Making a die filer – how to build the eccentric

[Iain DownsParticipant @iaindowns78295]

I'm planning on making a die filer and wanted some advice on how to manage the eccentric.

I have a Paralux motor with a DC speed control which runs at 150rpm max. I plan to gear that up to a max of 3 or 4 times that which should cover the speed range.

My main target is small things like crossing clock wheels, but I would like to be able to handle slightly heavier work if need be. So one of the requirements I think I have is to be able to adjust the stroke (clock files short stroke, 9 inch bastard a bit longer).

I've looked at various designs (and made some up) and would appreciate any input on which would be the most robust and reliable.

Please be aware the sketches are just to get the idea across. there will need to be a bit more design!

This is one of the simplest. A wheel with a button on which pushes the slotted bur up and down. Several holes in the wheel to allow different strokes.

The next one is the same basic idea but the button runs into a bearing which pushes the containing bar up and down.

I saw that one in a youtube build and wondered if the point was to reduce or spread the wear.

Finally, and this is my own idea.

In this case the axle is offset from the centre of the wheel. I thought that I could mill a flat on the end and remove the wheel and replace in alternate square holes.

I think some of the commercial units (or kits) follow a design like the above, though only with one stroke and the wheel probably permanently mounted on the axle.

Oh – my first thought was to build something a bit like a steam engine eccentric, but that adds a lot of height/length and would be more complex than the ideas above.

I hope this makes a bit of sense and all suggestions and advice welcome!

Iain

[Iain DownsParticipant @iaindowns78295]

[old martParticipant @oldmart]

If the crank pin was running in a radial slot, the stroke could be adjusted

[JasonBModerator @jasonb]

For the couple of scotch yoke options you show I would have the pin run in a hole in a rectangular block and then the block running side to side in the slot. That way you have a better contact area for the pin around it's whole surface not just two points

Edited By JasonB on 05/02/2022 20:30:46

[Martin KyteParticipant @martinkyte99762]

Have a squint at the Hemmingway Kit at

**LINK**

I buit one and it works very well. Designed to fit on a Myford and be driven by the chuck. The table is adjustable for angle and the stroke length can also be adjusted. Essentially the file is attached to a slide whitch is driven by a crank. No bearings are required for the "big end" as that is taken care of by the headstock bearings. Similarly the motor and speed control are built into the lathe, in my case a variable speed drive as I have a Newton Tesla inverter drive on mine. Lathe mounting also takes care of, well mounting actually, and so the unit ends up at the right sort of hight and is rigidly constrained. I have to say, whats not to like. By all means do your own thing but it's a hard act to beat. The only criticism I have is that the file travels in a straight line so rubs on the back stroke. Hard to get a machine to do anything else really. You really should mount your files upside down in a unit like this so they cut on the down stroke and against the table for heavier work.

I have used mine for wheel crossing but like most thing horological everyone thinks there are short cuts but in the end practicing hand methods end up faster in the end.

regards Martin

[DalboyParticipant @dalboy]

The centre one is similar to some of the machines I use to work on one thing some of them had was a bearing on the pin

[John HinkleyParticipant @johnhinkley26699]

Iain,

How about a variation on the bull wheel drive system as used on a shaper, turned through 90 degrees so that the resultant motion is vertical. An added advantage, as I see it, would be a slow cutting stroke in the downward direction and a rapid return on the upstroke.  The filing speed would be adjustable as well as the stroke.

John

Edited to add an afterthought.

Edited By John Hinkley on 05/02/2022 22:39:44

[Iain DownsParticipant @iaindowns78295]

Old Mart. I think I see what you mean about a radial slot, but I'm not sure how I would secure the pin in the slot.

Jason. Many thanks for finding the term for me. 'Scotch Yoke'. Rings better than thingy which goes up and down. In reflection, the option I presented in the middle did have a pin, I just mis-remembered.

Martin. I have looked at that (you don't think I invented all my ideas do you?). Apart from the general desire to start from scratch (though the kit price is more appealing than I would have expected), I have the sort of modern mini-lathe with no slots on the cross-slide and I'm not convinced they could be added safely. As a matter of interest is the stroke adjustable?

John. I'm interested in more about 'bull wheel'. I've managed to find an internet source which explains how a shaper works (I only had the broadest idea before) and will follow that up.

Thanks all. Any other thoughts welcome.

Iain

[Alan Wood 4Participant @alanwood4]

Chris Borge is showing a first pass on his idea for a 3D printed Die Filer to add to his many other 3D printed workshop devices (including a fractal vice). You might need a small investment in filament.

Chris Borge 3D Filer

[Howard LewisParticipant @howardlewis46836]

The mechanism usually used in Shapers to give a slow forward stroke and a rapid return is often known as a Whitworth Quick Return Mechanism.

It relies on a pin on a wheel engagaging with a lever which is pivoted below the wheel, but not on the same vertical centreline, to give the differential speeds of movement..

Howard.

[Iain DownsParticipant @iaindowns78295]

Thanks for the input so far.

I've had a look at the quick return mechanisms and sketched half a dozen options and I think I've come up with the way I want to do it. My drivers have been ease of building, stroke length adjustment and compactness. Some of my sketches made devices which were far too high for comfortable use.

This should give the idea…

So we have a yoke suspended on two slide bearings (the rods). That's driven by an eccentric wheel where the stroke can be set through a pin (not shown in the sketch) on one of a set of threaded holes at different radii (radiuses?) in the eccentric. there's bronze (probably) bearing which connects the pin to the yoke.

round the wheel goes up and do the yellow bar rides. Simples.

Apart from any general advice and suggestions, I would like to ask for advice on material. Basically I would like to make it all out of steel, apart from the bronze bearing that drives the yoke.

My concern is that the rule is no similar metals on bearing surfaces (except cast iron).

The main concern is therefore two sliding bearing bars either side of the yoke and the yellow drive bar (probably all ground sliver steel)..

My view/ hope is that with a decent amount of grease, what is not frankly a huge load or speed and less than industrial usage that that will suffice.

I don't fancy cast iron for any of the bits both because of the relative fragility and the extra challenges of machine a bar to a nice parallel and fine finish. Something silver still provides for little cost (in this case I already have a bunch, so none).

In a pinch I could make the yoke of cast and perhaps put a lid on it to provide rigidity, but I'd rather not.

Please let me know what you think….

Iain

[JasonBModerator @jasonb]

You could do the yoke from steel and fit bronze ( or even Oilite) sleeves either end to run on the guide rods. Then your square block could also be bronze which will run OK against the steel yoke and steel pin.

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