I should probably first qualify a comment I made earlier - "I've experienced what you're describing many times." Yes, for sure, but it's not been frequent across the 10,000+ corner joints that I've routed with Incra systems. I'd say that significant self-feeding or minor chip out only affects about 5% of the pin cuts.
This thread covers two mostly separate matters. They come up about twice a year in conversations with customers and they haven't posed problems for me personally, but I've been thinking of a few other possibilities since my conversation with Wayne beyond what's already been discussed.
Using a really sharp bit, tear out or chip out is largely a function of grain direction near the end of the board, as has been mentioned. I've never needed to deviate from the normal method, but if tear out is severe or consistent, you can leave the pin board a little long, rout the grooves between the pins longer to match, then cut the board to final length, taking the damaged end grain with it.
A leader board could be difficult to secure...I'd be wary of trying it. Also, I don't think it's the situation here, but cutting into edge grain will produce heinous tear out...I occasionally chat with customers want to join boards on their long edges instead of ends.
If a bit/lumber combination tends to self-feed, there are a few things I'd recommend to minimize it in addition to what was quoted above -
- If you're using a plunge router, make sure the plunge is locked up tight. The motor bouncing around on its posts will pull the lumber right out of your hands (I forgot once). If you have a midsize router that came with two bases, use the fixed base. The plunge bases on a number of these routers aren't stable enough for router table use.
- Wax the heck out of both the table top and the fence surface to get the best feed control, slicker is better. The enemy is static friction...this is resistance to sliding while stationary, then suddenly breaking, free producing a rapid jerk/stop/jerk motion.
- More RPM is usually better, but I wouldn't say "always".
If you keep the lumber going straight if it wants to self-feed, it won't affect the accuracy of the cut. A few suggestions -
- Keep your right hand on the push block and your left hand near the trailing end of the board, keeping the trailing edge in solid contact with the fence. This helps counteract the clockwise rotation that bit is trying to produce. Boards less than 5" long have the greatest tendency to dip into the router bit opening, longer boards are easier.
- I've never tried this, but you could install a pair of zero clearance sub fences as described in the Wonder Fence manual, which can be found on either of our websites. Closing off the space between the bit and fence would dramatically reduce the boards ability to dip into the bit opening on through dovetails, and the sub fence immediately above the bit would completely eliminate this possibility on half blind dovetails. There's no need to have the right angle fixture hooked over the fence...it will track fine along the sub fence with some pressure inward/downward on the body (this is smart technique, regardless)
- Again, wax the snot out of both the table and fence, slicker is better. If you've seen our demos at woodworking shows, we keep our tables waxed up like a sheet of ice.
Let me know if I can clarify or address any questions - 888.804.6272 xt 4. Please e-mail me directly or call vs a PM through the forum...
Field Operations Manager
Taylor Design Group, Inc
1605 Crescent Circle, #400
Carrollton, TX 75006
Phone: 888.804.6272, ext. 4
1 317 287 0340 (international)
E-mail: [email protected]