Thread: Homemade Tri-Square - have you made one?

Here is a 6" one I made a couple of years ago. This is not the only way to make these - there are many methods. I always like to be able to take my tools apart as much as possible - there are ways of making a trisquare that are simpler but here is what I did.



This one is adjustable so if it goes out of square it can be adjusted back to square. It has to be one the most difficult tools I have every made. Ultimately how square it is depends on you having access to a high quality square of some kind to compare it to, because testing the square you are making for squareness by usual methods is not that accurate for small squares.

I will leave the adjustable mechanism out of my description because it is a bit complicated to describe in words.

The blade needs to be made out of something reasonable hard or else it would wear too quickly. Mine is made from a left over piece of 0.03" thick blue steel floor scraper available at most hardware stores. This was cut to shape using a fine kerf metal cutting blade in a small table saw and then filed by hand to size and parallelness. The blade sides have to be absolutely straight and parallel, this requires some time and a lot of patience. The effort needed to make this component alone would put me off making another.

The handle is made from Australian Red Gum from my wood pile but any hardwood would do. The slot for the blade in the handle was cut with a tenon saw so that the blade was a very tight fit. Then I drilled 1/8" pilot holes thru the timber to mark the positions for the hole in the blade. Remove the blade and drill the holes for the 1/4" brass lugs using a 15/64 drill. The blue steel material is VERY hard but can be drilled with patience. I used brand new drills and lots of lubricant on a drill press. If you press too hard the blade will stretch, bend and permanently dimple so you just have to take it easy and use enough pressure to cut without making it bend. A cobalt HSS drill will work better than a regular HSS drill. No matter what you do the holes will be burred and these have to be removed with a file or abrasive paper. By the time you do this the holes may be slight bigger than 15/64"

Next drill 15/64" holes in the handle. You want a really tight fit so you might have to open them up a little with a little roll of abrasive paper to fit the brass lugs. You might need to do the same with the holes on the blade. I would strongly recommend doing a complete practice fit with a bit of blue steel and hardwood scrap, you don't want to mess up the blade which has taken you hours to file square and parallel .

The brass lugs are made overlength and after they have been hammered into place they are sanded flat to the timber with a belt sander. The brass rub plate is made from 1/16" brass plate and held in place with some countersunk screws as shown.

Next test for squareness. You can cheat a little at this point and file the balde again if needed to make it square.

These look like simple tools but they are very demanding to make accurately. If this is the first tool you have ever made I would strongly recommend making a few simpler ones first. Better still, unless you are seriously into toolmaking, I would just go and buy a superb Colen Clenton Square, These are just awesome and if you do try and make your own you will appreciate the effort and skill that goes into making these tools.

Cheers

Have a look at Hayward's book on Making tools:
http://www.toolemera.com/bkpdf/haywardhowtobk.pdf

Originally Posted by jmk89

Have a look at Hayward's book on Making tools:
http://www.toolemera.com/bkpdf/haywardhowtobk.pdf

JK, link does not work. Directory also no longer exists, it looks like the book has been removed from that site.

Try this:
http://www.toolemera.com/Books%20%26...ooksplans.html

Remove the blade and drill the holes for the 1/4" brass lugs using a 15/64 drill. The blue steel material is VERY hard but can be drilled with patience. I used brand new drills and lots of lubricant on a drill press. If you press too hard the blade will stretch, bend and permanently dimple so you just have to take it easy and use enough pressure to cut without making it bend. A cobalt HSS drill will work better than a regular HSS drill. No matter what you do the holes will be burred and these have to be removed with a file or abrasive paper. By the time you do this the holes may be slight bigger than 15/64"

Have read a technique of spot annealling a hardened steel blade by clipping the head off a nail, chucking it in the drill press & running it on the spots where you wish to drill.

Would make it easier to do the drilling at least. Lot of work in the rest of it though, Bob.


Cheers......................Sean

That sounds like a good little tip Scooter. I'll give it a go. Thanks.

Originally Posted by scooter

Have read a technique of spot annealling a hardened steel blade by clipping the head off a nail, chucking it in the drill press & running it on the spots where you wish to drill.

Would make it easier to do the drilling at least. Lot of work in the rest of it though, Bob.

Thanks for the tip - I used the same blue steel scraper blade material to make a tenon saw. I want to make another soon, so I'll definitely be trying that next time to make the holes for the handle.

Just be careful the nail doesn't weld itself to the blade - it does happen!

In the metal work forum there was a post by me about using a carbide tipped drill to drill a hole is HSS. I used a sharpened masonry drill bit - and it went through HSS - not easily but it went through. This means it will also go through this hardened blue steel plate.