# HELP! Jig for lap joints on end of boards?



## DesertRatTom (Jul 3, 2012)

Hi, getting set up to make theatrical flats that depend on lap joints. Dimensions are 4' by 10', with a crossbar top, bottom and two evenly spaced the length of the flat. The rails and styles are all 3.5 to 4 inches, depending on what I can find that's relatively straight.

Window and door flats are a little different and rely on bottom steel braces to hold their shape. All possible joints will be lap joints.

That said, I need to build a jig that will fit over the end of the stiles. Any suggestions on how to make this. The lap joints on the other rails are pretty obvious. All lap joints must be an exact fit.


----------



## Stick486 (Jan 4, 2013)

table saw and a dado blade..
ball roller stands for material support...


----------



## DesertRatTom (Jul 3, 2012)

Stick486 said:


> table saw and a dado blade..
> ball roller stands for material support...


Not workable in my small shop. Pretty much has to be a router. Wondering whether the side rails of the jig need to b adjustable to fit the 3.5 inch stock width, or whether I can just snug the jig up to one edge of the 10 ft rail. Maybe make a small jig just large enought to stabilize the router over the jig. 

I can see it will be easy to handle the jig for the middle of the styles, but all joints will have to be right on ends. In other words, how can I build a jig to cut the ends?

I found a video where the set builder cut across the rail with a hand saw, then used a router freehand to remove the rest. I am not so sure I can hold the router staady enough to make that work. Your thoughts?


----------



## Stick486 (Jan 4, 2013)

okay...
so use Oliver's jig...

.


----------



## Quillman (Aug 16, 2010)

Just a right angle jig with a strong back. Like this.
Use a spacer or the stock itself to position the the jig. Add some for the offset in the collar.


----------



## tomp913 (Mar 7, 2014)

@Desertrat Tom

You don't say what thickness material you'll be using, but even 1X will require a couple of passes with a router. Or how many pieces you'll need to cut. As we're probably not talking super precision, I'd look at using a circular saw set to half the thickness, and cut multiple kerfs along the joint and then knock out the pieces with a hammer.

I had to make a new door for my shed - the new grass catcher on the riding mower was less than 1" narrower than the old opening. I removed one stud and reframed the opening and made a new door to suit. The original doors were made of 2X material with half lap joints at the corners and at the center rail. I used a CS with the Kreg cross cut joint and had all 12 joints cut and fitted in a little over an hour. Left about a blade thickness of material between each kerf and then just smacked it with a hammer. A couple of swipes with a block plane cleaned the faces up well enough and I put the frame together with construction adhesive and deck screws.

The original shed is about 25 years old and the door has held up OK so no reason that the new one won't.

It would probably be quicker with one of the newer sliding miter saws where you can lock down the blade at a set height above the table but I don't have one of those, the CS worked pretty good and was the way that I'd built the original doors.


----------



## Ray Newman (Mar 9, 2009)

Do you know someone who has a now "obsolete" RAS -- radial arm saw? A stop block, sharp dado head cutter, and a RAS set to cut the correct depth would make short work cutting half laps. Gang up several boards with a few nails and pieces of scrap and the work will go quicker.


----------



## Cherryville Chuck (Sep 28, 2010)

Use a guide similar to the one in this link  http://cdn1.tmbi.com/TFH/Projects/FH08OCT_SAWGUI_01.JPG . Use about 1/4 to 3/8 material for the base and leave it long enough so that you cut the edge off on the very first pass. That shows the cut line for every cut after that. Take a short piece of the material you want to lap and scribe (not pencil) lines down the edges when it is 90* to the piece you want the lap on. You can add a cleat to the piece to automatically register it at 90* and that would be faster.

Once the lines are scribed use the cutting guide to cut one line and then flip it around and cut to the other line. Then just hog out the waste in the middle working from one end to the other.


----------



## kp91 (Sep 10, 2004)

Quillman said:


> Just a right angle jig with a strong back. Like this.
> Use a spacer or the stock itself to position the the jig. Add some for the offset in the collar.


Pat,

That is a great looking jig, simple and effective.


----------



## tomp913 (Mar 7, 2014)

I found a movie

Create a Half-Lap Joint | Today's Homeowner


----------



## mgmine (Jan 16, 2012)

Why not pocket holes instead of a lap joint?


----------



## CharleyL (Feb 28, 2009)

I would use a plunge router and a jig made in the following way. I would start with a piece of 3/4 plywood, maybe 18" square, so it could be clamped or screwed to a saw horse or work bench. On top of this I would attach pieces of scrap material the same thickness as the material that you will be cutting, to make a 3 sided pocket to fit the end of the piece to be routed. Since much of the top surface of this scrap will be routed away, they should be glued, and not screwed in place. On top of these, attach a fourth piece of scrap to form a bridge over the open end of the previous layer, adding some 1/16" shims under it so the piece to be routed can easily slide under this bridge. The bridge position needs to be calculated, because it will be the fence that the router rides against when cutting the half lap. This completes the jig for the end half laps.

Attach the jig to a workbench or saw horse and insert the first piece of stock that will receive a half lap and clamp it in place. Using the router and a large diameter mortise bit, set for 1/2 the thickness of the material being cut, place the router up against the side of the bridge piece and make the first pass. Then free hand cut the rest of the half lap, but make certain that you leave some of the surrounding pieces of scrap at full thickness to support the router base. 

I built a second similar jig with two bridges and a pass through design to cut 1/2 laps in the stiles for the rails. The space between the bridges needs to be the size of the router base plus the width of the half lap plus the diameter of the bit used. If you through cut the two passes adjacent to the bridges, then you will have accurate position cuts in the scrap side pieces to line up the rest of the pieces for cutting.

I helped make flats for a local theater group about 14 years ago and built jigs like this to cut the 1/2 laps. In addition, the corners of the flats received 1/4" thick plywood gussets on the back side for further strength. All joints were glued and screwed together. Most of the flats that I helped make are still in use, and this group does 2-4 shows per year.

A router table could also be used for this, but I prefer using the plunge router with jigs built like described above. Even someone not skilled in router use can be taught to use these jigs in 5-10 minutes. 

Charley


----------



## DesertRatTom (Jul 3, 2012)

mgmine said:


> Why not pocket holes instead of a lap joint?


I think I should add some information...

Theatrical flats get very rough treatment, a set must be changed completely in 4-6 minutes. They are lashed together with rope. They are held up by large L brackets held down with sandbags, and by angled flats that intersect them. 

The Stiles are 10 ft long and have half lap joints on the ends and two each in the middle of the long side of the framework. It is really not unlike a giant face frame, but it must stand up to a lot of abuse. In the past, you would assemble flats with triangular pieces of 1/4 ply, but by using half laps, you can fold them and stack them better. Door and window set pieces have additional rails, and door pieces have a 1/8 steel bar across the bottom. Window pieces span two stiles.

Each joint will be glued and/or screwed together for maximum strength, which requires a flat surface on the joint.

Flats are covered in raw muslin, stapled in place on the back, inside of the frame. The muslin is then coated with sizing (a form of hide glue) so it shrinks nice and tight. That is why the rails are set in the middle, to keep the flat from bowing under the pressur of the shrunken, tight fabric. 

Most flats are painted over 40-50 times. They are sometimes connected with loose pin hinges, but mostly by rope lashes.

The frame is very carefully squared up, so they will be assembled in a jig. If they are not square, they cannot be lashed together. That is why I am so interested in precision in making the joint. 

I've seen a video of a commercial theatrical flat making operation, and a router was used to clear the joint after an initial saw cut established the joint's edge.

Construction will take place across 3 folding tables, so clamping with be somewhat limited, which makes a precise jig even more essential.


----------



## DesertRatTom (Jul 3, 2012)

CharleyL said:


> I would use a plunge router and a jig made in the following way. I would start with a piece of 3/4 plywood, maybe 18" square, so it could be clamped or screwed to a saw horse or work bench. On top of this I would attach pieces of scrap material the same thickness as the material that you will be cutting, to make a 3 sided pocket to fit the end of the piece to be routed. Since much of the top surface of this scrap will be routed away, they should be glued, and not screwed in place. On top of these, attach a fourth piece of scrap to form a bridge over the open end of the previous layer, adding some 1/16" shims under it so the piece to be routed can easily slide under this bridge. The bridge position needs to be calculated, because it will be the fence that the router rides against when cutting the half lap. This completes the jig for the end half laps.
> 
> Attach the jig to a workbench or saw horse and insert the first piece of stock that will receive a half lap and clamp it in place. Using the router and a large diameter mortise bit, set for 1/2 the thickness of the material being cut, place the router up against the side of the bridge piece and make the first pass. Then free hand cut the rest of the half lap, but make certain that you leave some of the surrounding pieces of scrap at full thickness to support the router base.
> 
> ...


Thanks Charley, this is exactly what I was looking for. I missed this post before posting the previous item. VERY helpful.


----------



## DesertRatTom (Jul 3, 2012)

@CharleyL Thanks again. One last question, what did you use for your lumber? Pine I'm sure, but was it knot free? Did you have to do a lot of hand selection to get fairly straight stock? Kiln dried? Our theater uses 10 ft. flats, which is alot of length to find straight pieces for. I'm paying for this as a contribution, so I don't want to buy better than I actually need. I can drive to a large lumber supplier to get this stock, don't have to stay local.

Our theater group uses tape to hide gaps, in the old days we glued on fabric. Man, that hyde glue really smelled bad.

I'd really like to do enough flats for two sets, with a couple of door and window flats to spare. Our commmunity theater is an old USO building from WWII, 25 ft wide procenium and 25 feet from apron to back wall. 10 feet 2 inchs from stage floor to ceiling.


----------



## CharleyL (Feb 28, 2009)

The flats that I made were poplar 1 X 4 and 1 X 3 stock with almost no significant knots.
Pine should be OK if you can find good quality at a reasonable price. My high school stage had pine flats in rough condition but we just kept repairing them and never made new ones. At least two shows that used them were put on each year and I think the flats were the original 30 year old original flats that were built when the school opened. A Summer Theater that I ran one Summer after high school had pine flats that were in rough condition, but I think they had been around for 40 or more years and significantly abused. All were still straight enough to use, but we only did one show that required them. All of the rest of the shows were orchestras, stand up comedians, movies, etc.

The poplar wood for what we built was donated by a local lumber company. Much of it was very green and almost black in color in places, so I suspect that it was culls that the customers wouldn't buy. All of it was very dry and almost all of it was very straight with no twists of any significance. The few pieces that weren't straight enough became short rails and wherever not straight enough for that, were used wherever shorts could be made from them for around the windows and doors. I used the 1 X 4 for the tops and bottoms of the flats. There was almost no waste, at least nothing longer than 2'. We actually had 23 full 12' sticks left that were not unused and were saved for future projects.

As the frames were built I had two volunteers using laminate trimmers with 1/8" round over bits, ease all of the edges, because the edges of all of this donated stock had extremely sharp corners. They each went through several carbide bits just doing this part. From my memory, 26 full 4' wide 12' high flats, plus some 1, 2, and 3' wide, 4 door flats, and 3 window flats were built, plus one short curved end flat was built to be used above an archway. I was only involved in building the frames for the flats. They had others attaching the muslin with air staplers and sizing them. I don't know what sizing they used, but it was white and did not smell bad. I suspect that it may have been just white wood glue. When they ran out of stage space, the flats that were complete and just drying were carried outside on the lawn for the Sun to dry. They used cases of this sizing, whatever it was.

Without plywood gussets, I'm concerned that the half laps, especially those used for the cross bracing, may not leave the joint strong enough for the treatment that these flats will get in their life. A piece of wood 3/8" thick at a joint in the middle of a 10 or 12' length of 3/4" thick wood is a significant weak point.

My work area was the orchestra pit and the stage was used for the covering and sizing. Behind and to one side of the stage is a workshop and storage area, but it's way too small for all of this to take place at the same time. We had 22 banquet tables that we used as work benches, with brown kraft paper covering them to keep them as clean as possible. 

All of this work was done in two weekends, but I had built the jigs in my home shop ahead of time. About 28 people were involved. Some stayed the full time while others came and went. During the two weekends I trained 6 to use the laminate trimmers, one to use the chop saw, and two to use the routers and the 1/2 lap jigs, plus me. I filled in where needed and generally supervised the frame building. There were also those who assembled the frames with glue and screws. I forgot that I had also built some jigs to help with getting the frame joints square. For these, all they had to do was drop the pieces into place and clamp them against the two right angle sides of the jigs, then apply the glue and screws. The plywood gussets were installed at the next assembly position using an air stapler and narrow crown staples. Separate drills held the screw drill bits and the driver bits. I think we had 4 of each there, with back-up batteries on charge nearby. We had the frames for the flats almost complete by the end of the first weekend, but we got way ahead of those doing the covering and sizing. We worked mostly on the door and window flat frames the second weekend. I was gone before all of the frames had been covered and coated. I think they worked the following weekend on them.

I hope you are going to get help to build all of this. It takes a lot of space and people to make these quickly. Things begin slowly, but with the jigs and tools all in place, and the workers comfortable with their part, the assembly line speed picks up very rapidly. I think it was some fun time for everyone involved. I know that I enjoyed it. Oh, keep plenty of sandwiches, coffee, water, and soda available. 

In each of the theaters that I've been involved in, the flats were stacked against a large flat wall behind or adjacent to the stage, and bungee or rope strapped to the wall at several heights to keep them flat when not in use. Slight warping front to back doesn't matter much because they are flexible enough to pull straight as you tie them together when in use. You don't want the two sides to pull together. They need to be straight, so use cross bracing at several heights when constructing them. Every 3-4' or so is a good number. Just divide the height up roughly equally for the positions of these. 

Charley


----------



## CharleyL (Feb 28, 2009)

I missed saying that we used wide masking tape on the joints between the flats at the high school, so I did the same when running the Summer Theater, followed by the paint. I suggested using it in this theater, but they have just been roping the flats together so far. Maybe in a few years, after the flats begin to get roughed up, they will decide that the tape is is a good idea.

This group uses an old movie theater that was originally built for stage shows, but I don't think it was used very much for the shows. Much of the old theater show equipment like sets, etc. was removed and scrapped many years ago, but you can sometimes see where it was originally located in the mounting points and dirt shadows still there. I think the original paint is still on the walls backstage. When you get up above and high behind the stage, things have 75 or more years of dust and dirt on them too. You show it very well when you come back down. 

Charley


----------



## DesertRatTom (Jul 3, 2012)

@CharleyL Wow, that is some project. I was just going to work on them myself, but I know that if I went through the nonprofit arts group that runs the theater, I could really get more people involved. It might be easier to get lumber and materials at a discount. I like poplar, but pine will work OK. Storage to keep them flat is something I hadn't considered, but it sure makes sense. There will be 2 rails in the middle, plus top and bottom. 

I've been thinking about the jigs and it occurs to me that all the end piece half laps can be cut in a fixed jig. Slide the pieces into the jig, clamp them down and zip zap with a router. I was already planning on a corner jig to make sure it's square, I might make two, about 5 ft. long. The jig for the half laps in the stiles will be easy.

I was planning to pony up about $2,500 or so myself, but if I can do it as a community project, that can stretch much further, especially if I can get the materials donated or at cost. 

I have a feeling the rails and squaring up the corners will do a lot to straighten out any slight warping. Glue and screws are never going to let loose. I am not likely to use gussets since I want some to store back to back. Theatrical supply houses have special loose pin hinges and other hardware, but they are priced pretty high, so I'm likely to use the old bent nail for hinge pin trick. Everyone loses the loose pins anyhow. We can grind off the end of a cheaper hinge to remove the pin.

The thing I have always liked about community theater is the working together on a big project. This would certainly fit that picture. Lots to think about here.


----------



## DesertRatTom (Jul 3, 2012)

This is a set I did some work on not too long ago. Did the large window as one piece, and the faux french doors. It was for a production of "Cat on a Hot Tin Roof." I
Throulghout High School, I did a lot of theater, four classes in my senior year, and directed many plays. My best friend, Byron Bauer, was a real stagecraft guy who went on to teach tech theater at LA State, and he also deisgned sets for the Mark Taper Forum in Los Angeles. Now 72,he runs a film production services outfit.


----------



## mgmine (Jan 16, 2012)

If your shop is too small then move the saw outside or make all your cuts on one end then move the saw to the other end of the shop or possibly by the door going into the shop if there is one. No matter what unless you have a large cabinet saw it would be quicker and easier and possibly more accurate with a table saw. 
http://www.woodsmith.com/files/issues/146/cut-perfect-half-laps.pdf


----------

