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Member postings for Clive Foster

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

Thread: Hammerite Smooth Paint
21/01/2017 22:21:14


Just checked wikipedia. You are right Carbon Tetrachloride is an effective fire extinguisher so its not of itself flammable. Big danger with fire is, as Clive Hartland says, production of phosgene gas when in contact with hot surfaces. Which is possibly even worse than simple burning. At lease you can usually see the flames.

Looking at the wiki entry its clearly very nasty stuff if abused but actually pretty safe if handled correctly. The quantity used in dry cleaning applications over the years must be enormous and dry cleaners aren't exactly into chemi-lab precautions.

Interesting to see the knee jerk "greenhouse gas" comment on wikipedia despite carbon tetrachloride having no significant absorption bands. Annoys me 'cos at one time I was an IR detection specialist.


Thread: Newall Readout
21/01/2017 20:22:35

Which version and how old? The eeprom in the old Digipac series eventually looses its content. Not all at once but slowly which will cause such effects. Not totally surprising as they must be around 40 years old. Far as I know fixing is now impossible as chips can't be got and Newall never divulged the contents. I eventually managed to get one done about ten years back but it was a struggle then. Later ones Topaz et al are said to suffer membrane keypad problems, some folks say they are not good for more than 10 to 20 years use.

Always worth scrubbing connectors and checking wiring loom.

Heads and bars seem to last nearly forever so you are probably in for a new console. Either Newall, or there is amore affordable alternative from one of other suppliers who do a conversion box to drive the spherosyn and put out common quadrature pulses.


Thread: Hammerite Smooth Paint
21/01/2017 20:11:44

its unlikely to be the original formulation as the thinner was basically carbon tetrachloride. Absolute conniption fit stuff for the elfins, EU crats et al. With some justification as its a considerable fire hazard and will de-fat skin tissues if abused. Version used as Finnigans thinners was modified, something like Genclene I think, so as to be adequately safe if not abused. Don't wash in it, don't breathe it basically. Recall discussing this way back with a safety rule enforcer 'crat type who went ballistic about Hammerite thinners being on sale to the general public.


Thread: Kennedy Vernier calipers
21/01/2017 15:30:50

If I recall correctly from brief handling of another guys equipment the Kennedy digital calipers were a pretty generic middle of the road device. Neither remarkably good or remarkably bad, just functional. Which I think pretty much summarises the usual Kennedy market position. But who remembers model numbers anyway so may not be that specific one although the one on E-Bay for £60 odd looks right. Doesn't appear to be a current model. Battery life may well be an issue on older types. Mitutoyo used to be much better than most at, usually, over 3 years but the other proper brands seem to be catching up.

Lawson HIS have a limited stock of the Mitutoyos linked to by Jon at just under £70.00, tenner cheaper subject to postage. (Currently in mimble mode over those. Do I need digital as I have both dial and verniers in both flavours and several sizes.)


Thread: Stuck drill chuck
19/01/2017 13:07:02


Good suggestion but probably not in this case as mine have a full cone centre in front of the flats, not a partial one as in a half centre. That said I have seen similar with what might be called a 3/4 centre where the narrow side of the centre was midway in size between a half and full centre and the wide side ran right out to the full diameter. Extended centre style so the centre proper was on a cylindrical projection. Piece of grinding machine kit I think. Possibly a conversion from a standard extended centre for a special job.


19/01/2017 11:04:12

Posted by John Haine on 19/01/2017 09:50:13:

A centre that doesn't have a tang usually has a threaded hole for a drawbar.

Not always. My rotating centre has a plain bore about 3/8" diameter and 1/2" long in the plain end. I simply loctited a suitable piece of rod in to act as an ejector.

My plain centres have spanner flats on the outer ends of the taper before the centre proper. Presumably these could be used in conjunction with a suitable spanner and spacer as an extraction device on machines with non self ejecting tailstocks. Or you could make up a simple U shaped tool with a lip to drop in the flats. Potentially handy for some of us but what are the flats really intended for?


Thread: The non-cutting end of a thread tap
17/01/2017 17:07:15

Having shattered the countersink of a small end-mill (4 mm and under) a couple or three times before I understood correct use of a Clarkson chuck it seems quite plausible that a countersink in the end of a small tap isn't strong enough to reliably stand up to manufacturing loads.


Thread: Lathe motor replacement
15/01/2017 17:18:21

Best practice is to have a switch or isolator on the incoming supply and use the inverter controls for everything else. Easiest, and probably not that much more expensive than DIY, to buy a pendant or control box made to work with your inverter. Wired my own in the past but these days I'd just get the pre-made box, despite having suitable components to hand, saving all the hassle and futzing about. If you are not set-up and ready its an easy 2 or 3 hours to make a box and not that much less to splice something in based on what's on the machine. Just sorting out the which connection goes where can be a serious puzzle for the uninitiated.  Sometimes life is too short!


Edited By Clive Foster on 15/01/2017 17:20:10

Thread: 'Re-purposing' old hand drills
15/01/2017 16:13:32

Re the little springs holding the chuck jaws apart. Last time I needed some the internal spring out of an aerosol can did the deed. For the larger, 1/2", chucks sometimes the spring out of a retractable type ball point pen will do. Seem to be different sizes of these, I got lucky with one smaller in diameter than most.


Thread: Silver solder Oilite bush
14/01/2017 20:14:38

I believe the recommended method of fitting oilite bushes is with a stepped guide tool. First part made a smooth, shake free sliding fit in the hole it is to go in, second part made a touch smaller than the finished size of the installed bush. Second part should be a little longer, 1/16" or a couple of mm is fine, than the bush. First part makes a good gauge for the bore size if your hole measuring equipment isn't really up to the job of making an accurate hole off the dials by direct measurement.

Method of use is to introduce the first part into the hole and apply pressure to the end of the second part. First part aligns things nicely in the hole so when pressure is applied the bush floats back against the pressing device self aligns itself with the hole. It can be pressed in without undue force and no risk of deformation. Helps if there is a slight chamfer on the hole. Oilite bushes aren't very good at resisting deformation forces from being pushed out of line and a re easily cracked or distorted beyond repair.

Like so many things you can get away with less than ideal methods given appropriate care but odds are you will get bitten in the end.


14/01/2017 17:33:45

I know of the oilite bush in loctite fitted sleeve idea being used with every success. Darned if I can remember the application tho'. The sleeve was bored to take the oilite bush with the correct amount of compression to produce an accurately sized bore. The assembly was trimmed to length and locitited into the bored out hole. Possibly marginally less accurate than fitting the sleeve then boring in situ but that way the loctite joint isn't subject to machining and bush pressing in loads.

If done with appropriate care there is probably no practical difference in the results whichever way you do it. Doing the sleeve and bush assembly first before fitting is perhaps less vulnerable to irrecoverable Gremilin interference and (un)common shop mistakes.


Thread: Is it possible to make a hot bulb Diesel engine from a petrol lawn mower engine?
12/01/2017 19:50:10

In principle it should be possible but the engine may end up being too small to run properly. Hot bulb engines in general are hefty beasts with large reciprocating and rotating masses helping to keep them running at their low operational speeds, typically in the 200 rpm range. Plenty of meat in the cylinder heads to help keep the bulb temperature stable. Something based on a Briggs & Stratton may well not have enough inertia to keep going unless the set up is very precise. Which to a degree misses the point of a hot bulb engine which is supposed to be able to run under almost any remotely suitable operating conditions. You could hang a hefty flywheel on but I'm unconvinced as to the durability of a Briggs & Stratton crank and crank case if you do.

Injection system can be very low pressure as fuel is injected towards the end of the inlet stroke or very beginning of the compression stroke. Simple air blast squirting fuel through a nozzle should be fine. Valve timing might be need some work. No idea how you would establish the volume of the hot bulb chamber which is probably a fairly important parameter in a small engine.

In many ways a hot bulb engine finds its own operating point as a sort of balance between, load, set-up, fuel and other things, probably including phase of the moon. Which is why they do fine under long term running at fairly constant load and speed. Once set-up and going well the just keep on keeping on with engine thermal and technical inertia helping to ride out variations. Try and use them for variable speed variable load applications and things can get interesting. Some of the two stroke variations were quite capable of self reversing at lower speed should they feel so inclined. Which could be interesting in applications such as the Lanz tractors.

i have horrible feeling that getting it to run reliably and successfully will need a higher compression ratio and more sophisticated control going some way towards a diesel engine rather after the manner of Ackroyd Stuarts work with Hornsby's.


Thread: bench drill clamping
12/01/2017 14:33:44

Its certainly feasible but whether its really appropriate given the sizes of components normally held in a drill and the relatively high probability of inadvertently adding extra, un-tapped holes is a different matter. I used an aluminium optical breadboard from Thor Labs having 6 mm tapped holes on 25 mm centres as a work-table on my BCA jig borer. Quite satisfactory and a great improvement on trying to fix things to the built in rotary table. But this was primarily for milling relatively small components and very limited drilling for tapped holes and the like. My feeling is its not going to work that well as the normal table on a drill where the primary objective is to get the component with the hole centre under the drill chuck. When you don't have screw feeds wiggling around is usually easier with some sort of one hand operated clamping arm or device to lock the part down once its in the right place.

That said the smaller Thor Labs aluminium breadboards aren't stupidly expensive **LINK**. and one might well be worth the cost as another work mounting option if appropriate for what you do. The anodising is hard and durable. I'd probably not fix it to a machine, just fit when appropriate. Maybe clamp parts down on the bench then take the whole thing to the machine. Many smaller machines are a bit short on space when trying to set tricky parts up.

My pillar drill is an ex industrial Pollard 15 AY with square column and screw elevation so space and weight aren't great issue. My basic work-holder is a 6" cross vice with the horizontal and vertical Vee'd jaw set. For most jobs that won't go directly in the vice I use sacrificial tables made from ex-kitchen cabinet materials fitted with a wide tongue underneath for the vice to grab. Being sacrificial I'm unworried by extra holes, especially as there is a lifetime supply of material up in the shop attic.. A power screwdriver and wood screws rapidly takes care of tricky clamping things. If there is no other alternative I will reluctantly remove the cross vice but that takes a deal of persuasion as its 'kin heavy.



Edited By Clive Foster on 12/01/2017 14:34:52

Thread: "Gas" Threads
11/01/2017 18:28:03
Posted by Clive Foster on 11/01/2017 13:12:37:

Gas threads go on British Brass Pipe sizes and are always little bit over nominal diameter. For example 1/4 has an actual OD of 0.260! 27 TPI on all nominal sizes from no 4, 0.246" actual diameter to 1" nominal, 1.006 actual diameter. 32 TPI on nominal sizes 0.148 and 0.196 which are also actual diameters, just to confuse folk.

All are Whitworth form but there are detail differences in fits and tolerances.


Source Newnes Engineers Handbook, second version, first (only?) edition, second printing 1964.

11/01/2017 17:39:44

Bad though the 1/4" BSF - Cycle mix is the 0 BA male in 1/4" BSF female is possibly worse. Such a pairing of decent quality components will tighten up to a seemingly adequate torque but the actual residual load carrying ability is pretty small. I've seen the fail demonstrated as part of an introductory How (Not) To Kill Yourself With Lifting Gear course devoted mostly to the sort of dangerous mistakes the unthinking and inexperienced can make. If you do the maths the load carrying ability of properly fitted bolts and similar threaded components is scary large to normal folk. Apparently you can hang grand piano of a single 1/4" bolt!

For the sake of completeness its worth mentioning that Cycle threads are 60° flank angle derived in the same manner as 55° Whitworth threads. Preferably made by rolling rather than cutting. The resulting thread form is different to 60° American so even though a US thread may mate, depending on tolerances and fit classes they may not actually go together sensibly despite being same TPI, the pair will not have the specified load carrying or tightening torque capability. If you include spoke sizes there are over 40 defined cycle threads, some rather application specific and obscure.


Thread: Alternative to PC based Cnc controllers
11/01/2017 14:35:21

Do yourself and your tools a favour and spend a weekend gluing 40mm if Kingspan insulation to the underside of the roof.

Better to provide battens or similar positive support rather than trying to jam in or use glue. Kingspan and foam type insulation sheets seem to compress a bit over time so will fall out if jam fitted even if its almost too tight to shove in. Glue doesn't seem to last more than a few years, say 5 or so, against a condensation prone steel roof. Dunno if cause is the damp getting under, near impossibility of getting roof fully dry before sticking, difficulty of getting full glue line coverage as both roof and sheet aren't super flat or just movement as the roof expands and contracts due to sunlight heating. If it is expansion and contraction might do better with big blobs of silicon rather than glue as being a bit more flexible.

Gotta bite the bullet and re-do my glued on steel insulation in the shop and the jammed in Kingspan between the rafters immediately underneath my new roof. Both done by builder types, with my assistance, disregarding my opinion that the job wouldn't last. No fun in "I told you so" when it means a ton of work for moi to fix.

That said such insulation really makes huge difference. Maybe halves my shop heating bill compared to relying on the 4" of insulation in the walls. Similar effect on heat losses through the house roof. Post extension new roof area pushing double old roof area yet losses through new one are similar to, probably bit less than, old. No regrets from jamming my pedal extremity down and assisting that both be done.


Thread: "Gas" Threads
11/01/2017 13:12:37

Careful. You can get in a right mess with oddball, but officially listed sizes for this sort of pipe fitting thing.

British Brass Thread (not British Standard Brass as there is no official standard) is 26 TPI on all sizes. Overall diameter is nominal size and tapped holes should be to 90% thread depth.

Gas threads go on British Brass Pipe sizes and are always little bit over nominal diameter. For example 1/4 has an actual OD of 0.260! 27 TPI on all nominal sizes from no 4, 0.246" actual diameter to 1" nominal, 1.006 actual diameter. 32 TPI on nominal sizes 0.148 and 0.196 which are also actual diameters, just to confuse folk.

Then there is copper tube thread covering nominal diameters from 1/8" to 4". 28 TPI on 1/8", 20 TPI from 1/4" to 1 1/2" in 1/8" intervals except for no 1 1/8" or 1 3/8" sizes. 16 TPI thereafter in 1/4" intervals.

All are Whitworth form but there are detail differences in fits and tolerances. Probably not enough for us to worry about except maybe the oversize on Gas threads.

I know of no book or reference which has them all in proper detail I had to scramble through three books although two would have done for this.

Whilst we are at it one more little ID nightmare courtesy of the inexpensive Asian import folk. I've run into a couple of air fittings using Admiralty thread sizes but using UN/Metric 60° form instead of Whitworth 55° to make life that bit harder.


Thread: Air supply for chip blower
11/01/2017 12:34:04

Maybe one of the square cooling fan assemblies used with computers, power supplies and other electronic gubbins would be sufficient if connected to a suitable funnel and tube assembly. Those things are made to run all the time and even the smaller ones shift a fair amount of air. Big question will be whether you can feed the output into a small enough tube to get a usefully powerful blowing jet without creating too much back pressure and seriously reducing the amount of air delivered.

I think RS or one of the other industrial suppliers used to provide graphs and formulae for this sort of calculation to verify that enough air could be delivered when venting was limited.


Thread: Record No.3 vice
11/01/2017 11:12:51

Ultimately such bench vices are all about getting the mating jaws to line up against each other for a good grip. Having the moving parts a "rattling good fit" lets the various parts shift around as required for self alignment and maximum grip as the jaws clamp up. Such self alignment makes the device very tolerant of abuse and harsh use. With a good bench vice you are paying for proper base material, proper manufacturing methods and proper heat treatment to withstand the efforts of Bubba & Co.

For a bench vice the exact position of what you are holding generally doesn't matter. It just has to stay put whilst you operate on it. Grip is all. Different for a milling vice where workpiece position is as important as grip so everything has to be tight and move in accurate alignment.


Thread: Alternative to PC based Cnc controllers
10/01/2017 18:39:41

The folk in your first link, Adtech, have a UK stockist and associated website. This is the page for the controllers; - **LINK** .

They sell either direct or via E-Bay. Prices don't seem remarkably different from direct import, unless the VAT and duty thing has been "fudged" by the direct supplier. Don't forget that not only are you supposed to pay VAT and duty on individual import but also the delivery company makes a significant change for collecting the tax. Paying a bit more for local delivery and support is probably worth it given just how complicated retro-fit can get if things don't hook up relatively simply. They also supply servos and drive kits so, presumably, you get a turnkey package ready to fit and certain to work assuming you get the wiring right. Having downloaded the various manuals for direct from China units I figure guaranteed to work is worth a couple or three hundred pounds over ordering what ought to go from on-line specifications. In wage slave days I had a certain professional background in similar sorts of stuff so I don't frighten easily but full DIY looks too much hassle. Mimbling around t'net I'm amazed how hard folk are willing to work in order to get something going. Maybe its age but I expect this sort of computer stuff to just work. OK it might not do exactly what one might expect but it should at least do its thing like the book says.

Major question mark for any of the sophisticated systems is availability of posts for CAM software. Fusion 360 looks to be the most likely requirement for neophytes.


Who's is currently taking a serious look at going from a manual Bridgeport to proper CNC in the near future.

Edited By Clive Foster on 10/01/2017 18:56:10

Edited By Clive Foster on 10/01/2017 18:56:51

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