Rear mounting parting-off tools

[andy mulhollandParticipant @andymulholland30577]

 Operating from the front toolpopsts should in fact be more rigid because all is being pushed down onto the bed. At the back it’s all being lifted and any slack will be magnified.

 

           lifted this from an earlier post and was wondering if it is  actually right. the cutting forces will have an equal and opposite reaction which will tend to do just the opposite, ie lifting at front and pushing down at back. the best way i can explain this is to imagine trying to hold the tool in position by hand and think of the force and direction of it you would have to exert.  add this to the fact that you have more sliding surfaces under a front mounted tool makes for possibly a less rigid set up than a tool mounted directly on the cross slide. there can surley be no doubt that the rear mount does work well on a light lathe. even if my above reasoning is flawed  it did solve my parting off nightmare shifting to a rear mount.

 

            regards all andy

[Clive FosterParticipant @clivefoster55965]

All this geometrical argument about tool fulcrums and tool lift altering depth of cut is very interesting but it ignores the fundamental causes namely backlash and the forces on the feed screw.

 

 I think everyone agrees that serious parting off trouble begins with the work piece effectively climbing over the tool and trying to draw it deeper into cut.  Whether the climb over effect is due to spindle play, work piece deflection or tool deflection is immaterial as the effect is, for all practical purposes the same.

 

Consider a lathe with the conventional “push from the front” cross slide feed screw.

With a rear mounted tool the screw is pulling the tool into the work.  The screw is in tension, all the play in the bearings and nut mount is pulled out so if the tool is to be pulled deeper into cut by the climb over effect it’s necessary to stretch the feed screw.  An unlikely scenario as the feed screw on even the smallest, wimpiest lathe has enormous tensile strength.  Thus the increased depth of cut is generated solely by the climb over effect with no positive feedback to make it larger so there is a good chance of the tool cutting through and the work piece settling back to where it should be.

 

Now with a front mount the feed screw is pushing the tool into the work.  All the backlash and clearances are on the opposite side of the thread and thrust bearings to the working forces.  Being in compression the relatively slender feed screw will try to run away from the load by bowing and shuffling sideways in nut and mounting collar clearances.  A tendency not helped by the offset unbalanced forces inherent to the helical nature of the screw.  Effectively you have a spring, a very stiff spring, pushing the tool into the work.  Now when the work piece does its climb over trick it is able to draw the slide forward through the backlash region and the spring deflection region, the springy bit actually helps the effect along.  The cut depth increases pretty much instantly by getting on for 30 thou or even more on a well worn lathe.  The lathe has no chance of cutting through this, climb over continues until everything comes to a grinding halt with broken tool ruined job and considerable Workshop Esperanto loosely translatable as “oh dear, oh tut-tut, things have gone wrong”.

 

It doesn’t help the front  mounted tool case that its mounted on the top slide giving an extra set of dovetail slides to reduce rigidity relative to the rear mount case. 

 

Clive 

 

[chris stephensParticipant @chrisstephens63393]

Hi Guys,

At last someone has come up with a reasonable argument, well done Clive. 

Sorry  Dave H., but if your lathe has that much flex next time buy one made from METAL not plasticene.. 

It all boils down to; if it works for you then great. If it doesn’t, then try something else till it does, 

Ain’t it great to live in a democracy. The day there is only one way to do something, is the day to start  the taking up cake decorating.

chris stephens

[CirclipParticipant @circlip]

One of Mark Twains’ I think,

 

  “It is better for people to think one is a fool than open ones mouth an dispell ALL doubt”.

 

  Regards  Ian.

[John HaineParticipant @johnhaine32865]

Um, I don’t get Clive’s argument here.  Yes, if you are pushing the tool in and the cutting forces pull the tool into the work then any backlash in the feedscrew & nut means that there is nothing resisting the pull.  But equally if you are pulling the tool in and the cutting force is also pulling the tool in, then again any backlash also means that there is nothing to resist it.

[mgjParticipant @mgj]

David – regrettably your resultants are incorrect..

 

My point was that if the tool is high at the front, or below centre at the back then there is a more or less vertical component which takes the tip into thicker metal so the depth of cut has to increase. And vice versa.  Also your drawing ignores the component or vector generated by back rake.

 

Sorry, but the drawing is rather too simplistic to be of much help, even if it has been published in similar form many times.Sorry, but I like drawings with vectors and tedious thngs like sin alpha and cos theta on them. Those, as an engineer, I relate to when it comes to working out what is going on.  Big hand small map arrows – bit less happy about.

 

As for backlash  – being favourable at the back. I have a little difficulty with that. You are pulling the work in under tension on the back edge of the thread. The job rides up, or by some other means an inwards component is generated (which is what is going to cause the jam up) and this screw is to remain under tension?

 

When there is a space (backlash/tolerance)into which the feed nut can move?

 

 

In short, all the backlash and spaces are on the same side on the nut – relative to the direction of movement  of the cross slide – when the jam up occurs. Front or back.

 

In both cases the entrance of the tool is resisted and in both cases that will take up all backlash before cutting begins. Then some inwards component is required to overcome that resistance and then the load (cut) will increase such that the inward component drags the tool inwards and into the backlash and into the work unfortunately too..

 

In other words you are not going to get a jam up until the tension or compression have been released. Something has to act (faster or) in addition to that compression or tension, because while that tension or compression was being applied the tool was cutting OK.

 

As in tool is cutting OK, – something happens (which doesn’t include increasing the cut manually), and it is often independent of radius) – conditions change -tool increases cut –  tool jams. It doesn’t suddenly jam because it feels like it. And it can most certainly jam at the back as well as front. And that is the problem with a lot of these arguments- they assume that it won’t jam at the back. When it can.  So, mathematically, or  in their mechanics, there is something wrong with them – by definition.

So tension and backlash and whirling lines seem unlikely as explanations

 

 I prefer chip jamming in the slot and back rake, because removing the latter reduces the inwards component, and lowering the centre of the cut introduces an actual outward component (vector) so it isn’t going to pull in unless one does something really intellectual. Actually Mr Sandvik also rather likes that explanation too, and thats one of the reasons he designed his tips that way – so he says in his blurb. So forgive me if I stay with it.

 

But, only too pleased to listen to other possibilities – I’m sure they will explain to me why I don’t have a problem parting off at  the front.

 

Were these gentlemen were right I would get a front jam every time? In fact, I used to. I then changed, and now despite an extra set of dovetails (QCTP) on top of my topslide dovetails, I can part off faster, with much deeper cuts, in narrower slots, and on one lathe, with a degree of tool overhang which is greater than the centre height of many modellers lathes. And it doesn’t jam. Not once.

 

And that is not surprising. I am using the most rigid part of the lathe, I am pressing onto the bed and taking up all the slack I can, my spring is as short as possible and I have a tool geometry which resists being pulled in so the nut will not get drawn forwards into the backlash and increase the cut suddenly and uncontrollably, and there is feedback in the form of feel. 

 

So thats why I REALLY REALLY like the Sandvik argument. They have measured forces etc, and they REALLY REALLY know what they are on about. They are not guessing. I find that quite nice, especially when it is borne out in practice

 

 

Of fools and things. I always thought it was Thomas Jefferson, but I could be wrong. The actual quotation is “Wiser to remain silent and be thought a fool, than to speak and remove all doubt.  More elegant that way? 

 

Edited By meyrick griffith-jones on 16/10/2009 20:08:03

[chris stephensParticipant @chrisstephens63393]

Hi Meyrick,

We mustn’t go on meeting like this, people will begin to suspect.

As usual you sum up matters nicely. Nice to hear sense not dogma, for once.

Regarding Sandvik tips, I heard a story that goes something like; When the replacable parting tool tips were first introduced by, possibly or not, Iscar, Sandvik tried to come up with one of there own. This did not work and they had to wait till the patent ran out to copy a tip shape that did.Certainly the Iscar parting tips that I use work very well, but I am running out and the new styles are different, bo hoo! 

 No slur intended on Sandvik, I know they make quality products. but they do seem more interested in industry than home use. Some other makers, make tips that are ideal for home use, Sumitomo for instance, even if they don’t like selling to individuals. Anyone who has used their T1200a titanium carbide Cermet tips knows what I am talking about. Just had a look on their site and could not find T1200a, so it looks like you folks will never get to find out how good they were.

I suppose I shall have stick to my Tangential tools, for a good finish.

chris stephens

[mgjParticipant @mgj]

Well hell I hope its sense. Its just basic mechanics  and levers. You have to be able to look at forces and work out vectors and resultants. It don’t take the brains of an archbishop.

 

Engineering day 1 after finding where the lecture hall is. Take moments about point a or b, set to zero and work out the load at… (oops, have I got the signs right?)

 

If you can’t do that sort of thing and you want to work out the loadings in a space frame or suspension member, or the torque reaction in a set of brakes……….. it can get a bit dramatic on circuit.. and very expensive if you are running a project where items run at £250k per unit. (engine and gearbox)

 

Tips – I didn’t know that anyone actually make tips for home use. I must admit I had assumed that all were for industry, and to be fair, most of the tips that modellers use are industrial tips because most conform to the ISO standard. All the SCLCR SDJCR and variants are. And so far as I know most of the milling shapes are standard too.The triangular PK… are a rather old fashioned tip now. The Glanze ones – slightly twisted rectangular ones certainly are.

 

Having said that I can well believe that tip geometry between makers varies and some will suit the lower powered machines that we go in for. SECO I personally find much better than Sandvik on the Myford, though they show no advantage on the 6″ Chinaman with rather more horses available.  However the Sandvik parting tips are better than the SECO (for me anyway).

 

So if you tell me that Sumitomo are excellent  I’m open to suggestion. 1200a will be one of their grades of carbide? Or is it actually a tip designation? If its a tip description to fit a standard holder then it should sound like CCMT……04/08 and the 1200 will be the grade.  Might not be an ISO shape of course. Stellram make brilliant boring bars, all pre drilled down the centre for coolant, and I bught a set. Best cutting things you ever came across, and the tips last for ever even in cast iron. – not an ISO shape though, so you have to go back to Stellram for tips – if you live long enough to have to.

 

 

I bet those tangetial things are darned good. They look as if they should be, though without anything to carry a download, I wonder if those holders are good on interrupted cuts where there is a shock load. If I’d heard about them, I’d have gone for them, but I went for tips. Given that a box of tips costs the same as a Eccentric holder, the HSS is a pretty good way forward IMO, except for parting where tipped tooling for me offers such a clear advantage over ground up tools that its worth paying the money. 

 

 

 

 

[chris stephensParticipant @chrisstephens63393]

Hi Meyrick,

This is becoming a bit two sided.

The Sumitomo tips I mentioned are industrial but they are capable of taking very fine cuts, something “industrial” tips will often not do. As they are ‘sharp’ they can be used on low power machines, like a lot of hobbyists have. They cut so remarkably well that they leave an almost chrome like finish on steel, even on shallow final sizing cuts, another reason why they are good for hobbyists, with the right tip radius and chip breaker, of course.

T1200a is the material they are made from which is a “cermet” a ceramic titanium carbide not tungsten carbide.

Tangentials can be made at home you know, no need to ruin the balance of payments deficit any more than necessary. See this months MEW, but I would scale it up to use 1/4″ HSS. As for interrupted cuts, they work just fine the worst that could happen is they slip. Great thing about them on a lathe without QC holders is that you can centre height them with ease. The other great thing is once made the cost of cutters is negligible as you don’t waste HSS too much, just take a smidgeon of the end each time.

As I mentioned earlier I have three parting tools in QC holders, the standard Bantam Dickson type1/8″ wide(or is it 5/32? horribly expensive to replace), this has a vee ground in its top, this I have used to part off  2 1/2″ alloy steel under power.. The second is an Iscar 2mm wide great for tough stuff, used with a drop feed of CT90, but will only cut about 12-15mm deep. the third is an Eclipse 1/16″ x 5/16″ parting tool holder which is in turn held in an angled sub base which gives about 6-7 degrees of rake. This sweet little tool only has a max depth of cut of about 8mm (recommended) but can be used to at least 10mm, this may not sound much but is used quite frequently, made it so it will fit the Myford too. This is very cheap to run as you only have to grind the front, when it needs a touch up.

HSS, if you can sharpen it well, is a great money saver. Down side is that metal removal rates are reduced, but then we are hobbyists not every second counts clock watching industrialists. A well sharpened HSS tool can give a superior finish, especially on shallow cuts when doing final sizing. I don’t know about you but I would not use anything else when “chasing tenths” on the rare occasions when it is called for.

chris stephens

[mgjParticipant @mgj]

I agree – you must be an insomniac BTW.

 

I suspect that a lot of my parting woes have been caused by using too much back rake. Then you create that inwards component and then you are in trouble.  I tended to use the maximum rake recommended by Tubal Cain, and I should have thought about it and reduced  rake. Now of course I’m using zero rake. I have the 3/32 blades and a 1/16 blade but now they tend to be used for chamfering and the odd rounded groove at the end of screw threads – because the Q cut is so good.

 

II’l look at Sumitomo – good hint. Sandvik are good. I got an especially good deal on turning tips, because i cleared a place out of CCMT-06/09 tips of discontinued grades for steel. So that made them especially good, but you are right – they are not great for shaving cuts. I wish I could say I can hit diameter from a mile off.

 

Well I can – but sometimes its not quite the right one!

[chris stephensParticipant @chrisstephens63393]

Hi Meyrick and sorry to the rest of you guys,

If your top rake (or is that back rake/) is ground into the blade you will get trouble, but if your top rake is created by tilting the whole tool you should have less  trouble. On the 1/16″ blade, I have a large(ish) amount of front clearance giving quite a sharp edge. I also grind it square, to prevent any tendency to bend the narrow blade during a cut.  Any down ward  tool deflection would cause the tool to come out of engagement not a jam up, bearing in mind that you have limited depth of cut, implying small diameter work. The same deflection on large diameter work would keep the tool in contact with the work.

 Could it be that jams occur when using a fairly blunt tool, the tool deflects down, then springs back suddenly increasing the cut. Could the answer be to use a sharp tool and power feed, this way the load is relatively constant so spring would be maintained? No sudden jerks to cause problems.

I wonder if people have more jams with large material compared to small. I feel a survey coming on. Also, how much blade do people have protruding ?

Please don’t take my comments on Sumitomo tips as a recommendation, as I now have no experience of their current products. Just because they will say the new ones are an improvement, the cynic in me says “prove it”. Due to designation changes I would not even know which ones to opt for. I don’t want the Rep to come here, that would remove any credibility that I might have.

One of the reasons why shaving cuts are not accurate is that you have too thick an oil/grease on your cross slide lead screw. The theory goes something like; on a heavy cut all backlash is taken up, but on shallow or light cuts there is not enough equal and opposite to compress the lube, just the weight of cross slide. The oil acts rather like a damper. One answer might be to have a cross slide lock, which you can add friction to help compress the oil film, use a light oil. How does that sound? You are the Engineer, I’m just a knob  twister!  “Stop ye tittering at the back, there”. to quote Frankie Howard.

To quote someone again “I can make any size, just hope and pray it’s the one I want” 

chris stephens

[chris stephensParticipant @chrisstephens63393]

Ignore the posting above, I can’t delete it
Posted by chris stephens on 17/10/2009 13:52:08:
Hi Meyrick and sorry to the rest of you guys,

If your top rake (or is that back rake/) is ground into the blade you will get trouble, but if your top rake is created by tilting the whole tool you should have less  trouble. On the 1/16″ blade, I have a large(ish) amount of front clearance giving quite a sharp edge. I also grind it square, to prevent any tendency to bend the narrow blade during a cut.  Any down ward  tool deflection would cause the tool to come out of engagement not a jam up, bearing in mind that you have limited depth of cut, implying small diameter work. The same deflection on large diameter work would keep the tool in contact with the work.

 Could it be that jams occur when using a fairly blunt tool, the tool deflects down, then springs back suddenly increasing the cut. Could the answer be to use a sharp tool and power feed, this way the load is relatively constant so spring would be maintained? No sudden jerks to cause problems.

I wonder if people have more jams with large material compared to small. I feel a survey coming on. Also, how much blade do people have protruding ?

Please don’t take my comments on Sumitomo tips as a recommendation, as I now have no experience of their current products. Just because they will say the new ones are an improvement, the cynic in me says “prove it”. Due to designation changes I would not even know which ones to opt for. I don’t want the Rep to come here, that would remove any credibility that I might have.

One of the reasons why shaving cuts are not accurate is that you have too thick an oil/grease on your cross slide lead screw. The theory goes something like; on a heavy cut all backlash is taken up, but on shallow or light cuts there is not enough equal and opposite to compress the lube, just the weight of cross slide. The oil acts rather like a damper. One answer might be to have a cross slide lock, which you can add friction to help compress the oil film, use a light oil. How does that sound? You are the Engineer, I’m just a knob  twister!  “Titter ye not.”. to quote Frankie Howard.

To quote someone again “I can make any size, just hope and pray it’s the one I want” 

chris stephens

 PS realized my mis-quote hence changes. Why can’t I edit when using Google Chrome, but I can when posting from Internet Explorer?

Edited By chris stephens on 17/10/2009 14:55:20

Edited By chris stephens on 17/10/2009 14:58:11

[mgjParticipant @mgj]

Blunt tools when you push in, and suddenly it grabs, backlash- somewhere for it to grab into, which it needs, and inwards vectors due to rake and geometry, and tool positioning wrt centre height (use DHs diagram to visualise and you can see that centre height is crucial as to whether depth of cut increases or decreases.

 

One of the thing we haven’t considered is tool rigidity or spring. We have assumed its rigid. The smaller parting off tool may not be, and spring in the tool could well contribute or be an initiator. If you look at the tipped tools they are massively rigid- the baby Glanze in nearly an inch deep for a 2mm wide cut. The Sandvik blade about 1.25″ deep.

 

My guess is that much of this front bad, back OK has to do with backlash. The back toolpost is often given as a remedy for a worn lathe – bearings allow job to ride up. No, because it can still jam at the back. (as it should if the geometry is as I suggest.) Probably with the the smaller lathes not having roller thrusts in the leadscrew drive, (the Myford Connoisseur has so must get the mod at MEX) and the fact that at the front one is operating on a worn section of the FEEDSCREW, and there is most of the answer. I know the Myford got much better behaved after 23 years on one feedscrew and it got a treat in the form of a new feed nut and screw.

 

Constant load I like – that sounds good, because backing off leaves the x slide floating in the backlash and not under control for a second or so. And tools of low rake. 

 

Oil or float will do it. – final diameters. I have always taken a little while to set x slide gibs to ensure they are a touch firmer than many might like, because that introduces greater consistency. At a price, because the feed nut does wear a little faster. But then they are quite easy to make. Acme tap and a chunk of bronze, or else just send to Myford. One screw and nut in 23 years is hardly high maintenance! 

 

However, whether the float is in the feed nut, or the vertical movement of the saddle and x slide downwards I don’t know. However, with slightly firmer gibs you don’t have to know!

 

I’ll try my local tool people and see if I can blag a Sumitomo tip – just to try.

[chris stephensParticipant @chrisstephens63393]

Hi Meyrick,

Where is everybody else, thought someone would chime in by now.

 

The new Myfords are quite nice to use, certainly that was the  reason I put variable speed on mine. Can’t quite understand why their Metric lathe still has an imperial gearbox. No, wait I can, cost!

I was using one at the last couple of MEX at Ascot on the SMEE stand, but I doubt that I shall this year. Had I been going to demonstrate, you could have tried a Tangential tool, might have made you drop everything to make one yourself. Not demonstrating ‘cos of “day time job” and I am getting bored with metal munching. Going to the Midlands show tomorrow, to try and be inspired again.

 

When you say blag a tip, you do realize that they make hundreds upon hundreds of different tips. Most will be no more useful to a Myford user than anybody elses. On  the 7X12 lathe group, they seem to recommend tips designed for Aluminium (no make in particular), these I imagine have more rake than ones for steel and are therefore sharper. This would mean they cut rather than “plastic deform” or whatever the phase is.

chris stephens

 

[mgjParticipant @mgj]

No – I was going to look through the catalogue and find something appropriate. I was really thinking of a parting tip in the fine finish low feed range.

 

I don’t mind a lot of rake on a knife tool – quite like it in fact . I think I have a total of 25 deg compound angle on the Quorned HSS ones, and they cut like I don’t know what. Well they would with that rake pulling them forwards. The Myford loves them and will take 1/2″ on dia in one cut at 600 RPM. (220M07) Bit interesting in brass and bronze though.(backlash, grabbing, difficult to control etc) – gets a bit bouncy.

[chris stephensParticipant @chrisstephens63393]

Just the two of us then,

The tips I was using were, I think, TCMT 090202NFP in  T1200A. also CCMT 09T302 NFP again in T1200A. NFP is described as “bumpy chip breaker NFP for finishing with small depth of cut and fine finishing” . Mind you small depth of cut in industry might be massive in a hobby situation. The 02 tip rad. might seem a bit small, but the reasoning is, I believe, less strain when cutting therefore less likelyhood of work moving away from the tool. The book says DoC is in the range 1mm down to bu**er all, with a feed rate of virtually zero to 0.2 mm/rev. Surface speed is 80-300M/min. Oh, and never stop the cut with the tool in contact with the work, sure way to chip a T1200A, very, very hard but brittle as a biscuit.

Good luck with the search. I would say let me know what the new numbers are, even if I wont be buying any.

chris stephens

[mgjParticipant @mgj]

Chris – tip radius will have quite a lot to do with it. They always say that your final cut should never be less than the tip radius, to stop rubbing. Or so I was told. I don’t think Sandvik actually do .2mm tips. .4 and .8 I have.

 

80-300m per minute. I’m not sure my machinery can get to that speed, and certainly not without spraying coolant everywhere.

 

However thanks for that – I have noted the tip numbers.  I’ll see what i can do, because sometimes a sharp corner is quite helpful.

[chris stephensParticipant @chrisstephens63393]

Fear not, I have used them on my Bantam which has a top speed of a mighty 800RPM! Oh and I used them dry.

You are welcome, see you in the ether.

chris stephens

PS I was machining the cast iron table, for a GHT Pillar tool, and was not happy with finish. I was getting that mottled effect, anyway I dug out a used rhomboid tip and used the only sharp corner left, the 80 degree one, and it cut great.  Note to self, after five years it’s about time to finish it.

[Mark Smith 3Participant @marksmith3]

I have read with great interest and not a lot of understanding this whole thread; am I confused? of course I am, I am a shoe maker with pretentions of being an model engineer.

I find parting off to be a chore I approach with fear as I have an ancient Barns Lathe designed about 1880 and manufactured around 1930. It has a tiny spindle, poured bearings and an overhang of the chuck of 7″ from the head stock to the jaws. Now, when I get a dig in the whole chuck and spindle lifts very high and the flat belt is thrown off its pulley. The bearings seem ok so long as I check the screws for tightness on the bearing cap, but it still does it. I have found that copious quantities of wd40 helps which also keeps the bed from rusting. I would like to try a rear mounted tool post but there is simply nowhere to mount it as it has no T slots on the cross slide. Woe is me I think I need a new lathe, what think ye?

Mark

[Geoff SheppardParticipant @geoffsheppard46476]

I carried out quite a few experiments with a variety of parting tool systems for an article I prepared for MEW quite a few years ago now. I ended up acquiring/making some eight different forms of holder and several dozen blades. One of the more effective (and least expensive) was the holder described by the late Len Mason in his book “Using the Small Lathe”. This consists of two plates, between which is sandwiched a short length of hacksaw blade ground to the correct form. Some of the nicest to use were the small Churchill blades which produce a thin groove.

Quite definitely, using the Myford Super 7, an improvement was made by going to a rear toolpost and the ultimate system was a Q Cut from Greenwood mounted directly into a rear QCTP. For use with steel, though, I have found it necessary to provide a continuous drip of coolant (I use neat cutting oil) right on to the tip of the insert. This seems to keep the swarf moving away and prevents overheating. Power cross-feed ensures a continuous cut and prevents rubbing which, on some materials is fatal because of the work-hardening tendencies.

Hope this helps

 

Geoff

[Peter G. ShawParticipant @peterg-shaw75338]

Geoff Shepherd mentions Len Mason’s parting tool system using two plates and a bit of hacksaw blade.

I tried this, and didn’t have much success – my blades kept breaking.

 

What I did do though, was to use the same idea but instead of hacksaw blades use an old 4″ file ground down to a thickness of 1.8mm, (1.8mm because that’s where it ended up being successful!)  and a blade length of about 10 to 12mm. Using slowest feed and plenty lubrication, It worked perfectly despite the fact that the clamping device was rather poorly made.

 

Incidently, it’s used as a front mounted cutter working the right way up.

 

Regards,

 

Peter G. Shaw

[calder percival 1Participant @calderpercival1]

the rear toolpost originally came to counter the split cap bearings found in most model engineers lathes in the early days the effect was to thrust the weight of cut into the casting and not against the bolts that held the bearing caps down. You will find that a keen tool with the correct rake and set ever so slightly below centre will part clearly all the time coolant is essential! i have just parted off two rings 4″ diameter with hand feed tonight in b.m.s for backplates on my traction engine hubs a little care goes a long way.

[KWILParticipant @kwil]

All very interesting, in the end its what works for you.  Personally I am a Sandvik/Iscar person, front mounted on all sizes of lathe, when used with fluid the wet stuff stays on the top surface where it is wanted!

[DuncParticipant @dunc]

Regarding the use the (front) toolpost but run the lathe in reverse…

Here is another commentary

http://email.villagepress.com/pub/HSM/20091211/20091211.html

[NobbyParticipant @nobby]

Hi Tony

I part off from the back as Michaels says it digs out . The reason is because as you wind in from the back the backlash does not come in as the nut pushing on the front of the thread.and no movement can accour. Ps this may have been said already

Regards Nobby

[Author]

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