How to cut half-lap joints on a 45 in middle of stock

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Forum topic by JK1972 posted 02-15-2016 06:29 PM 2562 views 1 time favorited 0 replies Add to Favorites Watch
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02-15-2016 06:29 PM

Topic tags/keywords: half-lap

I am posting this because I got a lot of good tips on the subject while trying to build some table legs. I hope this helps someone and saves you a lot of time and headache. I would consider myself a novice to intermediate woodworker. I’m trying to start a little side job and had a request to build a table with 4 “X” style legs. After thinking on it and asking for advice, I finally figured it out. Thanks to all those who replied to my call for help. I think I used a little bit of everyone’s advice. Forgive me if this is a little lengthy but I wanted to be as detailed as possible for those who are new to woodworking like me. So here it goes:
How to cut half-lap joints on a 45 in the middle of stock
1. Leave stock plenty long. You can cut to length after half-laps are cut. I was making legs 33 1/4” long and used 48” pieces.
2. Mark the center of your stock.
3. Mark the angle you want. Then using a piece of your stock, line it up and mark the other side.

4. Wrap the marks for width to the adjacent side. These are your start and stop points. I extended these to a second piece and cut them together. These marks will help you keep get the pieces realigned if you have to cut a little more. Remember, you can always take a little more off so go slow and careful.
5. I used a scrap piece of plywood to extend my miter fence on my table saw & used spray adhesive to attach 2 small pieces of sand paper to the face. This will help keep the work piece from slipping as you push it through
6. Set the depth of your blade to just less than half of your stock thickness. This will ensure a tight fit. You can fine tune after a test fit.
7. Clamp 2 pieces of stock together to cut at the same time.
8. Set the miter gauge to 45 & line up your first cut with the saw OFF. I don’t think it matters but I set my miter gauge to the left & cut on the right side of the blade just out of personal preference.

9. Once you have the stock lined up, turn on your saw and make the first cut. My second cut was at my stop mark. Then I just nibbled away at the center.
10. Once all the material is cleared, turn off the saw and do a test fit. Just turn one leg end over end and it should match up. Once you like how the joint fits, leave the pieces together to mark legs for their final length.
12. Angles can make your head spin at first (at least they did mine) but after a couple of hours of trial & error and putting pencil to paper, it turns out it’s really not that difficult. Once I figured everything out, I made a template set of legs to ensure all of my legs would be exactly the same.
13. I spent a lot of time trying to figure out what angle I needed to cut the top and bottoms of my legs so they would sit flat on the floor and under the table top. Here’s my quick class on these angles:
—My joints are 45 degrees. A triangle is made up of 180 degrees. 180-45=135 for the other 2 angles. 135 divided by 2 is 67.5. This is NOT the angle for your cuts. If you make a 90 degree line next to the triangle, you can visualize the angle of your leg. Now subtract 67.5 from 90 and you get 22.5 degrees. THIS is the angle for your cut for the tops and bottoms of your legs. And it just so happens that is a pre-set angle on your miter saw! Go figure.

14. Now that you have the angles figured out, how do you determine the actual length to cut your legs so they are the correct height? If you just cut them to the final height, they will be short because they are at an angle. Here’s where my jig/template comes in. I used a square and clamped it between the legs to make sure it was a 45 degree angle, then I screwed the legs together at the joint. Then I found the center of the joint by drawing lines from each point of the joint.

15. Next, measure ½ of your total height from the center of the joint & use a straight edge to mark your legs at the top and bottom. (My height was 33 ¼” so I measured 16 5/8”)

Double check your measurements by measuring from mark to mark on the same side. This should be your final height. (Mine is already cut but this is where your marks should be on your uncut piece)
The pieces on the top are some I messed up trying to figure everything out.

If it is correct, you can separate the legs and cut them to length. I marked my pieces to make sure I kept them together after cutting. Be sure to cut your angles the correct way. Make sure they will be oriented in the right direction. I even stood mine upright to check them. Leave the legs together when you sand them. I separated mine and they didn’t fit as tight after sanding.
16. Last, I drilled a ½” hole in the center of the joint and will glue a dowel in place for extra strength and a little aesthetics.
Happy woodworking!

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