High Pressure Steam Table Engine

[Jo]

Now for the tricky bit: the straps  We are going to do this the opposite way from what seems sensible 

Having made two bits of steel the same 15.8mm width (yes one was 16mm  ) two holes drilled under diameter near the ends I can round the ends:



Two bits of bar with three rounded ends and one where the cutter caught 



Time for the slots. Having zeroed on one hole and knowing the distance to the other I can mill between them with a suitable small diameter cutter:



Moving to a bigger diameter cutter I need to first open up the two outer ends:



The slot was first opened up with an 8mm, then a9mm and finally a single cut under power feed using a lovely new 9.5mm cutter that Dave gave me. THANK YOU Dave 


The second needs a second hole drilled in it before I can do the same on it:




and the battery on my camera has run out  Time for a re-charge and a coffee.

Jo

[Roger B]

 

[vtsteam]

 

[Laurentic]

I missed this build but have now just read from start to date.  Very good write up, loved the detail in the set-ups and methods, all very clear and logical, as always, thanks for that Jo, and very nice workmanship too.  Will now watch this one out, so you have another following.

Just out of interest - what replacement hacksaw did you end up with? 

Chris

[Jo]

Hi Chris,

I brought a standard Eclipse frame but I am not impressed as the blade twists as you tighten the wing nut to tension the blade so it won't cut straight  I have to get  a pair of pliers on it to straighten up the blade to get it to cut straight. I can't see me remembering to do that every time 

Jo

[Laurentic]

Can't see that hacksaw lasting long as First Choice hacksaw for you Jo, OK as a first reserve maybe, but that sounds really poor, thought Eclipse was better than that

There are a bewildering number of different hacksaws on the markets with as many different prices to match, so knowing what may be a good one is not as easy as it may seem, as you have just found out, and as you point out many seem to have those rubbishy plasticy/rubber handgrips that go all yuckky in a short while.  Tricky one, hence the question!   

Chris

[ettingtonliam]

Have they changed the design? I've had an Eclipse frame for many years, and the pegs on both ends have squares where they pass through the frame, so they can't twist when I tension the blade.

[Jo]

The square ends are a loose fit 


Another thing you shouldn't do is buy milling cutters from Arc Euro and expect them to be the size quoted/ printed on them 

I just went to do the next bit on these straps which is to position the cotter pin slots. To get some idea of the spacing I put the end of one of the rods into the gap and found it rattled around  Out with the vernier and the slot was over width, check the cutter and 



The other Arc cutters are also oversized  Time to start again   :'(

Jo

[Jasonb]

The old Sandvik 225 was a good frame and what I still use, Bahco do one that is almost identical
https://www.bahco.com/gb_en/professional-hand-hacksaw-frames-with-aluminium-handle-300-mm-pb_225-plus_.html

Monument also do a similar one under their own name and also branded with other names
https://monumenthandtools.co.uk/monument-12in-hacksaw-frame-mon1921d

No sticky grips of loose end locations that can twist and they both have the 45degree option for sawing long strips of deep cuts

They must have sent you specials jo as all mine seem OK. Have you let Ketan or Iain know. Hope that big ears and the elves has not been putting them in the wrong boxes.  4-flute is not ideal for slots anyway.

EDIT just saw the photos and its the cheap ones you have, better to stick with the premium, no wonder you were given them, what is it they say about beggers?

[Jo]

They must have sent you specials jo as all mine seem OK. Have you let Ketan or Iain know. Hope that big ears and the elves has not been putting them in the wrong boxes.  4-flute is not ideal for slots anyway.

EDIT just saw the photos and its the cheap ones you have, better to stick with the premium, no wonder you were given them, what is it they say about beggers?

I just put it down to poor Chinese quality control again. I have labelled them all Arc Euro cheap and oversized.

If you have been following along you would have known I used then to skim off the last 0.25mm, or rather it should have been. I'll go back to milling down each side to get them to width.

Jo

[Jasonb]

I only have a 7mm one of those and bought it for counterbores so have not used them for "milling" beware the ball nose ones as are based on rugby balls or possibly aimed at the american market

That's what I tend to do particularly if the mating part has already been made, plunge the ends to size and then use a size down cutter and offset for each side and adjust to a good fit, takes a bit longer but not as long as remaking loose parts.

[Jo]

Having recognised that Chinese quality control continues to be an issue onward with converting perfectly good bits of metal into swarf...

A replacement piece has been made for the pair of side rod straps. This time before removing it from the vice I checked the slot:



As you can see it is nice and tight but having removed it from the milling vice it opened up again  this time I use a specialist tool (vice) to make a width adjustment  And checked the width again:



On the second on I left it a smidgen (technical measurement  ) smaller and it was a nice fit:



Now to work out how far down to cut the cotter slots  Then we can set about showing the joys of cutting them 

Jo

[Twizseven]

Looking very good Jo.

[Jo]

Flattery will get you everywhere 

Another Drawing feature  Cotter slot position and the length of the side rods straps

Looking at the big end drawing you can see there is a line I have ringed in green I will assume this is the front of the slot cut in the strap. Yes it is in front of the rear of the bearing but it is not doing any work (just looking tacky  ) )

At the bottom I have arrowed the line that seems to be representing the back of the bearing, the front of the cotter and the end of the rod  We need the cotter and pin to pull the rod and strap together around the bearing so we need the slot to move along rod so that it is actually in the end of the rod not a slit in the end    Ideally with 3mm but it is likely to need to be shorter.

Length of cotter slot: this has to be the width of the narrower of the top or bottom of the cotter. Once through one side of the strap, the rod and the other side of the strap it slides sideways and leaves a gap for the pin.  The key surfaces are the outside (furthest from the bearing) on the straps and inside (nearest the bearing on the rods. 5mm slot with a 4.76mm cotter top would work.

Lets not be hasty and I will think further on this. Might be best to draw it out 

Jo

[RReid]

this time I use a specialist tool (vice)

I left it a smidgen (technical measurement)

This is getting far too specialized and technical for me.    ( )

Still following along with interest and pleasure, Jo.