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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: Bridgeport Table Feed Drive Circuit
28/07/2012 10:02:13

Where can I get hold of the circuit diagrams for the Erskine power feed control unit commonly found on UK built Bridgeport series 1 milling machines. Its easy to find circuits the American controller units but not data on the Erskine one.

I'd also like the circuit for the change over relay unit needed to drive two axes from one controller. Its possible to work this out from the main wiring diagram but having the circuit makes for an easier life.

I've collected most of the bits to add a Y-axis power feed for mine but want to be sure I have away back if I make a mistake and let the magic smoke out!



Thread: Meddings Dril Tru
11/07/2012 15:29:18

A certain care is necessary with B16 chuck mount tapers. They come in two varieties, short and long, and are very close dimensionally to the Jacobs 33 taper. So much so that, depending on tolerances, it is possible to get wrong pairs to apparently assemble. Maybe even well enough to drill a few holes. This is most likely with no name or "sounds like a brand" bargain components.

I once had the dubious pleasure of sorting out a chuck and arbour pair where even the makers seemed confused as the measurements on both fell between all three standards. As the taper sides were barrelled rather than straight I eventually concluded that the (unknown) makers had concocted a sort of universal fit which would mate adequately with any provided sufficient pressure or large enough hammer were applied. Alignment afterwards being, most likely, somewhat imperfect.


Thread: Drilling out Grubscrews?
11/07/2012 15:09:39

A good quality brand new or carefully sharpened masonry is known to work well on hard steel given sufficient pressure at very low rotational speed. Drilling a bearing race in that manner was a known salesman / party trick with the old screw feed direct hand ratchet turned Coles and (presumably) similar agricultural drills. I doubt if any normal power drill will run slow enough or be able to apply sufficient pressure to reliably replicate the trick. I'm none too sure that a 6BA thread would stand the strain of that much pressure anyway.

If you have access to a good milling machine a centre cutting carbide end mill may well be a better bet than a carbide drill. I have successfully drilled out 2.5 mm taps using one. Last one of 5 killed one flute but it got the job done.


Thread: Making a thread end where I want it to
11/07/2012 10:53:51

If its a tapped hole you can, in principle do the job by tapping not quite deep enough, inserting the mating part and figuring out how many turns and / or part turns more you need to tap to get the right orientation. I suppose a similar tactic would work with a die. In practice probably a right faffle and odds of getting just right are slim.


Thread: Milling hine Speeds
27/05/2012 00:22:10

How difficult is it to change the belt on the motor to countershaft pulley drive? If things are reasonably accessible a quick and dirty expedient is to mount two sizes of pulley on both motor and countershaft chosen so the pairs give you appropriate high and low speed ranges. Get a two belts, one for each pulley pair, of lengths calculated to give very close centre distances. Generally a variation of less than 1/4" or so can be arranged. A reasonably hefty spring in the belt tensioning arrangement will accommodate that or you could go all posh with a spring loaded jockey pulley. If you decide to go for a jockey pulley it would be worth investigating whether light modification of a car fan or camshaft drive belt tensioner assembly could suffice saving on building work.

Although it sounds bodgey the two belt system worked well enough for me in one application for several people to copy it. Second time round I did it properly and worked out a set of pulleys to do the job with a single size of belt. Even with computer assistance the gain was not, objectively, worth the headache.


Thread: Motor suitability?
25/05/2012 17:48:44

It will do just fine.

The sounds like Newman is a standard capacitor start single phase induction motor whilst the Crompton Parkinson one appears to have simple start & run windings with no capacitor to improve starting torque. Both types built in numbers beyond convenient counting for light machine duties. No difference in performance once up to speed. Capacitors used to be very expensive (relatively speaking) and less than reliable so simple start windings were often preferred to keep costs down unless the application really needed the extra starting torque given by a capacitor. Often just as economic to use a larger motor to get the starting oompf.

These days capacitors are relatively inexpensive and many low end modern motors use them to boost the performance of an "economy" design of starting winding.


Thread: Endmill vs. Slotdrill
23/05/2012 11:08:02

As John Stevenson says the first big distinction is between centre cutting and non-centre cutting which defines whether or not the cutter can plunge straight in like a drill. The second distinction is whether it will cut a slot true to width or not. A two flute slot drill will, a four flute end mill cuts oversize, a three flute centre cutting slot drill/end mill (as popularised by the Clarkson FC3 "throwaway" cutters) should cut to size and a five flute cutter might. Essentially cutting a slot true to size requires balanced cutting loads. Any unbalance causes the cutter to walk or oscillate from side to side during the process nibbling the slot wider. (Deep thinking about this will make your head hurt!)

Best answer with a machine like yours, which isn't really able to exploit the more sophisticated cutters where confusion really reigns, is to go all old fashioned and use two flute slot drills for slots and four flute end mills to cut along the sides of steps. Pay particular attention to the depth of cut both vertically and sideways when using end mills as small machines like yours aren't really stiff enough for book values on anything other than quite small cutters. As Ady1 says a two flute slot drill can be sharpened with unsophisticated equipment and will do end-mill duties just fine, albeit more slowly due to having fewer cutting edges and being a little less stiff. My view is "really sharp" beats "theoretically better" any day.

If bargain packs of three flute throwaways can be had its worth getting a holder, usually 6 mm or 1/4" diameter, as the attrition rate of small cutters can be high. Also worth picking up a high quality centre cutting carbide one (or two) should a bargain come your way. Reserve for get out of jail purposes like chomping out broken taps. Be lucky to manage more than a couple or three taps hence need for bargain price but when the alternative is starting over .....


Thread: Bridgeport siting
21/05/2012 11:10:55

I have my Bridgeport canter-wise across a corner with a secondary exit door specifically placed to allow long jobs to project outside. Sort of thing you can do when scratch building. I went for an angle closer to 30° than 45° as it seemed tome that it made more efficient use of space in my situation. Pillar drill, Pollard 15AY so quite big, sits alongside.

Disadvantage of the canter-wise across the corner position is that it effectively blocks off quite a lot of alongside the wall storage space as its so difficult to squeeze past the table without lots of cranking. I've used some of the space for "once in a blue moon" stuff but 20/20 hindsight says I should have built some cupboards on castors with floor guides for easy pull out. Building a bigger shop and carefully planning beforehand ensures you have plenty of room for the stuff you had then. Six years down the line it all looks a bit different! Workshop stuff makes rabbits look downright lazy.

I have seen a Bridgeport placed canter-wise but away from the corner which seemed to work better from the storage access point of view than hard into the corner. Memory says a pair of four drawer filing cabinets (with lift out trays) filling out the corner so to speak but I may be transferring my affection for filing cabinets as workshop storage onto something of similar size.


Thread: Unknown Chuck
03/05/2012 18:53:30

Looks to be an auto-reverse tapping head. Usually used on drills or milling machines. Assuming it is there will be somewhere to fit an anti-rotation stop bar. Holding device at the end should incorporate something to hold the square end of the tap and some sort of adjustable collet or chuck to grip the shank and ensure concentricity. My Pollard built ones have a simple hand operated chuck similar to those on an old fashioned hand powered drill.

In operation the tap will be driven via the reduction gearbox so long as downward pressure is applied keeping the internal clutch engaged. If pressure is released either directly via the drill feed lever or inadvertently by the tap pulling forward too fast drive is lost until the clutch is re-engaged by pushing down again. Upward pressure on the drill feed lever brings the reverse drive into play which spins the tap out at direct drive speed. Settings 1 to 4 are probably overload clutch settings limiting the drive torque so as not to snap taps but still be enough to make a thread. My well be a grub screw to lock the chosen setting or may need to push the knurled ring back up the shaft to clear a key before it will turn.

Archer is a common make of similar style but yours looks too short in the body to be one of theirs.


Thread: 4 Wire motor
25/04/2012 23:03:11

Sounds like you have a permanent capacitor run motor. Running hot under no load is pretty characteristic of the breed. Excellent at their design job but not a general purpose motor. Ages back I fitted one to a pillar drill which eventually fried itself mid-way through a long series (50??) of fairly small holes (3/16).

Post mortem research revealed that this type of motor are a sort of "synthetic 2 phase" machine despite the single phase supply and very efficient at their design speed, load and slip angle. Unfortunately any change in slip angle as when running off load or with more than the design load rapidly upsets the synthetic 2 phase business so motor efficiency drops signifcantly and things become hot'n bothered. Often fatally.

A major application for these machines is driving continous or near continously running fans. Once up to speed the load settles very close to the design rating so the motor is happy, running all the time the extra efficiency relative to a standard single phase motor means smaller electricity bills. No centrifugal switch simplfies the design too making for a cheaper motor.


Thread: Panels & badges
11/04/2012 22:26:21

Computer drawing or CAD program for the artwork, print out and laminate (cheapy machine from Lidl) does the deed for me. Gluing is hit'n miss. Itysy bitsy chrome screws backed up by the nuts for switches, knobs and whatever seems to work fine in my hands but nothing I've done has huge areas of exposed plain panel.

Have also had good results with printing onto sticky backed paper and spraying with several layers of PCB lacquer for protection after sticking to the panel. Fine for interior use, not sure that I'd trust it in a workshop environment tho'. PCB lacquer is safe over laser printing, some of the other varieties aren't. Never tried with ink-jet print. Finding the split lines so the backing can be got off exposing the stickum can be "frustrating", main reason I abandoned the technique.


Thread: CNC or Manual
05/04/2012 19:24:33

I'd convert it back to manual and sell the CNC parts as a conversion kit.

Given the number of Myfords around there will always be a demand for decent quality used parts so there will be no great problem in getting a reasonable price for the parts you have removed to go CNC. However prices for good Myford lathes are, relatively speaking, high on a per size basis compared to other machines so its unlikely you will get a premium for the CNC converted machine. Indeed you might get less as most Myford buyers won't actually be looking for a CNC machine, or even want one. That said a proven, ready to go, CNC conversion kit would be quite valuable to any Myford owner considering going CNC and weighing the options of buying another machine, doing a roll your own job or hunting around for a kit.


Thread: Shell CY2 oil for Centec Vertical head
26/03/2012 22:46:02

Sounds like Castrol Magna BD68 is a good candidate for the Centec head. It's an ISO 68 oil specified for nominal ambient temperature operation on bearings, plain or roller, and slideways. So it hangs around a bit better than a simple "oily oil"(!?) but will put up with gear tooth shearing loads which some of the pure slideway oils wont. I use it for all my slideway and heavy oil machine tool duties, eg feed screws. Squirt it on change gears and it strings most impressively but still wipes clean. Castrol Hyspin AWS 32, a hydraulic oil, does me fine for headstock bearings and other light oil duties. RS components stock both so its easy enough to get.


Thread: Cutting spring wire
25/02/2012 17:58:00

Good old fashioned pliers will handle such cuts using the "shearing" notch on the outside of the pivot area of the jaws. That's the sort of job it's there for. Wouldn't care to risk the sharp edge of the wire cutting sections inside the jaws however good the pliers, altho' I have seen it done. Unfortunately many of the modern, especially in the more affordable ranges, pliers lack the outside notch and some that do haven't the requisite clean faces and crisp edge. Even the excellent Eclipse made pair I keep for best has no notch. A combination fencing tool probably has the requisite cutter section but is about 30 years since I used one so memory may not be right.


Thread: Cobalt drill speed to remove broken tap
24/02/2012 19:23:40

A three flute carbide centre cutting endmill did the deed for me in a similar situation. Either M2 or M2.5 size and cutting dry in a Bridgeport varispeed running flat out. Somewhat below book speed, which is approximately supersonic, but it shifted 3 dead taps for me. Found the cutter on E-Bay, can't recall the brand but I think it began with N. Not a job I care to remember. Too many holes, hard spotted material, and rapidly blunting taps.


Thread: Grinding on the side of the wheel
15/01/2012 20:44:06
Further to the grinding of lathe tools using a cup wheel the instructions for the Boxford T&C grinder specifically call for the face of the cup wheel to be dressed at an angle between 5 & 15° so that all cutting is done with the outer corner. It doesn't take much wear of the corner before grinding efficiency and finish quality deteriorates.
A previous owner of my Clarkson kindly marked the 10° offset for dressing and and 90° to spindle for grinding positions on the table pivot which makes things very easy. Presenting the tool to the flat face of the cup wheel, as I mistakenly did on first trials, has depressingly poor results. In contrast the cup wheel on my standard bench grinder works quite well when the tool is presented to the dressed flat face.
I guess heavy grinding for rough shaping is less common these days. The thin cutting disks for angle grinders which provide a faster and less messy way.
10/01/2012 23:27:42

Major wheel damage or break up generally needs something to get stuck between the wheel and a stationary, solid, object. This is much more dangerous when working on the side of the wheel rather than in the approved manner.

When grinding on the front the working plane is a narrow cylinder so the wheel surface above and below object being ground is further away. Besides reducing the depth of cut when things get out of position, thus reducing the drawing into the jam forces, it also makes it more likely that any wheel damage will be a chunk taken out rather than a full blown break up. The break-up forces tend to be somewhat on a chord of the circle which, being a weaker orientation, is less likely to take the whole wheel out.
On the side of the wheel the working plane is flat so, should something shift and start to jam up there is depth of cut reduction geometry to offset the draw in tendency. Rather the opposite. As the offending object is drawn the depth of cut increases adding to the draw in effect. The forces on the wheel are across a flat side so its much less likely that a chunk can be knocked out relieving the forces before they get too large. Instead positive feedback is likely to continue until either the motor stalls or a serious crack develops across the flat side leading to wheel explosion. For various reasons such a crack is likely to be more or less on a radius, clearly the most dangerous orientation.
Another factor working against grinding on the side of the wheel is the difficulty of dressing. If its dressed at all. So the wheel will most likely be at least somewhat glazed and won't be working anywhere near its best. Its tempting to up the pressure on a wheel that isn't cutting well.
As has been said grinding on the side of the wheel is pretty similar to using a cup wheel. So ideally the wheel should be dressed with a slight inwards taper, 5 to 10°, so that only the outer edge is doing any work. Tool and cutter grinder users will know that this shape makes a big difference to how easily and accurately a tool can be ground to a good finish. It also makes using the common swing across the wheel drill sharpener a lot less finicky.

Thread: T nuts
07/01/2012 23:17:19
Don't care much for DIY store threaded rod. Generally a very slack fit in tapped holes.
Much to be said for using light alloy for Tee nuts. If you do trap a bit of swarf it grinds into the nut where you can get at it for removal rather than sticking into the underside of the Tee slot from whence it takes serious creativity and numerous words of power to dig out. Also if you do get over ambitious with the spanners the nut will strip before the table is damaged.
MDF / Chipboard / other improved wood sheets as used on kitchen cabinets and flat pack furniture makes excellent work holding plates if you don't have a vice or the job won't fit. Just break out the power driver and DIY screw box. Either fit holes in "spare" parts of the stock or use whatever is handy for clamp bars. Handy on the drill press too. Given the intended application the stuff is silly flat, although its best to check with a straight edge as sometimes there are ripples. Totally disposable once there are too many holes or milled out bits to keep using as there is always some-one nearby doing a kitchen. Easy enough to get as much as you need. Might have to donate an hour or two of help tho'. (Don't underestimate the strength of such cabinets. Well up to workshop tasks with a bit of re-engineering such as proper solid backs and screwed on angle strips for positive fixing of shelves etc.)
Thread: Angle Grinder Cut Off Saw Attachments any good?
05/01/2012 23:33:21

Apart from their habit of spraying hot stuff all over the shop unless you get creative with better guarding the big problem with these things is the price performance ratio doesn't work. Keeping the cost down low enough to create a decent market means the overall engineering has to be too cheap to work well. A major problem is that they have to be made to fit "any" grinder rather than specific models with the inevitable problems of flimsy multi-adjustment and nearly fits but manages to hold (sort of) rather than fits properly.


I picked up one from Lidl a while back for a specific job but a bit of fiddling showed that I was never going to be happy with the standard grinder mounts. Re-engineering looked to be relatively simple but more trouble than its was ever going to be worth.For general use a 9" grinder on a pivoting arm and a decent milling vice fixed to a suitable base plate looks a better option. At least the capacity will be half decent. I guess the standard size would be OK if you only do small work but DIY is still the way to go. After all neither vice nor grinder need be dedicated. Small size would be great for rough shaping HSS bits with an appropriate holder.
The 1 mm disks are ace.

Edited By Clive Foster on 05/01/2012 23:34:12

Thread: Blackgates power hacksaw drawings
22/12/2011 21:52:56
If you have a source of decent hex steel bar it's well worth considering copying the Kennedy saw guide bar arrangements. Not too difficult to make, easily adjusted and very effective. Had one in the lab support workshop at my old employers which saw much use. Overall design lends itself to home shop simplification with a flat base plate, commercial work vice and simple plummer block bearings on posts. Simple flat pulleys too. A multigroove belt would work just fine.
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