High Pressure Steam Table Engine

[Jo]

Thanks Guys, Terry I hope this is a bit more useful for you.

There is a drawing feature on the cross head  If you add up the bits that are supposed to go inside the two slide bearings you will find they add up to 0.6mm too wide to fit in the gap    The only measurements you can adjust are highlighted below:



I've reduced those to 1.6mm each and it fits 



Now for the fun bit the taper. It needs to be just under 20mm long from the narrower section so I have marked that on the piece. I then loosened up the top slide, wound it back to the end of the taper which will need to measure 9.5mm diameter and wound the cross slide in so that the 3mm profiling bit touches the bar. Having found a spacer of the required thickness to provide me the correct taper, I then wound the top slide fully in, squeesed the spacer between the tool & material and tighten up the top slide. We are now set up for the correct taper for this item:



Having turned up a bit of the taper a quick measurement to check it is long enough and adjust the position of the SADLE if required.



Both sides done:



I hoped to hold it in a 5C square collet to mill either side:



But the collet is not true to its slot 



Another piece of quality Chinese tooling 

I had just set up to do the sides another way and a salesman phoned up  There is nothing worse when you are in the zone and someone phones up trying to flog you something and yak, I always loose my focus on what I was doing and have to walk away. It is so frustrating   .

Jo

[ettingtonliam]

I see what you mean, and thats annoying, but wouldn't it be good enough for what, after all, is a visual feature?

You seem to have come across a fair number of drawing errors. Are you using Clarkson drawings, or are they the ones currently marketed by Blackgates?

[Jo]

I see what you mean, and thats annoying, but wouldn't it be good enough for what, after all, is a visual feature?

The space between the two slide bars is 70mm and with that extra bit makes the crosshead with the bearings 70.5mm so it is too wide for the gap  = it will be jammed solid and will be unable to slide up and down with the piston rod

These are original Clarkson Drawings, of which I have two different ones which do not admit to their date/version etc I have no idea what Blackgates are doing in the way of drawings.

Jo

[Jasonb]

Also make sure you use the Conrod yoke drawing with the wider spacing not the one on the metricated drawings as that is a lot too narrow, might have suited the short crosshead you posted the other day that has gone AWOL

[ettingtonliam]

The space between the two slide bars is 70mm and with that extra bit makes the crosshead with the bearings 70.5mm so it is too wide for the gap  = it will be jammed solid and will be unable to slide up and down with the piston rod

These are original Clarkson Drawings, of which I have two different ones which do not admit to their date/version etc I have no idea what Blackgates are doing in the way of drawings.

Jo

Yes, I understand the bit about the cross head as drawn being too wide, but I was talking about your plan to hold the cross head in your square collet to mill the sides down to thickness.

[Jo]

Very true Richard: The little bit its out is only a visual surface on this piece.

I could go back to the original way I intended on doing it but I am already set up for another method 

I'll sleep on it 

Jo

[Jasonb]

You could loosen the pin on the 5C block and just hold the work true as you tighten the collet then original plan will work.

Now if only you had kept that indexer you could use the 1deg holes to set the job true then just rotate 180deg

I'd probably make use of the central hole to hold it on the CNC rotary table then the flats and the rounding of the central boss can be done in one setting

[Jo]

The connecting rod cross head was then mounted in a sub vice and centred up:



I first tried milling behind the piece  Then realised it was worth doing the front first:



And after the back:



Then off to the rotary table to round the centre:



I am sure Jason will explain to us where you have to be careful if you try to do the two flats on the rotary table 

You can see there is a little bump between the two curves:



A couple of rubs with a file and these are gone. Then use the Foredom to remove any milling cutter marks:



So it is not lost (stolen by the workshop gnome  ) best put it into place on the engine:



There is a second cross head that I really should do before going on 

Jo

[Jasonb]

What no buttons

Yes having it on just a central arbour like you do there is a risk of the work rotating so a bit of thought first to prevent that may help. Such as screwing the work through the central hole to a block than can include a stop at the rear. Also using CAD to get the exact point where the flat meets the boss can help save that little bump.

[Roger B]

it is indeed an elegant engine       

[Kim]

Beautiful looking crosshead, Jo! 
Kim

[Jo]

Thanks Roger and Kim,

The valve crosshead is much smaller and more fiddly. I initially started making it from 5.5mm square steel but then realised the original engraving shows the centre section slightly taller so started again using 6.35mm square. It is the same as the other crosshead except:



I decided to play it safe and supported the end while cutting the taper. Then there was not enough to securely hold it:



So I made an additional holding block so it would be more secure in the vice.

The two drawings show the middle section of this crosshead as different lengths. I chose to make it 34mm (rather than either of the original drawings  ) by scaling up from the engraving.



Jo

[crueby]

Looking great!   

[Admiral_dk]

Enjoy to see the fine parts and progress you make Jo 
But I need to some more of the parts it matches up with, before my imagination will create a functional picture 

Per

[bent]

As long as you have material left to file, no harm - no foul.