cope and stick woes

[mrFinpgh]

I am trying to validate my setup w/ a new cope and stick set from MLCS.  It's the shaker style 15 degree bevel set.

I've triple checked my dimensions and everything is square and flat.  Everytime I do a test piece, though, there is a notable gap.  Photos to illustrate below.

At first, I attributed it to my saw being just slightly off 90, but I've tuned that up since then.  Still, issues.

The tongue and groove is snug, so I don't think it's a question shimming.  I am careful to get my fence and the bearing in line using a machine rule.

Also, this isn't the first time I've done doors with cope and stick bits..  usually the fit is snug and gap-free. 

What else should I be looking at?  Is it possible I just have a bad set of bits?

Thanks,
adam

 

[Lincoln]

That 'looks' like it should pull up - is it a consistent gap all round, cause it looks like it in the pics?

 

[leakyroof]

What happens if you just kiss the end of the tongue with a cut to shorten it?
Still have a gap after that?,,, [scratch chin]

 

[Alanbach]

I would also try tapping the fence back just a bit so you can make sure that your fence adjustment is not impeding the bearing / bit from making a full depth groove.

 

[mrFinpgh]

That 'looks' like it should pull up - is it a consistent gap all round, cause it looks like it in the pics?

I think there is a shadow around the tenon, as the tenon is actually pressed up to the back of the groove.  There is more gap around the profile than the tenon and groove.

If I clamp it with some pressure, I can get it pretty close to tight on the face, but the back will open up and it would probably be out of plane.

 

[mrFinpgh]

I would also try tapping the fence back just a bit so you can make sure that your fence adjustment is not impeding the bearing / bit from making a full depth groove.

At the moment, the fence and bearing face are completely in the same plane. I'm not sure how I would accomplish what you're talking about without some issues doing the cope cuts. 

I use a push block that rides against the fence to support those cuts and back them up from blow out.  If the bearing was running proud of the fence, it seems like I'd run into an issue at the beginning and end of the cut.

 

[mrFinpgh]

What happens if you just kiss the end of the tongue with a cut to shorten it?
Still have a gap after that?,,, [scratch chin]

I'll break out a shooting board and see if that helps any.  Seems like that shouldn't be happening, though. if anything I'd expect a tiny gap between the end grain of the tenon and the bottom of the groove.

 

[Bob D.]

Maybe check the diameter of the two bearings. They should be the same.

But you would have noticed this when changing from one bit to the other
and checking alignment with the fence so maybe it's not a concern.

Just for grins try swapping the bearings between the two bits and see if it
makes a difference.

If you've checked the fence alignment after the bit swap then this won't make
a difference, but if you just changed bits and didn't check with the second bit
the bearing might be just a fraction behind the fence so your groove might not
be as deep as it should be. Unlikely maybe but since you've checked all the usual
possibilities it might be time to start considering the improbable.

 

[mrFinpgh]

I use a musclechuck, so i move the fence out of the way before switching bits from above.

I'll have to get a battery before I check, but looking at the diameter of the bearings seems logical.

I did try taking a bit off the tenon to see whether it allowed the joint to close up. That's not the cause of the issue : now there is more of a gap at the tenon and the profile.  I think it's the lower profile that appears to be holding the joint apart.  It seems like maybe the bits are not matched perfectly.

At this point, I'm considering:

1) See if MLCS can replace the set.
2) Just ditch the chamfer profile and do a domino joint.  I'm not sure how much the chamfer adds to a double frame and panel with bookmatched curly walnut panels anyways.  I just hate to be uncertain about whether I could make it work or not.