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MTech notcher?

Discussion in 'The Garage' started by ntaj*ep, Feb 2, 2003.

  1. ntaj*ep

    ntaj*ep 1/2 ton status

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  2. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    I've got a $25 HF version that looks almost exactly like the one you posted and it works very well. I find that I don't use it very much, mostly I use the chop saw and hand grinder. It's worth the $25 I paid, and nice to have when I need it, but I'm glad I didn't spend a lot on it...
     
  3. m j

    m j 1/2 ton status

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    If you have time could you elaborate on your technique?
    it seems to me that it would take a very steady hand to get a tight fitting joint
     
  4. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Hmm, not that hard really. Lots of different things depending on the joint. For 90* joints, I set the chop saw on 45* and cut 2 45* "ears" (the scrap pieces look like cat ears) off the end of the tube, leaving about 1/3 of the flat end of the tube untouched. Then a hand grinder on the inside of the untouched area is needed to open it up just a bit. Works great, and the 45* cuts leave a perfect 45* bevel on the sharp angles of the joint for a strong joint without being limited to a single outside fillet, while the uncut end gives plenty of access on the sides. For smallish variations off of 90* (up to 30* or so), it's a bit more trouble. It just needs some simple angle adjustments on each side to account for the joint angle, and generally more hand grinding is required, but I've found that after a few joints were done, it became pretty easy/fast to "eye-ball" the cut. Once you approach 45* on the joint, you no longer worry about the outside notch since the tube's shape works fine, but the inside needs an pretty sharp angle cut off, more than the chopsaw can handle, so it requires more grinding. A few test fits and it’s done.

    As for having to be careful, and requiring a steady hand, not really. Most of my joints fit pretty good with maybe a little more than 1/16" gap at any point on the worst. I don't mind that at all, it just gives me a chance to start deep and get a good weld the width of the tube wall. Joints made by the notcher fit *too* well for my liking. If you cut deep into the tube, the "points" left by the hole saw are VERY thin. That's not where you want to be welding, so you have to grind back to solid metal there anyway. If you don't take a deep bite with the hole saw, you don't have to grind off the sharp edges to get to solid metal, but you do fit up tight in the crotch of the joint. If you don’t bevel this area, you have only a single outside fillet. Properly done, this wouldn’t be a problem. If you don't have everything set perfect, your going to be blowing through trying to get a good strong weld with enough penetration (at least I do, generally going over board being paranoid). I'm just not comfortable enough with my ability to achieve full strength joint in a roll cage with a single outside fillet. I *think* I can, but tube is a pain to weld anyway (EVERYTHING is constantly changing on the way around) and I would rather be as certain as possible that I get the strongest weld possible.

    Hope that makes sense.
     
  5. ntaj*ep

    ntaj*ep 1/2 ton status

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    So your saying basiclly with the notcher you have your having to cut down the "ears" to get it where you'd like to see the fit?
    I think I get it, however I think with as much as this will get used I would rather spend the money and get a slightly better unit. Thanks for the HF reminder though /forums/images/graemlins/thumb.gifI totally forgot about them till you said something. i think I'll get my work bench and vice from them. /forums/images/graemlins/thumb.gif
     
  6. 70~K5

    70~K5 1/2 ton status

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    MJ and others interested. The Feb. 2003 issue of Dick Bergren's SPEEDWAY Illustrated has an article starting on page 78 on 3 ways to notch your tubes. 1. sawing, 2. shearing, and 3. hole saws. Plus they show how to make a template out of a cardboard roll for odd spots. It was worth the cost of the mag to me for this article. Has lots of pics too, to go with the writeup. /forums/images/graemlins/thumb.gif
     
  7. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    No, it will fit perfectly if you use the right size hole saw. But, if you notch it deep with a hole saw the same size as the tube (which is typical) then the "points" or "lips" of the fish mouth will be razor sharp. Not much good for welding, so you have to grind/cut those back to full width metal wall. And, as I said earlier, in the bottom of the "fish mouth", where the notched tube will form the sharp intersection with the mated tube (i.e. the point of the wall intersection that is on the plane defined by the center line of the 2 tubes) you will basically have a "T" joint where you can only fillet weld one side. To avoid that, you have to bevel that part and taper it into the flattened "lips".

    That's why I like the chop saw and grinder approach. It's often about the same or less work, much faster, no expensive bi-metal hole saws to fool with (if you don't notch deep, you gotta be careful or it will spit teeth), no messy cutting oil to make the saw live, no reversing the tube for a back side cut because the hole saw is not deep enough for anything other than 90* cuts (just try to find a 1.75" saw deeper than 1.75"), and of course you need a drill press that can turn around 200 rpm and has a huge throat to use the notcher right. You can do it with a hand drill but, it will turn too fast and you'll dull saws rapidly.

    Hope that makes sense...
     
  8. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Cool. Can you (or someone) scan in the article and host it somewhere? If someone can scan it, I'll host it...
     
  9. 70~K5

    70~K5 1/2 ton status

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    Russ if I can get my daughters scanner to work I'll email it tonight.
     

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