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Knife Plates

Started by jwh1291, April 12, 2019, 04:41:14 PM

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jwh1291

Does anyone out there know of a good knife plate supplier for timber posts? Looking for a supplier of plates, fully concealed or not, of all varieties for anchoring to concrete pads and foundations. My timber posts are all typically +/- 8"x8" or 8"x10" (actual dimensions). Thanks. 

Josh 

Mike W

Josh

look up timber frame headquarters, under the products page, they have a couple/few types of Knife plates that may work for you

Best

flyingparks

A local welder may be the way to go.

jwh1291

Thanks, the problem I have run into with local welders is that its hard in some instances to get inspectors to okay their products without a detailed account of specs that I can provide regarding strength of connections and such. 

flyingparks

As long as they have their certificates, you should be fine.

waynorthmountie

After only their second year of training most welders are certified for building structural items. That stated it may be different for housing items.

Typical of inspectors though not to accept something that is outside of their understanding of what is appropriate.

flyingparks

Out here it takes much more than two years. The folks that do the certifying will X-ray  your welds. They will make you weld in various positions, like upside down. It is very hard to get certified. Our building department requires a third party welding inspector to come and inspect field welds and check the certificates of the welder. However, if the welding operation is certified and the welds are being done in a controlled environment (like a shop), than the building department doesn't require an inspection. Another hoop to jump through, but I don't mind it because I like to know it's done properly. I know a lot of welders who say they can weld anything but really shouldn't be welding anything structural. So that being said, depending on the connection to the foundation, the knife plates could easily be done in a certified shop.

D L Bahler

Pretty sure none of the guys I saw welding on commercial buildings with sunglasses in Thailand were certified... so, there's that... I guess

flyingparks

Not saying someone who isn't certified isn't capable. I'm just saying the rules in our area are there for a reason. All those failed trailers on the side of the highway that could have killed someone were done by the welder next door. It's easy to make welds look good. Someone has literally caulked and painted welds to make them look good because they were done so poorly. Had an inspector not been out there to catch it it could have been very bad. My two cents

Don P

I doubt the point of failure in a typical foundation knife plate connection is going to be at a steel to steel connection. It is more likely going to be at the steel to wood connection which has a small fraction of the steel weld strength. Not saying that argument wouldn't fall on deaf ears. The awc.org connections calc used in the design might help calm the inspector. That is based on the NDS tables for connection strength.

flyingparks

Totally agree. A knife plate is highly unlikely to fail. Maybe in the case of an extraordinary lateral load it would fail. But, building departments usually don't take things like that into consideration. They come up with a requirement and it's across the board. I recently put in a 42' piece of C channel but for purposes of getting the beam into place it had to be spliced. A connection like that deserves a welder who has proven capabilities. It sounds like the original poster needs to have a welding inspection, so again my recommendation is using a local certified outfit and provide them with the detail. Knife plates are expensive to put in the mail. Good luck!

Don P

Agreed, the detail would probably need to be provided by a PE and the fabrication through a certified welder. If the PE would provide a generic detail that would work for most situations rather than per job that would be great, you're getting into his liability exposure then though, repeated exposure for one drawing. That is a lot of why we have gotten to Simpson etc.

jwh1291

Anyone have a trick for cutting slots into the base of posts for concealed knife plates? 

Don P

The wickedly dangerous way, you've probably already considered that one.
Chain mortiser.
I've also drilled multiple holes with a long bit. Then angle to connect the holes as much as possible, then a stiff sawzall blade like a Milwaukee AX. Then if that didn't get it clean at least the dangerous way is less so. A battery chainsaw has less momentum.

flyingparks

You can buy a Swisspro Horizontal chain spotter for $7,800.  :D
I use a drill guide with a small bit if the bottom of the timber will be exposed. If it is not going to be exposed you can cut three sides with circular saw. Either way you'll need to do some chisel work.

Brad_bb

I See this is your first time posting.  How about putting your location in your profile, it will then show up in each post.  This helps people direct their responses based on your area/part of the country.  Nice to know whereabouts people are.  

And Welcome to the forum!
Anything someone can design, I can sure figure out how to fix!
If I say it\\\\\\\'s going to take so long, multiply that by at least 3!

Jim_Rogers

Many years ago, I attended a raising in NH. At that time they were preparing the post bases for a knife plate.
I took lots of pictures of the bracket that a timber framer had installed on his chain saw that would hold the bar in the correct position to bore a knife plate hole into the base of a post.
Unfortunately during my shoot of the process my camera auto focus motor died and all my pictures came out very fuzzy.
The last picture I got that was good was this one:



 

After the knife plate was inserted the though bolts were put into the post and after the post was raised and set in place the knife plate base was welded to the plate that was cast in the concrete.:


 

This welding in place afterwards allowed the post to shift a very little bit to align to the spot where it needed to be for all other joints to go together and be true, and plumb.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

flyingparks

Hey Jim was there any concern about the heat transfer from the welding surfaces to the posts? It looks like there wasn't a full perimeter weld, just about an inch per side. I'm made the mistake before of welding a wooden table top encased in c channel to a metal base. The wood didn't ignite but it did smoke and burn a little. Luckily the Sho Sugi Ban look is in. :)

Don P

 Not that I love the shortness of this knife plate, the short relish, the predrilled hole or the short anchor hooks (yup this was stamped and done by certified welders) What I do like about this one is the standoff made of 5" square tube that is welded to the knife plate. When they field welded to the lower cast in plate there was no shou sugi ban going on.




Brad_bb

I've said this before in several other posts, but I am NOT a fan of wet setting Anchors, bolts, or plates in a foundation.  Waiting until it's cured, and then accurately snapping chalklines on the foundation and using a laser level for height, then drilling and epoxying anchor bolts in is the way to go in my book.  

I used these stainless knife plates made by a fabricator, in a horse barn recently.  Turned onto these by a timber frame shop that uses these knife plates or custom versions of them.  Stainless was chosen due to wash stall, and possibility of pressure washing and not wanting bases to ever rust.




You can see that anchor bolts are used to hold the plate down, and a 1" peg is used to secure the knife plate to the post.
Anything someone can design, I can sure figure out how to fix!
If I say it\\\\\\\'s going to take so long, multiply that by at least 3!

flyingparks


Jim_Rogers

Quote from: flyingparks on April 16, 2019, 06:06:18 PM
Hey Jim was there any concern about the heat transfer from the welding surfaces to the posts?
I wasn't there when it was welded but soon afterwards and saw that the concrete was wet. I'm assuming that the welder had a bucket of water there to wet the timber to keep it from burning from the heat of the weld.
Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

flyingparks

Totally agree, Brad. I always ask the engineer if we can set them after the concrete starts to set up. Sometimes they allow, sometimes they don't. Sometimes the rebar welded the bottom of the base plate needs to be 2'6". Yikes!

timberwrestler

Not me (my buddy), but what I'd do:







www.uncarvedblockinc.com
www.facebook.com/uncarvedblockinc

luap

Quote from: waynorthmountie on April 13, 2019, 11:17:40 PM
After only their second year of training most welders are certified for building structural items. That stated it may be different for housing items.

Typical of inspectors though not to accept something that is outside of their understanding of what is appropriate.
welding certification can be a very specific process. structural and pipe welding have the welding procedure certified first. That will specify type of rod,  what is used for the root pass  and how wide the cover pass is and how high above base metal it can be and base material. The welder then makes the weld in whatever position is specified. certain positions supersede others. If I certify on 8 inch pipe in a 45 deg position then I am good for pipe that size and smaller in any position. If I certify on horizontal pipe then that's what my certificate is good for. Pipe welding certificate supersedes all structural. then the testing can be x-ray or destructive. Only so many defects are allowed to pass. all that said welding inspectors are working for the company building the pipeline or bridge or whatever and will have there own set of requirements usually dictated by the engineers. No matter what certificate you may have held every welder is tested on site. You also have to make a certified weld within a certain time period to keep you certification. At one time on these bigger jobs only a percentage of welds were tested but most require every weld x-ray tested today. So just because some is certified may not tell you the complete story

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