Is There Time - The Build of Willy.

[PaulR]

It's been ages since I tapped a hole in cast iron but breaking a tap in some sticks in my mind vividly (the only tap I can recall breaking). How tricky were the M1.6 holes and do you have any general tips for threading CI? I have that almost complete cast iron pig that I'll be using to make various parts in future.

[Jasonb]

A piece of wooden dowel was turned down to a firm fit in the cylinder, loaded with a mix of oil and 600g silicon carbide powder and the cylinder lapped.



The piston material was then faced and turned 0.2mm over diameter before being drilled & tapped M3



It was then screwed onto the piston rod for final turning to diameter using the cylinder to gauge the size and a small oil groove added. No photos of the piston rod as it is just a piece of 3mm stainless steel tapped M3 at both ends.



A small offcut of brass was milled to a 5mm x 5mm square section, the end squared up and a hole drilled and reamed 3mm for the crank pin.



It was then held end up to drill and tap for the piston rod. After sawing off the end was rounded over concentric to the pin hole.



Again no pictured of teh cylinder pivot as it is also just a piece of 3mm stainless threaded at both ends. The spring adjusting nut was turned from 8mm brass and rather than a hex hed like I used on kelsey I formed a half round bead and then using just one wheel of a pair of diamond knurls cut a good representation of a rope knurl.



And I think that just about covers all the parts.



After a successful test run the engine was stripped, cleaned and painted.



Still not too late to guess how long it took me to complete.

[astroud]

It's been ages since I tapped a hole in cast iron but breaking a tap in some sticks in my mind vividly (the only tap I can recall breaking). How tricky were the M1.6 holes and do you have any general tips for threading CI? I have that almost complete cast iron pig that I'll be using to make various parts in future.

Hi Paul, a workaround I have seen quoted is to drill and Loctite in a brass plug which then can be tapped. Less worry about breakage and if it goes pear shaped the plug should be more easily removed to try again. Of course use depends on the clearance around your tapped hole.

[Jasonb]

Sorry, missed your question.

I don't do anything special when tapping cast iron to what I do for any other holes.  I always guide the tap while the drill is still above the hole, nothing fancy just a piece of steel rod drilled one end with a ctr drill and a point turned on the other. Held in the drill chuck it guides the top of the tap while light pressure is applied to the quill.

tap wrench on the round part of the tap so it will hopefully slip before things brake

No lubrication for CI

Larger size sI tend to use Spiral flute taps but in M2 and M1.6 I use traditional taps.

[pgp001]

It's been ages since I tapped a hole in cast iron but breaking a tap in some sticks in my mind vividly (the only tap I can recall breaking). How tricky were the M1.6 holes and do you have any general tips for threading CI? I have that almost complete cast iron pig that I'll be using to make various parts in future.

Hi Paul, a workaround I have seen quoted is to drill and Loctite in a brass plug which then can be tapped. Less worry about breakage and if it goes pear shaped the plug should be more easily removed to try again. Of course use depends on the clearance around your tapped hole.

Paul

Similar to the above, I sometimes use the brass plug method for small tapped holes in tricky materials, I often use M1.2 & M1.6.
The difference with my method is that I make the brass plug with tapped hole already in it using the lathe, then loctite it in place. Much easier than tapping it when fitted.

Phil P

[PaulR]

Hi Paul, a workaround I have seen quoted is to drill and Loctite in a brass plug which then can be tapped. Less worry about breakage and if it goes pear shaped the plug should be more easily removed to try again. Of course use depends on the clearance around your tapped hole.

Another good tip to file away for future use - thanks!

[PaulR]

Similar to the above, I sometimes use the brass plug method for small tapped holes in tricky materials, I often use M1.2 & M1.6.
The difference with my method is that I make the brass plug with tapped hole already in it using the lathe, then loctite it in place. Much easier than tapping it when fitted.

Ah, so the loctite doesn't have to resist the rotational force of the tap if doing it the other way round, neat, thank you!

[PaulR]

I don't do anything special when tapping cast iron to what I do for any other holes.  I always guide the tap while the drill is still above the hole, nothing fancy just a piece of steel rod drilled one end with a ctr drill and a point turned on the other. Held in the drill chuck it guides the top of the tap while light pressure is applied to the quill.

What does the pointed end of the steel rod do?

Sorry for taking things off topic!

[Jasonb]

That end gets used for taps that have a small ctr hole in the end which you tend to find as the size gets bigger.

[PaulR]

That end gets used for taps that have a small ctr hole in the end which you tend to find as the size gets bigger.

Ah, I see, thought I was losing the plot even more!

[Jasonb]

Although I have posted the videos in the Kelsey thread on ME I will also put them here so it is all in one place

<a href="https://www.youtube.com/watch?v=OzkpJuu9cZg" target="_blank">http://www.youtube.com/watch?v=OzkpJuu9cZg</a>

During the test run and while doing the video above I could not get Willy to run as slowly as I would have liked, he was a bit stiff and he needed a good flick to get him going when the regulator was at a low opening but as I wanted to get the completed video out before the end of the year run as it was.

With a little more time I had a fiddle and there was a bit of tightness when turning the flywheel over. I tracked it down to the big end which was a bit tight on the pin, running a hand reamer through the previously machine reamed 3mm hole just eased it enough to free things up. I think what had happened was that I rounded over the big end by screwing it to an arbor and using the rotary table, the cap head screw had brused the edge of the hole slightly.

With the engine back together and no change to the pressure it ran a lot slower and if the crank was in the right place would self start as the regulator was opened – something it did not do before.

<a href="https://www.youtube.com/watch?v=Ljj8m4WARtk" target="_blank">http://www.youtube.com/watch?v=Ljj8m4WARtk</a>

One other bonus of this fiddling was that I found the small adaptor for the airhose I had made could be screwed in too far and partially block the inlet drilled passages. With it not screwed in so far there was a good improvement in speed, going from 2700rpm as seen at the end of the first video to 3687rpm an increase of almost 1000rpm for the same pressure but with no restriction to the passages

[crueby]

Excellent!!

[Michael S.]

A really well-made little motor.

That inspires me to build something like that myself.