Sykes Pickavant valve grinding tool

[Nick Lettington]

Good old Ebay...


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[steve anderson]

I prefer a good machinist to cut 3 angle valve seats all at same height , with the contact point at outer edge of valve and narrow so they last longer and seal better ..   stones are a older rougher way ..   STEVE

[Zetomagneto]

I have a set of Neway cutters which are excellent but rather expensive.
Only light hand pressure required to give a good seat, the pilot is dependant on the 
valve guide for accuracy so I obviously renew the guides first unless they are very good.
I am able to do 3 angle seats with these.

[Charles P]

Students of David Vizard and others may opt for 30degree inlet valves with the fully radiused approach with a thin 30 degree seat joint cut onto the radius. Never known if it makes much difference in reality.

Charles

[Bob Culver]

Steel seat cutters were also used but the seat surface has to be broken first or blunts cutters.
Grinding valves old style is very poor practice. It was done to remove pits from both valve and seat; wastefully reduced the block and formed a very undesirable step on the valve. And the valve not obliged to centre exactly. Production and modern recon technique is not to lap at all and often use an interference angle.
With my Seven used for extensive main road running, and operating a Javelin for decades I have done a lot of valve work. For reasons I did not understand at the time, the Javelin burned and sank innumerable valves and cracked heads. For those without the toys but with a lathe I describe my "tools". I use a one arm cutter to narrow valve seats. I have a series of dummy valves comprising mild steel screwed to rods and finished between centres to a very neat fit in the guides. These are used to lap the seats and regularly trued in lathe.
Valves reground in lathe chuck; with care many can be turned. Ideally should use a collet or do between centres as all chucks jaws wobble to some degree.
Esp for inlets seats can be placed high on the seat and valve cleared immediately below seating to give full breathing.
For the same lift 30deg gives more opening; considered beneficial with low lift valves

[A G Wood]

Reading a little between the lines, a cutter is good for softer seats and a stone essential for hardened seats? So presumably the cast iron seven block valve seat can be cleaned up with either?
Yes Nick, that is how I would approach it. But as Ruairidh says, take care, the stones can remove a surprising amount of material in a surprisingly short time.
The Repco branded 'vibro-centric cutter' I am familiar with drove its stone through a coil spring inside its housing to impart a reciprocating action to the stone [this action was adjustable by twisting the end cap] to avoid cutting concentric tracks- does the SP/B & D one do this? Also with the Repco kit, once one had cut the seat, the instruction was to chuck the tool in the valve grinding machine by its pilot [which was a solid pilot] and finely dress the seat stone against the valve refacer wheel, using the same angle setting  on the machine as the valves had been faced to and a final light cut taken. If the kit was in good order [particularly the pilot] you could get pretty good results without any lapping, even 3-angle if you had the inclination.
Edit: forgot to say that for the Repco variant the pilot was locked in the tool and rotated in the guide, iirc their theory was a snug fitting rotating pilot would average out any minor valve guide wear and keep the seat concentric...