DF500 Through Tenon Mortise Plunge Strain?

[onocoffee]

I was using the DF500 the other day to make through tenon mortises with the 5mm bit. The side panel is 12mm thick and I set the plunge to the full depth of 28mm. The plunge is going into pine.

Everything goes smoothly until I get to the deepest part of the plunge. I feel like there's a couple more millimeters to go but I hear the bit and motor starting to strain. Concerned that I really don't know what I'm doing and might snap the bit, I back off and plunge no further. I needed to plunge 12 mortises and all of them had the similar strain at the deepest part of the plunge.

There's still more depth to plunge on the DF500 and when the tenons are installed, they are about 2mm proud of the surface.

Is it a build-up of saw dust below the tip of the bit that is causing the blockage? Or something else? I'd just like to understand what's happening better.

Thanks - and Happy New Year!

 

[Vtshopdog]

You’re probably bottoming out the cutter portion of the 5mm bit and hitting the tapered area where diameter increases to thread on to the machine.

Actual cutter length on my 5mm is shorter than on the larger bits. Take the tool and fully compress the fence with the 5 installed and you’ll see what’s happening.

Good job noticing the tool straining. 

 

[Michael Kellough]

Beat me to it…I’ll just add, you can finish the mortise with a 5mm drill bit or just shorter he Domino.

 

[ChuckM]

The reinforced shoulder on the 5mm cutter rubbing the mortise's opening was causing the strain. The 6mm cutter, e.g., doesn't have the raised shoulder.

A potential (and faster) fix (provided the 1mm difference is not detrimental to the project) is to remill everything with a 6mm cutter.

 

[onocoffee]

Thank you guys for the lesson. The lack of depth for this was no problem, I just used a hand saw to cut off the excess and sanded it smooth.

But it's good to know what's happening in case I want to make changes to the approach in the future. Noted on the chisel clean up and replunging with 6mm.

 

[ChuckM]

Too late now, but instead of trimming the tenons flush and sanding, it would have been a lot faster to bandsaw the tenons a little shorter before gluing and hammering them home.

 

[onocoffee]

[member=57948]ChuckS[/member] Band saw? Good point. I'll remember that!