Need help fixing holes, Magnetic drill?

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[/IMG]I have a hinged part that needs new bushings put it. I has to be welded up and then drilled out to 1" diameter holes. the part has three ears that line up to make a hinge. the ears that attach to the arm are 1/2 inch thick. and the ear on the hub is 1" thick. So I will be drilling through 2" inches of steel. and inserting a new bushing. I was thinking about using a magnetic drill. does anyone know if a 1" annular cutter would make a accurate enough hole to drill them out in one shot. Or will i need to drill a smaller hole such as 15/16 then use a reamer to ream it out to 1" I have about 16 sets of these to weld up on a hub. I have a drawing of what it looks like. anybody give me any advice on this thanks
Reply:An annular cutter will work but depending on the accuracy required I'd drill it 1" with a conventional twist drill or as you stated, undersize and then ream for a better fit.Drilling multiple thicknesses with an annular cutter is slightly harder than with a twist drill in that as you go thru each layer you have to remove the slug. No big deal I realize but an extra step non the less. If you do decide to go with an annular cutter, make sure that you get one designed to cut thru multiple layers. The difference being the cutting edge is sharpened to cut along the periphery of the hole first rather than the inside, that makes sure the slug comes out easier. I ran into this problem alot when drilling double truck frames until a salesman told me the different types of sharpening.....Mike
Reply:If you re-size the image to a max of 600h x 800w pixels....theimage when posted, won't chop off what you've written--that can't be read.Annular cutters produce accurate holes, sized a few thou. over nominal.?does the hole on each flange of the hub, need to be in good alignmentto the hole on the opposite flange ?.........(I'd suspect so)Trying to accurately locate to drill or cut thru both eyes of the welded clevis,then thru the center hub flange is problematic. You'll need to remove the slugsas they cut thru each section. How would you fix the clevis to the hub for stability during drilling?.....and you'llstill-I think, need to have accurate positional method to locate the holes.Suggest you consider, laying out and making the hub flange platesas matched set (can be tacked together)--slug cut or drillingThen using fixturing, either drill each clevis half undersize, weld the assemblieswith snug fit pin thru the clevis eyes, then reamBlackbird
Reply:I was going to weld a piece of flat bar on the outside of the flanges to hold them in line and to keep them from moving I was going to make a template from the holes that are already there so I have something to mark dead center when I go to drill after I have welded them up. And I believe I can use a thick piece of copper to cover the back of the holes to get a good flat plug weld started then pull them off and finish welding the hole up. Now I have never used a mag drill, so I have to rent one, what kind of shank or morse taper, etc. do they come with. I think drilling to like 15/16 then using a reamer would be ideal. what kind of reamer would you guys use to get an accurate alignment and size through 3 plates that equal a depth of 2" . A machinist i talked to said he would drill them close to size then use a mill to plung into the hole to get my 1" finish size. thanks for your guys input.Last edited by fishburn123; 12-07-2011 at 02:01 PM.
Reply:Drill them all out,, install your bushing then make new bushings out of steel for the top and bottom, insert the pin through everything then weld in the bushings.