Steam Mania - A professionals view of the machining of locomotive cylinders in 5" gauge for the 9F 2-10-0

A professionals View

A professionals view of the machining of locomotive cylinders in 5" gauge for the 9F 2-10-0

(With thanks to R.W. on the L.N.E.R.)

Making a start on the cylinder blocks, tools needed v/milling machine vice, fly/cutter, first machine the datum's, backside of block first, just a clean up at this stage, then turn the block with the machined edge against the fixed jaw using the scribing block, manoeuvre the cylinder block into its best position for machining the surface, using shim if necessary under opposite face, then fly/cut. With two surfaces machined, using a slot-drill put a machined path along the edge which breaks into the edge of the bolting face thus giving the third datum, using a d.t.i. clock, datum to within .002". The opposite face can now be machined, just a clean up, next operation to mark out for the two bores transfer to the marking off table using angle plate, 'V' blocks, parallels ,and v/height gauge, with the machined datum's set vernier to .687" plus height of parallels and scribe the line around the cylinder block, reset the vernier by adding 1.875" and scribe, dropping the cylinder block on to its bolting face on the 'V' blocks, reset vernier to 1.687" and mark, reset v/h gauge adding .438"and mark the two centers which are now plotted, working from the datum's split the difference and scribe, then, by turning through 90° copy, boxes are now formed with the lines this routine is mirrored on both bores, the cylinder bores can now be machined out, transfer to the v/milling machine using tenon stops, and angle plate, slips, and clamps, fasten block too angle plate and milling table, using thickness of slip under corners of block, feeler gauges used to check for gaps working to .002" with bolting face hard against angle plate pull down tight on table.

Boring head is attached to the milling machine with tool, pick up the rough cast of the bore and then take cut, watch for high spots while traversing through, after a number of cuts alter position of cutter to pick up with the box marking, breaking into each one and finish 1.875" dead. Set table traverses to zero moving over 1.875" on the length with .438" offset, machine as before on last hole, bores are now finished.

The length of the cylinder block should now be machined with fly/cutter to size.

Clamp the cylinder block bolting face to the back of the fixed vice jaw and by turning the vice through 90° clamp to table, alter vertical head of milling machine to 30° using slot-drill machine path for exhaust fixing port surface.

The cylinder block can now be turned over and machined for the drain cock seating, turning v/milling head to 5°, it is important that both angles point the same way.

The cylinder block is ready for the steam passage ways. First mark out the position of the 1/2" hole, this is 1.000" from the bolting face and on the same center line has the valve bore, turning v/head through to 30° and by using 1/2" slot-drill locate on the center of the steam passage way, following the egg shaped hole indexing down to maximum depth which will be length of cutter and breaking into the steam chest with an 1/2" drill and mirror the operation on the opposite side.

The next part is probably the most difficult job, the steam passageways between the valve and the piston bore, the way in which I figured it out was to extend the length of the 3/16" slot-drill by marking an extension bar and brazing the cutter into it.

By using a sine bar set to 12"~30" on a slip pile, mark out with v/height gauge spitting both bores then working both sides of the center line for the width of the 1/2" slot.

Start by turning the v/head of the milling machine to 12° extended cutter into collect of chuck, it is important that you only need to machine half way between both bores, working this machining into a 1/2" slot repeat the process on the opposite side of the cylinder block.

Turn cylinder block over and alter v/head of the miller to 22°, this angle is the closest one can get to the best position for machining just enough to avoid the side of the bore, [Note that the position of the slot inside the valve bore must be 3/16" from edge, machine out a 1/2" slot and break into the existing passageway there should now a channel between both bores.

This leaves the exhaust port surface, mark out with the aid of datum's, scribe center of 3/8" diameter hole, split the difference to obtain 1" centers by turning the v/head miller to 30°, drill the exhaust-way into the valve chamber and also the fixing tap 4ba x 5/16" depth, the cylinder block is now set-up on faceplate in lathe having angle plate attached with clamps through slots, one modification was made for straps over the top of the cylinder block, counter balance weights were positioned opposite the cylinder block and a start was made for machining the counter bore, knocking the casting about with the aid of a d.t.i., get the bore running true to within .000" to .002" side and face, using boring tool recess-out to a depth of .125" x 1.938", turn the tool post to 20° picking up the edge of the recess and turn chamfer, this operation for left and right hand of the cylinder block machining complete for block.

Replace all datum center lines around cylinder block, this will only help with the setting for back plate, valve liner, and cylinder cover caps, mark out for drain-off positions 7/32" cap side, and 3/16" guide side, respectively drill at an angle of 5° 3/16" x 40 t.p.i. x 5/16" depth, this concludes the cylinder block.

Picking up the rear caps, swing in the center lathe using scribing block, adjust to run as near as possible for rough cast, machine top and face only for truing to bolting face, drill hole using pilot and finish to 15/32" diameter and counter bore to 21/32" diameter x 3/4" in depth for gland flange, turn round, gripping on top diameter, machine remaining waste to a size of 2-9/16" and to a width of 15/32", machine down to spigot of 1.15/16" x 3/32" making sure to being concentric to bore.

True up as before, grip minimum amount of cast, machine top diameter to 2-9/16" turn round, clock up and machine to width of 9/32" and then machine spigot as before, making sure that the caps fit the cylinder block recesses, transfer to marking off table using dividing head, split 11 holes into equal spacing, but two holes must be at 45° to each other to avoid the steam-way, set by using cylinder block datum's. Hollow edge to suit valve liner fit and spot through on to cylinder block and drill and tap 4ba.

Machine from solid bar to diameter of 1.1/4" allowing plenty for lobe shape, machine down to 21/32" x 5/32" lg to suit rear cover [dimension on drawing is wrong] should be 7/16" not 13/32" in the bore, drill and ream 7/16" diameter, mark off using dividing head 3 holes x 7/8" diameter p.c.d. and drill .41" then using gland as a template spot through onto cylinder cover housing and drill and tap 6ba.

Machine from solid using 1" diameter bar and clock with d.t.i. turn down to 3/8" x 1/4" lg, center drill pilot and finish 3/16" ream turn round and face up to length, using dividing head mark off center line with two holes on 3/4" centers to be used as a template for rear valve guide holes 8ba studding.

Turn from 1.1/2" skim top to 1.7/16" diameter machine down to 13/16" diameter x 1/4" lg and step down to 3/8"diameter 5/8" lg, a 'V' groove 1/16" deep is needed to make dummy cap look original, turn round gripping on intermediate diameter and clock, machine spigot to 1.1/16" x 7/16" lg, making sure that we have 3/16" flange diameter, center drill and finish 3/16" ream x 1.5/16" depth, counter bore to 1/2" x 3/16" deep, mark out using dividing head 4 equally spaced holes on 5/8" p.c.d. Transfer to miller using special vice jaw with 'V' groove to hold diameter of v/cover, turning vice to correct angle for machining taper with 5/8" diameter end mill, taper to be 3/16" x 0" to avoid steam-way.

Pieces of 1/8" x 1/4" x 1.7/16" 4 off & 1/8" x 9/32" x 1.7/16" lg square all faces, 4 at a time mark off from back mark 1/8" x 1.1/4" centers.

Turn from 5/8" diameter solid, machine to 7/16" diameter x 3/32" lg drill & ream 3/8" diameter, change to opposite side, machine to size 5/16" lg and chamfer to 45°, and part off.

Start from 1" diameter bar machine down to 13/16" diameter, machine step to 5/8" x 1/4" lg center drill and pilot & finish to 17/32" bore, and part off.

Grip in 4 jaw chuck and true up, turn top to 1.7/8" diameter x 11/16" lg and face up, parting tool 1/8" wide touching side of face, move over 1/8" x width of tool, set at zero and traverse down thickness of ring plus +.005, moving tool over 3/16" x 1/8" for final groove, center drill and finish to 3/8" x 32 t.p.i. opening up to 3/8" diameter x 5/16" deep, turn round and face to 11/16" wide.

[s/cutting running slow revs, English tool angle, setting at zero on index and traversing in .018" run die down afterwards]

Machine from 3/8" diameter face up to length of 5.1/16" lg and screw cut 3/8" x 32 t.p.i. x 3/8" lg, change round and s/cut 3/8" x 32 t.p.i. x 1/2 lg.

Turn from 3/8" x 6.9/16" lg, clock up in 4 jaw chuck and center drill the end, change round and do the same, bring out from chuck using tailstock with rotating center, and hold the job, machine along 2.1/2" x 7/32" diameter reducing down to 3/16" x 1.7/8" lg, leaving 5/8" shoulder and screw cutting the end 3/16" x 40 t.p.i. x 5/16" lg moving along thread 7/32" x 40 t.p.i. x 3/8" lg, turn round and machine along to 1.11/16" x 7/32" diameter making sure that the length between the pistons is 2.3/8" lg and then thread as before, turn to shoulder 3/16" x 1.1/16" lg. Hollow out center to 1/4" diameter leaving 3/32" either end with radius, by supporting one end in rotating center.

Guide handed by taper, making a start by truing up the flange with scribing block, machine the surface of the flange to 1.7/16" diameter then machine up to shoulder 1.1/16" x 7/16" lg and center drill and ream to 3/16" diameter using small boring tool, machine recess to 1/2" x 3/16" in depth, remove to miller making spacing piece between machined flats for guide plates, this will stop the casting from caving in. And clamp, machine top and inside face to 1/4" below datum center, turning vice through to angle of taper machine to 7/16" to 1/4" [important the tapers are handed making sure to avoid steam-way] using end mill, remove to lathe clock up and recess to 3/8" x 5/16" deep for gland. Mark off using gland in housing for 8ba studding.

Material 1/4" diameter x 1/4" lg face and drill .41" and flat for valve guide buckle.

Machine top to 5/8" diameter and face up, bore out to 13/32" diameter and chamfer 45° part off to length 5/16" and chamfer reverse face.

Machine in lathe gripping the diameter then take a skim down the front face first, remove to miller, with scribing block touch both sides of flats and machine taking just enough off to machine up to 1.1/4" lg, back to the lathe, machine to 1.312" x 1.1/4" lg, this should be a very good fit in cylinder block, alter tool post to 20° and bore angle out, turn round and bore out to 1.000" diameter then recess to 1.062" x 5/82" in depth and shape chamfer at bottom of recess. Remove and mark out with holes in line with valve bore on datum center, scribing lines both sides on 11/16" centers drill and counter bore for 6ba bolts using 5/16" slot-drill.

Square up both plates together on v/miller using two datum c/lines, top and side, mark out and drill for 4ba screws and countersink transferring holes to cylinder block tapping to 4ba for retaining the back plate to cylinder, extended flange band saw out and file to shape this concludes the 9F cylinder block in 5"gauge.