The set-up is quite well described [for a router jig] here: **LINK**

https://www.trend-uk.com/en/US/trend/content/content_detail.php?record_type=Knowledge&id=23356

How exactly you implement it will depend upon your machine.

MichaelG.

.

Edit: If you want to turn an ellipse: https://m.youtube.com/watch?v=TjaBYsAlwGc

Just in time to edit again … This previous thread is worth a look:

https://www.model-engineer.co.uk/forums/postings.asp?th=73387

Edited By Michael Gilligan on 15/07/2018 19:45:44

Edited By Michael Gilligan on 15/07/2018 20:01:33

The only downside to the method Frances describes is that the sides of the resulting ellipse are not perpendicular to the face. Perfect method if you want to make a butterfly valve but not for something like a gland.

Like the cutout in the centre of this spacer, just for the hell of it:

Andrew

.

I think it's fair to say that the underlying geometry of that method is the same as that of the router jig that I referenced.

Wikipedia shows several interesting constructions: **LINK**

https://en.wikipedia.org/wiki/Ellipse

… and I suppose the Steiner method would be the basis of John's CNC approach.

MichaelG.

I have done quite a few small wooden ellipses using the same principal that Michael's link to the trend jig uses, you just need a strip of wood or even the edge of a bit of paper, just mark 1/2 of each axis and then move your rod around and mark the edge of the elipse.

Since I have had CAD I tend to use that to draw a suitable ellipse and then produce a set of co-ordinates, for big things like dining tables I tend to just make a jig of 1/4 of the ellipse from say 6mm MDF then use that to mark out and finally guide a router.

Similar can be done for smaller metal ones just by drawing a second ellipse outside the first that is larger by half the diameter of your cutter, again you only need to work out for 1/4 of the shape and simply adjust the +/-valve . Plunge at each co-ordinate and the finish with a file. Depending on spacing and dia of cutter you can leave yourself more or less filing as you prefer.

None of the posts in this topic seem to be related to 'Ken' so I am wondering if somehow my PC does not see all the post. Neil's reply does refer to an ellipse so what am I missing?

Ian P

Keith, one way to do this would be for someone who has an understanding of the maths involved in plotting an ellipse creating a set of coordinates for you to use with you manual mill. You would use these coordinates to move a cutter around your blank to give about the correct shape for you to file smooth and to size. For instance with a 6mm cutter and the machine set to x=0 y=0 at the centre of the gland the coordinates would start off like this and would leave about 0.5mm to file away all round. It is tedious if there are a lot of points and rougher if there are less points, just a matter of picking a happy balance. These coordinates are for 1° increments so would require 360 for the complete outline. Alternate values would take 180 moves but have a slightly rougher surface etc. These are mm values but could easily be changed to inch units. A DRO would help keep track of movement. If you want either the spreadsheet that produced these numbers or a text file with the numbers on then PM me.

Martin C

X value Y value

0 -14.5

0.31 -14.49

0.63 -14.46

0.94 -14.42

I wanted an oval piece of brass for the butterfly valve of a Stuart Turner S9 steam engine I was rebuilding, I turned a bit of brass rod to the minimum width, then cut it across at 20*, then moved along and another cut to make a 1 mm thick butterfly valve plate, it worked, so it must be right.

Ian S C

Keith, not Ken. Sorry Keith, and I think it may have been cast iron…

Well those sizes seem to fit together quite nicely and will come out of 7/8" (22.2mm) stock

This first picture shows part of my construction drawing, the red line is the outline of the gland made up from two 19mm radius arcs (38mm dia circles) and the ends rounded to 3.6mm radius. You hopefully can just see a dashed green line that almost matches the red outline which is actually a true ellipse so the made up one comes close enough for most things. Click on all pictures and they should come up larger.

I added a boss if you need one and this is what the finished flange will look like

For the Jig a piece of bar  38mm diameter or larger, I have shown 38 as it matched the curve of the side of the gland and is also more or less 1.5" diameter which you may have to hand. Length is not critical but enough to hold so 20mm plus. Face off then mark out and drill and tap two holes 7BA in the positions shown. replace in chuck and skim down the end to 38mm dia and zero the handwheel dial. Screw on the flange and turn one side to the zero setting then reverse it round and do the other side

The flange is just turned 22mm round and the two holes drilled and will take on the shape as you turn it on the jig. Finally file the ends round using filing buttons.

And this is the drawing to work to PDF to download or just use this image

Edited By JasonB on 16/07/2018 19:13:14

Edited By JasonB on 16/07/2018 19:16:13