Member postings for Rod Renshaw

So, how do you make a ventilator?

To me, who knows nothing about the subject, it sounds like you need some tubing and valves, an air pump, some electronics , some switches and pots to control things and a case to hold it all together.

So, a steam engine builder, a hot -air engine builder, an Aurdino enthusiast, someone who has fitted a VFD to his lathe, anyone who has made a toolbox, and a martinet to organise things.

We have all the skills on this forum!

I guess there must be more to it than that, but they are asking JCB to make them, and it seems a long way from an earth mover to medical equipment, so perhaps it's not rocket science.

Not entirely seriously

Rod

Hi all

I have an arrangement using an Arrand ball bearing spindle and it works quite well for small holes up to about 4 mm.

For larger holes it's worth reflecting that it takes the same power to drill a hole in the lathe as it does in a drill press, and quite a large motor is needed to drill holes of (say) 6 mm diameter or more, especially in steel. Anything much less than 1/4 HP may seem underpowered and very slow, and 1/2 HP is much better.

Rod

Hi again

My reference above to "Martin's last post" was to his Goodnight nurse post, not the Bitcoin one. , he must have been typing again as I was typing.

Rod

At last! - some sense in the last 3 or 4 posts.

When younger I was told that it was not considered polite to discuss politics or religion at the dinner table as this would cause arguments that would not lead anywhere - perhaps we should add climate change to the list.

I personally am convinced it's happening, it does not take a degree in physics to read a thermometer and weather stations and geographers around the world agree the world is warming up. If it's not human activity which is causing this rapid change then I see no other plausible alternative explanation and I agree with Martin's last post.

I am concerned that vested interests and a desire to continue living our usual lives may be acting to delay any effective remedial action until everyone can be convinced, and then it may be too late as some effects of warming, such as loss of albedo caused by ice cap melting may not be easy to reverse.

Rod

While Daniel is correct on one level, I am guessing that John restores older machines to become historical exhibits or museum pieces or something of that kind, and that they will not be used in any aggressive role in their new lives. So perhaps it's not a bad thing that they are preserved as examples of man's follies.

In any event Daniel's post does not seem calculated to welcome John to the forum which is a pity as we usually welcome all new members whatever kind of work they do, on whatever kind of scale and whatever their background or level of expertise.

So, John, welcome to the forum, you will find it generally welcoming, helpful and constructive, though we have a few grumpy old sods who can't help getting on their high horses and pontificating at great length, though even they can be informative and even amusing at times.

Rod

+1 for views of NW 1 but I find it also pays to think of the total time that the job may take as being made up of the time to change the tool and also the time taken to make the cut. For smallish work requiring several tool changes then I use a QCTP and find it adequate and quick. But the QCTP overhangs the side of the topslide and lacks the rigidity needed to take heavy cuts. I wonder if the real limitation with using the QCTP is the topslide itself - which tilts sideways under load because of the overhang.

So for biggish work requiring a lot of metal to be removed on a smallish (Myford) lathe then I switch to an earlier idea and find the taken to switch is more than compensated for by the ability to take much.heavier cuts.

My earlier system is based on the "Simple Toolholders" advocated by Dr Robert Rose in a short series of articles in ME. Vol 138 (1972). These toolholders are just short lengths of BMS with a slot milled in one side to hold a HSS toolbit. Imagine one side of a 4 way toolpost "detached" as it were, from it's fellows, and with very short screws. The article advocates one makes a holder for each tool likely to be used. The toolbits are held in the holders, complete with their dedicated packing, by short grub screws. The holders are held on the topslide by the "Clog" toolpost supplied with the lathe. The holders are quick and easy to make, cost virtually nothing and, because they are held almost centrally on the topslide, they are very rigid and make heavy cuts easy. Considering the simplicity and cheapness, I think this is a good system which could easily be adapted to holding tipped tools.

Not everyone will have access to the articles but if they are available, they are well worth reading, perhaps Neil could reprint them.

Rod

Hi

I faced a similar problem a few years ago and solved it by grinding tapers on 2 woodworkers flatbits of suitable sizes. I think the larger one was for cutting a 5/8 " diameter hole but can't really remember.

The steel of which these bits are made is just a little too hard to file easily but it grinds easily, the degree of accuracy needed is not high and I did the job on my off-hand grinder. If you make the new sloping edges each slightly convex then the hole grips at the top and bottom of the tool taper so the tools are held securely. I agree about the lubricant, which also helps with rust prevention.

Give each edge a little back clearance for easier cutting but in practice the detail does not seem to matter much, it will cut it's way into wood whatever the geometry of the edge. The bits are quite cheap and can be bought singly and can be retained for further use.

Christmas Greetings

Rod

LED batten lamps can be obtained from many retailers such as Screwfix and they resemble florescent tube batten lamp fittings and screw to the ceiling in the same way. They are easy to wire up (have Live, Neutral and Earth terminals), they consume little power and they start instantly and give a bright white light. Highly recommended! The active elements cannot be replaced, ( so the makers say, but an expert DIYer may think differently) the whole fitting will need to be replaced in due course but they are supposed to last a long time, so may be "fit and forget" in a mature worker's shop.

Neil

That's always been my understanding . I have owned and used a Super 7 for over 40 years and have always only used oil. The instruction book only mentions oil. I think think the question has been raised on this forum before and the answer from everyone was "Only oil".

Rod

I have one these ( same as HasBeans, except mine has 1/16" graduations) and I prefer it to the handwheel. I can estimate a depth to about 1/64" which seems accurate enough for drilling holes. The standard Myford handwheel tailstock has no graduations on the handwheel and the depth has to be estimated from the 1/8" graduations on the barrel itself. The other advantages are that the taper in the barrel is very easy to clean out and one can use a drawbar to secure collets and turrets in the tailstock. I have made a "bumper out" from a length of 1/2" steel bar with a brass tip on one end and a simple, but weighty, steel handle on the other. I keep this loose in the tailstock barrel and I don't miss the self-eject facility. The same bumper out is also useful in the headstock.

Rod

Graham

Many thanks for the explanation.

Rod

Hi

I have not come across the word "urge" used in this context.

Can anyone explain please.

Fascinating modification, I feel sure George would approve.

Thanks

Rod

I was once shown a "writing hut" which the homeowner had built in his garden and which rotated to catch the sun on a home made lazy susan bearing. The bearing itself was made of 3 sheets of plywood each about 8 feet in diameter. The lower sheet apparently rested on the foundations and the upper sheet was secured to the base of the shed. The middle sheet had holes drilled in it in 3 (or possibly 4) concentric circles to act as a cage and children's glass marbles were used as ball bearings. I was told the bearings had indented the plywood a little in use, to make tracks in the upper and lower sheets of ply and that there was a "bolt" in the centre to form a centre bearing, the builder was not an engineer. I don't know what the shed weighed but it seemed strongly made and the owner was keen to demonstrate that the shed could be rotated with little effort even with 4 or so of his guests crowded into it.

it might be a bit homespun for a turntable but it does demonstrate what can be done with simple arrangements.

If the load on the turntable is 1,000 lb and there are (say) 200 marbles, it does not seem unreasonable to expect a marble to support 5 lb?

These felts are still available for Myford 7s.

I understand that you can make your own and that chiropody felt ,available on the web, is a good material to use.

Rod

Memory suggests that the chemical is alum, as used in cooking, but I can't remember the details. I seem to remember it takes quite a long time.

I am rather taken with SOD's explanation for how siphons work using the analogy of a chain being dragged over an edge by gravity. ( I am sure JAs explanation using maths will be correct but I don't have the maths to follow it)

If we assume SODs explanation is a good analogy then I don't see any problem about water having nearly no tensile strength- which may well be true in general but in this case the water is in a pipe. The water has to stay in an unbroken length within the pipe because any break would cause a vacuum in any gap that formed. and air pressure on the water at both ends of the pipe would not allow that to happen- so the water behaves as if it does have tensile strength.

There is a limit though. It is well known that a siphon will not work over a "lip" of over 30 feet or so because the atmospheric pressure will not support the water column, and this may limit the use of siphons in large civil engineering situations. I am not clear how, or indeed if, siphons work in a vacuum.

Rod

Small tumblers are used by collectors and polishers of pebbles and semi-precious stones, and these are readily available from specialised shops and on the net.

Hi Plasma

Is half a hemisphere a quarter sphere?

Rod

Hi Clive

Many thanks for your prompt and comprehensive reply to my question.

I just have to find one like yours now!

Even if I can't find an adjustable one, I now have an idea of the sensitivity I am looking for.

Thanks again.

Rod

Hi all

After reading many of the contributions to this thread I am thinking of buying a level to use for "leveling" my lathe, and also for setting work up on my mill.

There has been much input on this thread about the sensitivity needed for these tasks and I find myself confused by all the different "Units" quoted by manufacturers and advertisers.

There seem to be units based on angles such as degrees, minutes and seconds of arc, and also degrees and decimal fractions of a degree. Then there are units based on offsets, and here there are many different lengths of baseline and some use Imperial measures and some use Metric units.

So how sensitive does the level need to be? and can the answer be quoted in many units so that levels from different sources can be compared? It is almost as if we could do with a conversion table, anyone know of one?

Thanks to anyone who can clarify this.

Regards

Rod