Solving Valve-seat Problems
Page 75
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MO-DAY the use of inserted valve seats is markedly on the increase, both as regards new engines andfor reconditioning work. In the latter connection it is not always an easy matter to cut the orifice for the insert and then accurately to locate and press home the new seating. A special tool has recently been brought out by Lunts, Ltd., Milford Street, Leicester, to combat these difficulties. It is known as the B and T Valve Insert Seat Cutter, and is priced at £2 19s. 6d.
This all-British tool is packed in a wooden box, and includes a cutter, pilot, tool body, press block, six insert rings and an instruction sheet. An angle cutter costs 1.2s. extra, whilst insert ringe are priced at 9s, per dozen and spare pilots at 5s. 9d. each. When ordering, details as to sizes of valves and pilots should be given. The pilot fits inside the valve guide.
A study of the accompanying illustrations shows the general construction of the B and T cutter ; this is how it is operated : first assemble the tool consisting of the body, cutter, pilot, feed screw and clamping ring. The body is held down by one of the cylinder head studs, centring the cutter by the pilot, which must move freely in the valve guide. Next revolve the knurled feed screw until the cutter begins to bite on the old defective seating. To gauge the depth of cut, place an insert ring between the body of the device and the clamping ring. Traverse the last-named until it touches the insert; locate it firmly by tightening the
cheese-headed screw of the ring as shown.
Work then begins, the feed screw being operated by means of a tommybar. When the clamping ring touches the body of the device the hole has been cut sufficiently deep. Next remove the cutter and pilot. Place the
insert ring over the hole, the chamfered edge being lowest. Above the ring is the press block, which is operated by the feed screw. As the feed is lowered the insert is driven home. The ring is of centrifugally cast-iron, ground to fine limits: the seat is located by being a force fit in the aperture cut by the tool.