paul
Member
Posts: 8
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Post by paul on Jun 13, 2007 18:00:48 GMT
Parting Shot. Get it? Picture of parting tool? Ah, forget it! I put this in a different thread to my other recent 'parting off' topic as I thought it might be a useful tip for others with mini-lathes (Warco, Clarke etc). I bought a knife-type tool in the smallest shank size but couldn't use it because the inclined blade is way above centre even without shims under the tool. Today I had a mini-brainwave - turn the blade upside down in it's holder then turn the tool over - with a bit of packing the tool can be raised to the correct height! The only disadvantage is that the blade-holder's screw prevents the tool from being held with a really small overhang but it's not too bad. It might be possible to re-arrange the blade clamp/screw to get over this minor problem anyway. I parted off a 1mm thick slice from a piece of brass hex as a test and it was great.
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Post by havoc on Jun 13, 2007 18:43:02 GMT
Well, I mount the tool upside down and run the lathe in reverse. Have to since I don't have a back toolpost.
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Post by steammadman on Jun 15, 2007 22:04:56 GMT
DANGER DANGER DANGER
JUST WHAT ALL THE PUNDITS FROWN UPON
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steam4ian
Elder Statesman
One good turn deserves another
Posts: 2,069
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Post by steam4ian on Jun 16, 2007 3:51:48 GMT
G'day steammadman. "Just what all the pundits frown up" Could you or the pundits please tell us more before I commit the same mistake. At present I can't see difference between the uplift from a rear tool post and the uplift on a reversed front tool post. For the 7x12 mini-lathe. which Paul's appears to be, the saddle is equally retained front and back.
Happy to learn, that's why I joined the group, so please reply.
One good turn deserves another. Regards, Ian
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lancelot
Part of the e-furniture
Posts: 471
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Post by lancelot on Jun 16, 2007 10:40:26 GMT
Any chance of your Chuck flying off and dancing across the shop floor, Havoc...forgive the pun... ;D
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steam4ian
Elder Statesman
One good turn deserves another
Posts: 2,069
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Post by steam4ian on Jun 16, 2007 10:58:07 GMT
G'day Lancelot. Thankfully the chuck on the 7x12 mini-lathe bolts to a a backing plate. The idea of a chuck becoming unscrewed is daunting, I wouldn't want to be in its way. One good turn deserves another. Regards, Ian
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Post by havoc on Jun 17, 2007 20:03:53 GMT
Yes, I would like to know the problem as well. The chuck isn't screwed on the headstock like in ancient times. It is the design with 3 studs through the head. I don't see any differences in forces on the cross slide, it just pushes on the other side compared to a back toolpost. So: WHERE IS THE DANGER ? Only difference is that the tool is mounted on the compound slide. I don't really like it. But I have given up on parting steel, only use it for brass and bronze.
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Post by Shawki Shlemon on Jun 18, 2007 11:03:16 GMT
Most modern !!! small lathes have their chucks screwed on the head stock shaft and if one is machining /parting etc while it is running in reverse there is a good possibility for the chuck to be undone and go for a fly .That is the danger .
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Post by baggo on Jun 18, 2007 15:38:13 GMT
Hi Paul,
the only snag I can see with your suggestion is that by turning the holder upside down you are altering the top rake on the blade from positive to negative (The blade is inclined in the holder to give the blade top rake without having to grind it). This might be ok for brass but may cause problems with steel etc.? It might be worth trying one of the 'T' type parting tools as one of those may sit lower in the tool post. I have similar problems with the quick change tool post that I use - a lot of tools are still too high even when the holder is at it's lowest position and I have to revert back to the standard Myford clamp type.
John
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Post by havoc on Jun 18, 2007 18:36:35 GMT
I do understand the problem with screwed on chucks, but I haven't seen any of that type in a shop since I started in this hobby 2 years ago. Even the old second hand ones had some system with bolts. Is this typical of english lathe design?
The parting tools I have in my collection have a square shaft to clamp them in the toolpost. So I guess it won't make a difference for that type of tools. Yes, I tried different types of parting tools, all with the same bad results on steel.
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