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Member postings for mgnbuk

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

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Thread: Power drawbar
19/12/2011 20:15:11
I have not seen a power drawbar used on a morse taper. I supsect that the force required to break such taper would be large - even the normal steep taper tooling can stick if the tool gets hot in use - some drawbars are designed to contact the head of the pullstud in the last millimeter or so of travel to break the taper free, particularly on toolchanger machines where a stuck tool can damage the mechanism.
 
I have designed replacement spindles incorporating screw type & collet type drawbars. The collet clamping element & cylinder were bought in from a German company - Berg Spanntechnik. The datasheet for the clamping element is here :
 
http://www.berg-spanntechnik.de/wEnglish/produkte/werkzeug/pdf/ssk.pdf
 
This gives details of the spindle internal features required to make it work. We used them with hydraulic clamping cylinders, not Belleville spring packets. More reliable clamping & almost impossible to pull a tool out, as the cylinder features non-return valves that generate a hydraulic lock when clamped. Not cheap. though - IIRC a 50 taper cylinder (3.5T pull) was around £3500 10 years ago. The collet was around £200
 
For the screw type units we used Align Air-power units (same company that makes the add-on power feeds), usually bought from XYZ Machine Tools. Drawback to these is the need for a spindle brake, as the spindle spins when the tool touches the taper otherwise. The tool also has to be guided into the spindle as the drawbar rotates, there is a risk of cross threading & the threads must be kept free from debris & well lubricated (molybdenum grease) or they can seize.
 
During rebuilds of CNC machines we frequently found broken Belleville springs on machines equipped with them.. To get the required pull strength and travel can make for quite lengthy stacks (longer spindles). The stack needs supporting to keep the spindle balanced. Many release cylinders put the release pressure through the spindle bearings (not good), though it is not difficult to design an arrangement that doesn't.
If using air to release the tool, many machines require tandem cylinders to get sufficient thrust. Assembling the things can be a bit fraught, as the stack has to be pressurised in order to screw the clamping element into the release shaft.
 
Another variation uses ball bearings to clamp the pullstud instead of a collet - a sleeve with 4 holes drilled "not-quite-through" holds the balls captive in the spindle. An groove in the spindle allows the balls to move away from the pullstud when the sleeve is moved to release the tool & the pullstud is released. When the sleeve moves to clamp the tool, the balls move out when they contact the end of the groove & catch under the pullstud head. A Wadkin vertical machining centre where I did my apprenticeship had this arrangement - one operation on stainless ball valve bodies was a back counterbore & a tough casting (or operator on bonus with the feed override on 150% !) could pull the tool out of the spindle. And the ball bearings with it. . Apprentice maintence person (me) would have to lie under the spindle wearing goggles & attempt to replace the balls in the sleeve with a long screwdriver & a dollop of grease. I don't know if the sleeve was drilled through (which allowed the balls to escape) of it pulling the tool out had opened the holes out. A hydraulic clamp cylinder would not have allowed it to pull out in the first place !
 
If I were designing a compact system "from scratch" I would investigate internal clamping - as used on modern high speed machines (HSK, Sandvik Coromant Capto or Kennamental KM) like this :
 
http://www.berg-spanntechnik.de/wEnglish/produkte/werkzeug/hsk_auswahl.shtml
 
A much stiffer system, as the flange on the front of the tool is pulled in to contact with the spindle face as well as the taper . The industrial products detailed are tri-lobed designs (The Sandvik system requires a licence to incorporate it, not sure about KM, but I think HSK is "open source"). A low power system for home use & manufacture would probably work fine with a straight cone.
 
HTH
 
Nigel B.
Thread: Is 0.1 deg good enough..
19/12/2011 13:32:38
So does the accumulated wisdom here think that leveling to 0.1 deg is 'good enough'?
 
Not by a long way, if you want to do the job properly. A precision level with 0.05mm/Metre sensitivity or better - at my previous employment we had a 0.02mm/Metre block level as well as 0.05 box levels - & aim for 1/2 a division error or better. I was able to "borrow" overnight the 0.02 level to install my Myford & it levelled to within the width of a graduation line in both planes - near enough !. When checked again a couple of years afterwards there had been very little movement & only minor adjustments were required.
 
the absolute dead level is not necessary.
 
It is if you want to check alignment to British or other National Standards. The first check on all those I have worked with is to check absolute level in both planes & there is a (tight) tolerance specified. Some machines (slant bed lathes for example) require a levelling fixture to hold the level, due to lack of suitable features on the bed. One of the "challenges" of installing machines & demonstrating the alignments is that you are very limited in what you can tweak - due in part to the levels being "tied up". It was frequently necessary to push one check (say, levels)to one side of the tolerance band in order to get another check (say, squareness) to come in on the other side. Small adjustments & frequent re-checking of all the values being the order of the day.
 
Regards,
 
Nigel B.
Thread: 3 phase motor connections
16/12/2011 16:11:26
motor was started as ‘Star’. After the starting surge died down and the motor came upto speed; the ‘Memota’ type unit automatically switched the wiring into Delta. Star takes a lot of current and spins the motor up to speed changing it into Delta reduces the current flow and the motor then cruises doing its work.
 
I think you will find that it's the other way round - star connection takes less current. That is the whole reason for star-delta starting - to reduce the initial current draw. It also starts the motor with reduced torque, giving the device being started an easier time. It is not usual to star-delta start small motors - I can't recall seeing a motor under 7.5hp started in this way.
 
It is usual these days to use an electronic "soft start", as these give more control, include current limiting functions & the price is not usually much different to a star/delta starter + oveload.
 
Regards,
 
Nigel B.
14/12/2011 20:37:39
There will be four terminals
 
Definately only 3 on my motor - had to brave the cold to go out to the garage for something else & checked. 3 black wires to studs on a paxolin plate. That said, the rating plate unambiguously states 415v only, with no mention of 240v operation. I would guess that my machine is '60s built - blue/grey paint and old-style name plates - later machine probably had different motors.
 
Nigel B.
14/12/2011 19:06:02
I seem to recall that the 3 phase motor on my Boxford shaper was 415V star connection only. I swapped it out for a second hand single phase motor to get the machine operational quickly for least cost.
 
The rating plate could be a "generic" one - are there any current values stamped in the "Mesh" area of the plate ? Current at the lower voltage should be higher. If there is only one current value & un-stamped areas on the plate, I would suspect that the motor is single voltage star wound. Only 3 connections (or 3 wires from the stator) in the terminal box would confirm this.
 
You can get 240V input / 415V output inverters, though I don't know how happy they would be starting a shaper and they are not cheap You may have to go oversize with the inverter to handle the starting load.
 
You may be able to dig into the motor to retreive the star point & attach 3 more wires - though there is a risk that you will break a wire off & the motor would then require a rewind (or replacement). Been there, done that, payed for the rewind ! (on a different motor, though).
 
My single phase shaper is rather rough running, as single phase motors are not as smooth as 3 phase - the cabinet doors buzz quite annoyingly when the motor is running. Having recently "invested" in a Clarke static converter, I may put the 3 phase motor back on and trying the converter on it.
 
Regards,
 
Nigel B.
Thread: Fitting Power Feed to Chester Super Lux Mill
08/12/2011 20:51:11
Have a look here :
 
http://www.use-enco.com/Machinery/205-6404.pdf
 
for the Enco version manual, which appears to be largely the same as the Align unit fitted to my RF30 mill/drill .
 
HTH,
 
Nigel B.
Thread: MEW, would less be more?
07/12/2011 20:06:11
it doesn't really matter if you don't understand the attitude so lolng as you buy the mag.

Ah, but I don't any more. I think Issue 184 was my last, having subscribed since around Issue 8. Finally got unhappy enough with 13 shallow issues a year to ring up & cancel the DD.

if you are going to moan about magazine content send it to the Editor
 
Tried that - not going to change anything any time soon, I think. Hence my decision to drop out.

If everyone thought that, there would be no magazine. If you think it could be better, help make it so.
 
I reiterate - this is a commercial venture, not a club magazine. While the motorcycle magazine I subscribe to has submissions from readers, the content it is primary written by the magazine staff. This no longer appears to happen with MEW, probably due to the current Editor also being responsible for ME as well. Which brings us back to the original question posed at the head of this discussion....
 
I have, in the past, edited & layed out a national motorcycle club magazine (1200 or so members), so I can sympathise with DC1 & realise that you cannot please all of the readers all of the time. A club magazine is reliant mainly on submissions from members to fill it (and 64 pages in A5 format, bi-monthly take some filling - very few adverts !).
 
But when short of articles, or when the balance appeared a bit one-sided for the next issue, I sat down & wrote something. Or perused my photo collection for something a bit different. Or set out & took suitable pictures of my bikes or events - anything to fill the space with something relevant & varied. Only once, early on, did I make the mistake of "just putting in the stuff to hand, as supplied" to fill the space. Grapevine reports (rarely was anything mentioned directly) suggested (quite strongly !) that was not the way to go, hence the change of direction.
 
Yet comments about the content of articles in MEW seem usually to elicit the reply "that is how it was submitted". There doesn't seem to be any "Editing" ? Just assembling "the stuff to hand, as supplied" ?
 
I appear to be somewhat out of step with the general concensus about the frequency & content of MEW. I have voted with my feet, so to speak, and so will make no further comment on either topic.
 
Regards,
 
Nigel B.
Thread: ME Forum
07/12/2011 19:21:39

Is anyone else experiencing problems accessing this site?
 
Yes, pretty well every visit. Very long page load times. I don't think that the plethora of flashing adverts will help.
 
I'm running Firefox on Win XP (or Linux on another pc - just as slow) & have a 30Mb fibre optic connection that checks out at it's rated speed.
 
Don't have similar problems with other sites.
 
Regards,
 
Nigel B.
Thread: Why are milling machines so b****y expensive
05/12/2011 13:27:28
I am not certain about the Horizontal mill but I am pretty certain that neither the Shaper nor the Planer have ever been fitted with CNC controls.
 
I have fitted CNC controls to both a horizontal milling machines & a planer while in my previous employment.
 
The milling machine was an Ajax & was converted from a manual machine by fitting ballscrews all round & a Heidenhain control to produce CRT grid frames for a Welsh based Japanese manufacturer.
 
The planer was a large Butler, again fitted with ballscrews (except the table) and a new heavy duty milling head (30Kw) in addition to the planing head. Again, a Heidenhain control & done for a railway points & crossings maker in South Yorks. They wanted to CNC plane radii on points castings. This worked up to a point, but tool clearance was a big problem & would have really required a rotating toolpost to keep the tool from jamming in the rail groove. The control also had a limit of 100 meters radius for circular moves - as some main line points had radii in the kilometers range, they had to be programmed as a aseries of straight lines (worked out by the Drawing Office).
 
I have also seen a CNC slotter, used by a manufacturer of tank & naval guns to slot the breech ring for the breech block
 
You can CNC pretty well anything if you put your mind to it !
Thread: MEW, would less be more?
05/12/2011 07:53:24
If you aren't happy with the content, then get and pen some articles yourselves, instead of keyboarding moaning about it.
 
I have never understood this attitude - how does my writing my own articles improve the magazine from my point of view ? I would have already read that article as I wrote it !
 
ME and MEW are not "Club" magazines, they are a commercial venture. ME used to employ staff writers - doesn't seem to be the case these days.
 
£0.02
 
Nigel B.
Thread: Titanium Wire
22/11/2011 21:11:16
I get several unsolicited e-mails every week from Chinese suppliers of titanium in various grades & forms - happy to forward a few if you wanted to approach one (or several) for a "sample".
Thread: metric taps
22/11/2011 21:04:25
Guess I've got strong wrists as I've been using dia-pitch for 30odd years ever since that was what I was tought and seldom break a tap

Ditto. Well, except for the strong wrists bit (Carpal Tunnel decompressions both sides !)

I cannot recall seeing any instances of "oversize" tapping holes being recommended on manufacturing drawings - the "Thread diameter minus pitch, rounded to nearest standard size" rule seems pretty universal.

Thread: SMW Autoblok/ Rohm
12/11/2011 16:05:46
The smaller Gildermeister "Manual Plus" CNC lathe at work has a 315 dia.manual Forkhardt 3 jaw chuck - we priced up a replacement earlier this year & it was about £3,100. I'm not sure what jaws (if any) were included with that. The Forkhardt chuck doesn't use a scroll, having a screw operated moving block that rotates a plate the drives the jaws through a limited stroke. The jaws are serrated & can be positioned to suit the diameter of the workpiece. If our operators would grease the mechanism regularly as instructed, then the expensive screw & moving block would not strip !
 
While waiting for the parts to repair our chuck, we bought a Chester 315 dia. 3 jaw scroll chuck off Ebay for less than half the price of the replacement screw & block (£1100 for the parts, £430 for the Chester chuck IIRC).
 
The Chinese chuck is suprisingly well made, but it's 2-part jaw interface (tenon / slot arrangement) is the opposite "polarity" to the Forkhardt, meaning that our extensive collection of soft jaws won't fit - hence the quote for a new Forkhardt chuck.
 
We also bought a 500 dia. Chester 3 Jaw scroll chuck for the large Gildemeister lathe- the jaw tenons on that are identical to the 700 dia. 4 jaw that came with the machine. That is also a well made chuck that cost around a fifth of the price of the next cheapest 500 chuck I could find.
 
HTH
 
Nigel B.
Thread: MEW, would less be more?
06/11/2011 16:03:19
I agree. The current 13 issue arrangement provides no more "content" than the old 8 issue arrangement, but includes far more advertisements - most of which are of no interest & of little relevance to me.
 
I have not not happy with the current content/advert ratio for some time now and, as I see no chance of any change for my idea of better, I cancelled my DD subscription a couple of issues ago.
 
I guess you can't please all of the people all of the time though, as I have subscribed since very early on (and have all bar a couple of early issues), it is a shame non the less. I stopped getting ME many years ago, as I have no interest in steam models or railways - maybe time to have another look at HSM ?
 
£0.02
 
Nigel B.
 

Thread: My Super-7 trips out
05/11/2011 15:57:55
Check that the current rating on the overload matches the motor full load curent on the motor rating plate. The overloads have a working current range that is adjustable, but setting to "maximum" may still trip if the overload maximum is less than the motor. The overload should be adjusted to the motor current & no more.
 
If that is OK, I would use a clamp-on current meter to check the current that the motor is drawing. If it is at or over the motor rating plate FLC, I would remove the input drive belt & check again. If still over current, have the motor checked out. If it is now under, how tight is the spindle drive line when rotated by hand ?
 
You don't say what speed range you have the machine set to, but if it is one of the higher ranges it may be that your spindle front bearing is set a bit tight. I run my S7 from an older inverter - my front bearing is set close enough that it won't start at the top couple of speeds (inverter trips) unless it has been "warmed up" for a while at a lower speed.
 
HTH
 
Nigel B.
Thread: Ground angle tool checking device
01/11/2011 19:16:27
Would something like this do :
 
http://www.swissprec.com/CGI/ISPDFF?PMCTLG=01&PMPAGE=96
 
The current J&L offer flyer landed on my desk yesterday - IIRC the basic 7X unit with a standard recticle is under £30, with the extra reticles around £9 each.
 
Nigel B.
Thread: RF30 Mill/drill replacement belts
28/10/2011 16:42:31
I have had a Taiwanese built "Tru-Tool" RF30 mill/drill (appears to be the same as the Warco Major) awaiting commissioning for a number of years - the main hold-up being it had a 3 phase motor and the intended fitment of an inverter was constantly slipping down the list of priorities.
 
But a Machine Mart Vat-free coupon was recently utilised to obtain a Clarke phase converter , which got the machine running - though rather lumpily. The poor running was traced to the original Vee belts having taken a set & the wrapping was coming away in places. As the original markings were quite clear ("GeminiRope" B42 and B34) I got replacements from my local bearing supplier.
 
They didn't fit - both being far too long to allow tensioning once fitted. When the original belts were measured, they turned out to be B40 and B32 respectively.
 
Whether the originals had been mis-labled, or the Taiwanese use different belt length standards to everybody else, I don't know. But I do vaugely recall having similar problems with a Sealy 12 speed pillar drill where I used to work some years ago.
 
I chose to fit more modern raw edge, moulded cog belts (BX40 & BX32), which fit well. I have yet to connect it up & see if the running has improved, but the drive arrangement does turn more smoothly by hand than before.
 
So if your imported machine requires replacement belts, it may be best to ignore any markings & have the originals measured to get the correct size.
 
Nigel B.
Thread: Collet Chuck
28/10/2011 16:23:41
I had thought I might be able to assist with these, as I have a box of similar shape collets that came from a scrapped automatic capstan lathe.
 
But when I dug them out today, while they are the same nominal shape they are different dimensions - overall length is 2.531", the ground end opposite the taper is 0.471" , the parallel section ahead of the taper 0.498", taper max dia. 0.734", taper min dia. approx 0.485", taper length approx. 0.451".
 
I cannot recall the make of lathe, but seem to recall that the collets were refered to as "dead length collets" - i don't think that the length of material protruding changes as the collet is tightend. The collet chuck on this machine was either pneumatically or hydraulically actuated & there was a bar feed fitted.
 
It seemed a shame for all the tooling that accompanied the machine to follow it into a skip, so the collets & few other bits were "rescued" - but a suitable holder / clamping arrangement for my S7 has yet to be designed.
 
Nigel B.
Thread: Anyone have a Worden grinder? Experiences?
27/10/2011 07:45:07
The Worden has stops fitted to the cross bar
 
Mine doesn't - the snail cam modification to the table tilt arrangement meant the original stop design wouldn't work. The original builder didn't come up with an alterative stop arrangement to work with the snail cam. I only realised that it should have had stops when I got a set of original drawings - I guess that's another project !
 
I think a linear bearing will suffer from dust penetration, so far I have had no problem with the cast iron block binding.
 
The ball bushings do at least have wipers to help keep grit out. As the two complete ex-equipment bushes & hardened rods cost nothing but my time to remove them from their original installation, I have little to loose trying them. Should the bushing life prove short, Igus manufacture plastic lined bushings designed to run dry that are dimensionally interchangeable with standard ball bushings. I had intended to add an oil seal at each end of the bushing as an additional wiper - might add a bit of extra drag, but it won't be as bad as the "as designed" arrangement. If your machine has the guide bar at the rear, you won't suffer the grit problem that causes my front bearing machine to get stiffer with use.
 
Nigel
26/10/2011 20:35:17
moved the pivot to its current (front) location as an "improvement". I've asked around but could never discover the reasoning for that.

I have an early version with the pivot at the front - bought competed at a Myford Open Day several years ago. It looks like it was assembled in a bit of a rush (or by someone learning the ropes) as it was unpainted & some areas of machining were a bit "rough and ready".

I have not used it much, but it does a better job of grinding lathe tools than I can accompish by hand. It has had a modification done to the table tilt arrangment - a snail cam instead of a curved, slotted strap and lock screw. I was only made aware of this when I came by a set of the original construction drawings. I can only guess that the original builder found the as-designed arrangement lacking.

One of the reasons it hasn't been used for much more than lathe tools is (IMHO) probably the reason for the change of table bearing arrangement. The front-mounted bearing gets covered on grinding dust and gets very sticky in operation. This isn't a problem when doing lathe tools, as the tool is swept across the face of the wheel, but I wouldn't want to try doing the end face of an end mill trying to avoid overshooting & catching the opposite tooth. It also doesn't have the angular markings on the table top, so I use a combination set protractor to set the angles.

I have (just another project !) a linear ball bushing & hardened shaft to fit in place of the original close-bored cast iron on mild steel arrangement. Hopefully this will give a bit more "feel".

I am happy enough with it for the £75 it cost me. I'm not sure I would spend upwards of £400 on the kit, though.

Nigel B.
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