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cutting circles in 1" plate

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  • jdunmyer
    replied
    If you have a mill, a hole saw works great up to 6" and 1" thick. Sawing a plate that's more than about 1/8" thick requires a couple of holes to allow the swarf to fall out. Put the hole location so that its OD intersects with the kerf of the hole saw, either inside the circle or outside, depending...

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  • Arthur.Marks
    replied
    Just noticed there's one of the multi-tools for sale used here:
    http://cgi.ebay.com/APT-Multi-Tool-H...2#ht_500wt_922
    Nice guys to deal with. Been to their shop many times.

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  • darryl
    replied
    I read about making your own holesaw using sections of bandsaw blade attached to a suitably sized disc. I have tried that in a small way and it works. One difference between that and a regular hole saw is that you can have a lot less teeth in the workpiece, so with reasonable pressure, each tooth gets a proper bite into the steel. Also there's way more clearance in the kerf because you'd only have sections of toothed blade and not a full hoop.

    I don't see my experimental tool right now, but I believe what I did is drill and tap around the edge of a metal disc, then grind a slot in both ends of the bandsaw blade sections. The bolts hold each section in place, putting the curve in them as they are bolted on. That makes them align properly and the teeth have the same type of clearance that they did in use as a bandsaw blade.

    I have made several types of trepanning tools over the years, most of which are a single cutter on the end of an arm, basically. To balance the forces, you could start with a piece of bar, length to suit the diameter of the hole you need to make, then round each end and attach a blade section to each end. The bar is mounted to the mill spindle in whatever way it can be made rigid. You could machine a recess in a metal disc such that it would be a close fit to the end of your spindle, then use a drawbar to keep it there. The piece of bar would be fixed to the disc, possibly being threaded through along with the disc for the drawbar. In my case, this has resulted in the most rigid tool mounting method, better than using a morse taper adapter. In one case I used both a short tapered stub and the recessed disc to fit my spindle.

    In any event, this bar with two cutters will be evenly loaded when cutting, so the possibility exists for smoother cutting action. The bandsaw blade sections that you bolt on are replaceable, so it's basically a matter of getting your attachment method figured out. Drilling the blade sections is not usually an option for me, but grinding a slot in each end is easy. When the length of each piece is right, and the depth of the slots is right, the fit can be very close. You should be able to find bandsaw blade sections without too much trouble- a local shop gave me a few pieces which were either leftover from making up blades, or pieces from where they had damaged a blade and it couldn't be used on their machine. Either way, you basically get new teeth, or at least perfectly usable teeth, and probably HSS of a good grade.

    Depth of cut will obviously be limited to the width of the blade material less the bar thickness. You would probably have to make sure if you turn the material over you can center it again so the cuts meet. You also have the option of grinding away some of the teeth from each blade section to leave an appropriate number of teeth for the best cutting action with the available torque from the machine.
    Last edited by darryl; 12-11-2010, 03:22 PM.

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  • KEJR
    replied
    You should ge able to make your own trepan tool for the mill. I'd think you could make one with some large rod stock. You'll want to make sure it is rigid and well secured and fairly balanced. Run it at real low RPM until you are sure it is working well. I think you can make your cutter bit out of 3/16" or 1/4" round drill blanks. I'm not sure what cutter geometry would work well but you could experiment. Something tells me you would want to back grind your cutter so that it has clearance like a lathe parting tool does.

    A guy I know turned a small diameter trepan tool on the lath out of O1 and then hardened it with a torch. I think it was for making 1" discs. It kind of looked like a hole saw but with 2 large teeth and was alot more rigid. You really only have to harden the two teeth and then temper them and grind to sharp.

    Edit: Toolguy already suggested it, but a rotary table can make these cuts with an endmill. If your stock is precut (bandsaw) to be just above your size you only have to cut off the corners.

    KEJR
    Last edited by KEJR; 12-11-2010, 02:39 PM.

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  • David Powell
    replied
    An easy but slow way----

    Is to use a holesaw. Put blank in chuck, centre drill, then hold holesaw in tailstock chuck, drill centre hole, put lathe in backgear, cut half depth of holesaw teeth, withdraw, tap holesaw with chuck key or small hammer so that the swarf in the teeth falls off or/ and brush teeth with disposable paint brush, put a few drops of cutting oil on if cutting steel and repeat until about half way through, reverse the part and repeat until you are through. IF you go all the way through the blank you cut out may wedge very firmly in the saw, if you reverse it it will fall out easily, dont ask why, I really do not know! If you are gentle even cheap hole saws will work well, it MAY speed things up if you grind off every other tooth. If you try to take too deep a cut you will BREAK off some teeth and maybe jam the saw very firmly into the work. Some machinists have told me this is not a " proper" procedure but it works for me. Regards David Powell.

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  • Abner
    replied
    Trepanning looks like the better option if I want to do it myself.I have both a mill and a lathe. If I don't want to buy trepan tooling I could use my lathe.

    The cutter shape - any details? looks like it would be easy to get vibration.

    I like the idea of buying discs, I guess I will have to get off my wallet
    Last edited by Abner; 12-11-2010, 07:49 AM.

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  • wierdscience
    replied
    Originally posted by Abner
    I figured as much, I just get tired of the clean up.
    Pulleys mainly for cable and odd mechanisms so sheaves wouldn't work.
    I should just go buy some 5-6 in shaft for the bigger ones.
    Thanks
    I do cable sheave sizes up to 18" OD on a regular basis.The ones up to 12" I buy from a metal service center,cut from round bar.They can saw and deliver as many discs as I need for not much more than I pay for the steel plate it would take to make them myself.Plus there is no hard skin.

    I use-
    http://www.southerntoolsteel.com/

    The best part is I can get any alloy I want,for pennies more with no nasty torch scale to waste tooling on.

    The 12"+ sizes I have laser cut,much,much less slag than gas or plasma and much cheaper than waterjet.An additonal benifit is any spokes,or bearing bores can be programed and cut at the same time and need only slight cleanup for preess fits.

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  • The Artful Bodger
    replied
    Originally posted by jkilroy
    First question is are you sure the application requires steel? Would delrin work? Second, how do you hold them in that lathe to clean up?
    I faced mine using external chuck jaws and trued the edges with the 'wheel' on an arbor.

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  • jkilroy
    replied
    First question is are you sure the application requires steel? Would delrin work? Second, how do you hold them in that lathe to clean up? Half and half? I make 8" sheaves for a stock product of mine often. Its not cheap, but you can buy slices from bar from McMaster-Carr as well, to sizes much larger than 6".

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  • The Artful Bodger
    replied
    I have managed to cut a couple of 'wheels' from plate using my lathe.

    I fix the plate to the backplate on the lathe then drill the centre hole and use a piece of all thread as a 'drawbar' to fix the centre firmly to the backplate, the edges of the plate are already firmly afixed.

    Then I use a trepanning tool to cut the wheel out.

    N.B. It is important to have both the centre 'wheel' and the offcut edge firmly fixed to the backplate to avoid disaster at 'breakthrough'.

    A layer of sacrificial plywood saves my back plate from disfigurement!

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  • oldtiffie
    replied
    Adaption

    Nice solution Mcgyver.

    If I am caught like that I usually just tack-weld it to another bit that can be held in the bandsaw vise. Does not need a lot of tacks at all.

    But on the other hand, if it needs to be cut from plate, I get my supplier to get it done at a local shop that does high pressure water-jet cutting. Its easy to machine and doesn't stress or distort or locally harden the part I want either. Most times non-important water-jet cut faces can be left "as is". My supplier gets it done at a better rate than I can and when he puts his margin on it I get it at a good price as well.

    I made a conscious decision a long time ago to stop buying or hoarding steel plates and sections as the space it takes is a PITA as is pulling that bit I want out from the back of the stack/rack. I carry small quantities of steel sections and bar, and a bit of brass, bronze and aluminium, but otherwise I just go and buy it on an "as required" basis. Most stuff is available locally or if not its only a couple of days away by order.

    I've wasted too many hours and too much stock "making do with what's around" and I plan my jobs around what stock my supplier has. He will cut to length for a small nominal charge as well and so the stuff is ready to use "as is" as soon as I get it home.

    But, as you've shown in your band-saw adaption, you just have to improvise or make do sometimes - but its my last resort.

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  • Mcgyver
    replied
    Originally posted by oldtiffie
    I wouldn't do that.

    At some time you are going to have an end left that you will find difficult to fit in your hack/band saw.
    .



    stud into end, bolted to parallel box, c clamped to band saw. Piece of cake

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  • oldtiffie
    replied
    Band-sawing from a round bar

    Originally posted by Abner
    I figured as much, I just get tired of the clean up.
    Pulleys mainly for cable and odd mechanisms so sheaves wouldn't work.
    I should just go buy some 5-6 in shaft for the bigger ones.
    Thanks
    I wouldn't do that.

    At some time you are going to have an end left that you will find difficult to fit in your hack/band saw.

    I just get it cut from round rod/bar by my steel supplier on his very big band-saw. Cost to cut is minimal and I am set to go on the lathe or mill with no hard spots to remove or cutters to be trashed and I don't have the inconvenience or expense of steel round bars sitting around "just in case".

    I drive past my steel supplier 2>4 times a week - about 10Km (~ 6 miles) round trip. He can cut it dead true (for a band-saw) in a matter of minutes.

    Its much easier facing off band-sawn faces and hot rolled than it is facing off a "black" face and a gas-cut edge on a disk cut from HR plate.

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  • mike os
    replied
    Originally posted by rohart
    Liger :

    I'm not too sure we go around cutting slices off 6" bar, either !

    ***** (ffs... a thing that goes meow)

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  • Toolguy
    replied
    Sure we do! Most modern hacksaws have a 12" blade.

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