Member postings for gerry madden

I want to make another measuring probe like the ones in the picture below.

My first attempt to simply turn one up was ok but highlighted the need for the tip to be very spherical. So for Mk2 I want to put a hole bearing ball (1/8~1/4" and glue in on to the turned body. The hardness and smoothness of the ball will be advantageous also.

Just looking for some guidance or comments on the following:-

1. I assume I'll need a carbide drill. With my speed limited to 3000RPM approximately how long should I expect this to take ? 5 mins or 50 mins ?

2. I will probably need to grind a small flat on it before drilling, but rather than do this off-hand then have the challenge of then re-holding the ball with flat in the right place and at right-angles to the drill, would it be better to attempt mill a flat with a carbide mill ?. I just cant see this going well ...... actually I have just realised, I have a diamond wheel I can mount in the mill so forget this one !

3. ... or should I forget carbide and just go for a small diamond encrusted drill?

I have seen torroidal shaped rubies for sale for this purpose but perhaps that can wait for Mk3, in the event that Mk2 is still lacking in some way.

Gerry

Thanks all for your comments and advice. The sheet I was 'sold' did have a mahogany skin which convinced me it was genuine, but on the quiet was always concerned by the lack of any marking confirming the fact. I will have to buy another sheet, this time from a 'proper' supplier and look for some some marking on the product. Even then I will do a test sample !

It's the second box I have made. My first one did get occupied successfully. But I used standard ply and after two years the bottom had dropped out and the rest was in a sorry state. I plan to put a camera in the 2nd box so want to make it survive. I've already decided the first one is going to finish its life as yet more garage shelving.

Gerry

A couple of years ago I ordered a sheet of 12mm marine ply for a tawny owl nest box from a well known building materials supplier. I have only just got around to making the damn thing . After completing the carcass it I put it outside to let the preservative dry. It rained gently for a couple of days which I didn't think would be a problem. Today I went to finish it and found the ply was delaminating badly in several areas !

This makes me think that this material was not marine ply. There was no marking on the sheet to suggest it was or wasn't. Should there be, and how would I know that I have the proper stuff next time ?

Gerry

Update - I took a punt on a Femi 728xl. Excellent delivery and a sensible design. But as so often these days, a good product is let down by a few quality issues. For any one else buying one here's what I found.

1) Drive pulley

As it was cold outside I took the liberty of running it in on the dining room floor. Im pleased I did because after a few moments I noticed crumbs of rubber dropping out from the blade box. Dismantling showed that the head of the main hinge bolt was rubbing against the edge of the drive pully. The bolt head was standing proud because someone had stuck a way too course star-washer under it. What made it worse was that there was already a slot in the casting to prevent rotation of the bolt and the round star-washer didn't fit the slot. The remedy was simple. I removed the bolt cleaned up the slot with a die grinder. I then found a thinner star-washer and ground flats onto it so that both the washer and the bolt head would fitted snuggly in the slot.

2) Vice

When I turned the handle it oscillated between tight and loose with each rotation and the moveable jaw swashed in sympathy with it. This suggested a bend in the shaft. Sure enough, when it was all in pieces this was found to be the case. However it wasn't so much the main shaft that was bent, it was the stud on the end with the M6 thread that was out of line with the main shaft. Some careful re-bending and machining sorted this.

What was somewhat surprising was that the vice unit had been carefully shimmed up with shimming washers so that is didn't distort when bolted to the non-flat frame. I wasn't expecting such refinements and all the shims fell onto the table when I unbolted the vice. I didn't take long to re-shim.

3) Angle adjuster

When the machine was all reassembled I noticed that that the blade wasn't quite square with the vice axis. I thought it was just simply a case of adjusting the eccentric stop but that didnt work because the clamp bolt was hard up against the end of its slot. So out came the die-grinder again. With a slightly longer slot I was then able to alight the blade perfectly and fix the position with the eccentric stop. The real zero degree position is now slightly off the scale but I'm happy with that knowing that I can find the real zero every time.

4) Blade guide

The support roller for the back edge of the blade is set in a spindle which sits in a cast 'v' groove. The groove is a little too deep which meant that if the blade is ever pushed this far back, the blade teeth will be running on the corners of the pairs of guide bearings for the side of the blade. This will destroy them quickly. I sorted this by putting thinner much thinner washers under the guide bearings to drop them down a little. Its not a perfect repair but will do for now.

General conclusion...

All this took me the best part of the day but I'm not unhappy about it as I am a bit on the fussy side. I can sleep at night now knowing I have four less things to worry about So overall, would I recommend this product ? Oh yes! It cuts beautifully. Here's my very first trial on a 45mm bar of aluminium. I was able to cut a slice less than 1mm thick and just look at the surface finish !!!

Thanks all for your very useful and thought provoking comments. I certainly hadn't thought much about the speed aspect !

Due to space constraints I do tend to favour one machine capable of multiple tasks, provided of course it does all of those tasks reasonably well.

Martins Axminster seems to have this covered well. Strangely its just not available right now and I cant find another machine that has a similar wide range of speed. I wonder why that is ?

There seem to be plenty of robust-looking machines out there for about £500 (for example the Makita) which one could feed through a £50 RS controller, which might then make it suitable for slow but steady metal cutting, albeit with appropriate work-piece holding ? Or am I missing something ?

Gerry

Finally after years of ridiculous hand sawing I've decided to get myself a bandsaw. I'm erring towards the tall standing type that are usually described as being for woodworking. However half the time I need to cut bits of metal, which in the worst case would be a 5 inch diameter bar of aluminium or steel plate up 1 inch thick.

Even with the right kind of blade fitted I can see an issue with this type of saw is that the table doesn't move so one would have to constantly push the workpiece towards the blade. With heavy lumps of metal this could be challenging and depending on how one chooses to do it, possibly dangerous too.

My question is therefore: Am I 'barking up the wrong tree' in thinking that a woodworking saw would do for lumps of metal ? If so, what would you recommend ?

Gerry

Gentlemen, seven 'quality' responses. Thank you all very much. What a site this is. Anything you need help with is available !

Gerry

I've offered to help fix the doors on a 1950s~1960s hangar. Its only a small steel framed agricultural type building to house 2~3 planes. The side-to-side sliding doors are top-suspended, with steel frame and trapezoidally corrugated steel cladding.

Age, use, and almost certainly lack of maintenance means it is almost impossible to move them now. They don't appear to completely resting on the ground but there may be intermittent contact.

I imagine wear and tear of the runners and bearings is the issue and I feel it must be fixable for not too much money. But I haven't been up on a ladder to have a close look yet.

Its a long shot I know but just wondering if anyone has experience of such things, in particular:-

a) Is the suspension system typically a square 'C' sectioned runner ?

b) Might the rollers be height adjustable for wear or fixed size ?

c) For runner and roller repairs would it be necessary to remove the door completely or could it be done with the door jacked up ?

All experience appreciated

Gerry

The klueber greases mentioned are fine. But if you don't want to spend too much, the key grease property you should look for is it's consistency or penetration number. Ensure that you get a No.3 which is 'stiffer' grease than most others which are typically no.2. Stiff greases will 'channel' faster than soft ones. This helps keeps temperatures down and is particularly helpful on vertical shafts where the excess grease that gets displaced to the upper side of the bearing is always trying to slump back into the bearing.

Of course, other properties like viscosity etc can be important in high speed applications but quite honestly for an intermittently used drill I really wouldn't worry too much

Gerry

Doug, there are huge loads on turbine bearings but they also have large bearings to carry these loads. So there is no TB (true brinelling) generally. But FB (false brinelling) can be an issue if they remain static for months and months and its cause by the continual flexure in the structure. That said, friction increases and noise are not problems so the damage is generally just accepted as an ageing characteristic, generally.

Gerry

Hopper is almost correct !

There is true brinelling (TB) and false brinelling (FB), quite different things.

True brinelling (TB) is caused by the application of heavy loads when the bearing is stationary or virtually stationary. Clive's Saab wheel bearing is an example of this. In other equipment TB very rarely happens unless something has gone badly wrong.

Every other case mentioned is either FB or a more generalised fretting damage. FB is just a special case of fretting damage where the damage is restricted to ball contact points as a result of very small movements that displace the lube film. These contact points then wear due to the lack of lube and cause the formation of hard ferric oxide which accelerates the wear process. The pits can become highly polished. Visually they resemble the marks from a brinell test. But whereas a brinell test makes indents that are plastically formed, 'false brinell' marks are basically abrasive wear pits.

TB and FB both affect bearings in three ways. They put perturbations in the generally uniform friction torque, create noise and vibration if you run at high speed, and potentially reduce the fatigue life of the bearing. For clockmakers the first is the general concern. In electric motors, fans etc, its the second. One rarely gets to the third in industrial equipment because the noise will upset people first and the bearings will be replaced.

As mentioned, FB is caused by local lube film breakdown. This happens with greased bearings and it takes usually tens of thousands of small angular oscillations, such as one would get in a pendulum suspension or pallet arbor. One can combat this to some extent by stuffing lots of grease into the bearing such that the local grease displacement around the rolling elements can't happen. But if it's a clock, this excess of grease drastically increases the friction - which is the very reason for using a rolling bearing in the first place. Oil is very effective at stopping FB but you need seals to keep it in and they add friction torque too.

Gerry

Thanks all.

Ian, yes I wondered about trying this after seeing multiple threads on one bolt on a Youtube vid some time ago. My "feeling" is it wont go too well on a smaller scale with burrs etc.... BUT ....I have nothing to loose as I can skim back later if needed. I might even learn something in the process. If it fails, I'll glue on a sleeve as Tony suggests.

Peter, I did wonder about the actual positioning of the lenses relative to the thread. But I played about and it didn't seem to make a difference, as least as far as the focusing was concerned. Perhaps field of view or fringes might be worse. I'll admit to not really understanding optics. Let me get the thing properly screwed in and see how it works and re-thread in a different position as required.

Gerry

I have some 1970's Russian microscope objective lenses that I want to use in my 1940s English-made microscope. I feel the quality of the Russian optics is a little better and the lenses are much larger diameter and let more light through.

The threads on the two tubes have the same outside diameter but unfortunately the English one is a 0.7mm pitch whereas the Russian one is a 1.0mm.

I ' think' there are two ways I could modify the Russian tube to make it fit.

(a) I could fill the thread with a hard solder and re-cut the new thread straight into the old one.

(b) Another way could be to machine back the Russian thread, glue/solder on a sleeve and recut that with the required 0.7 pitch.

I 'think' (b) sounds more sensible. Would you agree, or do you have any better suggestions ?

Right then, now that all the dust has settled I thought I'd send a few words in response. First of all thanks all for you advice and comment. Perhaps I should have added that I'm not a completely wet-behind-the-ears erk and I do deal with very heavilly loaded structures on a daily basis. So no need to worry about safety.

Many suggested that devices like this are 'pared to the bone to minimise cost'. This is clearly not the case with this crane which exhibits all the signs of component standardisation for economies of scale. A great example of this is the main hinge bracket which is 3/4 of an inch wider that the main beam that sits in it. (It looked so awful I put plastic spacers in the gap to make sure the beam didn't slide about!) So clearly this cranes main post is used in a bigger capacity model. Then there's things like the bolts that are either too long or too short so that the threads become load-bearing in shear. ...Not to mention standard soft and thin washers that don't reach the side walls of the box sections so don't spread the loads into the structure in a proper and decent way.

As I said in my original post, I hadn't done any calculations. But one only has to 'look' at the crane to see that exceeding the rated load by 10% wouldn't be a disaster and that with some effort and judicious application of bits of scrap, probably 50% more might be safely achievable. I'm not sure I would ever need this much though. I suppose I just hoped that someone else had already done this exercise and would be able to say from experience what worked for them.

What astounded me the most if I'm honest was that I got more warnings about safety than others who asking about electrical wiring issues! Come on its only a simple crane, and as some pointed out, so easy to test with bags of sand.

Gerry

I'm not sure the angle is to do with pulley contact area. I think its to do with the distortion of the cross-section of the belt as it bent. The tighter the bend the more the distortion.

I got so confused by data on the net so when I made some pulleys I bent the belt into the working radius of the pulley and measured the resulting 'v' angle on cross-section. My measurements seemed to agree with some of the internet guidance and after making them they seemed to work too!

Gerry

Thanks all for your comments. All sorted.

Gerry

These left and right-handed centres came to me with some other stuff. I have no idea what machine or equipment they come from but they are no good to me.

Does anyone recognise them ?

Would they be of use to anyone ? If so I'll be happy to send for the cost of the postage. If not, I will remove the 'potentially useful parts' and bin the castings.

I bought this small engine crane for lifting things in the workshop and garage a while back. Its rated at 200Kg and 500Kg at maximum and minimum extensions of the jib.

So far this capacity has suited my purposes very well. However one day i may need to lift something heavier so before that time comes I might undertake a little project to add a little more robustness.

I haven't done any calculations on it yet but before I do I thought I'd ask the structural stress experts here where from experience (bitter or otherwise) they might be inclined to beef it up a bit ?

My first thoughts are the rear wheels !

Oh dear, all you microscopists aren't going to like this so turn away now if you have feelings for lenses.

In the words of Bernard Cribbins "we wos getting nowhere" ! I began to clean the lenses and graticule discs as carefully as possible, fluids and no abrasion etc, but in the end only mechanical removal worked. The culprits were these things.....

100% of the glass surfaces seemed to be covered in these myriads of fine lines which where interspersed with white dots. Invisible to the naked eye, these dots were very tenacious, quite hard and almost crystaline in their texture. I found the only way to shift them was to take a new flat-edged scalpel blade and run it carefully over the surfaces.

I couldn't detect that the scraping with the steel blade left any mark on the glass, but if it did it was invisible to my small 20/40x microscope.

I'm puzzled as to what might have created this phenomena. I have heard of fungus being a problem on lenses, but fungus doesn't normally follow straight lines, does it ?. So perhaps it was the deposits of some kind of spider or mite?

I have more lenses to do. What are your thoughts on the use of an ultrasonic cleaner next time ?

Gerry

I have crazily agreed to paint some 50m or so of white lines outside an airfield hangar to help with manouvering of aircraft.

The obvious way is to paint them but having done this before for some reason it seems to take ten times longer than one imagines when you include the marking up.

As I wont be doing this until the spring time, I have some time to plan the job.

However I'm just wondering if there is a much smarter way of doing this task that better people than me know about. ....Something like a tape that could be unrolled and then melted onto the surface with a hot-air gun.

Any thoughts would be appreciated.

Gerry