My little engine (continued)

[GarryCParticipant @garryc]

Hi Clive and Jason

Thanks – this is the first time I've tried anything this small, I've just gone back to lathe and using a little over 1000rpm and my knife tool that I made – my mike is reading 0.016mm difference end to end and the finish is really nice – not even tried more than one pass at the same setting yet… great, can't thank you both enough. Bit more learning done..!

Garry

[GarryCParticipant @garryc]

Ended up with .01mm difference end to end which is brilliant given what I had first time – so didn't need any centre support after all just a lot more oomph and it was much better to hand feed.. With more time spent could have got even closer..

That turned out to be a nice little exercise….

Thanks again..

I would have been better off with a much smaller parting off blade I think.. Really pleased with how the Knife Tool worked.

The Pin was made from Mild Steel..

Cheers.

Garry

 

Edited By Garry_C on 25/06/2015 09:49:51

Edited By Garry_C on 25/06/2015 09:51:17

Edited By Garry_C on 25/06/2015 09:52:58

[Ian S CParticipant @iansc]

To get an accurate small diameter, say .030" from a bit of .250" bar, do it in one cut, fine feed, keep the speed up, Have a Just a fraction over the 5/16" out of the chuck, enough to alow you to cut it off

[steve de24Participant @stevede2433577]

Garry, nice job on the con-rod.

Question regarding the crosshead bolt drawing. What does the small length of plain section (outboard of the 1/4 x 26tpi thread) do? Does it fit with another part?

Advice sought from the experienced guys on here – would it be better to make the crosshead in bronze?

Keep up the good work

Steve

[GarryCParticipant @garryc]

Thanks Ian, that's one that I will be remembering to try, I can imagine it working well..

(i'm well chuffed at the moment, I've just picked up an old Musket Ball in the garden, never found one before..! Bit of a Time Team fan..)

Cheers

Garry

[JasonBModerator @jasonb]

Yes looking at the book it was originally a one piece casting in SG iron. The piston rod will be a lot easier using a bit of stainless than trying to turn it parallel plus there is little risk of it rusting unlike the iron part. I would get the thread into the crosshead quite early on and screw in the pistion rod, then use the rod as your datum that way all the surfaces will be cut true to the rod. If the rod was screwed in last and the thread a bit off you will have problems.

Unless the engine is going to do real work a steel crosshead should be OK and not pick up on the steel guide plates but could be case hardened if needed. Garry is it definately a block of steel, the surface looks a bit more like its been sawn from an iron block in which case it will slide along fine.

Only thing I can think of for that reduced dia beyond the thread is to fit a pin to stop the nut comming off.

[GarryCParticipant @garryc]

That sounds like another life saver Jason, thank you very much. I wouldn't have done that I'm sure. Needless to say I will now!

I had also wondered about the crosshead being Steel and in moving contact with the Steel Guide Plates… It won't be run for long periods though (assuming I'm successful in finishing it that is) – It'll be good to get to look at what's involved in case hardening generally as well in due course..

The entry from the Drawing 'stock list'…

The photo of the Engine in Stuarts catalogue seems to show the Crosshead Bolt without that 'extension' of a reduced diameter – showing the end of the nut and the bolt pretty well flush together..

and thanks for the comments Steve..

Garry

[GarryCParticipant @garryc]

The Crosshead Bolt today – just need to part off tomorrow and do the hole for the Locking Pin. Have to be careful doing that, but I have a plan!

My new knife tool has been invaluable again today, don't know how I've managed without one..

The Bolt does have some important dimensions so did take me a while to do – think it should be ok, nice fit through the Con Rod, I've checked the shoulders are clean as I can make them and the dimension across the Con Rod so that when tightened its not closing the Fork Gap should be ok – 1/2 thou excess on the drawing and I should be pretty close to that..

The Crosshead Bolt Drawing.

The supplied piece of Mild Steel bar was barely long enough again – so I used some of my own to be a bit safer holding in the chuck..

The Fork and Nut will fit right up to the shoulders.. Went 4 thou undersize on the thread core when relieving the shoulder, I got a bit carried away when all the nut needed was a touch with the spanner – should have tried the spanner first before taking it down that little bit more. But its ok. 1/4 x 26tpi thread and the nut a nice close fit..

Just need to part off and do the hole for the Locking Pin.

Cheers.

Garry

Edited By Garry_C on 26/06/2015 14:46:00

[GarryCParticipant @garryc]

Here are far too many photos of me finishing the Crosshead Bolt.. Great Fun..

I should have cleaned it up a bit beforehand so apologies some of the photos not too good and a bit dirty..

Lined up in the Mill for drilling. Just after parting off in the Lathe.

Trying to show the shoulder protruding very slightly to prevent the nut from closing the Fork gap.

I did as Andrew Smiths booklet suggested and put the Pin all the way through the top of the bolt – it was easier. The pin doesn't show too much.

The nut tightens just as it should I think / hope.

The finished Crosshead Bolt. Its a pretty tight fit (hoping thats a good thing) – I've had iit together and apart lots of times while finishing and the Pin is already looking well used.

Hope it was of interest..

Cheers

Garry

Edited By Garry_C on 27/06/2015 13:46:54

[Gas_mantle.Participant @gas_mantle]

It's looking good Garry, do you think she'll be steaming away by Christmas ?

[Clive HartlandParticipant @clivehartland94829]

It looks as if you have room there under the nut for a nice chamfered washer. perhaps also smarten up the nut.

All very good so far.

Clive

[GarryCParticipant @garryc]

Hi Peter

Thanks, lots still to do yet – I've no real idea of how long it may take and I'm so very slow taking it forward but I'm enjoying it at that pace. Just noticed and been reading some more updates again in your build thread and it does make me look like I'm standing still though..!

Hi Clive

Thanks as well, yes that nut does look very 2nd hand, don't know why that is – now you've mentioned it I'll remember to clean it up when it comes to final assembly… The washer comment is interesting, I keep promising myself a trip to a 'steam' museum somewhere to check on little details like that on the real engines… Must do it this summer.

Cheers.

Garry

 

Edited By Garry_C on 27/06/2015 20:02:09

[Clive HartlandParticipant @clivehartland94829]

I only mention it because it would take up the waste thread outside the nut, the washer would leave the thread flush with the nut!

Clive

[GarryCParticipant @garryc]

Ah see what you mean Clive, I like your attention to detail..!

Cheers.

Garry

[GarryCParticipant @garryc]

Just a quick session earlier today – making a split sleeve to use holding the Piston Rod in the Lathe tomorrow..

I'll make sure it is throughly free of swarf and deburred first of course..

Cheers

Garry

Edited By Garry_C on 28/06/2015 15:02:51

[GarryCParticipant @garryc]

This looked like it had to be the easiest part to make on the whole engine but threading the Stainless Steel by hand with the chuck wasn't easy – finally cut the thread with the die fully open and then another pass tightened up to get a better thread and one that fits a test nut I was using. I did used to have a tailstock die holder but it only took larger size die's – let it go with my old lathe, (stupid as I should have kept it for my next lathe), I'll have to get one that fits more sizes, it would have made this a better and easier job all round if I'd had one i think. I'm hoping to be able to wait before trying screwcutting on the Lathe until I've got one with gears rather than 'change wheels' – but I don't know anything at all about the subject yet..

There are only a few dimensions involved with this and I've double checked that all is right – but I seem to only have two and a half threads at the Crosshead end – have to see how that goes or I'll be having to redo maybe.. Doesn't look right somehow.

Checked again both ends that edges are clean and a nut will connect with the shoulders, but I'lll be able to test properly when the mating parts are done…

The split sleeve worked perfectly and left no marks….

The finished Piston Rod.

Cheers

Garry

[roy entwistleParticipant @royentwistle24699]

Garry Have you made sure that the 3 3/4 dimension from the piston thread shoulder is to the centre of the cross head bolt hole?        Just a thought        It seems to be a very odd way of dimensioning the length of the piston rod

Roy

Edited By roy entwistle on 30/06/2015 15:03:12

[GarryCParticipant @garryc]

Hi Roy

Thanks for the reminder, I haven't started the Crosshead yet – the plan is to get the Piston Rod fitted to it as soon as poss (as Jason suggested), i can then mark out the 3 3/4"…

I've been a bit bemused by having to work out dimensions on the Stuart Drawings sometimes, many times thinking I wonder why they don't simply put a measurement on for something – but all the info needed has always been there, I had thought that perhaps this was just normal for engineering type drawings..! No probs about it, just need to do a bit of calculating sometimes.

I'm to have a look at the Crosshead next, the one thing that I have been wondering is about the 1/16" angled hole and if I would be right this time with the assumption it is an oil hole – just in case anyone knows. I must admit to not having checked the assembly drawing around it yet though ..

It looks like I'll need to order a bull nose milling cutter or cutters once I can see what size I'll need..

Cheers.

Garry

[JasonBModerator @jasonb]

Yes its an oil hole, usual to put a bit of a CSK at the top which makes it easier to oil and acts a sa small resovoir. If you wanted to go to town you could add a small oil pipe and brass oilpot.

Depending on what size bit of metal they have given you the two 1/8" radius cut outs could be done by drilling and then cutting away the waste. or if the metal is a bit tight use a 1/4" milling cutter and make a series of plunge cuts taking say 0.010" at a time to give the curved cutout. Both will save you having to buy a cutter. See the governor latch in this thread for an example of plunging with the mill

The way the rod is dimensioned is quite common as its the length between shoulder and the centre of the hole that is the critical dimension, you could be a bit out with the rod and/or cross head but provided the final size was 3 3/4" you will be OK. It may also originate from the old drawings that had this as a single casting not two bits joined together

 

EDIT, another way to do the curved cutouts if metal is tight would be to clamp some scrap steel to the side, bit like this

And when you pull them apart you get a half round or whatever you wanted

 

Edited By JasonB on 30/06/2015 17:37:55

[GarryCParticipant @garryc]

Jason, many thanks thats really useful – I've just been sat staring at the top photo and its just clicked..!

This job is different from anything I've come across before – its already making a bit more sense and easier to see now after this..

edit: and I've just looked at the link. Some amazing things there for sure, but I can see better the plunge milling as well..

Cheers.

Garry

Edited By Garry_C on 30/06/2015 18:13:34

[GarryCParticipant @garryc]

Just starting the crosshead today and already I've got myself a bit stuck at the moment – I should have realised this before I'm sure. The hole for the Piston Rod is so shallow at 1/8" that its not deep enough for the tap to start, not even the plug tap..

All I can think to do is grind off the taper on the plug tap..

I thought I'd put this here just in case I'm missing something silly..

Cheers.

Garry

[Anonymous]

The answer is a spiral flute tap, specifically designed for blind holes. They look like a plug tap, but have spiral flutes which direct the swarf upwards, out of the blind hole. I tend to use them as a matter of course, as you only need to buy one tap per thread size. Although intended for machine tapping, for which they work very well, they are equally useful for hand tapping.

<Rant>

Personally I think that 'designers' of commercial model engines should be forced to build one before plans are released. Then they would think twice about doing dumb things like using very shallow tapped holes.

<End Rant>

Andrew

[GarryCParticipant @garryc]

Hi Andrew

Thanks thats very interesting, I didn't know about them but know what to look for now, cheers.

Meantime (and before I saw this..) I did grind off the end and it seems to have worked fine, I think luck is still with me at the moment..!

and I agree 100% with the rant..!!!!

I'll put some pics up later..

Regards

Garry

[GarryCParticipant @garryc]

The little hole had a big bite after all…Luckily all I've done is drill a hole, so no real harm done – as I'll have to restart it..

After grinding off the end of the Plug Tap..

this – oops. No taper left after grinding to start it square, not even in the mill.. I suppose I should have done a lot more checking before starting the tap..

But I have some slightly larger section bar in stock so I can restart and use a taper tap to start properly followed by my ground off one to get a thread right to the bottom – and then mill down to size. Also meantime I can have a look at getting a spiral flute as Andrew suggested..

Cheers

Garry

[Anonymous]

Never be afraid to modify tooling to suit the job.

The converse of spiral flute is a spiral point tap (gun tap in the US) for through holes, which has angled flutes at the point designed to push the swarf forwards and away. The beauty of spiral flute and spiral point taps is that you don't tend to get the swarf jamming the tap, so no turning to and fro to clear same. When machine tapping it is way quicker threading the hole than drilling the hole in the first place.

Andrew

[Author]

Posts