Member postings for Clive Foster

An oft overlooked gotcha with parting off is that the chip is wider than the groove cut by the tool. So the depth of cut has to be shallow enough that the chip can deflect or bend on its way out. If the chip is too strong it will jam up and, at best, seriously mark the work. At worst a major smash up and "unfortunate" language. An especial issue when the tool is cutting square rather than at an angle.

The insert type tools have concave top, bending the chip to make it narrower than the slot so it falls out easily without marking. Not a universal panacea, as I was reminded a couple of days back when hand parting off the first of several components from 50 mm alloy bar. Got a bit too enthusiastic and, even after bending, the over thick chip was still enough wider than the tool slot to seriously mark the cut faces.

Ooops.

Checking the book and setting power feed to the correct depth of cut I realised I had been feeding about 3 times too fast. Instant disaster on a Myford or smaller machine. My hefty S&B 1024 just shoved the tool through with a complete lack of drama.

Clive

Sedimentary my dear Robert.

The drill sharpening device one my Clarkson Tool and Cutter grinder has a 6 jaw chuck to accurately hold all the drill sizes within its range. 6 jaws are needed to retain concentricity when gripping on teh webs. The sharpener rotates to generate the drill point so, presumably this geometry requires the drill point to be concentric to the rotation axis regardless of size. A simple Vee trough and top clamp will hold a goodly range of sizes but the point height must vary with size.

Clive

Edited By Clive Foster on 23/03/2023 14:05:01

+1 for Andrews broom with considerable assistance from an industrial version of Henry.

The mister provides a low power air blow when needed to keep the chips out of the cut and, occasionally, oil when needed. I do make an effort to keep chips brushed off they work and onto the table during the job, pausing as appropriate. Frequent wielding of the vacuum cleaner to pick chips off the table helps a lot.

I have got an industrial "flexible" shielding system that magnetically mounts to the Bridgeport table but pretty much never use it as it gets in the way so much during set up. Table mount systems may make sense when doing repetition work so no set-up needed after getting things right on the first two or three. But thats not what we do.

The only shield totally worth having is something effective at the back of the machine so chips don't disappear behind.

Bench mill users might do well with fold out wings connected to the back shield to keep chips on the bench close to the machine. Two or three folds probably best so they don't close off useful fast space when the machine isn't being used.

Clive

Howards contribution concerning tightening to yield convinces me that we really need better terms to describe how stretch bolts behave. When an ordinary bolt or stud is taken past its elastic limit it pretty much looses all ability to recover and stays stretched. A stretch bolt or stud is still capable of elastic recovery after yielding. It can't go back past the yield point but it still recovers elastically within its working range.

Which is why they are so popular and effective for things like head bolts on alloy engines, like the venerable pushrod V8 in my Range Rover. If the bolts didn't recover all head gasket pressure would be lost when cold after about 4 or 5 starts due to stretch from differential expansion when the engine is up to operating temperature.

The old Rover V8 is an excellent example of why correct installation ensuring the stretch bolt is always within its correct operating range is so important. Combine over torquing and with overheating and the bolt will go out of range so the head gasket fails. The margins are surprisingly slim too. Pushing the operating temperature up from 95°C to 100°C and restricting cold coolant flow to meet emissions requirements shifted the Rover installation from bullet proof to occasionally unreliable. The extra stretch between 95° and 100° is very small but just enough, when combined with stretch bolt production tolerances, to eat up the margins.

Clive

Edited By Clive Foster on 20/03/2023 10:28:40

To me the biggest worry on this is how poor the OEM components from the design rights holder are.

Component manufacture and materials specification standards for a simple component with no specified life or an inspect before re-use requirement on something like this should be so high that failure without gross installation abuse should not be possible unless the component is defective.

Fairly obviously such standards can be easily met by off the shelf replacements without any side effects so continual supply of known to be (occasionally) inadequate components is inexplicable. There is little doubt that the maintenance community for these motors knew, grapevine communication is pretty effective and fast, that stud failure did occasionally occur and were prepared to change them as required.

Given this knowledge either maintenance instructions should have been modified to life the studs "change after X hours or every Y overhaul" sort of thing or materials changed to give effectively infinite life.

Clive

Edited By Clive Foster on 20/03/2023 10:28:03

Ignatz

Thats an excellent point that probably can't be settled until someone tries it successfully.

My view is that so long as the actual knurl points appear to be the same size the changes in the number of points in each circle as the circumference of the handle varies will be seen as natural.

On a parallel workpiece you see straight lines along the job where knurl points at the same angular circumferential position align. Think of a stack of same size gears with the teeth lined up. This, probably, enhances the perception of straightness so long as the knurling depth is identical and the points the same size.

On a gently curved surface, like that handle, the corresponding lines will be curved as the knurl point row alignment diverges or converges to accommodate extra points per rev where the dimeter increases and loose excess points where it decreases.The depth of knurl and absolute size of the points will change slightly during this process to make space for extra points or remove excess ones. In practice for any reasonable combination of knurl size and workpiece diameter this difference in depth and therefore point size is very small.

Providing the knurl points are not perceptibly different in size these curves will enhance the perception of handle shape and look "right". Using patterns to alter the perceived shape of objects is an old established decorative technique. For both aesthetic enhancement and obfuscation.

I suspect that if the knurl point sizes become visibly different on a row to row basis the change will stick out like a sore thumb and, as you suggest, its going to look horrible.

Totally impractical of course but I do wonder if manipulation of knurl depth could be used to increase the permitted rate of curvature before it all goes to pot. There is an extensive literature on what happens to patterns when the curvature of the underlying surface changes. Some heavily mathematical concerning manifolds and some eyewateringly visual concerning decorative effects. Neither of which should be indulged in by any normal person, especially not on a dreary Monday morning, as being likely to be seriously injurious to personal health, wellbeing and sanity.

Brains leaking out of your ears or eyes popping out of your head!

Your choice.

I'll go with neither.

Clive

Edited By Clive Foster on 20/03/2023 09:54:14

pgk

Interesting idea but I suspect the spring may need to be impractically strong.

Handwaving estimate of my squeeze force on the nutcrackers feels like something approaching half maximum and effective leverage ratio, taken from the single knurl pivot pin to the middle of my hand, around 5 to 1. According to Google health male grip force is a bit over 70 lb - 32 kg. So something approaching 150 lb - 70 kg of squeeze to make a nice knurl in steel doesn't seem unreasonable. In practice you'd be doing several lighter passes rather than one full knurl one so less force ought to work. But you need a decent squeeze to make anything happen at all so I'd be surprised if you could get away anything less than around 100 lb - 45 kg force on steel or brass. Maybe a softish alloy would be OK with less.

The corner dig-in on steeper curves issue still looks intractable.

Clive

Irbailey

Need to lean it a touch and push slightly sideways to make it move along. It's a feel thing really. Given the right mix of squeeze force with a modest push and gentle lean it walks sideways very controllably.

If you hold it dead square when you squeeze it stays in place. Just the ticket for doing knurled head screws.

Toolpost mount types you feed side to side using saddle feed. On lighter machines its probably better not to try and make a full knurl in one go.

Clive

Thinking about my experience of using the hand held squeeze knurler device mentioned by Bizibilder it might be possible to keep sufficiently even pressure on the tool to create a good looking knurl by twisting the tool slightly so it runs from side to side. The technique works fine on a long(ish) parallel shaft.

Can't see any reason why it shouldn't follow moderate slopes and curves. Obviously if the slope is too steep or the curve too great it's going to dig in. Given an adequately shallow curve or slope it obvious issue is keeping the right level of pressure on the tool as it runs up and down the the cuve. I imagine it will take several strokes to form the knurl squeezing harder with successive runs. For ordinary small knurling you just squeeze until the knurl looks deep enough.

Here is a picture of the tool Bizibilder refers tor :-

Certainly hasn't been made for years and rare then. Found mine maybe 40 years ago in the "going to throw away" box at an experienced machine tool and tooling dealer who didn't realise what it was and how effective it could be. Having used one I knew better and gladly handed over an extra £1 for it on top of the price of the big Pollard drill I went to buy.

Minor correction to what Bizibilder said. The screw sets the squeeze depth not the clamping load. I'd think screw clamping could be dangerous if the tool gets away from you. Although the adjustments imply it can be set to handle work over 2 inches - 50 mm in diameter I find it starts getting cumbersome over an inch - 25 mm or so. But what it does do it does really well. Had to knurl some 6 mm pins to fill some no longer needed holes in a part being modified yesterday. Longest party of the job was finding some stock and mounting in the lathe. Squeeze and repeat 8 times gave me 8 pins 10 mm long ready to tap in.

Links to drawings and build instructions for that and couple of similar ones in the thread linked to by Bizibilder.

Clive

Edited By Clive Foster on 19/03/2023 15:52:05

Very interesting reading.

Its impressive how the spiralock system spreads the load over more threads, I'd always thought that system to be a little gimmicky. In comparison the standard thread loads up the first thread much more so clearly things can unzip if the first thread fails and there aren't enough threads to leave at least one carrying effectively zero load to take up the slack.

Checking torque setting tables I wonder how many smaller threaded fasteners are routinely over-tightened. Typically ordinary fasteners of the size discussed in that report, 3/8 - 24, should only go to around 15 to 20 or so ft-lb.

Looking at the sections reduces my faith in the oft repeated statement that using lower thread engagement percentages for easier tapping makes little difference to the strength of the thread.

Mrs Google (Google knows everything so she has to be female!) finds some rather nice graphs from Engineering toolbox illustrating the effect of size and material on recommended torque. I'm minded to do some printouts as graphs give a much clearer view of relationship s than tables although tables are more accurate for individual sizes.

Clive

Basically either :-

machine equal amounts off each side

or

anneal it by heating to red and allowing to cool slowly.

Bright steel bar is finished to size by rolling which locks up stresses in the outer layers of the material.

Machining on only one side takes out the stressed layer on that side leaving the other side still stressed. So the bar bends.Machining both sides equalises any remaining stress so it stays straight. Holding it so you can machine both sides without it moving mid job due to inadequate grip or taking out the bend when remounting to do the second side can require creativity.

Heating to red (all the way through) and cooling slowly lets the stresses work themselves out as the material cools. Rather easier during open fire / soil fuel boiler days as you could dump it in the fire of an evening to get hot and retrieve it from the ashes the next morning when it had cooled down. These days you need to pay for gas to heat it and have something to bury it in for slow cooling.

Clive

PS Jason types faster! That said I'd want it red for longer and very slow cooling. These days some of the bright bar seems to have had a lot of rolling and lots of stress. Several itty bitty cuts are a good way to shorten the life of milling cutter too. So glad I have a shaper! I've been known to weld such pieces to a larger parent bar to keep them straight. Costs you the ends where the weld was but can make life very easy.

Edited By Clive Foster on 17/03/2023 19:03:36

If it's the old style MEM unit with an auto - manual switchable reset overload detection device it's worth verifying the unit hasn't decided to switch all on its ownsome for no discernible reason.

Such self switching after many years of doing nothing at all is a known, albeit moderately rare issue. A goodly spray with switch cleaner and operating the auto - manual switch a few times sorted one on my Bridgeport about 7 years ago. Sill going strong. If it happens again the whole lot are coming out to be replaced by modern mid-range DIN rail relays.

It may also be simply dirty contacts on the coil switching side. Old style MEM and similar vintage are relatively easy to strip and clean. Coil control contacts only carry a small current and tend to be little vulnerable to contamination over the years.

If it really has died, basically coil going open circuit is the only thing that will permanently kill an old one, as opposed to too much futzing to fix, get a short piece of DIN rail and a mid-range DIN fitting replacement. Anything from an industrial supplier or brand you have heard of will do. Probably around £30 to £50 the pair. CHINT come up as cheapest contactor at around £15, I have some off their other products which seem OK. Would be willing to try one although my last such purchase was Schneider.

Clive

Edited By Clive Foster on 16/03/2023 13:26:00

Jason

With only 1/32" held how the devil did you get the job running true?

Nearest I ever came to that was with an 3/32" long spigot on an asymmetric and non circular flange that needed the hole in the middle enlarged. I blessed the original maker for putting a teeny undercut at the junction so it sat flat against the face of the collet.

A job for one of the "gash" set of Harding 5C collets I bought for "£ not very much" in the days before I learned proper E-Bay caution. Clearly retired from production duties, probably from a Tier 3 shop, most have lost their spring and don't open properly, maybe half have internal taper in greater or lesser degree and some are so badly distorted that there is visible error in the angle between the main shank and the taper. Lord knows what they were tightening the things up with. Surprisingly concentricity was still very good but the various errors and tapers vastly compromised grip. Which I found out they hard way after a job that needed to be real nice spun! Concentricity great, I checked first, grip crap. Fortunately most of the 1/64 th s are still pretty good.

Clive

General rule with collets is that the parallel, gripping, part inside the collet must be filled for proper, stable, grip.

In the absence of measurements its usually OK to assume that so long as the workpiece goes in a bit further than teh depth of the outer, large, taper things will work correctly on unambitious jobs.

Trying to hold a very short piece and ramping up the pressure to get things to hold is a quick way of messing up a collet. They are not as robust as they look at first sight. There don't seem to be any official figures but I imagine 20 ft lb would be as high as I could sensibly manage with the hand wheel closer on my lathes and the shoe C spanner with my collet block. What I actually use is less.

Clive

Nicola

Google turned up a French mortice lock that might be what you desire.

Called the Metalux 33 it's a narrow fitting mortice lock whose data sheet implies that works off a half turn of the handle.

See :- https://www.dom-security.com/fr/en/products/metalux-33

Google also came up with an outrageously expensive supplier :-

https://a2pro.com/en/single-point-recessed-lock/1493-metalux-series-33-half-turn-latch-only.html#/1-sens-poussant_droit

If it is the right sort of thing maybe it can be found at a more realistic price.

Clive

Ask a good lock and security specialist shop about long throw key operated bolts and auxiliary garage door locks.

I have a garage door one that goes through up to one and a half turns to throw the bolt. Key is cross shaped and, on mine, can be pulled out at half turn intervals so the bolt doesn't have to make its full throw. As I recall it there were others with both more turns and less turns available. That one had the throw I needed.

Doesn't seem to be available now but it looked rather like the Asec AS1997 that can be found on Amazon or as the ASEC Garage Door Locking kit from Lock Shop Direct.

I imagine the gubbins can be pulled out and modified.

Big key so handbag rather than pocket!

Clive

Dave

Keyless chucks for ordinary drills are very different animals to those used on proper workshop machines.

The proper type self tighten under load and loosen slightly, basically just enough to let you undo the thing, when the load is removed. Any attempt to use one like that on a hammer drill will cause it to undo instantly.

Ordinary drill style keyless chucks are just cheap hand tightened versions of the familiar keyed chuck slight geometrical differences that allegedly give a small degree of extra grip under load. Never seen any evidence for the self tightening myself.

If one of those is to stay tight when used with a hammer drill it must have locking facility otherwise the hammer action vibrates it undone very quickly. Some have an extra ring to engage the lock, some just go "click, I'm locked" when you securely hand tighten them. All the ones I've used are of the latter type, none have been very good. Makita cordless standard fare are good for about 4 holes when new but rapidly deteriorate. Mine are down to something between 1/2 and 1 1/2 holes in hammer. So I got a compact Makita battery cordless SDS drill, type DRH242Z, and never looked back. Affordable if you already have batteries.

Clive

Standard correct answer is to use a decent quality test bar in the spindle taper, fix an indicator to the top slide so it touches the bar and traverse it back and forth. Adjust the cross slide angle until the indicator reading doesn't change during traverse.

Alternative is to turn a temporary test bar held in chuck or collet and use the same procedure.

Turning two collars using the topslide or turning a bar and checking the diameter is the same all the way along is, theoretically, subject to various errors and is not necessarily reliable. Whether the errors could be relevant in practice is a whole other matter. If the lathe and work holding device are in decent nick probably not for folk like us. Whatever its a total faff.

Adequate test bars aren't silly expensive and make this sort of thing easy. It is important to first verify that the lathe bed is in line with the spindle by traversing the saddle. If the bed is out of line you have problems.

Could run the indicator along the extended tailstock barrel. On a Myford it will probably not be dead nuts true but setting for the same taper readings as given by traversing the saddle will work well enough. Some creativity in mounting the indicator will be needed.

My opinion follows that of Big Den who taught me basic lathe work at RARDE and reckoned setting a topside parallel to teh bed was a "bloody stupid thing to do" as it unnecessarily multiplied the chances of error.

Clive

I leave the rotating bases on my pair of normal use vices. But I drive a Bridgeport so I've got more headroom than folk with smaller machines and the lost inch+ is no great issue.

Can't be bothered with keys and the like. Simply pulling the vice back so the bolts are both hard against the edge of the Tee slots before final tightening is repeatable to something between a quarter and half a thou per inch of jaw width. Good enough for ordinary jobs. Each holding down slot has its own designated set of Tee nut, bolt and washer which Intake great care not to interchange.

Way back I contemplated something a little more engineering like with Tee nuts in the vice slots engaging with special Tee nuts in the table slots to give flat surfaces for registration. Still wouldn't have been perfect so the effort didn't seem worthwhile.

If you drop the rotary base it would be sensible to cut the slot sides dead parallel to the jaws with the vice inverted and gripping a suitably aligned block on the lathe. Could simply pull back against the bolt, as I do, but a stepped Tee nut on top dropping down into the table slot a little might be worth the effort.

Jason has previously reported that he also uses the pull back against the bolts method with a plain base vice and has negligible alignment error. Tenths per inch at worst. Generally vice fixing slots aren't something where great efforts are made to accurately machine them.

Buy the very nature of manufacturing methods the sides will be close to parallel with the jaws but how close is matter of luck. I'd say better than 5 thou per inch of jaw width on a 4 inch vice can be expected but its not something specially checked by the maker so Jason got lucky.

A survey might be interesting. I'd put money on the simple pull back method errors for decent, but still affordable, vices clustering around the 2 to 3 thou per inch. The ground all over CNC specific and toolmakers vices being different issue by they generally don't have slots.

Clive

Ah! Baccy tins and Brylcreem jars.

Cue Mary Hopkins "Those were the days my friend....."

Seriously about 3 years ago I tripped over a website selling retail quantities of smart new tins in various sizes. Including baccy tins, possibly in all three sizes. Something of a surprise as I'd always thought such had to be got by the million, our thereabouts.

As I recall it the price for the common size was reasonably competitive if you bought a decent quantity. Probably equivalent to mid way between Raaco and the LiDL sets I bought earlier this year for a similar volume of storage. Being perennially short of sorted storage my interest was briefly perked but I didn't fancy the effort of building racks.

Regrettably I didn't note the website details but I imagine the firm are still around. Probably more than one business offering such things.

Clive

PS Bernard types faster!

Edited By Clive Foster on 11/03/2023 18:25:58