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Working With Machines - Lathes, Mills, etc.

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murrayec
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On my workbench thread @Galteemore asked about turning buffer housings and smokebox doors- I had thought about a thread on here about using machines for model building and about the machines themselves for anyone looking for info. So here we go;-

First up Galteemore's request, there will be more about machines later as we go.

Smokebox Door;-

There is a few ways to do this, the two main ones are to spin a sheet of metal to form the door that way, or to turn it from a solid bar. Spinning a sheet of metal requires a former to be made out of hardwood first, which has the inside profile of the door, the former is mounted in the lathe chuck with the sheet of metal pressed up against it with the tailstock, its then 'spun' and a burnished tool is applied to the metal to push it into shape!

This discussion will deal with the solid bar option. This option is simpler than spinning but is a more advanced lathe operation than most because of the curves to the door- 2 curves are generally required, a small radius curve at the outside edge with a larger curve across the door, some doors have compound curves. This is done by hand turning which requires additional tools.

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The round bar stock is mounted in the chuck with the minimum amount protruding for the part and a bit of safety from the chuck jaws, if the bar is the same size as the door a four jaw chuck is used and the bar has to be clocked to centre, if the bar diameter is larger than the door a three jaw chuck can be used as the bar will be turned down to size, then the part will be concentric. A four jaw chuck will hold the bar stock far better than the three jaw, very handy because we don't want the tailstock to be used as it will get in the way. Take light cuts and all should be OK.

1. Rough cut. The rough shape is cut to approx size, the cut to the rear of the door should allow for a flange to fit into the smokebox face plate, a parting tool is used to do this cut, just to the depth of the flange initially, allowing for the flange and the final parting cut.

2. Step Cuts to Curves. The front face is step cut to just over size of the final curves on the door to prepare for hand finishing. A flange is also cut on centre to a width n depth for the door handle detail. The centre hole is drilled to size- always use a centre drill to start a hole.

3. Hand Tool Curves. Hand turning is done with a Garver Tool held over a bar tool rest, the rest should be adjustable so that one can angle the tool to form the desired curve. Hand turning takes a bit of practice but once mastered any shape can be created, as long as its round! The other option is to use files to do the curves, ensure there is a handle on all files one uses on the lathe. The door handle flange could be ignored and a washer could be soldered or stuck on when the part is finished.

4. Parting Off. Use grades of emery paper or Scotchbright pads to finish the surface taking care not to loose the edges on the detail and then part off with a parting tool, ensure all slides and the saddle are locked when parting off, and if its a deep cut don't forget to allow for this in the initial setting up. Also don't forget to leave the flange on the back of the door! This is where the tailstock should be used but the centre hole is quite small, an adapter can be used to fit in the hole of the door and apply pressure on the handle flange with a revolving centre in the tailstock.

Using a Garver Tool. Some chaps use a bar mounted in the toolpost as a rest, I have done this it works but I reckon the proper stand is better.

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Play with some aluminium bar stock to practice forming curves

Hole setting out can be done before the part is parted off, a punch mounted in the tool post set on centre height can be employed to do this, the chuck is rotated by hand and the cross slide is used to locate where the centre pops are required. A handy device is a printed paper 360deg scale to fit around the chuck and a pointer mounted to indicate the deg of rotation. Tables are available in booklet form or on line to workout rotation.

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A long Hilti nail close fit in a block of mild steel makes a grand punch, just need to ensure one can get it on centre height.

Garver tools, my paper 360deg strip and indicator. I do have an indexing tool but the paper strip is far quicker to set up and accurate enough for this kind of work.

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No workshop should be without this little booklet- threads, drill sizes, tolerance fit tables, PCD radial hole charts and log tables!

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Next well do the buffer housings.......

Eoin

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Thanks Eoin - just been playing with mine this week to get the hang of it! This is really useful - much appreciated for you taking so much time. We can often get away with UK loco parts in 7mm ( LMS 4F buffers match the SLNC pattern and so on) but some parts are special. Recently I had to add a brass capuchon to an NER chimney to get the Irish look - hopefully I can now turn up whole thing in the lathe..... 

If I ever get the Sligo Tank done, the next scratch build is likely to be a GSWR type so will be lots of interesting bits to turn....

Edited by Galteemore
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  • 3 weeks later...

Lathe Turning Gauge G Wheels for an Alco RS-3

This is a job turning 4 replacement wheels for the loco, it was decided to change the traction tyre wheels for plain ones as the layout is relatively level and the tyres disintegrate over time.

A 41mm dia EN8 mild steel bar was sourced for its relative hardness and ease of machining, the wheels are fixed on a 6mm taper axle with a screw to lock in place. This adds to the complexity having to turn a small taper bore from 4.8mm to 6mm, needing a rather small boring tool which had to be made. Also required to turn the taper was a 'taper gauge' - this is for testing the fit of the taper in the wheels while turning it and to hold the wheel blanks in the chuck as the face truing is being done, again this had to be made first.

Boring tool being ground from a broken 3.75mm dia cnc tungsten carbide bit, using a green stone on the bench grinder to do this, grey stone does not cut carbide very well and generally just falls apart and over heats the tool which is not good- the tool looses it's hardness.

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An existing wheel was removed to use as a pattern, 10mm thick wheel blanks were cut from the 41mm bar on the bandsaw the final thickness of the wheel is 8mm so a bit to play with! the taper gauge/mandrel was turned from 16mm dia EN8 ms bar to replicate an axle end from the loco, it has a M4 bolt and washer to hold the wheels when being used as the mandrill, and the boring tool was setup.

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The wheel blanks were mounted in the 4 jaw chuck and dialled in to run on centre as the blanks were the exact diameter of the wheels including the flange so no waste to spare. The blank was faced off first as this is the back of the wheel and now is the time to do it. A 4mm dia hole was drilled through using a centre drill first 4mm gives just enough space to get the boring tool in. The boring was done by setting the top slide to the taper angle, the saddle and cross slide were locked and the cutting was carried out using the angled top slide only to create the taper. This is where the bore gauge comes in for checking the fit when doing the final cuts.

When setting up a taper gauge to check fit in this kind of job one sets the top slide to the angle, cuts the gauge and then cuts the bore in the item being made- without resetting the top slide or the cutting tool so that the taper angles will be spot on!

I have no photos of that work but this is one of the completed tapers and faced off wheel backface.

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The blanks were then turned around in the 4 jaw chuck and a counter bore was cut for the bolt recess when fitted to the loco and also to be used for holding the blank on the taper mandrill while processing the front of the wheel. The counter bore was done with the little boring bar.

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Now the taper gauge/mandrill is mounter in a collet chuck, this kind of chunk is very handy for round bar as it always tightens up on centre, even if one removes the bar and re chucks it- it will be on centre. This chuck is an ER25 type for the mini lathe and can hold bar from 1mm up to 16mm by changing the appropriate collet in the chuck- the 16mm collet is being used here.

The wheel blank has been mounted on the mandrill with the M4 cap screw, the head of the screw and washer needs to be turned down to fit into the counter bore of the wheel blank, an extra washer is installed for packing to allow the outer washer to be turned down to size.

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After the screw and washer are turned down and re-fitted the full face of the wheel blank can be faced off and brought to the finished size of 8mm thick. A dial gauge is been used here off the saddle to measure the cut so that when the other 3 blanks are set up to be faced they will all end up at the same thickness.

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With all the blanks set to the same size the front of wheel recess detail is part done- the top slide is set to an 8deg angle as the recess is at an 8deg angle, it get deeper out near the tyre. The saddle has a dial gauge set up to watch the depth of the cut and only the top slide is used to traverse the tool.

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Inside done to 1mm deep but then the tool binds.

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The tool is changed to do part of the outside of the recess but cannot be completed yet until the wheel thread is cut to set the distance, so the detail will match the existing loco wheels.

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Outside being done but have to step the tool out near the tyre as it also starts to bind.

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Two dial gauges are used her, one to measure off the saddle for the depth of recess and the other off the top slide to stop at a point adjacent the location of the tyre.

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Recesses part complete which will be completed with a boring bar after the tyres are cut.

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Tyres and flanges are rough cut square first.

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All done square.

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Now the top slide is set over at 20deg to cut the flange faces372976097_RS3-W2120210304_140930.jpg.0fcceed778878b271778b096381ca9ac.jpg.

The tool is set in the post to have a 4deg angle to cut the tyre face when the top slide is wound in to the full flange depth. The saddle and cross slide are locked and only the cross slide is used clocked with a dial gauge to measure the depth and get all the wheels the same.

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Now that the tyres are finished the rim dimension can be set. The final cut being done on the front face using a boring bar tool to finish the outside of the recess.

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Dial gauges again being used to measure the depth of cut and distance out to the edge of the recess.

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Cleaning up the edges with a file.

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Blackening being done with blowtorch and WD40.

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Blackened.

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Complete, the one on the left is an original.

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Fitting and going for a test run........

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Eoin.

 

 

 

 

 

 

 

 

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  • 1 month later...
  • 10 months later...
Posted (edited)

Mini Sandblasting Cabinet Upgrades;-

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This cabinet was made a few years ago. It's made from a perspex medical display box, Woodies gloves, plumbing bits, and an Expo Tools airbrush sandblast gun. The gun, although it gives an excellent fine finish for painting, is a pain to use. The sand container lasts for about 20 seconds and then it has to be filled again- this works fine, but becomes a pain after about 6 goes. Also the cabinet is not tall enough internally and makes the work tight and uncomfortable.

So some upgrades are needed, as I have a bunch of 6 wheelers, a J10 chassis, and more coming along to paint. These models have a few delicate parts so I prefer to use this setup rather than my larger sandblaster which has a more aggressive grit which is prone to bend/warp delicate parts. Also this blaster has a very light cut, so light that paint can be cut back without going all the way through to the metal or plastic, it can also be used for weathering a model.

The work involved;- raising the lid, designing a sand hopper to feed the airbrush, and lights.

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An MDF lid riser was constructed and all the parts needed made from brass and aluminium bar, aluminium sheet and angle, 4mm plastic tube, and a bit of ply wood.

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The airbrush sand hopper lid was modified by drilling and tapping an M4 hole and threading a tube through with lock nut to hold, the bore of the brass tube is 2.5mm dia. On the right in the photo is the sand outlet for the new hopper turned up in brass with a brass knurled nut.

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These are the bits to hold the new hopper.

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The new hopper is made from a Lidl hand-wash container.

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Floor underlay foam was used to make a seal for the lid.

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New hopper mounted.

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This shows how the lid of the hand-wash bottle is modified to take the brass outlet.

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Ready for testing.

Well things did not go well- the sand would not flow easily in the 4mm tube, and when the sand was used up in the tube the air would squirt up the tube and fire sand all over the place! So I decided two mods would be tried- a sealed hopper with a small air hole only and a larger diameter tube- 6mm.

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6mm diameter silicone tube was acquired and a few new brass fittings were turned up- a 6mm bore hopper out let (that's the old one on the right) and a brass fitting to connect the tube to the top of the airbrush.

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The new fitting screws onto the brass M4 threaded tube on the lid and locks onto the nut.

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New sealed hopper bottle and LED strip lights (Lidl's best) installed.

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The lid on and ready for a test. I still have to find a piano hinge for the lid!

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The 6mm dia tube sorted the sand flow problem and I was able to blast the above 6 wheeler bogie part to a lovely silky finish in about 2 minutes. Blowback up the sand tube happens every so often, but pausing the blasting allows the sand to flow down again. Best thing is I could blast this part without having to refill the airbrush hopper every 20 seconds, I reckon a full bottle of sand should last for about 1.5 hours of blasting.

Some more tweaks will be done as I process more parts.......

Eoin

 

Edited by murrayec
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Posted (edited)

Proxxon MBS 240/E coolant upgrade;-

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I bought one of these last year, mainly to cut metal, including steel. When buying it I found the coolant tank & tray optional extras are not available any-more! When cutting steel a coolant system is required if one wants the blade to last a reasonable amount of time.

So I had to make my own;-

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An oven tray of suitable size was found in Woodies, the tray was drilled mounted on a timber base with threaded inserts in the base.

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Drilled the tray and soldered in a brass pipe for the coolant drain.

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Two sheets of 10mm thick Tufnol were cut to form a riser under the saw and then the machine was bolted down. The tray outlet pipe just hangs over the edge of the timber base where a container will be hung to catch the coolant.

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2 no. aluminium pipe connectors were turned up, threaded, and screwed into the table outlets.

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Drain pipes installed.

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These are the parts for the coolant jar (an old Swarfega Tub), the plan is to be able to remove the jar easily, if not in use and for storing the machine away.

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The jar sits in the bracket like this (upside down for the photo)

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The bracket has a hanger strip on the back to hook onto a bracket fixed to the saw body.

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The bracket on the body.

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Hung!

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The jar on, which will be glued to the bracket after painting.

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The outlet is a brass fitting turned up and fitted to the jar using rubber washers to form a water seal.

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Tap and 90 deg outlet fitted, the tap is an aquarium air pump tap!

I'm going to wait until I paint the plywood jar bracket before I test the setup, I shall post up a few photo when I do.........

Eoin

 

Edited by murrayec
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Wow! This is not something I need to do, or would ever attempt, but that's some serious machinery and equipment you have there and it's obvious you know how to use it. Thanks for sharing all that :)

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