Boxford newbie

Sorry if this question has been asked a thousand times bur....

I have what I think is a Boxford 500 VSL, it has the A thread cutting gearbox is it possible to convert this for cuttin metric threads?

Thanks for helping a newbie

Yes, (I assume you have the 8tpi leadscrew) - you need the 127/100 conversion gear set. Other combinations give a near enough conversion.

Get a copy of the Boxford "Know your lathe" publication from the net and have a look at page 75 where it shows how to use the metric conversion gear and the screw cutting gear box combination.

Boxford Know Your Lathe

Edited By Speedy Builder5 on 27/03/2022 07:27:35

Hi David,

Welcome to the forum. I too can recommend the book. As said, you should be able to cut metric threads provided you have the correct change gears. There is more about your lathe at lathes.co.uk, and you should be able to buy changewheels from them too. There is a Boxford user group here, and a metric conversion chart.
 Does your lathe have a L00 taper spindle?

Thor

Edited By Thor 🇳🇴 on 27/03/2022 08:02:33

Forum member Brian Wood's book Gearing Lathes For Screwcutting includes a wide variety of alternative gearing for metric too.

You may need to check that before splashing out on a compound gear. If I recall correctly, there is insufficient room for the 127/100 gear in a VSL and it instead uses 64/50 (or something similar) to get a close approximation.

I haven't owned a VSL for some years so appologies if I'm getting confused with something else.

There is a very close approximation to 127/100 and that is 63/80 [source Southbend] if you have the gears, Another is 47/37 which is not quite as close but it was used by Hardinge so it has a decent pedigree.

Brian

63/80 is the one. Chap on ebay (no connection) sells them in delrin.

Boxford supplied 64/54 for imperial to metric gearing for the VSL model as against 127/100 for the A/B/C lathes, ie a noticeably different ratio The handbook gives the necessary gearbox settings for the A ( gearbox) model, but not for the VSL, which are presumably different. (All VSL lathes have a gearbox). I don't know if the respective gearbox internal ratios differ between the A and the VSL.

The handbook emphasises that the 127/100 gear is exact, so it seems surprising if they compromised on their top-of-the-range model.

Edited By Clive Brown 1 on 27/03/2022 18:48:49

Whilst 127 is the perfect conversion, On many lathes there is not room for a 127, so halving it to 63 or 64 is quite normal, and the error is of no practical concern. Noel.

I agree that a 127 gear is large, although the standard Boxfords do accomodate one easily enough. I was trying to highlight that although 64 is close to 127/2, 54 isn't so very close to 100/2, so the Boxford conversion gears for the VSL lathe is not simply a case of halving the size of both gears to give a "near-enough" ratio,.

Clive,

Boxford supplied a second double gear of 65/76 to mesh with the one you listed; I don't know how they were arranged as there are 4 possible combinations, which might explain their apparently lax attitude to the gearing that puzzled you

Brian

Brian,

The 65/76 T compound gearthat you mention is quoted in the Boxford book for converting a metric VSL lathe to cut imperial threads whereas the 64/54 T is imperial to metric. In neither case is any other set-up information given for the VSL.It seems that the OP will have to do some digging to find this. Maybe the Boxford Owners Forum could help.

Clive

lathes.co.uk have an interesting comment in their VSL information:

'... on these lathes a screwcutting gearbox was standard - but some had different internal ratios and the English/metric and metric/English conversions gears arranged to be more compact with pairs of 64/54t and 76/65t respectively instead of the usual 127/110t (inch to metric) and 135/127t (metric to inch) gears. At one time it was believed that all gearboxes on the L00 VSL lathes had the altered internal ratios but several examples have been found in the USA (one being a VSL500 manufactured in 1977 with serial number V.S.L. 71861-L00) where this is not the case, the gearboxes being of the earlier, ordinary type. It is suspected that, while Boxford fitted a different gearbox to the earlier VSL models with the L00 spindle nose, this practice was discontinued and later editions of the manual not updated to reflect the change. If you buy a gearbox-equipped lathe that appears not to generate the pitches shown on the screwcutting plate check the special manual produced by lathes.co.uk, it shows all the ex-factory arrangement of the changewheels.'

As there are VSL variants, it's necessary to identify exactly what gear-ratios are fitted to David's particular machine before rushing to buy a metric conversion gear pair. The special manual sold by lathes.co.uk might reveal all instantly. Otherwise, possible to work out what's needed from the lead-screw pitch and available gear-box ratios.

Another good news / bad news answer. Good news, David's lathe will do metric in the usual way by fitting the appropriate change gears. Bad news, finding what the appropriate change gears are isn't easy because VSLs aren't identical. Homework required.

David doesn't mention having any change-gears : if the lathe came with a box of accessories, the metric gears might be in it?

Dave

Dave, well found! Seems nothing is simple, but at least there is a useful source of information for the OP. I have read lathes.co.uk in the past but that piece had gone unnoticed.

Should say that my interest is academic as I have the bog-standard imperial ME10.

Hello Clive,

My mistake; my apologies. I read that entry only today and missed the significance of the word respectively and leapt immediately to the wrong conclusion!

My interest is even more academic than yours, the closest I get to Boxford is with a Sabel and the Smart and Brown copy of the Southbend gearbox

Regards Brian

If the ratio in the gearbox is 'different' then the gear train from spindle to gearbox must compensate so compare what is on your lathe to any other VSL specific data / pictures you can find.

When 127 is used to imp>metric it is a driven gear, When 63 is used it is normally a driver but as it is 7x9 you can often use other gears to achieve the ratio.

What is important is always the primes involved so using higher primes is sometimes better. Late Drummonds/early Myfords used 46/73 or 2x23/73.
Harrison M300 uses (8x36)/(19x11x35) much better (left the 36&35 as so because they are fixed at the gearbox output for metric threads)
Colchester uses (13x5x29)/(19x7x36) staggeringly close at 2.540053

In each case you throw in some of the common changewheels with factors of 2,3,5,7 to get the thread you want.