Textile Mill Diorama

[crueby]

For the ports its not that important that the bottom of the hole be square, just to be deep enough to intersect the cross hole, but finishing the depth with the end mill works fine as long as it is center cutting, otherwise it just rubs and jams.

Chain drilling definitely makes the cutter's job easier, especially in steel - using a smaller drill for that is best as you say. Note that if you do not chain drill, and make a pass with the end mill through solid stock, the small size mills can flex a little and pull to the side as the flutes grab - best to use a smaller size there as well and get to the finished line in light one-side passes.
Sure you will get it - if any worries, make a test set in a bit of scrap bar to work out the sequence.
 

[Jasonb]

As your engine is not going to do any heavy work why not just drill 3 or 4 1/8" holes for the inlets which give a bit of metal between the holes, three 3/16" drilled holes for the exhaust and then with an 1/8" milling cutter just mill out a shallow rectangular pocket for the three ports.

[mklotz]

Thank you Chris. I understand.

I think if you use a twist drill first, you have to back off early and not let the drill go to its depth - it has an angle on the end that deepens the hole. The whole point of using a milling cutter is to get a flat bottomed hole to an exact depth - if the flutes of the cutter wlll let you go down that far.

How early do you need to back off?

A bit of trig will show that that value, x, is given by:

x =  (d/2) / tan (a/2)

where:

d = drill diameter
a = included angle of drill tip

Most drills are sharpened such that a = 118 deg, so this simplifies to:

x = 0.300 * d

[Jasonb]

Easier to just touch the drill tip on the work, zero your depth scale and just drill to the required depth shown on drawing.

[J.L.]

Thanks for all the input gentlemen.

Marv, where do you come up with that math? That just flew over my head. 

The deed is done. Jason and Chris, both your options were used; undersized starter holes, milling slot undersized, then on one side only to expand.

I finished the 1/8" slots with a 1/8" slotting drill (two flute).

Now for the steam passages...


 

[crueby]

Looks great - nice crisp long edges, that is very important for the valves.

    

[J.L.]

Thanks Chris.

I spent quite a bit of time today making a brass flange for the outlet pipe from scratch.

I assume such a deep void was cast in the cylinder on both sides to save metal. Obviously, a hole was intended to be drilled and threaded right into the cylinder.

But Ernest Winter casually mentioned and I quote;

   “If a more authentic flanged joint is preferred, the side of the cylinder casting will need to be milled flat [for the exhaust pipe flange]”.

Interesting.

The exhaust hole has to be fairly low to meet the bottom of the 5/8" centre port. There is no metal for such a flange as is seen in the third photo.

So this large void will have to be filled with epoxy resin and allowed to harden in layers to bring a surface flush with the cylinder wall.  Hopefully, it will hold threads for the flange and the brass bands for the cladding.

I see this as a casting oversight. More meat should have been left on the top surface for an exhaust flange option.
 

[wagnmkr]

John, in my mind, JB weld would be much stronger and it is meant to be drilled and threaded.

Tom

[Ramon Wilson]

Hi John - up early and waiting for my mate before our weekly jaunt round the common.

Just caught up with your latest progress - my word you have been busy 

Re the valve outlet fitting I can see what you mean by the casting being deep but you do not have to have the outlet hole meeting the exhaust cavity at the very bottom - indeed as long as it *does not break the valve surface it can be as close to that surface as you want* - doing that may give you the area you need to bolt your flange on. Failing that I would agree with Tom on using JB Weld. If you do (and I would advise using the standard type and not the fast set type) let it sit for an hour or so after mixing before applying it to the cylinder. JB tends to be a bit runny and will slump if applied straight away. You can also mix colloidal silica (readily available from epoxy resin suppliers) to thicken it to 'stay where it is' without affecting it's strength.

If you are going to machine and drill and tap it I would leave it a good two days to really harden out before doing so.

Hope that's of use to you - stunning work so far, keep it coming 

Regards - Tug

Edit - let me rephrase that. *If the outlet flange you have made does not break the valve face line then you can move your outlet flange toward that face as close as you want.* That may give you a wider cast area to D/T for the flange

[J.L.]

Hi Tom.

JB Weld it is. And thanks for the tip Tug on just the standard type and letting it cure well.

Tug, I know what you are saying about mounting the valve higher on that sharp 'v' face. It would let the two stud holes on either side of the boss see metal, but since I'm going to clad the cylinder, a clean straight edge will be a good starting point for the first board - rather than having to shape wood around that deep void. A deeper hole will also stay away from those 1/8" steam passage holes coming up from the edges of the cylinder to their ports.

Good thought nevertheless Tug. Thanks.

Cheers...John

[john mills]

hi john
The ports look good ,you worked out how to machine them .
For the flange i would drill and tap the hole as for a screwed in pipe but turned the bose you have on the flange like a sleeve with a step ,bored the flange with a plain hole then screwed the sleeve to the cylinder holding the flange in position. the flange can have holes drilled and tapped for studs with nuts as required . Then space can be filled as required to support the lagging.

[J.L.]

Thanks John.
I'll stay on track with filling the void. The first layer is hardening nicely. The 1/4" exhaust hole has also been drilled. No broken drill! Let's hope I'm that lucky when the steam passages are bored.

I don't want to disturb things until several operations are complete with the cylinder in the vice now. I have to purchase new JB Weld anyway. So the milling machine is out of action for other operations for awhile.

I'm happy with that. I think I'll put shingles on half of the boiler roof! 

[Jasonb]

John, you may still have problems when drilling the stud holes as the drill will want to swerve off into the softer JBWeld, A dummy pair of studs and a screwed in flange like John suggests may be better.

[J.L.]

Jason, you make a good point about the drill wandering into the softer material. The dummy studs and nut make perfect sense, but I am not yet sure how to attach the flange. The 1/4" hole in the valve face of the cylinder would have to opened up to take a 5/16" shouldered hole. Then a smooth sleeve could be inserted into that smooth hole and extended proud of the milled face 1/16" to centre the threaded 5/16" NPT threaded hole in the flange.

I am working with tapered MTP Threads here. Only straight threads would work as John suggested.

We've got time to think this one through. The flange is basically cosmetic. The flange could simply be CA glued in place with its dummy fasteners. The sleeve would be necessary though for that.

[J.L.]

Hi John,
Thanks for the suggestion of threading into the cast iron. Unfortunately, it's difficult to use tapered tap and dies to do the job. If the threads were 5/16" straight, you could run right through the flange into the iron.

But you have given me the idea of creating a smooth shoulder extending out of the iron and catching the edge of the tapered flange threads. The wider tapered threads at the top of the flange would not be affected by the untrusion of the sleeve at the bottom portion of the hole. Threaded pipes lock up long before reaching the bottom of the fixture.

So I guess we are gluing the flange onto the sleeve extending out of the machined face.

Love these challenges John. It's what makes the craft fun.

Thanks again,
John