S Scale Wagon Wheels on Axles

[Tim Watson]

Fascinating chasing run outs. I purchased a Griptru chuck for the Myford recently which is incredibly useful. My little 8mm CZK East German watch makers lathe is very useful for very small bits, but doesn’t have sufficient rigidity to achieve a good finish on slightly bigger items.

Tim

 

[Susie]

Jim,

One thing that has occured to me is that you could replicate the action of a Griptru chuck with your Bison one, if, as I think, it is attached using a backplate. Remove the chuck and then reduce the diameter of the register on the backplate by about 5 or 10 thou, so that the chuck is a loose fit! Then replace the chuck but do the screws up only lightly. Hold a bit of ground bar (such as a short length of silver steel) in the three jaws, and by gently tapping the chuck get the bar to run true; then tighten the screws. This is essentially what a Griptru does, except tht rather then tapping the chuck the movement is controlled by screw activated wedges.

Once set, you should get pretty good repeatability as long as the diameter of the work remains constant.

 

[JimG]

Jim,

One thing that has occured to me is that you could replicate the action of a Griptru chuck with your Bison one, if, as I think, it is attached using a backplate. Remove the chuck and then reduce the diameter of the register on the backplate by about 5 or 10 thou, so that the chuck is a loose fit! Then replace the chuck but do the screws up only lightly. Hold a bit of ground bar (such as a short length of silver steel) in the three jaws, and by gently tapping the chuck get the bar to run true; then tighten the screws. This is essentially what a Griptru does, except tht rather then tapping the chuck the movement is controlled by screw activated wedges.

Once set, you should get pretty good repeatability as long as the diameter of the work remains constant.

No backplate.




Jim.

 

[simond]

I'm sure my Unimat has a chuck just like that.

And I think it was horribly tight when new. Rather over-enthusiastic wave washer IIRC.

 

[JimG]

Fascinating chasing run outs. I purchased a Griptru chuck for the Myford recently which is incredibly useful. My little 8mm CZK East German watch makers lathe is very useful for very small bits, but doesn’t have sufficient rigidity to achieve a good finish on slightly bigger items.

Tim,

I've started pushing the Cowells a bit - getting away from small items of brass. This morning I've been taking a bit of 19mm (3/4") EN1 down to 9mm diameter - all done at 180rpm in back gear with 0.2mm cuts at larger diameters and 0.25mm cuts in the smaller diameters, and the lathe has worked well. Eyeballing the size of the gears on the banjo, I suspect that the feed is in the 0.05mm - 0.06mm range.




The cuts have been producing quite nice swarf...



...and it looks as though the swarf with the more open spiral might be turning blue!!! Time to make the lathe work harder and swap the HSS tool for an insert one.



The finish is quite good and looks better in actuality than the picture portrays.

It will now take about an hour to clean the lathe down.

Jim.

 

[Ian@StEnochs]

Fascinating chasing run outs. I purchased a Griptru chuck for the Myford recently which is incredibly useful. My little 8mm CZK East German watch makers lathe is very useful for very small bits, but doesn’t have sufficient rigidity to achieve a good finish on slightly bigger items.

Tim

When I bought my Super 7 I opted for a Griptru. A bit more costly than a standard 3 jaw but it has more than made up for that over the years. I turn quite a lot of wheels and it is very easy to get the fixtures running true, much easier, and quicker, than a 4 jaw!

Ian.

 

[Susie]

Another very useful addition is a set of soft jaws, particularly for wheel turning, making in effect, a bespoke step chuck.

 

[Brian McKenzie]

Time to make the lathe work harder and swap the HSS tool for an insert one.

Jim,

Your journey through various lathe turning endeavours has been fascinating - as it much mirrors my own - starting like you with a Super Adept at age 14, then with a Unimat SL after I started earning. Lathes have only got bigger since . . . .

Be wary about insert tooling. In most instances, not only will lightly built lathes then work harder, but the resulting finish could be quite disappointing.
Carbide needs to be sharp which regular inserts are not - unless of 'positive rake' where the cutting edges have been subsequently ground following manufacture. You will know to avoid negative rake inserts, which are blunt instruments intended to make use of brute power and machine rigidity to force heavy chip removal. These inserts, including positive rake type, get supplied with slightly rounded edges, a left over from the moulding process of their production. This slight bluntness is used to advantage, to avoid crumbling of the cutting edge when worked hard - but this is not at all helpful for light cuts on small machines.

Sumitomo produces a range of inserts that modellers have used successfully, but an even better alternative is to prepare your own carbide tooling - or adapt from the now considered to be old-fashioned brazed tools.

The key to obtaining pristine finishes lies in the sharpening of whatever tool material is selected. In the case of carbide, I silver-solder old broken inserts to short steel bars - or use cheap Chinese made brazed tools if in a hurry. Don't bother trying to use a green grit wheel to sharpen these in the same manner as you would for a HSS tool bit, it's too slow going. A diamond wheel fairly gobbles carbide, and a fine grit wheel can provide an edge sharp enough to shave the hairs off your arm.

I make use of a lot of stainless steel offcuts for wheel tyres, and don't care much if some happens to be tough 316 grade. Crisp tools, sharpened to the appropriate cutting angles, peels stainless away effortlessly.

 

[JimG]

Since the stainless steel rod arrived I've been messing around making new axles.

I continued work with the holder for the axle material. I had one false start...



For the first attempt, I machined the mild steel body the approximate length of the axles - 30mm - then drilled through this to 1.9mm diameter to open it out to the 2mm diameter with a reamer. I've often read of drills wandering when boring, but it's the first time it has happened to me. I had started this hole off with a 1.5mm drill and I suspect that this might have caused the problem.

So he new holder body, which I started in my previous message, would have short length brass inserts at each end to avoid wandering drills.



What is going to be the rear end was bored to accept the brass end plug, so no wandering now.



The holder was then reversed and set up in the four jaw to run true referencing the rear end just turned...



...and the front end was bored to take the front plug. The outside of the front was skimmed to make it true as well.

Two brass plugs were turned up to be push fits in the holder body.



Here you can just about see the front plug which has been push fitted into the steel body - that needed my 4" Record vice in the outside workshop to do that - the small vice in my indoor workshop wouldn't look at it.

The brass plug for the rear has been drilled 2mm for the axle end and a small BA screw has been fitted to allow for an adjustable back stop. It hasn't been fitted to the body until the work on the front plug has been finished.



The hole in the front plug was started with a 1.5mm end mill to minimise any chance of wandering. It was then opened out to 1.9mm and a 2mm hand reamer was entered from the rear and the hole finished using the taper on the reamer to provide a tight-ish fit for the axle material.



The finished axle holder with a bit of the stainless steel material in place. An 8BA clamp crew has been added to lock the material during turning.



The rear plug has been press-fitted into the back of the body.



The axle material - 2mm stainless steel rod from Amazon. It's actually 1.98mm diameter, sold to use as axles on small electric cars, so probably running clearance in a 2mm bearing. It was sawn into ~31mm lengths to turn down to the 30mm axle length.



The tool in action, in this case cutting the 1mm diameter journal after the axle had been turned down to 30mm length.

I am aware that the setup will inherently have some run-out - i.e. the clamping screw will tend to hold the axle off centre with the small amount of clearance around the axle which will occur with use. But it could be limited to about 0.001" TIR.



The finished axles, and it was a bit of a fight. The stainless steel was not easy to turn and I had a bit of a fight to get reasonable results from it. In fact it blunted the first tool I used which had been sharpened just before I started on the batch and I used another sharpened tool with a different top rake to see if I got better results.

I made up sets of wheels on axles using this batch of axles and I got about 90% within my 0.003" TIR limit. I've also worked out a dodge to improve out of tolerance wheels. On the assumption that the runout could be both on the axle journal and the wheel axle hole, I turn the wheel on the axle by 90 degrees or 180 degrees and on most occasions the TIR is improved to within limits.

But I've had my fill of wheels on axles at the moment. I've got enough made up sets to use in over twenty wagons so that should be enough for a while.

But I've located a source of plated mild steel rod and I've got some coming from China which should be here at the start of May. So I will probably have another go to see if the mild steel turns better. I'm also looking at cutting the seat for the wheel at 1.9mm diameter on the axle end at the same time as I'm cutting the 1mm diameter journal, so they will be concentric, so the only source of runout should be in the bore of the wheel.

Jim.

 

[Rob R]

That last bit, turning bearing journal and wheel seat in one setting sounds like a good plan. It also means you can use the material that turns best without worrying about the stock size.

 

[JimG]

That last bit, turning bearing journal and wheel seat in one setting sounds like a good plan. It also means you can use the material that turns best without worrying about the stock size.

That only dawned on me this morning. I was thinking about the Slaters' wheels that are supplied to the Society. They have a reduced diameter wheel seat on the axles and David White sold that to me as giving automatic setting of the B-to-B when the wheels are mounted. What it really does is give wheel seat and bearing end concentricity in manufacture when machined in one operation. I could have kicked myself for not thinking that a long time ago. . Roll on getting the mild steel to try it out. I've definitely gone off stainless.

Jim.

 

[Overseer]

That only dawned on me this morning. I was thinking about the Slaters' wheels that are supplied to the Society. They have a reduced diameter wheel seat on the axles and David White sold that to me as giving automatic setting of the B-to-B when the wheels are mounted. What it really does is give wheel seat and bearing end concentricity in manufacture when machined in one operation. I could have kicked myself for not thinking that a long time ago. . Roll on getting the mild steel to try it out. I've definitely gone off stainless.

Jim.

And the axle material doesn’t need to be round. Older Slaters axles (eg 1980s) were made from drawn rod so had grooves along them and couldn’t be used with inside bearings, or they could but would ream out the bearing, and weren’t necessarily concentric with the tyres.

 

[simond]

Stainless is tedious stuff to machine. 303/4 aren’t too bad but 316 is horrid and particularly expensive in taps. We do a fair bit of it at work, the approach seems to be sufficient cut to avoid rubbing and a relatively low speed with lots of coolant. We use solid carbide taps.

 

[JimG]

Stainless is tedious stuff to machine. 303/4 aren’t too bad but 316 is horrid and particularly expensive in taps. We do a fair bit of it at work, the approach seems to be sufficient cut to avoid rubbing and a relatively low speed with lots of coolant. We use solid carbide taps.

I don't think I've ever tried to work with stainless before but I had memories of reading about problems over the years. It really wants plenty of coolant to prevent heating and work hardening and preferably carbide tooling. HSS will work but can be blunted quickly. So with no coolant and HSS tooling I was probably farting against thunder. And I've no idea what type of stainless it is.

I wonder where our commercial producers get their 2mm diameter mild steel material for 4mm and S scale axles? I found a supplier in the US with very high prices, and a supplier in China with more acceptable prices, but no other source in the UK or Europe after a lot of searching on the Internet.

Jim.

 

[simond]

Jim

Can’t help with any suggestions, all our stuff is a bit bigger from 6 to about 40mm and up to 100 in plastic

I’m back in the office Monday - if I get any hints I’ll shout up

Atb
Simon

 

[simond]

Waiting for a train; a quick google suggests that mild (and stainless) steel is available in metre lengths at 1.0, 1.6, 2.4, and 3.2 dia as TIG welding rods - about £15 per kilo

Eg.

Tig Welding Filler Rods, Tig Welding Wire, Tig Welder Filler Consumables

Tig Welder Filler Rods and Tig Welding Wire for aluminium, stainless and mild steel, high quality tig wire & filler rods, buy online for next day delivery

www.r-techwelding.co.uk

Not sure if/how much the copper coating matters

 

[GrahamMc]

but no other source in the UK or Europe after a lot of searching on the Internet.

Hi Jim, what about using silver steel? No need to harden it, unless you want to, and it seems cheap enough at 69p for 13" from Zoro. Link here. Minimum order is 5 pieces. Delivery is a bit steep at £4.99 but they're trade suppliers and are probably looking for 'proper' orders of over £25 when delivery is free. Plenty of alternatives on eBay.

 

[JimG]

Thanks for all your suggestions, but I received a message from another member pointing me to the following...

2MM DIA EN1APB £/Metre - MK Metals

...which is free-cutting mild steel which is probably the best material for me on the Cowells.

This never turned up on any of my searches.

So I've ordered a couple of metres to see how I get on - a case of the delivery charges being more than twice the material cost.

By the time I've finished all this wheel set making, I'm going to have to build a lot of wagons to use them all up.

Jim.

 

[simond]

Perfect!

(I'm still on the train)

 

[WM183]

Mild steel is so much better behaved than stainless. Steel just turns beautifully with big satisfying spirals of swarf. Stainless just chatters and kills tools.

Edited for spelling