Boxford AUD

[Perrie HulettParticipant @perriehulett60924]

Hello,

I have just purchased a lathe and joined this group so am right at the beginning of my engineering journey.

I have purchased a Boxford AUD long bed with Norton gearbox and power cross slide.

Being completely new to lathes and buying locally from a professional tool maker so mistakenly trusting the seller I did not realise that the cross slide lead screw is completely worn out. Worn out as in if I push and pull on the cross slide it moves a good 2mm.

To be sure, I have removed the lead screw and brass nut and you can visually see the difference in thickness of the threads in the middle compared to the ends.

I am not too concerned, as the reason I love engineering and working with metal so much is the fact that you can make/repair anything within reason.

The above is about to be tested it would seem as I have today been told that the lead screw in question is now an obsolete part.

so my question is, is it really obsolete or could someone on here make one?

Alternatively could I cut off the worn thread buy a new ACME thread and TIG weld it on.

I have run a standard metal file over it and it is definitely not hardened.

Any help/advice would be really appreciated as I’m chewing at the bit to start making chips.

Thank you.

[Perrie HulettParticipant @perriehulett60924]

[Thor 🇳🇴Participant @thor]

Hi Perrie,

Welcome to the forum. Making a new feed-screw is one solution. Have you checked lathes.co.uk? They may have a spare. I assume you have a copy of Know Your Lathe? There is also a Boxford group.

Thor

Edited By Thor 🇳🇴 on 04/10/2022 07:37:18

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Perrie, there is a used one on Ebay complete with the handwheel bracket and nut, which is an imperial one, which looks decent.

Regards Nick.

[HollowpointParticipant @hollowpoint]

I would have thought it's more likely to be the bronze nut that is worn than the leadscrew? If so you can purchase them on ebay, alternatively you could try making it into a split nut so you can adjust the play out. Basically you slit the nut and add a grub screw to push the two halves apart slightly.

Edited By Hollowpoint on 04/10/2022 09:37:43

[Phil WhitleyParticipant @philwhitley94135]

The usual method of repair is to cut off the old thread, put a bore in the remainder, turn down the new thread to suit the bore, and locate the new thread with a roll pin in a drilling through both components. this ensures that the thread is perfectly in line with the rest of the handwheel shaft. You will also need to replace the nut, which will mean buying a standard nut from the thread suppliers and modifying it to fit, or making a blank and then drilling and tapping it to suit. Taps are available from Tracy tools and also RDG. there is always some backlash in cross slides, there has to be to accomodate minor imperfections in the threads, that is why you wind back and then forwards again, as this eliminates the backlash from the handwheel scale reading. Also make sure there is no lost motion in the handwheel thrust washers or bearings, and make sure the nut is securely fixed. can you pull the handwheel in and out? that is lost motion in the thrust assembly. TBH I think all my lathes have more than 2mm backlash on cross slides, and used correctly, it does not cause a problem. On lathes, cross slide screws and nuts should be considered a wearable, which will need to be replaced several times in the life of a well used machine. Pointless buying a second hand screw with wear already in it, my first lathe, a DS&G 13Z had already been repaired in this way (and worn out) when I got it, and I fitted a new thread and made a nut which was threaded for me as taps were not easily available "I them days" Don't sweat it!

Phil

Edited By Phil Whitley on 04/10/2022 09:45:18

[not done it yetParticipant @notdoneityet]

Posted by Hollowpoint on 04/10/2022 09:33:08:

I would have thought it's more likely to be the bronze nut that is worn than the leadscrew? If so you can purchase them on ebay, alternatively you could try making it into a split nut so you can adjust the play out. Basically you slit the nut and add a grub screw to push the two halves apart slightly.

Edited By Hollowpoint on 04/10/2022 09:37:43

You will, most likely, need a new or repaired feed screw nut – choose now whether you want imperial or metric.🙂

Repairing could be boring out the old threads and fitting a sleeve (threaded or to be threaded). Or turning off the threaded part and soldering on a new threaded section. Nuts have been repaired with Acetal by the “heat’n’squeeze” method.

Screw wear can be evaluated (if necessary) by checking the backlash difference at the midle and extremities of the screw.

Removing the thread then boring and fitting a fresh bar, in its place, is easy enough with (a) pin(s) and loctite. The bar could then be easily turned to diameter and single pointed to your requirements. Usually, with a bar or a finished threaded bar (or finished-size awaiting threading).

Nothing too arduous – you choose the way that best suits your ability. Threaded ACME or trapezoidal threaded rod for feed/lead screws is readily available.

Edited By not done it yet on 04/10/2022 10:13:16

[William ChithamParticipant @williamchitham75949]

When I bought my Boxford a few years ago I was concerned about backlash too but, as Phil says, once I gained a bit of experience using the lathe I realised that backlash isn't actually that big a problem. If it is a metric lathe like mine with a 2.5mm pitch screw on the cross slide then I think you will have to make your own replacement or find a decent used or NOS part – I have searched in vain for a supplier of acme threaded bar in this pitch.

William.

[Ady1Participant @ady1]

If you put a decent DRO on your cross slide then as long as it works it's fine, backlash issues for measuring are eliminated

A new cross slide nut would make things even better

At some point you will either make or be able to buy a newer CS leadscrew

A Nice lathe, lucky you

Edited By Ady1 on 04/10/2022 10:18:20

[Perrie HulettParticipant @perriehulett60924]

Hi,

Thank you all for your responses.

when on the machine the cross slide has little to zero backlash when wound fully out and the same when wound fully in but has 2/3mm in the middle. I can see with my eyes let alone measuring that the middle threads are at least half the thickness of the threads on each end.
Is the difference between imperial and metric only depend on the cross slide dial or is it the lead screw as well?

thank you again.

ps can somebody confirm the name and size of the cross slide lead screw thread on this lathe Boxford AUD.

[Clive Brown 1Participant @clivebrown1]

Metric Boxfords have a 2.5mm pitch thread. Imperial machines have a 0.1" pitich thread, ie slightly bigger. The dials are also differently calibrated of course.

For second-hand spares, it might be worth joining the Boxford group on Facebook. there's a couple of members who stock them.

Edited By Clive Brown 1 on 04/10/2022 13:36:11

[mgnbukParticipant @mgnbuk]

There is another way around a locally worn screw. This method was used by a machine tool rebilding company that was part of the group I served my apprenticeship at & I was seconded there for a couple of months experience.

On a Herbert centre lathe with a worn cross slide screw, the screw was re-machined to remove the"unworn" sections of the thread to make it a constant (but now non-standard) form & a matching non-standard threadform nut made to suit, rather than replacing the screw & nut with new parts – all about keeping costs down.

In this case the screw was re-machined on a thread whirler rather than screwcut, but I don't see why it couldn't be done by screwcutting. The resultant thread has 2 new wearing faces with a now even gap along its length, but would obviously rattle in a standard nut hence the need for making a replacement nut to suit the now non-standard thread form.

I particularly remember this as it was a bit of extra money for me – I took the screw & nut to and from the sub-contract machine shop who did the work – strapped along the length of my motorcycle – & got paid the "up tp 1300cc" car mileage rate for a budget 250cc bike. Apprentice wages in 1979 were not great, so every little helped !

Nigel B.

[Dave HalfordParticipant @davehalford22513]

The only problem with doing the lead screw swap is you have to use it to turn down the spigot.

So, you test drill some scrap, then turn down the new acme thread for 1/2" to match the hole, then saw the old thread off the lead screw, chuck and drill. Loctite the two together and refit the next day. Very easy to do and mine has not needed pinning.

I found that with the leadscrew with 50thou slop + the nut wear was fine with a DRO until you wanted to bore something. Loading up the leadscrew the other way gave an unreliable cut depth. Parting was impossible.

Don't forget you probably have dovetail wear as well.

This guy does nuts on Ebay should be 3/8" 10tpi but measure yours.

threaded rod might have to be US supplied. half inch can be got in the UK from HPC

Edited By Dave Halford on 04/10/2022 14:59:32

[BazyleParticipant @bazyle]

Backlash is rarely a problem and variations between middle and ends of a crew don't have much effect unless you are doing milling and co-ordinate drilling to fine tolerance. However +1 for MGNBUK's method. You can use the topslide to provide infeed for the process, Once complete you have a fully functioning lathe to use to make the new parts, There is (or was) a website detailing the mach9ining of a new crosslide screw for the equivalent Boxford clone a Hercus lathe.

Another trick is to use the lathe as is to make a short length of nut say 3 turns, then solder it onto the existing nut so that the main nut is taking the thrust of cuts and the add on is just reducing the backlash. Again a temproary fix for a few years while you get round to making new parts.

[BazyleParticipant @bazyle]

BTW much more significant is the provision of a nice adjustable index wheel on the slide and coping with the messed up threads around the handle grubscrew that are so common. Also don't forget the screw in the middle of the star wheel on the apron is REVERSE thread.

[Howard LewisParticipant @howardlewis46836]

If remotely possible, find and join a local M E Club.

There will almost certainly be someone there who can help you, and probably be willing to make new parts for you.

(It will be a good learning expereince for you to see how they go aboiut it. )

If you are new to lathes and lathework, buy one or more books.

You will certainly refer, frequently to Zeus Charts.

There are a number of books that will increase your store of knowledge.

The book referred to by many people is "The Amateur's lathe" by L H Sparey.

Other useful books will include "The Amateur's Workshop" by Ian Bradley. Covers general workshop activity as well as setting up a lathe.

"Basic Lathework" by Stan Bray.

"Lathework" by Harold Hall.

Both are former Editors of Model Engineers'Workshop

Neil Wyatt, current Editor of Model Engineer' Workshop has written a book on Lathework, based on his experience of a more modern machine, the Sieg SC4,.

Al;l of these books will show the basic techniques, of setting up and using a lathe,, tool grinding and setting, which will help you to gain experience and confidence.

Without learning and understanding the basics, you are more likely to struggle. A good book will have the answer to the question that you are about to ask, and give an explanation.

When the lathe up and running, practice on pieces of mild steel. make small workshop tools, such a Centre Height Gauge, Tap Wrench, Die Holder, and then graduate to a Sliding Tailstock Die Holder, and possibly a Mandrel Handle.

Making these tools will bring you experience, and knowledge, give you confidence, and provide small tools that you can use for the rest of your life. .(you will use some of them every time that you mount a tool in the lathe or Tap a hole, or cut an external thread.

Good Luck

Howard.

[Howard LewisParticipant @howardlewis46836]

P S.

If you want to make a new Leadscrew and Nut, Tracy Too;ls will probably be able to provide the tap and Die that you mneed.

It may mseem costly, to buy tooling that you only expct to use just once, but it will enable to resuscitate a very useful and versatile machine.

The gearbox will make changing feed rates, or thread pitches easier .When you approach screwcutting, buy

"Screwcutting in the Lathe" by Martin Cleeve, No 3 in the Workshop Practice Series. Some of the other books are also min the Workshop Practice Series.

If you can get to the Midlands Model Engineering Show, will be able find a stand selling them, and others selling tools and materials.

[Perrie HulettParticipant @perriehulett60924]

Just an update:-

with the lead screw removed I have checked the cross slide travel for wear and there is none as I can detect, in fact I tightened the gib screws a little and it slides between both extremes of travel without binding or looseness and seems in rude health. I have put everything back together and the gib tightening has all but negated any physical backlash.

so why do I have such a terrible finish even on brass and aluminium? In fact when I take cut along the length of a piece I can visually see the cutter tip backing away and back in to the piece creating deep ridges. Also I can take a cut ( having wound the slide towards to piece to eliminate potential slack) back away from the piece and each time I go back across the work it’s takes some material off even thought I haven’t moved anything? I can do this half a dozen times and it still removes material! I know I’m a noob but this seems extreme!

[Clive Brown 1Participant @clivebrown1]

Posted by Perrie Hulett on 06/10/2022 10:53:13:.

so why do I have such a terrible finish even on brass and aluminium? In fact when I take cut along the length of a piece I can visually see the cutter tip backing away and back in to the piece creating deep ridges. Also I can take a cut ( having wound the slide towards to piece to eliminate potential slack) back away from the piece and each time I go back across the work it’s takes some material off even thought I haven’t moved anything? I can do this half a dozen times and it still removes material! I know I’m a noob but this seems extreme!

Can you see where this movement is stemming from?

Is the top-slide, which carries the actual tool-post, properly adjusted and firmly fixed to the cross-slide? Are the tool-post and tool firmly clamped down?

Can you lock the main carriage by means of the lock-bolt on the front LH corner and then try machining a fairly short, say 30mm, length of material using the top-slide travel and see if that improves the finish?

Presumably the lathe spindle bearings are properly set up with no play in the spindle but maybe worth checking.

Edited By Clive Brown 1 on 06/10/2022 11:47:37

[Clive Brown 1Participant @clivebrown1]

Sorry, brain fade, carriage lock is on RH side NOT LH.

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