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Thread: Machining setup, thoughts needed
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11th Aug 2018, 07:50 AM #16Most Valued Member
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Hi CW
the only problem is that the hole is nowhere near concentric with the outside of the casting plus with the wear that is already there makes it nearly impossible to know the original position of the hole relative to the outside of the casting. I'm hoping that by spinning it in the lathe I may be able to visualise it but I need to make sure I have the bore parallel with the lathe spindle first (or as good as I can get it).
Phil
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11th Aug 2018, 08:21 AM #17Philomath in training
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I don't think that is expressing it quite right - you want the axis of the two bores to intersect at 90 degrees. I would hope that it was machined that way originally, but you can't make that assumption that it is correct now - it may have worn eccentrically to the axis or even drilled/ bored slightly off originally.
I've been thinking a lot on how to set this up over the last few days. At the moment I'm leaning towards a mandrel through the main bore (that is, the top of the T) that sits in V blocks. The V blocks need to be placed on the face plate so that axis of the mandrel intersects the lathe axis. The bore of concern (the upright of the T) then needs to be positioned so the 'true' end diameter is on the lathe axis. That way, even if the bore has worn off axis (or was not there in the first place), any boring operation will restore that. To locate that end diameter, I'm thinking that a spider running in a fixed steady may be the way to go. Provided that the axis of the spider is on the axis of the lathe, adjusting the part in the spider to be central should then also get the end of the bore central to the spindle axis.
On a mill I would still use V blocks and a mandrel but attach the end diameter to an angle plate to secure it.
My thoughts anyway.
Michael
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11th Aug 2018, 09:22 AM #18Most Valued Member
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Gees I agonized over that. I knew it wasn't right. 'In line with the lathe spindle axis would have been better'.
The V blocks need to be placed on the face plate so that axis of the mandrel intersects the lathe axis.
I'm thinking that a spider running in a fixed steady may be the way to go.
Provided that the axis of the spider is on the axis of the lathe, adjusting the part in the spider to be central should then also get the end of the bore central to the spindle axis.
Hope I have this correct.
I'm glad I'm doing this as pretty much every pickering is worn through this bore and invariably need attention.
It'll be great if I can get this right.
Phil
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11th Aug 2018, 09:26 AM #19Most Valued Member
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Something like this Michael.
I just need a nice plate to lay across the top and dial that.
Phil
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11th Aug 2018, 09:53 AM #20Philomath in training
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I'd suggest (and others may have better ideas) attaching the V blocks* to a strip of material to keep them in line and then using a central hole (that is, a hole that sits along the axis of the Vs. As the part is asymmetric, it does not have to sit equidistant from the Vs) in either the strip or a piece of rod resting in the V's to line up.
*I say V blocks but there is no reason (within reason) you could not just get some angle iron and RHS and weld up a fixture, especially if you think that others may want this done so there is a future need. Provided it is accurately positioned, it would work. That also lets you incorporate locating and clamping features too which may make things easier
Yep. That was my thinking
MichaelLast edited by Michael G; 11th Aug 2018 at 10:12 AM. Reason: clarified
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11th Aug 2018, 11:17 AM #21
Shame it could not be set up and bored in long/line bore fashion. Of course supporting the end of the boring bar would not be possible.
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11th Aug 2018, 11:59 AM #22Most Valued Member
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Aint that the truth Ray. I've done that on many occasions in the past and it would have been ideal in this situation as I am going to have to machine a bronze bush to press into the bore and I'll need the accuracy. I'm not sure yet whether I will do the old big end small end method or undercut the middle section to create less drag when pressing it in.
Now, in my head is a solution to this problem using Michaels setup but with a little addendum. This will take me a few days to fabricate and machine so bear with me.
If it works...
Phil
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17th Aug 2018, 02:02 PM #23Golden Member
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Hi Phil.
Did you solve the problem yet? Lester Bowman on PM has just posted a description and photos of a similar governor which he has overhauled:
https://www.practicalmachinist.com/v...04/index2.html
Post number 57
He says he replaced everything except the original casting and the pulley. He did not specifically say he had rebored the tube to accept a new shaft, but if he did he might be a source of further ideas if you do get stuck.
By the way, have you ever come across a porcupine boiler, as described on the first page of the above thread? I cannot visualise how water circulation could take place, though another poster in the thread (post 52), makes some suggestions. I would imagine that the closed tubes, and probably the whole boiler, would have a relatively short life.
Regards,
Frank.
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19th Aug 2018, 08:55 AM #24Most Valued Member
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Hi Frank
what a great read, I almost forgot what I went over there for.
Pity there isn't a rebuild thread for the governor though I am guessing he was lucky enough to be able to ream out the bore and make a new shaft.
I have to say I have never seen a "porcupine" boiler before though I do understand the principle as bad as the design is.
Every boiler has what is known as the 'vital part' which is basically that part which is affected from the heat of the hot gasses from the furnace and will be exposed first if the water level should recede. This is generally what causes a boiler to explode. I would class this boiler as a 'water tube' boiler so the explosion would be almost insignificant.
I noticed that the top couple of rows of quills had caps on indicating (to me) they had been replaced with out the facilities to swage the ends like the other quills so they screwed caps on.
I wouldn't mind betting the boiler ran a bit short on water at some stage. Either that or they were replaced due to the gasses being a lot cooler at that stage which would be inducive to corrosion both external and internal with bad circulation.
I would reckon that they relied on 'thermosyph', a lot, for that boiler to work. Basically this means that the hotter the water gets the lighter it becomes and will work its way upwards drawing cooler water in behind it. The quills just create a larger heating surface to boil the water
Certainly an interesting boiler and I may certainly be totally wrong.
Phil
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20th Sep 2018, 10:14 AM #25Most Valued Member
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Hi all,
time for an update. I went with MichaelG's idea of the V block mount and it just seemed to grow from there.
DO NOT look at the welds...please, a welder I'm not.
If anyone spots any glaring mistakes or improvements please don't hesitate to say.
Phil
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20th Sep 2018, 10:41 AM #26Most Valued Member
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Nothing wrong with those welds, (once they're ground back ) Phil. A good excuse is old tired eyes, well that's mine anyway!!!
Like the V block idea, THANKS.
The only comment I can think of, would be to tap several holes so that there is a bit more holding the "V" blocks on the faceplate.
Kryn
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20th Sep 2018, 11:03 AM #27Most Valued Member
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20th Sep 2018, 11:15 AM #28Most Valued Member
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The last of the pics.
Any suggestions are more than welcome before I begin machining.
Phil
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20th Sep 2018, 11:22 AM #29Most Valued Member
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20th Sep 2018, 12:17 PM #30Most Valued Member
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Just wondering if this thread should be moved to a more appropriate place...be nice
Phil
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