Machining a smokebox door

[Jon LawesParticipant @jonlawes51698]

I've got to machine the smokebox door for my brit soon and I'm unsure of how to get the correct profile on the outside. Do you turn the critical bits then profile with a file? I really want to get a nice result; it's a real focal point for the locomotive.

Thanks,

Jon.

[Jon LawesParticipant @jonlawes51698]

[JasonBModerator @jasonb]

Have a look for the recent post on machining the curved face of a buffer or Andrew J's posts about his smokebox door.

[Anonymous]

To save the OP the trouble of searching, this is how I profiled my smokebox door:

Of course this is completely OTT. Although I already had the hydraulic copy unit I had to make the bar to enable the unit to be used for facing. I did it this way because the smokebox door has an outer ring nameplate and I wanted to be able to machine accurate matching curves so that the nameplate was a near perfect fit. Also facing with the unit was a new technique, so I was keen to try it out.

If I was doing the same for a loco smokebox door I'd use some angled cuts and smooth off with a file. Just to make things complicated I would assess which angles to use using CAD and create a sheet steel template marked out and filed by handraulic methods.

Andrew

[duncan webster 1Participant @duncanwebster1]

Andrew keeps on showing us his hydraulic copying attachment, but the chances of finding one to fit a small hobby lathe are worse than a snowball's chance in Hades. Myford did in fact make one

**LINK**

We all have a topslde. What we need is some clever chap (not me) to come up with a CNC drive to the topslide so that either the lathe's powered long travel or cross travel can be set going and the topslide drive whizzes round to generate the fancy shape

[Michael GilliganParticipant @michaelgilligan61133]

Posted by duncan webster on 08/10/2018 18:59:24:

[ … ]

We all have a topslde. What we need is some clever chap (not me) to come up with a CNC drive to the topslide so that either the lathe's powered long travel or cross travel can be set going and the topslide drive whizzes round to generate the fancy shape

.

Do we actually need to use CNC ?

Clockmakers use simple templates to drive a 'sans feedscrew' topslide to shape fusees … It's basically the same idea rotated 90°

MichaelG.

[Jon LawesParticipant @jonlawes51698]

I did read the buffer post, I figured it might be something like that, thank you.

Thanks to all for the suggestions, it would appear there isn't a magic bullet but the profile template and machining in steps is a sound one, thank you.

[JasonBModerator @jasonb]

You don't need CNC to follow a template, just stick a DTI against it and follow the needle or just disengage the leadscrew and push a follower against the template by hand while turning the cross slide with the other.

Simpler still make something like the Turnado from eccentric eng.

[Author]

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