Your non-diagnostic vehicle-related problems solved by Steve Rothwell
GENERAL
Q I set out to change my neighbours front coil spring on her V40 the other day only to be defeated by a seized solid lower balljoint pinch bolt which caused the head to completely round off, aided I suspect by the somewhat small diameter of the head (15mm), an alloy hub with a steel bolt causing electrolysis, and possibly being a Volvo (big on safety) a lot of thread lock. The only option now is to drill out the threaded section of the bolt and retap the thread, although I have just thought about the possibility of just putting a longer bolt with a nut in, assuming the hub is nice and flat so the nut will bolt down squarely – I’ll have to check that, be great if I can just do that.
As I don’t own a terribly comprehensive tap & die set, I’m just wondering what to look for when buying. Are split dies better than solid? Taps seem to come in all sorts of variants, fine, medium and course, starter, taper and plug.
Do I need a set that includes all of these, and do all sets advise on the size of drill bit to use as I think you usually need odd size bits. I’ve seen a Sealey one but no idea if this would cover a home mechanic’s needs, so feel free to recommend any others that you think may be better.
Also do you think the titanium-coated HSS drill bits are vastly better than those that aren’t? I think they’re supposed to stay sharper for longer, but I don’t know if this the reality. I’ve seen a Bosch non-titanium and an Erbauer titanium, both 25-piece both ranging up to 13mm. I actually bought the cobalt version of the Erbauer earlier in the year for £29 and the first time I used one of them a chunk broke of the edge so I’m a bit suspicious of the quality of Erbauer.
Pretty sure it’s Chinese stuff. £29 for a 25pc 5% cobalt set is probably too good to be true though.
A Hopefully the fitting will be able to accommodate a nut and a bolt, as this would be a good option and save you quite a bit of work. But if you do need to drill and tap the hole then there are a few steps that will make things easier.
The first step is to ensure that the centre of the old bolt is drilled accurately using a pilot drill, ensuring that this pilot drill goes through the very centre of the old bolt is the recipe for success. Using a centre punch and taking your time over this step will pay dividends.
The quality of the drill is important, but I never ask the drill bit to bite off more than it may be able to chew, and so starting with a 1.5mm pilot drill and moving up slowly to the desired size, will ensure that the drill bit is not overloaded or overheated and will enable an easier drilling. It should also be remembered that the larger the drill the slower the drill speed. This will help to prevent the conditions that would cause chipping of the drill bit. I will also emphasise a
