Member postings for Macolm

The brush material resistivity is mainly a function of the supply voltage. A brush bridges two commutator segments so partially shorting the relevant winding, but theoretically at the commutation point there should be no coupled flux. However nothing is perfect.

I suspect the “AC or DC" question was really “mains or battery”. Certainly, some heavy portable tools like angle grinders have different brushes for 240v and 110v versions.

I note the cast iron wheel appears to have a groove at the front, probably for a dedicated puller. The aluminium may just have the same feature. This feature was sometimes used to allow removal of tight fitting car engine and suspension parts.

To use it, you would need to make up a split puller which is turned up to fit the groove dimensions, then sawn in two axially so that it can actually be fitted over. You also need a close fitting sleeve to go over to retain it. It is usual to make the split sleeve also have the detail repeated to fit a threaded bush for the extraction bolt.

A puller like this is able to apply much more force that the universal type, and with little risk of causing damage, but is quite a lot of work to make.

If the chuck is a copy of Albrecht etc, the main knurled sleeve is in two parts with a thread between the tightening knurling, and the remainder. As supplied, it is not only invisible, but also very tight. However, if you make up hardwood or aluminium half shells to allow firm damage free gripping, it can be unscrewed.

Dismantling is then straight forward (but don’t loose balls), and there is through access to drive out the arbour.

It is quite possible to design a two phase inverter (VFD) to run a "single phase” induction motor (ie with main and start winding). Indeed, Maplin did sell such a thing briefly some years ago. The phase angle of the second output would simulate the capacitor(s) phase shift, and the effective voltage would probably also need to be reduced.

However, while there might be merit in being able to make an already installed motor into variable speed, there would seem to be little merit in this configuration in a new machine since the disadvantages of the single phase motor would remain.

I would be inclined to try a somewhat nasty fudge to restore the necessary interference between the split ring and the outer ring. Find some 2 thou (or thereby) brass shim and make packing pieces to insert in the splits. Brass would be more able to conform to the irregular split line and bed to a uniform spacing, and if necessary, anneal it.

Putting 2 thou in both splits would result in circa 1.3 thou increase in diameter, so quite a tight interference. You would probably need to glue the slivers of shim in place for assembly, but once pressed together it would be solid.

Belatedly, I came across the spacer piece I made to eject short MT parts on my Bantam. It slides across the slot, then the smaller section is offered against the offending item, and the normal ejection made with the handwheel. Make it a close fit, very similar to photo. While anything that fills the gap might assist ejection, it may get wedged and be very difficult to recover, particularly if ejection fails.

It was made from an offcut, and turned between centres.

My version also 78.5.1. I have just checked file location of my address book (which I changed long ago on to a second drive that is reguarly backed up to an off line store). There is indeed abook.mab.bak file, not very recently accessed. The active address book is in a file abook.sqlite, and I checked it is indeed the active file.

So indeed, the format may have changed, but if so this has been transparent to me. Perhaps it was done in the background, and the process failed on your computer. Thunderbird and such like are very prone to make a new (empty) file if unable to access the "right" one.

Check the Thunderbird website. I think sometimes the program creates a new profile, but the files are still there and there is a procedure to reinstate things. Hope for the best, but even then still very annoying.

My first lathe has a mix of feed directions, and no, I never had confidence which. The solution was to inscribe arrows beside the hand wheels as follows;-

Lens manufacturing technology has advanced to the point that any practicable optical design can be produced. Different lens maker have their own methods to blend the “infinity” distance zone to the reading patch at the bottom, but it is always a trade-off of distortion against optical aberrations. That said, the best varifocals work very well for most people.

If you are comfortable with ordinary varifocals and have a proactive optician (and sufficient money!), you can do what I have done and have an extra workshop pair. It seems best to choose the same lens type as your main pair. You choose a closer maximum distance, but keep the reading focus the same. I find one meter focal distance (to replace infinity) best for me, which means one dioptre more. The benefit is that the progression is more gradual, and all of the range is useful.

For example, suppose your prescription is +2 dioptres for distance and +5 for reading (addition is +3), then the workshop glasses would be +3 for “distance” and still +5 reading. The lenses do need to be set up to converge correctly. Some makers produce such specialist lenses, but these might have a different “feel" from your main glasses.

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Edited By Macolm on 31/08/2020 22:04:48

Quite so, but he has had limited success with that.

The point about the LM317 solution is that it would supply a simple LED (not a 12V component of unknown content) with a constant current (constant light output) irrespective of applied voltage. Though primarily intended as a voltage regulator, it is equally suitable for this application.

For a white LED, say the forward voltage at the required light output is 4V, allow 4V minimum drop across the LM317 and the associated resistor, and the supply can be anywhere between 8V and 35V. If there are spikes greater than that, agreed additional clipping components might be necessary.

The version of the LM317 needs to be chosen for the dissipation that results from dropping the excess volts. However, provided that at normal supply voltage the power is within the working limit, the device does contain thermal shut down that would allow it to weather occasional spikes. Note also that the 0.1 micro-F input capacitor is recommended to swamp the inductance of the wiring, which might otherwise cause instability.

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Edited By Macolm on 16/08/2020 21:07:27

Assuming the device consists of an LED with a series current controlling resistor, the capacitor would need to go across the LED only. A capacitor directly across the supply will almost certainly be useless.

If you can manage simple electronic assembly, you could use an ordinary LED, and make a small constant current circuit with a LM317L chip and a single resistor. This could be only slightly bigger than the ballast resistor you have. The Texas Instruments data sheet for the LM317L can be found easily as a free download, and shows a suitable circuit. The LED will then be unaffected by the battery voltage, provided you can keep within the power dissipation of the chip. Likely safe choice of LED current would be less than 10ma.

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I meant swapping drives in a RAID volume. Yes, agreed you need multiple drives (to provide a hierarchy) that are isolated (disconnected) except when synchronising. I also agree that cloud backup poses speed problems for many people, and it is also not clear what protection against encryption by malware it can provide.

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RAID provides quick reinstatement of redundant storage, appropriate for business use. It does not cover for other misfortunes, for which conventional or cloud backup is additionally necessary. Data security by swapping drives seems a lot of work for something that can be achieved easily by other methods.

Intel did indeed include a RAID controller in some chip-sets, and did warned that if accessing a drive was attempted other than in the array the contents might not be accessible! So a failed motherboard, and your data might not be recoverable.

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A bit late, but for Windows I would recommend a drive for the operating system, and a separate drive for data, photos etc. To address the various disaster scenarios you need storage that can normally be kept disconnected (eg USB memory with ideally 3 drives cycled round). This covers hardware failure, corrupted files, deleting things in error, viruses, malware encryption and so on provided you are diligent and reasonably alert. Beware RAID controllers that tie the drives to them, so that a failed controller locks you out.

The separate OS drive (eg a 250GB SSD, less than £30) can get by with less secure provision since you can always reinstall everything, though restoring a backup image is much more convenient. Macrium, Aoemi backupper and others have free editions, and take only minutes to make an image of the (data free) OS. With cunning you can restore such an OS image to a new drive. Recent processor/motherboards have a unique identifier that is registered by Microsoft, and the re-installation should be automatically validated.

For the data, Free File Sync is an excellent utility. It only writes changes so typically will sync tens of gigabytes in a minute or two. It copes with complex re-arrangement of folders seamlessly.

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Oh dear! The Camloc mounting is indeed heat treated, and unfortunately so is the body of the Burnard collet chuck, assuming it is the integral Camlock mount type.. It does look as if the spindle is bent. The next thing to do is fit a Morse sleeve in the spindle taper to see if that runs true. Can you see if the conical surface in the second photo is concentric with the internal taper? It may have been ground by a previous owner.

Unless the spindle is somehow fabricated from two parts, rectification looks near impossible.

That`s the obvious way where there is enough room for the extra length, and including any considerations about cross section if there is axial loading. In the case of something like a drawbar thread, it needs to keep within the original profile and also take the tension force.

In most cases this “thread adaptor” problem is easily solved, provided you have a little proficiency in screw cutting. (I previously posted how I converted M12 threaded Morse parts for a 3/8 Whitworth drawbar). Clearly a wire thread insert works fine, so the problem is to make a similar item if the available wall thickness will be insufficient to support the cutting forces

However, we can trade wall thickness against the depth (or percentage engagement) of the external thread by truncating the inner portion of the thread form. Decide the minimum diameter necessary, and bore out the thread which needs converted to this size. Now turn up the adaptor per the sketch. Cutting the external thread is very easy to do using an ordinary V lathe tool, though preferable with a flat on the nose of the V. A pilot length that is a nice fit in the bored out mating part makes sizing easy.

Do not set over the topslide, but cut the thread increasing the depth to reach the pilot diameter. Now take cuts at this diameter advancing the topslide until the full thread is reached. You can check this using something with the same (full) thread.

Clearly it is best to cut the smaller internal thread first to allow a relatively thin wall.

I don’t have a feel for the core frequency. Certainly the data output is low kilohertz bit rate. However, the individual elements of the capacitive vernier can only be 10 or 20 pf. Secure motion tracking as well as accuracy might need a higher frequency, and of course, this could be the part that is upset by low supply voltage or interference.

Unfortunately, measurement is not particularly straightforward without specialised testgear.

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