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Member postings for AJAX

Here is a list of all the postings AJAX has made in our forums. Click on a thread name to jump to the thread.

Thread: Fortis Vice
08/06/2022 19:38:29
Posted by Rockingdodge on 08/06/2022 17:58:20:
Posted by Jon Lawes on 08/06/2022 17:08:17:

My previous post I think got lost. I was pointing out that wartime equipment was often unpainted or blackened to save paint for the war effort.

I think you could be right as there seems to be no sign of paint but it's not that rusty, what I thought was heavy corrosion could well be an as cast finish!

I'm another owner of a Fortis Steel vice (pictures coming soon...) and although I cleaned it up a while back I don't recall there being any paint to remove. And mine is "Ministry of Supply - Property of HM Government" if that helps indicate the age.

Thread: Denham Lathe Restoration
07/06/2022 22:43:15

The "motor date" probably refers to the British Standard, bss170:1939 and not the date of manufacture.

Thread: Powering a Suds pump?
07/06/2022 10:35:52
Posted by Andrew Tinsley on 07/06/2022 10:19:07:

Found another 6 microfarad cap so using both in parallel gives 3 microfarads. This works a treat, so thank you Andrew Noyes! It gives almost perfect balance, using my scope (unearthed for this measurement!)

The tank and pump are stand alone items, to be switched to whatever machine is in use, so single phase is the best bet.

Thanks everyone for their input.

Andrew.

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.

Thread: Review prejudice - who do you trust?
03/06/2022 07:21:21

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

Thread: More beginner questions
31/05/2022 11:55:42
Posted by Andrew Johnston on 30/05/2022 20:44:52:

First things first; if you don't know what the metal is then bin it and get a known grade of metal. The ideal would be EN1A leaded. If, with a known grade of metal, the finish is still poor then the tool shape and position can be considered.

Andrew

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.

Thread: What does this circuit do ?
26/05/2022 22:38:29
Posted by SillyOldDuffer on 26/05/2022 18:24:55:

10,000uF is a lot of capacity to put on an existing DC supply and is unnecessary if the diode is only there to protect against a reversed connection.

What 10000uF would usefully do is a basic smoothing job on the choppy DC that comes out of a car battery charger and many simple transformer wall-warts. It would even sort out an AC input. I expect that was its purpose; providing some reasonably smooth DC.

The fuse ought to be on the input side. As is, if the 10000uF capacitor shorts out, as electrolytics are prone to do, then the capacitor will go pop, possibly blowing the rectifier and igniting the unfused cable too.

Dave

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.

26/05/2022 17:20:01

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.

Thread: mini grinders
19/05/2022 20:20:45

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.

Thread: T-slot cutter
19/05/2022 20:16:49

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

Thread: Myford ML4 change gear modification
16/05/2022 19:29:49
Posted by Georgineer on 16/05/2022 18:02:17:
Posted by Nick Clarke 3 on 16/05/2022 07:44:59:

A reminder that the original Drummond/Myford pins were tapered and only fit from one side.

I would be tempted to not do this with your new pins but use parallel pins held in place with loctite or similar.

I can't answer for the Drummond (though I have my suspicions) but the Myford used parallel pins of 3/32" silver steel. I have this in original Myford paperwork somewhere. Not Loctite - you want to be able to remove the pins, so nothing tighter than a sliding fit. .

The Myford way was to drill blind holes in the gears and collars, which trapped the pins in place. If you drill through-holes, the pin will work its way out and let go in the middle of a cut. Don't ask me how I know.

Ajax, I have used the pin drive system on my father's and then my own ML4s for over fifty years and it never caused the least problem that wasn't of my own making (see above!).

George

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.

16/05/2022 19:22:53
Posted by Bill Davies 2 on 16/05/2022 11:07:17:

Ajax, assuming that you would want to key the intermediate gears, they would have to have bushes with a key, through each pair of gears, to bear on the non-rotating shafts on the banjo. There would seem to be little benefit in keying the final gear to the leadscrew, if the previous gears transmit their power via pins.

Bill

That's another consideration. Thanks.

15/05/2022 21:43:39

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.

Thread: Boxford AUD/BUD single phase conversion
10/05/2022 18:59:07
Posted by Kingofthehill on 10/05/2022 18:50:18:
Posted by Richard Millington on 10/05/2022 11:25:57:

Check the motor can be wired Delta 240v.

The rating plate suggests that it can be. Suppose I won't know for sure until I pull it out of the cabinet and have a look.

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.

Thread: Weight of Myford ML4 ?
09/05/2022 21:44:51
Posted by Georgineer on 09/05/2022 20:33:00:

Ajax, that looks convincing for an ML4. Does your weight of 50.1 kg include the drip tray shown in the photos? I have recently lifted an ML4 (less tailstock and drip tray) from ground level to car-boot level without distress, so I would estimate it about 40 - 45kg plus those bits. Unfortunately my ML4 leaflets don't give weights, so I can't quote from source.

And before anybody asks, yes I have the manual handling and lifting certificate (and a 35-year-old disc injury) so I don't take chances!

George

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.

08/05/2022 10:57:22

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.

20220508-104744 20220508-104737 20220508-104835 20220508-104843

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

Thread: Suggest a repair method for broken aluminium alloy casting
06/05/2022 22:33:23
Posted by noel shelley on 06/05/2022 21:40:27:

Propane is more than hot enough and great care is needed to control the heat and get the rod / work to flow. I would say that you had TO MUCH heat. The heating is VERY critical. Noel.

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.

06/05/2022 20:51:46
Posted by Brian Wood on 02/05/2022 12:40:56:

Bazyle,

A propane flame is quite hot enough, no need for oxy-acetylene, that might meld the part you are trying to repair.

Brian

Even propane was hot enough to melt the broken casting.

06/05/2022 20:50:14

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.

Thread: help wiring a 3 ph coolant motor
05/05/2022 17:14:16

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

Thread: Suggest a repair method for broken aluminium alloy casting
01/05/2022 21:25:16
Posted by Brian Wood on 01/05/2022 18:04:56:

I have made repairs with the aluminium brazing rods which are strong enough in that sort of thickness. They look satisfactory too

I recommend you try them. Be sure to use a stainless steel brush to abrade the joint all round before you apply heat, the brazing torch should be quite adequate, this is not high temperature work

Regards Brian

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.

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