Member postings for Will Robertson

I found some advice on hard bonded and soft bonded diamond blades here

**LINK**

- I'm not sure how well this applies to diamond grinding wheels but I think it seems to imply that for finishing something hard like a lathe tool I should use a soft bonded diamond grinding wheel - I could be wrong though - fingers crossed...

I haven't got anywhere with finding out what "Steel 50" and "Steel 51" mean - think I'll just need to give them a try and find out what happens - any suggestions welcome!

Sorry - one more question - if I get a diamond grinding wheel for honing my HSS (or carbide) lathe tools should I get the "hard bonded" or "soft bonded" type?

Thanks - I think I need to be a bit cautious though - there seems to be agreement that the cylinder should be ground to a finish that still has microscopic scratches because these microscopic scratches help to hold some oil to lubricate it and that a polished surface with none of these scratches wouldn't hold the lubricating oil so well - I might be wrong in this though.

I've found someone who carries stock of "Steel 50" and "Steel 51" now - unfortunately I'm having difficulty working out what Steel 50 or Steel 51 means - can anyone suggest what it's machining properties are like or what the equivalent BS number would be?

Could machine a small cylindrical holder for them with a point to burst them as you screw the top on and a small valve to let the CO2 out as required - a handy source of small amounts of compressed gas when a compressor isn't nearby. Could also be used to power a steam engine for short periods of time for quick, highly portable demonstrations.

Handy as a cryogenic agent but in these tiny quantities may not be much use for anything.

>If the kids of today did what we did in our schooldays - they'd end up in Guantanamo Bay wearing zip-ties for bracelets.

I think they're planning to ban breathing soon because of the potential health risks...

Hi Jason,

Thanks - I'll take different grade of sandpaper and make scratches on some scrap steel sheet with it then I'll compare the visual appearance and feel of each 'grade' of scratches with the visual appearance and feel of the bore and that should give me an idea which grade to start at (hopefully...). Veritas go all the way to 90 but I suspect that that might be too coarse. I'm guessing from the feel and appearance of different grades of sandpaper compared to the bore that I should maybe start at somewhere round 300 - does that seem reasonable? I'll try it out as described above and let you know how I get on.

Hi HomeUse,

Thank you very much - this is the only place I've seen 1000 grit carbide for sale. I might also order some more stuff from them and get around to polishing some of the stones I find on the mountains some day (or some of the stones that find me in the case of rock falls...)

Will

Back to the cylinder bore for a moment - I think I've got a supplier for Veritas lapping grit (silicon carbide). After boring should I hone the cylinder bore with the 600 grit or should I use a coarser grit (e.g. 400 grit) first then the 600 grit? I don't mind if using the 600 grin means that the honing will take a little longer - washing everything to change grit would take a lot of time as well.

I'd like to use 1000 grit or paste but the 1000 grit always seems to be diamond, not carbide.

Will

Hi Gordon,

This sounds very similar to what I'm planning - I've got heat resistant bricks and my furnace will be much smaller than your friend's (only for soldering at 600C - not for foundray work). I'd love to get my paws on the burner from an old central heating boiler but so-far I haven't managed.

Will

I've got more machining done for the restoration of the S50 - I'll try to post some photos. Every step of the way I've been guided by advice from people on this forum - I'm very grateful.

For my own engine I'm thinking more about the problem of heating the stock for the cylinder and the mounting flange for the valve assembly to 600 C to solder them. The high temperature heating wire I got turned out to be much springier than I was expecting so I looked again at the idea of a paraffin or diesel fuelled furnace.

I built a diesel burner with a simple atomiser and fan fed air supply but the atomiser produced droplets of diesel which were too large and had far too high a flow rate, resulting in a large, yellow low-temperature flame - useless. One hint of hope did come as the diesel in the pressure tank ran out and a mixture of diesel and air passed through the atomiser - that gave a very fine colloidal diesel mist which looked almost like smoke and burned beautifully with an intense hot, blue flame. If I could only create that reliably... That gave the idea of using a compressed air to make something similar to those perfume bottles with a rubber bulb and air tube attached that you see in 1930s films but I don't know if this would give the very fine droplets of diesel that I'm looking for.

Now I'm thinking about vaporising the fuel instead. Does anyone have any advice about how to make the orifice that the vaporised diesel passes through in the Venturi effect mixer of the burner? I made this sort of burner often when I was a child but the fuel was ways LPG - I made the orifice by gently hammering a piece of copper brake pipe until the right diameter of hole was made and I got the right sort of flame. If I burn vaporise diesel, I need to be more aware of the need to prick the jet to clean it and keep it free of the deposits that tend to build up in this sort of burner.

D'oh - sorry - yes - you're right - I wouldn't have got a cross-hatch pattern that way. I'd have had to take the workpiece out and turn it around.

Thanks for your advice about using the DTI - I hadn't thought about using it in these circumstances thought I should have - a significant help since parts of the readout on the handles are too rusted to be easily readable.

Thanks very much for all your advice and taking the time to teach me these things.

I just realised that anyone reading the above post would think that I was fairly dense. Obviously, I want to keep the direction of rotation the same and reverse the direction of feed so that the boring tool will cut on the way out as well as on the way in and leave a good cross-hatch pattern. I'm blocked from doing this unfortunately because the pin that holds in place the lever that engages and disengages reverse gear for the power drive is rusted in position and penetrating oil for several days followed by persistent use of a small hammer couldn't move it.

Thank you very much. Using the cross slide in this way seems a great way of handling this situation. Is it OK simply to put the lathe into reverse to bring the boring tool out, adjust the cross slide than run forwards to take another cut? (I'd normally want to move the tool out of contact with the workpiece before reversing but there's almost a complete revolution of play on the transverse feed so I'm guessing that it's very worn and I'm not sure whether it would accurately get the tool back into exactly the same position.)

Unfortunately I left all my tool steel at home and the lathe I'm using is on a farm in Arctic Norway so I don't have any with me to make a u-shaped tool. Hoping to get a fine diamond grinding disk to help finish home-made precision tools.

Thank you very much for the detailed photographs of your engine - it's good of you to take the time to photograph each step in detail and a big help to folk like me who're learning.

The machine feed was pushing the apron more slowly than I could have managed by hand - I'd been able to set up a gear chain to give a fairly big gear ratio for the leadscrew. The pitch of the thread on the leadscrew meant that even though the leadscrew was rotating slowly the feed was fairly fast.

What's the slowest rate of fed that it's reasonable to expect to find on a lathe? A friend warned me a while back that on large lathes the minimum rate of feed was often too fast for precision work but I've never been sure what it's reasonable to expect in terms of minimum feed rates in a lathe.

(I know of one individual who, in desperation, declutched the leadscrew from his lathe and drove it from a custom gear chain and the DC motor and speed control from an old MIG welder!)

The cross-slide was rusted badly with a big variation in friction over its travel so moving it at a constant speed by hand would have been very difficult.

Apologies for my silence for a while - workload increased a lot towards the end of the year.

I got my paws on a very old, large lathe with a 4 jaw chuck in a farm workshop to re-bore the cylinder of the S50 (the bore was in such a bad state that honing couldn't repair it). Mounting the two largest and two smallest gears in the gear chain and setting the leadscrew gear box to the lowest speed to give the maximum gear ratio for the lead screw gave a leadscrew movement of 0.12mm per revolution of the workpiece - which was a lot faster than I'd like but the best I could do so I went for it.

Using the Ifanger boring bar.

Despite the age of the lathe and it being badly rusted it did a magnificent job of the cylinder bore - says a lot for the quality of the engineering that built the lathe. My only regret was that the fast feed relative to the speed of rotation left a slightly threaded surface on the bore - ideally I'd have used a much lower feed rate but that didn't seem to be possible on this lathe. Although there's a slight thread the bore looks much more dimensionally uniform than it was before re-boring.

Sorry about my silence - work has become a lot heavier over the last few weeks so I haven't been able to spend as much time as I'd like on the engine.

Re. the restoration of the S50: I dismantled two of the jaws on the 4 jaw chuck easily. The other two jaws seem to have some damage to the ends of the threads and so I can't dismantle them completely. At the moment this is preventing me dismantling them and mounting them on the milling machine to true the metal pieces welded onto the ends of the jaws. I'm not sure whet to do now - maybe another try at dismantling these jaws or maybe try to get use of a lathe with an unmodified 4 jaw chuck.

I'm being very cautious about truing the modified 4 jaw chuck - it doesn't belong to me and I've no idea where or whether I could get a replacement so I don't want to make a mess of it.

Re. my own engine: The electrical heating elements arrived to build an electric furnace to braze the cylinder to where it would mate with the valve assembly. I was anticipating something like the coils of nichrome wire used in heaters - which is fairly malleable and easily handled - what arrived were coils of much more springy wire than I was expecting so I need to give some thought to how that can be safely kept in enough tension to prevent it shorting out with disastrous results.

I found an interesting approach to cylinder boring in the hydraulics community - their approach is simply not to bother attempting it - metal stock is bought in 6 metre lengths already precision bored so all that's needed is to cut the required length and fit the other parts needed to make the hydraulic cylinder - much cheaper than buying specialist boring equipment for long cylinders.

I was thinking about something like that - maybe with the milling machine or a final cut using a boring tool or a turning tool with the jaws reversed to face out the way and talking very light cuts (interrupted cut of stainless steel could be tricky) to true the metal plates on the jaws. The snag is that I've never tried to do anything like this before and the chuck doesn't belong to me so if I mess it up it doesn't really bear thinking about...

I've been trying to get the cylinder of the S50 mounted in a 4 jaw chuck so that I can get the bore sorted out but things aren't going according to plan. The 4 jaw I'm using was modified at some point in the past (not by me) by welding metal blocks onto the 4 jaws. The metal blocks aren't perfectly true and the distance between two of the 4 jaws varies by 0.28mm between the front and the back of the chuck. I'm not sure how to handle this - in the past I've always relied on assuming that the jaws of a chuck are near enough perfectly true.

I know that I need to have at least one jaw which is true so that I can put the valve face against it and use that as datum. The hole in the centre of the 4 jaw is too large to allow me to use the back of the chuck as datum. The jaws of the chuck are a little shorter than the cylinder so I'll need to use some soft metal between the jaws and the cylinder to hold the cylinder as well as to avoid marking it.

I tried taking off the jaws and cleaning the surfaces they ran on to make sure it wasn't any loose swarf causing the problem but that didn't help. I also had a look at buying a new chuck but CTC only do 3 jaw. Not sure what to do. I could maybe ask someone else who has a 4 jaw if I could use theirs.

Ahh - OK - now I understand...

DraftSight seemed to default to a text sise of 0.2 - which was far too small so I doubled it to 0.4 - which still seems too small - should I just ignore the default and keep increasing the text sise until it looks reasonable? I couldn't find a way of changing the text sise for all text in a layer or drawing at once (I can change the colour of all the elements in a layer easily but I can't find a way of changing the text sise of all the elements in a layer or drawing).

Will

Hi Jason,

Sorry to go quiet for a few days - friend visiting.

I saw that you used a white background for your drawings - I reckoned that I should do likewise but i couldn't work out how to change the background colour of an existing drawing in DraftSight - I tried Tools > Options > System options > Display > Element Colours > Sheet Background but the sheet background seems to already be set to white - whatever I change it to the background on the drawing displayed on screen stays black. I must be doing something really daft...

Will

Hi Jason and Clive,

The problem turned out to be that the forum software was compressing the JPEG images and that was causing the text and a lot of the other detail to become illegible

I've uploaded the next set of drawings (the main cylinder) to here where they're not compressed

**LINK**

I reckon that the final 12.8mm drill leaves too much stock to be removed - I think I might have found a larger drill though. Ideally, what sise should I drill to ready to bore to 20mm diamiter?

JPEG is designed for photographic images (JPEG stands for Joint Photographic Experts Group) and isn't good with technical drawings. SVG (Scalable Vector Graphics) is much better for drawings so I can upload them in that format as well if it would help.

Sounds like a mixed situation re. honey production - it maybe depends on the skill of the individual beekeeper and local weather variations.

Will

Edited By Will Robertson on 01/11/2012 14:15:06

Edited By Will Robertson on 01/11/2012 14:42:33

Hi Jason,

Thank you very much. Here are my replies to Jason's points (originally sent by email but put on here in case anyone wants to correct me on anything or has anything to add.)

1) Yes - I'm uncertain about that as well - the design and dimensions came from a model builder here - the design is very similar to one that's used for hydraulic cylinders. I've got a fair-sised piece of PTFE (Teflon) stock so I can afford to get it wrong a few times and have to re-make them.

2) I wondered about that - it didn't 'feel' right - I'll change to the way you recommended. Should I use an M4 coarse or M4 fine thread? (Maybe I should go for M4 fine just for uniformity since most of the rest of the engine seems to have ended up using fine threads.)

3) Yes - the whole piston is 10mm long - I'll reduce the length as you suggested.

4) Is stainless steel not suitable for the piston in a brass cylinder? - I wasn't sure. Ideally I'd make a gun metal (bronze) rather than brass cylinder but a friend gave me a big chunk of brass stock so I felt that I should use it. I've become more and more interested in cast iron and in the future I'd like to make an engine with cast iron cylinder and piston but I'll avoid cast iron in this particular engine to keep it rust-free. I'm usually sceptical of aluminium in a steam engine because I'm concerned that contact with air and hot steam may cause it to build up too thick an oxide layer and jam - but this comes from school chemistry not engineering experience.

5) Thanks - I'll halve the thickness of the cast iron rings.

6) Thanks - I was following Greenly on this but I noticed that hydraulic engineers often didn't have a solid ring between the split ones.

7) For the PTFE (Teflon) with a scalpel and a good light. For the cast iron I have no idea but I hoped that somehow I'd manage to find out along the way or that someone would tell me (maybe using a slit saw or a very sharp and very carefully positioned chisel?).

8) Thanks - I didn't know how springy cast iron was - I'll give that a try - it makes sense since it's how internal combustion engine pistons and rings are made.

I've updated the drawings with Jason's suggestions.

Hi Clive,

Thank you very much - I remembered the problems you'd had and left part of the piston un-threaded but it was only a small part and probably wouldn't have been enough. I think I got the idea that I could thread perfectly true from the design of the S50 but the more I think about it the more I realise that a tapped thread is always likely to be a less true than a turned or bored surface.

Do you have any views on whether the thread in the piston should be metric fine or coarse?

I apologise for sending SVG files with my plans by email and having only unclear images on here. I'm looking at ways to put clearer images online so that everyone can give their thoughts.

PS - I had a quick look in Greenly and he agrees with you both re. joining the piston and piston rod.

Will

Edited By Will Robertson on 31/10/2012 19:25:03