Stuart D10 bedplate- cast iron or granite?!

[gondolier88]

Hi,

I'm a regular reader on here, but not a regular contributor.

I'm currently machining a D10 as the power source for a 1:12 scale Royal Navy 50ft steam picket boat, along with a 3 drum Yarrow boiler.

I have found that the casting set I have bought is predominantly of mediocre quality with obvious chilling occuring to most of the castings- the cylinders were bad enough, but the bedplate is proving almost impossible.

First- I dislike some of the features of the D10- the main bearing designs being one such. I decided to file ( I don't own a milling machine or a lathe with T-slotted crosslide) the keeps square as per full size, make up some proper split bearings and hey presto. However upon filing the keeps I have found that the centre and one end keep have superhard skin to a depth of around .120"! You can imagine what trying to file that was like- it just became a mirror finish and impossible to remove. I decided to think out of the box and using half of a Keats angle plate, some Oak shim, badly misused faceplate clamps and a massive amount of luck I mounted the bedplate onto the toolpost mount on my 7x12 SIEG and centred a 5/16" milling cutter in the chuck. It coped with the centre keep admirably, but the end keep removed material from the cutter! It did mill enough out of it to make a decent bearing, but it would be out of size in comparison with the other two, and wouldn't feel to me anything more than being a bodge.

So, to those who have been there and done it all, what on earth can I do? My last resort is to visit my local freindly machine shop, but that's kind of missing the point isn't it?

Any help would be very gratefully recieved, thanks.

Greg

 

[Maryak]

A couple of suggestions

Get the bed annealed/normalised.

Build up a bed or machine from solid.

Hope this helps.

Best Regards
Bob

 

[rhankey]

Greg,

I'm about half way through making a Stuart triple at the moment. I also found some hard spots in the sole plate. I was able to mill my way through them, with some damage to a cheap Chinese milling bit. I haven't started on the cylinder head parts yet but am suspecting I might find some trouble on the exposed ears to which the cylinder head attaches to the vertical columns.

I feel for you, especially when you have limited options to work with. I believe Stuart will replace castings that are found to have defects, for which hard spots would be considered by most as a defect. However, as of the start of this year I understand that it is not clear whether Stuart is still in business or not, so I'm not sure if you want to risk sending them the defective castings back only to find you don't anything back. I understand their foundry is trying to take them over to carry things along. In any event, the replacements could have the same problem as they probably came from the same batch.

As Bob suggested, annealing the castings would be one good option. There are good posts on this site as to doing that. I haven't had to try doing so yet.

I have been dealing with the problem by using cheap Chinese cutters on the castings until I know that there are no remaining hard spots to work through. Losing a couple dollar cutter isn't going to have me lose any sleep.

I have also made some of my parts from solid stock rather than from the supplied castings. I did so as I wanted to make some of the parts in SS, and to make my life easier with machining very small parts. So, I've probably missed some of the fun that would have otherwise been in store for me.

Other than some small voids, and some castings being barely large enough to make the part, I've not had any issues with any of the gunmettal castings.

I hope your luck improves.

Robin

 

[gondolier88]

Hi Bob, Robin,

I had thought of annealing- I'll look up the posts on here as I had a go with a blowlamp, but not knowing how far to go and not knowing what problems I was aking for adding localised heat I didn't go through with it properly.

Of course building up is an option, but I have now put so much work into it that I really don't want to go that route unless I really really have to.

I believe ST is now in the ownership of RDG Tools, the current owners of Myford too.

I have been watching your progress with the triple intently Robin, your making a great job of it.

Interesting to hear your comments on the casting qaulity- I am a good freind of a well known model engine manufacturer, ST approched them to machine batches of their castings for them (so much for the 'machined by our in house engineers' line they used to pedal! Anyway, said friend tried machining them (in a workshop that is equipped to produce CNC'd parts to 2 microns that fit from machine to use without inspection for Eurofighter Typhoons) and couldn't produce them quickly enough because of the poor qaulity of the castings to make any money on them!

Thanks again for your help, I'll try the annealing route I think.

Greg

 

[Charles Lamont]

If this is becoming a general problem with ST castings then it is an enormous shame. The original company in Henley had a
fantastic reputation for the quality of their foundry work. What you have been supplied with is simply not good enough. Any casting that ruins an HSS cutter I would expect to be replaced FOC, and I would expect it to be done with good grace and an apology.

 

[Gedeon Spilett]

hi,
you should try to get a replacement part in Stuart, they are generally commercially understanding, if not and because you love file, I suggest that could file the piece with a cheap diamond needle file, usually very biting, or with the dremel and diamond grinding wheels.
I did this model some 30 years ago, the cast parts were first class in these days, and the kit contained also a forged steel blank for the crankshaft...

Zephyrin

 

[gondolier88]

I suggest that could file the piece with a cheap diamond needle file, usually very biting, or with the dremel and diamond grinding wheels.

Zephyrin

Great suggestion- I'll see how it looks after annealing, but I might try that, thanks. The casting is in the fire as we speak. If none of this works then I'll get back to ST.

Thanks again.

Greg

 

[gondolier88]

Well, thanks a lot guys, 3 hours in the fire baking, slowly cooled as the fire died. I heated it again the next day, a slight deformity corrected, scale chipped off and hey presto it is one entirely uniform easy to machine and file casting.

Really pleased with the outcome and it's down to your advice.

Thanks again.

Greg

 

[Swede]

Excellent, Greg! Well done. Did you lose much dimension to scale? That is one thing that bothers me about open-air heating of a part that is already machined - you lose too much material to oxidation.

 

[Mainer]

Wrapping it in stainless steel foil prior to annealing might be the way to go.

It is indeed sad that ST quality has deteriorated so markedly. When I built "Victoria" some 25 years ago or so, the castings were absolutely lovely to work with. Perhaps the new owner will get the problems sorted out.

 

[gondolier88]

Excellent, Greg! Well done. Did you lose much dimension to scale? That is one thing that bothers me about open-air heating of a part that is already machined - you lose too much material to oxidation.

In a word, yes, but I'll just make everything else to suit, as long as the centres stay the same the engine can afford to lose a few pounds to put it in health fanatic speak!

It is a valid concern though, stainless steel foil is a good tip, and something that if I needed to do in the future I would probably use.

Greg