Thread: Best way to cut slots cross grain at a 15º angle

I think both the Forrest and Freud 3/8 box joint blade sets can be shimmed to 11 mm.
these blades would give you an angled bottom to the slot.
Note, I know these blades can be shimmed but don't know bu=y how much.


another approach is -- can you change the insert material to a dimension that would fit a slightly narrower slot


Then CMT make 11.1 and 11 mm straight bits
11 mm is part number 911.011.11, cutting length 20 mm -- but you will need an 8 mm collet.
11.1 mm is part number 812.611.11, cutting length 31.7 mm -- and is a 1/2" shank

Not really an answer but, could help with production.
Is there a chance of doing the slots while the timber is wider and then ripping to width...

Originally Posted by Wynterplace

I have to go and file out the stepping created by the blade kerf at the bottom of the slots

Why? Will anyone ever notice it?

If you want an easy way to clean the bottom, thickness a strip of timber to be a slip fit in the groove and double-sided-tape sandpaper to the edge. The groove will hold the sanding block square to the sides and, if you line a bunch up, you won't roll the corners as you enter-exit.

Originally Posted by Wynterplace

Would I be better off using a jig on the table mounted router that holds the timber at a 15º angle and having a custom 11mm cutter machined to do the slots in one pass? Or should I get a dado stack (i'm using a Makita MLT100), and make a new sled to accomodate the stack at a 15º angle instead? Or is there a better way to do it that i'm not seeing?

If you don't have 1000's of these to make, and an extra hour or two "once" is no big deal to your bottom line. I would just make the jig you spoke of for the router table, but make it for the tablesaw and use a flat top blade set at 90° to make the 4 passes. that way you don't need to buy custom tooling or a dado stack etc etc and you "get it done"

If you do a lot of these I'd be going the router table jig method with a downcut bit. If you're able to set your fence accurately (or build the necessary accuracy in to the jig) and you have a sacrificial bit of timber on either side of your stock you'll get a result that requires no finishing. You can use any bit 3/8" dia. or less and just do two passes. The main thing to watch out for is stock control because any of the larger dia. downcut bits will tend to lift the stock off the table.

Will your saw accept a dado stack? Groove bottom finish using most dado stacks is far from 'perfect' anyway.

unless the jig is pretty sophisticated -- I'm thinking a jig that incorporates a sliding carriage -- any method that requires two or more passes will result in a stepped slot, which when smoothed out will have a flat rather than angled bottom.
It's a matter of geometry. the cutter cuts to the same depth each pass, while what the OP wants (if doing more than one pass) is a cut that varies in depth with each pass.

The jig will be nothing more than an 15° angled base which loosely sits in a standard crosscut fence or on a sliding table. The purpose of the jig is to incline the work piece 15° so that when the blade is at 90°, you can create the 15° angled slots. When making multiple passes, you slide the work piece AND the 15° angled base together as one. The blade doesn't raise or lower, the distance from the tablesaw surface to the workpiece remains constant. It is exactly like running a wide tenon requiring multiple passes with a dado stack except that the workpiece is on an incline instead of laying flat on the tablesaw surface. The base of the slot will be at 15° in relation to the long faces of the workpiece, exactly how Wynterplace has drawn it.

If doing many of these I'd make a jig to angle the router in the table.

Sent from my SM-G935F using Tapatalk

Guide the router between two runners, and tilt it 15 degrees by adding a spacer under one side. There is no need to be make it more complicated than this. No need for a wedged base - just lift up one side of the router to the desired height for the wanted angle (spacer held on with double-side tape or hot glue).

Now groove one side, turn the router and groove the other side, and then slice the board up to make the feet.

This will leave an angled base in the slot. Perhaps this does not matter. If it does, then level with a router plane.

Regards from Perth

Derek

https://www.timbecon.com.au/sawing/f...-dado-saw-blad

Originally Posted by China

https://www.timbecon.com.au/sawing/f...-dado-saw-blad

That link doesn't work for me. Wynterplace seems to have disappeared from the thread, maybe he's worked out a solution and is busy making them.

If I had that problem and was making a few, and assuming they are all identical, I would taper cut some scrap to 15 degrees laminate it into a router sub base make a dedicated fence, clamp the work together and rout the channels by hand. Shouldn't take too long to make that jig. Really depends on how many, any variations between pieces and how you prefer to tackle it.

2c...+gst..

For a small batch I think a SCMS with a depth of cut stop might be an option.

Good Morning Wynterplace

Perhaps you could reverse your work order and add a twist:

• Leave planks whole and flatten one face only on the jointer,
• Then cut the slots in the dressed face on the table saw with the blade tilted - this will leave a "saw tooth" bottom to the trenches.
• Flatten the bottom of the trenches with a shoulder plane, using trench sides as reference surface.
• Then rip the work to size and smooth it, as you have been doing.

This is a good small shoulder plane:






Plane, Shoulder, Miniature, Veritas, 6mm Wide x 62mm Long, A2 Blade, 50gms, #05P80.01
Plane, Shoulder, Miniature, Veritas, 6mm Wide x 62mm Long, A2 Blade, 50gms, #05P80.01 AU$69.88

More Details...


If your trenches are a little wider at 12 mm or half-inch then there are many more shoulder planes available. HNT Gordon, Veritas, Lie Nielsen and possibly Luban come to mind.


Cheers

Graeme