Fixturing conundrum with Hemingway die filer kit

[timdotdParticipant @timdotd]

I’m part-way through the build of a Hemingway die filer kit, and I’m wondering about how to interpret the drawings and fixture the castings in order to machine some radial slots.

If I’m reading these right, the radii are measured from the “extended” dimension that I’ve ringed in red?

Then I’m wondering about the best way to fixture this for milling, because the larger of the two castings is too big to swing on my SC4.

I’ve got a rotary table, but it’s too small to easily clamp the castings down – so I was thinking of mounting the part to my lathe faceplate and bolting the faceplate to the rotary table.

The casting would have to be offset so that the “virtual” centre dimension is aligned with the rotary table centre, then the entire stack would need to be clamped to the mill table and offset so that the cutter would sweep the arc as the rotary table was turned.

Does this sound feasible (or advisable), or is there a more straightforward option I’ve overlooked?

[bernard towersParticipant @bernardtowers37738]

I used the hole that says 1/4 bsf to clock from. You need a centre pin of known dia and a 3/16 pin in what will be 1/4 bsf later and then a little bit of simple maths. if you fit it to a face plate you could mill it in the lathe (tool post miller)

[JasonBModerator @jasonb]

For jobs likethat it is sometimes easier to hot glue a bit of metal onto the casting so that you can mark out where the ctr should be. Then with the rotary table centred below the spindle position the work so your mark is also lined up and clamp in place.

Another option would be to put a bit of 3/8″ silver steel or the shank of a cutter in your collet and when that touches the side of the casting you will have that 3/16″ offset.

[bernard towersParticipant @bernardtowers37738]

[vintagengineerParticipant @vintagengineer]

If it works go with it!

[Nigel Graham 2Participant @nigelgraham2]

Bolting a faceplate to a rotary-table is usually rather awkward and loses headroom.

If a faceplate for a lathe with screwed nose, as on the Myfords, fitting it via a screwed adaptor requires a positive anti-rotation stop, as the rotating milling-cutter is likely to unscrew it.

Instead, you can mount a reasonably thick, flat plate on the rotary table, using countersunk / counter-bored screws where those may be under the workpiece. (With due care about screw-length / T-slot depth, of course.)

The workpiece is then screwed or clamped to that extension plate.

Bernard’s photo shows that although he didn’t use it, he had room below the extension plate to bolt it to the casting via those two larger holes. I’ve done similarly by using screws tapped into the extension; on both a rotary table and on a lathe faceplate on the lathe itself.

 

I have an aluminium-alloy disc that had once hidden all the ‘orrible ‘oles in a bench-drill table, and this now resembles a Swiss cheese with so many holes for various example of such work!

[timdotdParticipant @timdotd]

Thank you, gentlemen – that cleared up my confusion, and the fixturing actually turns out not to be as frightening as I first thought.

The medium term solution is definitely a custom plate – coincidentally, a very good YouTube video on the subject was posted this week…

[bernard towersParticipant @bernardtowers37738]

By the way Tim when its finished it is quite a bit of kit, I have never been able to file as accurately and fast as that can, its pretty good on the sawing too!

[Roderick JenkinsParticipant @roderickjenkins93242]

I’ve just found the pictures of mine:  Looks like Bernard and I have exactly the same rotary table!

Rod

[bernard towersParticipant @bernardtowers37738]

Yes except I dont have that red blob on the handle, must get round to doing that one day!!!

[timdotdParticipant @timdotd]

I have an ever-expanding backlog of clock wheels to cross out, so anything which is going to speed up filing is warmly welcomed..!

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