I've just completed my first 'real' project on my ML7 (a project fo work), and I am very happy with the results. Obviously I have learned great deal about turning, milling and boring as well as the mor fundamental things like what a pain in the ar*e it is to always have t convert from imperial to metric and vice versa. Luckily all the drawing I did were in Autocad, so I dimensioned them in both metric an imperial. However, I was looking at the digital readout bars on th Chronos, Arc Euro websites. I have some £8 digital calipers which us the same readout box, and they are great.
Has anyone fitted these bars to an ML7? I'm looking at fitting the th main ways, the cross slide and possibly my vertical milling slide. Wha is the neatest way of doing this, ideally without butchering my lathe!
Also, has anyone any experience of the rotary tables available from th above?
Garth Hi, apologies but my life is too busy to do your question real justice but a few "hard learned" experiences for you to consider with regard to a lathe DRO. More apologies if you already have considered these but your comments re the collet system lead me to believe that accuracy is important for you.
The way the lathe works the potential error (on work diameter) is twice what the DRO system claims for accuracy. Therefore a cheap scale working to .0005" will only position the cross slide to give accuracy of .001" on work diameter. Obviously if you use more expensive glass scales working to .0002" the potential error is .0004". Many, many (most?) people find this acceptable for 90% of what they need to do. I am one that uses a DRO system on my Myford but revert to the scales when trying (important caveat) to work to a couple of tenths. A hard learned lesson for me was a DRO is much easier to use but not necessarily more accurate than I can achieve with the normal scales.
The cheap chinese scales as used for calipers etc are very vulnerable to oil and coolant and will fail if contaminated (personal experience). They need to be well protected if possible.
The Myford is one of the more difficult machines to fit a DRO system to as the available space is very limited.
There is a recent article MEW (I think) that covers fitting a glass scale system to a Myford (Machine DRO?). The article is here if you haven't read it:
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My own system is a BW Electronics wire system that I find really easy to use and extremely convienient but is not as accurate as one of the newer glass scale types. The choice was easy for me as at the time it was the only system that fitted the Myford with minimal impact. The question has been "done to death" in the forums over the last couple of years and you will find lots of good advice if you look round.
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There is a lot of good advice if you read through that thread. If you can put up with the accuracy limitations a DRO system on the lathe makes it very convienient to use.
Garth, not good posting again but I need to correct my previou
statement. The DRO fitting article I pointed you to does not mentio MEW so I guess that the two articles are different. Apologies for an confusion but the general layout is similar
Hi Garth, Ive got the 6" Shoba Rotary table from chronos. I bought the set with the plates and the tailstock (SOB1). Seems fine, works ok, and is reasonably well built. The handle is of larger diameter that the depth of the table when horizontal, so it wont sit on a flat surface unless the handle hangs off the edge.(I cant remember about in the vertical mode, but IIRC it clears) Not a problem for most things, but maybe important once in a while. The size is ok for small things, but you do run out of clamping space quickly on larger items.
Thanks for the advice. I did wonder about how well sealed the unit were, and hadn't considered the accuracy on diameter issue. I als looked at the article pictures of a typical setup. To be honest I thin I am better off just using the existing indexes on the handwheels an using my current measuring equipment. I may however invest in some o the 'zeroable' handwheel indexes, which will makes things a tiny bi less confusing!
By the way, I have sent the collet chucks back (kept the collet themselves though) so I am looking for another ER25 collet chuck now If I get another and it is still 0.003" out I will give up! I am no after totally perfect accuracy, but it was just that there seeme little pont in paying for the same accuracy as my existing chuck. I' have been happy with 0.0005" runout.
Dave,
I am still considering the rotary table, but I will see how I go o with my forthcoming steam engine project before investing in anythin elso too expensive.
Regarding the rotary tables: I was considering one to fit to my ML lathe. Please excuse my ignorance, but I can't see the point of th tailstock. Fair enough if you are using it for a milling machine, but intended to use it mounted vertically for radial drilling/milling o components using the headstock chuck, or mounted vertically for axia milling/drilling, again using the headstock chuck. Also, why would yo need dividing plates? Surely the handwheel is accurate? Is this jus for quick repetitive jobs? The reason I ask is because there ar packages with a rotary table, tailstock and dividing plates.
It isn't That impossible to turn up a chuck to fit the collets from a lump of steel. That way you will be ensured of a perfectly centred chuck on _your_ lathe. I did this for a collet chuck, and am happy that I got a better result than the original.
PS. If you must use a web based front end to a Usenet group, try to learn to quote properly :-|
If you are machining something (say a gear on an arbour) that is a bit flexible, then the tailstock can give necessary support to stop things from moving out of the way of the cutter..
Similarly cutting something like a 14 tooth gear is a lot easier with dividing plates than by working out the degrees to turn.
PS. If you must use a web based front end to a Usenet group, try to learn to quote properly :-|
You'll probably find that any rotary table of sufficient size to allow a reasonable amount of work (ie 6" or bigger) wont fit on your lathe in a sensible way to achieve what you are describing. I initially had thoughts along the same lines, but my harrison (4.5" center height - an inch more than a 7) is to small to bolt the RT to the boring table and still expect to use it... I did use my RT on a cheapy drill press for a while, but it was a PITA to position the offset for PCD/bolt circles... Dividing plates are for dividing, if you want (say) 11 equally space holes (32.7272 degrees apart)then doing that using the degree scale is much harder than counting (say) 15 holes on a circle. Not a good example, but illustrative I hope. The Tailstock is for the same purpose as the lathe one, to support the end of what ever you have mounted on the RT.
I used the nut that came with the (MT2 based) chuck and turned threads to fit it. One could turn a nut from scratch, but it might be easier to buy one and make the chuck to fit it.
Practice, It's a pain having to edit your posts in order to reply to them!
Better still, get a news reader and a connection to a news server, rather than relying on a ghastly, parasitical, web-based front end.
I have arranged with Chronos that I can keep the original collet chuc f.o.c.
Further to your idea of machining my own chuck, I am going to try t re-machine this existing one.
Can you think of any problems with this?
First of all I am going to find the axes of the register and the tape and see if they are indeed 'off'. If they are coincident I guess I'v got a problem with my lathe.
In one of the lost posts in your other thread Norman Billingham posted description of how he fixed his similar chuck. You might not have seen it as rc groups failed to pick it up. You can see the whole thread through google groups though.
Norman wrote-
"I've had this problem and, if you google around you'll find some discussions with Jim Guthrie about it.
I swapped my first Chronos one for a new one which was no better, then returned that and got an Arrand, which was a bit better but still ran out about 0.002".
I fixed it as follows;
Centre drill the ends of a piece of 10mm bar, slide a 10mm collet onto the bar and mount between centres.
Mount a DTI in teh tool post at exact centre height, bearing on teh cone of the collet.
Adjust the topslide so it tracks along the cone with zero runout i.e. set the topslide angle exacly to the taper angel of the collet.
Mount the ER25 chuck. According to Arrand it should be pulled up tight to the back register then the tommy bar given a tap with a hammer to seat it rock solid on the register.
Uisnig a rigid boring bar, with a fresh carbide insert and wothte cross slide locked, use the topslide to take a cut across the conical surface of the chuck, taking off the absolute minimum of material - I thing I removed less than a couple of "thou".
After this, mine showed zero runout. On removal and replacement it typically manages better than 0.0002.
Worked for me but as others say, this advice is worth exactly what you paid for it! "
Looks very possible to me from what Norman says depending obviously on how hard your particular chuck is. You will need to make the same test bar/holding fixture to both check register/collet seat concentricity and to re-machine the seat so no wasted work. There is another thread that talks about checking reister/backplate mounting that you might find useful here:
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Sorry if you have already seen it but it seems to cover most problems that you are likely to find if the problem is with your spindle/chuck mount rather than the chuck its self.
Thanks for taking the time to copy Norman's post, and apolgies t Norman because I did not ever get to read his original reply. Perhap I'd be better off looking at this forum on Google Groups.
One thing I did not check was the runout on my lathes nose registe abutment. I will do that tonight, and assuming all is o.k. I wil follow Norman's procedure for trueing the original collet chuck.
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