Using a Time-Sert kitThis is easier than you think
1. Prepare your workThis is where you clamp down whatever you're operating on to a bench, and if you need to, you remove any covers. For a live postie motor I'll pull the clutch cover off cause it will give access to the back side of the upper part of the drain plug so I should be able to pick at any swarf that makes it past the grease and into the motor.
Here's a quick before shot of the hole.
The threads in the hole I'm using for this tutorial aren't too bad, but it's useful to practise on something before trying to do this on a real life engine that you'd have to fully dismantle and buy new cases for if you cock it up.
2. Clean out the old threadsUse the supplied drill bit for this. You can either drill this by hand (hard to do!) or do it VERY slowly with an electric drill.
Coat the drill bit in copious amounts of grease.
Make sure you keep the drill bit perpendicular to the surface that the bolt head will bear onto. If you get this wrong, you'll bugger up the tapping and, quite frankly, you'll end up having to buy the next size up insert kit and you'll feel like a bit of a fool. Keep it straight! A helper is good here; they can tell you if you're getting off line. I tried to teach my pooch to tell me when I was offline but he just went back to gnawing on a bone.
Work the drill slowly in, and if it gets stuck, don't force it with more power, run the drill bit backwards to break any chips out. It can take some time, but just keep working it backwards and forwards, always turning the motor slowly. Don't spit swarf everywhere as it'll flick around outside and into your eyes (unless you have safety glasses on in which case: good man!) and also flick off the end of the drill bit inside the engine, spreading swarf inside your motor.
At the end of it, you should have a nice clean hole. You have may have a small ring of debris around your hole, but hey, nothing some rags can't clean up.
3. Countersink the holeCoat the head of the countersink tool with grease to contain swarf. If you don't, PLEASE wear safety glasses - this tool flicks a lot of metal around.
This tool produces a fair amount of swarf quickly, at least it stays on the outside of the hole.
If your grease is sticky enough, it'll also stay on the end of the countersink bit.
Keeping the countersink bit perpendicular to the surface, work it in and bore until the bit will not let you bore any more.
Clean up the bit and the hole. You now have a clean hole with a countersunk section at the top.
4. Tap the threads for the outer part of the insert into the holeHere's the really fun part. This is not the time to be learning tapping a thread 101, but I'll give you the lowdown on that first.
There are two schools of thought on tapping threads: one is to just go at it as quickly as you can, smoothly, and keep it straight, and the other is to go forwards half a turn, then back a quarter of a turn, all the way through the hole. The first style seems to produce really smooth, nice looking threads. The second style is what most schools will teach students. The first style really needs high-speed steel taps, tapping in soft materials like aluminium, the second style will work on almost anything you can tap.
I work somewhere in the middle. For cutting threads for an insert kit you want slightly coase edges to the threads so it's got some grip. You also don't want all the swarf going into the motor, so you don't want to just do it in one fell swoop. I go in a few turns to really cut some threads, then back it right out, clean out the flutes, relubricate, then cut more threads.
In case you're going "huh?" about the word flutes in this context, they're the cut out bits on the tap that hold the chips as they come away from the metal on the sides of the hole you're tapping.
The cut away pieces of metal in the tap are called flutes. They serve to extract the swarf as you chip material from the sides of the hole.
Thread tapping 101Tapping a thread is pretty easy.
You start by ensuring the tap is square to the surface - that's what your tap guide is for! Use it!
Make sure you've got a suitable lubricant on the tap, both in the flutes (which collect the metal you cut out) and in the cutting teeth (which are what need lubricating).
Put on your tap handle, or use a shifter like I am for added dodginess, and start the tap spinning clockwise (unless you've got some odd left-hand-thread insert, in which case you are probably repairing something British. I pity you.) The tap will spin and slowly bite. As it bites, don't wriggle it, please, you'll cock up the start of the thread and then the bolt won't work. Get a couple of turns on it, so you've at least cut a reasonable couple of start threads.
Note the guide to keep it straight. Yes, I should really use a proper tap handle, but these taps are just bigger than my biggest tap handle, so a shifter will suffice. Again, you just make sure you keep it straight and steady if you do it this way.
Normally you wouldn't let a tap hang in the thread like that, I purposely cut more threads than I normally would at the start so it would stay and I could get a photo. The things I do. Anyway, after a few turns at the start it'll start getting harder to turn. Do NOT proceed to the point where you cannot turn the tap - this is where you snap it off and if you've ever extracted a screw extractor you'll know just how damned hard these tools are. Of course, if you've already bound the tap then you're in trouble... In either the case you've done it right and it'll still turn, or it is bound, you start to back the tap out by turning it counter-clockwise. Again, do not wriggle it, and turn it until it is ENTIRELY disengaged from the thread. It is NOT a drill bit, do NOT just pull it out of the hole, you'll rip out the threads and feel like a fool.
With the tap out, you can see all the material that's collected in the flutes. Clean it out. This again shows why grease is useful.
Relubricate, and repeat. Take it easy - you can go really slowly and do it half a turn forwards, all the way out, clean out the swarf, etc, or you can take a few turns then back it right out. The further you go the more chance you have of getting swarf into the motor and the more chance you have of binding the tap and snapping it. You have been warned.
If you're doing this in a drill press, you're tapping into soft aluminium, you are confident, and your tap is a high-speed steel one, you could go full speed and do it in one fell swoop. But, hey, if you were that confident, you might not be reading this guide, and you certainly wouldn't be doing it on an engine in-situ, so this guide probably isn't for you.
After a while you'll realise you're cutting no new material. This will feel nice, as the tap will never get tight as you turn it. Congratulations, you have tapped a thread.
If you haven't ever tapped a thread before attempting to tap one for a thread insert kit I'd suggest picking up some scrap metal and a cheap set of taps and practising so you know what it feels like.
With the tapping done, clean up that hole and check out the threads.
You now have a hole, which has a countersunk top, and has the outer threads for the insert cut.
5. Install the insertThe Time-Sert kit is VERY specific on this: USE OIL ON THE INSERT TOOL. Seriously, it's not hard, read the instructions, and do it. You're not really cutting metal so you produce no swarf, so use nice oil for this, not grease.
It's also advantageous to use a tap handle for this as you spin the tool around a lot and it's easier to do with a proper tap handle. My M2-M12 tap handle fits the insert tool nicely, just not any of the other tools in the M12 Time-Sert kit.
I'm using my long-handled tap handle here, just cause I can.
Oil up the threads, and screw the insert on. For a Time-Sert kit you'll engage maybe two or three threads on the insert before you can't do it up with your fingers any more. This is normal. A Helicoil would differ to this a fair bit: with those kits you'd put the insert onto the insert tool, and turn it, then turn it backwards to snap off the tang once you're done.
Screw the insert into the hole using the insert tool. After a while the threads will catch on the outside and the insert will stop spinning, and the insert tool will start to spin. This is the bit where the insert tool cuts the last of the threads in the insert and cold-rolls the sides into the threads. The insert will start spinning again into the hole, and then the insert tool will spin inside the insert, blablabla. Keep doing this for a while.
Keep going until the insert completely bites into the taper at the top and is fully seated. At this point, the tip of the insert tool will only be at the bottom of the insert.
Now you keep going with the insert tool, to really work the threads. It will slowly get easier to turn, to the point where it will be very easy to turn.
The threads are nicely expanded to catch into the outer threads, and the inner threads are the right size for the original bolt.
You're done! Install the original bolt back into the sucker to the proper torque, and don't rip this bastard out.
I did a bit of a test though. This particular sump plug is mean to go in at 20-25N.m, 14-18 lb.ft. I did it up to minimum torque, no problems. Maximum torque was no problem. Double maximum torque no problems. Quadruple maximum torque was a problem - I stretched the sump plug. I got it back out, and a new one installed perfectly. Phot of the stretched threads didn't turn out, and the sump plug's already in the rubbish truck which was taken earlier. Sorry!
These are definitely stronger than the threads cut straight into the aluminium. This is supported by a paper I found on this topic (the URL of which escapes me now).
Happy motorcycling!