Member postings for Macolm

Once there is an impression of the knurl on the work, it becomes exactly like three gear wheels running together. They stay in mesh. The advantage of a hunting tooth is that the effects of irregularities and wear will be averaged. The wheels would, of course, be constant pitch so slightly different diameters. If so, this may be a superior knurling tool!

Possibly a "hunting tooth" to average out variations, so avoiding patterning?

This item seems to be branded for various retailers. I have one which was sold as a return for about half the new price. It is really only suitable for wood blades, though it does comes with a diamond blade for carbide, and a stone for steel.

It is only suitable to grind the radial faces, and the indexing is not good enough to control the depth of cut to be the same for each tooth. In use, it just gets you to the next tooth. It is then a case of feeding each tooth against the wheel by hand until you judge it is sharp. However, this does work well enough for wood blades, and they then cut pretty well as new. Most wood blades need different angles for odd and even teeth, so you need to mark every second tooth unless you have phenomenal concentration. I have used it for blades from less than 100mm to 220mm, and it can probably sharpen a somewhat greater range than that. It did need a bit of fettling for best results.

If that suits your requirements then it is adequate provided you do not pay too much, but forget any use for accurate sharpening of blades for metal.

You need ingenuity! A method I have used is to find a length of rubber tube that the nut fits tightly, and use it as a flexible drive to run the nut up the thread. This can work even if you have no access straight on. Getting it started may need something to reach in and guide it initially, perhaps wire with the end coiled to fit round loosely. If you can get the nut started and most of the way home, find a spanner, small ratchet or what have you to finish tightening from afar.

Edited By Macolm on 21/03/2023 17:46:21

Looks like the motor mounting plate is pivoted below, and you just need to slacken the bolt in the slot above. This could well have a nut on each side to loosen, not be very convenient. After changing belt position, tension with the hidden nut and lock with the accessible one.

Another vote for the Rohm Supra SK. Look for the red lock ring. An Ebay source of these is Hilti adapters, available also with many other chuck types. Item 225420242555 at present is a moth-eaten example but good/unused examples come up from time to time. The chuck just unscrews, though very tight. They all seem to be 13mm size, not 10mm, but they are quite compact.

Edited By Macolm on 12/03/2023 21:49:04

Most exciting. We must be on the verge of a perpetual motion machine that actually outputs useful energy as well!

The suspension of Citroen 2CV cars used a “knife edge pivot pin”, though in practice it was a rolling contact. A pull rod with a large round eye, maybe 16mm diameter, connected to the spring, and a triangular pin on the suspension arm with about 3mm corner radius was in contact, finding its own point of operation. It worked very well, with little or no wear over many years.

The problem with that is that the basic hob is not insulated to stand several hundred degrees in immediate proximity, and by the time insulation is added to achieve that, inductive coupling may well be reduced too much to work.

I have long wondered about making a heat treatment oven from one. The plan would be a length of large seamless steel tube for the oven cavity, a layer of high temperature insulation round it, (probably) an air gap for blown cooling air, then the cylindrical coil driven from the electronics round it all. It would need a temperature sensor (thermo-couple) and control electronics.

Nearly all the heat should be generated in the steel tube, and hopefully the temperature inside that would be quite even.

I’ll try. The apron power feed knock off works by releasing the worm from mesh with its pinion. During this, the gear teeth are nearly out of mesh while still transmitting the full maximum torque. As others have confirmed, it can also release under high, but not excessive, cutting forces. This suggests a less than ideal compromise.

Some owners seem to have increased the release force to the point of causing damage. Unfortunately there do not seem to be instructions from the makers as to how to set this up. A much better design would incorporate a dog clutch, since this allows a more robust release interface. In addition, it would be best actuated directly by contact with the stop, not indirect by the build up of force when baulked.

Another annoyance is that the cross slide has a two start lead screw, resulting in the need for quite eyesight challenging setting of the dial. This may have been done because the cross feed rate is already only half of the surfacing rate, and more appropriate feed gearing could not be fitted in.

However, the manufacture is undoubtedly to a high standard, and the smooth controls and minimal backlash (when unworn) make for very satisfactory use.

The knock-off on my Bantam appears to have the original factory setting, since I doubt that the original technical college owners adjusted it. It works OK, apparently without excessive force, though there is a fair clunk on disengagement. I do use it most of the time. However, it is possible to set a sufficient depth of cut to cause spurious operation, but I just accept that as a compromise in a useful but somewhat mediocre design.

Edited By Macolm on 25/01/2023 20:47:59

What about hardwood?

There is usually a laminated on plastic polariser layer on the display panel front face, and the problem is probably due to degradation of this. The polariser is essential to LCD operation. I have no idea if there is any easy cure.

Just for the record, here are images of the central area cropped from the HiView v1.4 software, showing the cross axes (scale factor can be calibrated) and other measuring tools.

I recently bought a Bresser USB Digital Microscope from LIDL which claims to be "full 1080p". The mini CD in the box installed a VGA (640x480) viewer with no graticule. Annoyed, I went to the Bresser webside link given in the booklet, and downloaded Hiview V1.4 (ref 9652200).

This proved to be much better, displays a 1600x1200 image with (optional) fine cross axes graticule that can be calibrated to any scale factor by adjusting a multiplier. There are some other tools including text annotation, and the ability to save images.

The microscope appears to be a common Chinese item, available with various sensor resolutions. I have yet to make a stable stand that can exploit the performance – the included base is fairly useless. The magnification adjustment also changes the object distance, so something reasonably elaborate is needed for maximum flexibility. It may have potential for fine work such as watch making.

The problem is that in many examples, the “thread” helix angle is too steep to allow unscrewing by a pure rotary torque. It jams instead because the component of force generated along the helix direction is less than the friction caused by the torque. Thus some added axial extraction force is needed. If the head is domed without a parallel diameter, this is difficult to apply.

I have used a slotted wood chisel (under the label), and damage still seems unavoidable. To extract these quick thread drive pins, they need pulled out along the thread orientation.

I haven’t tried this, and have no intention of doing so, but I suggest using a Dremel or similar to cut slots per the attached. Anyone skilled in micro-surgery should find this easy. Then use strong end cutters to grip, rotate and pull. You may need to modify suitable end cutters by grinding them flat across the face so as that the gripping/cutting edge is outermost.

To extend blade life somewhat, I have had success with a smear of wax on the blade entry side of the work. Just enough gets carried by the blade without contaminating the drive wheels. This works for both vertical and horizontal configurations.

Not tried this, but might work to dislodge a tight Jacobs taper.

Drill centrally through the chuck as suggested previously, but make it a small hole for a tight fit on a 3mm (say) steel rod. Now with the arbour downwards, fill the space with oil. Enter the rod (only just) and strike it sharply with a hammer to pressurise the space. The difference in areas should multiply the force on the end of the arbor

Some of us will have removed plain bushes from a blind housing in a similar way. It is surprising that this works even with a very loose fit, but the leakage is small for a sharp blow.