Member postings for Clive Foster

Agree with Tony that 60° is correct.

But alignment is much more important than angle. The dovetails on each component both have to be on the same plane so full surface engagement occurs when the piston pushes out. Anything more than the smallest error will cause things to try and tilt so much of the registration surfaces are in the wind doing nothing to keep the tool holder stable.

Although this co-planarity is relatively easy to achieve with simple equipment given careful execution of a well thought out technique I've never cared much for the piston concept because the stability dynamics are inherently a bit iffy. Everything rides on the mutual alignment of those dovetails which, to my mind, makes the system under constrained. But from a DIY perspective you literally have only one setting to get right.

Clive

No need to turn a polyVee belt inside out. The soft Vee side works just fine on flat belt pulleys.

I'd be unsurprised to discover that a polyVee used in that manner actually outperforms an old style leather belt working at (too) short centres on a small lathe. Worked well on my SouthBend Heavy 10. Much better than the leather belt it came with but that was old and neglected.

The back sides of both polyVee and timing belts are generally not that good as driving surfaces. By design in most cases as the back side just runs over a tensioning pulley so low friction reduces belt wear. Double drive surface belts where both sides drive things are somewhat different to the usual type.

Grinding wheel drives should only be just good enough to transmit the power needed for normal use and wheel dressing. That way if you do get a serious dig or jam up the wheel stalls before serious damage is done or, quell horror, it bursts.

Clive

Another vote for getting a kit.

Back when I fitted DRO systems to my machines such things weren't around. Getting the various parts properly lined up and fitted in decent places was something of a pain. Fortunately my design skills and improvised bracket creativity to hold things in place whilst marking out and drilling fixing holes were up to the job.

Not perfect but decently useable despite recognising there were things I'd do differently next time.

Which might or might not have worked out better overall.

I find a lot of the "It would be better if ...." refinements to a useable system end up an exercise in turning the benches round to satisfy the new foreman. Fixing the bit you are unhappy with just ends up shifting the unhappiness to another place. Seems to be a pretty universal rule for everything that 80% is happy, 20% not so much. Or thereabouts. The art being to make sure the things you normally do fall into the 80% happy region.

With a kit you can be pretty sure that all the normal things are in the 80% happy region and that the "Oh Sh*****.." gotcha that so often gets overlooked until nearly finished has been safely avoided.

When it comes to mounting onto irregular casting shapes I found the best way was to mock up the scale position using suitable angle with a layer of car body filler underneath it to make a true surface to bolt to. The universal bits n'bobs sets that came with the DRO set in question hand suitable length of angle. Wrapping it in cling film before pushing into the filler meant I could get it off again. In practice the mounting I had to use filer on went faster and easier than the ones where I just went ahead and wiggled the rackets et al into position.

Probably 'cos I thought it all through first and mocked up the reader position on the angle too. Much more room to make up transfer brackets and guides on the bench instead of working direct off the machine.

Clive

Edited By Clive Foster on 14/04/2023 08:44:15

Howard

You need a bit of oversize if the die is to easily go into the holder.

I have one that is less than 5 thou oversize relative to the die diameters and it's a total pain to get dies in and out. Usual method is to screw a stud or similar into it to use as a handle. Its important to get the die seated true against the back of the recess which is hard without a touch of wiggle room.

Clive

Duncan

Sounds like the advice I found ages back is about right.

Depending on which authority you choose to quote 950°C is up at the top end off the cherry red shading towards orange region.

Fair bit higher than copper needs in my experience. I find it generally anneals quite well when merely at the higher end of darkish red. Especially if quenched. If leaving to air cool it seems to like a bit more heat and you have to shift the oxide so air cool is too much faff for me.

Clive.

Mike

My understanding is that kunifer can be annealed in the same way as copper. Heat to bright cherry red then quench in cold water. It is said that kunifer is less tolerant than copper over not quite being up to temperature and, unlike copper, you can't get away with air cooling.

Have to say I've never done it myself. Merely looked the procedure up before starting a job just in case.

Clive

Thats a tricky measurement without dedicated metrology equipment.

It is said that typically taper gibs on machines made to imperial standards are tapered at 1/4" to the foot.

Even non typical ones will be a sensible fraction ion an inch per foot. Slope is much easier to set out accurately than angles.

Metric countries use 50:1, 5 mm in 250 mm. Close enough to be confusing if you try to do it by angles.

Allegedly you can measure direct on the machine using two bearing balls of different, suitable, sizes. Push the slide over so the flat sides are in contact and insert the small ball from the narrow gap end and larger one from the wider gap end.

Measure how far down they go, calculate the separation at the centre line running transversely across the gib gap and calculate the slope. The maths is simple trigonometry of similar triangles.

Obviously the greater the difference in ball sizes the easier it is to be accurate. Also easier retrieve the balls if they don't go in very far. Really helps that the result is known to be a sensible fraction of an inch per foot.

If you can mount things on a mill table, or similar accurate leadscrew controlled thing, so that both the straight and taper dovetails can be got at with a dial gauge its possible to measure the taper directly. Straight side acts as a reference so you don't have to worry about getting things uber accurately aligned with the travel.

Clive

Seems to be yet another one of those "Rules are made for the guidance of wise men and obedience of fools" thing.

When you know what you are doing, how to select the wood and how to treat it there seems to be a fairly wide variety of woods that can be used for tool boxes, chests and cabinets without corrosion issues.

For the less well informed picking a fairly random sample of xxxxx wood is risky. Hence sensible to stick to a restricted selection of woods that are both known to work well and regularly available in appropriately treated form.

Which is why I wondered what Starrett used for their solid wood instrument cases. These appear to hold the instruments in simple cavities routed out of solid wood with no varnish or other treatment. The outside is varnished.

Clive

Edited By Clive Foster on 05/04/2023 20:09:14

Does anyone know what wood Starrett used for their carved from solid micrometer, vernier et al cases.

Looks to me that the ones I have might be sapele.

Whatever it is simply carving out recesses in the solid material seems perfectly satisfactory from the corrosion point go view. I have some such cases and contents that I know to be over 40 years old. Not necessarily carefully stored indoors before I got them either.

Clive

I imagine there are some subtleties of construction that seriously affect the stiffness of benches made like the Sealey one in question.

Back in the early days of the DERA / DRA / Qinetiq / DSL morphing process management dictated the wholesale installation of new lab benches and cabinets based on bolt up frames of that style. Although vastly inferior to the old style solid teak benches (and storage units) those frames were adequately stiff and up to moderate metalworking, sawing et al duties with a medium sized vice fitted. Used free standing so not as stable as you'd ideally like but I'm pretty sure that bolting down to a solid floor would have fixed that.

Simple standard hex socket bolts did the holding together bit so the shoulder bolt refinements suggested by Robert wouldn't have been necessary although correctly engineered in they would undoubtably be effective. It's around 30 odd years since I helped assemble a set so I don't recall anything spectacularity clever in engineering terms. Frankly I was surprised how good they turned out. But still glad that I made sure my lab didn't get the modern kit!

First step is to take a good look at how the bolts up joints align and go together. It dosen't take very much fitting infelicity to make it all seriously wiggly. If the fits are good next step is to brace the open panels at side and rear. Whether simple diagonal struts or diaphragms. If you can live with the looks aluminium tread plate panels are seriously stiffer than plain alloy or steel of the same nominal thickness. I'd also put a horizontal strut at the front about 6" to 9" down which will make considerable difference, especially if a brace or diaphragm can be added.

Clive

Edited By Clive Foster on 04/04/2023 12:13:46

+1 for the suggestion from MichaelG that you go for a narrow Poly-Vee belt rather than toothed. If for no other reason than that the pulleys can easily be made yourself. Just get cunning with a bed stop and spacers to get the Vee spacing right.

Toothed belts can have issues when the centre spacing is short and the difference in pulley sizes large due to the limited wrap angle on the smaller pulley. At your low powers probably mostly noise but you may get premature wear due to the teeth not registering neatly when entering the small pulley. Eye-balling your set up I'd think it to be firmly in what I interpreted from the data as being in the iffy region when I considered a toothed belt set up. Went Poly-Vee using similar wrap angles, moving the motor to set tension, and never regretted it.

John Haine illustrates the textbook set up with a bit more space between the pulleys and a nice ball bearing tensioner to define the belt run.

Toothed belts are excellent devices but there are definitely dragons in the data sheets waiting to chomp the unwary.

Clive

+1 for fitting a VFD. The import VFD boxes are so cheap that it's a no-brainer decision. If it's a permanent star connection the 380 V breed will do fine. Basically one less problem. Buy, move, wire and go is attractive. Extra value might not quite cover the extra cost but will certainly lead to an easier sale. One less lever for "How about ......." ££ less than the asking price.

Fitting a DRO is generally a pain due to the accurate mechanical work involved in getting the scales lined up. I suspect that value wise a DRO is either zero sum at best where the extra value equals the cost of the DRO or loose a bit. I'm inclined to think that a high end DRO set up only adds the price of commodity E-Bay / box shifter set up.

Clive

If I recall correctly once the kit was a few years old the rubber lost a bit of resiliency and the bucks didn't go together that well. Breathing on the projections immediately before pushing together restored easy mating.

Much more realistic and generally nicer to handle than Lego, which always seemed very crude to me. My inherited kit had superb windows and roof parts along with a quite thick instruction book with lots of examples of houses you could make.

Passed on to mothers sisters grandchildren who wantonly destroyed and dispersed it, along with the monster Meccano box.

As Nigel says its almost scary to contemplate what would happen if modern kids tried to do the sort of things that were routinely published as thing for teh clever boy or girl to do in pre-war and post-war "I'm on holiday and bored" things to do books. My generation and I sometimes have a minor start before realising "Yes we could do that.".

Clive

Fluke publish a handy little guide to diagnosing voltage issues on VFD units :-

**LINK**

https://www.fluke.com/en-gb/learn/blog/motors-drives-pumps-compressors/how-to-measure-output-voltage-from-a-vfd-to-a-motor.

De-mistifies things quite nicely.

Often forgotten that the DC bus voltage is technically 1.41 times the RMS input voltage. So a 400 volt VFD for a star connected motor has approaching 700 volts inside and a 230 volt one for delta connection approaching 350 volts. So to properly go from normal single phase to 400 three phase the voltage has to be near enough trebled and capacitor storage great enough to supply the motor without too much voltage drop. A tall order. No wonder things have to be de-rated.

Clive

Jasons E-Bay fu and Google fu is better than mine.

Found a couple of similar but not the same offerings and several of the "shoe box" style more or less Darex clones but not one just like the Arc one.

Clive

Steve

That EMG machine looks to be by far the best option for quick and simple use. Totally enclosed so the H&S folk shouldn't be upset.

Unfortunately it looks as if it's no longer made. Internet searches don't turn up a current maker or UK importer.

Chester list a similar device called the Neptune :-

**LINK**

https://www.chestermachinetools.com/product/neptune-brierley-end-mill-grinder/

so might be worth giving them a call.

Cuttermasters are said to be easy to use too. Less setting up faff than a Clarkson or similar using the standard tool holding devices.

Clive

How does the cost of contacting a sharpening service compare with buying a machine and doing your own?

Unless there are institutional budgeting procedures involved that seriously skew things I can't see doing your own being financially viable.

If institutional constraints make DIY viable the obvious answer is to find a Clarkson, Boxford or similar proper small T&C grinder and learn how to use it. Great advantage of such machines is that you can gnash the ends of the cutters properly and get rather more sharpening out of them. Flute grinding, with the associated change in cut diameter, is probably too confusing in the educational environment.

Sounds like you may have the volume of cutters to make learning worthwhile. However do remember that "throw away" cutters were invented for a reason.

Allegedly the Deckel clone based sharpeners have accessories that allow them to do end mills but I have my doubts as to how practical the devices are. From what I've seen the devices sold to turn these engraving cutter grinders into poor mans T&C systems tend to be touchy in set up and over reliant on operator set-up skill to make a less than robust system work.

Darex make industrial standard "poke it in the hole" sharpeners for the ends of end mills but these don't seem to be available in the UK. Various clones are patchily available but most vendors seem to be seriously confused as to whether they are selling the drill sharpener or the end-mill sharpener.

If you just need to do the ends the Howard Hall system is attractive for very little money if the students build it. Refinements are obvious to make set-up and use easier at the expense of a moderate increase in build complexity. Howard unashamedly designs for simplest build.

If you have a surface grinder the tilting devices work well within their limitations.

Clive

Edited By Clive Foster on 25/03/2023 20:25:51

When you get to tenths thou and similar level errors process becomes almost more important than dead-nuts equipment accuracy. So long as your vice or other tooling is decently good the closeness to "perfection" of the job or set-up depends on how you approach things and how well you do the job.

I tend to the view that most of then time your true grip reference is the fixed vice jaw. So long a that is true and vertical a decent set up can be achieved even if the vice base isn't dead flat relative to the mill table or exactly perpendicular to the vice jaw. So long as the component is sturdy enough to grip without distortion something can usually be worked out by appropriate selection and positioning of parallels along with use of resilient packing or a roller for line contact on the moving jaw.

Generally I favour resilient packing, eg soft aluminium, as being easier to handle than a roller.

One day I shall experiment with magnets and a D shape packing piece set flat side to the job to combine the flexibility of a roller with a larger contact area on the workpiece..

My normal use vices have a very slight perpendicularity error between the fixed jaw and the base. Just enough that if 1/4" wide parallels are placed next to the fixed and moving jaws with a robust test piece having truly parallel sides around 2" or more wide gripped between the jaws and beaten down the parallel next to the moving jaw is just loose enough to slide out with moderate pressure. Depending on the job I either rely on the parallel next to the fixed jaw to set position, but still fit one close to the moving jaw to ensure things don't tilt objectionably when beating down, or put two parallel at the 1/3d jaw separation points. Seems to work adequately as parts look too be standing up straight.

Clive

Sorry double post. Why?

Clive

Edited By Clive Foster on 25/03/2023 09:46:10

Provided you have a sharp tool and sensibly light infeed dig in isn't problem with power feed.

The 'bang, everything stops" experience with power feed is invariably due to chip jamming in the tool slot. Which is why lubrication is desirable and the narrowed chip produced by insert tools so beneficial. As Andrew says a properly set up and properly fed insert tool leaves an excellent finish showing that the chip doesn't significantly touch the sides of the slot. Any contact being so light that the surface is not marked.

In practice we generally have to grind a conventional HSS blade with a flat top. Geo.H Thomas put a Vee top and front on his (how?) but thats for advanced folk only.

Grinding the front at an angle effectively produces a tilted chip that is less likely to jam up as it's already trying to rotate away from the walls of the slot. The top of the tool also needs to be angled for best results as that re-enforces the twisting action. Get the two angles opposed and it will jam! Need to get the speeds and feeds right so a long chip comes out. Unfortunately angling the tip produces a side force on the tool so it rubs disturbing the finish. All too often hobsons choice. Pip on the end of the job or rub marks.

Tight spiral chips on top of the tool indicate incorrect speed and feed combination. High risk of jamming up.

As ever careful set-up and careful work practice will get round these issues but its important to be aware of what can go wrong.

Small lathes have slender feed screws.

Effectively the push force goes through a column the core diameter of the screw. Not very big.

The helix of the thread produces a side force so the unsupported length of screw between the handle bearing and nut has a bowing force imposed. Clearance between nut and thread doesn't help as this provides extra space for any bow.

If the tool stops cutting momentarily the feed forces causes the unsupported part of the screw to bow acting like a stiff spring. Further feed with the tool not cutting increases the bow until the spring force is sufficient to re-start cutting an action whereupon the tool jumps forward. It takes more force to start a cut than it does to keep it going so the restarted cut is even greater than pure geometry predicts. In the worst case the job climbs over the tool or breaks it during the climb process.

Naturally the deeper the parting off slot the longer the unsupported part of the feed screw so the greater the bow tendency. Deeper slot means more chip drag too and thinner part of job remaining makes the whole thing less stable so, if a hand feed job is going to go wrong it always seems to be about 2/3 rds through. Just when you start to relax thinking "Yup, it's going right this time!"

Hence Daves "4 thou cut going to 25 thou and bang" scenario. Most likely with materials that work harden or form built up edges.

Given maliciously careful hand feed its possible to demonstrate this spring action on a slightly loose machine with the slide visibly oscillating as the cut stops and starts. First happened to me with an alloy forming a built up edge leading to regular momentary stops in cutting after the built up edge formed before it broke away as the tool rubbed allowing cutting to resume. Spectacular marks on the cut faces.

Using a rear tool post with a conventional feed screw keeps the screw in tension so there is no bow effect. SouthBend Heavy 10 lathes fitted with a taper turning attachment have the cross feed screw effectively reversed so it pulls from the back operating in tension. Parting off with a taper turning equipped Heavy 10 is noticeably better behaved and generally less fraught than with the non taper turning version with its conventional push feed screw.

Clive

Edited By Clive Foster on 25/03/2023 09:55:16