The SVS II Deluxe Valve Refacer is most accurate Valve Refacer made today.
.0005 accuracy for standard chuck and .0002 accuracy for high-performance chuck. The Industry's Best.
The Kwik-Way CenterLine Chuck is what makes SVS II Valve Refacer a cut above all rest. Other Valve Refacers use Chucks, referred to as "center less". These use rollers to grip valve stem while Kwik-way Chuck uses two sets of independent balls that grip stem at two very distinct points. The advantage being, if you have a center less chuck and you're trying to grind an in-service valve, if there is any out-of-round on valve stem, that out-of-round is transferred from rollers on center less chuck to valve face. So your face run out will be no better than your stem run-out.
With Kwik-way Chuck, since it uses two sets of balls that capture valve in wear area of stem, will automatically re-centerline valve. What that means is when we grind valve, face will come out true to center line of stem that actually rides in valve guide.
In other words, if there is some wear on stem surface Kwik-Way Chuck is going to compensate for that wear in such a way that resulting ground valve face is perfectly centered when valve is back in engine.
Some valve manufacturers design their valves with a tapered stem. Because of unique way The Kwik-Way Chuck grabs valve stem, taper has no influence on precision of positioning of valve in chuck. Other Valve Refacer Chucks may cause valve to tilt in chuck. Without a way to compensate for valve stem taper, you cannot reface valve with same amount of accuracy as with a Kwik-Way machine.
The Kwik-Way Chuck is air activated. You simply push a button that will release two sets of balls and allow you to insert valve. You will have a range of 4mm to 14.3mm with standard or high perfermance valve chuck.
Another type if chuck used on other machines is a collet chuck. To give you range of 4mm to 14.3mm you would need at least 5 or as many as 9 different collets to cover that range. As you now know, with SVS II, there is no change over required for various stem diameters. And as you change collets there can be problems with repeatability because you can put collet in receiver with dirt or grit between receiver and collet. In that case, you will get inaccuracy. Also, if you have a tapered valve, collet will not compress to same tension at both points so again with a collet chuck and a tapered valve you get inaccuracy.
The same is true with an out-of-round valve. Because collet wants to compress uniformly around circumference of stem. The bottom line is that other chucks grab valve stem using a greater amount of valve surface, which can be a problem if there are any irregularities in that valve.