BA and MOD D.P. change wheels for modern boxford lathe

[SteveIParticipant @stevei]

Hi,

I have a boxford is11.30 lathe that I have been refurbishing. I have the 9 standard change wheels which came with the lathe. On a whim I got in touch with Boxford to enquire about the cost of buying the missing change wheels for thread cutting.

According to their website:

http://www.boxford.co.uk/products/man-machines/lathes/

with 4 additional wheels I can cut 0 – 8 BA threads.

with 2 additional wheels and an aux changewheel stud I can cut .3-2 MOD, and 14-60 DP.

However it turns out that they are no longer for sale. Furthermore boxford would give me no details such that I can cut my own to spec.

Does anyone have any idea of the spec? Or could point me in the right direction?

Thanks,

Steve

[SteveIParticipant @stevei]

[Michael GilliganParticipant @michaelgilligan61133]

Steve,

It's a long-shot, but this ebay listing might help.

MichaelG.

[BazyleParticipant @bazyle]

Out of interest what is the DP of the changewheels? The old Boxfords were 18DP (Myford's 20DP).

If this or your post on the Boxford yahoo group don't come up with an answer it is just a case of playing with a spreadsheet or computer program to work out some options then see what gears are most readily available.

[SteveIParticipant @stevei]

Hi,

well a little more research on the gears I have. Assuming a reasonable approximation (gear teeth might be undersize):

D.P == number of teeth + 2 / whole (outside) diameter in inches

for 3 example gears yielded a DP of 25.41, 25.43, 25.44. As there are 25.4mm in 1 inch, then a number 1 module is equal to 25.4 DP. I think it might be safe to say that these gears are 1 mod. Does that sound likely?

Michael — The long shot will not come in! These are definetly not the type. The gears have 6 keyways equally spaced. If I could work out how to post a picture I would. I don't have an online picture site I can use. Is it possible to upload a picture directly to this site?

Thanks,

Steve

Thanks,
Steve

[AndyfParticipant @andyf]

Steve, the overall (toothtip to toothtip) diameter of a Mod 1 gear is equal in mms to the number of teeth + 2. So a 50T will be 52mm (maybe a fraction less).

Other module sizes work in proportion, so a Mod 1.5 50T would be 52 x 1.5 = 78mm OD.

Andy

[Thor 🇳🇴Participant @thor]

Hi Steve,

to upload photos to this site you click "My photos" in the My account window. Then click "Create a Photo Album", give the album a name and the click Add Photo.

Regards

Thor

Edited By Thor on 07/06/2013 18:19:22

[Michael GilliganParticipant @michaelgilligan61133]

Steve,

I note that you have the late-type "splined" gears [for which, information seems to be very scarce]; but there is a comprehensive listing of the tooth-counts, on the early-models page at lathes.co.uk

This might be useful … It seems very likely that [although the DP/Module and the mounting arrangement changed] they would stick to the same tooth-counts.

Good Luck

MichaelG.

.

Edit: added hyperlink

Edited By Michael Gilligan on 07/06/2013 19:37:31

[BazyleParticipant @bazyle]

Your lathe will have more in common with new far eastern designs than the original Boxford/southbend design as far as atachments etc are concerned. Not much surprise that a modern lathe went metric on the gears – probably the nuts and bolts too. The Colchesters have splined gears, I think 7/8 over spline but not sure. Yours are probaly deliberately different to be awkward.

Back to threads. You know the Pitch of 0BA is 1mm and 10BA is .35mm so there are two sorted. 2BA at .81mm is close enough depending on how particular you are.

In general list out the threads you have using the gearbox. Then work out the ratio of the external gears between spindle and gearbox and recalculate the "threads" the gearbox alone produces even though they will be silly values of tpi. Now list the threads you want, BA, Module or whatever.
Take one thread you want. Work out the ratio between it and one of the gearbox "threads" calculated above. This is the ratio your gear train must provide.
Go to this website, Duncan's metal pages software and find the gear calculator program. It takes a list of the gears you happen ot have and the ratio you want and suggests combinations of 4 that do the trick.

[SteveIParticipant @stevei]

Hi,

 

Thanks all. Yep it seems most of the gears are very slightly under theoretical size. I don't know why but I assumed they would be DP which resulted in the approach I took to realise they wre 1 MOD.

I made a photo album and added a picture. One of them the 46 tooth is spot on Ø48.00mm.

They are all 9mm wide. You can clearly see the spline. Is this type of spline common?

I will study the notes on the lathes.co.uk website about the metric threading older type boxford. I am also reading up on the hpcgears website. It has given me some food for thought. Many thanks.

Perhaps this thread should have been posted in the begineers section.

Regards,

Steve

Edited By SteveI on 07/06/2013 20:27:51

Edited By SteveI on 07/06/2013 20:46:05

Edited By SteveI on 07/06/2013 21:19:24

[Sub MandrelParticipant @submandrel]

Steve,

Mini-lathe change gears are 1-mod. You could probably buy a full metal set from Arc Euro for the cost of a couple of genuine Boxford ones. If reboring and splining a full set is too much effort, if you made one or two splined adaptors and bored out the Arc gears to fit over these, would that work?

Neil

[John Stevenson 1Participant @johnstevenson1]

Neil has it spot on.

Another choice is to come up with your own design of driving the gears and scrap the spline method which is pure overkill for something like this.

A simple key drive has been good enough for many years for lathes smaller, larger, cheaper and more expensive than the Boxford.

A stumbling block could be the gearbox input drive if it has the spline and you may need a few gears for this if neils method won't work due to the diameter of the splined adaptor being bigger than the gear it needs to fit.

[Ian S CParticipant @iansc]

Instead of a splined hole, how about a plain hole with a key way, and using one of the splinesas a key way? would that work? Oh well just an idea. Ian S C

[Michael GilliganParticipant @michaelgilligan61133]

Just what I was thinking, Ian

Trouble is … Steve wants to make some Gears to fit the existing Shafts.

Correct me if I'm wrong but this method "Does not Compute"

MichaelG.

[Clive FosterParticipant @clivefoster55965]

The easiest way is to get a change wheel listing from another lathe and convert as required to suit your leadscrew pitch and gearbox settings. For example my metric Smart & Brown 1024 lathe has a 4 mm pitch scew and the book gives details of the additional gears needed for BA, Mod and DP. If it will help PM me and I'll do you a copy of the relevant table, heck I may even ahve it in Excel format set up for a similar calculation.

Splines are pretty standard. can be done with a single tooth keyway shaping cutter if you are patient. I'd shift the bulk of the metal using suitable size small drills before boring out the centre. Given that use is likely to be very low a bit of low cunning should come up with a way to share one splined hub between all the extra gears. Being a crude sort I'd probably take a hole saw to one of the gears you have!

As JS says the splines are overkill for the power to be transmitted, the 1024 has only a single key smaller than one of your splines.

Clive

[SteveIParticipant @stevei]

HI,

Thanks all. I think it will be a good approach to make a splined adaptor or 2 and then play with different commonly available mod 1 gears.

I will also look into what tooth counts I will actually be needing.

Thanks,

Steve

[Sub MandrelParticipant @submandrel]

If it's got an 8tpi leadscrew, the the charts in the latest MEW can be used if you halve one of the input gears or double one of the output gears.

Neil

[SteveIParticipant @stevei]

Neil,

The leadscrew pitch is 6mm. All the published details I am working from are here:

http://www.boxford.co.uk/products/man-machines/lathes/

Regards,

Steve

[Sub MandrelParticipant @submandrel]

Hi Steve,

Use the metric 1.5 charts and a factor of 4. They will still cover teh most useful sizes.

Neil

[Tony RayParticipant @tonyray65007]

Steve,

Is this type of spline common ? – Splined gears were used on Colchesters; Bantams are 8 splined and DP and the Harrison M250 and M300 are 6 splines like yours but 1.5 MOD.

It seem to me that the splines were as much a way of tying users in to OEM rather than buying stock gears and cutting a simple keyway

I was not impressed by Boxfords complete unwillingness to share a simple fact about the module – I also asked about the spline as I had hoped that the gears it would be compatible with my Harrison.

Everyone knows that the older Boxford are 18DP 14 1/2 PA (or can find out in a couple of clicks).

I'm going to post your MOD info on the Boxford Yahoo forum so it becomes more widely available.

Tony

[Mark CParticipant @markc]

Are the splines standard BS/ISO? Do a sketch and post it so we can see!

Mark

[Tony RayParticipant @tonyray65007]

Good idea Mark.

If it helps anyone the M300 M250 spline is 6 off 1/4" straight sided splines major diameter 1" the spline height is about 0.051".

There is plenty of info on metric ISo splines but I could not access any BS standard for imperial splines on the 'net. Does anyone know if the above configuration relates to a standard ?

and if so what ?

Thanks

Tony

[John Stevenson 1Participant @johnstevenson1]

Tony,

I have a load of spline data and some old splined gears but think they are Colchester.

Unfortunately I'm stuck in Russia for about another week or so and can't access that data.

John S.

[SteveIParticipant @stevei]

Hi,

Based on this drawing of the dimensions of the spline:

I have measured the following::

D== 23.10mm

d== 20.00mm

W== some range on this 5.50 through upto 5.55mm

h== hard to accurately measure

From some web research I understand that the parameter dimensions are controlled by the fit for a particular application. I also found a link detailing the relationship between the paraemters and dimension D. I have no idea if this was authoritative. Perhpas a member can educate me?

For six splines W for all fits == 0.250D

For permanent fit: h== 0.050D, d==0.900D

For slide without load fit: h== 0.075D, d==0.850D

For slide under load fit: h== 0.100D, d==0.800D

I'd be interested to learn if and what standard these gears splines are machined to. Any help appreciated.

Thanks,

Steve

[Ian S CParticipant @iansc]

The way I'd do it; shaft dia (d) with a key way cut (W) x (h) or 1/2(W), going by the drawing of Steve's, I'd use this as an alterative if I could not cut the spline. Ian S C

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