annular cutter problem

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I was using an 1.5" X 3" annular cutter drilling through half inch mild steel when the cutter shattered and broke into 5 or 6 pieces.  Can anyone give me an idea of how to prevent this?  It was about my tenth hole that I had cut and the previous slug had jammed sideways and not come out easily.  Could this have anything to do with the problem?  I was using a hougen mag drill with a rotabroach cutter.  Thanks in advance.
Reply:Are you using coolant or oil?Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:Are you using coolant or oil?The drill is sitting horizontally so the normal coolant does not work but I am using a slick stick (I think that is the name) to lubricate the cutter at the beginning of the cut.
Reply:I just had a hougen 1" rotalock cutter just explode on its first hole it ever drilled on my hougen hmd 150.  Got a new send right out to me under warranty.  The grease stick works much better than the cutting oils if your doing a lot of out of position work.Lincoln 300 Vantage 2008300 Commander 1999SA250 1999SA200 1968Miller Syncrowave 200XMT350MPA/S-52E/xr-15Xtreme 12vs Millermatic 251 w/30A  Millermatic 251 Dialarc 250 Hypertherm 1250 GEKA & Bantom Ironwokers
Reply:I just had a 1/2 inch bit explode on me second cut.. Wanted to cry. So I'm interested to see what the experts saySIN CITY METAL WORKSvisit my YouTube channel https://www.youtube.com/user/devvon
Reply:OK so first some good drilling solution.  Any quality drilling coolant used on a drill press will do or you can spend for the name brands.  Get yourself a trigger sprayer so that you can shoot it at the rotating cutter regularly , say every three of four seconds.   Make sure your magnet surface is clear of chips.  That means in most cases that you wipe it clear with a rag or your gloved hand.  Magnets will grip on half inch material but if you are drilling 1/4 inch plate it can shift easily.  One trick is to take a scrap piece of half inch flat bar and place it on the underside of the 1/4 inch material once the magnet is energized.    When you start locate your center on the mark then energize the magnet.  Give it a bump to make sure it has grabbed and start the motor.  SLOWLY engage the plate.  You can see the cutter make a track in the plate,  Once engaged use steady pressure.  Don't load up the motor too much but keep a steady stream of chips curling out. of course you already by this time have given the location a couple of shots of coolant.  Keep the feed going unless you are drilling something very thick like over one inch.  Annular cutters do not grab when they clear the bottom but still if you can guess depth let up on the pressure slightly.   Usually cutters fail because the magnet lets go.  I have never seen a cutter fracture without movement of the drill base except when drilling very deep like a one inch hole in 1 and 1/2 inch plate.  In those cases sometimes you have disengage and blow the cut absolutley clean of chips in the bottom before restarting.  Usually dull bits will fracture because people notice that they are not cutting and they respond by adding too much pressure.  If you stop cutting and lift slightly the chips can get under the cutting edges.  When you apply pressure again the cutting edges skate around the groove sliding on the chip.  You then apply more pressure and ...... it breaks.   Take a look at a new cutter and you will see a sharp edges.  If you look at a slightly worn cutter you will notice that the sharp corner is actually a bit shiny since there is a miniature flat spot.  When you can easily see those shiny flat spots it is time to send it out for sharpening.   If you continue to use the cutter you will end up having to replace it when it shatters.   A properly operated mag drill with one 13/16 cutter going through 3/8th and 1/2 inch will last somewhere between 100 and maybe if you are lucky 200 holes.   If you have drilled accurately you will be able to inspect the slug and see that the centerpunch mark on the slug is centered.   Avoid huge centerpunch marks.Last edited by lotechman; 02-19-2012 at 10:13 PM.
Reply:My experience is that oils can't remove enough heat.  You need to use water and soluble oil at 10:1.  Excess feed pressure will shatter cutters, not because of the feed pressure but because you will partially disengage the magnetic base from the material which causes the bit to wedge sideways in the hole and shatter.  Also trying to drill through lapped plates will cause problems.
Reply:My memory is that I was not applying an execisive amount of feed pressure but I will pay better attention to that.  The bit was not hot and the cutter was only on its tenth whole and was still sharp.  That makes sense that the bit could bind in the hole and then shatter.  I will look at the cut to see if there are any signs of that.  My other thought was the possibility that the bit had been fractured in trying to force out the previous slug and then shattered when the bit was started into the next hole.  Thanks for all of the responses so far this gives me something to think about.
Reply:Next to impossible to have fracture from breaking though a hole and the slug itself is pushed out by the spring loaded center piece.  Dollars to doughnuts something shhifted.  My bet is a few pieces of cuttings sitting under the magnet.  I tilt the unit on its side and swipe it clean with a rag before moving it on to the next position.
Reply:i dont use them all the time but the 3 times i have shattered one, once trying to drill a doubled frame truck used excessive force trying to break through the rust between the rails the other two times the magnet came loose deep in a hole because I didnt have room for the whole magnet to stick down. I think you are probably right you fractured it driving out the plug and came it apart on the next hole.Do not argue with an idiot. He will drag you down to his level and beat you with experience.
Reply:keep your magnet base stable.  Every cutter i have ever broken has been because the drill moved and side loaded the cutter. well i take that back i shattered one when i hit a carbon pocket once.  but other than that its been side loading.Vantage 500's LN-25's, VI-400's, cobramatics, Miller migs, synch 350 LX, Powcon inverters, XMT's, 250 Ton Acurrpress 12' brake, 1/4" 10' Atlantic shear,Koikie plasma table W/ esab plasmas. marvel & hyd-mech saws, pirrana & metal muncher punches.
Reply:We had a 1 13/16" cutter shatter the other day. I couldn't of been the magnetic base because we had it in the radial drill.  For the real story though you need a little back ground. We where cutting the holes in 2"x4"x 3/8" wall tubing. He made the first cut ok and went for the second when it shattered causing it to bind in the hole of the first side and then shatter the tang on the #3 morse taper adapter. I'm pretty sure he went down a little fast and caught the weld on the opposite side causing the shatter. It's either that or he cracked it getting the slug out since not all the slugs ejected well with the spring.Millermatic 252XMT 304'sDynasty 280DXHypertherm PowerMax 1250Miller Trailblazer 302 EFIOptima PulserXR feeder and XR Edge gun and more athttp://members.dslextreme.com/users/waynecook/index.htm
Reply:Although you might get away with using an annular cutter in a drill press it is risky because you want something that is very rigid. Drill presses are not rigid like say a milling machine.   An annular cutter is closer to a end mill that is hollow.  If there is any flex or give in the setup the cutter is toast.
Reply:Drill presses come in different sizes and shapes. But I know what you mean and was a little worried because my radial drill below is old and has a little bit of give in the spindle.  But so far that's the only problem we've had. The guy I had doing it is still pretty green and hasn't learned all the little problems with using machinery this big.   Sorry about the image size but I just linked to the one on my web page.Millermatic 252XMT 304'sDynasty 280DXHypertherm PowerMax 1250Miller Trailblazer 302 EFIOptima PulserXR feeder and XR Edge gun and more athttp://members.dslextreme.com/users/waynecook/index.htm
Reply:Now THAT is a DRILL!!!
Reply:Place where I was working had a Carlton that size.  It was all mine for a few years. :')   Drill tubing on something like that barely wakes it up.   I went by this week and the column has shifted on the base.  I have no idea what is inside but whatever is there has failed and it moved about 3/8 of an inch.   Anyone pulled a column on one of these babies??
Reply:Originally Posted by ironmangqNow THAT is a DRILL!!!
Reply:with the annular cutters mounted in the mill i have also shattered them.   Mostly from the part not being properly secured in the fixtureVantage 500's LN-25's, VI-400's, cobramatics, Miller migs, synch 350 LX, Powcon inverters, XMT's, 250 Ton Acurrpress 12' brake, 1/4" 10' Atlantic shear,Koikie plasma table W/ esab plasmas. marvel & hyd-mech saws, pirrana & metal muncher punches.
Reply:Thanks Irish.  I heard second hand the bearing assemblies are several grand. It seems reasonable for a 20 inch diameter bearing.   If anyone chances on annular cutters with carbide tips be very careful.  They are double or triple the price of regular cutters.  They last forever if looked after.
Reply:Mine's not got roller bearings (though I'm sure some do, come to think of it I think the American we had did). Instead when I say rollers I mean like steel casters running on shafts. If there's fell like you say it sounds to me like it might be the same.  If you look in the picture above at the column you can see the bump out near the top of the collar at the bottom of the main column. Actually you can see two of the bump outs one with the lift screw and the other this side of it. That's where the bottom rollers are on my drill. There's similar at the top of the column.Last edited by irish fixit; 02-24-2012 at 08:53 PM.Millermatic 252XMT 304'sDynasty 280DXHypertherm PowerMax 1250Miller Trailblazer 302 EFIOptima PulserXR feeder and XR Edge gun and more athttp://members.dslextreme.com/users/waynecook/index.htm