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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: Do I need a J drill or what?
24/06/2023 16:13:49

Tony

I've always found Delrin drills true and to size given a razor sharp drill with undamaged lands. Dormer factory grind is barely sharp enough.

Fortunately my Clarkson attachment will put that extra edge on .

Hafta say that if I needed job to come dead right first time I'd factor anew drill into the budget. If I did lots of plastic work there would be dedicated drills, just as there would be if I did lots of brass.

Nylon of course is different story. Given a sniff of a chance that runs away rather than cut.

Clive

24/06/2023 13:44:23

Getting back to the machining side of things Delrin is generally very stable when machined but it is a plastic and so thermal conductivity is inherently low.

Standard machining rules apply. Razor sharp tools, low speed, heavy cut, decent feed and keep it cool. Heat input is fundamentally related to length of cut so you want as much material out as possible per unit length.

Never had much luck with stepping out, shaving cuts or reamers. Drilling straight to size, unless teh hole is really big, always worked for me. But I do have the means to make any drill up to 3/4" very sharp indeed.

Clive

Thread: Have I made a mistake buying a MT3 mill?
23/06/2023 16:37:11

its remarkably difficult to get authoritative information as to appropriate drawbar torque for draw in collets.

If you search hard enough you will find that Bridgeport advise between 25 and 30 ft lb for the R8 system, which doesn't seem unreasonable. I have, I think, 8 versions of the Bridgeport manual and only one gives a figure, in a rather hidden place too.

ER system torques are relatively findable. In the context of Model Engineer / Home Workshop machines the official torques to guarantee run-out specifications are scary high. Fortunately too much for the usually supplied sheet metal spanner to comfortably reach as the usual spindle lock components really aren't designed for the stresses of an ER25 or 35 system at full torque.

Essentially the requirement for safe cutter holding is to generate hoop stresses in the collet gripping the cutter equivalent to a moderate interference fit. Heat shrinking of cutters into their holders is popular in the CNC world. They temperatures involved suggest the holder contraction is moderate so presumably the forces involved can be calculated.

Because MT tapers are both relatively long and shallow enough to be self holding it can be presumed that the frictional forces between collet and spindle go up very rapidly once contact between collet and cutter has occurred. So the conversion of longitudinal draw force into interference fit equivalent hoop stress in the collet will be inefficient. I suspect that further tightening of the drawbar beyond a fairly moderate torque does just about nothing to increase cutter retention but massively increases the hold between spindle and collet.

In principle all this stuff can be fairly simply, albeit tediously, calculated to a precision adequate for workshop use and verified by comparison with what real world figures can be found for other systems. But its seriously annoying that there are no proper engineering figures out there.

Were I to use an MT3 collet system I'd promptly grind a decent section out of the middle of the MT3 section so only a short part at the front is actually compressed to grip the cutter. Something equivalent to the working section of an R8 should be ample. A fairly short section at the drawbar end should stabilise things OK so the collet actually pulls up straight. R8 has a simple cylinder at the drawbar end but trying to replicate that is way too much bother.

Out in the real world MT shanks with the centre third or more reduced so as to be clear of the spindle walls are not uncommon so clearly the full shank has way more grip than needed for many jobs.

As cutters with flats for sidelock "Weldon" holders are now fairly readily available at affordable prices it's worth considering whether using sidelock holders rather than collets makes economic sense. You don't need many sizes and being able to leave cutters in their holders ready to go has certain advantages.

Much more so nowadays when it's affordable to have a DRO system on the Z axis. Were I starting over and sidelock holders about 1/2 to 2/3rds current prices from the usual ME budget friendly suppliers going all in on sidelock with enough of each size to work in a manner akin to using a QC system on a lathe would be a no brainer.

Given that gripping area of an MT shank in the spindle is hugely greater than that of a collet on a cutter I imagine very modest drawbar torque would suffice to secure the holder against rotation.

Clive

Edited By Clive Foster on 23/06/2023 16:39:55

Thread: Eclipse mag stand part
22/06/2023 14:31:23

Don't know what the factory issue is on that particular indicator but it would be relatively easy to fabricate a version of the common cross drilled cylindrical head bolt and sleeve system used to hold round shaft mounts and adapters. It's common for indicators to either have a built on round shaft or some sort of adapter fitting either a lug on the body or slender Vee grooves on the body. Common shaft sizes are 1/4" and 6 mm Ø.

Unfortunately I don't have a piclture to hand of the common system based on a bolt with a cylindrical head cross drilled to accept whatever size shaft the system is built for. A closed end sleeve drilled the same size is a loose sliding fit on the cylindrical head with the drillings offset sufficiently that when the bolt is tightened the holes no longer align. Clearly if a round shot is passed through the holes in both sleeve and bolt head things will be locked in position when tightened up. Generally a round, knurled, nut is considered sufficient. The closed end of the sleeve provides something to tighten against and prevents the sleeve from falling off when no shaft is fitted.

The closed end is commonly made conical (ish) with a matching recess in the base end but flat works fine.

Clive

Jason is probably right as to the factory intentions as what he describes works in exactly the same way. Easy to check. Just screw down further and see if the end of the thread appears in the cross hole. Not one I've seen.

 

Edited By Clive Foster on 22/06/2023 14:34:56

Thread: High Speed Milling
22/06/2023 09:25:57

Ian

I think you were doing well to hand feed such small high speed cutters at all on an ordinary mill of that size. Hand feeding is a right pain even on something designed for that sot of thing such as a BCA.

Possibly the worst issue is having no feedback at all from the cutter. You are always working against the inherent drag of the slides which is never exactly constant so its incredibly difficult to keep the feed truly even,

Best bet would be to arrange some sort of power feed. Wouldn't need to be terribly sophisticated. Simple belt drive to a pulley from some sort of variable speed motor.

I'd be looking at cannibalising an older two speed battery operated drill being disposed of because the batteries are kaput and new ones either un-obtainium or way too expensive. Cheap DC power supply off E-Bay or whatever will run it just fine. OK the durability of a drill motor isn't going to be up to what we consider machine tool standards but it should last a useful time and the supply is more than ample.

I'm sure I've seen "look what I made" pictures of such on the internet, maybe even a how to article.

Clive

Thread: Which cutting lubricant
18/06/2023 22:32:13

Using neat cutting oil is very wasteful.

Only a very tiny amount of oil is needed to lubricate the tool tip and work so the cut proceeds easily with the chip running smoothly over the tool. Check out the consumption of pure oil microcode systems for confirmation.

Conventional suds emulsion used in flooded applications is largely about cooling which is mostly done by the water content. Compared to water oil is pretty pants at taking heat away, especially at the low temperatures typical of the light cuts inescapable with smaller machines.

Synthetic oils have better extreme pressure lubrication properties than conventional cutting oils so higher dilutions can be used. Its probably true to say that for folk like us the mostly water content is primarily there to give the spray or brush something to get hold of.

I find the only exception to diluted Ultra-Cut is for single pass threading as with a die, whether conventional or coventry, which needs the heavy duty lubricants specially designed for the job.

Clive

Thread: Hoppers 4 way toolpost thread ??
17/06/2023 21:48:40

IanT

I think we are at cross purposes.

I think I'm advocating exactly the same things as you.

Viz

If tool tip height in interchangeable blocks can be accurately and easily set off the machine the sole compelling advantage of the conventional QC systems is the screw adjustment system that makes it relatively easy to set tool tip height on the machine. There is no inherent reason why arranging quick change blocks should be any harder than changing tool holders on a conventional QC system. Whether by your rose blocks, my proposed rotating tool stud or any number of other mechanically satisfactory solutions.

Interchangeable blocks do require an indexing base whilst conventional QC posts can get along without indexing. But plenty of folk regularly shift Dickson and similar 2 or 3 station posts around to different angles without the aid of indexing and the Mulitfix goes to considerable extra engineering effort to include multiple angular settings. It was quite common for industrial users to graft a Dickson onto the indexing arrangement living under the factory 4 way of many makes.

I can't see the extra cost of an indexing base being a significant deterrent.

derek hall 1

The piston post is not inherently better than the Dickson system. Arguably its worse because forces are mostly resolved via the holding piston rather than directly.

In my experience the weak point of a Dickson is that it needs regular cleaning out inside. Mine are positive magnets for itty bitty teeny weeny swarf dust. But it's easy to pop the pistons out and clean. Height retention failures are primarily due to the snail on the locking hex self adjusting the height setting thimble. The lock bolt needs to be tight and the tool holders held in position whilst being locked. Leaving it up to the locking tongue to pull things into position is poor practice. The holder is almost invariably at an angle so the snail rubs against the thimble making upsets more likely. Hamfisted folk can also bend the stud. Which is less than helpful. A quick brush down of the mating surfaces to remove any swarf before fitting is sensible.

Clive

Thread: Bridgeport Milling Machine feed control module
17/06/2023 16:49:22

Leon

PM sent re data.

Agree with Andrew that problem could well be motor commutator dirty and / or worn out brushes. If you do decide to investigate inside be prepared for copious quantities of finely divided carbon dust. Judging by the quantity inside the one on mine I'd be unsurprised to discover that it had worn out two sets of brushes without intermediate cleaning!

Do wear disposable gloves because the dust is so fine it's near impossible to get your hands completely clean. Even after three or four goes. The mess in the sink will not improve popularity with the distaff side either. You also won't be impressed next time you have to clean out the U bend. I know significant amounts hang in there for 3 years!

Tip :- decent brand hair shampoo is much better than Swarfega and the other mechanics hand cleaners for shifting this sort of thing.

Clive

Thread: Hoppers 4 way toolpost thread ??
17/06/2023 16:14:39
Posted by Nick Wheeler on 17/06/2023 15:52:35:

Posted by Clive Foster on 17/06/2023 14:31:23:

If you use insert tooling, with its fixed cutting tip height, purchasing a conventional QC system means you are paying lots of money for a versatile height adjustment capability that you will never use.

Surely the height adjustable feature of QCTPs is a useful freebie from how the holders drop into place? If it was the most desirable part, wouldn't they have been call Height Adjustable Tool Posts?

I consider the QCTP to be the best value tool I've bought for machine tools.

Height adjustment is hardly a freebie.

It's what defines the conventional QC system. If (relatively) easy on-machine height adjustment wasn't considered essential folk would be just swopping blocks and paying shedloads less money for the system.

Bargain hunting means I probably only have £500 or so locked up in the two T2 Dickson / Rapide posts and 20 (ish) holders I have for my two machines. Useful but not, in my eyes, exceptional value. At full price unthinkable!

Clive

17/06/2023 14:31:23

Always wondered how the whole QCTP thing got started. It's an inevitably expensive concept due to needing decent engineering and precise manufacture if it is to work well for a useful lifetime. Not to mention system lock in. Of necessity the tool must overhang the support so it's inherently less rigid than simple block sitting down onto the slide.

From a clean sheet of paper perspective it would seem much more economic to make simple slotted block tool posts held down to an indexing base by some form quick acting lock. Either 1/3rd (ish) turn like most QC systems or some sort of lift over latch. Indeed Holbrook at one time made a 4 way system with a horizontally pivoted spade grip handle that was pulled down to latch it onto the face ratchet indexer after turning. Half way to an easy remove system but Holbrook used the usual nut on a stud to hold things together.

Fixed block tool posts were widely used and most industrial English lathes had a well engineered indexing device under the factory four way posts so adding quick release set-up to the block doesn't seem much of a stretch. Given quick release capabilities tool height can be set by direct measurement on the bench so the most objectionable trial and error aspect of on machine shimming is avoided. A simple block with slot(s) must surely be much less costly to make than a QC toolholder.

Maybe 20 years ago I drew out a Model Engineer / Home Workshop friendly version of this concept using two way blocks built up from stock bar and plate sections glued and screwed together. The blocks were to be held down via a hollow castellated nut screwed into the top passing over a rotating tool post stud cross drilled to take a tommy bar sized to engage between the castellations. A partial turn of the tommy bar from tight would allow it to be withdrawn so the block could be lifted off and a different one fitted whereupon the tommy bar could be replaced and things locked with a partial turn.

Some years later Neil was kind enough to publish in the Letters section of MEW a layout sketch of the system as it would have been applied to the SouthBend Heavy 10 I was using at the time of design. Taking the opportunity to step up from the Heavy 10 to a Smart & Brown 1024 complete with a Dickson set up curtailed development. I was never really happy with the indexing on that specific concept but I know how to do it better now.

If you use insert tooling, with its fixed cutting tip height, purchasing a conventional QC system means you are paying lots of money for a versatile height adjustment capability that you will never use.

Clive

Thread: Which cutting lubricant
17/06/2023 08:42:07

Which Rocol are you using?

Neat or diluted?

Key to economy is to choose something that keeps and can be used at high dilution.

Almost 20 years ago I took a deep breath and paid around £40 for 5 litres of Ultra-cut. Using it at approx 40 to 1 dilution I'm about half way down the bottle now. Big hit was filling the lube pan on the S&B 1024. Being synthetic it doesn't smell or go off.

Worst aspect of high dilution is needing to wipe things down at close of play followed by anointing with way oil or similar to protect machined surfaces. I think it good practice to work a bit of lube under the lathe saddle et al before lights out. Synthetic is better than suds when its comes to corrosion but it can still trap water underneath. I imagine high dilution gives better wipe off too.

These days I tend to use Bjur Spray mist devices, modified to work like micro-drop systems rather than spray to avoid fug, on the lathes and mill. Being very careful where I point the nozzle, more like running air blast cooling really. squirt bottle on drill, saw and shaper. 500 cc ex LiDL bathroom cleaner squirt bottle lasts around 6 months between re-fills. Choose a squirt bottle made for something aggressive as the stuff can eat the squirter innards.

Clive

Edited By Clive Foster on 17/06/2023 08:42:25

Thread: Unknown Engine needs new spark plug
16/06/2023 23:23:03

+1 for NSU Quickly.

Newnes says:-

Bosch W240T11 plug, breaker gap 12 thou, timing 24° btdc,

Carburettor Bing 1/9/1, main jet 56, needle position 2.

Shedloads of information on the internet.

Clive

Edited By Clive Foster on 16/06/2023 23:24:15

16/06/2023 20:57:37

The make of the carburettor, and number if visible, might at least help identify the country of origin.

If the engine was built between around 1950 and 1965(?) Newnes Motorcycle Data Book may help as this gives basic specification and service data for most of the motorcycles, scooters, mopeds and light cars sold in theUK over that period. Including carburettor make and number.

My copy is of the second edition which only goes up to 1961, I think there was third edition with a later cut-off date. It's fairly comprehensive, covering some makes I've never seen or heard of elsewhere.

Clive

Thread: Making a large washer.
13/06/2023 09:26:24

Circlip

The tank cutter tool is basically a trepanning cutter for making holes in well supported sheet metal. Not so good with two concentric holes.

I have one and it hates me!

We have agreed that if I leave it resting in the drawer it won't take bite out of me letting the red stuff out!

Clive

Edited By Clive Foster on 13/06/2023 09:27:30

Thread: Suitable Vice and decent milling cutters
11/06/2023 21:45:25

Jason

Thanks for pointing out the extra capacity obtained by reconfiguring the jaw plates on the Arc Versatile vices. Something I always forget about.

Mostly because I've been driving a Bridgeport for the last 20 odd years so the shallow gripping surfaces after re-configuration appear woefully inadequate when you have a 2 hp motor driving things. Totally lost touch with how the definition of adequate differs for smaller machines!

Is this just an Arc feature or do some other breeds both have it and are made with sufficiently good quality control for it to be safe to use. The flatness and anti-lift demands on the moving jaw would seem to be quite stringent when the jaw plate is fitted at the handle end.

My precision vices generally get used sat on their sides.

Clive

11/06/2023 17:33:10

Mouse

It's a truism that model engineer and home shop machinery is frequently required to handle jobs that objectively are too large for the machine. Something that needs to be born in mind when selecting work holding and tooling. Most important when considering a milling machine because everything goes inside the work envelope

Before finally purchasing tooling and work holding for your mill it's worth doing some drawings to see how much space the various options leave you. Many folk buy a vice with a rotating base and habitually leave the rotary base off to get an inch or so extra clearance under the head.

For example by small machine standards a 1/2" or 12.5 mm drill and chuck is a very long assembly hanging below the head. Its a right pain if you have to pull everything off, remove the base from the vice and put it all back to get that 1/4'' or 6 mm clearance the drill needs to get into the right position. All users of small machines doing small jobs should seriously consider investing in sub drills. Seem excessive to pay for 4", 100 mm, of drilling depth capability when your thickest job is only ever going to be 1/2", 12.5 mm. Endless other examples in the same vein.

Vertical clearance is the obvious one but side and longitudinal clearance can also be important.

Looking at the ArcEurotrade website **LINK**

https://www.arceurotrade.co.uk/Catalogue/Workholding/Machine-Vices

The two, readily available new, vice styles of interest for general use are the ordinary screw operated ones and what Arc call the precision vice type 2.

The screw operated ones have less opening for any given jaw width and body size than the precision ones because the moving jaw base needs to be quite long for accurate movement and stability.

The precision type is tightened by an angled socket head screw pulling the moving jaw forwards and downwards making it very stable at the cost of limited travel. So the nut underneath has to be arranges so it can take up a number of positions giving coarse adjustment. Which is not only less convenient than a single long screw but also frustrating when you set them coarse position wrong and have to move the nut before the vice will tighten up.

The precision vices are expensive due to being well made and ground all over so they can be used turned on their side if need be. Affordability is a relatively recent thing. Back in the day such were purely industrial market devices and priced accordingly as the modular vices originally designed for CNC work still are. Although import prices are creeping down into merely painful territory.

The shallowest, relatively findable, type of vice is the industrial style originally introduced by Taylor having a free sliding moveable jaw clamped by a screw in a sort of Y shaped assembly engaging with rack teeth on the top of the vice base. Strong and durable but now seriously obsolete for industrial use they often appear on E-Bay, Facebook et al for reasonable money. The primary installation disadvantage being jaws much narrower than the base.

As ever it's a matter of making a, hopefully informed, decision to pick the best compromise of advantages and disadvantage that can reasonably be afforded. Many folk have found that a smaller, more affordable vice, supplemented by clamps and sacrificial plates to hold oversize work directly on the mill table to be an effective compromise. Disciplined use of the travel stops being important to preserve the table top surface.

The two piece endless vices, whether bought or shop made, can be an effective way of holding oversize jobs too. Tend to be too expensive or need too much work to make unless you really need them tho'.

Clive

Edited By Clive Foster on 11/06/2023 17:43:04

Thread: Making a large washer.
09/06/2023 21:19:56

Effective though trepanning is grinding the tools can be tricky if you've not done it before and don't have a good guide with decent pictures. As ever it gets easier the larger the job is. Grinding a satisfactory tool to handle holes under 400 mm, 1 1/2 inches or so without putting excessive force into the sheet can be quite difficult.

It's important to fix the sheet securely to the substrate as there is significant force trying to make things ripple. Worse with thin material.

I can, and have, both ground the tool and done the deed successfully but I'd rather not. During my efforts I didn't have that nice warm fuzzy feeling of proper understanding with everything under full control.

Clive

09/06/2023 18:34:18

Having an objectively excessive collection of Starrett hole saws I can generally find one quite close to the needed inside and outside sizes which minimises the amount of lathe work involved.

A certain care is needed when doing the lathe work to stop the nascent washer from twisting out of position in the chuck leading, at best, to misshapen inside and outside diameters. At worst the thing pretzelllises before self ejecting from the chuck.

Which is annoying.

The grooves in the jaws aren't guaranteed top hold the thin part in a secure and stable manner. The job is most at risk when taking the corners off the outside. The more sides you cut initially the lower the knock-knock-knock forces at each corner making it much easier for the chuck to hold properly. Clive Brown advises starting with an octagon rather than square which is what I used to do before getting into hole saw collecting.

Trapping a piece of suitably thick wood, MDF, particle board or similar between the embryo washer and the chuck jaws to act as a sacrificial support can help. No need to make it tight on the centre or terribly round. It just needs to sit under where the tool is cutting.

As with so many such jobs belt and braces set-up is frequently not needed. The job going fine when just held in the chuck. But taking that extra care costs little time when "thats the way you do it".

Clive

Thread: Bench Grinder Bush
05/06/2023 17:29:42

Further to what Clive Brown says about gripping diameters the proper gripping rim width is pretty narrow.

Maybe 1/4" or so.

Some of the economy range grinders have very poorly designed flanges with drastically excessive gripping flange widths. The simple pressed ones can be horribly bad in that respect. Often seriously less than flat too.

I have a bar of dreadful, almost too soft to turn, aluminium that is steadily being used up for wheel flanges and the like. I figure a nice soft surface on the gripping bit is a good thing. Besides I have to do something with the stuff even if it owes me nothing having been given to me by a pal notorious for not letting anything go for free. Wonder why it escaped!

Clive

Thread: How did early Automatic gear boxes on cars work?
05/06/2023 17:18:25

John

Torque converters aren't actually as inherently inefficient as commonly thought. Under steady state conditions they approach that of fluid couplings which rarely have worse than 4% losses and can get close to 2% loss if properly specified and fully filled. The extra losses of a torque converter are primarily due to less efficient flow around the stator that generates the torque multiplication when needed. Under steady state conditions at whatever speed the stator is optimised for you can get down to significantly less than10 % losses. But it's generally impractical to operate a car at optimised steady state speed and load. In acceleration mode losses can be much higher due to flow inefficiencies.

If torque converters were as inherently inefficient as raw fuel consumption comparison suggests the losses would rapidly boil the transmission fluid. Assuming you need 40 hp to run at 70 mph and that raw fuel consumption comparison suggests 25% losses you'd be pushing something like 10 hp worth of heat into the transmission fluid. Basically a 7.5 kW mechanical heater. The itty bitty transmission oil cooler radiator fitted to most cars isn't going to cope with that.

For a conventional carburettor or older, more basic, fuel injection systems the tree steady state, cruise, problem is that the torque multiplication in the converter lets the engine run at a much less efficient throttle setting. Basically there is a throttle opening corresponding to peak torque at any engine speed. This engine speed is the most efficient, lowest fuel consumption, one for that throttle opening. Sympathetic drivers can generally run their cars quite close to peak torque at most speeds getting best economy.

(Side comment. Really sympathetic drivers of a manual gearbox car with a properly set-up SU carb will know that once up to speed on motorway the throttle can be backed off to not much above idle and the car will maintain speed on much less fuel. The best speed for this effect depends on the car. For the old 2 litre Montego estate with manual box it was just over 70 mph with a couple or three mph range each side needing only tiny throttle tweaks to hold. 50 mpg being insane for those days from a car that size, well loaded too.)

Put a torque converter in the driveline and the torque multiplication lets the engine run well away from peak torque whilst still generating the power needed to drive the car. Engine efficiency plummets and fuel consumption rises the further away from peak torque you are able to run. It doesn't help that the inherent losses of a torque converter are roughly correlated with the amount of torque multiplication going on. So whilst driving the car with the engine running significantly away from its most efficient throttle position the torque converter is also running at a less efficient power transmission mode.

Loose - loose.

Modern electronically controlled, mapped, engine and transmission ECU systems seek to keep both the engine and torque converter away from the inefficient modes during normal operation. Adding more ratios to the gearbox significantly helps because the speed range demands on both is greatly reduced so much better optimisation is possible. Such controls also allow much greater use of the lock up clutch which is a great aid to economy.

Clive

Edited By Clive Foster on 05/06/2023 17:40:16

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