Member postings for Niels Abildgaard

Where can Chris Boll be contacted for drawings?

Niels

Hello Robin and thank You for links.

Exactly what I wanted to look at.

The CJ0625 is a very different animal but the procedure described in the Grizzly manual of Yours is universal for adjusting spindle bearings and has been bookmarked.

Niels

Hello Graham

Thank You for kind words.

There are pictures of Your lathe in album.

What is size of lathe and can I have a picture of the headstock with internals?

And spindle bearing numbers?

I am interested as the screwcutting geartrain seems to be the same as in my future (and latest. I swear) dream lathe.

Chineese of course and a 38mm bore for 1000$ called CJ0625.

The same gentleman explain carbide part off tooling (and I hijack the thread here)

Step parting

Edited By Niels Abildgaard on 30/04/2021 09:15:08

An old describtion of a homemade,ultra-rigid

Toolingship

Is 5 degree to little?

Many carbide inserts run 7 degree or more

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.

Was ER 40 collets an option and why not?

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

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

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.

As a sewing machine motor fan I sincerely hope You will put up more writing and video concerning potentiometer substuting.

Personally I think the Hall Sensor is more fail safe,but hearing contra views is interesting.

A Myford with 500Watt BLDC(smallest size) is an overkill.It will maybe selfdestruct.

My latest motor is a 1500 Watt /12Nm/3500rpm and that will make a Myford look like an (Expensive) corkscrew.

I have been thinking very hard how to make my next 62mm bearing bore lathe more capable.Main problem is to make a system of mandrels holding front bearing holder while Chokfast,Non-shrinking loctite or epoxy sets without locking up tool as well.

On the other hand it is only for the brave or rich as it will not be possible to go back.

You can se on picture that the bearing bore stop on front bearing hole has to go.Not a precission job but non recoverable.

While I am at it it is no big deal to show how it can look on a 290 lathe with 75mm bores.

Edited By Niels Abildgaard on 21/03/2021 08:38:55

It is  an offence to us underpriviledged citizens in not going to the moon soon countries ,to ofload us so much iron and then put such a small knitting neddle spindle in.

As luck have it I can offer two solutions that do not need any change of headstock.

Please enjoy.

Edited By Niels Abildgaard on 19/03/2021 16:51:32

Edited By Niels Abildgaard on 19/03/2021 16:53:32

Edited By Niels Abildgaard on 19/03/2021 16:54:04

Edited By Niels Abildgaard on 19/03/2021 16:54:41

A good advice to Niels:

Do your homework before touching keyboard. The CQ6128X660A lathe is 280 size with 660mm between points.

This is more or less a Brother of JasonB s.But a smaller 26mm spindle I think.

It depends on what You define as ligth

Modified 180 Lathe

it was done with a sewing machine motor

Stiffened 180 lathe bed

Edited By Niels Abildgaard on 18/03/2021 16:34:12

The bed of the 180/210 lathes is Lousy but the Canadian gentleman lathe is a 250 and frame is miles better than Myfords and on par with Southbend/Boxfords

Edited By Niels Abildgaard on 18/03/2021 15:44:35

For parting on my Boxford I made a very stiff system and for my 250 with solid flange another.

The ME photo insert system is a disater waiting to happen for us unpaid writers

Edited By Niels Abildgaard on 18/03/2021 10:52:13

The lathe is a 26mm bore 250 size like the much loved one I had before my son liberated it.He will get a surprice when estate is parted.

First thing is that it shal have a solid foundation.

The old Emco toolholder system is idiotic and a momemade came on

Power per litre is an armchair unit.

For two strokes on unpressurised air and no liquid oxygen(nitro) the ultimate limit is the blowdown time area.

If you double all dimensions we get eigth times the volume but the exhaust area gets only four times bigger and air does not want to go faster than mach one in such situations.

If we considder Aprilia 125 ,54 times 54 mm, and 53 horsepower as the ultimate two stroke ,we can say that is 424 horsepower per litre and look very smart.

The engine mentioned above of 14.74 ccm that is 8.5 times smaller volume and should thus give 53 divided by 8.5 equals 6.2 horsepower if as well dimensioned as the Aprilia thing.

The port area ratio is not 8.5 but 4.1 and if the boat people were as good as Aprilistas they should get around 13 bhp.

It is my guess that headstock bores for cups and spindle seats for cones are more than ten times more unround than chineese taper rolling bearings.

To use Your own time hunting unicorns is OK,but the bearing merchants are there for living.

The whole point of tapered roller bearings is to adjust their preload on site.