GENERAL
Taps & dies
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.
Anthony Pattinson
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 again that the first hole is important, and care taken to ensure the first drilling is straight and correctly placed, will ensure the accuracy of the finished job.
With regard to Taps & Dies, a professional tap set would have three taps of each size, and the first would be heavily tapered, the second slightly tapered and the third would be straight enabling the thread to be tapped to the base of a blind hole.
If you are tapping through an open hole, the first tap would be the only one needed, followed through possibly by the second.
The split taps do also offer a little more flexibility allowing the first cut to be slightly lighter before tightening the tap holder on the next cut.
I am not sure if any tap & die sets come with the drill size chart, but the general rule is that for a standard thread the drill should be 85% of the tap diameter. You can also calculate this by subtracting the pitch of the thread from the diameter, so an M10x1.5 bolt size would require a 8.5mm hole drilled to tap (10-1.5 = 8.5).
CHEVROLET ORLANDO
Underpowered
Q I would like some advice about a problem with my sons 2011 Orlando 1.8 petrol. I advised him as the car had done 75,000 miles to have the timing belt and water pump changed. This he did using a local garage, however on return the car was underpowered and the engine management light came on.
The code displayed that the exhaust camshaft sensor was faulty. However the garage stated that it was the Vanos unit.
I replaced the sensor with a new quality aftermarket unit and also the exhaust camshaft solenoid which controls the Vanos unit. I also replaced the oil and filter, but all this has made no difference.
On returning to the garage that had carried out the original belt replacement I asked them to check the timing was correct and the exhaust camshaft wasn’t a tooth out. They said it was correct and asked an auto electrician to check out the fault and he said it was the exhaust camshaft sensor at fault.
I find this strange as the sensor was replaced. I checked the wiring to the sensor, and all seemed OK with a healthy voltage to the unit.
This all started after the timing belt was changed but the garage insists the timing is correct. Is there any way to check the correct position of both cams without involving a stripdown. The engine seems to be the same unit fitted to Vauxhall Vectra’s.
Dave John
A The instructions on the cambelt replacement include the warning...
Engines with variable valve timing: Mark camshafts, camshaft sprockets, camshaft adjusters and related camshaft drive system components (as applicable) with chalk or paint prior to removal or dismantling to assist alignment on installation. This is because even with the locking plates in place the cam timing can alter if not correctly set.
Knowing the exact code set would help as many of the camshaft codes do refer to correlation as opposed to sensor failure, and if this is the case then I would agree that the problem experienced since the replacement of the timing belt is due to an incorrect setting up of the camshafts when the belt was replaced.
The engine in your sons Orlando is the 2HO/Z18XER engine and this is the Opel engine which was installed in the Astra, Zafira, Vectra and Insignia. The checking of the timing can be done with the front covers stripped off and the insertion of the timing tool EN-6340.
The camshafts position can also be
