Author Topic: High Pressure Steam Table Engine  (Read 25427 times)

Offline crueby

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Re: High Pressure Steam Table Engine
« Reply #15 on: May 26, 2022, 03:26:54 PM »
Looking great Jo!

The one time I cut flutes in a column, I didn't have a ball cutter, so I took a normal square end end mill the same size, and tilted the mill head over 45 degrees, and ran the columns under it with the part centered under the cutter. Ran the cuts so the side of the cutter was touching the part first, and the tip dragging along behind. The angled end cut a nice rounded shape just like a ball end mill would.
 :popcorn: :popcorn: :popcorn:

Online Jo

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Re: High Pressure Steam Table Engine
« Reply #16 on: May 26, 2022, 04:05:51 PM »
Thanks for that idea Chris I might need it  ;)

Jo
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Offline Jasonb

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Re: High Pressure Steam Table Engine
« Reply #17 on: May 26, 2022, 04:15:57 PM »
Another option if you want to keep the moths under wraps is to grind up a simple single point tool and use that to cut the grooves at the side of the column not the top a bit like gear cutting, would also save packing the tailstock to height and the cutting edge is moving a lot faster than the almost dead middle of a ball nose so should give a nice cut.

Did you drill with a standard ctr drill or one that gives a trumpet shaped hole? They are supposed to be better for this but I've not tried one.

Online Jo

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Re: High Pressure Steam Table Engine
« Reply #18 on: May 26, 2022, 04:27:53 PM »
Thanks for the idea Jason  :) . I think packing the tailstock up (cutting at the top) is going to be much easier than trying to offset it sidewise during the cut on the side in order to get the flutes parallel.

I only have standard centre drills.

Jo
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Offline Jasonb

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Re: High Pressure Steam Table Engine
« Reply #19 on: May 26, 2022, 05:05:11 PM »
There is an easy way, shout if you decide to go down the side cut route.

Offline Charles Lamont

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Re: High Pressure Steam Table Engine
« Reply #20 on: May 27, 2022, 03:04:44 PM »
Geometry/aesthetic question: do you mill the flutes parallel to the side, or make the cut depth slightly greater at the fat end to keep the lands between the flutes parallel?
« Last Edit: May 27, 2022, 04:45:56 PM by Charles Lamont »

Offline Jasonb

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Re: High Pressure Steam Table Engine
« Reply #21 on: May 27, 2022, 04:11:30 PM »
They should be slightly deeper at the bottom otherwise you end up with the bits inbetween getting too narrow. I'll dig out the formula later and I think I have some images showing how it's done. Also they do not have to be semi-circles you want say a 4mm dia cutter for a 3mm width flute so it's more of a scallop.

It's debatable if it would notice on a part this size and I'm sure whatever Jo does will be an improvement on the rather soft ill defined castings. I did it for the much larger Otto langen and if Jo gets round to doing her "big Willey" then that would probably need it.
« Last Edit: May 27, 2022, 04:44:15 PM by Jasonb »

Offline Jasonb

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Re: High Pressure Steam Table Engine
« Reply #22 on: May 27, 2022, 04:43:35 PM »
have a look at this and the next page, I drew one out in CAD

https://www.modelenginemaker.com/index.php/topic,7162.195.html

Offline crueby

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Re: High Pressure Steam Table Engine
« Reply #23 on: May 27, 2022, 04:50:37 PM »
have a look at this and the next page, I drew one out in CAD

https://www.modelenginemaker.com/index.php/topic,7162.195.html
Which post numbers? I am not seeing the column at that link, its a long thread to search through.

Online Jo

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Re: High Pressure Steam Table Engine
« Reply #24 on: May 27, 2022, 04:57:08 PM »
This one https://www.modelenginemaker.com/index.php/topic,7162.msg153641.html#msg153641  ::) Its the land width that should be kept a constant  ;)

Yes the groove is not a true semi-circle but elliptical which can also be achieved by cutting on the side of the cutter like Chris mentioned  :)

Jo
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Offline crueby

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Re: High Pressure Steam Table Engine
« Reply #25 on: May 27, 2022, 04:58:41 PM »
This one https://www.modelenginemaker.com/index.php/topic,7162.msg153641.html#msg153641  ::) Its the land width that should be kept a constant  ;)

Yes the groove is not a true semi-circle but elliptical which can also be achieved by cutting on the side of the cutter like Chris mentioned  :)

Jo
Excellent - thanks!

Offline Jasonb

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Re: High Pressure Steam Table Engine
« Reply #26 on: May 27, 2022, 05:17:42 PM »
The discussion of fluted columns runs for over two pages starting at or before the top of the one in my link

Jo's 18 flute one with a 2.4mm cutter


Offline Charles Lamont

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Re: High Pressure Steam Table Engine
« Reply #27 on: May 27, 2022, 10:28:20 PM »
The skewed cutter trick is an occasional lifesaver. I made this clack valve for an unusual direct mounting onto a boiler barrel (having a reinforcing piece inside).
Although the curved face is theoretically slightly eliptical, it bolted up as machined, with no fitting required. (It is not my workshop, and that ancient [Archdale?] mill has since been scrapped).

Offline ettingtonliam

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Re: High Pressure Steam Table Engine
« Reply #28 on: May 28, 2022, 02:54:51 PM »
For jobs like this, where the flutes are 'visual, and don't have to be geometrically accurate, I have simply taken an end mill of the right diameter and freehand ground the end to form a ball end mill. Even better if you can use a broken or blunt cutter, and make something useful from it!

Probably not an acceptable solution for you precision guys, but I'm from the 'coal board fitter' side of the spectrum!

Online Jo

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Re: High Pressure Steam Table Engine
« Reply #29 on: May 30, 2022, 02:44:08 PM »
Luckily I have found a 3mm ball nosed cutter so I am going ahead with that one  :)

I first jacked up the tailstock by half the difference in the taper diameter. Mounted the column in the dividing head chuck making sure to only hold it on a bit so to allow the piece to flex and checked the top cutting surface is flat:


 :)

Time for some dividing head calculations:

This dividing head is 40:1 and I need 18 flutes  :thinking:

18 times 40 = 720 so I need something divisible by  :facepalm: what am I up to if I use an 18 hole dividing plate then all I need is to move forward 40 holes = 2 full turns plus 4 holes. What could be easier  :ROFL: Off we go:

Start with a 0.1mm cut:


 :thinking: Looks like plenty to go but lets go round a bit...


The depth looks even:



That looks even, round the whole way:


A bit more depth and  :rant:  :wallbang:   :toilet_claw:


Don't you hate it when that happens   :Doh: I have just cut a spare/replacement in time for a strong coffee  :disappointed:

Jo


« Last Edit: July 27, 2023, 03:57:56 PM by Jo »
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