grinding chassis tubes

[carmaxxx]

What's the best way to grind chassis tubes for a perfect fit?
I've seen some teams with impossibly well ground curve profiles, and I wonder how it's done.
Using a hand grinder will never get you a perfect profile. I had tried getting a 1" OD grinding bit, but i could only find it for a flexible hand grinder, and using it would take ages and ages.
Any suggestions?

[carmaxxx]

What's the best way to grind chassis tubes for a perfect fit?
I've seen some teams with impossibly well ground curve profiles, and I wonder how it's done.
Using a hand grinder will never get you a perfect profile. I had tried getting a 1" OD grinding bit, but i could only find it for a flexible hand grinder, and using it would take ages and ages.
Any suggestions?

[C.Zinke]

We do it by lasercutting. Of course you will need a sponsor for that, but you will get very accurate tube ends. This makes the manufacturing process easier, because the tube fits only in one way. Furthermore you can do "hollow nodes" (See picture). This decrease weight alot.

http://www.lionsracing.de/component/option,com_ponygall.../func,detail/id,664/ (http://www.lionsracing.de/component/option,com_ponygallery/Itemid,68/func,detail/id,664/)

[afroney]

Laser cutting? Thats amazing.

The fab shop that donates our steel offered to notch our tubes with a some sort of CNC tubing notcher. He offered to let us use it next year.

I notched tubes for our chassis this year with a grinder. On a lot of our tubes, I used our mill to notch a perfect slot. This doesnt work on the more intricate angles.

[ttk3]

Lazer cutting and out sourced notching?! All that's needed is a grinding wheel and a file. (patience optional)

[Drew Price]

In the past, our tubing has been notched on what is essentially a huge belt sander, with a cylindrical die the same diameter of the tubing, with a jig at the end to hold the tubing at the proper angle to the die, and a slide to push the tube against the sanding belt to get the proper depth.

All in all, it's an OK process, but a bit imprecise, expecially with how carefully we have had to radially position the tubes for notching the other end.

This year I am going to try putting a hole saw in a mill, like this:

http://bobbrowncycles.netfirms.com/images/shop-pics/mill.jpg



Anyone else do it like this, and any tips?

Tips on other methods, particularly on matching the notches on the two ends to the correct radial angle?

Best,
Drew

[Anday]

We have a similar sanding tube notcher, which is pretty easy as far as a perpendicualar or common angle goes.
We also use angled pieces from the waterjet to place tubes at the appropriate angles for the bridgeport.
Also, we will be starting to use the waterjet to cut angles and square notches. With the right jigging it takes about a minute and a half, instead of a half hour on the mill.
And of course you cant forget the "custom" notches done with a grinder.

No way is perfect but with options it's not too bad.

[SeanM]

I'n my experiances it's been fairly easy using a hole saw on a jig and then fine tuning with either a pedastal grinder or an angle grinder. and to match the two ends of the tubes. the simplest way i've seen is to fit the one side to where it needs to be then mark where the new notch goes and notch the piece with room to spare and grind till it fits.

[Parker]

http://www.pipemastertools.com/

[rjwoods77]

Carmaxx,

Well lets get to the bottom of this. What equipment (mills, lathes) do you have access to? You can pretty much forget about laser for now because if you are asking a question like this then you arent ready for it.

The second question is what are your modelling capabilites? Inventor,solidworks and the better question is can anyone really use it.

Answer these two questions and the answer will be easy to setup around what you have going on. It can be really easy(finding cut angles and walk in distance from cad and cutting with a horizotal mill with corregated cutter) depending on what you got. I started with hand sketches and a pipe master when I started out and now I am rolling pretty nice.

[carmaxxx]

yeah... laser is possible only in my dreams right now.
We have a milling machine and a lathe, apart from a flexible grinder and a hand grinder (these two are manual, so we cant get much out of them.)

We use CATIA for modeling, and yes, we have 3 guys who know it pretty well, apart from professionals helping us out.

[rjwoods77]

Ok you need to use a lathe or a horizontal for it to work okay. If you use a lathe you put the cutter in the chuck (not really safe but oh well) and use a v block mounted on the tool post which in reality replicated a horizontal mill. Vertical mills tend to have too many limitations of angle and mounting bent tubes and such. From cad you determine angle and walk over distance. Basically you mount a tube and clamp it down. Touch the tool off on the surface of the tube ( dont bother indicating it. Just put you hand under the cutter and look for minute shavings comming off) set your zero and walk over the prescribed distance. Use a corregated end mill to keep the tubing from grabing and folding under. That will scare the shit out of you.

Ill describe the CAD thing in soldworks terms. Transfer as necessary. Our tube frame are 2d and 3d line sketches in a part file then use the weldment features to sweep the tubes. For each tube notch you need to understand that the two tubes actually exsist on one plane. Make a plane on these two line segments(click on the three end points of the line segments)to determine you cut plane. On this plane creat a sketch. Figure out which tube is your "cutter". The edge of this tube that is the furthest into the tube you are cutting is your cutter depth. Draw a line from the end of the cut tube sketch to the cutter depth that is perpendicular to the cutter depth. Makes a triangle and shows you your depth of cut by clicking on that line. Before you even get there, find out the line segment length of the tube and cut that on a lathe,saw,whatever. Basically use the edge of the tube as a locatiion edge so get a nice square cut.

We got this process down nice and got spectacular results. Actually I was able to step back and direct 5 people at once to get stuff done. I had one guy cutting the tubes on a saw to rough length. 1 guy on the lathe sizing the length of the tube correctly. 1 guy cutting to my specs off a piece of paper on the mill and the last guy deburring and fianl fit filing. We cut the real quick and they were dead accurate with a minimum of grinding.

[jwill211]

bridgeport with a 1" end mill and digital protractor for crucial notches, regular tube notcher with a hole saw and then file to get the exact fit I want for not so crucial joints. Be patient, enjoy it, after a while you can get a perfect fit every time with just a half round file...

[rjwoods77]

The fitment of your tubing is directly related to warpage due to welding. The filling in the gap attitude is the wrong one to have. When you bridge gaps all you are doing is pulling the tubing all over the place which really pre stresses the tubes. By the time you are done with the car that ends up being alot of pulling. If you read up of weld cerification/qualification you arent allowed a gap period. It is grounds for fail in alot of cases. Fusion welding is the melting of 2 similar metal and adding a third to the mix. Not melting one, adding a second and hoping it bonds well with the third. Might as well call your frame soldered at that point. Joint fitment is crucial for alot of reasons and you should be anal about. Will it matter for our type of cars in terms of performace, probably not. But that is no reason to do things wrong.
We are still in the process of revising our site but look in the 2006 picture section to see how we were doing things. We were drilling little holes to vent gases when welding.

http://www.eng.buffalo.edu/Students/Organizations/sae/f...bum/player_black.swf (http://www.eng.buffalo.edu/Students/Organizations/sae/formula/Album/player_black.swf)

[KU_Racing]

Easiest way? get them laser cut, or buy a purpose built tube notcher. www.mittlerbros.com (http://www.mittlerbros.com)

[jpventuri]

It's as simple as printing out a real size flat pattern of your tube and then wrapping the tube with it.

Then you get yourself a little cutting wheel and go to town, finish with a sander, and then wire wheel for welding and it's all done. Some post fitting may be required.

Also upstairs we have a special tube notching device with a 1" end mill on it mounted horizontally. The best kind of end mill to use are the "rough cut" end mills, that have ridges down the cutting face.

Once you get the hang of it, it becomes pretty easy

[Jersey Tom]

Pipe master, grinding wheel, die grinder. Some of the fitup has been great this year.. real tight, real easy clean welds. Some has been.. not so nice. But in the interest of time, rollin with it anyway.

We also have a purpose built tube notcher but for the really complicated nodes it doesnt do much good.

[JerryLH3]

We use either a cutter in the lathe or take the tube over to the bench grinder. Sometimes, when something is required to be in a jig, we'll touch it up with the Dremel to avoid taking it in and out of the jig so many times.

This method takes patience and I think of it as an art form. You have to have a good eye for how the tubes will fit together.

[Ian M]

Tubing notcher, angle grinder, and cutoff wheel used here. Pretty sure we got the tubing notcher from Harbor Freight and it has worked great. We have had races tubing notcher vs. angle grinder to see which one is faster, more accurate and it is pretty equal. Just have to figure out what angle each tube is meeting up with another tube and set that on the tubing notcher or have a little experience on the angle grinder and a good imagination.