I've use my rotary table before for doing simple jobs that have just been to hold something at an angle to machine a flat on it or to cut a radius on something, but for my tiny steam engines I thought it seemed appropriate that I tried to use it for cutting the general shape of the spokes in the flywheels.
my rotary table is tiny compared to most being 100mm diameter and has a 36:1 ratio, so 1 revolution of the had wheel turns the table 10 degrees, which makes it nice and easy to add the angles up. the divisions on the handwheel confused me though as they worked out to be 0.166 degrees, but then I realised its working in angles so each division is 10 minutes which makes it nice and easy to calculate too and the middle of a division allows me to work to a 5' angle (which is accurate enough for my purposes and the angles on the rotary table are in clockwise direction (numbers get bigger at the table goes clockwise. it also has 20' of backlash in
so having a quick scan on the net I came across this about how to cut tapered spokes for a steam engine flywheel, which is a bit complicated for my needs, but pointed me in the right direction
http://rick.sparber.org/FWp.pdf (it was ok for me a couple of weeks ago, but my antivirus software is saying its dodgy now, so you have been warned.
so I decided to draw out how I wanted the flywheel to look, drawn on 5mm squared paper at scale of 10:1, with my following design specs, the flywheel is 24mm o/d, with the outer rim being 1.5mm wide and the hub being 5mm o/d, so I thought it would look ok with 2mm wide spokes and the inner edge of the rim would be 1mm in from the outer edge and the spokes would end up 1mm from the hub. I decided to have a 1.5mm radius between the spoke centres and 1.25mm radius between the outer rim and the edge of the spokes.
if you follow that far, but using pythagoras theorem to calculate the length of the spokes between the radiused ends (4.33mm and 7.94mm) and simple trigonometry to calculate the centre of the radius from from the centre of the spokes (15.827 degrees or 15 degrees and 50 minutes). then from this you can work out all the holes you need to drill and the curved and straight slots you need to mill, so I ended up with the following. with this everything is worked from the centre of the flywheel (or rotary table), with the x and y values being the offset of the milling axis. the angles are all from 0 degrees and as there are 6 spokes, the angles are all based on 60 degree sections. e.g. the first outer hole drilled is 15 degrees 50', the second hole is 60 degress less that amount and the third one is 60 degrees plus the original amount, until you have all 12 holes worked out.
the angles of the curved outer slot are cut in the opposite direction so the edge is done with conventional milling and the backlash of the rotary table into account. the spoke sides are cut in multiples of 60 degree rotations. and I ended up with a piece of paper like this with all the cutting and drilling information on it .
so then its time to do some work
so the rotary table was centred on the milling machine and the flywheel was centred on that by using the shank of a drill in a milling chuck (you can just see it in the photo) and the alignment was checked at 90 degree angles and if its set up right the drill will go into the hole without catching on the sides
and the inner and outer holes were drilled (I offset the inner holes 4.33mm instead of 5.00mm) so they were in the wrong place but didnt realise until I'd drilled them, so they were nearer to the hub than they should have been
I then milled the centre of the holes to make it easier to cut the slots later
and then the curves and straight slots were cut to give the shape of the spokes. you can see what effect the error with holes in the centre of the spokes made
rather than scrap it, I decided to taped the spokes and give them a round section by filing them, show together with the 20mm flywheel for the other steam engine, and the drawing and machining data, the inner slot is done in the opposite direction to the outer slot to do is conventional milling rather than climb milling
hopefully working like this makes a rotary table easier to use with a bit of understanding of what you're trying to acheive
my rotary table is tiny compared to most being 100mm diameter and has a 36:1 ratio, so 1 revolution of the had wheel turns the table 10 degrees, which makes it nice and easy to add the angles up. the divisions on the handwheel confused me though as they worked out to be 0.166 degrees, but then I realised its working in angles so each division is 10 minutes which makes it nice and easy to calculate too and the middle of a division allows me to work to a 5' angle (which is accurate enough for my purposes and the angles on the rotary table are in clockwise direction (numbers get bigger at the table goes clockwise. it also has 20' of backlash in
so having a quick scan on the net I came across this about how to cut tapered spokes for a steam engine flywheel, which is a bit complicated for my needs, but pointed me in the right direction
http://rick.sparber.org/FWp.pdf (it was ok for me a couple of weeks ago, but my antivirus software is saying its dodgy now, so you have been warned.
so I decided to draw out how I wanted the flywheel to look, drawn on 5mm squared paper at scale of 10:1, with my following design specs, the flywheel is 24mm o/d, with the outer rim being 1.5mm wide and the hub being 5mm o/d, so I thought it would look ok with 2mm wide spokes and the inner edge of the rim would be 1mm in from the outer edge and the spokes would end up 1mm from the hub. I decided to have a 1.5mm radius between the spoke centres and 1.25mm radius between the outer rim and the edge of the spokes.
if you follow that far, but using pythagoras theorem to calculate the length of the spokes between the radiused ends (4.33mm and 7.94mm) and simple trigonometry to calculate the centre of the radius from from the centre of the spokes (15.827 degrees or 15 degrees and 50 minutes). then from this you can work out all the holes you need to drill and the curved and straight slots you need to mill, so I ended up with the following. with this everything is worked from the centre of the flywheel (or rotary table), with the x and y values being the offset of the milling axis. the angles are all from 0 degrees and as there are 6 spokes, the angles are all based on 60 degree sections. e.g. the first outer hole drilled is 15 degrees 50', the second hole is 60 degress less that amount and the third one is 60 degrees plus the original amount, until you have all 12 holes worked out.
the angles of the curved outer slot are cut in the opposite direction so the edge is done with conventional milling and the backlash of the rotary table into account. the spoke sides are cut in multiples of 60 degree rotations. and I ended up with a piece of paper like this with all the cutting and drilling information on it .
so then its time to do some work
so the rotary table was centred on the milling machine and the flywheel was centred on that by using the shank of a drill in a milling chuck (you can just see it in the photo) and the alignment was checked at 90 degree angles and if its set up right the drill will go into the hole without catching on the sides
and the inner and outer holes were drilled (I offset the inner holes 4.33mm instead of 5.00mm) so they were in the wrong place but didnt realise until I'd drilled them, so they were nearer to the hub than they should have been
I then milled the centre of the holes to make it easier to cut the slots later
and then the curves and straight slots were cut to give the shape of the spokes. you can see what effect the error with holes in the centre of the spokes made
rather than scrap it, I decided to taped the spokes and give them a round section by filing them, show together with the 20mm flywheel for the other steam engine, and the drawing and machining data, the inner slot is done in the opposite direction to the outer slot to do is conventional milling rather than climb milling
hopefully working like this makes a rotary table easier to use with a bit of understanding of what you're trying to acheive