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Post by 02jcole on Apr 3, 2008 18:56:12 GMT
Hello,
I was very lucky to recently come by a very cheap Harrison M300, after stripping down the saddle and replacing various bits and pieces I have reassembled it. But it now drags the tool when passing backover the piece of metal that has just been machined, I have eliminated the backlash in the cross slide using the split nut and also locked the topslide, but it still occurs.
Anyone else own an M300 or have experience with setting up machine tools?
Regards James.
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steam4ian
Elder Statesman
One good turn deserves another
Posts: 2,069
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Post by steam4ian on Apr 3, 2008 19:27:11 GMT
G'day James. Now you know why you got it cheap  Isn't that normal?  I am saddled with a Chinese effort and consequently correspond a lot with others with a similar burden. We have to rebuild our machines as we start using them. Have you checked your gibs, top slide, cross slide and saddle? Either the gibs are allowing the tool to spring or the saddle is slewing. BTW, nice lathe; DROOL.  Regards, Ian |
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Post by 02jcole on Apr 3, 2008 19:48:01 GMT
Hello,
The lathe turned perfectly before I brought it as I tried on purchase from a liquidated engineering company. So it seems I have created the problem as they say " If it ain't broke don't fix it"!
The problem is I don't know any of the tips or tricks that the fitters used to set the saddle up...
Regards James.
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Post by dickdastardly40 on Apr 4, 2008 6:40:17 GMT
James,
I've a fair amount of time stood in front of a M300, though no quick fix for this.
You'll have checked these but Devil's Advocacy insists I ask:
Is the tool post tight and the tool within?
Is the large screw on the front of the saddle that holds the tapered gib strip tight?
Can you feel any slop in the saddle & crosslide by hand using firm tugs?
No other quick checks come to mind, I expect it's something silly.
Al
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Post by weldsol on Apr 4, 2008 7:32:01 GMT
Silly question but have you called Harrison's technical dept, as they should be able to help 01924 415 010
Paul
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Post by mutley on Apr 4, 2008 8:00:50 GMT
how heavy a cut are you taking? It may just be the result of the work piece flexing under the cutting load.
Andy
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Post by 02jcole on Apr 4, 2008 8:46:59 GMT
Hello,
I haven't yet tried phoning the 600 group for some harrison support as I'm not sure whether they would want to help.
The tool and toolpost is definately rigid, but will have to check the screw for the tapered gib strip.
The problem only occurs when you change the direction of cut i.e. retract the saddle away from the headstock after taking any size of cut, but it is more noticeable with heavier cuts. This leads me to think that the saddle is able to twist on the bed, or some of the slides able able to lift when not under cutting load?
Regards James.
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Noddy
Statesman
Posts: 672
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Post by Noddy on Apr 4, 2008 10:43:33 GMT
It sounds like the saddle is rotating slightly.
If you have the tool positioned infront of the centre of rotation, then the slop will cancel out as during cutting, cutting pressure will keep the saddle tight, and during retraction, the halfnuts or the pinion will be pulling the saddle round the same way.
Keith
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Post by circlip on Apr 4, 2008 11:47:22 GMT
Might be a silly question James but have you checked that the machine is level and the bed is not twisted. A spirit level on the bed and across it will show. Ian.
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Post by 02jcole on Apr 4, 2008 12:39:32 GMT
Hello,
Yes, I levelled it the other day as it has adjustable feet.
Keith, I shall experiment with different topslide cseetings to alter the center of rotation as you say.
Thank you for all of you help so far, as I want to get this sorted so that it becomes an accurate and useful machine to me.
Regards James.
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Post by chris vine on Apr 4, 2008 21:40:16 GMT
Hi James,
I think you might find something out by putting a dial gauge in the tool post and positioning it up against a nice straight shaft in the chuck.
Then you can try racking the saddle by hand, with the hand wheel with the lead screw etc.
At least this way you know that there are no cutting forces at play and what you are seeing is not a spring cut (when the work piece/lathe give a slight second cut with no additional feed in).
You will have to put your detective hat on I think.....
Chris.
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waggy
Statesman
Posts: 747
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Post by waggy on Apr 6, 2008 9:09:04 GMT
James,
Are the headstock bearings adjusted correctly? The may seem tight but is the pre-load correct? You could be pushing the work away from the tool with the first cut, everything settling back in line as you run the tool off the job, hence the second cut.
Regards,
Waggy.
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Post by 02jcole on May 2, 2008 22:14:29 GMT
Hello,
I have solved the problem of the dragging tool, and found it it be the gib strips on the cross and top slide and also the adjust on the saddle, it must have settled down or bedded in since I rebuilt it! But as a consequence I now find the saddle tight at either end of the bed where the bed has had least use, is there any way around uneven bed wear other than a re-grind or will I just have to live with it?
James.
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