Looks like I've got the joys of restoring a thread on an engine block. It's one of the threads that holds the PAS bracket at the rear edge, and must have been loose in a former life and has lots of wobble in it. It's M8 currently, and I need to drill and tap it to M12 so that I can install a replacement keensert (helicoil-style) thread to get it back to M8. Question is, when I attack this with the drill, and then tap an M12 thread, do I need a hard steel drill and hard steel tap to do it with? Or will it give in fairly easily? I've got a spare engine block I could have a trial effort with, btw.
It's just cast iron - use a decent HSS drill bit, take it slowly and keep it cold with loads of WD40 or whatever. The tap shouldn't have any problems...
I've got an 8mm Helicoil set if you want to use that (less drilling required). Think I've also got a spray can of proper cutting lube somewhere. The tapping of the hole can be tricky, depending on the quality of your tap & die set, but you should be ok if you've got a decent one. If you get stuck, look for proper engineering taps - 3 stage set. You should be ok with 2 of the 3 though.
no need for lubricant as cast iron has a lot of carbon in it which is a natural lubricant, well when im machining it we dont use any lubricant just go steady.
Not sure I'd do this with the block 'in-situ'. maybe a good application of liquid metal and stick the bolt in and see how it goes ?
Soft as sh it. Just drill and tap, but be careful with a hand drill, 1 little wobble and the hole will be huge!
Hoping to get straight in thru the wheel arch with the leccy drill. Then I have today bought a Sealey T-handle tap wrench, with sliding handle: Liquid metal sounds a possibility though - where have I seen this stuff? Recomend any outlets? Is it effectively a case of using it like glue? Once in, the bolt stays in, unwindable, without breaking the 'metal' glue?
looks good, on the heli coil front, I'll only get the V-coil kits. i find them just as strong, more coils & drill bit ,complete kit for the job
Lubricant is mainly to cool the drilling, not really lubricate it as such. Basically if you overheat the drill/metal, you'll "work harden" it and it will become as strong as the drill bit itself (in the critical local few tenths of mm you're trying to drill off), becoming a 3 day long drillathon with about 5-6 blunted drill bits. If the drill bit is sufficiently hard and sharp, it will take about 2 mins!
An M9 would probably be a bit close on the amount of material there - the base of the threads on an M9 would be in the ~8mm region already, so may not cut enough clean thread, especially as the pitch would likely differ. 10 is a possibility, though the hole through the PAS bracket is probably not enough without drilling out.
Got it done - quite easy to drill. Practised on a dummy block and half tapped that. Drilled at half mm increments. Then tapped the actual block in situ. Just tapped it as far as the keensert needed, with a square ended tap to finish: Loctite 641 bearing fit, and keensert insert: Crappy phone pic, but that's the insert in, with the tags removed which are just used for turning it into the new thread: Cheers for the tips all
arggghhh help A thread from the past... I have the exact same problem right now.. Both the power steering bracket mouting holes are knackered. its a 20yr old block and the previous car didnt have power steering so the threads are gone to rust. not sure whether to just tap it m9, m10 or what. Chris Did you drill m12 in the end then put the insert in to get it back to m8x1.25? dont they do and friction/spline inserts to save any tapping? as im not too confident not done if for afew years although I know how. I didnt realise before installing the engine so now its in'situ and my tap handle is long it hits the driveshaft and stuff...will have to get one of those handles you bought looks just the job! Might mess it up so guess drill m10 and tap that to start and if no go, drill m12 and tap that for an insert. I have a spare block to practice on also. I cannot let this stop me from going to nurburgring if all else fails ill weld the damn thing to the block!
Seb, it was easy to do, just the drill, tap, keensert & loctite required. Measure the hole length very carefully and don't overdrill the hole. Drill it for as much distance as the tapered tap nose will require to put a full thread in for the keensert. Use paint on the drill bit once distance established. Keenserts from Trident @ Silverstone, that then dictates the overdrill thread and tap size. Any more Qs, ask.
Try cleaning it up with an 8mm tap first. I've done similar on an engine I bought years ago for my golf. PAS is for girls, btw
I sorted it! just drilled it for new m10 x 1.5 bolts, supposed to drill it to 8.5mm then tap it but because my tap set is poor, i.e no taper had to drill 9mm to get the tap to start. also had to enlargen the PAS bracket holes. now thats sorted and the new engine is running ok ive had oil gushing out from somewhere [:^(] both side of the block by the looks of it, couldn't quite tell..coming off bellhousing and other side of sump so just had the pulleys off and the intermediate shaft oil seal had popped out. oil was all over the place higher up also so changed the camshaft and inter. shaft seals. not sure whether to do the crankshaft seal at the same time its harder to get off and not sure if the seal is the same as the other two. im foobard if the seal behind the gearbox has gone will change oil filter mounting to block gasket if the timing end seals dont do the job... then the worst fix... some wynns oil stop leaks fluid
