Turning new wheels for a Kato 11-104.

The Kato 11-104, along with the similar 11-103, is a popular chassis among the OO9 fraternity being a cheap reliable motor bogie. Many kits have been designed for it, and a fair few others adapted to sit on it, usually steam locos with the mechanism hidden by side skirts (ho hum). I have one fitted to my Rushby's Resins battery loco, but I feel that its let down by the small wheels. So I decided to turn my own.

First job was to measure the stock wheels and make a simple back-of-an-envelope sketch;

The wheels are solid metal with stub axles which fit into insulating muffs with the drive gear moulded on.
I started by making the stub axles from 1mm silver steel. These have pin points on the outer end, and there was much experimenting done before I found a method that gave me results that I was happy with. I ended up using a sharp 'V' tool in my compound slide (set to 30 degrees) and turning away from the chuck (i.e. moving the tool to the right). The machine was set at 4000rpm and only light cuts taken. I also found it best to cut the material a couple of millimetres overlength, turn the pin points, then face to length rather than my usual method of losing a long bar in the chuck spindle and keep drawing it out and cutting the part from the bar as I progressed. This was to stop the bar whipping around inside the headstock spindle and getting bent.
Here's a poor shot of the set-up;

There's only 2mm of material sticking out of the collet.
I made 6 stub axles, so that I could select the best 4 to use.

The wheels themselves were turned from brass. Nickel silver would probably be better but I have brass in stock, and its easier to turn. As I wanted 3 hole discs I started by facing the ends of 2 lengths of 10mm rod, then drilling 3 equally spaced .9mm holes in the ends at a 4mm(ish) PCD (pitch circle diameter) on my SL, set up as a drill press with the bar held in a dividing head.

Then the bar was transferred to the U3. First I turned down the end to 8.7mm dia. by 4mm long;

Then I used a 1.5mm grooving tool to cut a relief groove 2.5mm from the end, to 6.6mm dia.;

Next the profile tool came into play. This cuts a NEM 310 profile, with a flange depth of .8mm. So as I wanted a wheel that was 6.9mm diameter I plunged the tool in until the flange diameter was 8.5mm (.8 x 2 = 1.6mm. So a 6.9mm dia wheel would have a flange that measured 8.5mm.). I touched the tool on the end of the workpiece and moved it along 3.5mm, which put the flange in roughly at the right place at the end of the bar (although I still had to skim the end of the bar to remove a witness mark);

The wheel could then be drilled for the axle, I used a .8mm drill followed by a .9mm. This is so that I could finish to size with a 5 sided broach. I did originally try a .95mm drill when practicing but it cut slightly oversize. Rather than using a Jacobs chuck I held the drills in my collet chuck, which I find to be much more accurate when using small drills.
Once drilled the wheel could be parted off, slightly overlength. I remounted the wheels in a stepped chuck (from Fohrmann) and faced them to length. I wanted a groove in the face of the wheels, so used a tool that I originally ground when turning a Swedish spark arrestor chimney to cut a shallow groove. Again the wheels were held in the stepped chuck;

Here's a shot of the wheels and stepped chuck, the upper pair have been grooved;

To get this far I've had to use 5 different turning tools;

From left to right; turning and facing, grooving, wheel profile, parting off, face grooving. Its when doing jobs like this that you find a quick change toolpost invaluable. Spindle speeds used were 1500rpm for drilling turning and facing and 150rpm for grooving, profiling and parting off.
Here's a closer look at the wheel profile tool along with the holder that I milled for it;

Once I had carefully broached out the axle holes so that the stub axles are a light press fit I pressed the stub axles in place using the lathe. To ensure that the axles only went in as far as neccessary I turned a spacer to act as a stop, this sat behind the wheel as the stub axle was pressed into place from the inner face.
Here's a photo comparing the original Kato wheels to my new brass turnings;

The spacer can be seen at the bottom of the photo.
And here's a spare Kato chassis with one set of my wheels and one set of Kato wheels fitted;

The 3 holes and the groove can hardly be seen. I blackened the wheels with two applications of Birchwood Casey Brass Black then left them overnight. In the morning they were thoroughly cleaned with lighter fluid and cotton buds and re-fitted to the gear muffs;

And finally the wheels fitted into the loco;

Was it worth it? Well, yes. Despite the new wheels having a chunkier look the difference is hardly noticable to be honest unless it was pointed out but that wasn't really the point. I have successfully turned my own wheels (although one wheel has a slight wobble, probably due to a wonky pin-point on the stub axle) which opens the way for all sorts of possibilities and means that I don't have to rely on commercial products (as long as I don't mind using plain discs and am not bothered by spokes).

And finally, my apologies for the less than perfect photos, I find lathes and shiny brass to be a pig to photograph. Don't forget that you can click on any pic. for a larger image.

Paul.

Update April '19. Instead of turning new stub axles its far easier to press the ones out of the stock wheels and re-use them. Quite why I didn't do that in the first place...

Unimat 3 compound slide.

A compound slide, or top slide, is very usefull on a lathe as it allows you to turn tapers. It sits on top of the cross slide, and is standard equipment on most large machines. On the Unimat 3 however it has to be bought seperately.

A view form the other side, note the graduations cast into the base;

On the underside can be seen a machined stub;

Which locates in a hole machined into the cross slide;

Also note the two engraved marks on the cross slide, upper left in the photo above. These line up with the cast graduations on the base of the compound slide;

Its set at 30 degrees in these photos.

This will come in very usefull for turning tapered chimneys and pin-pointing axles.

Paul.

Quick change toolpost for the Unimat 3.

The Unimat 3 comes with a simple toolpost, capable of taking one tool which has to be set to centre height (cutting edge in line with the centre of the chuck spindle) by placing shims under the tool. This is of course fine, but when you need to change the tool you need to take out the shims along with the tool, then set up the next tool with the correct amount of shims under it. This is I find a bit of a faff, although some canny users have various tools with shims superglued underneath them speeding up the process. However, I have worked on full sized industrial lathes and once you've used a quick change toolpost anything else is just hard work.

These toolposts are available for U3s, as original equipment from Emco (which are now pretty scarce) and also as aftermarket accessories. Mine came from Chronos Engineering Supplies via eBay. I believe that these are made in India for Chronos.

It comes with two toolholders and an allen key. Extra toolholders are available, I now have several.
Each toolholder slots into the toolpost from the top, and is locked in place with the cap head screw on the side. The height of the holder can be set by turning the shaped adjuster on the top, underneath which is a spring to hold the adjuster in place once set.

My toolpost had a problem with one of the locking strips, which sat above the body of the post;

This meant that the adjuster sat on the locking strip rather than the body of the post. I removed the locking strip and filed the upper end down;

Its a shame that this wasn't picked up at the factory, but thats the problem with moving manufactoring abroad, you have less control over the quality. But then if you make everything here in the UK no-one would want to buy it as the price would increase.

Here it is fitted onto the cross-slide;

What isn't supplied is an M6 x 55 cap head bolt, which will need to be shortened slightly (a few strokes with a file), and t-nut (not a problem as the one from the original toolpost can be used).

And again, with a boring bar in place;

(The boring bar incidentaly was made by my Grandfather from an old file.)

With the height of the tool being adjusted by simply turning a screw means that setting tools to centre height is far easier,

This should prove to be a usefull accessory, speeding up work quite considerably.

Paul.