Tailstock turret

As I'm going to build this i thought I might just as well document it as it may be of interest to others. I decided to start with the body casting as it is the trickiest then the rest must be easy! However, I've hit a snag before I've even started and that is how to hold the casting for machining. If you look at item 2 on the drawing the left hand face needs to be machined and a 2" register bored with a 3/8" tapped hole right through. I can't hold it in a chuck because of the spigot on the rhs is too large to allow the casting to sit in the jaws of the chuck.

I could hold the casting in the chuck and drill and tap 3/8" from the spigot side of the casting and then mount it on a threaded mandrel, then carrying out the various machining in the lathe but I'm concerned as whether a 4" diameter casting hanging on a 3/8" mandrel is pushing my luck a it too far. It can be seen in the top left of the drawing is a suggested method of holding the casting for machining the spigot, but that's not much help for what I'm trying to do. Any advice and suggestions will be most welcome. Phil

step 1- I think I would chuck the item 2 casting in the 4 jaw and face it and do the counterbored recess, on the lathe. step 2- Then clamp it up as the print shows to do the spigot angled machining and facing. step 3-The OD could be turned using a mandrel as you said, taking very light cuts. If the mandrel were mounted on a piece of scrap bar turned to fit the counterbore in step 1 and clamping to its' face the security of the holding would be improved greatly. step 4 - Later I would remove the bar / mandrel / item 2 assy to the mill, clamping the bar in the mill vise, find centre (aligned to angled spigot machining from step 2), and drill and tap the other holes in item 2 through from the unmachined casting back (spigot side).

Jeff, thanks for your input but the problem is with your step 1. Because of the size of the spigot it is impossible to mount the casting in a chuck, unless it is a very large one. Certainly l can't using my 3 or 4 jaw chucks (Myford sizes) l will post a photo later to illustrate the problem, when domestic tasks are finished!

Phil

I hope this photo shows how the spigot is too large to allow the casting to be held in the chuck jaws.

The photo is a posed shot with the tool holder holding the casting against the chuck.

I am currently thinking that when this turret kit was designed and offered for sale very few ME workshops would have had milling machines and large lathes, so there must be a way of doing it using a typical 3 1/2" lathe but at the moment I can't see it, so any help very much appreciated.

Phil

Oh! I see the problem now, thanks for the photo. Very risky as shown. I hate to suggest it, as extreme care would be needed, but the casting could be clamped up to a faceplate with two parallels under the sides, each side of the spigot, to do step 1. Be sure the parallels can't slip out, and do run slow rpm. Clamps would have to be placed carefully on the outer face to allow the counterbore to be machined to full dia.

It may be better to find a friend with a much bigger chuck to do the setup shown in the pic but in deeper jaws and with the jaws still fully in the chuck (if possible, with nearby friends and covid restrictions)

How about a disc of,say,thick MDF with a recess cut out to clear the spigot. Safer than loose parallels.Then the whole thing clamped to the faceplate.

Incidentally,where did you get the casting from?

Get your angleplate out, bolt the casting to the angle plate securely. Set the angle plate on the cross slide at the correct angle. Clock it in with a DTI mounted to the bed over a set distance or angle gauges and set the angleplate up against the faceplate with the gauge between the faces, before clamping down. Use a boring tool in the spindle. Drill and tap the hole with a drill chuck in the spindle. For next operation if you set it up right you'll simply need to turn and clock the angle plate in line with the axis of the lathe. Then drill and tap the hole for the arbour. If I'm looking at it correctly that is??

Just seen a fully built one of these for sale, is it a hemmingway kit?

Jon

Actually, engage brain.... do that in reverse. Mount raw casting on faceplate to bore and drill through the rotating piece first. Use plenty of packing. Once all these operations are done mount the angleplate loosely on the cross slide, put a piece of paper between the machined surface and the angle plate. Then poke a long bolt that you pre made into the casting to secure it to the angleplate. Make sure the angleplate is nipped fixer tight on the teenuts. Rotate the chuck so that the arbour spigot is on centreheight of the lathe. Then fully tighten the bolt through into the casting. The faceplate can now be turned on the cross slide, and clocked into the required angle. Then a simple matter of drilling and tapping for the arbour. Or you could transfer the angle plate to the faceplate, if the spigot is directed facing directly up so when mounted to the faceplate the spigot is in line with the axis of the lathe. An engineers square on the cross slide may help this setup.

Jon

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It’s rather scary looking ... but the solution is offered [top-left corner of the plan]

MichaelG.

The major challenge on the item 2 part is NOT machining the angled spigot. The challenge is the workholding to machine the front counterbored face, in the OP's small lathe. The angled spigot on the casting is very large and right in the way of holding the part. After the front face is done, and other steps, the angled spigot can be machined exactly as the plans show.

An afterhought for the current makers of these castings - a second chucking spigot at right angles to the front face could be added to the casting pattern to enable the casting to be chucked and the front face to be machined first, then the first op chucking spigot could be sawn off and the other ops done. The machining would be MUCH easier in small machines with this change.

Would it be possible to drill and tap the hole for the locking plunger (possibly smaller than finished size) ahead of schedule and use it to secure a packing block?

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Well that’s me told

MichaelG.

Personally I think doing the flat face boring, drilling and tapping of that side that will eventually face the chuck, is a better way of doing it. To give yourself the most surface area for holding, to then drill and tap/bore for the tailstock arbour. It also means that the part is already in position to maintain the centre tapped hole in line with the axis of the lathe. Also the plunger hole can be drilled at the same angle by simply setting over the cross slide.

The top part then can be made, and indexed and drilled for the plunger indent, bolted together then the sockets drilled and reamed for the tooling. Using the fully assembled part mounted in the tailstock and the drill and reamer mounted in the spindle. Perfect alignment is then ensured with the indexed position and the spindle axis.

Plenty of different ways to do it.

Jon

Edited By Jon Cameron on 05/02/2021 10:25:33

Oh wow, what a plethora of suggestions I'm not sure where to begin. I'm going to spend some time with my tablet in the workshop running through these ideas to decide which way forward. I had thought that I could do the problem machining on my vertical mill with a boring head but the set up again is problematic. Initially I liked Frank's idea of a purpose made mdf packing piece but the problem here is any kind of clamp to secure the casting will prevent the machining from taking place.

I also thought that a chucking spigot would be a simple solution but obviously not much help to me with this particular casting, I don't believe that this kit is still made l bought it at a club auction about 30 years ago and all I know about it is what is printed on the drawing ie. designed by Sparey in conjunction with the Model Maker magazine and I believe that that magazine is long since defunct, but maybe someone here has more information on that.

I will be keeping this going as a build thread but please don't expect rapid updates as my workshop time is limited and I never work that quickly at the best of times.

Phil

Edited By Philip Rowe on 05/02/2021 12:19:06

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Ahh ... So presumably the Reeves site is in need of an update : **LINK**

https://www.ajreeves.com/50_042.html

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MichaelG.

One further thought - is using this difficult to hold casting a must? Maybe you would consider machining a disk shaped part having the needed features like the machined casting disk from solid bar stock or plate, then adding a block having the angled spigot's features to the back of the disk. if disk and block were made in mild steel, the block could be bolted on, or welded, or silver soldered. Bolting would likely be easiest, if a square block with 4 small screws were used, into 4 tapped holes in the disk. The block could be located accurately by using a couple of small dowels fitting in reamed holes in disk and block. Very easy, very solid, and much less of a workholding challenge than using the casting. Just food for thought.

Well at long last I've made some progress, I took what some may regard as a not very satisfactory route but it has worked. I held the casting in the three jaw, drilled and tapped 3/8" BSF and machined a flat land for an arbor to mate to.I then turned the casting around and mounted it on the arbor (turned from a chunk of 3/4" bar) very gingerly faced the casting and turned the O/D to size using carbide insert tooling. Because of the initial interrupted cuts, depth of cut was only 10 - 15thou but once the cut was continuous I was taking cuts of around 30thou, the casting was well over size and consequently there was a lot of material to remove. Boring out the recess was just repetitious as I didn't want to push my luck and at 5/16" deep 30thou cuts take quite a while and also very messy, frequent stops to clear away the cast iron dust but it turned out OK in the end. One thing did surprise me was how little effort was required to unscrew the casting off the mandrel, with all the interrupted cuts when initially machining l thought that it would be really jammed on tight but my fears were unfounded.

Will post more when I have progressed further.

Phil

Looks like a good start Philip! Do please keep us posted as you continue.

The next step in machining the static casting. The casting was mounted on an small angle plate on the cross slide for drilling the tapping size for the 7/16"BSF hole but I've just found that I omitted to take a photo of that operation! Next I bolted the casting to a larger angle plate set at 20 degrees to give the required angle for MT2 arbor that whole assembly will eventually be mounted on and spotted the hole ready for drilling prior to boring.

After opening out the hole with drills to about 1/2" the chuck was removed and replaced with my boring head, I used this with a suitably ground tool bit to act as a facing cutter. Because of the interrupted cut across the boss this was quite a delicate operation, but eventually I was happy with the surface finish. I'm afraid that I chickened out of screw cutting a blind hole in the boss and I've decided to secure the arbor to the casting using a high strength loctite, I'm quite confident that this will be satisfactory for the type of usage that I will be putting the tailstock turret to. Putting the boring head to it's more usual function the hole was opened up to the finish size of 5/8". Again i forgot to get a photo of the actual operation and the following is a posed shot taken later.

So the next stage with this turret is machining the rotating casting, a great deal of head scratching and thought was required to enable me to machine this and maintain concentricity where it matters. The raw casting was mounted in the three jaw chuck using the outside jaws and the outer face of the casting was machined to size, the 20 degree tapered section was a minor problem as swinging the top slide round to achieve the angle meant the feed handle was fouling on the cross slide, so I had to remove the handle and replacing it with a convenient piece of scrap to enable me to rotate the feed screw. The part of the casting underneath the jaws that can't be machined at this stage will be removed later as concentricity is not important here as this area is just knurled to provide a finger grip.

The next stage was reasonably easy, the casting was drilled about 10mm dia and then opened out to finished size with a boring bar, there was a lot of spring in the bar so multiple passes at each setting were required before finishing with a 1/2" reamer.

The piece of paper towel has a weak magnet behind it to collect the worst of the iron dust but l won't be sorry when all the machining of the castings is finished it really is messy stuff!

Phil