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Tailored Fit: Tips For Stronger And Safer Roll Bars

Whether you are building a car from scratch or just making repairs, being able to closely fit up each piece of tubing before welding it up is the key to a strong, safe race car.

Whether you are building a car from scratch or just making repairs, being able to closely fit up each piece of tubing before welding it up is the key to a strong, safe race car.

Properly notched tubes don’t just make for a better looking race car, they make for a stronger–and safer–one too

A great fabricator can make the process of building a race car seem like creating art. And there is a lot of art to taking a big pile of tubing and a stack of sheet metal, and maybe an old chassis too, and turning it into a car capable of winning races.

But there is a lot of science too. The best fabricators have an understanding of geometry, can accurately measure and cut and aren’t flummoxed by compound angles and curves. Having the right tools certainly helps, but more than anything it is important to know how to make the most of the tools you do have available to you.

Whether you are building a race car from scratch, or just making some repairs or updates to your trusty old ride, two of the most important skills for anyone doing fab work on a race car are to be able to apply a good, strong weld and be able to properly fit up roll cage tubing.

It can be tempting to go with the “good enough” method when fitting up tubing. In other words, don’t worry about getting two pieces of tubing to fit as closely as possible, simply throw a bunch of weld at the joint to fill in any gaps. But it doesn’t matter how good your welds may look, filling a gap with welding wire is never as strong as two pieces of tubing that touch each other all the way around with a single bead of weld that properly penetrates both pieces of steel.

“Notching” is the name of the process to shape the end of one piece of tubing so that it fits around a second. Practically every joint on a race car between two pieces of round tubing requires notching. There are several ways to properly notch a tube. Some are faster than others, and some make it easier to make precise notches, but all can produce quality notches that provide a tight fit between tubes if you use care.

To find out what options are actually available to racers and car builders, we called up Mittler Brothers Machine & Tool–the most widely trusted company in racing when it comes to fabrication equipment of all types–and they gave us a rundown of different notchers and how they work. What is cool is that, like we already mentioned, all of these options can be used to build a strong, safe roll cage.

If you don't notch your tubing, you wind up with big gaps like this. You can try to cover the gap with welding wire, but it will never be as strong as a properly notched and fitted tube.

If you don’t notch your tubing, you wind up with big gaps like this. You can try to cover the gap with welding wire, but it will never be as strong as a properly notched and fitted tube.

The most basic way to notch tubing is to grind it to fit using--you guessed it--a powered angle grinder. The drawback is this method is slow and tedious, and all that grinding tends to make a big mess. Also, it takes a fair amount of skill and experience to get a good fit. When using a grinder to notch tubing, the best option is to take off small amounts of material with each pass and check often until you get the right fit.

The most basic way to notch tubing is to grind it to fit using–you guessed it–a powered angle grinder. The drawback is this method is slow and tedious, and all that grinding tends to make a big mess. Also, it takes a fair amount of skill and experience to get a good fit. When using a grinder to notch tubing, the best option is to take off small amounts of material with each pass and check often until you get the right fit.

 

Next step up is the hole saw notcher. There are several different options that vary from very basic--a hand drill (shown)--to a nice aluminum double adjustable unit you can mount in a drill press.

Next step up is the hole saw notcher. There are several different options that vary from very basic–a hand drill (shown)–to a nice aluminum double adjustable unit you can mount in a drill press.

Here's the double-adjustable unit mentioned earlier mounted up in a drill press. This setup allows for a pretty good fit and helps you to make angle notches pretty easily. The downside is they tend to be noisy in operation and can be hard on hole saws. A tip for using any notcher of this type is use a high-quality hole saw with the finest tooth count as you can get. Also, go slow when you feed the saw in so it doesn't grab the tubing and tear up the hole saw. Smooth and steady is the key here.

Here’s the double-adjustable unit mentioned earlier mounted up in a drill press. This setup allows for a pretty good fit and helps you to make angle notches pretty easily. The downside is they tend to be noisy in operation and can be hard on hole saws. A tip for using any notcher of this type is use a high-quality hole saw with the finest tooth count as you can get. Also, go slow when you feed the saw in so it doesn’t grab the tubing and tear up the hole saw. Smooth and steady is the key here.

A hydraulic notcher was created to produce a fast clean notch in a portable machine that can be taken right to the job. Different size dies allow the tube to be notched fast and clean. This method will produce a fast 90-degree notch as well as some angles depending on how it is fed in on both sides. This one makes a very fast and clean cut but it can be limiting if you are trying to get some really sharp angles.

A hydraulic notcher was created to produce a fast clean notch in a portable machine that can be taken right to the job. Different size dies allow the tube to be notched fast and clean. This method will produce a fast 90-degree notch as well as some angles depending on how it is fed in on both sides. This one makes a very fast and clean cut but it can be limiting if you are trying to get some really sharp angles.

The ultimate notcher is a horizontal milling machine type like you see here. It cuts very quickly and produces precise fit ups suitable for TIG welding (which requires minimal gaps between pieces of tubing). The tubing is clamped in a vee block jaw vise and fed into the rotating milling cutter to the desired depth.

The ultimate notcher is a horizontal milling machine type like you see here. It cuts very quickly and produces precise fit ups suitable for TIG welding (which requires minimal gaps between pieces of tubing). The tubing is clamped in a vee block jaw vise and fed into the rotating milling cutter to the desired depth.

Here's a shot of the piece of tubing after the notch has been cut. The vise has an adjustable swivel base so you can present the tube at different angles to get the desired fit. The cut is fast and quiet, and the machine is portable so it can be taken right to the job to save time.  This type of notcher is in use by many major chassis builders in all forms of racing.

Here’s a shot of the piece of tubing after the notch has been cut. The vise has an adjustable swivel base so you can present the tube at different angles to get the desired fit. The cut is fast and quiet, and the machine is portable so it can be taken right to the job to save time. This type of notcher is in use by many major chassis builders in all forms of racing.

 

Source

Mittler Brothers Machine & Tool / 800.467.2464 / mittlerbros.com

 


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