Lathe improvements?

[HopperParticipant @hopper]

Posted by Niels Abildgaard on 08/01/2021 19:51:35:

Edited By Niels Abildgaard on 08/01/2021 19:56:50

For goodness sakes! Mount that lathe and massive solid granite base block on a strong work bench before you hurt yourself.

That spindly Ikea piece of living room furniture was never designed to take that weight safely. It could collapse any minute now.

You are a danger to yourself and those in the apartment below you.

[Ady1Participant @ady1]

Some next level stuff Niels, very interesting

Hopper is right btw, buy a nice strong bench today and move that lathe before something bad happens

edit: best to do it before parting off begins

Edited By Ady1 on 09/01/2021 09:20:29

[Niels AbildgaardParticipant @nielsabildgaard33719]

Table was tested by two neigbours and their child rocking sideward in unison.Looked funny and no problem .Human mass 1.5 times diabas plus lathe.There is no neigbours underneath unless chineese count as neigbours.

It was much more alarming that the roller cages rubbed the bores.I filed them down and have no ultrasonic bath.

First five minutes sounded awfull but now they are OK and power falls steady and is now 80W down from about 200 yeasterday.temperature around 37 degree and I have put a chair and another miserable and cheap secondhand table as first line of defense against collapse.

I think world is quite a pleasant place for old men.

Lathe ,diabas and table are united by two M12 all-threads.

Edited By Niels Abildgaard on 09/01/2021 09:47:55

[Niels AbildgaardParticipant @nielsabildgaard33719]

Something crazy happened.One wet morning two lathes came up for sale.

First was a 920 with no equipement .no history and to expensive.

I told him I would call back later but sell if he could

The second was a 250 made and labelled from Weiss .One owner everthig OK.

I asked for half an hour to clear how to get money .That is problematic due to Covid etc.

I phoned back, got his account number and transfered the money and he offered to drive it to me 150 km north.

When we unloaded it took five seconds to reconize that I had contacted the wrong seller second time so now I have a much to expensive 920 .

Funny thing is I like it more and more and have ,guess what; designed a new bigger spindle.

It is maybe of interest to compare tool induced deflection of this hypothetical 920 Mega spindle with a standard Boxford for same tool force,whatever that is.

A sketch of battlefield.

[Ady1Participant @ady1]

Re: your narrow chuck work

No-one mentioned it but a recent ebay sale had the amazingly rare drummond 4jaw which was specially developed for large work bigger than the chuck itself, to fit into the gap

The jaws appear to be quite small compared to the chuck body

Edited By Ady1 on 30/03/2021 10:59:55

[Niels AbildgaardParticipant @nielsabildgaard33719]

From tool point to first bearing there is 120mm on my proposed and 150mm on the Boxford.

 

Between the bearing there are 130 and 180mm

 

Spindle bending stiffness between bearing is fourth power of diameters.

Mega 920 is thus 6.2 power 4 minus 4.5 power 4 equal to 1478 minus 410 equal to 1068

Boxford is 3.6 power 4 minus 1.9 power four giving 168 minus13 equals 155 in same units.

 

A unit tool load force on the Box gives a bending moment on front bearing that is 25%more than Mega920 .

The angular deformation on front bearing depends on bending stiffnes and that was 1068 /155 equal to and on the length ratio squared tha is 180/130 squared or ca 1.91

Let the transverse deflection at tool point for the Mean920 be one for a given load.

The corresponding for Boxford is thus 1.25*6.9*1.91*1.25 equal 27 times more.

Chatter come easy and faster on Boxers

 

Edited By Niels Abildgaard on 30/03/2021 11:11:01

Edited By Niels Abildgaard on 30/03/2021 11:12:55

Edited By Niels Abildgaard on 30/03/2021 11:24:41

[Niels AbildgaardParticipant @nielsabildgaard33719]

Posted by Ady1 on 30/03/2021 10:56:01:

Re: your narrow chuck work

No-one mentioned it but a recent ebay sale had the amazingly rare drummond 4jaw which was specially developed for large work bigger than the chuck itself, to fit into the gap

The jaws appear to be quite small compared to the chuck body

Edited By Ady1 on 30/03/2021 10:59:55

A new chinese precission version were just the thing for old toads.

[HopperParticipant @hopper]

Posted by Ady1 on 30/03/2021 10:56:01:

Re: your narrow chuck work

No-one mentioned it but a recent ebay sale had the amazingly rare drummond 4jaw which was specially developed for large work bigger than the chuck itself, to fit into the gap

The jaws appear to be quite small compared to the chuck body

Edited By Ady1 on 30/03/2021 10:59:55

Is that the standard M-Type 4jaw or something special? I have the regular 4 jaw on my Drummond and it is a nice slim body but never thought about the gap relationship.

[Ady1Participant @ady1]

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Hopper on 30/03/2021 11:54:31:

Posted by Ady1 on 30/03/2021 10:56:01:

Re: your narrow chuck work

No-one mentioned it but a recent ebay sale had the amazingly rare drummond 4jaw which was specially developed for large work bigger than the chuck itself, to fit into the gap

The jaws appear to be quite small compared to the chuck body

Edited By Ady1 on 30/03/2021 10:59:55

Is that the standard M-Type 4jaw or something special? I have the regular 4 jaw on my Drummond and it is a nice slim body but never thought about the gap relationship.

.

It looks [in Ady’s posted advert] remarkably like what became the Myford special that Burnerd produced

… and the text about the reversible jaws seems to describe the style which became the de-facto standard.

I wonder what “common pattern” Drummond was using as its benchmark

MichaelG.

[Niels AbildgaardParticipant @nielsabildgaard33719]

The Mega 920 versus Boxford stiffness comparison from 30 of march can maybeebe used again.

Many years ago I succeded in parting 100mm mild steel without trouble on my Boxford.

It is tempting to make a new spindle for my new 920 without any modification to headstock.

Distance from cutting point to first bearing is 110mm on the 920 and 140 on Box.

Bearing interdistance is 140 and190mm

Soft part of Box spindle is 36mm/19mm and the new 920 spindle is 40mm/28mm that is Box bends 1.26 times 920 .

length between bearings makes box 1.84 times more sensitive.

thecutting load makes spindle bending moment 1.28 higher for the Box.

For same cutting load the working point evasive movement will be 1,28 times 1.26 times 1.84 times 1.28 equals 3.8 less for the new two bearing 32908 920 spindle compared to my old boxford that was not bad.

I have just saved my self a lot of trouble.

[Niels AbildgaardParticipant @nielsabildgaard33719]

My son has bougth a Quantum 310 910 lathe and I can have my beloved Weiss Mashinery 250 750 with Morsecone 4 back.That was up to now my best bid for an old geezer ideal lathe.

In the meantime I have worked on my Maximum Capacity-Minimum Volume version of Weiss 180/210 cheap as dirt lathe.

It consist of bed and sled from a 180/300 and headstock from a 210/400 and a 48mm bore spindle in some slim conical roller bearings.

The screwcutting and feeding arrangement has cost me headache but I am sure it can be handled now.Screwcutting from 0,4 to 2mm pitch comes easy and a single fine feed will do until I can make an Adjust as You cut version.

It needs to stop immiately when spindle does.

 

Edited By Niels Abildgaard on 24/08/2021 21:24:32

[Niels AbildgaardParticipant @nielsabildgaard33719]

The gear wheels scheme is illustrated here

The fine feed via 80 teeth on spindle

First Compound 17/80

Second Compound 15/84

Leadscrew 2mm pitch and 100 teeth

Result can be calculated thus:

80multiplied by 17multiplied by 15 multiplied by 2  divided by 80 divided by 84 divided by 100 equals 0,o6mm per rev.

I would really prefer to use a 90 t gear instead of the 84 so if someone is in for a swap let us both benefit.

I have some funny gear numbers from aproximate imperial pitches on metric leadscrew and do not need them..

Let me know if You need.

For pure intelectual fun what imperial pitches between say  12 and 50 threads per inch are most important?

Edited By Niels Abildgaard on 24/08/2021 21:19:36

Edited By Niels Abildgaard on 24/08/2021 21:21:22

Edited By Niels Abildgaard on 24/08/2021 21:22:07

[Niels AbildgaardParticipant @nielsabildgaard33719]

Two further pictures and some thoughts (in German).

Try to click two times the pictures in the German website.

The resolution from my handheld ,8 year old Nokia phone in indoor daylight is astonishing.

 

German version

 

I am trying to get the moral fibre to part off the heavy walled pipe shown in one of the pictures.

Edited By Niels Abildgaard on 26/08/2021 12:57:13

[Ady1Participant @ady1]

I would start with decent tailstock support

[Niels AbildgaardParticipant @nielsabildgaard33719]

Posted by Ady1 on 26/08/2021 13:32:03:

I would start with decent tailstock support

You must be joking

[Alan JacksonParticipant @alanjackson47790]

Hi Niels,

Re your narrow chuck, here is my own design narrow four jaw 6 inch chuck. The body thickness is 30mm. The jaws are guided by an oval gib that can be adjusted to eliminate slackness in the jaw guidance.

Alan

[Niels AbildgaardParticipant @nielsabildgaard33719]

Posted by Alan Jackson on 26/08/2021 18:11:19:

Hi Niels,

Re your narrow chuck, here is my own design narrow four jaw 6 inch chuck. The body thickness is 30mm. The jaws are guided by an oval gib that can be adjusted to eliminate slackness in the jaw guidance.

Alan

 

 

 

 

 

Congratulation on work of a genius.

I have used hours to come up with something as good and failed.

How do You restrain the four jaw screw from coming out?

 

Edited By Niels Abildgaard on 26/08/2021 18:25:08

Edited By Niels Abildgaard on 26/08/2021 18:28:51

[Alan JacksonParticipant @alanjackson47790]

Hi Niels,

Thank you for your kind comments. The screws are secured by locked screws that can be reached inside the bore.

Alan

[Niels AbildgaardParticipant @nielsabildgaard33719]

Posted by Alan Jackson on 26/08/2021 18:29:02:

Hi Niels,

Thank you for your kind comments. The screws are secured by locked screws that can be reached inside the bore.

Alan

picture or sketch please?

[Alan JacksonParticipant @alanjackson47790]

Hi Niels

If you zoom up on the second photo you can see the screw heads in the chuck bore.

Alan

[Niels AbildgaardParticipant @nielsabildgaard33719]

Posted by Alan Jackson on 27/08/2021 09:31:58:

Hi Niels

If you zoom up on the second photo you can see the screw heads in the chuck bore.

Alan

Thank You.

Am still confused but at a higher level.

Do not bother

[Niels AbildgaardParticipant @nielsabildgaard33719]

Some high resolution stills and first cutting video.Performance is not impressive.

First cut Monster Mini Lathe

[Niels AbildgaardParticipant @nielsabildgaard33719]

First parting of.44mm Heavy wall pipe, C45 150 rpm.

Iscar Tang-Grip inserts 1.4 and 3mm.

Limit is belt slip so if I want to part 88mm I will have to make and fit a 215mm spindle belt disc.

somewhat better resolution can be seen here:

Parting off

[Niels AbildgaardParticipant @nielsabildgaard33719]

The lathe is back in 180 version with 27 mm hole and I dared to try some parting that went very well.

Iscar TAG N2J tipand blade and blade holder from China.

200RPM and nice mild steel C45..

If the manufacturers did some very small and not expensive changes it could become a very potent hobby lathe.

Parting off chinese mini lathe

[Author]

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