Setting Up and Using a Whiteside Lock Miter Bit

For the purposes of this tutorial, we used a Whiteside 3360 lock miter bit which is good for panel thickness ranging from 1/2″ to 1-1/4″. For smaller panels such as those used in a 1/2″ drawer box, the Whiteside 3362 is recommended and can accommodate stock from 1/2″ to 3/4″. You can buy either of them on our website

Safety First: The lock miter bit is probably the heaviest and possibly largest router bit you’ll ever use. Make sure you slow your router down to 10,000-12,000 RPM to avoid any chance of injury. If you do not have a variable speed router, please do not use this bit. A router table is also a must, do not try to hand hold the router while using a lock miter bit.

Now that’s out of the way, let’s move on.

Long corner joints such as those on columns, posts and such are best done with miter joints. The Lock Miter bit creates a perfect 45 degree angle, and the integral tongue and groove aligns the joint, holding the parts square during clamping.

It is a highly useful bit, but the set up can be tricky, and many woodworkers are put off by that. Learn here how to quickly get the setting close and adjust for a perfect fit in just a few minutes.

The set up for the joint is directly dependant on the thickness of the stock, so be sure that all your parts are milled at the same time. Also, when prepping your stock, cut a piece for each profile about 4″ too long that way you can use the cutoff as a setup block for future projects. But again, stock thickness is directly related to setup so the setup blocks would have to match the thickness of the new project material.

One half of the joint is run flat on the router table, and the other standing tight against the fence. For clarity, the vertical parts here have been painted black on the ends. To get the initial set up quite close, use your stock as a gauge. When the stock is lying flat or face down on the router table, it should be centered on the bit. The stock is also a thickness gauge where the bit should protrude from the fence a distance equal to the thickness of the stock.

Ignore the tongue and groove, set the bit height and fence depth as instructed above. Make a test cut of both joints and see how they fit.

The first thing to look for is that the bit is cutting the entire edge of the part. Be sure also that it is not cutting too deep and removing any of the face of the part.

The part should have a clean knife edge on the outer face.

Dry fit the two samples.

Here the set up is slightly off.

The part face down on the table (light) over hangs the part with it’s face against the fence or edge on the router table (dark). The bit is too low in the table, but simply raising it would cut into the face of the table part. So in this case, the bit needs to be raised slightly, and the fence brought forward by the same amount. As more of the bit is exposed from the table, it needs to be covered by the fence. The opposite also holds true.

Once the bit is set, add featherboards or hold downs as needed and process all your parts.

Like most joinery, getting clean accurate cuts is critical. Start with good dust collection. Removing the chips from the cutting area greatly helps with clean cuts. Hold downs and featherboards help keep the parts tight to the table and fence, and push sticks or blocks keep your fingers well away from the big cutter.

A sacrificial fence can be used to create a zero clearance face that greatly reduces the chance of tear out.

Some material can be removed with a bevel cut on the table saw to minimize the stock removal.

Care must be taken not to pre-cut too much and remove the material needed to form the tongue.

One more item to keep in mind; because this bit will create very tight joints, there is no room for glue to squeeze out. Use thinned glue, spread lightly along the joint, to secure the seam.

The Lock Miter joint should be used any time a strong square attractive joint is needed. With small practice, it can be set up quickly and easily to speed your construction.


November 22, 2009 at 10:00 PM Leave a comment

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