the top of your rabbetting bit as that is a different inside diameter (there are top-bearing kits for that), but that said, I grabbed a few of those bearings as well and converted a rabbetting bit I got in a set to a 3/8" rabbet from 1/2" to compliment the 1/2" I already had.  Very useful.

Back to the panel cutter, between the cove profile and the back-cutter was a bearing that would ride on your stock to set the standard profile.  That's the bearing I swapped out for these larger diameter bearings.  I also left off the backcutter as I didn't want that.  The problem, though, with removing the backcutter is that you reveal a section of the shank that isn't threaded... so how can you lock down the cove cutter?

For that, I stacked bearings and a thin shim between them (less wear on the bearings) to get to the threaded part.

The photo shows how, when I had the larger diameter bearing, I had a smaller diameter bearing under it simply as filler.  The bearing kit, though, does have a variety of shims; I just opted to use another bearing rather than stack 6 or more shims.

This photo partly shows something I want to point out as a caution when stacking bearings and shims: as I cut this panel, I was constantly making passes and raising the bit a hair (small panel, big bit, hard Maple end-grain...)  Imagine the above picture as the bit goes higher. At a point, I'd be riding on the narrow edge of the bearing and it would be easy to get the stock underneath the bearing.  If I'm lucky, I maintain control but dig into my stock in ways that glue and sawdust won't fix.  A more likely scenario is that it catches the stock and throws it.  The hand nearest the starter pin might get hit like a kickback, but the other hand might get carried with the board into the bit.  So pay attention to the registration of the bearing on your stock.  Without stacking bearings (using the bit "as is"), there would be a back cutter on the top and a bearing sandwiched between them; the case can happen there, too, if you raise the cove cutter (pattern cutter) high enough to get the bearing about the panel.

I point this out because the bazillion cycles of raise-bit-route-panel can get you into inattentive repetition and you might move the bearing up or down off a safe registration on the stock.

I bought that slot cutter survival kit with a slot-cutter set, but I swear I've used it more often to modify other stacked bits than my slot cutters.  Highly recommend finding a kit like this and having it on hand.  Also recommend a few of the top bearings although usually you can steal one from another bit for a particular operation.


  • Brian said...

    Great looking piece... Do you have a pic of the whole project?

  • HalfInchShy said...

    Uhm, not yet :) I just finished applying the first coat of finish to the main box; the panel for the lid (the panel in this blog entry) will have enough coats to be mounted inside its frame tomorrow night. Still carving the handle, though. It's a Christmas present for my mom; I gave it to her as completed pieces that weren't assembled so she had fun putting the puzzle together. Now, I need to put a better effort in just completing it!! Pictures and a video to follow!