Author Topic: "SPUR II" standard cutting tools?  (Read 1509 times)

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Offline John Candy

"SPUR II" standard cutting tools?
« on: December 09, 2015, 08:30:44 PM »
Came across this German Ebay seller "Carbide-solutions" offering quite a few lathe tools specially made for model railway wheels and other items in various scales.
One item is listed for profiling G-scale and Spur-II (the German equivalent of G3) wheels.

http://www.ebay.co.uk/itm/1-HSS-Radprofil-Drehmeisel-10x10-LGB-SpurG-Radsatz-piko-roco-cuttihg-lathe-Spur2-/121772625117?hash=item1c5a36ccdd:g:YjEAAOSw4HVWCUzp

Cannot comment on suitability for our purposes but there are other model railway lathe cutting tools from this same German vendor if you click on his "Visit shop" link.

http://www.ebay.co.uk/usr/carbide-solutions

John.
My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

Offline IanT

Re: "SPUR II" standard cutting tools?
« Reply #1 on: December 09, 2015, 09:11:02 PM »
I know some people use profiling (or form) tools to turn their wheels John but I've never really seen the need.

You can use normal HSS tooling to turn and 'profile' wheels in G3 without any trouble. A touch of a fine file will gently round off the top of flanges too - it doesn't take much. Form tools do have their uses but they are also quite prone to chattering and they are not essential to getting a usable wheel shape in Gauge 3 in my view.

Regards,


IanT
Nothing's ever Easy - At least the first time around.

Offline MikeWilliams

Re: "SPUR II" standard cutting tools?
« Reply #2 on: December 09, 2015, 10:38:13 PM »
I have long thought that a form tool would be useful and a professional I know made one from a Slaters tyre.  I have used them in smaller scales more as a gauge than as a cutting tool, but also for the final finish.

But, SpurII are not the same as G3 standards (some say they are better, but let's not go there!) and the flange looks strange to me with a very small root radius and a very tapered flange.  Does anyone know if these really are SpurII standard?

Mike

Offline Andy B

Re: "SPUR II" standard cutting tools?
« Reply #3 on: December 10, 2015, 07:09:43 AM »
.... and the flange looks strange to me with a very small root radius and a very tapered flange.  Does anyone know if these really are SpurII standard?

Note the advert heading says 'LGB Spur II' - i.e. narrow gauge on 45mm track (i.e. G scale, or Spur IIm).
The picture also says 'Spur G'. The "D=3.0" engraved on the tool suggests a 3mm flange depth.
So no, I don't think these are for standard gauge Spur II.

Andy

Offline Traininvain

Re: "SPUR II" standard cutting tools?
« Reply #4 on: December 10, 2015, 12:28:29 PM »
I know Mark Wood of Mark Wood wheels uses/used to use these types of tools to profile his own wheels.

However, feedback I've received from another model engineer says this is bad practice and will weaken the wheel.

Never having done it myself but looking to start, I think I'd prefer to learn Ian Turner's approach.

Could do with an article for the G3 Society Newsletter on wheel turning - any takers?

Ian


Offline IanT

Re: "SPUR II" standard cutting tools?
« Reply #5 on: December 10, 2015, 09:11:25 PM »
I don't think it's bad practice as such Ian, more a matter of personal preference.

Form tools cut over a larger area and therefore need more power (and a more robust machine tool) to cut cleanly. So a small form tool (on a small lathe) may work well enough but as the form tool increases in size (and cutting area) then the potential for chatter increases unless you are using a similarly larger and more rigid lathe. Most people here will probably only have access to "hobby" sized lathes (e.g. 3.5" and under) and unless everything is in good order (no play in headstock or gibs) then a (large) form tool will tend to chatter.

By contrast, a single point tool (e.g. most lathe tooling) imposes far less strain on the lathe and requires less power to make a good finishing cut.

Wheel turning has been covered many times here and elsewhere but is generally fairly simple provided a methodical approach is taken. There are small variations on the methods used - again with some people having their own way of doing things.  My general method is as follows;

a) Normally, I'll 'face' the back of the wheel, holding it in a 4 jaw by the tread where possible. I'll then turn it over and face the boss, with the casting held by the rim of the tread and the wheel pushed back flat against the chuck jaws. The wheels don't need to be exactly centred for these operations but all the wheels should have their bosses turned to the same thickness/depth at this time.

b) Depending on the quality of the casting (and how central the 'boss' is to the rim and newer castings are pretty good these days) I decide how best (where) to centre the wheels, before drilling (and possibly reaming) the axle hole. I do this to all the castings before proceeding any further.

c) I then turn (and thread the end) of a mandrel to match the bore of the wheels. This mandrel is kept in place until all the wheels have been finish turned. All further turning is done with the wheels mounted on this mandrel. You can take the wheels on and off but if you remove the mandrel itself, then it is very unlikely to run true if replaced.

d) I rarely use tipped tools, preferring HSS generally but 'roughing' sand castings is one of the times I do prefer them. I should also note that Mark Woods wheels are lost wax castings so probably do not have an abrasive skin like (the more usual) sand castings do. Once the wheels are 'skinned' I use a HSS tool to 1) cut the rim face to depth 2) cut the flange's top to diameter and 3) rough the tread diameter and flange thickness to just over their final dimensions. This work is done by using the lathe's dials - making sure any backlash is wound out first. Differences of a few thou between wheels in these dimensions will not be a problem in practice.  I've still not used the compound (top) slide at this stage, so the all wheels have 'square' surfaces. I now have a set of part-finished wheels, all 'roughed' to about the same size.

e) The compound is then set over to the required angle to give a 3 degree cone angle and using a thin round-nosed tool I take a finishing cut on the tread. Without moving anything (everything except the compound slide is locked) I then make the same cut on all the wheels - the tool forming a radius between the root of the flange and the tread. A saddle stop is useful but not essential when doing this.

f) Now you could set the compound right over (if your lathe allows) and cut a 10 degree taper on both sides of the flange but as it's only 2 (to 2.3) mm deep, I just use a fine file to 'ease' the flange slightly on the tread side and then put more of an 'angle' on the very top part of the flange (on both sides). Very little metal needs to be removed and it's very quick to do.

This subject has come up in the past and I think I have some photos I took at the time somewhere on file. I'll see if I can dig them out and post them later. Every Model Engineer has their own way to do things, including slightly different ways of turning wheels. So I do think 'preferences' is a better word to use - and this is generally how I do mine.

Regards,

IanT   
   

Nothing's ever Easy - At least the first time around.

Offline IanT

Re: "SPUR II" standard cutting tools?
« Reply #6 on: December 10, 2015, 10:12:11 PM »
Just a few photos to try to illustrate my previous post...

Photos 1 & 2 - Everyone tends to use Slater's wagon wheels these days but at one time these cast wagon wheels were the only choice. They show the very slight taper on the inside of the flange and the way the tread merges with the flange on the other side of the wheel.

Photo 3 - a simple wheel mandrel, turned and threaded in-situ. I think this one was made before I had any collets but I still use the same general approach. I have a small 'faceplate' with a (replaceable) central 'pin' I'd use now. The faceplate has a 'drive' pin in it that engages with the wheel spokes. The faceplate itself is mounted in a collet (or the 3 jaw) and the central 'pin' (which is initially slightly oversized for the axle bore) is turned true in-situ. It's the same idea and gives the same accuracy but uses less of my scrap box each time I need a mandrel...

Photo 4 - Just some wheel castings part way through the turning process described.  You can take them on and off the mandrel at any time as long as the mandrel itself is not disturbed..

Regards,

IanT
Nothing's ever Easy - At least the first time around.