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  1. #1
    Senior Member ftwelder's Avatar
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    miter grinding machine.

    I needed one of these for cutting some thin tubes so I made one over the holidays for myself!

    I found the idler wheel on an old piece in printing machinery but it's just a .120 wall tube that I added some contour to. The contact wheels are just aluminum bar threaded in the end for a paragon hole saw arbor. The tensioning trolly rides on long shoulder screws that allow belt tensioning with no tools.

    The main frame just clamps on the quill like a seat post clamp.

    I made it to fit standard hardware store belts and used pieces of material on the shelf so I could see if it works and it does just fine. The low quality belts are sort of a drag and I may have to turn down the contact wheels when I get some decent X backed belts.

    Enjoy!


    29 1028 by frankthewelder, on Flickr


    29 1026 by frankthewelder, on Flickr


    29 1032 by frankthewelder, on Flickr


    29 1033 by frankthewelder, on Flickr


    29 1034 by frankthewelder, on Flickr
    1886 Surrey machinists Invincible, 1900 Nashua, 1937 Raleigh Golden Arrow, 1938 Raleigh Silver Record, 1951 Armstrong tourmalet, 1970 Motobecane Grand Record, 1971 Raleigh Professional, 1971 Gitane TDF, 1972 Legnano Gran Primio, 1973, Peugeot PX-10, 1975 Roberts, 1984 Battaglin Giro, 1985 Grandis Speciale, 2012 FTW

    frankthewelder@comcast.net

    le prix s'oublie,la qualité reste ,(michel audiard)

  2. #2
    Randomhead
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    That's really nice.

    took me a while to figure out you were cutting on the quill side, I'm slow.

  3. #3
    Andrew R Stewart Andrew R Stewart's Avatar
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    Neat little set up!

    There has been some discussion about hand mitering over on Velocipede Salon lately where Dave B mentioned his belt miter rig. A good resource for mitering processes for a newbie on a files only budget. Andy.

  4. #4
    Senior Member ftwelder's Avatar
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    I love mitering tubes by hand. I learned on bigger tubes. I miter these roll cage tubes with a chop saw and a 20" disc grinder. I have built ten or more car chassis.


    IMG_1780 by frankthewelder, on Flickr
    1886 Surrey machinists Invincible, 1900 Nashua, 1937 Raleigh Golden Arrow, 1938 Raleigh Silver Record, 1951 Armstrong tourmalet, 1970 Motobecane Grand Record, 1971 Raleigh Professional, 1971 Gitane TDF, 1972 Legnano Gran Primio, 1973, Peugeot PX-10, 1975 Roberts, 1984 Battaglin Giro, 1985 Grandis Speciale, 2012 FTW

    frankthewelder@comcast.net

    le prix s'oublie,la qualité reste ,(michel audiard)

  5. #5
    Senior Member calstar's Avatar
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    Very nice. So you machine the contact wheels out of al bar stock to the radius you need for a specific miter, correct?

    "I needed one of these for cutting some thin tubes..."

    Do you need this because a regular cutter distorts thin tubing?

    Off subject here, but in the flicker pictures just before the grinder the red/maroon bike is a gorgeous color. Is that a clear powder coat with a tint that allows the heat coloration of the tubing to be seen? Very, very nice effect!

    thanks, Brian





    "The older I get the better I was" (from Old Guys Rule t-shirt)

  6. #6
    Senior Member ftwelder's Avatar
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    Quote Originally Posted by calstar View Post
    Very nice. So you machine the contact wheels out of al bar stock to the radius you need for a specific miter, correct?

    "I needed one of these for cutting some thin tubes..."

    Do you need this because a regular cutter distorts thin tubing?

    Off subject here, but in the flicker pictures just before the grinder the red/maroon bike is a gorgeous color. Is that a clear powder coat with a tint that allows the heat coloration of the tubing to be seen? Very, very nice effect!

    thanks, Brian



    Correct on the contact wheels being made to specific sizes.

    Over the years I have run across a few challenges with using hole saws. I usually buy one, straighten it, remove the paint, grind it to size, cut down the rakers and make the teeth smaller. It is sometimes still difficult to pick one that is perfect for the task. I have some swiss made ones that are good but there are still diameter limitations.

    I also shape frame tubes a bit and the hole saws are sketchy when cutting non-round shapes on .8 or .7 walls. Annular cutters or high-helix mills can work on thin round tubes but about half way through the tube things go bad on shaped tubes.

    The finish is powder paint. It is part of a two-coat system but we use only the tinted clear coat. It is called lollipop. Thanks for the kind words. The frame is for Angie, she won two national downhill pro titles for me so that bike is her christmas gift from the team.


    29 921 by frankthewelder, on Flickr
    Last edited by ftwelder; 01-05-13 at 04:50 AM.
    1886 Surrey machinists Invincible, 1900 Nashua, 1937 Raleigh Golden Arrow, 1938 Raleigh Silver Record, 1951 Armstrong tourmalet, 1970 Motobecane Grand Record, 1971 Raleigh Professional, 1971 Gitane TDF, 1972 Legnano Gran Primio, 1973, Peugeot PX-10, 1975 Roberts, 1984 Battaglin Giro, 1985 Grandis Speciale, 2012 FTW

    frankthewelder@comcast.net

    le prix s'oublie,la qualité reste ,(michel audiard)

  7. #7
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    I made mine as a detail wheel set for my 2x72 grinder. It runs at full speed and power and tubes could be swallowed whole. I just freehand on it, since not two builds are ever the same. The first step is to get the tube floating on the turning belt. I then bump it, and make corrections for tilt or centering. Once I have it running true I just feed it in. It is pretty easy compared to this (around 5 minutes):

    http://www.youtube.com/watch?v=kvlKfzW12d0

    I have to grind some broadheads for a guy, so I may get a pic today.

  8. #8
    Senior Member ftwelder's Avatar
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    That video is impressive. The surface speed is really the information there and the hand work is like any master craftsman. Utterly amazing to the layman and way harder than it looks!

    I really enjoyed watching him do the hollow grind. I have fooled around with that on my burr king grinders but getting the part same cut multiple times with the same coverage has evaded me. I was amazed at the material removal rate without a burr on the back-side during the profiling. Thanks for sharing that.

    I don't really understanding what you are describing for your process.

    When I freehand miter I use a belt on platen or disc and grind the profile that (on a bike) would be seen from the side of the bike. On the roll cages I use a chop saw and make two cuts and finish it on a 20" disc then tamper a bit with a big 1/2 round file.

    'pics would be great!

    I will try to get a film of what I am describing also!

    This was something fun from a couple of days ago. I bent and mitered these tubes on this piece of medical equipment for these two brilliant young engineers. We went through the steps one by one to get the information I needed out of this massive 3D drawing to make these tubular parts that were pretty basic compared to a bicycle chain stay.

    I did the two end cuts on the long bent tube like a typical machine shop would then the lower miter on the long up-tube and both cuts on the smaller tube were done by hand. It took two days to bend, ovalize one end and miter the main tubes and no more than 5 min to do the last three miters on the little home made belt sander in the background.


    29 1037 by frankthewelder, on Flickr

    Two more fun things in the photo is the bottle brush and touch up grinder way back in the photo. The bottle brush is a motorized reciprocating wire brush with about 2" of stroke. The machine on top is a regular bench grinder mounted up at eye level so I can really see to do fine work.
    Last edited by ftwelder; 01-05-13 at 07:18 PM.
    1886 Surrey machinists Invincible, 1900 Nashua, 1937 Raleigh Golden Arrow, 1938 Raleigh Silver Record, 1951 Armstrong tourmalet, 1970 Motobecane Grand Record, 1971 Raleigh Professional, 1971 Gitane TDF, 1972 Legnano Gran Primio, 1973, Peugeot PX-10, 1975 Roberts, 1984 Battaglin Giro, 1985 Grandis Speciale, 2012 FTW

    frankthewelder@comcast.net

    le prix s'oublie,la qualité reste ,(michel audiard)

  9. #9
    Senior Member calstar's Avatar
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    ftwelder:

    "The surface speed is really the information there and the hand work is like any master craftsman. Utterly amazing to the layman and way harder than it looks!"

    +1 Unbelievable how fast he cuts his blank. Master craftsman is right!

    Another question Frank: when you turn/machine the drive wheel does it need a slightly crowned surface to keep the belt centered like most woodworking belt sanders have?

    thanks, Brian
    Last edited by calstar; 01-05-13 at 07:40 PM.
    "The older I get the better I was" (from Old Guys Rule t-shirt)

  10. #10
    Senior Member ftwelder's Avatar
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    Quote Originally Posted by calstar View Post
    ftwelder:

    "The surface speed is really the information there and the hand work is like any master craftsman. Utterly amazing to the layman and way harder than it looks!"

    +1 Unbelievable how fast he cuts his blank. Master craftsman is right!

    Another question Frank: when you turn/machine the drive wheel does it need a slightly crowned surface to keep the belt centered like most woodworking belt sanders have?

    thanks, Brian
    Only the jockey wheel is drum shaped. The contact wheel is cylindrical.

    I am going to buy some #40 belts and a chunk of 440C and give that a try some day. That looks fun.
    1886 Surrey machinists Invincible, 1900 Nashua, 1937 Raleigh Golden Arrow, 1938 Raleigh Silver Record, 1951 Armstrong tourmalet, 1970 Motobecane Grand Record, 1971 Raleigh Professional, 1971 Gitane TDF, 1972 Legnano Gran Primio, 1973, Peugeot PX-10, 1975 Roberts, 1984 Battaglin Giro, 1985 Grandis Speciale, 2012 FTW

    frankthewelder@comcast.net

    le prix s'oublie,la qualité reste ,(michel audiard)

  11. #11
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    Frank. I forgot about this yesterday, once I got into the shop. Sounds familiar?

    I can grind a knife, at least an easy one (have not even tried a dagger), and it isn't that tough. The other day I was trying to grind some broadheads, and to my great surprise I did no get good results, so I made up a jig for that. Sometimes grinding needs a jig, and at other times fairly intricate results are possible freehand. In addition, a friend came by with a 6-pack and 18 broadheads he wanted ground, a jig started to make sense.

    A basic thing with grinding, in my mind, is to learn how to float the tool on the wheel with little or not cutting taking place. So in the case of the Entek knife, imagine holding the completed rough ground blade on the spinning wheel but with very little cutting taking place. I call that floating.

    So to grind a profile one needs to present the unground blade/part to the grinder in the exact same position as it will have when the grind is completed. a) grind in the finish position all the time, there isn't some initial position that is then converted to the final position (except that sometimes a sharp corner would rip off too much grit, so the first contact may need to be altered to blunt the workpiece.) b) initially grind just enough material to seat the workpiece on the wheel, then check to see that the workpiece is lined up. In the case of the tubes for bikes, one needs to center the tube, if the mitre is centered; ensure it is aligned to the clockface so 90 degrees or coplanar with the opposite end; and ground to a level depth on both sides. c) Once you have the piece floating on a cut that has the correct position, you can press it to near full depth. d) Then with one final check of everything, you get a small space to tweak it to perfection. This is easier than it sounds, with a little practice, and of course one way to go is to lay-out the mouth with a sharpie, so you can steer it right to that point. But I prefer to mark only depth, and depend on the approach suggested.

  12. #12
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    This is the full KMG grinder, I have the 10" contact wheel for it, and angle adjust platten, but I figured I would save some money on the detail wheel set by making it myself. I did a pretty nice job. At the time all I had was a drill press, and the grinder, and an AC 70 amp stick welder.



    The details wheels are mounted on 5/16" bolts. I made the initial ones out of rubber from wheels for sleeve sanders for a drill press These work pretty well for general stuff, but for miters, one wants precise wheels that have the same diameter with the belt in place as the cope itself. I was able to make those when I got a lathe. I also use a wheel that consists of just the bolt mounted. This gives a 3/8" cope for racks.



    The great thing about belts is that the speed is determined by the drive wheel and motor. This thing cuts as fast as the unit in the Entek video above, or at least would with the same motor. It does not mater whether you run a 16" wheel or a 3/8" one, it rips right into metal with perfect control.

    The bad thing is dust. It could be worse, since quality belts are very durable, and do not disgorge much dust. My welding, and bike building is pretty much a fair weather activity, so I wheel my grinder out of doors if I need to waste a lot of material. Of course on can extract a grinder, as in the entek video. But that is not on my to do list. It would get complicated in my cold climate. I prefer just to give it a rest for a few months a year. Now I have a mill to cut copes, or a file. I can still do the little weird cuts in the winter if I like, they don't stir up much dust.

  13. #13
    Senior Member ftwelder's Avatar
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    Massive, thanks for sharing. That is an awesome machine! I looked at my Burr king machines and there is no vented contact wheels on either.

    I noticed the way many of the grinders I see (like yours) have that removable/changable column. That is what I need to be doing.

    I don't have a big dust problem yet..
    1886 Surrey machinists Invincible, 1900 Nashua, 1937 Raleigh Golden Arrow, 1938 Raleigh Silver Record, 1951 Armstrong tourmalet, 1970 Motobecane Grand Record, 1971 Raleigh Professional, 1971 Gitane TDF, 1972 Legnano Gran Primio, 1973, Peugeot PX-10, 1975 Roberts, 1984 Battaglin Giro, 1985 Grandis Speciale, 2012 FTW

    frankthewelder@comcast.net

    le prix s'oublie,la qualité reste ,(michel audiard)

  14. #14
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    [Partial QUOTE=ftwelder;15121771] The finish is powder paint. It is part of a two-coat system but we use only the tinted clear coat. It is called lollipop. Thanks for the kind words. The frame is for Angie, she won two national downhill pro titles for me so that bike is her christmas gift from the team. 29 921 by frankthewelder, on Flickr[/QUOTE]

    FTWelder; That lollipop paint is insanely awesome...any chance you would be willing to do a basic thread to show how you do it? I just keep staring at it like it was one of those crystalline skulls from the Indiana Jones movie...and wondering "how he do that?"

  15. #15
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    Thanks FTW. The KMG grinder, as you probably know, is a respected brand that started as a Knife Makers Group, no weld project. There are plans all over the net on this baby. As you can weld, it is even easier for you to build. KMG sells parts for those who do not want to buy the commercial version they have now come to offer. Ebay also has all kinds of cheap deals on motors and controllers. A key to these machines is a big variable speed motor. I like to run mine out of doors, so I am limited to 110, and 1.5 hp. Otherwise I would have a 3hp motor. Of course I am talking general use, tubing does not have much heft to it.

    I want to make a 1x42 machine to the same standard, as I use that belt size a lot, and it is much cheaper for me to source the belts, and it is wide enough to do a lot of, admittedly mostly non-tubing, things. The serious abrasives are available in 1x42. Though the selection of 2x72 is uneatable, and in the US you would not have any problems getting the stuff.

    What about this guy, note the double shaft design:

    http://www.polarbearforge.com/grinder_kit.html

    This is the wheel I am going to use on the 1"

    http://usaknifemaker.com/grinders-sa...el-70duro.html

  16. #16
    Senior Member ftwelder's Avatar
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    I do production welding for a place that does laser cutting and there is a water-jet guy in the area also. got a kick out of his masterlock concept grinder. (polarbear) I almost gave up on finding pics but it was worth it.

    Where I am, there are a lot of old machines/tools everywhere. I have lots of industrial hardware in a pile out back so I really try not to pay inbound shipping on steel. My biggest problem is paying for items where the seller demands I take a machine "for it's own good" and pay for it at my leisure. I also have this rolling machine that belongs to a friend who hasn't been around for months.


    29 350 by frankthewelder, on Flickr


    I built a frame using the grinding machine and it worked pretty well. The belts were total crap and a bridgeport is tragically slow but it worked. The frame was my first with heavier forming operations on this new Columbus tubes. I didn't pick them but the buts are very short and the tubes are wicked thin.

    The fits were awesome and I hippy welded it, single pass with no blow-outs and only some minor touch-ups.

    It's hard to tell but I formed each of the tubes in several directions. It fits big tires with racing geometry with plenty of ring clearance. I gas brazed the bridges and small parts. Because the lack of butt length, I didn't have the material to wrap the widened top tube around the head tube so I "pinched" the bobbed ends of the tube in the vice and simultaneously swung the tube as I closed the vice, forming the odd endwork on the front side of the top tube.

    There was several magical moments building this frame. I didn't think about photos. It was one of those building sessions where I met only my most basic personal needs and everything else went into the frame. It was rad.

    The top of the seat tube is a very short, thick sleeve that gets a bigger slot with exclusive anti-propagation technology (BS) and the chain stays are "perasymmetrical" (a new word I just made up, it means the part (chain stay) itself is not symmetrical but two of the same are used) and the seat stays and head tube are regular bits.

    Ill return with the images. Fliikr is bogging
    1886 Surrey machinists Invincible, 1900 Nashua, 1937 Raleigh Golden Arrow, 1938 Raleigh Silver Record, 1951 Armstrong tourmalet, 1970 Motobecane Grand Record, 1971 Raleigh Professional, 1971 Gitane TDF, 1972 Legnano Gran Primio, 1973, Peugeot PX-10, 1975 Roberts, 1984 Battaglin Giro, 1985 Grandis Speciale, 2012 FTW

    frankthewelder@comcast.net

    le prix s'oublie,la qualité reste ,(michel audiard)

  17. #17
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    Here is an interesting take, post 58

    http://forums.dfoggknives.com/index....ic=4436&st=40&

  18. #18
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    Quote Originally Posted by MassiveD View Post
    A key to these machines is a big variable speed motor. I like to run mine out of doors, so I am limited to 110, and 1.5 hp. Otherwise I would have a 3hp motor.
    One of the useful items in my shed is a small single phase input to three phase output VSD rated for 2.5 kW (3.3 hp), allows me to run fair size motors on an extension cord if required. I'm in a 240V country but I think it's also rated for 110V input

  19. #19
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