JeffP Posted January 18, 2015 Share Posted January 18, 2015 Can someone please explain why the parting tool is upside down at the rear? Surely that means the piece is now trying to LIFT the parting tool, which makes it LESS stable? Link to post Share on other sites More sharing options...
Guest Isambarduk Posted January 18, 2015 Share Posted January 18, 2015 "Surely that means the piece is now trying to LIFT the parting tool, which makes it LESS stable?" Yes, but more to the point, it is trying to push the headstock spindle down into the headstock bearing which is 'a good thing'. Also, if the parting-off tool does decide to dig in (as if they ever would!) then there is negative feedback (ie more stable) in this arrangement in that the tool will pull away from the job; in the conventional arrangement, there is positive feedback (less stable) so, once the tool has dug in, it is pulled further into the job and .... we all knows what happens then! David Link to post Share on other sites More sharing options...
ian@stenochs Posted January 18, 2015 Share Posted January 18, 2015 "Surely that means the piece is now trying to LIFT the parting tool, which makes it LESS stable?" Hi, The saddle is locked to the bed, you can see the locking nut and spanner still in place on my photo, and my cross slide gibs are adjusted to minimise play. If the tool digs due to my over enthusiastic feed it tends to lift thus releasing it from the work. With the tool upside down the swarf falls away from the cutting edge and doesn't get jammed as it often does with the parting tool in the normal tool post. Hope this helps. Happy modelling. Ian. Link to post Share on other sites More sharing options...
JeffP Posted January 18, 2015 Share Posted January 18, 2015 Yes, thanks for both explanations. (Rushes off to see if such a beast exists for the EMCO Compact 5) Link to post Share on other sites More sharing options...
Guest Isambarduk Posted January 18, 2015 Share Posted January 18, 2015 "Rushes off to see if such a beast exists for the EMCO Compact 5" If you have an EMCO Compact 5, it should 'not be beyond the whit of man' to make one. Many years ago there was a design in Model Engineer called the Gibraltar Toolpost - because it was as solid as a rock! My father made a rear toolpost for his Myford ML7, which was a straight forward fabrication with a bit of machining. It is permanently mounted on the cross-slide and I use it every time I'm parting off. David Link to post Share on other sites More sharing options...
JeffP Posted January 19, 2015 Share Posted January 19, 2015 I think I'd better learn to use the milling machine first.... Link to post Share on other sites More sharing options...
ian@stenochs Posted January 19, 2015 Share Posted January 19, 2015 I think I'd better learn to use the milling machine first.... Hi. You dont need a milling machine! All the machining was done on the lathe. 1. The stock was faced off while the stock was held in the 4 jaw chuck. The ficing hole was drilled at the same time. 2. With the stock bolted to the cross slide the slot was milled with the cutter in the chuck. Add packing to extend slot down and upend stock to extend upwards. 3. The clamping screw holes were drilled in the vertical drill but could have been done by clamping the stock to the cross slide. 4. I used a Myford tee nut but the long screw was threaded while held in the 3 jaw with the die in a tailstock holder but could have been done in the vice with a normal hand held die stock. Socket screws and clamp nut are commercial items. Hope this is of help. Happy modelling. Ian Link to post Share on other sites More sharing options...
JeffP Posted January 19, 2015 Share Posted January 19, 2015 Yes, it is, thanks again. See...it shows my lack of experience, because all I thought of was holding the piece in the lathe jaws and having that turn, not keeping the piece still and having a tool in the lathe jaws. Link to post Share on other sites More sharing options...
buffalo Posted January 19, 2015 Share Posted January 19, 2015 I've been thinking of making a rear-mounted tool post for parting off as illustrated by Ian for the last few months. Part of the reason for not having got around to it is that there is an alternative for lathes with a reversible spindle. That is to mount the tool upside-down at the front and run the spindle in reverse. My gut feeling is that with this approach it would be easier to see what was going on. Any views on the relative merits of the two methods? Nick Link to post Share on other sites More sharing options...
TheWeatheringMan Posted January 19, 2015 Share Posted January 19, 2015 I've been thinking of making a rear-mounted tool post for parting off as illustrated by Ian for the last few months. Part of the reason for not having got around to it is that there is an alternative for lathes with a reversible spindle. That is to mount the tool upside-down at the front and run the spindle in reverse. My gut feeling is that with this approach it would be easier to see what was going on. Any views on the relative merits of the two methods? Nick Hi Nick, Fabulous - very many thanks for that, its something that hasnt ever occured to me. I make replacement brass wheels for Lima locos and parting off has often had the odd problem. Will try your sugestion and see what happens. My lathe is an Axminster BV20M with Dickson type quick change toolpost/holders also from Axminster. Not sure how setting centre height will go with the q/c posts once tool is upside down but i'm sure it will be do-able. Many thanks again. Regards Link to post Share on other sites More sharing options...
JeffP Posted January 19, 2015 Share Posted January 19, 2015 Mine goes backwards too! But my parting tool doesn't fit properly in the EMCO quick change toolholder...I can't get the correct c/h. I contacted the importers, expecting that there was a special holder for parting tools, to be told not so....... Link to post Share on other sites More sharing options...
buffalo Posted January 19, 2015 Share Posted January 19, 2015 Jeff, It would require making a holder to get the tool to the right height, but that would be a fairly simple task. Nick Link to post Share on other sites More sharing options...
ian@stenochs Posted January 19, 2015 Share Posted January 19, 2015 I've been thinking of making a rear-mounted tool post for parting off as illustrated by Ian for the last few months. Part of the reason for not having got around to it is that there is an alternative for lathes with a reversible spindle. That is to mount the tool upside-down at the front and run the spindle in reverse. My gut feeling is that with this approach it would be easier to see what was going on. Hi. My parting tool holder has a fixing screw on right hand side, see my picture, which does not let the tool get close to the chuck if held upside down in front tool post. Not a problem with small stock or brass but co uld be if larger steel being parted. If he tool is set up to the correct height before starting you dont need to see the cutting edge. There is not much you can do if there is a dig in as there is usually no warning, it just happens sometimes with a bang! Been there got the tee shirt! Rear post allows the swarf to fall by gravity away from the cut. Happy modelling. Ian Link to post Share on other sites More sharing options...
JeffP Posted January 19, 2015 Share Posted January 19, 2015 Jeff, It would require making a holder to get the tool to the right height, but that would be a fairly simple task. Nick Do you mean a new part for the q/r tool holder? Or a new part for the parting tool blade? It seems odd to me that EMCO make a q/r toolholder that can't be used for parting tools? Or maybe they aren't solid enough? Link to post Share on other sites More sharing options...
Guest Isambarduk Posted January 19, 2015 Share Posted January 19, 2015 "Part of the reason for not having got around to it is that there is an alternative for lathes with a reversible spindle. That is to mount the tool upside-down at the front and run the spindle in reverse.Any views on the relative merits of the two methods?" The rear toolpost is a far better bet for parting off and other high load (slow speed) operations, such as using a form tool. On running the lathe in reverse whilst undertaking such a high load operation: beware unscrewing the chuck or collet from the headstock spindle! I agree with Ian, with the tool mounted upside down there is nothing to see and the swarf is far more likely to fall away than jam between the tool. David Link to post Share on other sites More sharing options...
PatB Posted January 19, 2015 Share Posted January 19, 2015 I've been thinking of making a rear-mounted tool post for parting off as illustrated by Ian for the last few months. Part of the reason for not having got around to it is that there is an alternative for lathes with a reversible spindle. That is to mount the tool upside-down at the front and run the spindle in reverse. My gut feeling is that with this approach it would be easier to see what was going on. Any views on the relative merits of the two methods? Nick Just don't even think about trying it if your lathe has a threaded spindle rather than a camlock arrangement. Link to post Share on other sites More sharing options...
ozzyo Posted January 19, 2015 Author Share Posted January 19, 2015 Just don't even think about trying it if your lathe has a threaded spindle rather than a camlock arrangement. My lathe has neither type of arrangement. One type of chuck is held in the M/Taper in the head stock by a draw bar and the other chuck on the head stock "driving" face by a number of screws. In both cases it's not the screws that transmit the force but the large driving area. Link to post Share on other sites More sharing options...
buffalo Posted January 20, 2015 Share Posted January 20, 2015 ...My parting tool holder has a fixing screw on right hand side, see my picture, which does not let the tool get close to the chuck if held upside down in front tool post. Not a problem with small stock or brass but co uld be if larger steel being parted. If he tool is set up to the correct height before starting you dont need to see the cutting edge. There is not much you can do if there is a dig in as there is usually no warning, it just happens sometimes with a bang! Been there got the tee shirt! Rear post allows the swarf to fall by gravity away from the cut. Thanks for the comments, Ian. I also have that tee shirt and it's part of the reason why I was thinking about this. The idea in my head was to make a parting tool holder that would fit in the normal toolpost with any clamp screw(s) on top so nothing to foul the chuck. Running in reverse with an inverted front-mounted tool also lets the swarf fall away under gravity. ...On running the lathe in reverse whilst undertaking such a high load operation: beware unscrewing the chuck or collet from the headstock spindle! ... Well, David (and Pat), I did say "a lathe with a reversible spindle". Like that described by Ozzyo, there's nothing to unscrew on mine. Nick Link to post Share on other sites More sharing options...
Guest Isambarduk Posted January 20, 2015 Share Posted January 20, 2015 "Well, David (and Pat), I did say "a lathe with a reversible spindle". Like that described by Ozzyo, there's nothing to unscrew on mine." Fair enough; I intended it as a general statement, rather than one specifically for you; sorry. My Myford can be revered (electrically), which is very useful for a power return when screw-cutting, but I always let the clutch in gently - just in case! David Link to post Share on other sites More sharing options...
dajt Posted January 20, 2015 Share Posted January 20, 2015 Hi all, Two comments. 1. That 'chuck guard' looks useless in the pictured position. Most of the chips flying off the work will be zinging straight over it. It would travel with the tool which is a limitation of the one that came with my lathe which simply closed over the chuck, but still... what's the point? Better off without it and wear safety glasses. Or does it protect your hand on the carriage wheel? I do get sick of hot chips falling onto my hand. 2. I have the upside down parting tool holder from Eccentric Engineering, and it is brilliant. My lathe has a camlock chuck so running in reverse is fine. If you can do this, the upside down toolholder makes parting off from the front incredibly easy. For some reason none of the lathes I've seen sold out here (Aus) have T-slots in their cross slide tables so you'd need to be drilling and tapping to use rear tool posts. Regards, David. 1 Link to post Share on other sites More sharing options...
ozzyo Posted January 20, 2015 Author Share Posted January 20, 2015 Hi all, Two comments. 1. That 'chuck guard' looks useless in the pictured position. Most of the chips flying off the work will be zinging straight over it. It would travel with the tool which is a limitation of the one that came with my lathe which simply closed over the chuck, but still... what's the point? Better off without it and wear safety glasses. Or does it protect your hand on the carriage wheel? I do get sick of hot chips falling onto my hand. 2. I have the upside down parting tool holder from Eccentric Engineering, and it is brilliant. My lathe has a camlock chuck so running in reverse is fine. If you can do this, the upside down toolholder makes parting off from the front incredibly easy. For some reason none of the lathes I've seen sold out here (Aus) have T-slots in their cross slide tables so you'd need to be drilling and tapping to use rear tool posts. Regards, David. Hello David, we now live in the H&S world, if the lathe M/C came with out some sort of guard you could clame (off who I'm not sure)! One night I went to work on my mill (Clarkson M1700) to find a monster of a cage fitted to the M/C table. The night shift foreman said what do you think, I think that most of my words were of the four letter type ending up with get it off my mill and I'm sitting over there until you do. It was removed before the end of the shift and put in the bin (a very large bin I may add). Please don't get me wrong H&S is very good but it has to be used in context, IE. if your working on a roof why have a H/V jacket and a hard hat on, what are you going to get hit by a 747 falling out of the sky? They will then do you a lot of good! OzzyO. PS. one of the best ones is the safety warning is on a pack of razor blades "warning contains sharp objects???????????????????????????? I want the things to be sharp! If they are not sharp what is the point? PPS. you can not now buy razor blades if you are under 21? unless you have I.D. 1 Link to post Share on other sites More sharing options...
smokebox Posted January 20, 2015 Share Posted January 20, 2015 One of the causes of digging in when parting off with a front mounted toolpost is wear in the crosslide feed screw which allows the tool to be pulled in towards the job. With a rear mounted toolpost the tool tends to get pushed away from the job. When parting off on a front toolpost you can mount the tool a few thou below centre height which helps to reduce digging in. I also loosen the drive belt slightly on my lathe (Myford Speed 10) so that if I do get a dig in the belt slips rather than causing damage. Obviously not possible if you have a gear drive. Link to post Share on other sites More sharing options...
RMweb Premium Siberian Snooper Posted January 20, 2015 RMweb Premium Share Posted January 20, 2015 I agree Ozzy, sharp tools are safer than blunt ones as they need less effort to use and therefore do less damage than using a blunt one. Also less painfull when cutting yourself with them. Link to post Share on other sites More sharing options...
tender Posted January 20, 2015 Share Posted January 20, 2015 Have just stumbled across this thread and having recently bought a mini lathe and milling machine I wish I had done so earlier. Not had a chance to use either as yet as I'm waiting for the workshop to be elected in the garden. The lathe is a Chester super conquest which I think is a C2 variant and the mill is a arc euro trade SX2 plus with the DC motor wide bed. Can't wait to get to grips with both of them. Link to post Share on other sites More sharing options...
dajt Posted January 20, 2015 Share Posted January 20, 2015 Agreed tender, having a lathe (and milling machine if you can stretch to that) is great. Ozzy, both my machines came with guards, but I took them off too. I did start wearing safety glasses though as I have nearly been hit in the eye a few times. I broke an end mill not long ago too and the bit which flew off hit me in the chest, which was fine, but reinforced the idea that maybe I should be a bit careful. But back to that picture with the odd fitting on the cross slide, I still can't see it being for the safety guard as it just doesn't seem to put it in a useful place. The other clue would be if the machine will start with nothing in that fitting, then it isn't for the chuck guard. Sticking a DTI in there was an interesting idea. Link to post Share on other sites More sharing options...
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