Author Topic: Another Potty Horizontal Mill Engine  (Read 14601 times)

Offline Heffalump

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Re: Another Potty Horizontal Mill Engine
« Reply #30 on: May 21, 2015, 09:17:15 AM »
Large Face mills seem to work well as they're rigid. I've just got a fly cutter which is ok for a lot of stuff and probably a damn site cheaper. Face mill might be better at taking hard skin off castings. That 3mm port looks a lot bigger to me, probably a just the photo playing tricks with my eyes. Looking good.

Hi Nick,

I was thinking about having a go at making a fly cutter or fly bar to help with radii in the absence of a rotab. It would certainly make facing a lot easier for me.

Quote from: b.lindsey
A little time on a flat surface with some 320-400 grit paper will get rid of the swirl marks, just takes a little elbow grease. Will make for better sealing mating surfaces later on too. though I still use thin gaskets even so.

Looking good though...still following along here.

Bill

Thanks Bill, I'm going to get going with loads of finishing papers and things once I've finished all the ops on each part. But I won't go overboard until I've got a runner, then I'll probably strip down and get polishing.

 :)

Offline Heffalump

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Re: Another Potty Horizontal Mill Engine
« Reply #31 on: May 21, 2015, 04:51:29 PM »
Thinking about the surface roughness, I dug this out at work today:



And found that both types of milling, though they look quite difference, gave me an N6 surface





So I'm not too worried about that!

I realised I still needed two more M3 holes on what was to become the bottom face. So I viced up again and drilled those





And after much more tapping (I decided to make the 8 bolt holes M2.5 because my supplier didn't get back to me about a new M2 tap).



And I'm calling this part done until I get to the finishing stage.



The mushy bit where I got half a tap stuck in can be seen here. I'm just going to keep it as is and see how I go.

Thanks for looking  ;)

Online sco

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Re: Another Potty Horizontal Mill Engine
« Reply #32 on: May 21, 2015, 06:44:31 PM »
Looking good Jim ;-)

Simon.
Ars longa, vita brevis.

Offline NickG

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Re: Another Potty Horizontal Mill Engine
« Reply #33 on: May 21, 2015, 10:17:52 PM »
Definitely beneficial to lap the mating surface with the valve chest to get it to seal properly. If you're looking at surface finish I would have thought about N4 + is required there and if you milled the ends they could probably do with lapping too.

Offline Heffalump

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Re: Another Potty Horizontal Mill Engine
« Reply #34 on: May 21, 2015, 10:48:05 PM »
Thanks Simon  :)

Definitely beneficial to lap the mating surface with the valve chest to get it to seal properly. If you're looking at surface finish I would have thought about N4 + is required there and if you milled the ends they could probably do with lapping too.

I agree - I'll be finishing the part with very fine sanding and then lapping the mating surfaces together to get a good seal. If there's still some leakage I'll look at a thin gasket. Bearing in mind that my only other engine was a wobbler which ran but leaked like it was cool, so I'll just be happy to have an engine that works!

End caps tomorrow then!

 :cartwheel:

Offline b.lindsey

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Re: Another Potty Horizontal Mill Engine
« Reply #35 on: May 22, 2015, 12:33:51 AM »
Still looking good Heff. I am going to have to build one of these yet it seems :)

Bill

Offline Heffalump

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Re: Another Potty Horizontal Mill Engine
« Reply #36 on: May 26, 2015, 03:58:09 PM »
Thanks Bill. As the first real cylinder I've ever created I'm a bit biased towards this engine now.

I got the front end cylinder cap made today. There's a little fettling to be done tomorrow because it's currently blocking the steam port in the cylinder but that's a small facing op.

I started off with a nice blank and turned down two of my diameters.







A lot of hand cranking has given me quite a poor face finish, so I'm going to sort that out later with some emery and work on practicing some smooth cranking.

I flipped and turned the other side down to size



Then realised my mistake. I was going to have to use the mill at some point for my bolt circle and I'd turned away all my waste material! Oh well.. on we go.

I drilled through 4mm, then drilled blind for an M8 thread. I grabbed the wrong size drill bit so my thread is rather poor, but there's enough there to grab the part it's mating to, and I'll make sure I get it loctited in well. This does make me worry about the concentricity of the central hole in the packing gland later, so when I make that part I'll mate it to the cylinder end cap, possibly mate that to the cylinder, and drill it all in one so I can ensure that it's central.



I used a vee block in the mill vice. It left marks which I'll file out on the late I think. A small penance for not thinking ahead.



I drilled out clearance holes for the mounting bolts (forgot picture sorry!)

And here it is mounted to the cylinder.

Must try harder.



Thanks for looking :)

Offline b.lindsey

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Re: Another Potty Horizontal Mill Engine
« Reply #37 on: May 26, 2015, 11:57:19 PM »
Its all a learning process Heff, and you seem to be picking it up quickly...still looking  good.

Bill

Offline tinglett

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Re: Another Potty Horizontal Mill Engine
« Reply #38 on: May 27, 2015, 08:17:36 PM »
Then realised my mistake. I was going to have to use the mill at some point for my bolt circle and I'd turned away all my waste material! Oh well.. on we go.

I drilled for the bolts after making the cover, too.  I doubt if the waste material would have helped much if you left it on.  I simply put the cylinder in the mill vise, centered using the piston (you haven't made this yet, so a suitable rod representing the piston rod would have worked), and then drilled the 4 holes without an RT.  My holes were well placed, but not terribly accurate.  I'm not sure what went wrong...maybe I didn't account for backlash.  As it is, I need to rotate my cylinder covers until the holes align and then bolt them down.  But to the human eye you can't see this.

Looks like great progress today!

Todd

Offline Heffalump

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Re: Another Potty Horizontal Mill Engine
« Reply #39 on: May 28, 2015, 02:02:12 PM »
Then realised my mistake. I was going to have to use the mill at some point for my bolt circle and I'd turned away all my waste material! Oh well.. on we go.

I drilled for the bolts after making the cover, too.  I doubt if the waste material would have helped much if you left it on.  I simply put the cylinder in the mill vise, centered using the piston (you haven't made this yet, so a suitable rod representing the piston rod would have worked), and then drilled the 4 holes without an RT.  My holes were well placed, but not terribly accurate.  I'm not sure what went wrong...maybe I didn't account for backlash.  As it is, I need to rotate my cylinder covers until the holes align and then bolt them down.  But to the human eye you can't see this.

Looks like great progress today!

Todd

Hi Todd

Yes - I centered in the mill but then used a coordinate calulator to work out my PCD, really easy in this case, 12mm up, 12 down, 12 left, 12 right. Still though I'm the same as you, they will only line up in one orientation. I made the back end cap today and that's even worse, I had to widen the holes by .5mm but you can't tell when it's all together.

In retrospect I should have made the cylinder and caps all out of my 2" blank bar, drilled the holes before I parted the parts off individually, that way everything would have been bang on. We live and learn!

Jim

 

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