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Engine Building Fundamentals: How To Use A Bore Gauge

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How To Use A Bore Gauge


00:00 - In this module we're going to take a look at a bore gauge, as well as seeing how to correctly use the bore gauge for measuring the piston to bore clearance on our Toyota 2JZ engine block.
00:11 Now the bore gauge that we have here as our example is a metric bore gauge and it's able to measure bore diameters between 50 millimetres and 160 millimetres.
00:22 Now, the dial gauge at the end of the bore gauge is what we're going to be looking at to check and confirm our clearances.
00:29 Again, this is a metric equivalent, a metric product and it's able to measure down to 100th of a millimetre in precision.
00:38 At the other end of the bore gauge we have the area we're actually going to be fitting into the cylinder or whatever we're measuring.
00:47 By unscrewing this little adapter, we can change these adapters on the bore gauge which we can use to effect the diameter that the bore gauge can be used on.
00:58 So in our example here, we're measuring a 86 millimetre bore and I've got the correct adapter for that bore diameter.
01:05 The adapters all use a Teflon button at the end and this means that they're not going to scratch or mark the cylinder walls when we're actually using the bore gauge.
01:17 If we move to the other end, we can see we have a small pin and this is what's actually going to do the measuring.
01:24 When we move the pin in and out, the dial indicator will also move.
01:29 There's two wheels here which will run against the surface of the bore or cylinder wall and this locates and centralises the bore gauge.
01:38 Now as we've already found out the bore gauge is not a direct measurement tool, it's really a comparator.
01:45 So what we need to do is start by zeroing the bore gauge or zeroing the dial gauge.
01:51 So what we've done here is we've taken our micrometer and we've used this to measure the skirt diameter of the factory Toyota 2JZ piston.
02:00 What I'm going to do now is I'm going to grab our bore gauge and I'm going to locate and run the bore gauge between the extremes of our micrometer.
02:11 What we want to do here is just rock the bore gauge through until we find the zero point or the minimum point and we want to adjust the outer ring of the dial gauge until that's reading zero.
02:25 Once we've got the dial gauge reading zero we're ready to actually start making our measurements.
02:31 So, let's go on to the block now and check our clearances.
02:36 Now what we're going to do here is check our clearances and number of locations and we want to check the clearance also in two orientations.
02:46 So what I'm going to do is initially instal the bore gauge into the bore.
02:51 What we want to do is move slightly down from the top of the bore and I'm just going to rock the bore gauge through vertical and what I'm doing is taking note of the minimum reading on the bore gauge.
03:04 Now, in this particular example, we're seeing around about 300ths of a millimetre clearance.
03:10 Now, I've checked in the thrust direction of the piston.
03:15 We'll also want to check perpendicular to this plane.
03:19 This allows us to confirm that the bores are truly round.
03:24 Likewise we will tend to check our bore clearance, piston to bore clearance, at the top, the middle and also at the bottom of the bore.