Here is a list of all the postings Martin of Wick has made in our forums. Click on a thread name to jump to the thread.
|Thread: Lathe chuck not true.|
Thanks, I will check that later tonight and report!
thanks for that.
I think I understand, but just to be sure, are you saying remove the chuck body from the internally threaded back plate and then check the fore and aft run-out on the outer mating surface of the back plate to test if that surface is truly normal to the spindle axis?
That hadn't occurred to me as a source of error.
That old chuck problem again.
Generally, I thought I wasn't bothered by chuck run-out as usually try to avoid second chucking and I was using a Burnerd and they are good so we are told, so wasn't expecting significant run-out.
On having some issues, I actually checked with a DTI and was shocked to find a 10 thou total run-out (on both sets of jaws vs. less than 1 thou run-out on the outside of the chuck body (using silver steel test pieces).
So strip down, clean, inspect, relube and reassemble. There was no damage or obvious wear steps in the scroll, jaws or chuck body. In fact the jaws were in remarkable condition, no trace of bell-mouth or jaw damage evident.
On reassembly, slight improvement was noted to 9 thou TIR on both sets of jaws, slightly less for smaller diameters of silver steel (1/4, 1/2 and 5/8 was all I have to test).
The chuck is a Myford having a backplate with threads inside the chuck body and actually quite a tight fit, so wasn't expecting to gain much by rotating the chuck body with respect to the threaded back part. In fact this did help and gave a slight improvement reducing TIR to between 5 and 6 thou.
Experiments with shimming the apparently low side jaw with strips of paper showed that TIR could be reduced further (between 0 to 2 thou (which would be acceptable).
Assuming the chuck was good once, how can a scroll or jaws selectively wear to end up like this?
and should I now resort to grinding? to be achieved by carefully skimming off some material from the two apparently high jaws (say half thou at a time in the tool cutter grinder, replace, check, repeat until TIR is within reason etc). Or just shell out for a new chuck?
By comparison, the Chinese chuck on my Seig C1 is still within 2 thou TIR after years of abuse. No idea how old the Myford chuck is, the machine is mid 70s and has not had hard use. It is possible the chuck is the original but may not be.
Would appreciate any thoughts on whether there is anything else I can try before the dreaded grinding option. Don't want to grind in situ from the tool post either!
|Thread: 'What LatheXXXXX sorry 3D Printer should I buy'|
[ However, I did spot (thanks to a Forum post) the Aldi printer which appears to be one of these.
or possibly not. - because it looks the same doesn't mean it is the same for Chinese clones. Cant find a detailed spec on the aldi site to make a full comparison.
The PLUS version of the Wanhao i3 appears a better spec. compared to my basic I3 as the hot end is rated to 260c - if true this is useful as it will allow printing of nylon and other higher temp materials.
it is worth seeing if Aldi will provide you with the full spec of the machine including the firmware type and temperature ratings rather than just the marketing blurb. Remember, they are selling a clone of a clone, so what you see is not necessarily what you thought you were getting.
I have been pleased with the performance of my basic Wanhao, however in engineering terms it could have been so, so, much better with minor design tweaks to stiffen the Y axis and use of double linear bearings on the Z. Having said that, the quality of prints has exceeded my expectations without much more tweaking than speed and acceleration. I believe I can get better from it if I need to.
Note of caution, if you are minded to print high temperature materials, you may want to check whether the machine incorporates a Mosfet to supply the heater bed, because if not then upwards of 10A is being routed through the control board which has been attributed to early board failure. One of the planned upgrades that I did manage to do to mine - for peace of mind (and the only one so far - too busy printing to bother with any others!)
|Thread: Is a tool & cutter grinder worth having?|
Yes if you have the money and what is on offer has sufficient accessories to match your requirements.
However, if your requirements are relatively modest, you can go quite far with an adapted bench grinder and one or other of the tool rests described in the workshop practices book 'tool and cutter grinding'.
I used the simpler tool rest for years before acquiring a Stent T&C grinder. I still prefer the home-brew version if I want to quickly tidy up an edge rather than go to the faff of setting up the Stent. Stent is great if you want to spend a wet afternoon rounding up all the bits and pieces around that need reclaiming or making a special tool.
|Thread: Aldi to stock 3D printer|
As pointed out you can get the wanhao I3 from a UK supplier for less than £300 - doubt if the Aldi clone is significantly better or worse than the UK supplied version but the UK supplier is a specialist 3d printer outlet that offers support.
What I do know is the i3 is a very competent printer out of the box and without much finessing. cant say if it is as good as £900 printers but I bet there are some high cost printers that are not as good as the i3. I would suggest it is slightly stiffer than a Prusa, but not by much. Y axis can be improved though.
I used mine to produce some very serviceable MXL timing gears to drive a mini wood lathe (the picador pup no less!) and a bunch of 20 DP gears for the M7 (well not actually for the M7 but for an EW to replace the absurd DP16 set that came with the EW). Plus a whole bunch of other bits an pieces, mainly PLA. The supplied bed/print head will get hot enough for ABS, but not nylon
Not perfect by any means and all modestly priced 3d printers suffer the old engineering bugbear of a lack of rigidity, but this can be addressed if required, also in the case of the i3, the stated print height was a slight exaggeration more like 170mm than 200..
However, I was well pleased with it so far and you can use it 1/2 and hour after unpacking.
If new to this recommend you do your research etc
|Thread: Screwcutting on a Myford ML7 - part 2|
Thanks for that chaps, that's 2 votes for the 'cut and try' method then! - no harm in that as it is what most of us do most of the time! I fully expect to spend a lot of time cutting practice and test pieces. Appreciate the point regarding clearances on thread diameter on lathe cut threads but wondered if there were any actual published data or whether this is simply a mater of practicality?
What I was trying to get at with the post in relation to the original question was that the diagram of whitworth thread dimensions that you see endlessly regurgitated throughout the literature and now the WWW, can only precisely work if you use a form cutter (assuming you wish to get to the dimensions set out in the standard).
Even the very excellent Sparey (I have a 1948 first edition!) is as guilty as all the others in not pointing out that if you use a single point cutter at a cut depth of 0.64p from the major diameter, you will not achieve the correct Whitworth dimension of thread width and nose radius. A similar issue would apply to all types of threads due to the limitations of the single point cutter. If using a form tool, thread chaser or die head etc, then there is no issue with the dimensions as quoted.
Does this matter? - probably not in 90% of cases, as I get the impression that threading is not regarded as precision process - as long as the threaded part more or less fits and doesn't actually drop off when turned upside down seems to be the acceptable level of tolerance (although there are general guidelines and suggestions on engagement and minor diameter tolerance etc for various threads).
However, I was hoping to confirm a rigorous process from a known point of precision and then let natural expedience, practical bodgery and lack of competence determine where I end up - and when it ends in tears, at least I know that I started at the right point even if I got lost along the way!
Thanks to all.
Sorry to resurrect an old thread, but the original post noted the general lack of guidance or principles in the literature for screw cutting with a single point tool. ME handbook is a good start, but is hardly a practitioners guide.
If the diagram in 4.1 in the ME handbook for BSW is to be believed, then apparently there is no thread flank clearance for BSW threads - can this be correct? The thread engagement is not stated - do we assume 70% as drawn?
I admit I have no experience of cutting threads on a lathe but am planning the process for cutting an M7 backplate. I am more than happy if anyone would correct the approach I plan to use in the worked example below.
So we assume a perfectly ground single point tool ending in a sharp V and imperial dimensions.
As I am a beginner, for the avoidance of error, the tool will be used in a way to initially cut the full thread height given as 0.96p, not the truncated form. The threads will truncated in a second operation using the dimensions given in 4.1.
Therefore, if cutting an external thread of 1.125 inch nominal for 12tpi (0.08333 pitch), I would start with material that is 1.1516 diameter ie. truncated form plus 2x 0.16p or 1.125 + .0266. Then advance the cutting tool 0.0799 (based on 0.96p from 4.1)
The threads should come to a nice sharp point at the end of thread cutting and be a visual confirmation that the cut had been completed.
I would then truncate the new thread by advancing a cutting tool 0.0133 in. (0.16p) to generate the truncated form of the major diameter, restoring the external diameter to 1.125 in.
If I was cutting the internal thread, I would bore out to the untruncated minor diameter, calculate from the untruncated major diameter (above) minus 2 times the untunctated full thread height.
In this example it would be 1.1516 - 0.1598 or 1.1516- 2(.96p) that is equal to 0.9918 in.
The threads would be cut by advancing the tool by the same 0.96p or 0.0799 in. followed by a cut with the boring bar of 0.0133 in. to generate the truncated form of the internal thread.
I am relying on the fact that the nose threads on my clapped out M7 are so worn that additional thread clearance cuts will not be required, but if cutting a matching set of threads I would probably go in an extra thou or two for flank clearance -
hoping that somebody may know if there is a standard for BSW flank clearance?
Also recognise that as an alternative, you could start the internal threading by boring to the minor core diameter of the truncated form and then making a threading cut by advancing the tool 0.8p or 0.0666 in. and avoid the second operation to truncate the full height threads. But I quite like the idea that at the end of the thread cutting process you have a sort of visual check - if the flanks come to a sharp point on the final cut, then possibly you can be reasonably confident all has gone well - at least until you try to screw the two parts together and learn something else!
Of course, in trying to establish a set of repeatable practical steps, I may have completely misunderstood the approach required and got it all completely wrong- don't hold back you will be saving me from scrapping a backplate!
Also happy to hear other methods from anyone experienced in screwcutting or whether there are more reliable or simpler methodologies for use when form tools or taps are not available.
|Thread: New chinese lathe or old Myford lathe|
Forgive my crust for a first posting, but I would avoid anything badged as a Myford unless you really, really understand what you are getting. The ones that look like a bargain will be in poor condition and the ones that are in good condition are overpriced (ask me how I know).
As the owner of a S7, I would agree there is nothing 'super' about this relic of 1930s technology or the fact the spindle bore will only pass just over 1/2 inch ( which causes significant wastage of material). It is a joy to use (sometimes), but like a vintage motorcycle, you need to drive it carefully for good results.Yes, spare parts are available, at a cost in time and/or money and you can spend more time fettling the ruddy thing than actually making stuff.
A friend has one of the new WM 250 (other sources available) which comes with most of the basic kit included in the price and has a decent 1" headstock bore. To my jaundiced eye, it was an impressively smooth, quiet, fast, swarf generator and generally tolerant of the levels of abuse that I am wont to inflict on a lathe. I felt the bitter stab of lathe envy.
With the grand plus that you can save over the cost of a top notch S/H Myford you would also be able to buy a shed load of whatever tooling you require (that is new tooling, not 50 yr old worn out relics of faded engineering glory).
Due to the fact the pound in your pocket is now worth less than plastic washer from B&Q, the imported equipment is now more expensive than a couple of years ago. But if I was squandering my money again and not wanting to support the heritage industry, I would be getting a modern machine.
Just my biased 5p worth!
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