Member postings for John Haine

Aha! Thanks Jason, well found.

From one of my earlier posts in that thread:

After some though I decided that the helix angle of the tap isn't really a problem. You have to remember that the tap is significantly smaller than the hole you are threading. Yes, in principle as the tap rotates the helix may cause some rubbing, but both the smaller tap radius and its form relief are quickly taking the cutter surface away from the work, as it were.

Edited By John Haine on 15/05/2023 09:51:56

Somewhere on this forum there's a thread where the use of taps for thread milling was discussed with several contributions from John Stevenson, though I can't readily find it. I did contribute myself and John was very helpful. For my M14x1 internal thread I use two cutters (different trials). One was an M8x1 tap, with all the rows of teeth ground away except one and the tip ground square. That worked well but is limited to conventional milling down into the hole, and unless you also grind away all the teeth but one it will only do one pitch. A single point cutter (like my internal threading lathe tool I discussed) can start at the bottom of the hole and spiral out, climb milling all the way which is quieter and gives a better finish. To generate the code I used a little program provided by Chestnut Pens which Richard kindly modified to allow the use of a tap.

30mm rigid foam foil based insulation, 10mm tongue and groove high grade chipboard on top. Warmer for the feet.

I uploaded a copy of the Isaacs articles to the Synchronome1 group and it is still there at

**LINK**

You need to register to be able to access the files section. If you have problems let me know and I'll somehow send you a copy.

Few or no doom mongers will have actually done the conversion.

Jason, thread milling is cool! I have use two tools, one a modified M8x1 tap, the other a standard small insert tip inside threading tool I got from JB a few years back. Conveniently that has a cylindrical shank with a flat and takes the insert with the cutting edge exactly on axis. The one made from a tap has to be used in conventional milling mode but the other was quite happy climb milling from the bottom of the bore. I cut an M14x1mm thread in one pass to fit the Unimat spindle and the fit was perfect.

A thought on the front-to-back axis. Bob Matthys points out that this may only hang at an angle where the restoring force is just less than the frictional force, which may be slightly off vertical. Ideally one wants viscous friction to damp it. I believe that Bateman's clock actually has the spring clamped in a ground steel bar that just rests on the bracket so there is no damping at all.

On the measurement front, I can't help thinking that a picPET type device would avoid many of the problems at least for analysing short-term motion of the pendulum in fine detail though the OCXO might not be quite on frequency - but at least you can calibrate that out. TVB says that if you run a picPET to measure GPS pulses you can essentially see the Adev of the OCXO.

All episodes available on BBC Sounds

Well, mixed progress. As I was away last week for 4 days I left the clock running and logging data. This revealed a bug that I'd introduced into my logging software - the picPET rolls over after 100,000 seconds and this has to be detected but I had made a mistake with a new version that resulted in it adding 100,000 seconds to the times every beat! By Friday the clock seemed to have been running for the age of the known universe, before the logging program crashed! So I fixed that and started logging again on Saturday - checked the logs both yesterday morning and this morning and found I was getting occasional huge excursions of both amplitude and period. Looking closer this is clearly due to morning sun, which shines straight through the window on that side of the house on to the clock. I had this problem before. Fitting a black card sunshade in front of the sensor truck resulted in disturbing the wiring and that revealed a bad contact as well. Ho hum, the joys of clocks...

So, I have now fixed (I hope) the contact; fixed the logging bug; fixed a sunshade on the sensor and a black card background; and put a stool holding a piece of board in front of the clock to keep the sun off. Let's see what tomorrow brings...

Well the superconductors had zero resistance so the copper would be shorted out. It would however have good thermal conductivity for cooling.

Makes no difference.

I think I recall checking this and the length of the moment arm equals the height of the axis of the tool holder - not sure though.

As there doesn't seem to be a capacitor it is presumably a motor where the start winding just has a high resistance compared to the run winding to give some phase shift. With only 1/4 hp the lathe is definitely underpowered. And apart from anything else the mains cable looks old and horrible and ought to be replaced!

I fitted a 3ph motor to my S7 only partly for variable speed, but mainly to get smoother operation. With the single phase motor the higher speed range on the motor pulley was essentially unusable as the lathe vibrated so much. Going to 3ph has transformed the machine, much smoother and quieter. Single phase motors inherently have lumpy torque.

Google doesn't seem to have any direct link for that motor, and anyway aren't they mainly a car electrics supplier?

Please could you post some photos of the motor and switchgear so we can get a better idea of what you have?

My Super7 came with the Myford fitted single phase motor which was a dog to be honest. Replacing it with a decent 3phase motor and VFD has transformed the lathe..

I'm having difficulty understanding how a differential screw works on the rocking arm. The screw on mine just bears on the rear bar, and the female thread is on the "horn" that clamps to the workhead. I can't really visualise how one can have a differential screw in this application - usually one has a screw that advances through one member with one pitch while screwing into another member, not fixed to the first, with a slightly smaller pitch. Then the effective movement of the second per turn is given by the difference between the pitches. Can anyone post a picture of the arrangement please? I seem to recall seeing a Quorn that was fitted with a standard micrometer thimble on the rocker.

On the other hand it would be easy to have a diff screw on the front bar micrometer, and perhaps more useful.

They are almost certainly Neodymium type. This site:

https://www.kjmagnetics.com/calculator.asp

**LINK**

...has a calculator which will give he force between magnets. I buy magnets from

https://www.first4magnets.com/

**LINK**

...who have a large range at reasonable prices - you could find a comparable size and check what the force is.

I remember using silicon rectifiers in projects in the mid to late 60s, by then they were well accepted components. I remember frying the copper oxide rectifier in my brother's model train PSU when I must have been 10 or 11 around 1960 and my dad replaced them with silicon ones then. It helped that he worked for the company that made them.

In my experience, Arc Eurotrade stock good versions of the ubiquitous Sieg machine tools and provide excellent customer service.

**LINK**

How relevant their "only sold for hobby use" statement is in this context I don't know. The biggest machine is the SC4, you could buy several of these for the price of one new Myford, if you bought 2 Myford Connoisseurs you could have bought a roomful! You might consider getting the Boxfords you have professionally overhauled instead.

Andre, PLEASE could you learn how to post active links? It isn't hard.

It's grossly excessive. If you bought the lathe new then don't attempt any rectification yourself, reject it as not fit for purpose and get a refund. Vevor have a mixed reputation, for obvious reasons!