Boxford Lathe Big Bore Conversion

[Niels AbildgaardParticipant @nielsabildgaard33719]

The rear bearing has to be a special Schaeffler 320/42x and I donot have the courage to ask for a price yet.

They are 2 dollar each from China.Probably used in cars

 

 

Edited By Niels Abildgaard on 30/08/2017 09:34:25

Edited By Niels Abildgaard on 30/08/2017 09:35:23

Edited By Niels Abildgaard on 30/08/2017 09:35:45

Edited By Niels Abildgaard on 30/08/2017 09:41:58

[Niels AbildgaardParticipant @nielsabildgaard33719]

First update since1955.

Bigger and stiffer spindle.

>**LINK**

Only problem is to reduce outher diameter of new front bearing from 78 mm to 76.2mm.

https://simplybearings.co.uk/shop/p152859/NSK+5030G+Taper+Roller+Bearing+50x78x19mm/product_info.html

It is then possible to have a 38 mm hole not all through and 2.5 times bending stiffness of present spindle

Edited By Niels Abildgaard on 01/09/2017 18:33:31

Edited By Niels Abildgaard on 01/09/2017 18:38:44

[Niels AbildgaardParticipant @nielsabildgaard33719]

It has been quite some headschratching,but I think it can be done like picture:

>**LINK**

Change on the headstock casting is minimal.Only the grease traps behind bearings have two be enlarged from around 38 mm to 50 for the front one and from 35mm to 45.3 for the rear one.

The new front bearing is a 55£ 78/50/19 mm where I reduce outside to 76.2

and the rear is a 6£ 73.4/45.24/19.56mm .

I will start buying three of the cheap ones and experiment buy cutting them to 72 mm outside with some of my homemade carbide tangentials.

The new spindle will be 36 mm inside and three times less bendy than yhe stock one.

Edited By Niels Abildgaard on 03/09/2017 06:40:29

[Niels AbildgaardParticipant @nielsabildgaard33719]

A friend on another forum has proposed smaller section bearings so that no bearings or cast iron shall be mistreated.

The front bearing on my Boxford has a 76.2/38.1/23.8mm bearing with a load rating of 5.0/6.7 tons.

NSK make something HR32910J measuring 72/50/15 with a load rating in same units of 3.6/5.5 tons

Sligthly shorter life but much bigger hole.

>**LINK**

Where can I buy such bearings?

Edited By Niels Abildgaard on 03/09/2017 17:18:44

[Niels AbildgaardParticipant @nielsabildgaard33719]

Have sent 40$ to China and expect or hope to receive 4 bearings within a week.

Edited By Niels Abildgaard on 03/09/2017 18:09:49

[Niels AbildgaardParticipant @nielsabildgaard33719]

It has been a lot of head schratching but we are getting closer.

It is nice if we can avoid  removing headstock from bed and  do all  work at home.

>**LINK**

The first modification on headstock is opening the cast iron grease traps up to 50.05mm and 60.05mm from 35.05 and 38.15mm repectively.

The new aft bearing is a 32910 costing between 3 and 140£ depending on source and delivery time.

My three $ ones has not arrived yet. 72/50/15 mm.

New front is 32913 (90/65/17 mm) between 29 and54 £

We will have to cut (CONCENTRICALLY) a corner that is 90mm diameter from 76.2 mm

and 10 mm deep.

Beauty is that if we regret it is no big deal to reinstate the original bearings and spindle.

New spindle with 65 outside and a long hole of 63.5mm will have same bending stiffnes as stoneage Boxford.

 

Edited By Niels Abildgaard on 08/09/2017 23:12:37

Edited By Niels Abildgaard on 08/09/2017 23:14:55

Edited By Niels Abildgaard on 08/09/2017 23:19:51

[Niels AbildgaardParticipant @nielsabildgaard33719]

I have just bougth Koyo bearings type 32910 (72/50/15) and 32912(85/60/17) for 100$ from

**LINK**

I have reduced spindle design diameter 5mm.

It is crazy big anyway and it is less cast iron in headstock to remove.

Edited By Niels Abildgaard on 09/09/2017 10:12:13

[Niels AbildgaardParticipant @nielsabildgaard33719]

Hello Brian and have You line-bored the spare headstock ?

Bending stiffness is a third power(not four as I wrote half a year ago) and I intend to improve my Boxford without removing headstock from bed.The only change to headstock is to increase diameters of the grease traps inside the bearings.If I make a spindle with 50mm outside where bearings are and have a through hole of 38mm I will have two times the bending (and Torsion) stiffness of the normal Boxford spindle with 20mm hole.

Does someone know what bearing inner diameters on VSL spindle?

If You read this Brian and have some of the 50/72mm chinese bearings left please send me two.

 

 

 

https://i.imgur.com/XcYInSx.jpg

Edited By Niels Abildgaard on 24/02/2018 20:04:38

Edited By Niels Abildgaard on 24/02/2018 20:06:19

Edited By Niels Abildgaard on 24/02/2018 20:06:53

[Niels AbildgaardParticipant @nielsabildgaard33719]

An old thread but I have seen the holy light.

To make a really usefull Boxford ,we can machine a front bearing holder (bearing 32913) as shown and fit it in front headstock front bearing hole that   is bored 3Inch/76.2mm.

These new,slimline bearings have 65mm holes and spindle front part can easily have a 55mm hole.

I hessitated to send Brian the used chineese spindle as I thougth he underestimated the trouble of line boring headstock.

After having seen the holy ligth and I would not have hessitated but it had served no purpose either.

This new illuminated solution is pure lathe work and spindles are easy to make.

If the chucklholder face of spindle is made after assembly in the Boxford , no Schaublin,Hardinge etc will better it.

Please enjoy or critisize.

 

Edited By Niels Abildgaard on 17/01/2020 09:25:18

[Niels AbildgaardParticipant @nielsabildgaard33719]

A picture of standard Boxford

Standard Boxford

[Niels AbildgaardParticipant @nielsabildgaard33719]

I had sworn that I would not allow a Boxford in my house and was looking for suitable WM250 headstock to make two big spindle experiments.

My WM250 machine with MC4 is a very nice machine.

By accident a cheap model A 19509 Boxford saw me and followed home.

It has been in school since 1966 and has seen very,very little  use.

The complete drive system with a 0.5hp three phase Crompton will leave as will all the rotating parts in headstock plus gearbox and (imperial) leadscrew.

The spindle scheme to be tried first is this.The lines are 10mm apart.Bearings 32910 and 32916

Edited By Niels Abildgaard on 04/07/2020 15:34:47

[BazyleParticipant @bazyle]

Posted by Niels Abildgaard on 04/07/2020 15:30:17:

I had sworn that I would not allow a Boxford in my house

Edited By Niels Abildgaard on 04/07/2020 15:34:47

Well I was going to excommunicate you for this sacrilege but your proposition is sufficient for a pardon, at least temporary.

Looks like you are aiming for 38mm through bore which is quite impressive.

[Niels AbildgaardParticipant @nielsabildgaard33719]

Posted by Bazyle on 04/07/2020 16:27:34:

Posted by Niels Abildgaard on 04/07/2020 15:30:17:

I had sworn that I would not allow a Boxford in my house

Edited By Niels Abildgaard on 04/07/2020 15:34:47

Well I was going to excommunicate you for this sacrilege but your proposition is sufficient for a pardon, at least temporary.

Looks like you are aiming for 38mm through bore which is quite impressive.

My latest Boxford refugee from 1979 has a big bore spindle where bearing holes must be at least 85mm diameter-

Spindle through hole will be 55 or 50 mm.The gearing to leadscrew needs some thinking.

Are there some Boxford fans here who knows what bearing dimensions are now?

[Niels AbildgaardParticipant @nielsabildgaard33719]

I have played director of a hobby lathe factory for quite some time now.

I started with a thread called Ideal lathe spindle nose

I got involved in this Boxford big bore thing

I started a thread named Lathe improvement.

It was all a try to define the next million making hobby lathe generations and i now se it as a classical example of starting at the wrong end of problem.

One should rather start with what holding chucks,faceplate etc are usefull.

For a 240mm lathe minimum tooling is:A faceplate ca 200mm.An ER40 holder and a 125 or 160 mm fourjaw independent with the shortes and stiffest connection to spindle.

A 100 or 125 three jaw will not harm but will not se much use either

My newest plaything is industrial sewing machine motors and they stop instantaneously so screw on holders are no,no.

Parting of demands stiff spindle and very short overhang so the Loo nose of my new Boxford is in danger of being replaced.

Boxfords have two very good traits from Southbend:

The bed has six level points on underside from machining and in connection with a piece of granite we are in Schaublin/Hardinge country.

The combined feeding,facing and treading system with one slitted leadscrew

If someone knows bearing dimensions please tell me.

My fingers are itching.

Edited By Niels Abildgaard on 14/12/2020 20:05:45

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