Here is a list of all the postings JA has made in our forums. Click on a thread name to jump to the thread.
|Thread: Why does everyone disagree with you|
I feel that this forum is a bit like the Wild West: There are few rules, almost anything goes, sometimes it is wise to keep your head down and you may get shot at. An awful lot of members have hidden pasts (the majority do not have a public profile).
Steveiegtr - A comment, I see that a lot of your posts are made in the late evening. I have found from experience that this is unwise.
Edited By JA on 27/01/2020 12:38:25
|Thread: Robot Wars|
If I believed in conspiracy theories I would suggest that it has something to do with "The cultural status of (future) engineers ..........."
Edited By JA on 22/01/2020 19:35:16
|Thread: Reamer specifications ?|
The coding on the reamer, such as H7, defines the expected tolerance that it would give. While this is of little interest to model engineers it is of great importance in manufacturing where interchangeability is a must.
I will give a simple description on how it works.
For example, we want a 10,00mm shaft which slides in a bush (a sliding fit is between a push fit and a nice rotating fit).
The established standard kindly gives a chart
which suggests a hole and shaft tolerance – H7 & g6 (upper case = hole, lower case = shaft). The number gives the machining process that will achieve the required tolerance with ease.
It shows that we should be able to achieve the tolerances by grinding, broaching, reaming, boring or tuning. Finally we need the tolerances and required dimensions.
The hole requires a tolerance of 0 to +18 μm and the shaft -6 to -17 μm. It follows that the dimensions are 10,000 to 10,018 mm for the hole and 9,983 to 9,994 mm for the shaft. A 10mm reamer marked H7 should give us the correct hole dimension.
Fits and limits can get horribly complex and, unless one’s interest was manufacturing engineering, there were usually better things to do.
|Thread: Lathes as bling!|
I don't understand how a Hardinge lathe ended up in a railway workshop. These were bought by the likes of the Atomic Energy Research Centre and used in clean tool rooms.
By Prestwich in Tottenham, London (my play ground, bomb sites, as a kid)?
Edited By JA on 18/01/2020 19:20:33
Edited By JA on 18/01/2020 19:21:34
At school we are lied to and spend the rest of our lives messed up.
I strongly believe that history should not be tought to those under sixteen.
It is rather nice. Perhaps Boxford could copy it (I doubt it).
A bit of reverse bling.
I took this photograph as an ordinary member of the public visiting a heritage railway workshop.
Edited By JA on 18/01/2020 09:23:10
|Thread: Betelgeuse in Orion|
I will watch, I have yet to see a supernova. I guess it is one up from a solar total eclipse which I have seen.
|Thread: Too ambitious or achievable?|
The Kiwi was designed by Edgar Westbury. At the time he was the civilian boss of the apprentice and officer training workshop at RAF Cranwell.
I have just seen Hopper's posting. Simple Stuart steam engines are a good start
Edited By JA on 17/01/2020 20:05:33
|Thread: Lathes as bling!|
The fact that many threads on lathes degenerate to the old argument about the merits of Myford and Chinese lathes has got me thinking.
The amateur lathe market, unsurprising in the past, has been dominated by cheap new products or questionable second hand items. One feels there should be a market for a good modern lathe. Obviously such a lathe will cost more.
When I go to Slimbridge to look at the ducks there are people wandering about the place carrying £10,000+ of camera equipment around their necks so I feel the money is there. OK, I know it is bling. Perhaps we should do the same!
|Thread: Myford super 7|
I cannot improve on Dave's excellent reply.
Just a suggestion - experiment and keep notes on what you have done. That is what industry does for metals such as high temperature alloys.
|Thread: Musings on taps|
A - Not worried.
B - I usually grind off the point on plugs. The last time I broke a tap was doing this.
C - I try to buy single taps from suppliers I trust.
D - I have tapped stainless steel without difficulty. I realise there are many different stainless steels but, I am told, you must cut and not rub. If you want real difficulties try Aluminium Bronze.
E - With mild steel, yes. I do not tap using power and consider 3/8" BSF very large!
F - I have not met this one - see C
G - That is what you pay for.
|Thread: Myford super 7|
And even hold hexagonal bar.
|Thread: Driving Small Taps|
Both wrenches are also used in the lathe with a centre in tailstock as a guide.
I have used the above to tap 12BA holes into steel and have yet to break a tap.
Edited By JA on 16/01/2020 13:22:21
Edited By JA on 16/01/2020 13:22:55
Edited By JA on 16/01/2020 13:25:02
Edited By JA on 16/01/2020 13:25:28
|Thread: Myford super 7|
My three jaw chuck never ran very true, around +/-0.004". I did not use it often and tolerated it when I did.
About 7 years ago I decided to do something about it and bought another backplate. This did not fit onto the lathe spindle. My other chucks (the existing three jaw, 2 four jaw, catch plate, big faceplate and adaptor for Myford collets) had not problems. The inside diameter of the thread in the backplate was correct but the thread crest appeared to have too much flat on it. Measurements convinced me that another 0.003" to 0.004" needed to be taken off the flank of the thread. An easy afternoon job: I accurately mount the backplate, face to face, in the big four jaw chuck, pick up the thread with an internal screw cutting tool and remove the excess metal.
One little problem, my lathe is Imperial with 1/8" lead screw while the thread is M42.5 x 2mm. To get over this little difficulty I bought a gear set from John Stephenson (late of this forum) that fitted to the quadrant in the gear train to the gearbox. I am sure that this would have given an approximate Metric thread but the assembly fouled the casing of the lathe. Therefore everything was put aside.
Sometime later I bought the Myford conversion kit for cutting Metric threads, very expensive but justified since I had, and still have, a project requiring it. Looking at all the bits I realised that the conversion is not a quick job and you only do it if you have to. Since I did not have to the kit is on the shelf waiting for its intended use.
Last year I felt a little ashamed of all this, recognising that the undersize thread was a one off and its production batch was years ago, I bought another new backplate. It did not fit.
And this is for a chuck I don't use or need. Everything a three jaw chuck can do can be done in a four jaw chuck. A three jaw chuck only wins in the
So the unusable three jaw chuck sits on the back of the shelf, unloved.
Whether the security screw is tightened or not makes a small but measurable difference to the true running of the chuck.
Edited By JA on 15/01/2020 08:54:28
To be posted in the morning. Never post anything late at night!
Edited By JA on 14/01/2020 23:45:36
Edited By JA on 14/01/2020 23:46:53
Myford, the original firm, supplied a 160mm four jaw chuck with the lathe when I bought it in late 2010. The chuck back plate is locked to the spindle by a grub screw mating with a annular grove. This was not the case with my earlier Super 7 which had an unlocked chuck. I have never had a chuck come loose but I have been very aware that it could happen.
I see that the present firm only supply 100 & 125mm three jaw chucks according to their web site. I find the omission of an independent four jaw chuck surprising. I not longer have a useable three jaw chuck - for various reasons it has lost its back plate. Other than collets the big four jaw chuck is the chuck of choice.
When I bought my lathe the factory warned against using the clutch if you were running a largish chuck at high speed. In such cases the chuck should be run up to speed with the clutch engaged.
I have not used such a configuration (and I do not intend to) but I think we are talking about 2000+rpm and a large four jaw chuck.
|Thread: Only for Myford lathes|
The one thing I done not like is that the top slide clashes with the tail stock when set at 0 degrees.
I bought my third Myford, the first new one, with an inheritance about five months before the firm was sold in 2011. Since I had the money the lathe has all the bells and whistles - hardened bed, gear box, inverter supply to the motor and a DRO. I think I have made good use of the lathe and it has not let me down at all. The one problem with having the factory fitted DRO is that you loose the use of the taper turning attachment.
While Dave's list is true for early and middle age machines, a lot of the criticisms had disappeared with the later lathes (particularly if you spent the money).
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