A Robinson from rejects.

[crueby]

Nice! No matter how good the setup appears, it is always a nervous time to do that drilling.

 

[Ian j]

A bit more progress on my engine built from bar stock/scrap!
Exhaust valve chest:-
Milled/drilled/filed out of a lump of cast iron. I messed up the valve seat so ended up drilling out to 1/2" and turned  a bronze insert to be a close fit, drilled this 3/16" and 5/16" and formed the valve seat then pressed in with loctite. After about 30mins with grinding paste seem to have a good seal between the valve and valve seat.Silencer made from stainless steel , there's no baffles in it, was thinking of putting a piece of the steel type dish scourers.

[Jasonb]

Thats looking good.

I'm hoping to get the reject of the rejects for this part and maybe a couple of others.

[Alyn Foundry]

Thats looking good.

I'm hoping to get the reject of the rejects for this part and maybe a couple of others.

You shall Jason, you shall !

 

[RayW]

I was making good progress with the inlet valve block until it came to drilling the 1/32" gas inlet hole. At my first attempt, the drill broke off in the hole after about 1/8" deep but fortunately, the broken part came out OK. I have since broken several more bits without progressing any further and I am at a loss to know what to try next.
I have been running the milling machine at its maximum of about 2000 rpm, but I suspect that I may need much higher speeds than that for such a small drill bit. I have also been using plenty of cutting oil.
I have a Dremel which runs at something like 30,000 rpm, but no way of holding it in a steady vertical position, and I am reluctant to invest in a special drill stand just for this one hole.
I would appreciate any advice as to the best way to proceed.

One thought I had was to drill out the hole to, say, 3mm to match the other holes, then fit a brass plug, which I feel would be easier to drill than the mild steel of the block.

[Alyn Foundry]

Hi Ray.

What's the material you have used for the valve chest? I know its not a casting as I didn't have any of those.

My own thought is to try annealing the metal by a little heat and very slow cooling. Then try to re drill the hole.

A plug of Brass " press fitted " might be a suitable alternative.

Cheers Graham.

[Jasonb]

Have you drilled the 1/16" hole yet as it may be catching as it breaks into that particularly if a bit out of line. Could try a bit of rod to fill the hole while you drill the small one.

I don't find the theoretical high speed is needed, I drill quite a lot of 1/32 Well 0.8mm split pin holes to retain pins and don't run the mill at it's max revs just somewhere near so maybe 1800rpm.

Maybe just a nasty bit of iron you have? Mine was from an old weight from a York multigym and quite nice to machine

J

[RayW]

Thanks Graham and Jason. The block is mild steel and has been machining very nicely except for this hole. I am nowhere near deep enough to break into the 1/16" hole yet Jason. As I said, I had only managed to get about 1/8" deep before the bit broke.
I have been using some bits that came to me with a lot of other workshop tools and I am wondering now just how sharp they were.
I think I will order some new bits first to see if that solves the problem then look at other options like annealing or drilling out and plugging with brass. 

[Jo]

I'm hoping to get the reject of the rejects for this part and maybe a couple of others.

It sounds like someone has given up on the idea of making his engine solely out of bar stock and is having to resort to more castings 


Ray - Yes you are drilling a "deep" hole (relative to the diameter of the drill) a good quality drill and careful pecking & cleaning out of the swarf will be called for. A sensitive drilling machine will also help 

Jo

[Jasonb]

Well as the first part I machined was the Cylinder casting it was never going to be an all barstock engine, then I went and found two other Robinson castings which sealed it's fate. Thought I would ask Graham if he had any flywheel castings and as he was making a trip to the post office what else may be knocking about in a dark damp corner of his shed, saves it all turning to iron oxide

Having to wait a week or two for the castings forced me to start another engine, this one won't have any castings, not even the flywheel and at least I know there won't be any nasty holes hiding inside the parts

I just used a 0.8mm bit from one of those cheap sets of 20 "micro drills" with all the sensitivity that a far eastern mill gives

[Jo]

We know the truth you only pretend to not find castings desirable 

I just used a 0.8mm bit from one of those cheap sets of 20 "micro drills" with all the sensitivity that a far eastern mill gives

Yes I also brought some of those Blue boxes of ex industrial micro drills from Tony at the Guildford show for £3 a box He normally brings a few more along to each show if anyone else wants some.

Jo

[Jasonb]

No these type of drill sets

[RayW]

Another milestone reached today with completion of the crankshaft. Last big job left to do now is to machine the flywheel casting, then it will be a matter of assembling all the various parts and checking for fit and alignment.
I still have the troublesome 1/32" gas inlet hole to drill, but I have received some new drill bits in the post which will hopefully do the job.

[Ian j]

Looks good Ray. Is it fabricated or turned from one piece of flat bar stock ?
Ive just finished the inlet valve chest, I too was concerned about the 1/32" drill breaking so I opted to drill this first and then the 1/16" hole working on the theory that this was less likely to break on reaching the 1/32" hole . All went well . The only problem was I was thinking about this when marking out and machining the main part that it ended up narrower than shown on the drawing, but only we know that
 How are you and Jason making the valves, in one piece or silver soldering the valve and stem together, I've tapped the stem and fixed the valve with a small BA screw is this ok do you think?

Like you I have just the fly wheel to do on my Myford !!!
Ian

[Alyn Foundry]

Good evening Ray and Ian.

My favourite casting to machine was always the flywheel, it came first every time.

Your crankshaft is looking good Ray, Silver soldered and pinned?

Ian, when you write “ fixed the valve “ are you suggesting that the stem is attached to the head with a small screw? I don’t see a problem other than minute leakage without a suitable sealant.

I can understand the reluctance to machining one from the solid but back in the day engine valves were machined from forging’s, I know this to be true because I have several unmachined Barker “ B “ type valve forging’s in my workshop.

I’m beginning to get a little excited as the first run day is rapidly approaching!

Cheers Graham.