Paul Deslandes Posted October 13, 2012 Share Posted October 13, 2012 Whilst tapping a 3mm blind hole in a crank pulley I've managed to snap off the tap, slightly under flush with the surface. In spite of going very carefully and not being ham-fisted I think the bottom tap snagged on a hard bit and 'came off in my hand' ☹️. The flutes on the tap are very small and, so far, its resisted any attempt to get hold of it with ground down snipe nose pliers and the like. I can't get the pulley off the (non 7) engine so I need to deal with it in-situ as I have no intention of removing the engine, either now or at any time in the future. It s not going to be easy to shift as its obviously stuck in there, that almost certainly being the reason that it broke off in the first place. Drilling is a non starter as its far too hard, too small and the surrounding metal (cast steel at a guess) too soft. Googling reveals a number of possible way of getting it out but the most promising is a tap remover made by Walton Tools in the US. The smallest size they do happens to be 3mm. Emailing them for details of a UK stockist hasn't yet yielded a result so I may have to phone them. If anyone has one of these tools or other suggestions I'd be very interested. The alternative is to offset the hole and start again but I'd rather do it right than bodge it unless I absolutely have to. Ta Paul Link to comment Share on other sites More sharing options...
AMMO Posted October 13, 2012 Share Posted October 13, 2012 Paul I had a friend who used to modify Arriflex cameras for the film business. When small taps broke off he would get them spark eroded. Spark eroding if done properly will remove the tap without damaging the surrounding metal. Maybe you can Google to see if there is anyone offering this service near you. Link to comment Share on other sites More sharing options...
Paul Deslandes Posted October 13, 2012 Author Share Posted October 13, 2012 Ammo, thanks for the tip. I had assumed that spark erosion couldn't be done in situ and the part had to be taken to the machine, so to speak. I'll certainly give it a go though. I'm also wondering whether its worth trying to grind it out, with care, with a carbide burr on a Dremel. The problem is the small size and not being able to 'get in there'. I'd probably have to helicoil the hole afterwards but that shouldn't be too difficult. I'll keep you posted. Paul Link to comment Share on other sites More sharing options...
kenny. Posted October 13, 2012 Share Posted October 13, 2012 Paul, Try a very slim point...ie a scriber,bit of silver steel ground to a point, an old centre drill etc................and carefully tap it round with a small hammer. Link to comment Share on other sites More sharing options...
kenny. Posted October 13, 2012 Share Posted October 13, 2012 Paul.....I also have access to a spark eroder. However I think that tap will be fairly loose anyway, and will tap around with above method............unless it is full of swarf and broke because it was forced into the bottom of hole...........which I'm sure it wasn't. Link to comment Share on other sites More sharing options...
jonboylaw Posted October 13, 2012 Share Posted October 13, 2012 Or try welding a small bolt to the tap stud and winding it out. Link to comment Share on other sites More sharing options...
Paul Deslandes Posted October 13, 2012 Author Share Posted October 13, 2012 thanks for the suggestions. The problem is it being only M3 so its hard to get onto, plus the end is just below the surface of the parent piece. I don't think I could weld anything to it although I dare say an expert with a TIG might. I'll have another go with the sharp point as Kenny suggested. I'm wondering whether a carbide or even a diamond burr idea might work to grind it out. It was a good quality tap so its going to be pretty hard. I dson't know how durable a diamond burr would be. All the stones might just fall off. It wasn't being forced into the bottom of the hole so I suspect it may have been cracked before and a hard bit of the casting was enough to grab it. Kenny, are spark eroders portable or at least can the business end be +taken to the work piece? I'm going to have a ring around on Monday and see if anyone local has such a beast. The car is drivable so I can take it to the machine. Unfortunately Lancashire's a bit far. Paul Link to comment Share on other sites More sharing options...
kenny. Posted October 13, 2012 Share Posted October 13, 2012 The spark eroder I have use of would not be portable Paul........it's quite a big machine. Keep on trying, you may not even need to tap it around with a hammer if it's not jammed, the point of a thin piece of silver steel getting a bite down one of the flutes should hopefully move it by hand.............although it's awkward at first trying to get the "circular" motion on it without just pushing it into the thread. I don't think I'd have any joy with trying to grind it out in all honesty. Link to comment Share on other sites More sharing options...
kenny. Posted October 13, 2012 Share Posted October 13, 2012 Blow it out with an airline too after soaking it with some release fluid......just in case some crap is hindering the extraction, Link to comment Share on other sites More sharing options...
Gordon C Posted October 13, 2012 Share Posted October 13, 2012 A tap of this size is not something i would normally deal with in my normal day to day work however here in the aviation game we do at times have reason to remove perhaps a sheared tap, drills, sheared bolts etc from engines. Paul a long shot for you and one where you will need a compressor and the use of a Desoutter high speed grinder This is an incredably high speed grinder and uses grinding stones certainly small enough for your tap. Take care and no damage will be done to the threads. Thing is now where to get hold of one and can it be done in-situ ?? Link to comment Share on other sites More sharing options...
kenny. Posted October 13, 2012 Share Posted October 13, 2012 Paul, just had another thought...........if you've got a circa 1mm thick slitting/cut off disc for the angle grinder you could make a neat slot across the top of it.........enough meat on 3mm tap.......OK you'd have a mark either side of the hole on the pully but I bet it would then p1ss out with an electricians screwdriver. Link to comment Share on other sites More sharing options...
Gordon C Posted October 13, 2012 Share Posted October 13, 2012 Crumbs just looked at the price of the Desoutter. Never realised they where so expensive 😳 Edited by - Whoosh on 13 Oct 2012 16:30:59 Link to comment Share on other sites More sharing options...
Paul Deslandes Posted October 13, 2012 Author Share Posted October 13, 2012 well, I've just had a go with tapping it gently round with a point and knocked a lump off it. Which is good in one way but not in another in as much as there's less of it in the hole but also less to get hold of. I think this shows it must have been cracked before and why it broke with so little force applied. Either way its going to be a bugger to get out. The top now about 2mm below the surface so I think cutting a slot, which is a great idea, would dig too deep into the pulley. If I can't find someone reasoanbly local who can spark erode it, I'll see what's available in the way of burrs that will grind it away. I've got a high speed air powered die grinder and a Dremel so there must be something out there that will cut it. Link to comment Share on other sites More sharing options...
kenny. Posted October 13, 2012 Share Posted October 13, 2012 Paul, was it turning a bit when it broke or did it seem siezed. If the former do you have a pair of old but very slender/small dividers which you could get the tip of each point down a couple of the little flutes and twist? Link to comment Share on other sites More sharing options...
Paul Deslandes Posted October 13, 2012 Author Share Posted October 13, 2012 no Kenny, unfortunately not. I've been looking at the link that Woosh kindly sent for Cromwell Tools. They have a huge range of mounted points as well as the incredibly expensive grinder 😳 - I bet its the real business though. The points they list are all Aluminium Oxide with Rubenite, whatever that is, or Silicon Carbide. This is not my field so can someone tell me which if either of these materials would be best to grind out high speed steel or tool steel - not sure which the tap will be made of. I'm also not sure if they are suitable for 'end' use rather than grinding with the face of the cylinder IYSWIM. They have a number of lengths in 2.5 and 3mm. Link to comment Share on other sites More sharing options...
Chewie Posted October 13, 2012 Share Posted October 13, 2012 Forget all that spark erosion process. It takes all day and the average subcon machine shop charges £60/hr. Taps and dies are heat treated to a high hardness and are very brittle as you've discovered. Just take a pin punch and smash the **** out of the broken tap. It will shatter. Extract the shards. Redrill and tap M4 or M5. Edited by - Chewie on 13 Oct 2012 21:00:35 Link to comment Share on other sites More sharing options...
Bricol Posted October 13, 2012 Share Posted October 13, 2012 Forget it - drill and tap another hole elsewhere. It's snapped as it jammed - and pretty much anything you can get to slip down the flutes is smaller than the tap core - so unlikely to have much effect - other than add to the jamming. If you really MUST use the same hole, I'll second the smash the doo-dar out of it to break it up. If it manages the hole, and it really really needs to be M3, drill out and insert it - either with a helicoil type thingie, or make your own. Tap bigger, screw suitable sized screw, maybe pre-drilled and tapped down the centre, lock in with proper threadlock ans saw it off flush. Or fit a new pulley -= probably be quicker and less skin lost . Bri Bri Link to comment Share on other sites More sharing options...
kenny. Posted October 13, 2012 Share Posted October 13, 2012 Forget it - drill and tap another hole elsewhere. Probably 100% sound advice .....problem is for me I was the Toolroom "broken tap getter outer" for 20 years..............and as they always told me "it has to come out", which it always did. Link to comment Share on other sites More sharing options...
tbird Posted October 14, 2012 Share Posted October 14, 2012 Paul is this any help here Tim Link to comment Share on other sites More sharing options...
elie boone Posted October 14, 2012 Share Posted October 14, 2012 If you have 2 or 3 steel nails smal enough to between the tap and hole maybe you could turn it out that way, sue you will need a recoil after. Just a tought Link to comment Share on other sites More sharing options...
Paul Deslandes Posted October 14, 2012 Author Share Posted October 14, 2012 Thanks for the link Tim, that's exactly what I was looking for . I think its well worth a try for the price. I'll give them a call tomorrow. Elie, no I've tried that approach and the gap between the hole and the flutes is too small. I've been chipping away at it and I dare say it would all come out in the end. My only concern is damaging the pulley which I assume is cast and there's not a lot of land around one side of the hole. I'll probably end up by drilling another hole but it will always annoy me that I couldn't get it out and do it properly. Thanks for all the very helpful suggestions. Keep 'em coming. Paul Link to comment Share on other sites More sharing options...
Area Representative skeetsy Posted October 14, 2012 Area Representative Share Posted October 14, 2012 Spark eroders are great fun and can be very handy.... When I was an apprentice I spent two weeks making a very complicated flow metering station for a liquid sodium rig out of a piece of bonded (i.e. very expensive) billet stainless steel. I'd done all the complicated stuff and was just drilling the holes in the flanges when I snapped a centre drill ☹️, normally you would just drill it out from the other side, but because of the shape of the flow metering station I couldn't get a drill onto the other side of the flange and as such I got to use the spark eroder As I recall it was a fairly large machine (a bit like a pillar drill - only much more pyrotechnical 😬) and it saved the day If you can get a portable one I imagine the difficulty would be to keeping the thing in a straight line and only eroding what you want it to erode.... I hope the tap extractor works out for you. All the best Richard Link to comment Share on other sites More sharing options...
Wrightpayne Posted October 14, 2012 Share Posted October 14, 2012 This is the most interesting 'thread' on blatchat currently!! C'mon Paul you can do it !! Ian Link to comment Share on other sites More sharing options...
Paul Deslandes Posted October 16, 2012 Author Share Posted October 16, 2012 Hooray!!!!!!!!!!!!1 The tap remover arrived this afternoon from MSC. The little beauty comes with full instructions and hints on its use. I also blasted the broken tap with freezer spray in the hope that it would cool and shrink a bit, then with some lube. Using a pin vice to grip the remover, after a bit of to-ing and fro-ing, it started to turn and, hey presto, out it came *biggrin*. And no damage to the thread, which is a real bonus. These things are well worth the money, about £15.00 including postage for a 3mm version. Obviously they go up in price as they get larger but they do the job. Thanks to all those who gave tips and advice, especially TBird and Whoosh who found the link to MSC. Paul Edited by - Paul Deslandes on 18 Oct 2012 11:38:27 Link to comment Share on other sites More sharing options...
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