jump to example.com
Examples of Structural Pipe Fittings

Remember playing with Tinker Toys? Maybe they weren’t as cool as Legos or Erector, but they sure beat the crap out of Lincoln Logs. As an adult, you don’t have to secretly pine for your old play gear: check out these structural pipe fittings. They’re usually expensive enough to be deemed “Tool Pr0n,” but now that Harbor Freight carries them, you can pick some up without selling your car.

Harbor Freight’s structural pipe fittings let you connect standard 1-1/4″ OD PVC or steel pipe, and they cost a fraction of that of name brands like KEE CLAMP. They’re also galvanized to resist rust. Attaching the structural pipe clamps involves tightening a single hex drive screw per connection. Of course, you still have to supply the pipe, but you can score 1-1/4″ PVC or steel pipe on the cheap at most big box stores.

Available in eleven flavors from a three way 90° elbow to a double swivel tee, these structural pipe fittings run from $3 to $5 — versus $10 to $20 or more for name-brand fittings. And while Harbor Freight doesn’t offer the selection of fittings that other companies do, you never had all the pieces you wanted in your building sets as a kid either. That never limited your imagination, right?

Update: The inner diameter (ID) of these clamps is approximately 1.4″, which means it’ll work with 1″ schedule 40 pipe, which has an outer diameter (OD) of 1.3″.

Structural Pipe Fittings [Harbor Freight]
KEE CLAMP [Simplified Building Concepts]


27 Responses to A Grown Man’s Tinker Toys: Structural Pipe Fittings

  1. modernman says:

    Anyone know how these compare to kee clamp or speed rail?

  2. JamesBrauer66 says:

    I see some monkey bars in my little girls future.

  3. DaveD says:

    That is so cool!
    Where does one get the pipes for this?

  4. Domes says:

    These look nice…Does anybody know of a similar product, but set up for geodesic constrution?

    ‘Cause THAT would rock…

  5. Keith Melton says:

    Not to be a total jerk… but the plural form of Lego is just “Lego”

  6. DaveD,

    I’m not quite sure where you find 1-1/4″ OD pipe, When I wrote the post I assumed 1-1/4″ OD was a common size or else what is the point? It seems that black and galvanized 1″ pipe has a OD of about 1.315″, I’m not sure if that is close enough or not. I’m sure the local HF probably doesn’t carry these fittings to actually measure their ID — I’ve never seen them and I’ve combed over that store pretty well.

    I guess I’ll have to bring my calipers next time I stop at the local Big Box.

  7. Randy Piscione says:

    Wish I had known this a few months ago. Not sure if I can post links in these notes but here’s what I built using one of the name brands (not Kee):



    Cost of the rack was approx. $600 CAD. There’s at least 300 pounds on it now. Pipe is an odd thing. OD dimensions of pipe are nominal, the ID is usually accurate. There is also a “schedule” number, which I think is the thickness. These are the main differences between pipe and tube. It’s the combination of the thickness of the pipe and the strength of the key clamps that give the final weight limits.


    • Sean Knight says:

      Actually, it depending on the type of pipe, outside diameter (OD) or inside (ID) may be the specified measurement, but it is still nominal in some cases.

      For example, IPS, or iron pipe size, is used for all galvanized, black steel pipe, PVC, and ABS. The “size”, whether it is 1″, 3/4″, 3″, etc, is the NOMINAL ID (inside diameter), but the fittings all go on the outside — threaded, glued, or compression — so it is the OD (outside diameter) that is always the same from one type to another in the IPS sizing family. The inside diameter can be widely varying, with cast iron having a significantly smaller volume than PVC of the same “size”. Heavier duty (higher schedule) pipe will by smaller inside as well, because of thicker pipe wall. So, PVC schedule 40 will have the same ID as schedule 80, but the schedule 80 will have a smaller ID

      CT, or copper type, sizing is different than IPS, but within all types of pipe that use CT sizing, the OD will be the same. This includes copper pipe, PEX, and some other plastic piping. The consistent OD is how you can use push fittings (shark bite, etc.) to connect copper to PEX.

  8. eschoendorff says:

    Not to be a jerk, but Keith, you are wrong. The plural of Lego is Legos.

  9. Now we all know that some people disagree what the plural of Lego is. Let us all just agree that Lego sets (see how I am now avoiding the whole issue) were cooler that Tinker Toy sets, but you can be pretty creative with either.

    I’m still working on the 1-1/4″ OD pipe issue. Tomorrow I need to get some supplies. I’m bringing my calipers — I’ll comment if I find anything.

  10. Eli says:

    Kee Klamps work with both 1 1/4″ and 1 1/2″ (obviously you’re buying different fittings for the two diff sizes). This pipe is schedule 40 or sched 80 and available from your local metal purveyor. Anybody who has structural or raw steel as a welding supply should also carry this. Black and galvy pipe will not work. It isn’t budget, but the good part is this stuff has an almost infinite life span, if you believe in buying the best once. Today’s scaffold is tomorrow’s treehouse is a haunted house a year from now. There is just no end to the use for it. Not unfortunately adaptable for geodesics. For that, on the small scale, you’re better off flattening and drilling the ends of conduit.

  11. Eli says:

    And I’ve always said, “Let’s play Legos”

  12. RobinB says:

    Kee clamp has liks to Sketchup components for designing with this stuff.


  13. Chuck Cage says:

    I always thought that “pipe” was specified by schedule or ID and “tubing” is specified by OD.

  14. Clinton says:

    I’d love to see fittings like the slides and swivels that could work with 1/2″ or 3/4″ EMT conduit as the pipe of choice. Would be a great way to make a multi-purpose easily configurable and adaptable wire rack of DOOM. I’m sure electricians (and the low voltage guys like me) would love them for all kinds of nonelectrical projects.

  15. Bee says:

    I was recently excited to find exactly this style of cheap pipe fittings at a farm supply company. teksupply.com they are 3-7 dollars each. probably 20 styles. they say that 1 1/4″ size is for 1.66 OD pipe. 1 1/2 size is for 1.90″OD pipe and 1″ is for 1.315″ pipe. maybe that clears up the sizing issue.

  16. My local Harbor Freight actually carries a limited selection of these fittings. I bought one and brought it to the local big box. Galvanized steel 1″ sched. 40 pipe seems to fit. The actual ID of the fittings is approximately 1.4″ and the ID of the 1″ pipe is about 1.3″. There’s a little slop, but the hex drive screw seems to secure the pipe well. When I say the ID of the fitting is approximately 1.4″, I mean approximately. These are not precision machined pieces of steel here, these fitting are going straight from the mold to being galvanized.

  17. BJN says:

    Galvanized? Sounds like the HF fittings are cast iron. I’d be careful about using them in the appropriate application since cast iron is a brittle material.

    I have raft rowing frames made from cast/anodized Hollaender fittings and anodized aluminum tubing. I wouldn’t use iron fittings in a similar application, but I’m sure the HF fittings would make decent railings or shelf supports.

  18. Bill says:

    Steel pipe, for a given nominal size, will have the same OD regardless of wall thickness. So, for say thick-wall Schedule 80, the ID will be smaller than the same nominal size in the thinner-wall Schedule 40.

  19. christolles! says:

    sorry to bother a dead thread, but i just found easyfit:


    their fittings are designed to work with standard big box (HD in my case) black pipe, and are both affordable and feature an abundance of styles in 3 sizes.

    bought enough for a lofted queen sized bed just now – will let you know how it turns out…

    anybody else used easyfit?

  20. pierre-luc gelineau says:

    I can’t find them on the HFT website 🙁

  21. Ken Cenicola says:

    Here is a giant swingset I made using 1-1/2″ Pipe and Kee Klamp fittings.


  22. Lowell Parker says:

    If your project gets beyond your own level of expertise, there is a good mechanical engineer available at the given link. Submit a Solution Request and enter “bgeddes” in the Specialist’s username field.

  23. John B says:

    I have 48 pieces of 96″ long galvanized pipe for building projects if someone was interested…? Pipe is 1.315″ OD.

  24. R. V. Raskar says:

    We need Aluminium die cast structural pipe fittings like connectors straight, cross, 2,3,4 way, base and angled. Pl. send catalog with price list & nearest source location.

  25. Jae says:

    I’m using steeltek pipe and fighting tho build a closet system with a fleflexible flange and a 45 to make a 90 turn. What is the take away on the flexible flange. The length of pipe from the wall is 10″ thought the lengthy of pipe that makes the hypotenuse would be 14.14. That was wrong. I think the flexible flange ads 3″. Has anybody solved this problem. Specs on website don’t help.

Leave a Reply to Clinton Cancel reply

Your email address will not be published.