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Member postings for Oldpeter

Here is a list of all the postings Oldpeter has made in our forums. Click on a thread name to jump to the thread.

Thread: Drawing Quality
28/10/2011 15:56:41
Thanks for the encouragement to all who replied to olpeter's posting.Much appreciated.
 
25/10/2011 16:50:11
I got hold of a brand new "mini-lathe" with 2/3 HP motor and 18" between centres - 70 mm radius swing - Was that too small for steam engines of 1" bore? (Still have worn out 1921- Packard lathe for rough work.)
 
Posted by Richard Parsons on 25/10/2011 15:07:13:

Oldpeter
 
Mini lathes are I am afraid very light in their construction. They are really clock maker’s lathes. I after I bolted and gluer (with Araldite) my Unimat SL The three rules are reinforce the rigidity, sharp tools and light cuts.
I always measure after each cut and if the resulting diameter is not correct repeat the cut at the same settings..

25/10/2011 11:05:58
Thank you for the advice and encouragement - My problem is not that I have too little information - I have too much info and I need practical advice - I do NOT have a CNC lathe, only a minilathe. I have read Bradbury's workshop technology part one and they are on about surface finish 1 to 2 RA and better, but although it is there you can't measure it so it is pure theory - In practice you get feed marks which you can see but can't actually measure. With a travelling steady I hope to reduce the middle hump. With a dial micrometer I can measure differences but not the thickness - I am also reminded to be thinking 3 times, measure twice and cut once. I can't justify getting go - no go gauges as I am not mass producing.
So what must I be looking at - how far do I need to go to get a practical solution to accurate cutting? I don't want to cut ten times and throw it all away. Is lapping or honing
the answer once you are close and then trial fitting? What equipment do you need for lapping and honing?
In practice do I have to aim for slightly tight and then run it in - or do I rely on steam oil or graphite rings to close the gaps? The books do not tell you these things!
 
24/10/2011 10:56:00
OK so you have redrawn your project accurately on your favorite CAD program. How do you go about machining to the specification on your drawing? Let me start with a shaft and a bearing of lets say 6 mm. (Remember I am a beginner and leave the fag packets out of it.)
Do you do the bearing first and then the shaft and then making the shaft slightly over- size before starting to use emery paper to get to the exact size before doing trial fits between shaft and bearing or do you use measuring tools and if so which measuring tools? I believe if you can machine a shaft exactly 6mm and drill the bearing is exactly
6 mm you have an interference fit or press fit. In this case you want the shaft very slightly smaller than the bearing - how much - by being just able to push it through or by it just falling out on it's own weight??
I do not know how to machine or drill to exactly 6 mm!! ( the whole length )
What is the standard practice? Don't tell me you can do it with machining on a lathe with sharp tools - you end up either under or over size. It is quite difficult for me doing exact measuring as well with a vernier callipre - do you take the average reading of several different places on your work - it seems to me you get different thicknesses at the start and the end of the cut. Side cutting or face cutting? How do you do buffing or lapping and what exactly is it and how do you do it accurately? I did buy a new mini lathe as my old reconditioned 1921 Packard lathe is fit for rough machining only. Help advice and tips on starting out will be welcomed. I am interested to eventually build a small steam engine.
Thread: Sealing boiler fittings
23/10/2011 10:20:35
On taking my second hand boiler fittings off, I discovered aluminium washers were used, corroding the threads to blazes - will have to replace the fittings with larger ones, Drlling it out and re-tap, but I am not sure in what threads (standard and tpi) the fittings are available - Any suggestions. I have an old Stuart Turner 504 boiler. Also very difficult
(? impossible) to find the correct size water gauge or do I have to use one with one free floating end?
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