Boxford "Industrial 11-20" crosslide thread?

Hi All,

I have recently bought an "Industrial 11-20" Boxford that requires a new crosslide nut.I have a small manual surface grinder and intend to grind a single point tool to cut the thread. The lathe is a netric model with a 2,5mm pitch L.H. thread on a 12mm diameter crosslide screw. I initialy thought that the thread form would be Trapezoidal, other dimensions being metric. Following some research on the net and other posts on this website I am led to believe that due to the age of the lathe (c.late 1980s), it is more likely to be Acme. Does anyone know for sure the thread form used on these lathes?

Use the male cross slide screw as a template to make the tool.

Tony

If you are close enough to me I can ascertain the angle for you, see profile. If not you can photograph the thread, close up and try to take the pic at the thread angle so you get a clear image, expand the image, print if you want and measure the angle.

It will not be absolutely precise but good enough to show whether its 29 or 30 deg -- you will really need the cross slide feed screw as a gauge or maybe the compound is the same thread ?

John

Make yourself a gauge out of sheet metal cut and filed (or surface ground) to either 29 or 30 degrees and see how it fits your old thread.

Hi All,

Thanks for your replies. I have the crosslide screw and will probably make sheet metal gauges from it as Hopper suggests. It's not possible to make an accurate tool straight from an unworn portion of the original screw. I am wondering if I should cut the female nut thread slightly deeper, to give slightly more than the normal 10 thou clearance at the thread crest and. This is because the nut is split horizontally on one side, with a pinch bolt to allow slight adjustment to take up wear. Even with the standard 10 thou, the tool point will be narrower than the land at the root of the male thread, and I don't think I'll be able to decide on one degree over about 1.5mm in loose joint when offering up the tool point to the thread. Just thought if someone knew for sure I could "hit the ground running". I may try the photographic method first as it may save som time. Thanks for your help.

Sean.

If you do go deeper, you will need to make your toolbit with a slightly narrower flat on the end, otherwise going deeper will make the thread looser on the angled flanks.

It might be worth slightly decreasing the OD of the blank, (make allowance for this in the depth of thread, but my advice, FWIW is to keep the thread dimensions the same in other respects. Increasing the depth, and therefore the distance between flanks, as Hopper says, will only make the fit looser, which is not what you want.

Surely the extreme ends of the leadscrew cannot be that worn? Those are the places to check with your sheet metal gauges.

If anything, err on the side of tighter rather than looser. Your present problem appears to be one of too much clearance.

Howard

While you have got the top slide to bits, you might be able to incorporate some sort of antibacklash nut system, if there is room.

You have been unlucky with the size and pitch, 12mm TR is normally 3mm pitch, leadscrew material and nuts are easy to come by. I have recently managed to get hold of 2.5 TR inserts, but they are16 size and our leadscrews are about 23mm diameter. I do think that 11 size 2.5 TR are also available from the same Chinese source, but even these small ones would have to be butchered to manage a 12mm thread.

If you went the 3m pitch way, you would have to change the dial engraving, I have done that.

Edited By old mart on 29/07/2022 17:53:38

You should have on the front of the machine as mine, a symbol etched in to the information panel on the front of the headstock 'ISO METRIC'

Just read the opening post again and realised I did the same thread last week but RH for a Kitty planer 12 x 2.5 Trapezoidal -- this was a clean up job to free the thread.

Ground the tool freehand using a vernier protractor for the angles, got that correct then reduced the end to make it the right width, the tool holder has been around for years.

Hi All,

I've realised from some of the replies and re-reading my second post that I haven't explained very clearly. There is no wear in the crosslide screw at the extreme ends. The reason that I can't make the tool to fit the screw is as Hopper says, the tool end width must be narrower than the flat at the root of the crosslide thread to give clearance when the threads mate.

I have now made gauges from sheet and it turns out that the thread is Acme (29 Deg.). I have mounted this "Vee plate" gauge onto a height gauge and used it to measure the thread depth, which measures at 0.02mm over the calculated value of 1.5mm (this is about the accuracy tolerance of my height gauge). The tool point width calculates at 0.8mm. so just got to make the tool and get cutting.

Thanks for the feed back.

Sean.

Hi Sean,

I am in a similar situation to you, I recently purchased a Boxford STS. The original cross-slide nut/screw had significant wear and the previous owner replaced it with a homemade screw/nut but machined a standard 60 degree 2.5 pitch thread. It seems to do the job quite well but I would like to return it to factory spec if possible.

I too also assumed a TR thread and was about to purchase a TR12x2.5 tap/die set from China until I saw this post.

How did you end up going with this?

Cheers,

Jeremy

There's one on eBay at the mo - but it's a bit pricey!

https://www.ebay.co.uk/itm/284901951789?hash=item42557ac92d:g:3eEAAOSwwcliHOH4&amdata=enc%3AAQAHAAAAoEbt7oxuCRH9lwNgCutP4P8tJ3E4zNEYh5v93eaKEnj9NmYi6I9bKyWTo5KxeQQ3ps7hwQMRsmy3BmcTQ6LOaiENP1W0pOjxFrrcv8vJHMkpcFNJxirmltXhMGK6ljmDnQ8Z0HwltjK8BSPiSKlCQMYsKNeh4XaMy9P2Tk6gkfewtRnfCpM%2B7I%2BZaKFESxuHxSBctu3zcul6uAwzHO9O99U%3D%7Ctkp%3ABk9SR6bxwZa0YQ

Did Boxford really use Brass for the original nuts as per eBay ad?

Tony

If you want to know for sure just set up your screw on your surface grinder and grind the last turn of thread on it down to half diameter to expose the full profile. You can then set a camera up directly above it, take a zoomed-in photo and then open the pic on your pc and use some software to measure the angle.

That last 2.5mm of thread is of little practical use to you anyway.

.

Given that the ‘Description’ clearly states “Not direct from Boxford but manufactured to the exact same dimensions and specifications.” … One would hope so.

… If not, then Ostia deserves a good thrashing !!

MichaelG.

On a machine subjected to industrial use for 35+ years, how critical is the difference between 29 and 30 deg.?

I saw that one! Yes quite expensive, especially after currency conversion and shipping to New Zealand.

What would you have expected it to be made of?

The original one I have definitely looks to be brass or maybe bronze?

As an engineer I would expect Phosphor Bronze or similar for its wear properties certainly not brass😉

Tony