Lathe change wheels

[ScrumpyParticipant @scrumpy]

hi in the cabinet of my Boxford lathe was a full set of change wheels these matched the change wheel plate on the front of the lathe

But there were two extras fixed together one with 100 teeth and one with 137 do they belong with this lathe the colour was the same if so we're would I find a screw cutting chart . thanks

[ScrumpyParticipant @scrumpy]

[mark smith 20Participant @marksmith20]

Hi, Are you sure that isnt 100/127 , this is the compound changewheel that allows a good number of metric threads to be cut on an imperial lathe. They are quite expensive to buy for a boxford / southbend / logan lathe.

Edited By mark smith 20 on 18/01/2017 17:01:32

[SaxalbyParticipant @saxalby]

Here is the cart for cutting metric threads with the 100/127 compound gear

[ScrumpyParticipant @scrumpy]

Hi After counting the teeth it is 127 the reason I got it wrong was on the gear is marked DEH3656-214 followed by G4 -B29 TF2 P29 and 137 which I assumed was the teeth on that gear .

How many gears make up a full set as I have 8 plus this double one or should there be more thanks

[mark smith 20Participant @marksmith20]

All the info is here which is from the lathes.co.uk website.

[RobboParticipant @robbo]

This page from a full copy of "Know Your Lathe" shows the various standard changewheel sets supplied with various machines.

Thought the whole thing might be a useful "takeaway" for readers.

Your model B will be the first set.

Edited By Robbo on 18/01/2017 20:02:52

[ScrumpyParticipant @scrumpy]

Thanks for all your help I feel proud to think that the lathe from 1951/2 will soon be back doing what it was intended for and being so complete

[AjohnwParticipant @ajohnw51620]

Posted by Saxalby on 18/01/2017 17:49:59:

Here is the cart for cutting metric threads with the 100/127 compound gear

That's interesting. I've heard comments in the past that the smallest gear that will mesh with the 100T is 40T so the 56 must mesh with that and the small ones with the 127. Actual 40T may be too small. So if the above chart works it should show the compound as 100 – 127.

Thanks. I've just checked one of the values. It does work. 56 stops on the leadscrew gear driiven by the 100 and the other drives the 127. So changing one gear can produce all metric pitches even the ones that are out of the ISO spec.

It doesn't work out so nicely with the 100/127 the other way round. Silly me who knows it's best to check anything picked up from the web.

John

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[BazyleParticipant @bazyle]

The charts given above are for a gearbox type ie model A. Does anyone have it for a model B? I checked my book and it doesn't but I also don't see a lest of the gears supplied as shown above so there must be other versions of the book.

[RobboParticipant @robbo]

Bazyle

Is this the one you mean?

[BazyleParticipant @bazyle]

Thanks Robbo. My book has a fig 187 for 3mm leadscrew. Book version is "tenth impression 1981"

[AjohnwParticipant @ajohnw51620]

Posted by Bazyle on 19/01/2017 23:08:55:

The charts given above are for a gearbox type ie model A. Does anyone have it for a model B? I checked my book and it doesn't but I also don't see a lest of the gears supplied as shown above so there must be other versions of the book.

I can't easily copy them but if you have the parts list off the yahoo group change gears run from 34 to 49 and there is another group including the 100/127 that runs from 213 to 221 but part 217 is a pin. That looks to provide the missing gears.

I've only glanced through them quickly but it would make sense to group the extra gears with the 100/127. Maybe the first group provide imperial pitches on a none gearbox lathe.

I might use my 100/127 now. The only catch I can see is loosing the finest feed on 1mm pitch as 25.4tpi is coarser then 32. There may be others but that's not too bad. It also looks like it's worth having the gearbox as changing pitch is pretty simple.

To be honest I sometimes cut close in TPI and then run a metric chaser over it. So far it's been unusual for me to cut metric as the sizes I've needed can be done with a die.

John

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[John Stevenson 1Participant @johnstevenson1]

Posted by Ajohnw on 19/01/2017 17:44:17:

It doesn't work out so nicely with the 100/127 the other way round. Silly me who knows it's best to check anything picked up from the web.

John

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.

Especially if it was you that posted it

[AjohnwParticipant @ajohnw51620]

I took notice of a web comment that the 100/127 could only mesh with a 40 tooth plus gear. Suspect it's 48T actually.

I'm fully aware that the web can be a source of duff info.

John

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[RobboParticipant @robbo]

Posted by Bazyle on 19/01/2017 23:37:18:

Thanks Robbo. My book has a fig 187 for 3mm leadscrew. Book version is "tenth impression 1981"

Sorry Bazyle, forgot to reply earlier

My "book" is a bit of a composite. The section that chart came from is different from the usual "Know Your Lathe".

Its headed "SCREWCUTTING" "Special Data and Charts" and as well as the two I have reproduced in this thread includes some charts for Hercus Metric/Imperial conversion as well as Boxford charts.

[BazyleParticipant @bazyle]

There must be loads of people with the book who got annoyed at the omission pre web alternative sources.

As an aside from Boxford but on general topic I have been looking at the screwcutting plate for the Harrison M300, The great thing about this lathe is that the QCGB cover metric as well as imperial on the selectors – so convenient.
I have looked at switching in the 127 as an add on box and it gets a bit tricky.

Then I read a comment that the M300 either metric or imperial does the other type only approximately though rather well. Initial investigation shows it is rather clever and complex but the largest gear it uses is 50 and none of the usual 63 etc approximations.
Now to see whether I can make an equivalent Boxford size for less than the £750 starting price of one on ebay today.

Anyway those of us without a nice M300 (or the Colchester equivalent) but with a 127 on our plain lathe can be smug that we are cutting more accurate metrics than they are.

[RobboParticipant @robbo]

Bazyle

Time for a trip to Specsavers?

The 127/100 combi brought to my attention by ebay was £175 plus postage. Still far too much though.

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