By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Allendale Jan 24th

Boxford Lathe Big Bore Conversion

Big bore conversion?

All Topics | Latest Posts

Search for:  in Thread Title in  
Niels Abildgaard18/08/2017 14:30:23
260 forum posts
89 photos

The 290 spindle on photo has 38 mm bore and bearings are 95/60 and 90/55

**LINK**

I will try and exchange it for a 280 spindle

Brian Moss18/08/2017 18:00:23
20 forum posts

Hi Niels,

Very many thanks for this excellent information. From your photo I have estimated the lengths of each of the 7 sections of the spindle as follows starting from the threaded end: 80mm (including thread), 20mm, 50mm, 80mm, 60mm, 25mm, and 20mm.

Could you please confirm that these figures are correct, and if wrong could you give the correct lengths?

Finally , what is the diameter of the flange for fitting a chuck?

Regards,

Brian.

Niels Abildgaard18/08/2017 18:42:55
260 forum posts
89 photos

Hello Brian

 

Starting from chuck end. Diameter and length

 

70/14  123/16,5  70/24  60/59,5  57/73  55/45,6   52/21  48/50

Thread M48 pitch1,5 mm/24,5.

Do You have an idea how to line bore precisely?

Kind regards

Niels

 

 

Edited By Niels Abildgaard on 18/08/2017 18:44:11

Edited By Niels Abildgaard on 18/08/2017 18:46:28

Brian Moss18/08/2017 20:12:03
20 forum posts

Hi Niels,

Many thanks for the above; now the real head scratching begins!

My idea would be to line bore the spare headstock on the bed of a similar Boxford lathe. It sounds straight forward (famous last words) but I think it could be done accurately with care.

Kind regards, and thanks again,

Brian.

Nick_G18/08/2017 20:27:13
avatar
1808 forum posts
744 photos
Posted by Brian Moss on 18/08/2017 20:12:03:

Hi Niels,

Many thanks for the above; now the real head scratching begins!

My idea would be to line bore the spare headstock on the bed of a similar Boxford lathe. It sounds straight forward (famous last words) but I think it could be done accurately with care.

Kind regards, and thanks again,

Brian.

.

Hi Brian,

Do you mean in a similar way to this but with the headstock and not as in this example the tailstock.?

Niels Abildgaard19/08/2017 08:39:56
260 forum posts
89 photos
Posted by Brian Moss on 18/08/2017 20:12:03:

Hi Niels,

Many thanks for the above; now the real head scratching begins!

My idea would be to line bore the spare headstock on the bed of a similar Boxford lathe. It sounds straight forward (famous last words) but I think it could be done accurately with care.

Kind regards, and thanks again,

Brian.

 

 

Hello Brian

 

Good luck with boring and give us many clear photos.

It is a lot of bother to find a container for sending You the spindle and I cannot do it rigth now.

Contact me when You have succeded line boring and I will look for a suitable postage box in the meantime.

 

Kind regards

Niels

Edited By Niels Abildgaard on 19/08/2017 08:43:08

Edited By Niels Abildgaard on 19/08/2017 09:03:47

Brian Moss19/08/2017 11:28:44
20 forum posts

Hi Nick_G,

That's great to see! It's amazing what you can find on YouTube,

Brian.

Brian Moss19/08/2017 11:32:37
20 forum posts

Hi Niels,

That's fine, and thanks for wishing me luck!

I have sent you a PM with my email address so that we can keep in touch,

Regards,

Brian.

Niels Abildgaard29/08/2017 19:41:22
260 forum posts
89 photos
Posted by JasonB on 15/08/2017 12:21:26:

The 280 headstock is 180mm long though there is sufficient 45mm dia on the spindle that a 190mm long head casting would not cause issues.

Quick sketch of spindle below, click to make larger. Bore is 26mm to clear 1" stock, MT4 taper, Flange chuck mount. At the far end there is a section of 40mm dia which has a key slot and this takes the gear for feeds and the two step pully. Adjusting nut on the M39 thread. Spacer on the bit of 45dia that sticks out the head so that when nut is tightened everything pushes against the bearing. Sizes are as good as I can get without removing the spindle.

280 spindle.jpg

280 head parts15082017.jpg

Edited By JasonB on 15/08/2017 12:26:33

Jasons idea is very smart.No headstock modification and much bigger spindle bore and /or bending stiffnes .

Let us calculate .

Existing set up is lower part of picture and outher profile of spindle is a short piece of 3.81cm and rest is 3.5cm diameter and spindle bore is 2.05cm.

For a first aproximation let us say 3,6cm outside with a hole of 2.05

Bending stiffness is a fourth power thing and is proportional to 3.6**4 - 2.05**4 =168-18=150(more or less)

The new spindle is 45 mm outside and i want to calculate how big bore for same bending stiffnes

Equation becomes 4.5**4-X**4 = 150 giving a bore of 4.0cm

Double bending stiffnes is 4.5**-X**4= 300 allowing a bore of 3.2 cm

If we do not modify the chineese spindle that is 2.6 cm inside we get a stifnesvalue of

4.5**4-2.6**4=365 or roughly 2.4 times the boxford spindle value.

 

 

 

 

 

http://[img]http://i.imgur.com/fX55Bjm.jpg[/img]

Edited By Niels Abildgaard on 29/08/2017 20:01:31

Niels Abildgaard30/08/2017 09:32:51
260 forum posts
89 photos

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 Abildgaard01/09/2017 18:31:24
260 forum posts
89 photos

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 Abildgaard03/09/2017 06:38:53
260 forum posts
89 photos

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 Abildgaard03/09/2017 17:13:58
260 forum posts
89 photos

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 Abildgaard03/09/2017 18:08:20
260 forum posts
89 photos

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 Abildgaard08/09/2017 23:11:02
260 forum posts
89 photos

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 Abildgaard09/09/2017 10:11:52
260 forum posts
89 photos

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 Abildgaard24/02/2018 20:01:49
260 forum posts
89 photos

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 Abildgaard17/01/2020 09:18:51
260 forum posts
89 photos

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.

MegaBox

 

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

Niels Abildgaard17/01/2020 09:28:26
260 forum posts
89 photos

A picture of standard Boxford

Standard Boxford

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Latest Forum Posts
Support Our Partners
Eccentric July 5 2018
ChesterUK
cowells
Warco
emcomachinetools
Ausee.com.au
Allendale Electronics
Eccentric Engineering
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest