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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: Torque wrench testing
16/09/2015 01:55:07

Angular tightening implies tightening to yield,

This technique involves tightening to an initial "snug" torque followed by a known angular rotation which produces a fairly consistent axial load to just above the yield point of the material. This is now a standard aftermarket means of tightening to yield.

This means that the fastener takes on a permanent extension, and uses the fastener most efficiently, but is why some manufacturers insist that the fasteners are not re used.

Many years ago whilst involved in commissioning, what was at the time, the worlds largest multi spindle yield tightening machine, we spent several months repeatedly checking each of the 32 spindles. The end result was that W range, 1/2 UNF bolts were put into yield with a tensile load of 9 tons, and took on a permanent stretch of 0.001" at each tightening. It was considered that these fasteners could be reused, before needing replacement. During the trials, we found, like other manufacturers, that the lubrication needed to be controlled; although not as closely as our suppliers first feared).

Tightening to a torque, or by torque plus angle, whilst departing from the specified lubrication conditions, or the fastener material specification, will cause problems, either in too low a clamp load, or by overloading the fastener.

The load in the fastener can be measured using a load cell. This is effectively the same as fitting strain gauges to the fastener, since they are contained within the load cell.

On very large fasteners, where torques would be so large as to be difficult, or impossible, to apply, it is common practice to use hydraulic nuts, such as "Pilgrim" nuts. Here the load is applied by a hydraulic pressure calculated on the basis of the dimensions of the nut, to extend the nut to apply the required axial load, and then maintained by tightening another nut onto it.

Howard

Thread: Where to position the steam outlet on a horizontal boiler ?
16/09/2015 00:28:28

Not being a steam man, am probably treading where angels would not.

Taking steam directly above the boiling water risks picking up water droplets? (G J Churchward went to lot of trouble on his loco boilers to minimise this. Admittedly, being on a loco everything did get shaken about)

Also, to help dry the outgoing steam, how about doing what Mamod did on their boilers? Which was to run the steam offtake pipe down under the boiler, through the flame and up again on the other side. Presumably this helped to dry the steam a little (Although, MANY years ago, despite this, my engine used to dribble hot water out the cylinder quite liberally!) Trouble with this is hat the, hopefully, higher steam temperature will soften the flexible tubing even more!

Howard

Thread: Leadscrew cover/guard
16/09/2015 00:13:58

Later versions of my Asian lathe had volute spring type covers over the leadscrew. Unfortunately, these look to require a lot of stripping to fit, so have refrained from retrofitting to mine.

From time to time, I move the saddle to the Tailstock end of the bed, and engage the drive to the leadscrew, and then hold an old tooth brush against the leadscrew. Ceertainly do this before any screwcutting, to minimise risk of carrying rubbish into the halfnuts. If the direction of rotation of the screw has been chosen correctly, the rubbish, (swarf/dust/grease) gets worked up to the headstock end and out of the thread.

Old toothbrushes are useful for this sort of work, as well as cleaning taps, dies or drills after use. They are cheap, and disposable, although mine usually will have been cleaned a few times in white spirit before being discarded finally.

Not tight, just careful y'ken!

Howard

Thread: Cutting threads with die
15/09/2015 23:26:11

Hear hear! to advocates of Zeus Charts. They are invaluable.

I am still using the ones bought back in 1958, (They contain info that is lacking from some of the later versions that I have). ANY issue is good for details of various threads, (Dias, Core Dias, pitches, thread depths etc) and Tapping drills.

Info is available in seconds, saving ages searching or enquiring.

Unfortunately, they don't deal with M.E. threads, but Data Sheets that give those details are, or certainly were, available.

If not this is a good place to ask for someone to provide the details of an unusual thread. Someone will have come across it, no doubt and will tell you what you need to know.

FWIW, Beware, (if not already known), BSP and NPT threads are not interchangeable; different pitches and thread forms. Similarly, British Standard Brass is Whit form, Cycle is 60 degree, although both are 26 tpi.

Graunch at your peril!

Howard

Thread: Hello and the first of many questions
31/08/2015 11:50:53

If you did succeed in reaming out the mandrel to a larger size, (won't be much anyway) you will find that 2MT equipment then goes in deeper (You won't make it to 3MT, even if you can cut the mandrel) and this could cause you problems with some tooling.

You will have gathered that the general advice is "Don't do it".

I was equally, if not more, frustrated, by the small size of bar that would pas through the mandrel, so sold my ML7 and bought a larger lathe.

If you want to stick with a Myford, you need one of the later models, Super 7 Sigma, with a 4MT mandrel

Going from the sublime to the gorblimey, my current lathe has a 5MT mandrel!

Howard

Thread: Machine a head of a bolt
31/08/2015 11:37:24

At the risk of repeating what may already have been said, a few thoughts.

If the pivot is subject to high loads, as it would be on a Moto Cross bike; the material ought to be hardened, (Probably case hardening would suffice. You can buy case hardening compounds for home use. You will need a fairly potent blowtorch. S W M B O will be unlikely to approve use of the oven or gas rings on the cooker for heating to red heat!).

The original bolt was washer faced, so with a Milling attachment, you could start with bar the diameter of the original "washer". You then mill off each side an amount equal to half the difference between the Washer diameter and the Across Flats size of the original hexagon, indexing and repeating until you have a replica hexagon. You will have an end mill in the chuck, so the workpiece will need to be indexed in the milling vice using a protractor, (if not previously marked out) using each cut as the angular datum. The socket or spanner to be used for tightening makes a useful gauge, but don't forget to deburr and very slightly break the corners of the job before checking with the "gauge".

The suggestion to thread both ends, and to use nuts and washers seems to be a good one, if feasible. As is to use castellated nuts and cross drill and split pin, (or use Nyloc nuts on longer threads . Nylon is hygroscopic, so eventually the nylon will likely cause rusting of the threads under it , unless waterproffed with a fingerful or so of grease, afterwards)

For lubrication, I would advocate drilling and tapping one end for a grease nipple, and cross drilling, (at both ends if need be) to meet the axial drilling, so as to take lubricant into the bearing areas. Don't make the drillings too small, 4mm is less likely to clog than 3, but don't go to large and weaken the pivot! The grease oozing out at each end will also waterproof the assembly, as well as reducing wear.

Hope this is some help, if only food for thought

Howard

Thread: New lathe arrived today : The ongoing saga
31/08/2015 11:09:58

As has already been said, you don't have to have an Aluminium mandrel for an Aluminium component. In fact it would be better not do that. If the Al flywheel should slip on an Al mandrel, there could be local welding, and then in worst case, the two could be welded together, and only separable with force. Even if the worst case did not happen, there could still be scoring damage in the bore of the flywheel.

Mild steel should be easy to turn, FAR easier than stainless. Just don't try taking deep cuts.

Ensure that the tools are sharp, and set at centre height, and don't try to take deep cuts, "Slowly, slowly, catchee monkey".

Cut up tins, or coke cans for shims to adjust the tool height. Faced with a choice of a thou or two above or below centre height, go below. This will give increased front clearance , whereas above the tool will not cut properly, and merely rub.

High Speed Steel tools will cope better with small cuts than disposable tip Tungsten carbide tips.

(But this then gets you into grinding tools, which you will need to learn, eventually)

The advice on parting off is all good. Lubrication can help. For Al, kerosene is a good lubricant. Occasionally withdraw the tool to clear swarf, and when cutting, keep a small but steady forward feed. Don't let the tool rub. Don't force it, that will be likely cause dig ins, possibly a broken tool, even a scrap workpiece.

If there is a build up on the edge of any tool, stop and remove it. Lubrication helps to prevent this.

If you suffer chatter with any tool, reduced speed often helps, as will lubrication, sometimes.

If you decide to make split mandrels, remember that the central screw(s) will need to have the head turned to a taper so that the mandrel is expanded as the screw is tightened. Ten degrees (Five degrees Topslide offset) should be enough. My advice F WI W is to use as large a diameter screw , as possible, within reason.

You'd be pretty sick to have a M3 shear off, when a M4 or M5 wouldn't have!

Since you are bolting down the lathe, the bed needs to be free from twist. If the bed is twisted, it will not be possible to turn parallel over any length. (It won't turn parallel over a short length, but the error over a short distance will barely be detectable). If bolting to a wooden bench, my advice would be to have a piece of 3mm steel under the chip tray, to spread the load, before starting to remove any twist.

Since you are cutting dry, the level from Headstock to Tailstock does not really matter, but it is important that the front to back level is the same at both ends.

If you can get hold of a copy of the Myford Series 7 Manual it sets out how to remove twist from the lathe bed.(see page 42; although the same info will be available elsewhere, for sure). Turning a holding down nut just a flat can make a difference!

Do take up offers of help, you will learn, by seeing as well as hearing of how others do it.

Good luck! You'll get there in the end, but try to learn and make your mistakes on material. that you are prepared to scrap, not raw castings for you next project!

An undersize bar originally meant to be 6mm can always be raw material for a 5mm or 4mm piece.

(But I am an inveterate hoarder. "It'll come in useful one day"

Experience is what allows you to recognise the mistake, the next time that you make it.

Keep trying.

Howard

Thread: full size Dykes piston rings
28/08/2015 21:47:42

Dykes rings are a really venerable design.

Modern materials and processes should make them perform even better than when they were first invented.

Before I retired nearly twelve years ago, it had been common practice to have compression rings narrower than the groove depth so that they were gas backed. We found that the ring gap had a big effect on blowby..

The secret was to have a cold fitted gap so small that, when hot (full load rated speed coditions) the ring ends did not butt together. If they did, you were certain to have bore damage and broken rings.

The blowby tended to improve as the engine bedded in, as the rings lapped themselves to the faces of the groove.

Quite a contrast to have a three ring pack that performed much better than the five ring packs of the sixties and seventies, in terms of both blow by and oil control. The better technology , based on experiences, made that possible.

Some "new" things actually ARE better, not just in the minds of the marketing men.

Howard

Thread: New lathe arrived today : The ongoing saga
28/08/2015 19:30:58

Welcome!

Once you get the hang of things, you will have HOURS of pleasure.

As already said, gain experience on "scrap" metal, rather than expensive castings, or metal of which you have a very finite supply. It is better to learn on material which you are reasonably happy to bin, rather than a shaft for some model or tool for which you have paid highly.

If you can, join a Model Engineering Club, that way you should have first hand access to a lot of experience and help.

Direction of Rotation: ANTI Clockwise looking at the Chuck. (There are exceptions to this but these need not bother you now. When the time comes, you will probably have the experience to know how and why)

Learn how to turn the handwheels at a more or less constant rate, using both hands (a bit akin to pulling a rope hand over hand, one hand taking over from the other)

As you face inwards, the cutting speed will decrease, so the surface finish will probably vary. You will need to adjust your rate of feed to accomodate this.

As you traverse along the bed, the cutting speed will remain constant (unless you are cutting into a taper to bring it parallel).

3 Jaw self centering chucks do not hold work absolutely concentric. A good one will be within about 0.003 inches (say 0.01mm) Total Indicator Reading. As someone has already said, you turn the scroll until you can just see the start coming to the slot for No 1. Slot in jaw 1. Turn scroll slightly. and jaw will start to move in. Stop and turn chuck so that you can see down the slot for No.2.. Turn scroll until start comes into view. Fit Jaw 2, turn scroll until jaw moves in. Repeat for jaw 3..

Always fit tools at centre height, NEVER above. With minimal overhang, if the tool is ground to the correct angle, and meets the work with the correct clearance angle, if it chatters, reduce speed, and/ or feed rate.

Making a centre height gauge might be a time saver, and a useful exercise to gain experience. It can locate on the bed, or on the Cross slide, but obviously can only suit one or the other position, not both. The final operation having made one, (before fitting and setting the blade)is to hold the pillar in the chuck and face the underside of the base, to ensure that the pillar will will be vertical when in place for use.

You have a small lathe, so the manual will probably warn against taking cuts more than 0.25mm (0.010"

The toolpost guard came off my lathe VERY soon after it arrived, but I do have a flat acrylic guard that sits on a pillar on a pot magnet, that gets used from time to time. Hot swarf down the front of your shirt is an acquired taste, but not my recommendation.

The chuck guard possibly operates the microswitch by a face cam on the shaft carrying the guard. If you want to work without the guard (BE careful! It is there for your safety) you may get away with removing the guard, but leaving the shaft, although you are liable to have the foul problem still.

On my larger lathe, I cut the shaft and made up a sleeve to join together the two halves. When it gets in the way,as it does sometimes, I remove the sleeve and guard, leaving just the short end of the shaft. BUT I don't do that when the chuck jaws jut outside the chuck body, and keep well away from the jaws on the face of the chuck.

The usual recommended lubricant for Aluminium is kerosene, it will lessen the tendency to weld to the tool, and improve the finish. For a good finish, the tool should be sharp, and if in any doubt, run slower than normal, with a fine cut and fine feed.

White spirit may be an acceptable substitute for kerosene; try it?

When you are more proficient, you can start worrying about levelling the lathe, to minimise twist in the bed.  But that comes later!

Hope that all my ramblings will be of some help.

Howard

 

 

Edited By Howard Lewis on 28/08/2015 19:36:19

Thread: Weight and transportability of a Myford lathe
28/08/2015 18:44:16

When i bought my secondhand ML7, two of us lifted into the back of a Renault 16, (so that tells you how long ago).

Since then Two of us (males - me + not he same chap each time) have lifted the machine on four or five occasions.

Last time was 12 years ago, when I sold it, and helped install it in the new home.

The only thing with a ML7 with motor is that the headstock end is WAY off balance, so holding the motor is a job for one of your hands whilst the other supports the headstock. But it can be lifted and carried. Obviously, if you can load it onto a truck of some sort , moving distances is easier than carrying (until you find it too wide to fit through the doorway!)

A Norton box may help the balance, but will make the headstock end heavier.

If you can borrow / hire a small crane, removing the chuck, moving tailstock away from the chuck as far as possible , before slinging and lifting (fitting a steady there as well may help) will help balance end to end. But it will be desperate to capsize, so do keep at least one hand on, or an additional ratchet strap or something, to stabilise it.

Do be careful lifting from/ or lowering to, a low starting point; osteopaths get rich that way.

Summary: as long as you are both reasonably fit, awkward but not impossible.

Yes do protect the car floor with hardboard (minimum) or ply is better.

When in the final position, DO level carefully. Myford beds are not rigid, so you need to be very careful fixing down so that there is no twist between headstock and tailstock. Won't matter if the headstock is higher or lower than the tailstock, but any twist and it will never turn parallel. Even an extra nip on a holding down bolt will affect the twist.

Have hours of fun afterwards!

Howard

Thread: Buying a Lathe Advice
28/07/2015 22:01:11

A lot of valid comments on this. Now for a few more!

What lathe you choose depends on what you weant to do with it, (and looking to the future; because your horizons will expand as you gain confidence)

Years ago at the Worthing M E S Open Day, someone said "You can do small work on a big lathe, but you can't do big work on a small lathe"

An ex Industry lathe will have been worked hard for most of the time. It was bought to work and earn money for as much of the time, as possible.

An ex College/School lathe will not have seen as much use, but will have been abused. The Toolpost will probably have hit the chuck a few times, or the auto traverse abused and the shear pin been asked to do its job.

A new modern Eastern lathe may well have hardened bedways. Imperial dials/leadscrews may well be harder to find, but recent bikes will be metric anyway.

You may be able to find a fairly recent belt driven "Amateur" lathe in reasonable condition, not having been asked to take deep cuts at high feed rates, for days on end.

(Here, I am thinking terms of Warco BH600, Warco BH900, Chester Craftsman or possibly an Engineers ToolRoom BL12/24) All these are similar, with belt drive headstocks, with power cross feed from a Norton box, so less messing about with changewheels, to cut a wide variety of threads. These have a MT5 mandrel, so will pass upto 38mm. (One of the reasons, that I changed from a Myford ML7)

Geared Head models will be noisier than belt driven.

Older machines, even if mechanically good, may not have the speed range to get the best use from indexable carbide tools.

If you consider buying a second hand machine, with a three phase motor, it may be cheaper to buy an inverter than to a new single phase motor. Luxury, is to have a dual voltage three phase motor, with Variable Spee Drive via an Invertor. (My BL12/24 has a 1.5hp motor with VFD and I rarely find the need to take off more then 0.100" a side in one cut)

Belt drive has one advantage, the belt will slip if everything really jams. Plus belts are cheaper and quicker to replace than broken gears - if you can get them.

Ultimately, as Neil says, it is down to personal choice, and budget.

As an Apprentice, I fell in love with a 21" swing Dean Smith and Grace, but have not space or money for one, so my coat is cut according to my cloth.

Howard

Thread: Brass plug
10/07/2015 12:40:40

Purely for the record, British Standard Brass threads are 26 tpi, Whit form (55 degree)

Cycle Threads are 26 tpi, but 60 degree form.

Couldn't understand why there were two sorts of 26tpi threads, so went and found what the difference was.

As to a Cap removal tool; how about turning a recess to fit snugly around the cap and then cross drill at the appropriate distance and fit a silver steel pin of the same size as the slot in the cap? To be really precise, make and fit a square or rectangular section pin of a size to fit the screw driver slot.

The rest of the tool can have a hexagon for driving with a socket, or be cross drilled for a tommy bar drive, whilst you press down to stop it jumping out of the slot.

Hope that this is some help, or starts a train of thought.

Howard

Edited By Howard Lewis on 10/07/2015 12:42:45

Thread: What compressor
10/07/2015 12:28:51

All direct drive compressors are noisy!

Belt drive compressors are quieter, but tend to only come in larger sizes, both CFM and reservoir capacity

Diaphragm compressors are quiet, but costly.

If you can stand the noise, I would suggest a 3hp, (probably a V twin) that can be run off a 13 Amp domestic socket.

Even with a 5 or 10 psi regulated offtake, the compressor is likely to cycle on and off fairly frequently, and the sort of units that we buy are not intended for high duty cycles. hence the advice to buy a high delivery machine with a large capacity reservoir.

When I bought my HPC from a local compressor specialist, the advice was to drain down after every use, and to leave the drain open, so that any remaining moisture can escape.

When you drain down, don't be surprised if the air stops escaping with a reading still on the pressure gauge.

The tap will probably have frozen up, with the expanding air bringing the temperature below freezing. Left to its own devices, will thaw and dump the rest of the air and most of the moisture.

Howard

Thread: 2MT REVOLVING CENTRE
02/07/2015 13:59:48

Years ago, I bought a cheap 2MT revolving centre. The bearings must have been duff as using it seemed to result in more vibration and chatter than a greased dead centre.

I have often thought about using a Boring Head in the Tailstock for taper Turning, to avoid upsetting the Tailstock alignment. However, the travel must be absolutely horizontal, or the offset will not be accurate, and since the axis of the workpiece will depart from the lathe axis, in the vertical plane, over its length, cutting problems could result.

If decent bearings are available, it ought to be possible to make a small revolving centre with a shank to fit into the Boring Head. Sounds like another "Round Tuit" job has arisen!

Howard

Thread: Wabeco 2000/3000 Lathes
02/07/2015 13:33:23

For anyone wanting to see or buy a Wabeco machine in U.K., Pro machine Tools are located at :

Unit 17

Station Road Business Park

Barnack, (between Peterborough and Stamford)

PE9 3DW,

There is an advert on the inside of the front cover of M.E.W. 230, giving the above address, Telephone No. and E mail address.

Usual disclaimer, having once visited, but never having been a customer.

H T H

Howard

Thread: Lathe design not keeping up
23/06/2015 08:36:03

Toothed belts provide a sufficiently reliable drive for Camshafts and Fuel Injection Pumps (which really do give the belt some stick!) so could be a good way to go.

For anyone who wants to quieten their lathe, without changing to belt drives, they could try what was done to reduce noise on Diesel engines.

Instead of the front pulley being solid, it was changed to spoked. This reduced the area that could transmit noise to the surroundings

Since my Far Eastern lathe has a similar gear layout to that shown by John, maybe the big idler (120/127T) should be removed and have some large holes drilled/bored in it?

There are times when it "rings" at higher speeds.

Another alternative, which might improve finish or thread pitch consistency, would be to bolt on a lot of lead sheets. This would dampen the sound ( Sumps consisting of a sheet steel/lead/sheet steel sandwich were effective, but heavy) and provide a flywheel effect to give a drive with less instantaneous speed variation.

Just a thought.

Howard

Thread: swarf!
23/06/2015 08:19:46

I change into/out of a VERY old pair of shoes in the utility room. Heaven help me if I get caught around the house in them!

Yes, sometimes the bedroom carpet does glint in the sunlight, as does my "working" woolie. Have to give myself a quick rub down before going indoors. Made a Magnet Swarf Retrieval Tool (telescopic magnet in a copper tube) but no good for Ali or Brass.

The floor where I stand or walk, is covered with hard plastic mats, which let a lot of the swarf fall through (every so often they are pulled up to display the swarf and all the small items, nuts, washers, drills etc that have been dropped, and for cleaning). The swarf still gets EVERYWHERE else, though!

Howard

Thread: Hand cleaner
23/06/2015 08:07:02

Gave up using Barrier Cream, (not that it was not effective) but it it gripped any non rotating handle or socket extension, so that it rubbed the skin.

Often wear industrial gloves, but they are not waterproof, (so your hands can become soiled with dirt carried through in the oil/coolant) and eventually become soft and start to sag or get trapped between the workpiece and the jaw as the vice is tightened.

Washing Up Liquid is good, (with or without sugar/sawdust - never tried salt. NOT if you have a cut!) but dries out my skin, and having had Dermatitis, try to avoid using it. Still using original green Swarfega, IMO, better than the more expensive Orange version.

Howard

Thread: Help please with this oiler
23/06/2015 07:53:59

When I had a Myford, I found that the Myford gun supplied a lot of oil, all over the machine, including me, except where it should go.

A Reilang oil gun , fairly expensive, but it puts the oil through the ball oilers with minimal loss; and can generate quite a bit of pressure. Have never regretted buying it.

My BL12/24 (WArco BH600/Chester Craftsman lookalike) had an oiler for the power feed control that was inaccessible, right beneath the cross slide handwheel. In great trepidation, stripped off the control, removed the ball oiler (destroyed it in the process), plugged the original hole, and drilled another 6mm hole where it would be accessible, fitted a new ball oiler, and then reassembled.

For normal hydraulic grease nipples, i use an old CHEAP side lever grease gun with a flexible extension.

For Changewheels, I smear grease over as much as posible and rely on rotation to spread it to the other teeth.

Or one of the aerosol cans of chain/gear lubricant is even better.

Howard

Thread: lead screw bronze nut problem
15/06/2015 11:45:08

Hi Alan!

Am not a Hobbymat owner or user, but am a retired Mechanical Engineer, and fairly well equipped.

DON'T junk it until all avenues have been exhausted. (Was the Leadscrew hard/impossible to turn when you bought it? If so, this was probably why it was sold!)

In fixing it, you will learn a lot, and gain a great deal of satisfaction and confidence. AND you will have added quite a bit of value to it.

If all else fails, you could bring it to me, (about 40 miles south of Boston - Neil has my address, and we can arrange by E mail) and i will do whatever will help.

Howard

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