Member postings for AJAX

By placing two or more capacitors in parallel you are effectively increasing the plate area and so increasing the effective capacitance. When placed in series, you are increasing the distance between the plates and this reducing the effective capacitance.

The worst reviews of all are the sponsored Vine reviews on Amazon. Don't trust them!

I disagree with the comment to scrap it just because it's an unknown grade. Quite often, I and many others find a use for bits from the scrap bin. If he can't turn it with a reasonable finish now, put it to the side. He may be able to do so when the lathe and tooling is sorted.

I agree with the suggestion of trying some EN1A Pb. Aluminium alloy such as 6082 is another option.

I can't quite read the capacitor markings, but it may well be 1000uF and not 10000uF (10mF).

I agree with your comment regarding fuse on the supply side, but if the capacitor is large there may be an inrush current sufficiently large to blow the fuse.

The circuit is a half-wave rectifier with capacitive smoothing, but in this application (DC supply) the diode protects against reverse bias and the bulk capacitor improves load regulation by reducing ripple.

The open circuit voltage should be around 0.7V greater than the output voltage under load. Consider the IV characteristics of the diode to understand why.

I use one of those pencil type air die grinders. Cheap ebay job. Works really well, and I've given it some abuse. 30 to 50k rpm if I remember correctly. Doesn't use much air at all.

I'm always interested to see simple homemade tools that work.

George (and others) thank you for the information.

It appears the consensus is to use pins and holes and not to bother with keys. I'm happy with that as it's the easier option.

I have some low-strength Loctite (about 6 unused bottles if I remember correctly!) so I will probably use parallel pins and the through-hole option.

That's another consideration. Thanks.

I recently acquired a Myford ML4 which came with a limited number of change gears. The final driven gear has an unused keyway, and the leadscrew is not keyed (it has a small flat) and relies on a bush (fixed with a setscrew on the flat) that has a small pin that engages with the side of the gear wheel. All the torque is transferred via this small pin. Maybe that's a good idea, maybe not. I would expect it to be a likely point of failure in the event of a crash.

I happen to have a collection of keyed Myford change gears that could easily be modified to work on the ML4 lathe by adding a small hole for the pin. However, I'm wondering whether it would not be more sensible to mill a keyway slot and fit a key to the leadscrew. By making this one modification I could then use any of the change gears at my disposal.

I would welcome comments.

If it turns out to be hard wired star, don't immediately reject the motor. I recently rewired such a motor by digging out the star point on the windings. It wasn't difficult to do.

Regarding all the existing switch gear, I would ditch the lot when fitting the VFD. A modern rotary or toggle switch is easy to wire up for controlling motor direction.

Hello George,

Yes, 50.1 kg including the drip tray exactly as shown in the photos. I'm assuming it is an ML4, it has a centre height of 3.5" and the headstock has the bolt pattern I've seen on other supposed ML4 machines.

Quite by chance I had to unload a Myford lathe (which I suspect may be an ML4) from my car today. The bathroom scales report 50.1 kg.

Edited By AJAX on 08/05/2022 10:57:40

Too much heat for the casting but not enough for the rods I was using. That's why I decided they were unsuitable for this job. And as "not done it yet" suggests, there will be minimal load on this part so I'm happy with my screwed and glued repair.

Even propane was hot enough to melt the broken casting.

I thought it might be useful to give a quick update.

I bought some cheap "aluminium brazing rods" with a claimed melting temperature of circa 390 degrees. Not having used any before, I gave them a quick try on some scrap aluminium - an extruded finned aluminium heat sink from a power supply. I started off gently but found I had to turn up the gas to reach a suitable temperature which I checked with a non-contact thermometer. The brazing/soldering worked just fine and gave a good looking joint. I was quite impressed.

Buoyed by my initial success with the heat sink, I turned my attention to the broken casting. Lucky I was paying attention as the casting had a much lower melting temperature! I had barely started before it visibly softened. There was no chance of the rod melting at that temperature so I abandoned the job before it vaporized. I'm guessing it was an aluminium / zinc alloy.

The casting has now been drilled and screwed together, with a good dose of strong epoxy. I'm quite happy to have tried the brazing rods and I would use them again given a suitable material.

That looks very similar to the Colchester lathe pump in this video. It's very easy to split the star and add a run capacitor so it can be used on single phase. There's no real advantage in hooking it up to a dedicated VFD. A run capacitor is a much cheaper and quite satisfactory alternative.

Edited By AJAX on 05/05/2022 17:15:12

Brian, what is the claimed melting temperature of the rods you used? Most seem to be 392 C with some more expensive ones that claim 300 C.

Pete, that's very kind of you to offer; however, I'm going to get some brazing rods and give it a try on some scrap. I'd like to see if I can do it myself as it could be a useful skill for future tasks.

Thanks for your suggestion, Brian.

Do you think it would be a good idea to grind the crack out a bit before brazing? Vee-groove all round? I could do this quite easily with a rotary burr. As it stands, it would be impossible to clean the faces inside the crack without opening it up somehow. Do the brazing rods work well in filling cracks and if so what is the optimal gap?