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Member postings for Howard Lewis

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

Thread: Run outs
12/12/2019 21:09:34

To ensure that the work is centralised accurately when changed end for end, this is where the 4 jaw chuck comes into its own.

If only a 3 jaw is available, the nearest that you get is to mark the work and the chuck, and when the work is changed from one end to other, align the marks on the work and the chuck. This should position the work in the same place as it was originally.

Probably, I can be accused of being a micron chaser, but not a very good one, when I use the 4 jaw, as I like to get the work centred to better than 0.0005" (12.7 microns) if possible,.

Years of "fitness for purpose" have blunted my love of absolute accuracy.

Howard

Thread: my first lathe.
12/12/2019 20:56:03

A tangential tool is very useful item for most turning and facing jobs.

And dead easy to sharpen, only needing one face to be ground. Easy to set on centre height, if you have a centre height gauge, of some sort.

Howard

Thread: Possible causing my work being snatched out whilst cutting
12/12/2019 20:46:54

A 4 Jaw will allow you to bring work absolutely on centre, more accurately than a 3 Jaw.

There are lots of places in books detailing how to centre work in the 4 jaw

There was an article in MEW some time ago, saying how to centralise work in a 4 Jaw.

The thing to remember is that you adjust the diametrically opposed jaws by half the run out shown on the DTI. You keep on checking and adjusting until the run out diminishes to whatever figure you consider acceptable.

(Often half a thou or less Total Indicator Reading is obtainable )

Practice will make perfect

Howard

Thread: ML1 Worn Saddle adjustment
12/12/2019 20:33:29

As a "quick and nasty", baked bean tins seem to be made from tin plate which is about 0.010" thick.

It might be worth trying different types of tin, such as sardine tins, in case they are any thinner, or thicker.

Cooking foil is probably only about 0.001" thick, and is probably not going to be long lasting, but might do as a short term fine tune.

Do make a centre height gauge. We are not on piece work, but it will save time and frustration in setting tools.

Glad to see that you are up and running, and climbing the learning curve. Nothing succeeds like success. Every job that you do will increase your confidence and experience..

If you can find a couple more 20T changewheels, get them. To get the finest feed, you need three.

One from a ML7 will be OK, once you have drilled a 3/32 hole into one side of it for the driving pin. The bore and width are the same; as are the DP and Pressure Angle

Not long ago, I did this with an ex ML7 60T gear, so that a chap could set up a 20:60/20:65/20:60 gear train.

This gave a feed of 0.0043"/rev as a fine feed, using the Leadscrew. The 65T needed to be on the middle stud to avoid a clash between the two 20:60 meshes..

One other job for the "Round Tuit" might be to make a mandrel handle. This will be handy when you come to cut threads, even with Taps or Dies. It will allow you to turn the Chuck slowly (Ideal when cutting up to a shoulder )

Making it will involve some plain turning, a couple of short tapers, and two external, and two internal screw threads. These need only be 1/4 BSF, 1/4 UNF or M6.  1/4 BSF would be ideal to keep in with the rest of the Whit form threads on the lathe.

A bit of hacksawing and filing will be required, but nothing too complicated.

PM me with an E mail address, and I'll send a picture of the one that I made for a ML4

Howard

Edited By Howard Lewis on 12/12/2019 20:36:00 Fat Fingers!

Edited By Howard Lewis on 12/12/2019 20:37:00

Thread: Plumbing question
11/12/2019 13:26:50

For the same pressure differential between inlet and outlet, the limit on flow will, be the smaller pipe.

The longer the small diameter section is, the more the flow will decrease, because of the friction with the pipe wall. This will apply to all fluids.

If a gas is at pressure at the inlet to the minor diameter, and there is minimal back pressure at the outlet, the gas will expand, decrease in temperature. If it expands, the volume will increase.

The drop in temperature during expansion is used to liquify gases, reducing it to below its critical temperature, where recompression can liquify it.

Witness the nozzle of a CO2 fire extinguisher, which will become coated with "frost", because of the drop in temperature, condensing and freezing moisture in the surrounding air.

Gases will behave differently, depending on whether they are above or below the critical temperature, and not like liquids which are only VERY slightly compressible, when subjected to high pressures.

Howard. .

Thread: ML1 Worn Saddle adjustment
11/12/2019 13:00:07

Chris,

Sparey's book is written predominantly with the Myford ML7 in mind, but that is the detail.

The principles will apply to any lathe.

Others worth considering are Ian Bradley's "The Amateur's Workshop" and Tubal Cain's "Model Engineering Handbook"

They are all filled with useful information, especially Tubal Cain's book. As you get further into the hobby, you will find The Workshop Practice series to be very useful.

The ML series machines , differ in centre height - 3.125 for the early models ( ML 1 and 2 ) and 3.5 for the later models, with the "higher" numbers denoting a greater centre distance. They all date from just before WW2 and production ceased in the mid 40s The ML7 came out in about 1947.

Like all machines of that age, wear and abuse will be apparent, not to mention what we would regard as peculiar foibles, and facilities which we now take for granted, will be absent.

Having said that, within the limitations of design, age and abuse, they are still capable of producing good work.

Like all machines, careful adjustment can bring about huge improvements in performance.

Keep at it!

Howard

Thread: Run outs
11/12/2019 12:22:48

If you are turning two or more diameters without disturbing the workpiece, run out will not matter. The diameters that you turn will all be concentric about the centreline.

If the workpiece is moved, then run out may well become a significant factor.

It all depends whether your form of model engineering is making things, or chasing microns.

Howard

Thread: Plumbing question
11/12/2019 12:14:16

Folks, are we not making mountains out of molehills?

The theoretical discussions are interesting, but do not do much to help the OP. The effects of turbulence at the change of section may be interesting, but are hardly vital in carrying a small volume of water down a short pipe, as the case in point.. There have already been references to Rocket Science, which this is not.

We do not need a dissertation on the change of viscosity of water with temperature..

The OP was asking about a pipe between the tender and the locomotive.

The pressure available to promote flow is going to be of the order of a few inches of water, or probably less than 200 mm.

The pressure differential may be increased by the sub atmospheric effects of the injector that it feeds.

But basically, it all comes back to "Will a 1/4" pipe reduce the flow through a 3/8" pipe"?

The simple answer, in these circumstances is a common sense "YES".

As the late Rudi Mischetlager used to say "Common sense is not that common"

Remember the motto of the amateur radio world, KISS, "Keep It Simple Stupid"

Howard

Thread: ML7 questions
11/12/2019 11:59:23

I found that the Myford oil gun, was a scatter gun, lubricating everything except what was needed.

I bought a Reilang. Relatively more expensive than the Myford article, but the difference is that it puts oil where you want it, with almost no leakage, and will work in almost any position.

It has been a good investment, thoroughly recommend it.

With regard to spanners, it is possible to tighten / slacken hardware with a slightly oversize open end spanner, by inserting a packer of the correct size between one of the jaws and the flat of the hexagon, or square.

better to use the correct size, but sometimes, the devil drives, where needs must!

Howard

Thread: Run outs
10/12/2019 22:43:43

It has been suggested on another thread, that the concentricity of ER chucks/collets can improve if the clamp nut is tightened harder.

Have never bothered to check, but might be worth checking?

Cleanliness of chuck and collet is taken to be the case.

Howard

Thread: my first lathe.
10/12/2019 22:34:49

HSS is probably best for a newbie. Throw away tips are intended to run at high speeds and feeds are such that the metal is heated to the point of being softened. This is useful for turning hardened materials, where HSS will not cope,

Start by taking small cuts. with light feeds. Deep cuts and higher feed rates, (for roughing ) can come later when you have more experience.

Find a local Model Engineering club if you can, and join. You will get advice and help, face to face, and probably hands on, one to one, either on your machine, or someone else's.

Exact clearance angles are probably not too vital. Most folk will grind a knife tool with about 5 - 10 degrees clearance angles. (Cue howls from the perfectionists! )

It is unlikely that you will get on well with HSS tools with negative rake. I sometimes (mostly through sheer idleness ), use zero top rake.Too great a top rake will weaken the tool and shorten the life between regrinding. Softer materials, such as Aluminium, will accept greater top rakes than hard material.

Various books will show how to grind tools.

For a better surface finish, a radius on the edge of the tool can be stoned d or ground on. Too large a radius can induce chatter.

The most important thing is to ensure that the cutting edge is on the centre height of the job. Too high and the tool rubs instead of cutting, too low and it does not cut properly, and effectively has much too great clearance.

Both these faults will meant the tool does not cut to the centre, leaving a pip in the middle when facing.

If you do not yet have one, make a centre height gauge, and set the tool to it, always. There are various ways of finding the centre height. As a starting point, keep shimming a freshly ground tool until a facing cut leaves no pip in the middle. The set your gauge to that. All other tools can then be set to the gauge.

For tools in the front toolpost, the blade of the gauge is above the tool. Subsequent tools are then shimmed until they just make contact with the underside of the blade.

When / if you fit a rear toolpost, the gauge will need a second blade fitting below the original one. For this, fit the lower blade, loosely, set the upper blade, to the centre height cutting tool, again, The lower blade can then be brought up to contact the upper blade and locked in position. You are then ready to set tools in either the front or rear toolpost to the centre height. Tools in the rear toolpost will be mounted inverted, with the cutting edge facing down, hence the use of the upper surface of the lower blade.

You will make mistakes, but you will learn from them

Howard

Thread: Noise Isolating Platform
10/12/2019 21:49:35

I won't make the obvious comment about bit being a load of, but decoupling the source of vibration from the surroundings will reduce transmission greatly over a wide range of frequencies.

A very nice solution, using easily obtainable materials.

Just wonder how many would be needed for a 300Kg machine? i e what is the load bearing capacity of a tennis ball

Howard

Thread: Rotary Table
10/12/2019 21:44:51

Have you a chart giving the Turns and Holes for the various numbers of divisions with your Rotary Table?

If the gear ratio is 72:1, then the chart should call for one turn of the handle for each of 72 divisions.

If it is not 72:1, then whatever number of divisions that calls for one turn of the handle will be the gear ratio.

As an example; a Vertex HV6, calls for 1 turn for 90 divisions, so has a 90:1 ratio.

Otherwise, you will need to count how many turns of the handle are needed to rotate then table by a set number of degrees, such 90 degrees., and multiply by 4.

22.5 turns for a quarter turn means 90:1. 18 turns would mean 72:1, and so on. To be absolutely certain, keep counting the turns until the Zero graduation returns to the datum point. Bit of a PITA, but necessary to find the ratio. The higher the ratio the greater then resolution.

Mounting a set of division plates meant for a table with one ratio, onto one with a different ratio will mean that the chart supplied with the table will not apply, and a calculator or a spreadsheet will be needed, to arrive at the turns / holes for a given number of divisions. It can be done. When errors were evident in the Vertex HV6 chart, a spreadsheet brought to light other errors and omissions, so in the end it was time well spent.

Howard

Thread: BSP vs NPT vs "PT"
10/12/2019 21:25:08

Correct Eddy!

NPT will be 60 degree thread form, while BSP will be 55 degree Whitworth thread form; as as you now know the pitch also differs.

By the sound of it you need more than just three for one solenoid valve? You would need a 1/8 NPT die (assumes that the valves have female ports ) and a 1/8 BSP tap to produce the female part of the adaptor.

Otherwise, i would advocate getting some hexagon brass bar and making your own adaptors, unless you want to go into mass production?

Howard

Thread: ML1 Worn Saddle adjustment
09/12/2019 18:51:08

Comments.

The Myford M Series have dovetail beds, so wear on the dovetails may be less easy to recover, than on the flat top of the bed.

So your check with a straight edge needs to include the dovetails, (The rear dovetail may be even more difficult! ) as well as the flat top of the bed.

There will be backlash between the pinion and the rack. This is the normal method of moving the saddle, manually. Which is what you would do most of the time. In any case it is quicker than winding along with the Leadscrew, which will need 8 turns to advance the Saddle by an inch

The half nuts will be engaged with the Leadscrew if you wish to set up the change gears to provide a power feed for turning, to cut screwthreads, or to advance the Saddle by a measured distance.

For what my advice is worth, I would check one thing at a time, staring with the rear dovetail; then the front dovetail, and then the flat top of the bed, correcting the wear in each feature.

But remember that you will have difficulty putting on metal, if you remove too much. So proceed VERY carefully.

My first purchases would be a tin of Micrometer blue, and a good 12 " straight edge, plus laying in a good stock of clean rag, and Swarfega, with which to clean my. hands.

SLOWLY SLOWLY CATCHEE MONKEE!

When you happy with the bed, then clamp an accurate bar in the chuck, (1/2" minimum dia Silver Steel possibly ) and check that the Headstock is aligned with the bed. Unless your lathe is a very early one with a cast in Headstock, it should be possible to correct any misalignment by slackeinng the 1/4 BSF nuts that hold the Headstock to the bed.

Once that has been done, fit centres, and with a properly centre drilled bar and starting checking the Tailstock for alignment in first the horizontal plane, and then in the vertical plane. Adjusting for Zero deflection horizontally should be fairly easy, using the 1/4 BSW adjuster on the far side of the Tailstock. Recheck after locking with the nut!

If the centres are out vertically, you may have to scrape the underside of the Tailstock to bring the centres into alignment. If the tailstock centre is low, you will need to find some means of adding shims.

Again,BE CAREFUL, not to make matters worse! You do want a Tailstock barrel that points towards the sky, or the floor.

Either way, you will need to check that when the vertical alignment is correct, that the horizontal has not been changed since first set up.

Once you have got the lathe into alignment with as little backlash as possible, you should have a useable, mand useful, machine, even if it has foibles compared to a modern machine.

Howard

Thread: Newby machine help please
09/12/2019 18:10:26

Two comments Sorry to be depressive.

To calculate the DP of the gears.

OD = (N+2 ) / DP So, for the 60T: 62 / 5.647 = 10.979. Which, as Russel said looks like 11DP. An odd number in both ways!

Since the dimensions form the lathe are all quoted in Imperial, I think that we can discount the gears as being Module types Plus the 6oT with an OD of 143mm would be a 2.3 module, which seems to be even more odd.

May I suggest rechecking the tooth count and the OD, in case the gear is actually a more normal DP?

If a complete set contains 12 change gears, and you have only 3, buying the remaining 9 is going to be expensive. Possibly as much, or even more, than you paid for the lathe. And then, IF they are correct width, they will need to be modified to provide the correct bore and to cut the keyway.

My suggestion would be to see if you can find a Model Engineering Society close by, with a kind member who would be prepared to buy cutters, (more than one is likely to be needed, probably three without checking, so you are looking at £60 -70 as a starting point ) and to cut you as set of gears,

Either way, whether or not the gears are a strange DP, it is going to cost a bit!

Howard

Thread: Case Hardening
05/12/2019 17:57:15

My understanding of casehardening has always been that by heating a low carbon steel in a carbon rich environment, the carbon is absorbed into the surface of the steel. Thus, locally, the metal becomes a steel with a higher carbon content, and so capable of being heat treated to harden it.

Salt baths used for case hardening are often Cyanide based..

Nitriding is a process where the steel is heated in a Nitrogen rich environment, such as Ammonia, or a Nitrogen rich compound. This does harden the steel, and also improves its fatigue resistance; hence its use for crankshafts, and other components subjected to fluctuating loads.

Tufftriding is a salt bath version of Nitriding, and, again, is popular for Crankshafts.

What is important is remove the compound layer, which is EXTREMELY hard, but very friable.; I have seen it crumble off a crankshaft almost like grit.. If the compound layer is not removed, this will result in surface degrading in an exponential fashion, which does nothing for the shaft or the bearings in which it runs.

In all cases, the depth of case is determined by the time of exposure. Crankshafts were Nitrided for twenty or sixty hours, depending upon the use to which the engine was going to be put.

Howard

Thread: More evidence that the world has gone mad!
04/12/2019 16:51:00

If you are sufficiently determined, you can take offence at anything!

Some people will say NO before they know what the question is. Why don't they go get a life, like the rest of us?

(Maybe taking offence IS their life )

Howard

Thread: Lathe annoying 50Hz hum
04/12/2019 16:15:34

Anything will oscillate if the exciting force is great enough. The object will oscillate at the frequency of the exciting force, but not necessarily be in resonance.

Everything has a natural frequency, it will only go into resonance if the exciting frequency coincides with the natural frequency.

As the frequency of the exciting force approaches the resonant frequency, the amplitude of vibration will increase dramatically, some times with fatal results at resonance.

This is known as the Dynamic Magnifier effect. If the equipment survives, the amplitude will decrease equally rapidly as the exciting force moves away from the resonant frequency.

Notice how, pushing a child on a swing can send them higher and higher, for little effort if the push is applied at the resonant frequency of the "child + swing" system. The exciting pulse arrives at the same time as the natural movement of the swing. Applying the force 180 degrees out of phase will bring things to a halt very quickly.

Racing motorcycles, and naturally aspirated engines sometimes make use of this. Indeed the two stroke engine often used an exhaust pipe tuned to resonate at the frequency of the port opening to scavenge the cylinder.

Similar tuning can be used to provide ram, for induction, at certain speeds, but not over a wide speed band.

Motorcycle racers used to tune the exhaust to "get on the meg"aphone. In the same way that car engines would "get on the cam" Being open handed, nature will ensure that if you halve or double the speed, the effect will be not negative back pressure, but positive, stuffing the exhaust back into the cylinder!

It was said that a steel (as opposed to air ) sprung lorry would overturn if it passed through the average UK roundabout at 22 mph. The rate at which the body rolled would be the same as natural frequency of the suspension, so that the roll increased so rapidly as to turn the lorry over.

Air suspension, which stiffens as load is applied, has a variable natural frequency, and so is less prone to such problems.

Howard

Thread: Cracking a bolt
04/12/2019 15:47:40

The bolt or nut comes loose with a "crack" because you are overcoming the static friction.

If you need to measure the torque applied when the fixing was tightened.

Scribe a line across the flat of the fixing and the area around it.

Slacken the fixing

Retighten until the marks align again. The torque needed to do this is the torque originally applied.

Yield tightening is used to maximise the efficiency of the fastener. (A 8 mm fastener in yield may replace a torque tightened 10 mm, and provide a more consistent elastic load in the fasteners.

Not all yield tightened fixings are single use.

Torque is one means of applying (not very accurately ), the load in a fastener.

A more accurate method is to tighten until a required extension is obtained. This was used for the Big End Bolts in Rolls Royce C Range engines, so was probably a carry over from aircraft practice. The bolts had reduced diameter shanks to provide uniform strength along the length.

When commissioning what was, at the time, the world's largest multispindle yield tightening machine, we found that we could retighten W range 1/2 UNF bolts up to nine times before failure. We thought that reusing six times would be as much as could be safe.

This is NOT advising this for all fixings. It will depend upon the material, and the dimensions of the particular fixings, as well how far into yield the fixing is taken.

Howard

Edited By Howard Lewis on 04/12/2019 15:49:48

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