Tenons, Lap Joints, Bridle Joints.....stacked dado results

[George Farra]

Hi Everyone

I have a 6" Oshlun stacked dado set that I recently purchased with the intension that I wil use it to cut tenons (tenons to be mortised as well as bridle joints) and lap joints.

I'm not have much success getting flat cheeks. I have score marks from uneven blades in the stack I assume. Do these score marks really impact the joint itself? Should I clean them up with sandpaper wrapped around a block of wood? I don't have a shoulder plane....but this maybe a good reason to buy one

Alternatively I was also considering a horizontal router table which I know would give me a perfectly smooth tenon cheek but i would be limited by the length of the bit

TIA

George

[Bill White]

The cheeks will (should) have some roughness, but not excessive. You could have a blade out of whack. Is the rough surface identifyable to any of the stacked blades?
Bill

[Andy Sowers]

Are you by chance using shims? Every once in awhile the shims I have will get caught up in the arbor threads. This can cause one of the chippers to be slightly higher on one side causing a rough cut... at least that's what happens on my set (which is an 8" Freud set not Oshlun).

Andy

[Andrew Nemeth]

George,

Is it possible to post a few pictures of your results? I know it may be tough to show the detail you are talking about but it would be very helpful. Also, when I cut tenons like you describe, after I rough them out, I finalize the cut by creeping up on the blade and as the cheek is just barely floating over the blade I slide the workpiece perpendicuar to the blade. I creep forward another 1/16 of an inch and do the same thing. I repeat this process until I have worked all the way across the cheek. This process is a bit time consuming so it works best when you are just cutting a few tenons. If I am cutting a lot I now use a mortising jig on the table saw.

Hope this helps,

Andrew

[glenn bradley]

I agree that pics would help. It sounds like you are experiencing something beyond the "bat ears" that folks complain about. If you have ridges other than the outer edges, something is amiss. If you search here you will see plenty of threads where people are looking for a nice flat result from their dado stacks. The Freud SD508 looks like this.

[George Farra]

Correct guys, I'll get some pic snapped tonight or tomorrow. Interesting comment about the shims...that maybe my issue. It's almost like the chippers are not on the same plane as the 2 outer blades. I did have shims in the stack so maybe something got caught up on the arbor threads and put the 2 chippers out of whack.

[Prashun Patel]

Can't comment about yr dado pblms, but as for smoothing the cheeks:

A sandpaper block CAN work, but you have to support the infeed and outfeed of the joint to avoid rounding over.

A better approach is to use a shoulder plane.

On short joints like bridles and laps, you can even use a sharp chisel. Cut in from both sides to avoid blowing out the edges.

[Rod Sheridan]

Hi George, it can be a problem with the dado set itself. If the set isn't ground to the same diameter as a set, the individual chippers can be different diameters which results in grooves in the cut.

The table saw can also be the problem. A good saw arbour will have Acme threads that provide a wide flat support for the dado blades so that they are all in allignment.

An undersized arbour, or one with poorly cut threads can also produce this problem.

I have a Euro saw and it doesn't have an externally threaded arbour so the dado blades rest on a circular 30mm shaft. I've never had dado cuts so perfect, they look like they're made with a shaper cutter.

Your local saw shop should be able to measure your dado set and grind them to a consistent diameter for you.

Regards, Rod.