Member postings for Ajohnw

I came across an amateur web site some time ago run by a person who loved stellite lathe tools. It was at the tail end of times when cheaper used machine tool and junk dealers had bins of used tool bits. He used to search through them with a magnet. The site was all good advice elsewhere so I have always had a hankering to try some. £27 for a 5/16 tool bit is a bit off putting though.

The comment about Tantung G and diamonds is just a comment off the web. True / False pass.

John

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Edited By John W1 on 02/06/2015 15:02:14

I'm not so sure about them being obsolete. There are variations on the same theme such as this one

**LINK**

I understand this one can only be ground with diamond. Its' fairly easy to buy Stellite tool bits and drills so I'd guess it still has it's applications. Trouble is that even a 5/16 tool bit works out expensive. I have no idea how expensive the tantung stuff is.

John

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Buck and Hickman sell them

**LINK**

John

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I suspect they are stellite drills. They can be used to drill hardened material and are said to work best when they get red hot. I've never used one hence said but it makes sense. I did see some stellite tool bits some time ago. Rather expensive.

John

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The aspect that needs thinking about when the rear end is adjusted to get the cone right is that all 3 nuts play a part. The end nut forces the spindle shoulder up against the bearings closing them up. The very rear ring positions the bearings. The other ring just fixes the stuff in place so can be left to last but each time an adjustment is made the other 2 need setting appropriately.

Using the tail stock helps because it's likely to thin any oil film other than probably the one in the cone and it will take up any play in the end ring's thread so it wont move when the other ring is tightened - we hope.

Ideally when the cone is positioned correctly there should be some drag. So after an adjustment with the tailstock applying pressure tighten the ring that keeps things in place, withdraw the tailstock and rotate by hand. If after getting this right the cut is still not adequate just make a very small marginal adjustment to the rear ring with the others loose and then tighten them up in the right order. This all assumes that the rear bearing pair are held tightly together otherwise it falls flat on it's face. Hopefully the tail stock pressure will take care of that. Oil films are measure in 1/10 thou, less in some cases. That should give an idea how much difference a turn of a ring can make.

If the cone bearing in the headstock has worn oval that will mess this up and probably mean that the set up needs to be run a little looser than ideal.

There is a fair chance after doing this that it will need doing again once things have settled down - tiny adjustments again. The viscosity of the oil drops a lot once a lathe is in use for a while and that will make a difference usually loosening bearings but on some with roller races etc they can actually tighten a little. The spindle expands due to heat.

John

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Edited By John W1 on 01/06/2015 23:07:54

Edited By John W1 on 01/06/2015 23:16:09

You might find that using the tailstock to push the spindle home will help getting the rear bearings set correctly. If your sure that your tailstock is on centre but a centre on it and press it into the morse 2 on the headstock spindle. The cone on the centre needs to be bigger than the morse 2 hole though.

John

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If it's not belt slip try tightening the rear nut carefully while checking that it doesn't add much drag by rotating the spindle. There should be some drag but very little. When you are pushing by hand your unlikely to displace the oil as much as a cut will. If you over do it you will find they get rather hot after say running at medium speed for 15-20min. It's a tricky area as lathe bearings may run rather hot on some machines - enough to warm the metal around them.

John

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I sold a sensitive DTI to some one after finding I had 2 some how or the other who had done just what I said and wanted to straighten it. I have also seen bent 3 morse milling collet holders in used machine tool sellers stock. Much depends on the power of the miller and the size of the cut and cutter it will take but by all means use what ever you see fit to use. Really there is no point fitting a collet holder that can take bigger cutters than the machine can usefully use.  A rough metric for that is a depth equal to the diameter with some care. Light cuts with face and fly cutters are a different matter.

John

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Edited By John W1 on 01/06/2015 15:15:04

You missed Schaublin Colin - sort of morse like. They chose to do that. Some of the various types will have been made for the same reason.

I'm not going to look at that lot, just general.

There are basically only 2 types - locking tapers such as morse and ones which don't or shouldn't. A rule that is sometimes used for not locking under any circumstances is a 30 degree half angle. With oil I would wonder about that in terms of pulling it out.

Morse on cutting tools should really use a tang on the end to ensure it doesn't slip hence it's wide use on drills. A draw bar can also help.

The various milling chucks are in one way or the other down to the the size of the machine particularly the size of it's spindle and the available motor power. The larger miller specific ones will generally lock into the spindle so the taper is more for accurate alignment. This can even extend to the collets used in them such as with clarkson auto lock. The cutters have a thread on the end so any slippage screws them in further until they can't go any further. The collet grip alone seems to be more popular these days but I don't know many people who have 5HP millers, not much idea how powerful they can get either.

I'm glad you realise that cutting torque matters. Just because some on sells a morse 1 ER collet holder doesn't mean it's a sensible thing to use. People have been known to bend even MT3 arbours on millers. Any morse fitting collet holder extends significantly out of the spindle - morse collets don't so less leverage is applied. You have a fairly light weight machine so personally I would be inclined to bear that in mind.

John

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Edited By John W1 on 01/06/2015 13:35:24

Not relating to this thread but I am happy with what I have at the moment. I don't mill that often and work is small so I cope. I will probably add an ER25 holder at some point when and if I need to. I also intend to make an adapter for screw on face cutters using the myford nose. I have a box of face cutters but so far haven't needed to use them.

John

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A long time since I had to worry about this area. This image from a post on here shows why it's a tricky thing to do

It's a two stage adjustment. The bearing position is set by the rings but bearing pre load is set by the nut on the end. So each time the bearing position is moved to pull the front cone in the nut on the end needs slackening off first. Bearing position adjusted and then the bearing pre load re applied. In this case preload mean zero of very low end float. Your not looking for zero clearance on the front cone just a very low number to suit the oil that is being used to lubricate it. Perhaps the best way to do that is to smear some oil on the spindle cone before assembling it. This is likely to be too much. Adjust and run the lathe and then adjust again. You will also probably have to adjust again later on as the oil film settles down over time - best done eventually after the lathe has been running for say 15min at a medium speed. Lathe bearings warm up due to friction which will also thin the oil. After adjustment check for problems at high speed.

Summary - the angular contact bearings can always give zero end float. They also have to position the cone so that it has a sensible oil film to run in when the lathe has warmed up. It wont be possible to do this quickly. People might also find that the cone is too tight really before the lathe has warmed up. It's a matter of compromise if that happens.

Personally on these lathes I think it is worth checking the condition of the angular contact bearings as the adjustment is so easy to mess up. They are designed to be used in pairs with each one the right way round and like all bearings shouldn't have any play when not loaded. Some probably doesn't hurt at all given the way Myford use them but any jitter / ripple when they are pressed home and rotated is bad news. The cone can wear in odd ways as well if the lathe has been used with the bearings incorrectly adjusted - too loose in other words and lubrication is very important.

John

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I think Jason hit the nose on the head when he suggested morse collets. I have a dore westbury. It's morse 2 in a hefty spindle and that type of collet is the best option for a lot of work. I bought suitable metric and imperial collets because I like to buy bargains when they crop up.

I think you will find that standard shank diameters in your sizes are 3,4,5,6 and 8mm diameter. The actual cutting diameters at these sizes will vary. You will find that it's possible for instance to get 3mm cutters with a 6mm shank. The other smaller sizes of shank are more likely to be found on solid carbide cutters. You could get a better idea of the variations in this area by browsing ArcEuro's pages. They for instance only sell cutters with 6,10 and 12mm dia shanks.

ER collet holders sound very attractive but are just as much pain to change as a morse collet when a change is needed. I am not aware of any 1 morse versions anyway. I do use an ER16 holder at times because of the size of the quill on my miller - they give more reach from the quill and also give me a better view of what is going on. The parallel shank ones are often used on "big" milling machines for the same reasons. My DW isn't big but is based on a Myford lathe spindle nose.

John

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I think that's kindly put Ian. Looks like the Cub has sold. Not surprisingly really. Every now and again I get the urge to really refurb something like a Cub but have to slap my wrists and say no and never look at the add again. Trouble is there is something nice about geared head real lathes and few are that small.

John

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I think it would be worth asking what heavy wear is on the lead screws and if the dials move axially as well ?

My Mk1 had around 0.015in play which I would say isn't bad with no axial movement of the dials at all. I doubt if it was much better than that from "new".

ACME taps should come in 3's just like ordinary taps except they also step up in size. Even then they aren't the easiest of things to cut threads with. I suppose some might be extremely long to achieve the same thing. I'd be very careful if i found I needed to buy one as it might turn out to be unusable.

Personally I wouldn't dream of using delrin. I'd rip into shreds in no time as I set the slides rather tightly. What I should do but haven't is remove the lead screws and set the gib strips up by pushing by hand. Tightening until I feel some resistance.

I too would screw cut replacement nuts if needed in bronze. It might be possible to use a tap if a slightly over deep square thread is cut first. It might be possible to sort out some cnc lead screws and nuts as an alternative.

John

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I suspect the Churchill Cub advertised on here was a much better option at £250 and probably even worth spending some money on. A real lathe rather than ....... I am not sure what to call the exe..

John

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I did more or less the same thing with my Boxford Les. I started on the basis of wondering why Boxford used a certain size of gear for packing another gear and found that it could give some metric threads that were adequately accurate for many things. I then used that set up to estimate another. This is the result

I did this with a spread sheet but once compound trains are needed that gets tough. Some people use the above fairly regularly but many people insist on having a 127 gear and don't realise that a few microns error doesn't really matter and that lathe screw cutting isn't fantastically accurate anyway. Screws generally aren't anyway which is why nuts are so thin.

I looked for the software again because of an interest in cutting DP and Mod worms. My Boxford came with a fair selection of spare change wheels to use with the gearbox and I suspect who ever bought them had their reasons. The software on lathes co can sort out what they can do pretty rapidly for any pitch I am interested in. One odd fact on worms is that 8TPI is pretty close to 1 Mod, around 0.001 in error. I suspect a bit of lapping would correct the worm rapidly but I could do with a coarser pitch really.

John

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Edited By John Woodhouse on 28/05/2015 16:42:55

The wayback machine often doesn't retain executables but it has in this case. I've let him know via email.

Not the best of programs really for lathes with a screw cutting gearbox but a lot better than nothing. Personally I feel it should work with pitches rather than TPI. All a gearbox does is alter the effective pitch of the lead screw - usually via a couple of gears. On the other hand it's not too difficult to work out the ratio's from the same numbers.

John

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I did have a copy of these on my PC but they must have been missed when I upgraded my machine. The software sorts through available gears to select the best match for any pitch thread.

Tony had a problem with his web site. He has found NthreadsP but not BoxftrhreadP the version for lathes with a screw cutting gearbox. He is currently appealing for a copy of this one to restore his web site.

If some one has a copy could they send it to him. Contact details are on his web site.

John

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Leave the parts in paraffin for a few days. It will soften gunk sufficiently to allow it to be brushed off with a tooth brush.

You could also use Gunk engine cleaner but that is intended to be washed off with water which might lead to rust.

John

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