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Member postings for Mark Rand

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

Thread: ebay purchases : VAT
16/01/2021 15:35:31

I should have another datum in a week or two. Not worried about VAT and handling charges, but more than a bit miffed that it's easier to order stainless steel toolwrap for heat treating from California than the UK.

Thread: Standards of Electrical Wiring
14/01/2021 16:50:33

Looks good to me. It's a real pain to have to put a joint in a cable when you do some new work because you did a nice neat job the first time and left no slack for adjustments. smiley

Thread: Nitrogen as an Energy Store ...
11/01/2021 19:42:28

The Carnot Cycle efficiency of such a system is appaling.

Thread: Removing powder coating finish from metal.
08/01/2021 17:27:47

Take it to your local powder coating firm. They'll burn it off in their oven.

Thread: Cleaning Brass?
08/01/2021 17:22:43

Benzine was/is light petroleum spirits. benzene is the nasty stuff.

As a youf I ended up mending my mate's dads "Tickoprint"* Quartz crystal oscillator based watch setting machine.

He used Benzene! Died later from cancer...

*Quartz crystal oscillator with dividers down to a multiple of a watch escapement's ticking speed, driving a rotor with a helical ridge on it like a mower reel. The watch's ticking was picket up by a microphone and amplified to drive a hammer bar towards the rotating cylinder. When the watch was accurate it produced a straight line of dots on a till roll. too fast, the line slopes one way, too slow it slopes the other. The watch/microphone was in a jig that could be rotated to test the watch in different orientations, to mimic wearing. Fault was an OC81 transistor that had died.

Thread: Which Slideway Oil 68 or 32
31/12/2020 22:45:55

ISO68 oil for most horizontal slideways.

ISO220 for most vertical slideways

ISO32 for rapidly moving slideways, such as surface grinders.

It is only essentially the viscosity that is different.

Those are what I use in my shed.

Thread: TIG is harder than it looks
31/12/2020 20:06:08

Training is really useful with welding. I managed to get City&Guilds levels 1&2 in TIG and MMA (Stick) at Northampton College. The first because of a redundancy deal, where the company paid for 'retraining' when I took VR from the IT department, The rest from some of the redundancy payout.

4 hours one-on-one for £80 sounds excellent value for money. Even more so if they can start up where you left off if you want to go further.

Thread: Stent Tool Grinder
22/12/2020 22:39:29

To be fair, I trawled the BSME site and couldn't find peter's grinder.

Thread: lost drive to power feed
22/12/2020 21:35:47

Strangely enough, my one's got 1/2" silver steel ends, threaded 1/2"BSF, held in with Loctite 603 for similar reasons laugh.

It may be worth putting the feedscrew on a couple of V blocks to check that it is straight. If anyone's tries to lift the mill with slings under the table it might not be. Mine was 1/8 out of true! Straightened to 3 thou TIR with a bit of work.

At this point, it's also worth inspecting the feedscrew nut for wear. unscrewing the outside end of the adjustable nut and having a look down the hole will give you a good idea of how much meat is left on the threads. If they look as clapped out as mine were, you might need to make a new set. Not a particularly complicated job if you have a lathe that can be geared to cut 5 tpi and can grind and ACME bit to sit in a boring bar. If the threads look usable, then just adjust the backlash when you've got it all back together. The one thing that Balding Engineering got very right was to use cast iron nuts on the feedscrews. The nuts wear in preference to the screws unlike certain well known US mills, where the bronze nuts ruin the feedscrews...

A lot of improvements were made on the later Mk2 versions and they've had 60 years for people to abuse them, but when they're all sorted out they're bloody good machines (not biased at all!).

21/12/2020 20:03:28

I keep writing without checking or thinking. Sorry!

There should be two T-nuts in the slot at the front, one on the left and one on the right. The two holes that should be in the bottom of the slot just stop the T-nuts being moved past the point where the drive could destroy itself.

With the standard feed on the Mk1 being limited to 4 1/2" per minute, it's useful to be able to set the stops and wander away to do something else. I think that the optional faster feed just used a 2 pole motor instead of the 4 pole one.

21/12/2020 19:12:01

After you've got it all fixed, put some permanent stops in the T-slot on the front of the table. There may well be two tapped holes in the T-slot to locate them. That way, the feed will always get cut off before damage can occur.

21/12/2020 19:08:07

It's much easier to get it apart and back together if the table is removed from the saddle. That requires a crane/engine hoist/at least two people (it's about 300-350lb). Accsess is so much more difficult with the table in the way, as you have discovered.

Your best bet is probably to remove the left hand bracket. If you push the table a bit to the right, then you can manipulate the feedscrew independently of the table. Now you can turn it to feed it into the dog clutch assembly and tilt it up/down/sideways to try to get an easier fit without it binding in the hole and driving it round before you've got the key in the slot.

You'll get there! laugh

21/12/2020 17:51:11

Oops, i was talking b*ll*cks. Saying the right thing for the wrong reason.

The feedscrew IS slotted all the way along, But the reason you can't get it all the way out on the left hand side is because the non-threaded part of the feedscrew won't go through the feednut! That's what's locking it all up when you get it all the way to the left...

21/12/2020 16:26:55
Posted by Mark Guy on 21/12/2020 14:09:03:

Mark when you turn the left hand lead screw handle the dog drive turns with it even though the key that serves two purposes I.e locks the lead screw when it’s engaged and also holds the dog gear carrier. So it’s impossible to line the two up so when you screw it up it just locks against the key. Also I’m unable to back the bed right of to the left as it also locks up and not sure why

You can't remove the bed on the left without removing the end brackets and handles.

 

The feedscrew is keyed all along the threaded length but not far on the solid part of it and the dog clutch/gear assembly is permanently keyed to it rotationally (sliding fit axially). so the feed screw has to be withdrawn from the right hand side of the machine. take the left hand handle, dial, dial carrier and bracke too off. Take the right hand bracket off (can leave the handle etc. attached) then wind the feedscrew towards the right. Once it's past the feed nut, at the left side of the saddle, you can slide it out the rest of the way. There's a likelyhood that you'll need some creative tapping/levering with a drift and a wooden lever to get the brackets off the table, since the dowels are a good fit.

 

Pete:- I can't measure the centre didtances between those two gears, since one is in the gearbox and the other is buried in the carriage. But I have double checked by measurement that all the spur gears in the box are 20DP.

Edited By Mark Rand on 21/12/2020 16:28:11

21/12/2020 13:32:16

There is good news and bad news...

The old gearbox was still there under the surface table.

However

There is only the 20T gear because the 42T gear is part of the saddle assembly. The 20T gear is also rather badly worn. I suspect that it won't last all that well. One or more previous owners weren't all that bothered about lubrication, protection from brute force, moisture etc.

20201221_130621[1].jpg

As for the feedscrew key,the dogs should slide on to it without any force, but no noticeable clearance.. You may either have a small burr on the key or it isn't all the way into the keyseat.

 

You are welcome to the gears if you want them. Just PM me an address.

For what it's worth, I'd probably just use a collection of Myford changewheels, bore them out and Loctite them on to either manufactured bushes or the turned down originals.

Edited By Mark Rand on 21/12/2020 13:46:07

21/12/2020 09:50:07

I need to check in the shed, but it's just possible that I might have a set that could sort you out.

My Mk1 VBRP had a burnt out feed motor and cracked gearbox casting when I got it, but I managed to buy a replacement gearbox and motor from a pikey* who was changing his machine over to single phase with one of the nasty bolt on feed drives.

I think I've still got the original gearbox under a bench, so If I can find it, I can liberate the gears from it and post them to you.

If I can't find the box, then they're either 20DP (same as the changewheels for the box), which would be available from HPC-gears or they're 22DP, which are mich more rare in the UK.

 

*The sod charged me extra for the motor, even though it's an integral part of the assembly...

Edited By Mark Rand on 21/12/2020 09:52:02

Thread: Myford ML7 faster speed
18/11/2020 20:23:30

Just a few notes:-

Pressurised oil feed is not needed for high speed, it's needed for low speed. The load carrying capacity of a hydrodynamic bearing increases as the speed increases.

A hydrodynamic bearing has zero load carrying capacity for loads that occur at approximately half per rev. Hence the danger of oil whirl in lightly loaded bearings. This tendency is reduced by using lemon shaped bearing bores. In internal combustion engines, half speed loads are intrinsic in the four stroke cycle.

If the bearings aren't running warm and there is a reasonable rate of oil feed, then just jack the speed up...

The counter shaft bearings will fail well before the mandrel bearings do, they are smaller, more heavily loaded.and less reliably lubricated.

 

Edited By Mark Rand on 18/11/2020 20:24:10

Thread: Making storage air power out of thin air - new UK powerplant
08/11/2020 23:09:11

Just a small point:- liquid gas production plants use turbocompressors, with axial flow compressors, heat extraction, then axial flow turbines to expand the gas, cool it and feed power back to the compressors. This is more efficient than the free expansion in the Joule Thompson system.

Having said that, you still need to supply the heat that you rejected back to the liquified air/nitrogen in order to get meaningful output from the gas at the consumer end. You also need a plant that's got reaonable efficiency in extracting what's left of the usable energy at the consumer end. 75% cycle efficiency? Not convinced.

As a datum, AEI/GEC machines Rugby supplied what were the world's largest synchronous motors at 29,000hp for an oxygen liquifaction plant for a steel mill in the mid '70s...

 

If the plant stores the rejected heat in a usable form to help to re-gasify the air I'll believe that it's meaningful.

Edited By Mark Rand on 08/11/2020 23:18:26

Thread: Learning CAD with Alibre Atom3D
08/11/2020 22:37:11

How much help is there on creating/editiing a Post for your machine?

Thread: Myford Oil Pump
28/10/2020 22:04:11

The one linked to is a Wanner oil pump. They are good and there are a number of options for oil/grease and different nozzle types. The original myford guns were a very old Tecalemit design that could have been improved when new inventions such as plastics became available.

 

And yes, I have and use a both types.

This is where mine came from. They had the ends I needed for the recessed spherical cups in my Beaver milling machine.

Edited By Mark Rand on 28/10/2020 22:08:08

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