[benchracer1]

Anybody have any good methods for accurately fishmouthing tubing short of buying expensive notchers? I am relatively new and find marking the tubing to be very frustrating.

[tm454]

then how much would you use it after doing the job your doing now? Are there any chassis builders around you...maybe they could cut your notches for you. This is for a roll cage right?


Tazz


Rat Rods Rule!

[ONEBAD70SS]

If you're trying to notch the frame by putting a half-circle notch in it, here's some tips. first find and measure the area youy need to notch. Next, take a piece of tubing,..(find needed size.) place it on the side of the frame rail, hold it there and outline around it....This will give you a diagram to cut. Make your cut into the frame rail. Nexttake that piece of Heavy guage pipe that you used for the outline. Measure it carefully and cut it down the center so you have 2 halfs. Take the half place it into the frame rail,.. you will need to grind to clean the cut up and make a nice fit. Tack weld the pipe into place and cut the overhanging ends off. weld the piece of pipe into the frame and make sure you get a good, heavy weld. Then grind, clean as needed. Hope this helps!

[broncoII88]

You don't want a heavy weld. Unless you're making a multiple pass fillet weld with a stick welder. Excesive bead reinforcement wil weaken the joint because of distortion from the amount of extra heat. A mig welder is the easiest to use, but can be weak due to the fact that the wire can go anywhere in the joint and you may not get full penetration. Tig welding is best for welding tubes together because it penetrates the whole thickness of the metal, but it's the hardest method. If you want to save time and don't want to mess up your project just have a chassis shop do it. But make sure it is an acredited shop first.

[BillyShope]

Believe it or not, a fellow actually BRAZED a "space" frame for an SCCA class-winning sports car! Consider how good those fits had to be! Personally, I've become quite adept at filling large gaps with a torch and rod "weaving" technique. I would only trust a torch (and TIG, I suppose) for filling large gaps with thin wall tubing. I just don't trust MIG or a stick for that sort of thing, though I know many will insist they can do just as good a job.

What I'm trying to say, I guess, is that I have faith in my torch abilities and don't spend a whole lot of time attempting to get a "brazeable" fit.

[19_Chevelle_69]

It's not an industrial quality one, but for $30, it would do exactly what you need.... Harbor freight notcher

I have one that is made by a different manufacturer. A bit more quality for a bit more money...

Here's an example of mine... Speedy Notcher

[astroracer]

I got my http://www.harborfreight.com/cpi/cta...emnumber=42324
off eBay for $16.00...

[Max Keith]

One method Ive used for notching tubing is to take a piece of cardboard (Cheerios box works great), wrap it around the end of the tubing, then slide the carboard against wherever Im wanting the tubing to fit to. Then I will cut the carboard to fit to the desired location. You can first trim the carboard to the general profile of your contact area, then use an exacto knife to get the precision designyou need. Use this as a template to cut and grind your tubing. It can be tedius, but short of purchasing a notching jig, thats about the best I can come up with.

[daimon1054]

astroracer beat me to it, the harbor freight unit is nice but I would recoment buying a better set of hole saws than HF sells.

[astroracer]

I buy my hole saws from Enco...
http://www.use-enco.com/CGI/INSRIT?P...PMPXNO=3008824
High quality and a decent price.
Mark

[broncoII88]

Yeah but hole saws will wander from the tube unless you have a 100 pound vise clamped to the drill press table. If you don't want to invest in a notcher which has a special built in vise, then just cut a triangle out of the end to be notched and fine tune it with a grinder. It will take longer, but you'll get the same result.

[daimon1054]

30 bucks for the HF notcherand a hand drill and it works great so why fight the grinding?

[53LEDSLED]

i had a hard time doing the notching my self. what i did is cut the pipe (flat)at the angle it was going to go at and do the rest with an air grinder, i did take a little longer than i thought but i didn't have to do too many of them and i knew that i was going to do any more after this.

call Production Tool Supply 1-800-366-2600, i think they have one for under 70 bucks

[Max Keith]

Since your hole saw is designed to have a drill bit runnig down through the center of it, cut your tubing long, you can make a witness mark in the tube with a punch, to center your drill bit. This will stop the saw from dancing all over the place.

[Mule76]

Noone has mentioned the chop saw method which is what I use the most. Here is how it works.
The chop saw method,if understood , is a science. With known tube size and joint angle, tube can be notched with great accuracy. The notch is acheved by cutting two opposing angles on one end of a peice of tube, to form a point. The cross-section of this cut will be an elipitical cut due to the shape of the tube. Changes in both of the two angled cuts must be made for the intersection angle and the size of the two tubes being joined. The only real limitation is the max angle of the chop saw.

You start with what I call the base angle. This is the angle of boath cuts if the joint was 90*. For an example, I am fitting Two tubes together that are boath 1.75", at an 90* joint. The base angle, or the angle of boath cuts is 28*. These two cuts must meet at a point, and the point must allso be centered on the tube.

What if I want an 15* joint with my 1.75" tube???? You must start with your base angle, witch was 28* for 1.75"(remember above), and subtract 15* from one cut, and add 15* to the other cut to form a perfect notch. So now I must make a 13* cut and an 43* cut , with the point centered on the tube. Perfect coped joint, to get the fit absolutley tight you may have to take a grinder and grind down the inside of the coped tube along the points.

Remember your base angle will change with the tube being cut and the tube that you are fitting to.

Here are a few examples of base angles...

2.0" to 2.0" tube, base angle of 30*

1.75" to 1.75" tube, base angle of 28*

1.5" to 1.5" tube, base angle of 26*

1.25" to 1.25" tube, base angle of 22.5*

1" to 1" tube, Base angle of 20*

Now to fit diffrent size tubes together

1.75" to 2" tube, base angle of 25*

1.75" to 1.25" tube, base angle of 45*

1.25" to 1.75 tube, base angle of 20*

1" to 2" tube, base angle of 12*

And for more complicated cuts I will use a program that prints out a template and then mark the tube and plasma or grind the cut out of the tubing. I don't remember the name of it but it is free on the web.