Knife Plate Slotter for Timber Framing

I originally had money in my bid to buy the Hema Chain Mortiser/Slot Cutter or Mafell Chain Mortiser/Slot Cutter for this timber framed, steel plate framed, barn in Portola Valley California. However, I had to lower may bid to get the job and I still needed a way of cutting the hidden 52 -- 3/8" x 8" deep steel knife plate slots in the timbers. I designed a slotter/mortise jig that I called the California Knife Plate Slotter - Mortiser for the 6x6 post and another jig that I called the Okie Knife Plate Slotter - Mortiser for the 5 1/2" x 9" GluLam Beams.

This is the first time I've assembled a roof structure without using any nails. Not even a nail to tack the exposed post or beams together. I had more problems with the bolt hole layout than making the knife plate slots.

Steel Knife Plates
Kerf Plates
Flitch Plates
Steel Plate Framing

California Knife Plate Slotter - Mortiser for the 6x6 post.

We slotted all of the 18-- 6x6 post in about 20 minutes with the California Knife Plate Slotter - Mortiser. However, we spent a lot more time on the countersink holes and thru bolt holes.

The chainsaw bar is attached to the jig with 3 -- 2 1/2" SDS screws thru the 1 3/4" x 2 9/16" piece of poplar wood. Then the 1 3/4" x 2 9/16" poplar wood is attached to the sliding box, 5 1/2" x 5 1/2", with about 6 -- 2 1/2" torque head screws. The 5 1/2" x 5 1/2" box was built with 1 1/8" thick poplar and assembled with the 2 1/2" torque head screws.

Picture with the 4 3/4" tall piece of wood that we used to align the top of the chain with the box. This allowed us to make a slot in the timber that was close to perpendicular with the end of the 6x6 timber. We would slot the 6" x 6" post with the chainsaw and then flip the post over to even out the slot in the post.

We used a 7/16" bell reamer drill bit to clean up the sides and bottom of the 8" deep slot. The 16" long steel knife plate are not perfectly flat-straight. Some of the knife plates have a 1/16" bend in the plate from the laser cut heat. So most of the slots we made were tapered from 1/2" to 7/16" to make the 3/8" steel knife plates fit correctly. We use shims in the slots on some of the knife plates, there weren't a tight fit.

The California Knife Plate Slotter - Mortiser has a depth gauge block in the jig. The knife plates are 16" long with 8" of the knife plate attached to each of the timbers. We set the depth block for an 8 1/4" deep slot. The ends of the steel knife plates should not touch the timber. We used the same depth gauge block for the 5 1/2" x 9" GluLam beams.

The structural plans were drawn with square edged steel knife plates. I got the ok from the structural engineer to chamfer or radius cut the ends of the knife plates, because chainsaws always have a rounded nose. After going thru this process of cutting the slots in timbers for steel knife plates, I think all hidden steel knife plates such be designed with chamfered or radius cut ends.

Okie Knife Plate Slotter - Mortiser for the 5 1/2" x 9" GluLam Beams.

(AKA Chainsaw on a Stick)

Not a precision slotter, but it's better than free handing the 3/8"x 4"x 8" knife plate slots and it has a depth gauge block so we don't cut the slots too deep. This picture of the Okie Knife Plate Slotter - Mortiser is for the 5" deep slot we had to make in the sides of the 6x6 post and for the 5" deep slots we had to make in the ends of the GluLam beams.

Erik slides the chainsaw into the router slot and I press down on the Okie knife Plate Slotter jig to keep the chainsaw cut parallel with the sides of the GluLam beams.

                             The depth gauge block is also used to keep the jig perpendicular to the cut.

Timber Framing 101 router jigs. 

To slot the 5 1/2" x 9" Rosboro X-Beam, we used a router jig with a 1/2" straight flute bit. For slots on the ends of the GluLam beams we slotted the beams 4" deep with a 5 1/2" straight flute router bit, an 1" at a time on the depth so we didn't break the router bit. Most of the knife plates are 4" wide. Some were 6" wide on top of the steel columns and 7 1/2" wide on the sides of the columns where the end of the GluLam beams attached. We routed out a 4 1/4" wide slot for the 4" wide knife plates, since the knife plates have a square edge.

We drilled a couple of holes at each side of the slot with an 7/16" drill bit attached to our ProTool drill guide. To remove the wood the chainsaw didn't-couldn't remove. We would have had the same problem with the Hema or Mafell Chain Slotter with the radius nose on the slotter.

Router jig attached to the end of the GluLam beam.

Our newbie painting the ends of the GluLam beams with Anchor Sill to prevent the GluLam beams from checking or splitting in this 100+ degree heat.

Drilling out the steel post base hole an 1/32" . The steel columns  must be set perpendicular to the foundation layout to make the knife plates on top of the steel columns align with the knife plate slots in the GluLam beams.

Steel post and steel beams being welded.

Two Hour Fire Wall

Tim Uhler and Kyle Davis layout, frame,sheathe and lift rake walls on a daily basis. They make it look as simple as tying your shoe laces. I had a two hour fire wall (1600 pounds) to lift this last week, so I asked Tim for the correct way to attach the lifting straps to the wall. I didn't want to jack up the wall and attach the lifting strap on the underside of the wall.

Sim,
We use nylon lifting straps we bought at whitecap.
Make sure they are rated 10,000# or greater.
On this last house we used Simpson screws because they are bigger then the Ledgerlok http://www.strongtie.com/products/connectors/SDWS-SDWH.asp?source=fastenhp
I would use 4 screws per pick point minimum. If the bottom plate on the way stays down, the pick points, and forklift will "see" less load as the wall goes up.

We've thought about making rips of 1.75" x 5" Lvl to use instead of 2x6 to screw to the top plates. We haven't had anything break yet. 

Tim
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I went by WhiteCap Construction Supply on the way to work, but they didn't carry any of the Simpson Timber Screws. So I bought some GRK 3/8" x 8" timber screws that are rated at 4364 lbf  for side grain tear out. I was worried about the the top plate of our two hour fire wall ripping off the rake wall, because we only had two layers of GP DensGlass Sheathing (sheetrock). If I had structural plywood sheathing nailed to the rake wall top plates  I would not have been concerned about the top plates ripping off the studs.

Note: This two hour fire wall required 6 building inspection.

1. Screw inspection on Base Layer on outside of wall.(1 1/4" min screw length, 6-12 O.C.)
2. Screw inspection on Face Layer on outside of wall. (1 7/8" min screw length, 6-12 O.C.)
3. Frame inspection after we lifted the wall.
4. Shear wall sheathing nailing.
5. Interior Screw inspection on Base Layer on inside of wall.(1 5/8" min screw length, 6-12 O.C.)
6. Interior Screw inspection on Face Layer on inside of wall.(2 1/4" min screw length, 6-12 O.C.)

Outside base and face layer inspected.

3/8" x 8" GRK screws , 3 each side of rake wall top plates, screwed into our 4x4 post. With 4- 4 1/2" SDS screws on each side of the strap, that's rated at 12,800 pounds in the basket position.

Third inspection on the framing and anchor bolts.

Fourth inspection on the plywood shear wall nailing.

Fifth inspection on the base layer on the inside of the two hour fire wall.

Sixth inspection on the face layer of the two hour fire wall.

After using Tim's method of attaching the lifting straps to the top plates, I would only place the lifting straps on the bottom side of the two hour fires walls when they weigh more than 2,800 pounds.  Tim's method made lifting this rake wall as simple as tying our shoelaces.

Here's some pictures showing how we use to lift our walls, by jacking up the wall and placing the lifting straps on the bottom side of the wall. Or by cutting slots in the plywood for the lifting straps.