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Member postings for John Olsen

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

Thread: Adept and Super Adept Register
24/05/2019 04:50:57
Posted by David Standing 1 on 23/05/2019 18:21:40:
Posted by Neil Wyatt on 23/05/2019 17:09:10:
Posted by Brian Oldford on 23/05/2019 11:27:09:



Bugger that, that's what electric motors were invented for! devil

Beats pushing a file though, and more accurate too. Seems a bit spendy though, and missing the actual tool post.


Thread: Interesting??
24/05/2019 03:52:44
Posted by Chris Trice on 24/05/2019 01:33:44:
Posted by Neil Wyatt on 24/05/2019 00:38:16:

Approximately half the population are of below average intelligence.. most people think they are above average...


By definition, "exactly" half the population are below average intelligence. That's the definition of average.

Actually not so, this is only true if the population truly follows a normal distribution. If it does then the median will be the same as the mean. If the distribution is skewed, with say a very few ultra high intelligence people and then a lot of people just below the mean, then you would have more people below average than above. For example, if we had 100 people with an IQ of 99, and one with an IQ of 200, the mean would be 10100/101, or 100. 99 people would be below average and one would be above. That is an extreme somewhat contrived example but many things do not actually really fit a normal distribution, but they are often close enough for practical purposes, especially in large numbers of samples.

The median value is the one where half the population are above and half below. The mean, or average, is the sum of all the scores divided by the number of samples.


Thread: Unknown tool
23/05/2019 22:12:06

So whereabouts in NZ??? I'm in Cambridge myself....


Thread: The Chocolate Fireguard as designed by Mercedes Benz
20/05/2019 00:21:58

Maybe I can claim the record for longest non model engineering post for my "Aircraft General Discussion" thread at 1648 posts. (When I checked just now....)


05/05/2019 07:05:03

This advice may not be applicable to all types of machines...but on my three the vertical height gibbs get locked once the height has been adjusted. However, if the machine is getting a little worn, it might pay to adopt the following procedure.

First adjust the height to what you want. Next, adjust the table support at the front to bear on the slide. Now wind the table height adjustment down to put a little bit of load onto the table support. Then tighten up the gibb screws on the height adjustment to lock it in place. This ensures that the outer end of the table is positively supported rather than maybe having a bit of room to move up and down as the loads come on.

Many shapers do not have much provision for adjusting the Gibbs on the cross slide, so any wear here can be a bit of a problem to deal with. Not that I have ever needed to, mine all seem to be quite good, and since all of them would be well over fifty years old that is not too bad.


Thread: Anodising
05/05/2019 05:03:13

Hydrochloric acid is the one that will corrode all your tools. It is actually a gas at room temperature, so is normally encountered dissolved in water. Left in the workshop, a little will come out of solution and waft around your workshop attacking everything. Even the killed spirits version, Zinc Chloride, seems to do this. Best to keep the soldering flux in the woodshed rather than the workshop!

Also the various forms of Chlorine sold for swimming pools will attack things too.


Thread: Help on a Matador four stroke engine build please.
02/05/2019 01:58:44

I seem to recall that someone built a proper dynamometer for testing model aircraft engines, and it was described in I think Aeromodeller. Peter Chinn did most of the testing for Aeromodeller so I would guess he might have been involved.


Thread: Lathe Mill Combo setup
01/05/2019 05:31:48

Hi Owen,

There are other Kiwis on here, including myself. Quite possibly there might be someone near you...I would be happy to come and look at things with you if you are within a reasonable distance. Other than that, I agree with the suggestion to get a good book and have a read about things. The local library might even be able to find you something suitable. It does look like quite a good machine to have. Combined machines can be a bit of a pain, since if you want to turn something, it will be set up for milling, and vice versa of course. However, for starting out when you cannot afford both they can be very good.

John, in sunny Cambridge

Thread: A Unique Word?
27/04/2019 07:19:58

The difficulty is that the self constituted authorities are supposedly guided by usage. Usage is of course mostly determined by editors (like Neil?) who in case of doubt, tend to look up their dictionary before wielding the blue pencil. Also teachers tend to insist on dictionary spelling, hence the system has ended up locked into various nonsensical spellings, which can never be changed because those who would like to do so have no say in the system. So we are stuck with absurdities like through, rough, plough and so on, despite the fact that the advantage of our Arabic based letter system is supposed to be that the phonetic nature of spelling means that you can read and pronounce words that you have never previously seen.

Mississippi is not the word I was looking for....


26/04/2019 23:55:43

So what about a word with three pairs of doubled letters in a row? Can you think of one?


Thread: Eclipse magnetic table
25/04/2019 05:16:10

A magnet is subjected to a demagnetising force from its own magnetism. Older types of permanent magnet steel did not have a remanence as good a some of the more modern materials, so would gradually demagnetise themselves. Old magnetos quite often need remagnetising to get the proper performance. Providing a magnetic circuit reduces the demagnetising force seen by the magnet, which is why keepers are often used. In a motor or a magnetic chuck, there is effectively a keeper circuit provided, so the magnets will last longer if they are kept assembled. I would not have thought that disassembly for a short time would matter too much. The modern materials do have better performance, both in the initial strength and in their ability to retain it.


22/04/2019 22:33:09

Lathe tool shapes will work fine. The most useful general purpose general purpose tool is probably a V shape, eg grind the end to a V with some clearance each side, and grind a bit of top rake on top, then put a very small radius or flat on the V end. This is used for planing flat surfaces, and it will cut feeding either when you are planing down a surface, when you get to the far side, you add a little more cut and then reverse the direction of the table feed. A similar shape is sometimes used as a roughing cutter on a lathe, but they are not usually expected to cut in both directions.

But otherwise...a standard lathe type knife tool will cut into a corner, a parting type tool can cut slots and so on. Slots of course have all the usual problems like parting off. A narrow angle cutter is all that is needed to cut dovetails, along with a bit of thought about how to set the clapper box angle.


21/04/2019 23:13:22

First time I have seen one mounted on the wall!

That is a ten inch Alba just like mine, a very handy size of machine. I see you have a very solid looking vice with it too, you will find that useful.

I don't suppose you will have any desperate need to take the head off, but there is a trick to it if you do. You have to turn the head around so it is upside down.



Thread: Making Holes in Copper Sheet
19/04/2019 10:49:55

I would probably use a hole saw for the initial hole, still using the bits of ply as you intend. Ordinary drills are not always very good on sheet metal. Otherwise a step drill or a conecut would make a better job on sheet metal than a normal drill, but they can be a bit expensive if you don't already have one.. Using a boring tool, either a boring head in the mill if you have one, or boring in the lathe should be a good way to get the final size. Take it gently with all the work, copper can be a bit grabby at times.


Thread: Telescopic bore gauges
17/04/2019 01:32:52

Mine didn't come from Arc Euro, but are the same sort of thing. They can be a bit fiddly, there is a bit of a knack to it but I would expect to get a bore within about a thou of nominal with them. But then the internal mike I have for larger bores also can be a bit fiddly, and they are a lot more expensive.


Thread: Notre Dame
16/04/2019 23:56:32

Of course if we were really serious about feeding the hungry etc, we wouldn't be wasting our time posting on this site, we would be out digging in the garden to give the produce to the poor.

Not all resources can be usefully applied to any particular problem, eg the people who can rebuild the cathedral probably could not directly contribute to curing cancer.


Thread: Folding Bike design & build
10/04/2019 01:15:49

My wife and I took a couple of Dahon folding bikes on a world tour last year, which meant they had to fit into a standard airline check in bag size. That means 1580mm max total dimensions of the bag, and under 23 kg. So small bikes are of interest, since the trip was successful enough that we would love to do the same sort of thing again. This looks like a promising design, but I would echo the question someone asked above, what is the gearing like. It is hard to get a high enough top gear with small wheels. Not that you are going to want to go extremely Dahon has the 16 inch wheels and an 8 speed derailleur. The bottom gear is plenty low enough, the top could be a little higher but it is really hard to do that since you need a larger front sprocket. It has been done but they are hard to get, I might have to make one. The gear hub inside the back wheel is a good idea, again provided you can manage to source something suitable.

The other thing I would suggest thinking about is a carrier of some sort. My wife's Dahon came with one and it does not significantly affect the folded size. I had to buy and fit one for mine, which meant a bit of modification on the milling machine, but again it can be left on when folded and still fit the airline bag. I did fit it using quick release fasteners so that it can be taken off easily. Even if you do not plan airline travel, one of the good uses for a folding bike is trips to the shops from either a small apartment or even a caravan or campervan. (US RV) You may not need (or want!) to carry a lot of stuff but it is a handy thing to be able to do. We were able to fold down the big bag once the bike was out and strap it on the little carrier, wear the carry on, and bicycle to our bed and breakfast places.

The Dahons are around the 11 or 12 kg mark, which leaves a bit of extra available in the bag to carry clothes etc. Between that and our carry on bags, we were able to travel for two months quite comfortably. Of course there are little expedients to keep the weight of the bags down, like wearing the camera and keeping the lenses in my pockets.

Bikes are a bit frustrating, when you think that the 12 kg or so of mostly aluminium should be able to pack down into under 30 litres or so, if only there was a simple way to do that. Well, we could pack it down OK by melting it, but getting it unpacked would be more of a challenge.


Thread: ST #5A Reverse Gear
06/04/2019 20:42:26

Some of the Stuart engines use a rod to retain the reversing handle in the desired position, It attaches to (with a pivot) one corner of the valve chest and has a screw with a cross hole in it to grip on it at the reversing lever, and a small knob on the end to stop the reversing lever going too far. An alternative arrangement would use an arm with a slot in it.


Thread: Stress Relieving Rolled Mild Steel
05/04/2019 10:33:49

I would get out the propane torch and heat it up to a good red heat, keep it there for a while, and then let it cool as slowly as possible. A few chunks of firebricks around it to make a rudimentary furnace would help keep the drafts off. There will be some scale but not as much as with the old way of putting it in the embers of the fire overnight. There is very little danger of accidently getting it too hot, you won't melt it with anything you are likely to have at home.

If you don't have a propane torch, it is a really worthwhile thing to acquire, since you can also use it to harden bits of silver steel, or drill rod if you like. (or gauge plate.)


Thread: shaper machine unknown accessory
04/04/2019 04:54:05

I think Jordi has it right, it is for adjusting the stroke. I will also guess that it is not a manufacturers accessory, but something that has been made by a former owner. It is not that a precise adjustment of the stroke is all that important, it is that it can take a bit of to and fro to get the stroke anything like, and while you are doing it your hands are inside the machine, just waiting for someone to bump the power switch and put you in a world of pain.

Some shapers are easy to 18 inch Alba has the screw and bevel gears inside the bull wheel, so it can all be done from the operators side. My 6 inch Ammco does not, but it is a small machine, and it is easy to get the position right, you get the slotted arm in the vertical position and the crank pin will slide up and down easily and stay in the right position while you lock it up. My 10 inch Alba has the same arrangement, but it is not so easy to get it adjusted to a good position, it fights a bit and the rather small door opening gets in the way. So it is easy to see that someone might have decided that a more sophisticated way of adjusting the stroke was desirable.


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