Member postings for Clive Foster

Robert

My Drives Direct box provides me with a neutral line and, with the smoothing inductors, works exactly like proper three phase supply save for the limitation on motor power that can be started. Drives Direct says 5 hp, half the VFD rated load, I reckon 3 hp is more realistic if the motor is connected to any sort of load.

So far as I can see or measure it behaves sufficiently like real three phase for anything I wish to hang on it to be perfectly happy.

Appears to be a little less demanding on the single phase supply than my friends Transwave rotary converter of similar rating.

I can only presume the doubling of price from Drives Direct relative to the standard Teco VFD covers the needed modifications to make everything safe, effective and not send interference back down the lines. I've no intention of opening it up and winding the clock back 40 odd years to when I was supposed to be some sort of electronics engineer to check. Over a decade of successful operation proves that something must be right as all the magic smoke is still successfully contained.

That said I'd not even dream of installing something like that without output smoothing. The radiated interference from driving a naked line doesn't bear thinking about.

I'd prefer a proper mains three phase but given that it seems to be impossible to find someone willing to connect up the three phase income I have the "interim" device has to soldier on. Newt so permanent as a temporary fix.

Clive

I have 10 machines (I think, haven't counted recently) on a 10 hp Drives Direct boxes, which are modified Teco units, with the smoothing inductor add on on the back to clean up the output. Still going strong after over 10 years. Biggest motor is 3 hp and one is a two speed.

Normally one machine at a time but it comes just fine if the compressor, Hydrovane 502 with 3 hp motor, kicks in mid job.

Doing the maths at todays prices individual brand name VFD boxes would be cheaper if all the machines were modern enough to have dual voltage motors.

If I were to start over today I'd probably use individual brand name VFD boxes from Inverter Drive Supermarket and come out more or less even. Replace the two speed motor with a new 6 pole one and swop the Hydrovane 502 for the tripod mount 504 I just happen to have lying around (!) which will give me enough air running at the 850 or so rpm it could manage on 220 volts. Hydrovanes have 440 volt delta connect motors so no low voltage connections.

I'd be very chary of using an economy range VFD as a direct substitute for a proper mains three phase power switching motors on and off with the box running. Very very hard on the capacitors even when de-rated. There are alternative input rectifier configurations that ought to reduce the capacitor shock loading relative to a standard set-up. I presume the high cost of the Drives Direct boxes is due to installing such plus re-programming the box so it doesn't fall out on seeing only one phase on the input and/or high current demand on the output side when a motor starts.

Clive

Just to close this thread for any folk looking for advice in future I eventually went with Digital-Zones.com.

Just under £30 for the full Home and Business version of Office 2021.

As promised download link arrived less than an hour after paying. Straight to Microsoft official site to retrieve the installer & software package.

Hardest bit was sorting out the activation process. Procedure isn't that clear if you don't instinctively do it the right way.

Doesn't help that it all looks to be setting up the Microsoft 365 online version until they very last page where a magic "Click here if you have bought Office" button appears.Whereupon all is ready to go.

Hate this modern one screen per task approach apparently optimised for old style small scree smartphones. If it were all on one page it would be obvious what was going on.

The one screen per task approach always seems to be an open invitation to error, or near fraud in the case of less honest vendors, as lacking a visible map you have to trust that the succession of clicks isn't leading you astray like a GPS fixated on farm tracks.

Old school notepad and pen to write down the steps is probably a good idea.

Clive

Bo'sun

Pretty sure that the 1/2 key isn't working.

Clive

Bo'sun

If you zero at the first edge, find the second edge the display should read the distance between the edges (plus the centre finder probe diameter).

If you them press the 1/2 function key the display reading should halve.

Winding back to zero should place the quill above the centre position.

Questions :-

1) Does the display reading halve when you press them 1/2 key?

2) Does the display count down to zero when you move back towards the middle or freeze on the 1/2 value?

If the reading doesn't halve when you press the 1/2 key odds are the key isn't working properly. Contact issue under the membrane.

If If the reading freezes and doesn't count down you may have entered a lock mode.

My Sino set up has a lock mode if I read the book correctly. Something I make sure to stay the hell away from as the potential for confusion is obvious. That said I can see various uses for it if you exploit the other memories. Transfer of dimensions to replicate feature in other places for example.

Clive

Jason

Mis read my post I think. Mine are OK for facing but thats about all.

Being pin lock on a 20-20 shank for the CCMT 12-04 size inserts I have its all bit cumbersome.

Your smaller inserts and screw lock shanks are vastly more handleable. Doing something like your second picture with my bigger inserts and shank is barely worth the hassle.

Even working 12" to the ft scale.

Which is why I've never bothered to get a right hand holder.

Size really does matter and for the normal model engineer I can see no reason for setting up to use -12- size inserts. Go smaller.

Locking into -12- size over a decade ago because the price was right may have been a mistake on my part although there are no issues with plain turning and the insert in normal configuration.

Clive

Basic codes for pin style holders to use the obtuse corners of a CCMT are PCBNL and PCBNR.

More use in theory than practice as the layout makes for a cumbersome tool. I have a PCBNL 2020 which should be good for facing jobs but it's pretty much impossible to get into position for anything else. A PCBNR could, in principle, be used for reducing the diameter of fairly long length of stock but you have to make prior arrangements for the overhang of the tool in front of the cutting point unless its a single, pretty shallow, cut.

In practice you do rather less pure facing than longitudinal turning so an insert in an obtuse holder will last a very long time.

The ordinary CCMT holders are quite capable of handling facing duties anyway. They can cut up to a shoulder too inherently leaving a nice radius for stress relief. So switching tools just for a facing cut tends to be too much trouble. I have about 5 CCMT inserts saved to use up the other corner. I won't live long enough to use them.

Clive

Edited By Clive Foster on 29/09/2023 12:27:52

Further to what Peo says single skin walls or ordinary brick and not waterproof in the UK.

Ever.

Whatever nostrum is applied to the inside.

There is a reason why relatively modern UK construction has been based around cavity walls. The thermodynamic and humidity variation effects of a cavity are far more complex than many "experts" would wish you to believe but they allow you to use a relatively porous "common stock" brick for most of an exterior wall.

You pretty much have to put some sort of gap in between brick wall and the inside face to be sure all will stay dry. Impervious insulation fill is generally OK. Fibreglass probably theoretically little better but any difference is unlikely to matter unless the wall in question faces high winds and driving rain.

I found OSB sheets with several coats of white emulsion to be an aesthetically satisfactory internal wall and easy to do.

Often forgotten that the UK has one off the most brutal climates when it comes to building survival due to the repetitive cycling of atmospheric and building surface temperatures through the dew point of a generally damp atmosphere. Not forgetting getting pretty hot on a fairly regular basis. Most other regions get either hot or cold and stay there for months on end.

Clive

I have the interlocking tiles on the garage floor and simple waterproof chipboard tongue and groove jointed underflooring sheets in the workshop. Both on concrete.

Both are effective and both vastly better than bare concrete. Tongue and groove probably a bit cheaper but, despite being nominally waterproof, best not to use where things could get damp. Like a garage if you keep the standard door. Interlocking tiles prettier.

If you stay with a standard type door pay attention to sealing round the sides and bottom. The interlocking tiles have edging ramps which can help fill gaps. Alternatively the triangular glue down rubber strips about 1 inch high by 4 inches wide are very good. Cut it half in you don't want a dip on the backside before getting to the flooring. Cable cover strips are effectively same thing but much easier to cut due to cable hole rather than solid rubber down the middle.

Clive

In a similar situation I found the rotary wire brushes made for Dremel's, Multi-Tools et al were narrow enough to get down into the grooves. Life time was distressingly short and care was needed to start teh whole brush into teh groove without poking strands outside. I found putting the brush in stationary and winding up from minimum speed worked best but my slots were pretty much exactly brush width.

Results were good.

Clive

Ady1

I'm not convinced that such cracking is necessarily end of life for an iron casting on a hefty piece of equipment.

Way I see it is that theoretically a casting is a nice essentially homogeneous lump of iron which has cooled evenly so all the little grains are stuck nicely together and just sit there without mutual stress.

If anyone thinks that ever happens in practice I have a wonderful deal on a bridge. Used notes only.

In reality there is a tensile stress across every grain boundary, a necessary condition of the formation of the surfaces that define a grain, which could expand to a crack given sufficient force in the right place. In the body of a decently solid casting everything is decently well balanced. No sufficiently large forces to start a crack and drive it past grain boundaries can exist. So all is fine. Important to remember that although the stresses across a grain boundary could be crack starters the boundaries are also crack stoppers. I'm told the maths and science is really, really complicated.

Cut a hole in the casting (or drastically change its section) and a new boundary is created taking things out of balance. As material is removed the balance is most likely changed to increase the tensile stress at grain boundaries around the hole. In a good, well designed casting all is fine.

However if a crack does start inside and run across into a hole or surface it's proof that somewhere there is enough tensile force to break the casting along the line of the crack. The crack opening up has relieved some of the stress further back. So, in some ways, the casting may overall be stronger as the points at which opening crack has received the stress can take more load before breaking.

Its no different to the bottom rivets in Kiplings "Ship That Found Herself" giving a little so the garboard strake gained a fraction of an inch of play letting the ship go along much more easily.

Significant difference between giving a little and failing completely of course.

An effective way visualise whats going on with such cracks is to consider a seesaw held level by ratchet straps at each end. Tightening the straps just bends the seesaw a bit but things stay stable. But clearly it will now take less load to break the seesaw. The tighter the straps the effectively weaker the seesaw becomes as more and more of its strength is absorbed in resisting the straps.

By analogy this is the same as a piece of casting strained between two potential cracks.

If one strap is sufficiently weaker than the other to fail before the seesaw breaks it will snap. That end of the seesaw goes up. The other goes down to the ground. The bending stress in the blade disappears, so its full strength is available to resist loads. Stick a scaffold pole or Acrow prop under the upward end and everything is stable with the down and fully supported by the ground. Overall it's actually stronger than before. But a, hopefully slightly, different shape.

Conversely put a new stronger strap on and winch things up good'n tight. Then add a bit more for good measure. Odds are the other strap will break and you are back where you started except t'other way about.

Going back to our casting the crack opening up to the hole has relieved some internal stresses. So if you repair it by a cold lock or puddling process putting minimal closing stress on the crack balance will be restored and overall things may well be a little stronger.

A hot process putting significant quantities of molten metal into the hole that contracts when it cools is effectively the same as the stronger strap in the seesaw analogy. Fixing the crack has put more stress on the nascent one at the other end due to contraction of the filler. Maybe enough to turn that into a real crack.

Real castings are way more complex than the seesaw but, as Kurtis found, adding significant contraction forces when repairing cracks upsets the balance elsewhere in the casting forming lots of new cracks.

If you heat the casting before hot repair contraction stresses due to cooling can be much less so the repair is satisfactory. But there is always some extra stress involved. Knowing what to do to minimise this added stress is an art form.

Clive

Kiwi Bloke

Regrettably I know little more about the pudding process beyond discovering that it worked well after being told that was the way to repair the banjo casting on my SouthBend Ten after discovering a previous owner had over-tensioned the bolt snapping one side of the loop off the arm. I used the DIY market arc welding rods I had and made the repair around a mandrel of the same diameter as the SouthBend mount. The result was, so far as I could see, as round as the original. The banjo moved freely without rock and clamped up properly with moderate bolt torque. Which confirmed that very little, if any, contraction occurred a the repair joint. Any contraction would have opened things out and pulled the hole out of round.

Subsequent efforts have proven to my satisfaction that it's a suitable process in the right circumstances. Takes forever though.

Raising the subject with folk who do know cast iron welding, whether in person or on line gets basically this response.

Expert "Naughty boy. You really shouldn't do this. Totally wrong way to go about things. It has never been an approved technique although folk used to do it back in the dark ages."

Me "But it works just fine if you are careful."

Expert "Of course it does. Can be more than decently strong too."

Me. "??????"

Expert "But you must never, ever do it. Its wrong."

Me "OKay."

Thinks naughty words and chalks it up to yet another time when ignoring the expert is the way to go. One thing I learned in 40 odd years as a Scientist / R&D engineer is that experts are very handy people to have around but there are limits.

Clive

From what I've seen of industrial machines common practice with Dickson QCTP is to use a plain nut, a thick washer and a thick wall spacer loosely spigoted into the toolpost bore. The spacer being needed to lift the nut above the tool clamp screws.

I do know of folk whose opinion I have reason to respect advocating a second, standard thickness, washer under the nut in addition to the aforementioned thick one. I have never seen a flange nut used. My instructors said that the sole use for flange nuts in a machine shop was with mill table clamping kits.

I imagine the reasoning behind the use of a thick washer on top of the spacer was to spread any twisting loads as the nut was pulled down tight so the post itself doesn't try to turn. Observation of the Dickson set-up on my big Pratt & Whitney lathe seems to support this idea as both washer and spacer turn slightly with the nut on final tightening but lag. So the top washer turns less than the nut and the spacer less than the washer whilst the post says still. The turn angles are small, little more than barely enough to see and probably wouldn't be visible on smaller machine where the tightening torque is proportionally less.

I don't use a locating pin or underneath ratchet on my tool posts but I do require that the post sides stay in alignment with lathe cross slide and bed.

Whether the distribution of frictional forces to reduce the chance of a toolpost turning actually matters in practice I know not. I don't recall any such post twisting effects when using a simple standard washer under the nut of the tool post stud on my SouthBend lathes. Simple hand holding worked just fine.

Clive

The fundamental issue with any milling machine is that it be rigid enough and powerful enough to drive a cutter at a speed and depth of cut sufficient t to ensure that it cuts, rather than rubs, the material in question. Rubbing destroys a cutter in short order so a cutter does need to go deep enough to get bite on the material.

Teensy, weeny shaving cuts are a bad idea because the cutter is so nearly tangential to the surface that it's harder for it to bite rather than bounce.

End mill book data for manual machines is generally based on 1/4 diameter step over (cuts) for a reason.

CNC folk running HSM (High Speed Machining) paths with small stopovers and uber fast spindles live in a different galaxy!

Even a Taig mill will cut steel, quite obdurate steel at that, quite happily given the right set-up and cutters (small ones). No one in their right mind would claim the two box sections bolted together frame is a poster child for rigidity. CNC versions with their inherently much steadier feed speeds do much better. As ever with baby machines its hard to maintain the slow, steady feed rates needed by hand so the steadier drive from a power feed or CNC works better.

Has to be said that most neophytes tend to want to over-speed. Ancient penguins like me aren't immune from that temptation either. Being spoilt by power feeds on everything except the Bridgeport Y axis (must get around to digging out the bits I've had for ages and fitting it) doesn't help.

Clive

Pete

Belt change on the varispeed Bridgeport and clone heads is basically motor off, top cover off, change belt and re-assemble. Not that difficult if you have the book to follow and the head at a convenient height to work on.

Which is where the R8, or collet grippable size, post on the table and a support frame for the motor end make life so much easier. Even with the table right down I found the Bridgeport motor was high enough that standing on a hop-up, or equivalent portable step, made the lift'n tilt a bit movements needed to remove it much easier. When it comes to hefty stuff I'm a great fan of working at "cuddleble" heights if you see what I mean.

On a Bridgeport you need to know the method for compressing the spring on the motor end of the varispeed so the pulleys can be separated leaving room to shift the motor. The right way is easy and safe. The unorthodox alternatives not so much. On the Bridgeport it's important to verify that the screws holding the key in place are properly tight. They can work loose and fall out leading to seriously expensive sounding noises.

Clive

Postscript about strength of puddled repairs as described in previous post.

There is no reliable way to know how strong a puddled repair is. What you are effectively trying to do is wedging the casting back together where it has cracked. Hopefully receiving some of the stresses behind that helped open the crack.

If you have pure compressive stresses its at least as safe as the original casting.

Any tensile or bending loads and you are in the lap of the gods. It will be stronger than the cracked casting but no way of knowing how much by as the bond made on the first puddling layer must be weaker than a deeper adhesion from a brazed or more sophisticated weld. Never as strong as a good casting would have been. But most successful "ordinary" castings are low stressed anyway. Crankshafts et al are a whole different world.

Clive

Kurtis is generally impressive but he really should have known better than to attack a casting showing that sort of crack issues with a hot welding process putting great gobs of metal into large gouges. A splendid illustration of why "metal-loc" and the various other cold, stitching, repair processes were invented.

Basic cause is that the casting was riddled with grain boundary dislocations and similar nascent cracks formed during manufacture or post manufacture heat treatment. The part has high tensile stresses across the line where the cracks have formed. Given the low tensile strength of cast iron the part is already close to failure so anything whether temperature cycling or mechanical loads will cause the material along the nascent cracks to separate reliving stresses elsewhere.

My guess is that someone cocked up a post casting heat treatment on a casting that wasn't as well bonded together internally as you'd ideally like leaving multitude of tensile stresses just waiting to turn into cracks. Heat it to nearly red and allow it to cool naturally and the inherent stresses of uneven cooling, due to wall thickness variation if nothing else, will cause more cracks to appear. Throw in significant thicknesses of even hotter, melted metal which will contract more than the coast iron as it cools and it's an open invitation for cracks to appear all over the place. Trying to figure out where the tensile forces induced by differential cooling will cause a not quite enough stress to crack to turn into an actual crack is probably impossible.

Ideally the repair needs to apply an expansive force to the cracks being fixed further relieving stresses in the main body whose combined efforts had generated the crack inn the first place. Pretty much wedging it back together.

The hot metal processes are largely fine when you are sticking a broken off bit back on given requisite care to keep the extra cooling stress somewhere safe. But dealing with main body cracks is an art form, assuming it can be done at all.

This is probably the one place where the 'field expedient" puddling technique using an arc welder with ductile rods is actually the one most likely to produce a good repair.

Start by gouging out the first crack you are going to fix for access, I'd not take out as much material as Kurtis did and I'd try to keep a sharpish bottom V rather than the near half round he used. Then using the thinnest rod you can with just enough current to bond put a thin layer of weld on one side of your gouge. Tap it with your chipping hammer as it cools peening the hot weld to largely relieve tensile stresses formed during cooling. Do the other side. Rinse and repeat a couple of times stopping if the casting shows any signs of getting significantly warm. When it does go find something else to do for an hour whilst it cools right down. When you start joining the bottom of the Vee make special effort with the peening. When the gouge is about half full you can move up to a slightly bigger rod and accept the repair area staying little warmer so things go faster but you still have to keep peening trying to drive the weld metal into compression.

If you managed a perfect job (Ha! optimist) all the cooling tensile stresses are confined to weld metal, hence the need for a ductile rod, so the main casting sits as was cold retaining the internal stress release resulting from the original crack opening up.

Rinse and repeat for the next crack. Takes forever. On a job like that fixing two cracks a day would be good going. That said most of the time you are doing other things whilst it cools down properly.

Objectively it's not a commercial technique but it does work. I've used it a time or six when needs must. Impurities are still a major bugbear. Did a bit of Victorian decorative cast iron metal work that appeared to be about 50% included carbon. I looked like coal miner by the time I'd finished and the amount of weld for simple break was stupid but got 'er done! Never, absolutely not ever, again! On the other hand a broken banjo off a SouthBend lathe went together so well that it might as well have been mild steel.

Clive

Edited By Clive Foster on 22/09/2023 20:38:13

KenL

Theoretically it might be possible to start a single phase motor by connecting one phase from a three phase inverter to the main winding and another to the start winding. This will give a 120° phase shift between start and run plus whatever "natural" phase shift is built into the motor winding arrangements.

Sounds to me that it would be way too much and you'd need to put a capacitor or inductor in series with the start winding to adjust things to something more reasonable.

Oversimplifying things. Some phase shift between start and run windings is needed to generate a rotating field in a stationary single phase motor so it will run. Too much shift will limit how fast the motor can go with the start winding energised so the main winding won't take over and accelerate the motor up to speed. Too little phase shift and starting torque will be impractically small.

Once running the thing ought to keep going on the main winding fed by one of the VFD phases.

In practice a party trick with things set-up just so to do a demo. I imagine the VFD is going to be seriously unhappy at start-up time with one output floating and wildly different loadings on the other two let alone dropping onto one phase once all is going.

This style of idea has been floating around almost as long as VFDs have been around. To the best of my knowledge no one has made a commercial product of this type but I'd be unsurprised to discover that special, dedicated, motor / VFD pairs haven't been made for some applications. It would appear to be contender for things like multi-speed washing machine drives.

Clive

Clive

+1 for what Ian P says.

Grip it between two fairly narrow rings with tapered insides. Probably aranging to work at something like 1/3 rd of the diameter off set from top and bottom would be fine.

All the successful ball based tilt holders I've used seemed to grip on narrow rings.

Clive

Mark

There is complexity and there is complexity!

If I recall correctly from the ones I've seen of that type only uses three each of two styles of arm with all the pivots machined integrally. So given a decent set uplifts probably relatively easy to machine and get all the pivots nice fitting and in the right place.

The other styles generally have rather more parts, albeit simpler, but tolerance requirements will still be similar.

I suspect that when you get down to it machining and assmbly time will be similar.

Clive