How to trim these

[Bope]

I use dovetail keys in some trunks I make. My problem always comes at the trimming time. I use a flush cut saw as seen in picture 2. I lightly hold a finger on the back side of the saw when trimming to try to keep the saw flat. The problems I run into is with no set in the saw it starts to bind around half way through. Also there are always a couple where the saw digs into the wood. Thirdly the center keys are difficult to get to. There is not enough space between the keys to get the saw flat on the wood. I don't mind the keys a little proud after trimming. Using the ROS to get them flush is easy. Any suggestions?

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[KLaz]

If you are having problems gouging the work piece with the saw, use something to protect the surface.  Blue tape, sand paper or something else.

Mike Pekovich uses sand paper when cutting dowels.  Here is a YT video showing the same principle....

Flush cutting dowels

Even though your situation is a slightly different than dowels, same concept applies.

I find it helps to keep working the saw around the piece to be cut rather than cut from one direction.

In your case you'll obviously start at the outer most key and work your way down.

[Bill Wilson]

When using a flush cut saw, I sometimes put a couple layers of painter's tape on the wood to help protect against scratches.

[Splinter Puller]

I use my oscillating wide belt sander to quickly flush off dovetails like that.  I good example of having an overpowered tool makes a complicated task trivial.

[Alan S]

Do you have a bandsaw?  That works well with the blade cutting along the corner.  If you don't want to cut freehand, a short block as a fence can register the side without extending far enough to interfere with the splines.  

With a bit more preparation, you can use a tablesaw.  For that, you'd use both a supplementary fence clamped to the fence with space under it for the splines, and a board clamped down onto the table, allowing you to run the stock on that, with a gap to allow the splines to extend past the blade and under the other fence.  You just turn on the saw, turn the box so one side is guided by each fence in the corner formed by the two adjunct fences, and slide past the blade to cut off splines.  8 quick passes and you're done.  The fences prevent cutting too deeply.

If you want to do it by hand, the first question is whether you can cut that length without your saw binding in other stock.  If so, you need to work on technique, perhaps by simply trying to cut a little away from the face of the box.  If the saw does bind, you could use a chisel to remove stock, allowing you to restart the cut.

[jteneyck]

I use a regular Japanese saw for things like that, and put a layer or two of blue tape on the side.  Cuts close and doesn't bind.  

John

[Cooler]

If you are using the blue tape then it should be OK to lube the saw blade with either paraffin wax or bar soap.  Rub the wax on the saw on both sides of the blade to make sawing easier.  

Or get a specially designed product from Rockler.

http://www.rockler.com/blade-lubricant-stick

[ez-duzit]

You are having trouble because you have chosen too small a saw for the job. I use a Gyocucho Razor saw similar to the bamboo-wrapped one in this link. Start at one edge and work your way through all the dovetails consecutively.
https://www.ebay.com/itm/Japan-Gyokucho-...2019717489

[Kreuzie]

Oscillating multi-tool. Put two or three (or more) layers of masking tape on the bottom surface of the blade (to keep it a bit proud of the surface). Sand flush with the ROS.

[giradman]

For dowels (so quite not the same), I use the Veritas flush cut saw below and on one side put a single thin layer of UHMW tape (like in the second pic) - works fine for me.  Dave