Cutting 1.5" x 8tpi thread on a Metric Boxford.

I took delivery of my new nose mount ER32 collet chuck and collets this morning. I can see these will be a great addition to my tool box.

I know 2MT ER chucks can be purchased but I thought it may be nice to make my own. A 2MT to 1.5"x8tpi adaptor will allow me to use the chuck in the tailstock.

Is this possible on a Metric Boxford lathe? I have a full set of Metric change wheels. I guess, If it is at all possible, I will need some conversion gears?

John

John, I don't have all the info you need but the answer is I am sure yes, however you will need a 127 or possible a 63 tooth gear to make the reverse conversion to an imperial thread.

What model is your lathe? I recently purchased a metric boxford but do not have it running yet, I do have the full instructions so will have a look at what's recommended and either post the info or pm you.

John

PS mine is an 11-30 lathe

Edited By JohnF on 16/08/2014 17:38:24

Hi JohnF, It's a 5" Boxford CUD MKIII.

It would be nice to have the option to cut imperial threads. For smaller stuff I will carry on as normal with taps and dies.

John

Edited By John Bromley on 16/08/2014 17:50:28

try this

Changewheels and English/metric and metric/English conversions
"English" threading Lathes with an 8 t.p.i. leadscrew and changewheels for screwcutting (i.e. without a screwcutting Gearbox) were supplied with the following changewheels when they left the factory: *16, 24, 36, 40, 44, 46, 48, 52, 54, 56, 60, *80, *72/18 compound, *80 idler (with boss). (* gears on machine as dispatched from factory for standard feeds)
To convert a non-gearbox English-specification lathe to cut metric threads the following gears are needed: 20, 100, 127/100 combination
In addition, to cut the following five pitches extra gears are required as follows: 0.45 mm = 18t gear, 0.55 mm = 22 t gear, 0.65 mm = 26 t gear, 0.7 mm and 3.5 mm = 28t gear

Metric Threading Lathes with a 3 mm pitch leadscrew and changewheels for screwcutting (i.e. without a screwcutting gearbox): were supplied with the following gears as standard. *16, 24, 28, 30, 36, 40, 44, 48, 52, 56, 60, *80, *72/18 compound, *54/18 compound, *80 idler (with boss)
(* gears on machine as dispatched from factory for standard feeds)
To convert a non-gearbox Metric-leadscrew lathe to cut English threads the following gears are needed: 18, 22, 26, 38, 54, 64, 88, 135/127 compound, 48/24 compound.

"English" threading Lathes with a screwcutting gearbox had a standard ex-factory drive train consisting of: 20t, 40t, 56t and an 80t idler. To convert this gearbox to cut Metric threads the following gears are needed: 24, 26, 28, 32, 36, 44, 48, 127/100 compound

Metric threading lathe with a screwcutting gearbox had a standard ex-factory drive train consisting of: 20t, 45t, 50t and an 80t idler. To convert this gearbox to cut English threads the following gears are needed: 38, 40, 44, 52, 56 and a 135/127 compound.

Even without the 127 ger you may be able to find a combination of gears that gives a close enough approximation. There are several programs around the web that work out the options.

Hi John,
I agree with Bazyle's comments. The program I use is nthreadsp.exe available here While finding the URL for you I noticed that the page also contains a program called BoxftrhreadP which is for use with Boxfords with a screwcutting gearbox. My lathe has a screwcutting gearbox so to make best use of nthreadsp.exe I worked out all the ratios produced by the gearbox from the table of thread cutting data supplied with the lathe. From this I created a list of EFFECTIVE PITCHES available by multiplying the true leadscrew pitch by each ratio available from the gearbox. I then ran nthreads.exe and trying it with each of the effective pitch values to see which combination gave the nearest value to the pitch I required. I suspect the version for the Boxford may do this for you.

Les.

Hello John,

Your question seems to have run into the sand. Just out of interest I tried the links listed by Les Jones above; one was no longer accessible and the other was (to me at least) incomprehensible.

I don't know what change wheels you have available but I can offer two practical gearing arrangements that will do what you want. I don't claim authorship, these figures come straight out of Martin Cleeve's excellent book 'Screw cutting in the lathe' Workshop Practice Series #3

They are:- Stud gear 50----Idler----40=55------65 as screw gear (the = sign shows the gears linked on the same intermediate stud) That will be accurate to -1 part in 1650

The alternative arrangement is Stud gear 38---idler-----40=50-------45 as screw gear. This is accurate to -1 part in 380

In both examples, screw gear is the input to the gearbox.

Both will be more than sufficient to cut an 8tpi thread for your job to decent accuracy. They require the gearbox to be set to 3 mm pitch to match your lead screw pitch, in effect simulating a non-gearbox machine, and the usual caveat applies to keep the clasp nuts closed throughoit the whole process, beginning to end.

I hope that helps you

Regards Brian

Edited By Brian Wood on 18/08/2014 09:45:12

.

Brian,

Maybe a temporary glitch ?

... Links appear to work O.K.

MichaelG.

Hello Michael,

I have found in the past that some of the magic links for information in this sort of category is often difficult or clanky to follow even when they work.

I like to understand the logic which was why I went to the book for these answers. I think the OP just wanted a simple answer to get his job done this time, he can pursue the links later for the future.

Regards Brian

Thanks for the input chaps, I tried the nthreadsp.exe program and found it very easy to get on with.

Sadly the change wheels on my CUD will only go in certain places, the only gears I can compound are the ones Boxford deem necessary to cut Metric threads, the 54/18 and 72/18 pairs. The rest are designed to be mounted individually on keyed mandrels, either in the stud gear or lead screw positions.

Therefore I intend to make a complete 2MT Collet chuck. The closing nut thread on an ER chuck being 40x1.5mm will be easy with a 3mm lead screw, as I can engage the half nuts at any position.

Many thanks again.

John

.

May also be handy info :- **LINK**

Nick

For £14 you could buy one 2MT Chuck adaptor I have a couple of them and they are accurate and quite nicely finished.

Paul