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: Clinging to the Past|
In"The Old Workshop" at The WaterWorks Museum is a treadle lathe.
So when the electrical power supply fails, it will still be possible to do some turning by the the light of an Aladdin or hurricane lamp, measuring with Micrometers or Vernier callipers!
Not much hope for me with my VFD, though!
|Thread: Jammed shaft key removal|
If the key is a woodruff key ( a semi circle ) one way of moving it is to tap on the extrememe end so that it rotates to bring the other end further out of the keyway.
File or stone off any burrs that you may ahve already produced.
1 This should "unstick" the key. If it moves, with a small flat ended punch may it be possible to rotate it even further, even to remove it completely.
(Before searching to se where it has fallen )
2 There should be more material which can be gripped. If it moves, but does not come out completely.
Don't hammer so hard that the key is "mushroomed", or even worse so that the shaft is bent!
If the worst comes to the worst, you can make a new key!
Turn a piece of bar to the OD of the Woodruff key, part it off slightly too long, for careful filing afterwards ) to the correct thickness, and then cut in half . Not actually, since you want to finish up with one semi circle, cut and file away from the centreline, to produce the Woodruff key that you want.
|Thread: cutting spur gears on a mill|
Purely pedantry, but a helical gear is not a herringbone gear.
It can be paired with a similar one of the opposite helix to produce a herringbone gear, with the Vee tooth pattern.which gives rise to the name.
A helical gear, by virtue of its helix angle produces an axial thrust on the shaft. By mounting a gear which is identical, but of opposite helix, the two end thrusts cancel out.
Skew gears are helical gears where the axes of the shafts carrying them are not parallel.
Engineering implies precision. An imprecise description may result in an answer to a question which wasn't asked, and cause confusion.
|Thread: Regrind a V8 Crankshaft|
Grinding crankshafts is a task that really involves knowing what you are doing, and having the equipment to do it properly..The grain of the wheel and the relative speeds of the work and grinding wheel have be held within fairly close limits.
If the primary surface finish is incorrect, the bearings will fail. Our spec was 16 u inch CLA MAXIMUM,
And secondary surface finish affects bearing life very greatly, if only by controlling the size of the leak path for the oil. The primary function of which is to cool, with lubrication as a secondary purpose. If the bearing temperature is too high the composition of the alloy of the bearing metal changes, and can lead to failure.
(On marine main propulsion engines main bearing temperatures are monitored more closely than oil pressure ).
At 18 CLA the bearings began to mark. At 22 CLA they failed and ruined the Con Rod, Block and Crank.
This provides a copious supply of fag paper thin blued steel, and decorates what is left of the block with sparking white metal!
Get the web radius wrong and a fatigue failure very soon follows..
Broaching of the bearing shells has to be very closely controlled, or that can be another cause for bearing failure.
Main and Con Rod bearings are very highly stressed by inertia loads, which exceed gas loads at high engine speeds, so things HAVE to be right!
Crankshaft grinding is like marriage, not an undertaking to entered into lightly!
Howard (This wireless keyboard can't keep up with even my slow typing speeds! )
Edited By Howard Lewis on 22/08/2021 11:04:38
|Thread: 4 jaw Independent for a 7x12|
Just been into Machine Mart for something other than machining, to help a friend.
Looking at their latest catalogue, my impression is that prices are higher than our usual model engineering suppliers, such as Arc Euro, Chester or Warco.
Given my previous experiences. they are unlikely to meet any model engineering needs, For others, Toolstation or Screrwfix may on shorter odds of getting the business.
Purely, my past experiences, but in this instance, their competitors did not have what was needed. , .
|Thread: Interfering with fits?|
To make life easierv on machine, tool ,a nd you.
Make a sacrificial plug to go into the bore, and then drill a hole, centred on the boundary between sacrificial plug and bore.. This will remove a lot of the material that needs not to be there.
Remove plug and cut keyway.
You can either hold the tool in the tailstiock in some way, or in the toolpost, (Obviously equally disposed vertically about the centreline ) and then rack the tool to and fro, using the Saddle or tailstock handwheel..
The toolpost method is better since the Cross Slide can be used to control the depth of cut.
Once, I did cut a square hole, using a tool in the tailstock, but bit was laborious, since I had virtually no control over depth of cut. The method was to cut as deep as possible, about 0.010", withdraw, rotate chuck by 90 degrees, and repeat. Continue repeating until hole was to completed depth. Crude, and slow, but it produced the desired result. Not that I would want to make a habit of it!
With 20/20 hindsight, should have mounted the tool in the Toolpost!being bone idle, the tool was ground on the front face only, so that the swarf had to be cleared on each backstroke. Should have been ground like a small parting tool, with clearance on both sides.
|Thread: Strange stain in caravan|
If gentle methods fail, try bleach (Sodium Hypochlorite ) removes tannin stains from tea pot and mugs very well!
You only need a few drops to roll around and the stain disappears almost before your eyes.
|Thread: Reaming a hole|
One thought about reaming in the lathe, is that is anything is slightly off centre, the resulting hole will be oversize, because of the reamer acting like a boring bar, and predominantly cutting on one side.
My method is always to use a floating reamer holder. Thus the reamer can follow the hole that has already been drilled / bored which should be concentric.
If the hole is blind, machine reamer, having a shorter lead than a hand reamer will produce a greater length of hole to size than a hand reamer. Less of a problem with through holes.
|Thread: Clinging to the Past|
Someone said that those who ignore history are condemned to repeat the mistakes.
Because basic arithmetic seems to have been omitted from the syllabus, folk now have difficulty working out pulley sizes to give a required speed, from a motor of known speed. Similarly calculating the gear ratio between Mandrel and a Leadscrew of known pitch. Cutting a screw thread of the required pitch seems to be difficult, (Except, perhaps for the geriatrics among us, who had such things drummed into our heads at an early age )..
Remember "Times Tables"? Meccano taught me multiples of 19, as well as calculating simple and compound pulley and sprocket ratios.
So fractions are still necessary to find the gears to reduce a speed to says 5/6 of its value, A 35T gear driving a 42T (if one is available ) is one possibility, or a 75T driving a 90T?. Reversed, any of those should allow a 2.5 mm pitch to be produced on a lathe with a 3 mm pitch Leadscrew.. Compounded with a 3:1 reduction the original reduction would allow a 8 tpi Leadscrew to produce a 20 tpi thread.
Just fractions really.
Ask Brian Wood!
An understanding of the basics makes the complicated more understandable.
Understanding the principles makes anything more comprehensible.
Despite spending lots of time with fuel injection equipment, to me, microns are less easy to visualise than thous.
An average human hair is more easily visualised as being 0.005" than 127 microns.
Again, using whatever system / measurement is most easily applicable. Who wants to measure their car's fuel consumption in dimensions of 1.6 Km per 277 cubic inches?
Again, horses for courses
|Thread: Is there such a thing as an 'external reamer'?|
If the object is to produce the spigot, what is the matter with turning the OD of the spigot and finally facing to length?
|Thread: Converting fractions to decimals|
This looks be getting a little bitter and twisted, when we are taking of UNITS.
The same parameter can be dimensioned in whatever unit you like, Angstrom units, Light years, yards; rods, poles or perches; spans, or bricks, if that is what takes your fancy. Just depends on how many decimal points you are prepared to tolerate, even if you prefer duodecimal, or whatever..
Film speeds were measured in Hurter and Driffield, Scheiner, Weston, Gost, and ASA, all for the same material,
Before anyone says it, not all at the same time!
They are only units, you choose the one that suits best. Best to try to use the same units as other people, which is where Whitworth, Sayers, BSI and ANSI, etc came in.
Because my kit is all Imperial, I am an "Ancient Oddity" in all senses, but occasionally use Metric,WHEN IT SUITS.
My shop made Workshop Comparator incorporates 8-32 UNC, 5/16 BSW and half round 4 mm pitch 0.0625"deep threads, because
a ) the UNC and BSF fixings were available, and
b ) I wanted a coarse thread, and the lathe could be set to 4 mm pitch, into which I could match a 1/8" ball bearing..
They happened to be the horses that suited my courses, did the job, and do not need to be interchangeable with anything else....
|Thread: small toothed belts|
Suppliers of "pulleys" for cogged belts, such Davall Gears, Reliance Gears, HPC Gears etc?
|Thread: Looking for solution to incorrigibly jumpy needle roller bearings|
If you can find ball races that will fit the shaft and the housing, you could always replace a long , unreliable needle bearing by two, or more, ball races with suitable spacers. To take the loads, it would be worth fitting as many ball races as possible, to carry the loads.
The end product might be more durable than the original equipment!
|Thread: 4 jaw Independent for a 7x12|
Of the nbregister on the CL300 does differ from the other Sieg mini lathes, (Chester etc ) since you have a lathe with a 3 jaw chuck, you have machinery to turn a suitable register on a backplate to match the flange.
Once fitted to the flange,the OD can be turned to be the register for the new 4 jaw chuck.
Then it needs to be drilled, possibly tapped, for the fixings for the chuck.
If the chuck body is tapped, you will need to make some pointed studs to screw into the chuck, with which to mark the backplate for the holes.
Since the holes will be clearance, location being by the register of the backplate to the flange, and OD to the chuck, the holes can be a little oversize to take care of any small inaccuracies..
|Thread: Hello from Winnipeg, Canada|
I think that the Me 109 was faster than the Hurricane, and being fuel injected the engine did not cut out during violent manoeuvers. The Merlin was prone to this, in Hurricane and Spitfire, until "Miss Schilling's orifice" was fitted to the carburettors.
The Hurricane and Spitfire's advantage was that tey were more agile, and could turn more tightly than the Me, making it vulnerable.
|Thread: hi new here from ely|
P S M E held their first meeting, last night, for goodness knows how many months About 11 attended.
If you can't find anything closer, the next meeting is Monday September 6th (See the website for the location in Eye so a little closer your way on the A47 than coming into Peterborough.
|Thread: Hello from Winnipeg, Canada|
The Hurricane could take a lot more punishment, and was easier to repair than the Spitfire. As long as the missile missed the framework, it passed through the fabric with minimum effect.
The Spitfire was a stressed monocoque so a hole was more serious, and heavy damage less easily repaired, but was faster because it was sleeker.
It easier to believe that the Spitfire won the Battle of Britain, but there were a lot more Hurricanes involved, so they bore the brunt of the battle.
Both aircraft and their pilots did a splendid job for our country and the world in general.
The Defiant seemed a good idea at the time, but the heavy turret made it slower and less manouverable, so was soon withdrawn.
|Thread: Hello from Leeds|
Welcome, and good advice already forthcoming.
Lots of the questions in your mind have been asked, and answered many times before, so look back through previous threads.
You can shorten the search time by narrowing the field of search. So search for one subject at a time.
|Thread: Interfering with fits?|
Not Aluminium into steel, but when I wanted to shrink fit a steel shaftv into a cast iron base, I chose 0.001" (0.0254 mm ) interference.
cast Iron base was reamed to 1", and measured.
Steel shaft was turned own to measured diameter+0.001"
The shaft spent the night in the freezer, and the 6" diameter x 1.25" thick cast iron was cleaned and with permission heated in the oven at gas mark 6.
The shaft was removed from the freezer and wrapped in a towel, while thge base was moved from the oven onto a piece of 10 mm ply on the kitchen floor.
Shaft unwrapped and was a nice fit into the base. The frost on the shaft gradually disappered upwards.
When cool; a tight fit.
Based on industrial experience, Loctite usually needs a clearance of 0..002 - 0.003", You are relying on the shear strength of the anaerobic. So choose the correct grade, such as a retaining compound, not one intended to provide a relatively easy disassembly in the future.
Edited By Howard Lewis on 17/08/2021 16:45:45
|Thread: choices of material to turn|
If you are newbie to machining, make your mistakes on free cutting steel, such as leaded.
Stainless, can come later, when you have more experience.
Scrapping some 12 mm free cutting steel, if you get something wrong, will be cheaper than stainless, and less likely..
You learn to walk, before trying to sprint. Channel swimming comes after you have learned swim.
You are at the bottom of a learning curve.
Very few of us ever reach the peak! It's a LONG way off for me!
Get some books and read up on using a lathe, it will save you frustration and puzzlement.
You can gain experience by making simple accessories for the lathe, which will be useful after you have made them.
When you are familiar with the machine and using it, then you can try different materials. Then you will start to learn about feeds and speeds, depth of cut and tool shapes for best effect..
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.