Here is a list of all the postings mgnbuk has made in our forums. Click on a thread name to jump to the thread.
|Thread: Drive Belts - Link or Vee?|
Only had bad experiences with modern, plastic, link belts - both at home (Boxford CUD) and at work (J&S Cylindrical grinder). On the CUD a link belt has to be used, as it goes through the swarf tray to loop around the spindle. The original 1960s Boxford belt used a canvas based link, rather than the hard, shiny, fibre reinforced plastic links used today. Even bow-string tight the new belt slipped under load so, when I had to choose between a Super 7 & the CUD, the CUD went. Similar situation with the J & S grinder, which had 3 belts - we were recommended to use link belts for smooth running, but belt slip limited the load that could be applied (the machine had been converted into a CNC cut-off grinder to slice carbide tubes into short lengths for mechanical seals).
I much prefer raw edge, moulded cog wedge belts, as these conform well round small diameter pulleys, don't need to be excessively tight & drive well. I have no use for a power transmission system that doesn't transmit power when I need it to. Properly maintained (i.e. tensioned) endless belts last a long time, so the minor inconvenience of having to drop shafts or spindles out to change a belt is, to me, just that - a minor inconvenience.
Have not had much sucess with poly-vees in industrial applications either - but that is another can of worms !
Do you have a trophy supplier locally ?
We used to use one to produce engraved switchplates at my last employer - they are set up to engrave cups, trophies, nameplates etc.
|Thread: Colchester Student 2500 (Harrison M300)|
They are helical albeit very slight.
Somewhat blurry picture of the M330TDI - pretty certain these are straight cut. The bottom (engaged) gear shows wear due to the thread helix angle. The M330 is close to the M300 - vari-speed headstock rather than step gears - the apron appears to be the same as the M300 at my last employment. The gears are 3.2mm thick.
Technically I think they need to be helical gears, but I expect you could get away with straight cuts at the helix angle of the leadscrew.
I don't think they are that sophisticated, from memory of stripping the TDI down to un-sieze it on the Harrison M330 at work - I think they are straight cut from thin plate. I can drop them off tomorrow to measure up / photograph if that would help ?
|Thread: Zero backlash?|
As with many engineering items, Chinse manufacturers can provide suprisingly cost effective solutions. I did a quick measure on the table screw of my FB2 clone - 20 diameter 3mm pitch trapezoidal screw, overall length around 700mm.
This would probably be a reasonable place to start and, at £38 delivered for a 750mm long screw & bearings, isn't too pricy ? This may not be totally backlash free (but it won't have a huge amount of backlash) & probably wouldn't be up to making sub-micron parts on a 24-7 basis, but I would be happy to give one a go at that price if I needed to replace a worn-out screw (or fancied doing a CNC conversion) - particularly as Pro Machine Tools list FB2 table screws at £156, with the nut another £156 !
|Thread: KATSU MINI LATHE|
For instance, a centering lathe is a dual head machine in which the work stays fixed and the heads move towards the workpiece and machine a center drill hole into both ends.
The reviewer is not wrong :
Quite how that is relevant to a mini lathe review, though, isn't immediately obvious.
|Thread: Zero backlash?|
you will be after the double nut type if you want a preloaded zero backlash ball screw.
Not necessarily. Most ballscrew manufacturers can supply single nut, internally preloaded backlash free screw assemblies. These have two (or multiples of two) ball circuits ground with a slightl linear offset in the nut & the preload is obtained by ball sizing. Ballscrew manufacturers grade balls in micron increments & use these to get the required preload. We used these a lot in my last employment for CNC use, where they worked well and gave long, reliable service. If they lost preload due to extended use, a relatively inexpensive reball would get them going backlash free again. We initially used PGM screws, then Hiwin after PGM were taken over by THK, who dropped the internally preloaded PGM screw range.
We also used German "Star" brand backlash free rolled screws, which had adjustable backlash obtained by a varying the "crush" on the split ballnut housing. They worked reliably as well & were noticably cheaper than ground, preloaded types.
Bear in mind that backlash free, preloaded support bearings are needed with ballscrews to get a backlash free drive solution.
they are less able to 'self lock' so unless you keep a hand on the handles the cutter can pull into the work
In theory. In practice, they work fine - more than enough drag through the slides so pull-in isn't a problem on a Bridgeport-sized machine. None moving axes would be locked via other means, so not an issue there.
I put handwheels on ballscrews on a Taiwanese CNC kneemill at my last employment & ran it as a manual machine for years without any problems using HSS drills, endmills & a 50mm 3 insert face mill. As the machine was built as a CNC carcass it had Turcited ways, so should have been more prone to pull-in if anything - again theoretically, as in practice it didn't happen.
|Thread: Arc welder cooling oil.|
Is Brighouse, West Yorkshire near enough ? Millers Oils list transformer oil **LINK**
|Thread: Steinel SV4 milling machine problem|
Looking through the manuals in the links provided above, the vertical spindle just appears to have a captive drawbar for the MT3 spindle. Can't see a spindle lock, just flats on the sindle nose. In that regard, it is an almost identical arrangement to my Emco FB2 clone - to remove tools on my machine I use the spanner provided on the spindle nose to hold the spindle & unscrew the drawbar against the nut on the top of the spindle that holds it captive until the taper breaks free. No hammering required. I prefer to tighten my MT2 collets sufficiently to ensure that there is little chance of the tool pulling out in use, so removal can require a reasonable amount of pressure to release.
Given the bearing arrangement shown in the exploded diagram, I would be wary of assaulting the drawbar with a hammer - the ball thrust bearing used to set the main taper roller spindle bearing free play will not appreciate that !
|Thread: What did you do Today 2018|
I don't know if you got a manual for yours but if the Chinglish is too strong to make sense of, there are various other manuals out there that will do the trick.
Certainly not the easiest translation to understand ! A copy can be found at the link below, if anyone feels like a challenge. Might get a more accurate / readable translation by finding a Chinese copy & cut and paste the text into Google Translate - I doubt it could be much less intelligable.
Presumably you had your scales come loose, Neil ? A bit of Screwlock woon't go amiss, thanks for the reminder.
|Thread: Brass bar , 55 mm - ?supplier|
eBay item number: 273050215411
A 200mm length of 55 diameter is £60 delivered - out of touch with metal prices, so don't know if that is par for the course or OTT
|Thread: What did you do Today 2018|
New toy arrived at work yesterday, connected up on the dining table (as you do ....) today to make sure it works - which it appears to do. Bought from Ebay seller pjsparker, it was ordered on the 8th of this month, notified as despatched on the 12th & delivered (in two packages delivered by two different carriers) on the 17th.
This is destined for my Taiwanese FB2 clone. I was thinking of changing this machine for one of the WM18 type, but recent events (plus a lack of ready availability of a 3MT machine) prompted another measure-up of the FB2 - it is a bit shorter in the table travels than the WM18, but has a good spindle-table clearance & I know it is reasonably accurate all round. So I decided to improve its usability with the DRO & have a stepper motor feed on the go for the head.
|Thread: Proxxon lathe PD 400|
I have NOW used a test bar and it is pointed nicely at a centre held in the tailstock ... the error only shows up when cutting ...hmm ... hmm ... that might point the finger at the roller bearings...
But have you checked that the bearings are correctly adjusted before condeming them ?
Mount a chuck & chuck up a length of stout bar. Set a dial gauge from the bed to indicate at the top of the chuck backplate (12 o'clock). Grasp the bar & lift it away from the bed firmly. If there is lift in the spindle, it will show on the dial gauge. Adjust the bearings until you get no lift, add a small amount of preload & try a turning and boring test again - do both to see if the taper problem is apparent inside & out. If you cannot adjust to a "no lift" situation, then consider replacing the bearings.
When rebuilding CNC lathes in my last employment (much larger machines than a Proxxon !), we used to "bump" front bearings off the spindle. The spindle was stood upright on its rear end on a piece of wood (railway sleeper), then a stout bar was bolted across the chuck mounting face. Two of us lifted the spindle a few inches off the sleeper (the top of the spindle was about shoulder height with knees slightly bent from the floor/ sleeper) then dropped it vertically. With repeated "bumping", the front race walked off it's seat with no damage caused. The spindle also had a safety sling loosely mounted from the O/H crane so it couldn't fall over accidently if we got "out of sync" with the lift & drop sequence. The replacement bearing was warmed with an induction bearing heater & then it just dropped on.
Joe's experiences re: loose bearings appear to be different to mine - spindle bearing problems pretty much always manifested themselves as surface finish defects for me, not alignment issues. 0.002" lift on a newly rebuilt machine for an oil industry customer was enough to fail acceptance due to chatter while screwcutting - adjusting the bearings so there was no lift (which required the use of a crane on a bar bolted to the spinlde nose - couldn't tighten the adjusting nuts sufficiently by hand !) completely cured the problem. These were "NNU" type expanding roller bearings , though, not taper rollers - but a loose spindle is still a loose spindle regardless of the bearing arrangement ! At the employer before that, heavy lathe spindles were preloaded by running temperature - if the headstock didn't get to 40 C after a predetermined period at full speed, they were too loose, over 50C they were too tight. These were taper rollers, a "fixed" pair at the front end & a "floating" pair at the rear - as the hollow spindle passed 16 5/8" though, I would guess the bearings were around 24" bore.
lathe boring taper, not parallel.
How is it turning ? Are O/Ds not parallel by a similar amount in the same direction ?
I would expect a bearing issue to show up as surface finish / vibration rather than taper on the workpiece. Clean, smooth, shiny taper roller bearings sound like new ones ! I would regrease & re-install them, then set to zero play / lift (or slightly preload) and try your cutting test again, both boring and turning, before diving in further.
Have you tried checking the headstock alignment ? The usual way is with a Morse taper test bar in the spindle socket, with a dial gauge mounted on the saddle. "Normal" alignment is for the test bar to point slightly upwards & towards the toolpost (slightly being around 0.001" per foot). The test bar set between centres can also be used to set the tailstock for parallel turning, though a test bar of the tailstock socket taper is required to check the actual tailstock alignment. At a pinch, you could go for a 2MT test bar to fit the tailstock & use a 2-3 sleeve to check the headstock, though adding the sleeve also adds a potential source of error.
If you want to start throwing money about, a test bar would be a better place to start than changing out the bearings initially IMO - you could recoup much of the cost by selling it on later if you felt you no longer needed it after use.
|Thread: EMCO FB2 electrical help|
The Emco FB2 Operating Instruction manual & Spare Parts List can be downloaded **LINK**
The manuals are in German & the Operating Instruction manual (Betriebsanleitung) has wiring diagrams.
|Thread: Motorcycle General Discussion|
I can feel a bit of a shock but not enough to generate a spark
Might be that the flywheel needs remagnetising, rather than the condensor ?
|Thread: Soft start|
Plenty of cheap thyristor speed controllesr / dimmers on Ebay :
2Kw rated 192410752118 £1.23 delivered
4Kw rtaed 192410975598 £2.85 delivered
5Kw rated 192441295326 £4.69 delivered
I have used the 2Kw type to reduce the speed of pistol drills - put the module in a small diecast box wth a 13A plug on one end & a trailing socket on the other, so it could be put in circuit as required. Worked fine for my intended use, though for yours you would have to manually ramp up the speed with the pot.
|Thread: Imperial acme threaded rod|
If Abssac can't supply, this company **LINK**
were recommended by John Stevenson when this topic was discussed some time ago on this forum. If you go the download page, the standatrd screw products .pdf lists 1/2" 10 tpi LH and RH as stock products.
Edited By mgnbuk on 03/05/2018 16:09:56
Abbsac still list this as a "legacy product" **LINK**
Might be worth a call ?
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