tube notching using CNC mill or waterjet

[Nihal Murthy]

Hello I was wondering if anyone had any experience notching tubes using CNC mill or waterjet/laser machines. I am building a a tube frame vehicle, and was wondering if it was common for anyone to notch the tubes that way. If so what kind of machine or shop would you suggest? If anyone has any recommendations for a shop in or around the Bay Area, CA I would appreciate it.

 

[dsergison]

production is done with robot with a laser. or a laser plasma or water table equipped with a rotary axis (but that's kinda rare for a job shop i think)

handrail and such is typically notched with a tubing notcher, which is a special shear (for handrail and such) but limited to near 90 degree joints.

if you need all kinds of wonky angles, an annular cutter/holesaw/large endmill/sanding drum can be used with a fixture on a mill. either horizontal (typically preffered) or a vertical.

i cant think of any reason a cnc mill would be used. nobody cnc interpolates the fishmouth, and if you had production quantity to warrant the setup a robor or laser would be far more efficient.

 

[metlmunchr]

For the typical sand buggy, etc you can get by with a tube notching fixture and a drill press, or even a half inch drill motor. Its near impossible to have this sort of work done on a one-off basis by an outside shop, because you can calculate till doomsday and still not have the angles right when you fit things up. If a tube has out of plane bends then its far simpler to save the fishmouthing operation until last so the cut will have both the proper angle and the proper angular orientation relative to the tube axis. However, if you started dragging pieces like this into a jobshop for fishmouthing you'd soon find it would be cheaper to subcontract the construction of the entire frame. The Harbor Freight notching jig for less than $50 would get you by for building a buggy or two. There are several jigs on the market that cost several times as much as the HF one, and most of them aren't really that much better. Some of the best and most versatile jigs are ones designed and built by individuals for their own use. There are examples of several of these posted on some of the offroad sites and chopper building sites.

 

[Brandon Dixon]

There is a group that is using a rotary axis and cnc cutter to do tube notching. Pretty nice looking parts. Their website is www.vr3.ca

They seem to be primarily interested in experimental aircraft tubing kits, but maybe they would do a job if you already had a good model.

Brandon

 

[Nihal Murthy]

Thanks for that Vr3 link they maybe very useful for us as they do one-offs and so forth. I also found this
http://www.nextstepengineering.com/applications.html

and these guys that are local, they say they have 6 axis laser cutting. I will see what they can do for me.
http://www.atbending.com/html/contact_us.html


Here are some pictures of what I am looking to build. It is a student built Formula car, for a competition called Formula SAE. Our previous chassis was more complex, with much of the car out of plane and with complex joints. This was a pain to manufacture the tubes and jig the chassis. This chassis is a bit simpler, but we would like to stay away from notching using a hand held drill jig with a hole saw. We have not had good results for the accuracy we were looking for. Our issue also comes to clocking the tube correctly so that both notches end up on the right sides of the tube. Also it will take us a good amount of time to do it ourselves. If we can speed the process up it would be very helpful for us.

 

[jkeyser14]

I have been building similar frames now for several years as part of the baja competition. Here's some useful information. End mills don't work on thin tubing, the flute on one end of the cutter will pull the tubing in, distorting it or ripping it off. I would avoid waterjetting because it would be hard to fixture. We used to use hole saws in a mill, and that worked ok. Our biggest problem was clearance/clamping on parts with bends. It was hard to keep things from being cantelievered too far.

We eventually found that the lathe worked better. We wound up making a clamping tool holder for our Aloris toolpost on to hold the 1 1/4" tubes we use. It's basically a large boring bar holder, but the entire length is split and uses bolts to tighten, rather than having a non-split bore with set screws that can dent extremely thin tubes. We put the hole saw on a mandrel in the headstock and then use the compound to adjust the cut angle in one axis, and a level finder to adjust in the vertical. Using a combination of the two, you can always cut at the proper angle.

Also, when cutting on the lathe, you can use the auto feed at a very slow setting w/ plenty of coolant. This keeps the newbs from destroying the teeth of the holesaw by plunging the cheap HSS holesaws into the hardened chromoly tubes too quickly.

Website:
http://www.umbc.edu/sae/

 

[Nihal Murthy]

Hmm that is a good idea. We had an old Hendy around that would been useful for that, but we got rid of it. Would using a roughing cutter work? Although I don't see how the teeth would be any different.

I've thought about using it on a standard Bridgeport with a collet block holding the tube, but once again the tube clocking becomes an issue. These are all good ideas though. I will think about them.

 

[Ben_A]

We used to notch all of our tubes in a mill. To solve the tube collapsing problem, we turned down delrin or aluminum slugs that slid inside of the tube while notching (maybe a thou under the id of the tube, I can’t remember). This kept the end mill from grabbing the tubing and collapsing it on itself.

As for indexing the tubing around for notches that were not in line with each other, we used an indexing head (something similar to Travers p/n 65-800-388). We made a ‘T’ out of solid stock that we could clamp in the jaws of the indexing head. We would square up the ‘T’ with a machinist square and then simply rotate the indexing head to the desired angle and butt the first notch up with the ‘T’ on the indexing head, and away we went.

On edit: I just went back and saw the title of the post, we did all of our notching on manual machines, you had more of a feel, especially on the thinner wall tubing.

 

[Nihal Murthy]

I have noe problems doing this on a manual mill if I require it. As long as it is decently accurate and not much guess and check. Although having it farmed out to a CNC shop would make our lives easier. Do you have any pictures of the indexing head setup? It seems like a good idea, I am just having a hard time understanding what the T part does.

 

[Limy Sami]

Nihal, having done more than my share of welded tube work, I pondered your question and couldn't really see the advantage, then I saw saw your CAD sketch of the frame.

IMO, unless you have an assembly jig that will hold every piece exactly in place including throughout the welding process,...... not forgetting making allowances for expansion and contraction,........ then any hopes of using a ''kit'' of CNC cut parts would lead to dissapointment, big time.

I know it's a PITA but fitting, fettling (and any other effing you can think of) is part of the job, horizontal mill or lathe and holesaws for the main cuts and a die grinder burr combo is the the way to go.

Tubes not meeting as they should,always look a mess to me, better to take a bit of time and get it right.

Good luck with your project, take care. Sami.

 

[Ben_A]

Nihal

Here is the basic idea:

 

[Mfassler]

At my last shop we used to notch tubes all the time in our mills,put a V in one of your jaws and you should be okay,worked good for us at least.

 

[Wren]

I've done the tubing notching for several FSAE cars and a Baja car. Use an on-size roughing end mill and things should work out ok. Use a dividing head to hold the tubing and put an angle finder on it to get the out of plane cuts working. We had very accurate tube notching this way and the welders were very, very happy. Once we went to this method we were all amazed at how well everything fit up. We were able to almost completely remove the bench grinder from the tubing notching process.

 

[SamH]

I do this for motorcycle and tube car chassis. If it is thin wall, just use a belt sander. For a 90, just do a 45 to the centerline of the tube and then flip over and do the same. I use a combination of a modified tubing notcher with a hole saw, the vertical mill, or a grinder. It is definately a painstaking operation. Good thing is it gets easier every time you do it.

 

[greggv]

jointjigger.com Works great