My 7mm dabblings
- Thread starter mickoo
- Start date
Emma H
Active Member
Hi Mick,
Slaters will exchange but if you are interested they also sell packing washers to push standard axles out to S7. I have a pack but have not yet used them on the standard axles I have because my recent purchases already had S7 axles included.
JimG
Western Thunderer
One thing I do with turning wheel tyres to make life a bit easier on the lathe is to turn the tread to size with a knife tool and with the topslide set over by 3 degrees. I leave the flange unshaped - basically as a rectangular cross section. Then I go in with the form tool to finish the tyre off and all it is really doing is shaping the flange and maybe just shaving the tread if the previous machining has been slightly over in dimension. I do all the knife tool cutting as a batch then do all the form tool cutting as a batch, with the wheels on a mandrel to give accurate location - just like you're going to make.
Jim.
mickoo
Western Thunderer
Sounds like a good plan, I hear form tools take a bit of a hammering so any reduction in their work load can only be good.One thing I do with turning wheel tyres to make life a bit easier on the lathe is to turn the tread to size with a knife tool and with the topslide set over by 3 degrees. I leave the flange unshaped - basically as a rectangular cross section. Then I go in with the form tool to finish the tyre off and all it is really doing is shaping the flange and maybe just shaving the tread if the previous machining has been slightly over in dimension. I do all the knife tool cutting as a batch then do all the form tool cutting as a batch, with the wheels on a mandrel to give accurate location - just like you're going to make.
Jim.
Not quite sure of the best way to produce the mandrel (thanks for the correct term!) either a small shaft (10mm or so) with a spigot on the end which is smooth where the wheel boss goes and threaded above for a nut, or to have a threaded hole in the middle with a shouldered bolt, whose smooth part is slightly less than the depth of the boss.
Or to have similar but with the mandrel shaft almost matching the wheel dia and either of the above fixings for the wheel. I.E each size of wheel requiring a specific sized mandrel, you could make two dia for each mandrel, just simply reverse in the chuck for the required size.
I have a whole raft of diesel wheels to do and I'm thinking the solid plastic centre is going to help with take the loads from turning and I understand the boss does not need reducing. However, spoked wheels will need some other form of support, especially if you are going to reduce the boss thickness. The other option there is a mandrel with three holes that pass through the spokes and whose fixings clamp the spokes to the mandrel, a small spigot will be required to centre the wheel first mind, but shallow enough to not impede boss reduction.
mickoo
Western Thunderer
Graham, ok ta, apart from the Jubilee tender and bogie wheels which I ordered, all the rest came with kits I bought recently so no control over what axles were in there. I've also got some steel diesel ones where one side is plastic bushed on a smooth shaft and the other side threaded and screwed on, no idea how to convert those to S7, probably some turned washers.
mickoo
Western Thunderer
Sounds interesting, might be worth investigating if they won't part ex the current axles, personally I can't see why they won't as they are all brand new, actually might be worth keeping them in their packs and asking them to change the whole lot at a show or something, perhaps ring before hand and see if that's a more attractive solution rather than just bartering axles.
BrushType4
Western Thunderer
Mick, I have an idea.
Have reread through your posts, I think you're a mile ahead of me.
Have reread through your posts, I think you're a mile ahead of me.
JimG
Western Thunderer
Mick,
The main problem I find is providing enough friction on a mandrel to prevent the wheel slipping when the form tool is applied to it. I find I can get away with fairly simple methods of clamping - e.g. nut and washer on centre of wheel - if I use a knife tool to take off most of the metal then finish off with the form tool. Watch out for using screws or pegs through spokes - I've got a Gibson brass centred driving wheel somewhere with a very bent spoke when the form tool dug in.
I know there was a paper somewhere about reprofiling drivers and, surprise, surprise, it is a Scale7 one.
http://www.scaleseven.org.uk/About_S7/Standards/Resources/reprofiling.pdf
There the method advocated is to clamp the wheel between two plates with pressure applied from the tailstock.
Jim.
The main problem I find is providing enough friction on a mandrel to prevent the wheel slipping when the form tool is applied to it. I find I can get away with fairly simple methods of clamping - e.g. nut and washer on centre of wheel - if I use a knife tool to take off most of the metal then finish off with the form tool. Watch out for using screws or pegs through spokes - I've got a Gibson brass centred driving wheel somewhere with a very bent spoke when the form tool dug in.
I know there was a paper somewhere about reprofiling drivers and, surprise, surprise, it is a Scale7 one.
http://www.scaleseven.org.uk/About_S7/Standards/Resources/reprofiling.pdf
There the method advocated is to clamp the wheel between two plates with pressure applied from the tailstock.
Jim.
Osgood
Western Thunderer
I know there was a paper somewhere about reprofiling drivers and, surprise, surprise, it is a Scale7 one.
http://www.scaleseven.org.uk/About_S7/Standards/Resources/reprofiling.pdf
There the method advocated is to clamp the wheel between two plates with pressure applied from the tailstock.
Jim.
That is a very sensible arrangement, thanks for the link. If for any reason you didn't want to clamp using the tailstock, for spoked wheels the outer plate can be fastened to the driving plate by screws between the spokes (or the holes in discs for disc wheels?.
I'd been wondering how to do this operation on wheel set assemblies without removing them from the axle, and looking at the suggested method all you need is to split the main driving / clamping plate which would sit in between the wheels. Making this much longer would help with alignment and stability of the split clamp plate. It could be made with a bigger dia. centre section to allow clamping in chuck over the inside wheel.
mickoo
Western Thunderer
Maybe not! the image triggered something, how about using an axle (Slaters square ended type) as the centre pin/ spigot, your mandrel will be sized to suit the wheel, in it's centre a 3/16th hole, now you could hold the axle with a grub screw but that might push it a trite off centre so a better option would be a hole right through the mandrel and axle, retained with simply a nut and bolt.Mick, I have an idea.
View attachment 18927
Have reread through your posts, I think you're a mile ahead of me.
That way all the wheel is certain to be centred and will have some torsional force for cutting, it still maybe advisable to apply a tail stock clamp as well, not overly happy with that arrangement as it makes it very difficult to face the wheel, though I presume the tail stock clamp is only used when using the form tool so shouldn't get in the way when facing off the front and back of the rim.
Most of my wheels are diesel wheels whose holes are much too small to accept a screw through into the mandrel so some other form of clamping is required and the tail stock clamp looks like the best way, except, of all the parts I bought, a rotating centre point was not one of them!
mickoo
Western Thunderer
Jim, indeed I have espied that all ready, some useful information and tips there, just need to emulate or adapt to suit my own cack handed ideas LOL.Mick,
The main problem I find is providing enough friction on a mandrel to prevent the wheel slipping when the form tool is applied to it. I find I can get away with fairly simple methods of clamping - e.g. nut and washer on centre of wheel - if I use a knife tool to take off most of the metal then finish off with the form tool. Watch out for using screws or pegs through spokes - I've got a Gibson brass centred driving wheel somewhere with a very bent spoke when the form tool dug in.
I know there was a paper somewhere about reprofiling drivers and, surprise, surprise, it is a Scale7 one.
http://www.scaleseven.org.uk/About_S7/Standards/Resources/reprofiling.pdf
There the method advocated is to clamp the wheel between two plates with pressure applied from the tailstock.
Jim.
JimG
Western Thunderer
I was just thinking that a centre drill hole on a rod in the tailstock and on the outer clamp plate, with a ball bearing caught between them with a spot of lubrication might give a quick and cheap ball bearing centre.
I bet you it could also become a frustrating method as the ball drops into the swarf between the ways in the bed when you release pressure. Jim
alcazar
Guest
You have PM.
mickoo
Western Thunderer
I do
and greatly appreciated.
Pugsley
Western Thunderer
Rightly, or wrongly, that's the precise method I used to reprofile the wheels for the 37, with the Slaters axles used, as Mick suggested, to hold the wheel in the right place.Mick, I have an idea.
View attachment 18927
Have reread through your posts, I think you're a mile ahead of me.
Tim Humphreys ex Mudhen
Western Thunderer
Mick
Just catching up on the thread after a short holiday.
With regard to the doors and possible etching have you thought of getting Colin to profile mill them for you. He would need some plasticard masters but I'm sure he can assist.
On the subject of wheel turning; my class 40 wheels were turned mounted on a Slaters axle held in a collet chuck.
If you're at Sudbury on Sunday we can discuss it then.
Tim
Just catching up on the thread after a short holiday.
With regard to the doors and possible etching have you thought of getting Colin to profile mill them for you. He would need some plasticard masters but I'm sure he can assist.
On the subject of wheel turning; my class 40 wheels were turned mounted on a Slaters axle held in a collet chuck.
If you're at Sudbury on Sunday we can discuss it then.
Tim
mickoo
Western Thunderer
Tim, that is an option but would not allow for the differing thickness needed for the main door stamping and fingers, it's one of those things easier discussed on a beer mat in the pub than on 'tut' inter web LOL
Should be going to Ally Pally with Phil on Sunday sadly, if not I'll be there weather depending (sposed to snow at the weekend), good idea about the chuck, presume mounted in the 3 jaw chuck?, must confess the lathe chuck jaws are not the best for gripping small dia axles LOL, so the chuck idea is a neat solution. My current chuck closes up quite nice but is a JT2 fit so I'd need a parallel to JT2 adaptor, or just go for a parallel shaft collet chuck, mind that'd then not fit the tailstock MT2
Probably end up getting a JT2 collet chuck 'and' parallel to JT2 adaptor
Tim Humphreys ex Mudhen
Western Thunderer
Mick
I've got a collet chuck that mounts onto the same back plate as the 3 and 4 jaw chuck, so unscrew one and screw on another, then use a 3/16 collet
Tim
I've got a collet chuck that mounts onto the same back plate as the 3 and 4 jaw chuck, so unscrew one and screw on another, then use a 3/16 collet
Tim
mickoo
Western Thunderer
Aha, I see, sadly my lathe chuck isn't screw on its bolted onto a flange with three bolts, not as easy to change, mind it's a popular range of lathes so there may be an equivalent type.
Regards