Work Holding for Facing

Gents,

I have a work-holding question I'm hoping that you can help provide a solution to, please.

The material is a length of truck leaf spring, possibly 5160, roughly 3" x 5" x .330" thick.

Is there a safe way, to either hold this in a 4 jaw chuck or hold it to a face plate for facing on the ML7?

The plan is to face it on one side, then flip it over and face the other side, machining down the thickness to .250".

Yes......there is an "arc" to the work piece as is, being a truck spring, but I will flatten it the best that I can in a 20 ton press before any facing or milling.

I've never faced material this shape nor of this size before......yep, a newbie just learning. The thought of facing this stock in an amongst protruding clamps or chuck jaws is somewhat daunting.

The other question I have, is a sharp HSS tool up to the task of facing 5160? Of course I have no way of knowing exactly what steel this truck spring cut-off is for certainty, only that it is spring steel and maybe it is 5160.

If this cannot be done on a ML7, I do have a Taig mill that I will attempt the same procedure on.

Thanks for your thots.

I suspect you'll be wasting time unless the material is fully annealed. If you remove one side of spring material it is unlikely to stay flat. Better to start with known material than waste time with unknown material.

I'd face something that size on the mill, but I have a large mill. Alternatively I'd use a 4-jaw chuck in the lathe. Depending upon the hardness/temper HSS tooling may, or may not, work.

Andrew

If this not annealed so it's still springy, I don't think your press will flatten it at all; it would be very didgy to hold it in a 4-jaw, and I don't think your Taig mill would touch it. If what you want is a 1/4" bit of steel I think you would best just buy a bit. At the very least you should get the steel cherry-red hot and hold it there for a few minutes and let it cool very slowly to anneal it before trying to machine it. Might make it easier to flaqtten too.

I will attempt annealing it. No time like the present to learn something new, be it success or failure.

Removing most of the arc is simple in a 20 ton press. I re-arc truck springs in it without difficulty. This piece will be no different.

Yes, it may take multiple machining operations on both sides to remove the relieved stresses from machining. Annealing should help with this too.

My first choice would be to machine this on the ML7. How would you go about holding this piece for this purpose?

Removing most of the arc is simple in a 20 ton press

Lucky you. What sort of unit is it? Big? small? etc

Rather depends on what size 4-jaw you have for the myford, I you have one of the slim body 6" ones then no problem to hold in that with two opposite jaws reversed A 5" should also do it but would need all jaws reversed.

If you started with a longer bit you could drill & CSK the ends so it could be bolted to the faceplate then cut off the ends once you have it down to thickness.

Edited By JasonB on 24/04/2022 18:17:17

Thanks Jason.
Drilling and countersinking us an option. Good thot.
I may also tig a piece of square stock to the back of it, machine it, flip, repeat. That would provide something for the 4 jaw to hold onto.

For annealing the lengths that i have, i am going to put them in the woodstove for maybe 3 cycles of evening and night burning. Three good long 12 hour plus heat soaks. Will see if this works or not. Seems forging bladesmiths have done this to spring steel to anneal it, with success, so they claim.

Can you cut it overlength, hole in each end, bolt to faceplate. When you flip it over you'll need a packer underneath as obviously you cant face where the bolts are

Hmm. If there's any stress left in the steel, will it bend the faceplate when you skim the top?

Same idea, but cut a rough pair of flats with an angle grinder to take strap clamps that are bolted down to the faceplate. The plate is blocked up on a piece of wood to allow the cutter to clear the bolt heads.

If there's not enough room on the faceplate for a straight strap angled from the lip to under the bolt-head, then make some Z or C-shaped clamps to fit.

Dave

Yet another problem not mentioned by previous posters here. Topslides are set up to face work slightly concave. If work is faced across the diameter of a faceplate, it may well not end up dead flat.

Might be best to rough out the work in 4jaw as described above, in order to get the bulk of metal removal done quickly then transfer it to mill table, using low profile clamps on the edges, as per Harold Halls.

Edited By DMB on 24/04/2022 22:03:21

A significant amount of work and ingenuity required to obtain a section of steel 5" x 3" x .25".

Robert Butler

Why do you want to use and old truck leaf spring ?

A description of what you want to achieve will allow us to give better advice.

Not an issue really. Factory setting 60 years ago would have been between dead flat and half a thou concave over the width of the faceplate. But after 60 years of wear, who knows?

If its anealed and pressed flat you can hold it with all four chuck jaws reversed. Set it up "diagonally" so two jaws bear on one of the longest sides. The other two jaws bear on the opposite side. This is a common procedure and works well.

Pack the plate up with small packing pieces behind it so it sticks out past the reversed jaws by just more than you want to remove. This is easiest done with chuck laid down flat on the bench. You can remove the packing pieces if you want after final tightening on the lathe. I use light aluminium pieces and leave them in place if they are not loose. Or bent U shaped packing pieces that are trapped in situ.

This pic shows the basic principle of "diagonal" work holding jaw positions for the four jaw chuck.

But I like Duncan's idea to cut your piece of spring longer than required by say two inches, and  drill holes in the ends and bolt straight through to the faceplate . Machine the middle section and cut off the ends afterwards. Elegant in its simplicity and no chance of anything moving.

For interrupted cut on a large piece like yours, use low rpm, like backgear medium pulley.

Edited By Hopper on 25/04/2022 01:44:32

Edited By Hopper on 25/04/2022 02:02:42

Unlikely. The Myford faceplate is pretty stout with reinforcing ribs in the back.

That was my thought too, but then Felis said ' Removing most of the arc is simple in a 20 ton press. I re-arc truck springs in it without difficulty. This piece will be no different.'

Simply squeezing a leaf-spring between two flat anvils wouldn't flatten it permanently because the spring isn't taken beyond the elastic limit. But it could be straightened by bending it backwards over a fulcrum until the elastic limit is exceeded. Trouble is, bending a spring past the elastic limit damages it. Possibly it doesn't matter, for example piano wire can be wound into an effective coil spring without annealling and requenching.

My guess is Felis has access to a heap of scrap truck springs and hopes to use them as a cheap source of metal. I suspect it won't machine even if annealled. He's probably right that it's 5160, which I see on the web is tough stuff. Searching '5160 machineability' brings up discouraging statements like: While not easily welded or machined, 5160 steel can be heat-treated, annealed, and hot worked into shape. Leaded mild-steel (EN1APb) is much easier to machine than most other steels. (US equivalent, 12L14)

Dave

Over a 5" length I doubt the arc is enough to warrant trying to flatten it unless it's a very elliptical spring. face one side to remove the crest then flip it over to remove what is left which will be thicker at the ends

I didn't say that the stock was from an old truck leaf spring.

The pieces are cut-offs, from new, unused truck leaf springs, obtained from my local spring shop.