Member postings for Clive Foster

Mikes strategy of keeping tools and shim sets together in a divided box is undoubtably effective but takes a, to me, terrifying degree of super organisation.

No way could I mange that so pre-loaded posts were the way for me.

One advantage of of pre-loaded posts over swopping tool and shim sets in a single post is that tool projection distance settings are retained. Just as with a QC system. So if you have to make several parts needing tool changes during a job swopping posts rather than tools means you don't necessarily have to reset the dials after each change. Probably best to verify before the final cut on a precision part tho'.

Clive

As I understand things universal motors supplied for AC use can easily be re-configured to run off DC.

If, as Malcom says, it is connected directly across the 110 V supply using only the positive half cycles its never going to do well at low speeds.

Proper electronic controls for "90 V" nominal DC motors are relatively inexpensive these days. Starter price maybe £150 at the affordable end of full on industrial rated ones with rather more output than you need. Probably £50 or less in the lower end, but still decent, import shops but I've no familiarity with what can be found there.

A proper control with feedback and feedforward onboard is enormously better than a simple half wave supply at low speeds.

Due to the characteristics of universal motor half wave works pretty well on a faster, well loaded, motor such as a hand drill. Not so good on lighter loads intending to deliver constant speed.

Clive

+1 for the multiple identical 4 way or 2 way posts as an effective alternative to a QC system for the impecunious person.

Way back in my Southbend driving days I had four 4-way posts kept ready loaded with tools and simply swopped them over. Before the ready availability of import equipment. Only industrial quality QC posts were around. Totally unaffordable for me so I had to get creative. A little easier with a SouthBend because it has a T slot in the topslide so it's only necessary to loosen the top nut to release rather than undo it completely.

In practice I found that loading only two tools at a time worked better due to less porcupine effect and more freedom to adjust extension.

Shimming tools to height is much easer with removable 4 or 2 way because it can be done on the bench by measurement. Needs a set of sorted shim sizes. The colour coded plastic shim sets are a great help. These days I'd make a permanent gauge with an inexpensive plunger indicator fitted with an elephants foot on the end in simple fixed holder to measure in situ. Back then I used my second best vernier to measure the tool directly and worked out the shims needed to match the known centre height of the lathe.

Perfectly satisfactory toolposts can be made by gluing and screwing stock sections of plate and bar together. I used 5 or 6 mm countersunk head screws and tapped the centre block right through for them. Alloy is fine for the centre. In retrospect I should have made two way posts as being more compact.

One advantage of the DIY approach is that you can make the baseplate the right size to use insert tooling without shims.

I now use a QC system because my current lathes came so fitted but you do need enough holders to keep a good selection of tools mounted if the advantages of QC are to be realised. I usually have between 12 and 16 holders filled ready to go. Helps that both machines are set up to be interchangeable.

It is said that 8 is the minimum satisfactory complement of holders given that one will be dedicated to a parting tool and at least one to a boring tool.

Even on my big machines the sheer bulk of the QC post can be a problem as it sometimes gets in the way. Mostly when the tailstock centre is in use.

Prior to (and since) changing lathes I've devised a number of simply made ways to make releasing a bolt down toolpost by around 1/3 rd of a turn of the hold down screw to eliminate the prime speed disadvantage of block changing relative to QC posts. Never made any tho'.

Blocks tend to make it easier to accommodate relatively large, stiff, boring tools. Simple drilled hole on centre height to hold a round bar is strong and effective. Swanky folk interpose an eccentric sleeve for height adjustment.

Clive

Edited By Clive Foster on 24/07/2023 13:02:44

Could be a driver issue. DC motors are inherently pretty good a delivering steady torque down to low rpm but it does need a decent driver to realise that capability. Simple voltage control schemes without proper feed forward and feedback balancing tend to have problems at low rpm.

Clive

I have a commercial set of airline accessories that includes various 1/4" BSP adapters and couplers. Taper threads on the males, parallel on the females.

So I guess the mix is acceptable. Not had leaks yet using loctite, plumbers mate or old fashioned heave it up good'n tight methods.

OK it's a cheap set from LiDL but I've found LiDL airline components to be of more than decent quality and excellent value. Not terribly impressed by the airline supplied but at the kit prices I'm still saving serious money over the usual affordable suspects even if I never use the airline.

Clive

Baldric

Is there any possibility of fitting a "bare" magnetic strip system to the taper turning attachment?

I'd envisage a steel or alloy plate fixed to the top of the attachment overhanging one side yet narrow enough so as not to interfere with the nut or bolt that holds the attachment slider when in use. The magnetic strip being fitted under the plate so as to be adequately protected with the reader mounted facing upwards on suitable bracket overhung from the saddle. I'd imagine 3 mm or 1/8" would be thick enough for the plate. Probably need to make your own compact reader case tho'.

If such a system could be finagled in you'd probably have to accept that setting the taper attachment would become rather more fiddly.

Clive

Roger

Shouldn't be any wear issues with only one half nut on a hobby lathe. A fair number of respected industrial machines had that configuration with no reported issues of premature wear.

Colchester and Kerry are the two makes I have experience of having actually seen such nuts in perfectly useable condition after significant use.

Nut wear is frequently an alignment issue. The requirements are surprisingly stringent and, given the constructional layout, quite difficult when a lathe needs to be made to sell at a hobbyist friendly price.

Clive

A frequently overlooked point when using smaller tooling in larger toolpost is centring the tool under the clamp screws.

I have a batch of sharp inner corner angle L sections made up by welding two strips together to do basic alignment of smaller tools. The back, upright face being of a thickness that pretty much puts the clamp bolts on the toolbit or shank centre line and the underneath face thick enough to put an unground HSS toolbit or insert in its holder at the lathe centre height.

Makes life much easier as the tool with its intervening angle section can be pushed hard up against the back of the toolpost slot so the position is repeatable and the tool unlikely to move.

If going down to significantly smaller tooling, 6 mm in a slot made for 12 mm it may be better to machine the L spacer as the side needs to be shallow so it doesn't foul the bolts. Both side and base have to be quite thick too.

Frankly on a lathe of that size an HSS tooling made from 6 mm tool steel with be entirely adequate. Armstrong / J&S et al holders for Boxfords and the like used this size.

Clive

Edited By Clive Foster on 21/07/2023 19:13:08

NDI

I'm glad you like the idea.

Overall length isn't an issue because you always push the tapers fully home. Small errors in relative taper diameter merely alter the actual interference ached slightly. In practice it's far easier to get very close to what you intend that it is with a standard parallel fit.

To my mind the great thing is you can see exactly what's going on as you bring things to final size and adjustments are feasibly measurable.

Who can guarantee to take 1/2 or 1/4 thou off parallel shaft or hole? Even with the angled topslide trick and a lathe in first class order.

In principle the final cuts for self gauging tapers are effectively an extreme example of the angled topslide trick.

Worst point is that gauging and setting final diameter by longitudinal movement along the taper makes the relationship between cut and diameter a bit unintuitive. Which is why drawing out and calculating first is a good idea.

The angles simply fall out of the length of the fit / taper. Basically during set up the DIT movement as you traverse along the test bar needs to correspond to the fit. So if I want 1 thou of interference over a 1/2" long part I'd set-up for 8 thou over 4 inches using the taper attachment. If you are using the topslide 4 thou over 2 inches is probably practical.

Which is sensible magnitude of measurement. Even you only have a Unique indicator and an old Drummond.

Clive

Edited By Clive Foster on 21/07/2023 11:49:40

Shrink and interference fits are reliable and theoretically easy to do but, as a has been frequently discussed, getting practice and theory to align in the home workshop can be hard.

Realistically very few of us have the equipment to accurately and reliably measure to the tolerances needed for known shrink fits. Getting something to grip isn't too hard but the actual hoop stress, and therefore grip achieved, is somewhat in the lap of the gods. It doesn't help that, as Fulmen said in a recent post on a related thread, our parts are usually small so rapid heat loss and the concomitant tendency to self ream part of the joint if cooling is too rapid as the fit is made adds uncertainty. Small parts with small wall thicknesses tend to stretch too.

It's important that stresses in the material don't drive it past the elastic limit when a shrink fit cools. Again not easy for most of us as not only don't we have the maths and metallurgical knowledge to properly evaluate things the exact provenance, specification and heat treatment of the materials we have to hand tend to be uncertain. Given this it's risky to aim for high levels of interference fits.

For the inexperienced attempting anything seriously stronger than loctite is likely to be unsafe.

Self gauging tapers are an effective and relatively easy way of reliably achieving a known interference fit.

The two components are made with shallow tapers such that when offered up cold the male taper only goes part away into the female taper yet when pushed fully home the desired interference fit is achieved.

Usual practice is to make the taper over the full length of one side of the part equal to the desired interference so when offered up cold the tapers engage over half their length. Obviously the total interference possible over the whole length of the taper parts is double the desired fit but as the tapers start off half way home the actual fit corresponds to what is needed.

There are various relatively simple methods of creating matching male and female tapers from one set up on a lathe. Mine have taper turning attachments and camlock chucks enabling safe reverse running so dead easy for me. With screw on chucks you need to use an inverted tool for one side. If you don't have taper attachment it's wise to arrange some form of screw driven adjustment so as to accurately set the topslide.

Best to use a test bar as a reference and use a decent amount of travel. Even when using the topslide a couple of inches or more should be safe making it relatively easy to set a taper very close to that theoretically desired.

As this isn't something you do every day its advisable to draw things out first time through as the small offsets can make it confusing to see whats going on. It's also worth tabulating the adjustments needed to bring the tapers to the final mating lengths.

Due to the small taper angle the longitudinal adjustment needed to take half or quarter of a thou off to get the initial engagement right is usefully large. If you are using the topslide the error resulting from moving along the taper rather that along the bed will be inconsequential.

The method is quite tolerant of small errors. Half engagement is what you are aiming for but 1/3 rd or 2/3 rds will be good enough. In practice its quite difficult to end up with a bigger error given the usual modicum of extra care needed for the precise bits.

I first encountered this on a Velocette Thruxton camshaft drive. Some dinkle brain had pushed cams and camwheel together incorrectly giving the wrong timing. Pushing the pair apart and getting it back right was satisfyingly easy. Due to the tapers a hand push before pressing ensured things were inline.

Accurate alignment of parallel fits can be tricky.

Clive

Edited By Clive Foster on 21/07/2023 09:44:13

Effective though it is when in proper working order I always felt that Colchester motor control system was a little too clever for its own good.

I appreciate the probable operational advantages over a simple three push button system. Especially when used by an operator under pressure to meet production targets as it is clear which way the motor is running. It also eliminates any possible wrong button pushes going direct from forward to reverse without passing stop. That said my Smart & Brown 1024 with its three button system does the same thing electrically at, I think, the cost of extra contactors.

Given the known long term fragility of the mechanism I'd junk the whole thing. Options then are :-

1) Do a standard 3 button set-up with the usual microswitch train for safety turning the motor off or inhibiting re-start when covers are open et al. Requires a button box on the front instead of the lever which maybe aesthetically unacceptable.

2) Re-work the lever mechanism to have sprung detents at the nominal Forward-Stop-Reverse positions with over travel against a respectably strong spring to operate microswitches selecting run direction. Naturally the stop position actuates a third microswitch permanently interrupting the contactor coil supply when Stop is selected. Aesthetically and operationally invisible. Personally I'm in favour of a really positive action being needed to start a motor.

Whilst you are at it I'd replace all the contactors with modern DIN rail versions. They aren't silly expensive these days and are much easier to handle. Aged overload switches are notorious for occasionally being fracticous. Probably a combination of dust, workshop air stuff and never moving for years at a time.

I'd also shell out a few extra drinking vouchers for box on the back to hold the contactors so you can easily get at things when connecting up. My patience with neat, tucked away connections with screws you can't quite get a driver on dead straight ran out about 40 years ago! When it comes to electrics accessibility beats aesthetics any day. Not to mention that it's much easier to make a mistake when you cannot clearly see what you are doing.

Clive

Andrew

0.3150 is 8 mm.

Possibly 8 mm fine which can be 1 mm pitch.

I'd not care to try distinguishing between 24 tpi and 1 mm pitch without my excellent bench magnifier with its built in light.

Confusingly 0.75 mm pitch is also listed for 8 mm fine.

Clive

Disclaimer :-

I own a Bridgeport but I'm Home Workshop Guy, not Model Engineer Bloke, and pretty much everything I do is in 12 inch to the foot scale AKA full size.

The primary attraction of a Bridgeport in a home shop is that it can handle pretty much anything that can be reasonably lifted onto the table by a solo worker and get a cutter into anything that can be put on 2D drawing comprehensible by an ordinary person. The really tricky stuff being left to the Deckel and Thiel fraternity!

As such a Bridgeport makes an excellent sanity check comparator before finally pulling the purchase trigger on a machine that you think will not only be able to do the jobs you envisage but also have some capability to cope with the unexpected.

The basic question being what can a Bridgeport do that my provisional choice can't.

It's easy to miss things when concentrating on spec sheets with the "can do" vision filter in place. Turning it round to make a "can't do" question relative to a hopefully over capable reference gives a different viewpoint to flush out any errors.

For example:-

"Do I need a 49 inch table when the largest parts I envisage are only 6 inches long?".

Probably not but setting parts up on an angle can seriously burn up table space. That one bit me when I thought a 28" table square column bench mill would do. Hence swopping in a Bridgeport. Of course now I have the bigger machine the work I do has expanded to meet capacity. I'll admit that a 14 ft long job was stretching the envelope a bit and relied heavily on a strategically positioned workshop secondary door!

It's quite likely that a smaller machine may be up to the job.

I was impressed by the metal removal capacity of the square column mill I had which was of very similar size to the aforementioned Sieg 3.5. Its rare that the Bridgeport gets worked harder, blizzards of chips I can live without, but it turned out that too many jobs just wouldn't easily fit.

At least if you do the analysis and find only a Bridgeport will do you will know why.

However you may also be inspired to figure out a different approach which, metaphorically, fits a quart into a pint pot. Normal territory for Model Engineers whose jobs are frequently much larger than industrial practice would put on a machine of the available size.

If you think that may be a possibility just ask here.

Someone will have done similar things with an officially too big part.

Clive

Realistically with any Bridgeport equivalent mill the table can easily take the weight of anything you can manually lift on to it with a decent margin for tooling.

I've never gotten my Bridgeport loaded up to the point where the lift screw becomes significantly harder to turn. And its had some pretty hefty stuff on it!

Clive

Duncan

Prof Gordons books "The New Science of Strong Materials" and "Structures, or why things don't fall down" are still in print and available from Penguin.

Hardly surprising as they give an excellent explanation of how such things work with just the right amount of science for the ordinary intelligent reader to understand why things are the way they are whilst remaining accessible to just about anyone with an attention span long enough to cover 4 or 5 pages.

True classics and unlikely ever to become outdated.

Clive

Dave

Sounds like you are flirting with GD&T.

Geometrical Dimensioning and Tolerancing.

The modern way of going about things that seeks to unambiguously and accurately define all such infelicities working from sound theoretical principles. I guess it's fundamentally aimed at sorting the confluence between CAD, CNC and machine inaccuracies. Workable in computer space where all is defined I suppose.

Presumably the way that attempting to follow GD&T causes normal workshop folks brains to leak out of their ears in short order is just one of those unintended side effects.

The book I looked at left normal English usage behind about midway through chapter 1 and by the end of chapter 2 was accelerating rapidly over the comprehension event horizon at a rate likely to crack the light speed barrier before the last page.

The quick introduction guide sounds so simple and logical then ....

Clive

Smart job.

A little surprised you didn't take the opportunity to add a thumb lever style slide lock screw in Geo. H Thomas style.

So nice to be able to leave the gibs that smidgen looser so things run easily for accurate setting, but is still secure enough for ordinary jobs, with the lock to hold against heavy jobs.

Clive

Edited By Clive Foster on 05/07/2023 07:23:13

The bearings do wear, unsurprisingly, that allows things to move off line. The one we had in or little local section trials prep workshop at RARDE had noticeable rock but the saw still cut adequately. Albeit less square than we'd ideally have liked.

Modern plastic faced belts are potential issue as there tend to need both more tension and a higher surface speed to transmit useful power. The saw was designed and developed to use a leather or leather faced fibre backed belt.

if I had to replace the belt on one I'd change the motor pulley to poly-Vee and keep the standard flat pulley. The soft Vee side running on the big pulley will transmit enough power just fine at surprisingly low tension.

Doesn't help that power transmission nis inherently a bit on the marginal side to so the drive slips if the blade jams up rather than break. They were designed for site work where a certain degree of careless handling is inevitable.

Clive

Rule 1 with questionable E-Mail these days has to be having things set so you can see the actual source address not just the response address.

I got the same one as Chris this morning, albeit with a different name to reply to, but the source address was clearly nowt to do with BT.

It really is pity that there appears to be no way of holding only approved E-Mail addresses for firms et al so such scam are automatically filtered locally. It would seem a fairly trivial job at your E-Mail provider end to filter on that basis given a small amount of text analysis or keyword recognition. That said I think BT does aprtetty good job for me as its rare to actually see a scammy mail in my inbox.I get a few a week in my junk box "Apple mail thinks this is junk" presumably marked up by BT as questionable. Probably only one genuine mail marked up a junk every couple of moths so things seem to be working as well as could reasonably be expected.

Clive

Clive Brown

Hafta disagree about the need for a damper in working order.

Ran mine for years with the damper in as purchased setting, assuming as it came out of as proper engineering shop it would have been about right, and wasn't greatly impressed as it didn't seem to do much in the way of blade lift on the return. Eventually it stopped doing anything at all.

Initially I assumed I'd just pushed some of the oil out over the years when lifting the saw bow when some resistance could be felt. Fortunately I decided to investigate before refilling. Found the spring at the bottom adjusted to coil bound and the needle doing nothing so effectively the valve was more like a cork in a bottle than a damper. After some head scratching I figured out how it should all go. Set the spring to a moderately low tension so the plate could move, guessed at a sensible tilt setting for the plate and filled it with ISO 32.

It now does what it should giving a nice force reduction on the blade on the return stroke. Clearly it never been in working order in my ownership before.

Clive