Member postings for John P

Have a look on the https://www.chronos.ltd.uk/ site here Soba Chronos Product Code: 145056

and also Chronos Product Code: K11100M . The Soba is probably the better of the two.

John

The lug shown in the photo ,the only function of this is to provide enough
material for one of the tapped holes that hold the lead screw nut,
the two places marked on your photo here are the only adjustment
for the vertical clearance of the table if you remove those strips
there will most probably be some shim material between the
strips and the table ,there should be some reference to this in the build notes
that i believe that you have.

John

Posted by

I dont know if you are around but I’m still having significant problems with the table wobbling by a couple of thou, The good news is that turning the table the right way round has ensured squareness and there is very very little play in the horizontal plane, once the gibs are tightened.

But there is play in the vertical plane. With the table central, I can quite easily lift it by a couple of thou using my fingers under one end. And if I turn the handwheel it has the same effect.

Most slideways are dovetail, so secure a table in the horizontal and vertical plane at the same time. But the Dore Westbury is not, the only securing force from the gibs is in the horizontal plane. I find it difficult to believe that this isn’t accounted for in the design somehow. I am wondering if I am missing shims somewhere or something?

if you have any thoughts I’d be glad of them (or indeed anybody else!)

Cheers

The adjustment should be by shimming under the two flat strips fitted to the underside of the table,it may well be that when you remove them the edges that engage under the slideway strips may have worn ,likewise the underside of those two strips may also be worn .It is fortunate that the design of the Dore westbury these parts can be renewed just by replacing the strips in the same way as when the machine was made providing the sliding surfaces of the table are in good order this should be a straightforward procedure although the shimming may be a tedious operation ,as far as i can remember the strips are imperial sizes.

Seeing as you have turned around the table it may have been adjusted for when it was the other way round and just needs some adjustment.

John

Edited By John P on 05/11/2021 21:16:15

Posted by DC31k 04/11/2021 15:03:01

As a general observation (i.e. I have seen it enough now to be bothered to ask

the question), why is it that you produce a metric threading chart that includes

pitches that are never used and are entirely non-standard (e.g. 2.25mm,

3.75mm, 1.3mm, 1.1mm)? I have seen it with metric thread dial indicator charts

as well.

How many imperial threading charts do we see that include 6 1/2 tpi or 15tpi or

9 1/2 tpi?
-------------------------------------------------------------

The chart replicates all of the metric pitches in the Myford
handbook and a few extra , the Myford chart only goes to 3.5 mm.

I suppose if i had missed any of these out someone else
would have pointed out that the chart would have been incomplete.

The 3.75 came out as i had transposed some gears when setting
up ,as it came up as exactly 3.75 i just left it in the chart.

As a matter of interest my Warco lathe has on its screwcutting chart
4 3/4, 5 1/2, 5 3/4 , 9 1/2, 11 1/2, 13 1/2 and 15 tpi and also includes
2.25 mm and 0.313, 0.625, 0.875 module.

As i said here ,
Anyway the chart is there for you to use if you wish,
if it is of no use to you ignore it.

John

Posted by Pete Rimmer 02/11/2021 16:36:19

My lathe uses 16DP gears except for the metric set which utilises 127 tooth.

They are 32DP. I expect that a Myford 7 would get away with 40DP conversion

gears but 32DP would do just as well being ever so slightly finer than 0.8MOD.

---------------------------------------------------

The gear chart for the 127/60 gears i find much
easier to use that the pair of 21 tooth gears that
i have had for as long as i have had the Myford.
Since the 60 and 127 gears are always in the same
places setting up only requires changing perhaps
one or two gears,for instance to change from
.075 to 1.00 and1.25 mm pitch only requires
a change on the tumbler from 30 to 40 and 50 tooth
and reposition the banjo,i only use a few pitches
anyway mostly 20 tpi 1 mm and .75 mm and since
the half nuts have to remain closed for metric cutting
i use a mandrel handle so it is useful to be able to
keep the gear change door closed.

I nearly made a 20 dp 127 gear but realised quite
early on that fitting and using it may turn out to be
a real problem ,i doubt if you would be able to do the
full range of metric pitches using one , if you know different
i am sure you will let me know.

Anyway the chart is there for you to use if you wish, it
would only suit .8 mod or 32 dp .All of the pitches
have been set up on my machine so they will fit in
some are a tight squeeze even with .8 mod gears.

John

Posted by SillyOldDuffer 01/11/2021 11:26:17

not by rice-farmers in a shed!
---------------------------------------------
Don't appear to even have a shed ,well not in the first part.

https://www.youtube.com/watch?v=S6QmvOU_syM

John

The problem when using a 127 gear on a Myford 7 changewheel machine
is simply the size of the gear if you have it as 20 DP,the lead screw centre
distance to tumbler stud = 3.785" and is equal to the size od a 149
tooth gear .As a pair of gears in line maximum that can be fitted in is a
20 tooth and 127 tooth .

As Michael G pointed out ,One great proponent of the 127 tooth gear was
Martin Cleeve … but he, very wisely, used a reduced pitch on his ML7.

I have gone down this same route using a 0.8 module 127 and 60 tooth
gear with the exceptions of 2 pitches the rest can be done using only
the remaining standard changwheel set supplied with the machine
using the standard banjo and being able to shut the cover.

Here is the screw cutting chart a horizontal version is in the album
"gears" as this is easier to print out in nearly A4.

John

Posted by Henry Bainbridge 31/10/2021 14:21:36

Hey! How did you know I don't have a lathe? The pedant in my
says actually I have owned and operated a lathe every day
of my working life for the last 18 years, albeit a disc mastering
lathe, so not quite the same thing I grant you, but still.
You are right though, I don't have a lathe yet.

-------------------------------------------------------------

Before answering most posts on here i generally look back through
the posters history as this can sometimes help with giving a reasonable
answer ,most half decent engineer's will do their homework,
of course there are exceptions one of the posters who replied to you in
this thread was giving someone some chapter and verse advice
on how the set the dovetail gibs on his milling machine on a machine
that had square slide ways ,clearly would you take advice from
someone with such a sloppy approach.

Getting back "How did you know"

Your posting here 28/10/2021 19:33:03

The relevant bit i have put in brackets.

Hi there, just posting so I can see classifieds.
I will stop by again (if I get a lathe), and I have
some genuine queries

John

This green heat joint belting 5 mm dia is at its limit here driving
the internal grinding spindle at 28,000 rpm you can just see the joint frozen
in the flash on the top side ,the normal tension is set i think at 8% i
increased this to 15% to get the spindle to drive reliably at just
over 31,000 rpm ,its tough stuff this belting.

John

Posted by Michael Gilligan 29/10/2021 21:37:33

Jesse Ramsden described how to make a screw thread and use it as a
hob to make a large wormwheel … in sufficient detail for me to know
that concept works.

Hi Michael,

Whilst the OP was just getting enough postings just to look at the classifieds
and has yet to get a lathe and asked the opening question.

Various respondents have pointed to the early names of pioneers
of the industrial revolution.
If you look at this video

https://www.youtube.com/watch?v=yzMU8rH4PN8

was Jesse Ramsden inventing anything or just
re-inventing the wheel and much the same could be said for the others
since many the skills and techniques had been invented thousands
of years ago and i guess nobody really knows by who.

I suppose the only thing the early pioneers did was to get out of their
armchairs and actually get on with something, some on this forum
could learn a few things by doing the same.

I suppose i would say to the OP when you get your lathe and have used it
for a while you will have the opportunity to find out some of these things
yourself instead of popular pastime of just reading it out of a book.

John

Posted by Henry Bainbridge 29/10/2021 17:47:16

I am not sure what you mean by incorrect. I posed a recursive question
deliberately because AFAIK there are some parts of a lathe
that can only be made by a lathe and I wondered how that can be.
I take your point though, so for the sake of argument let's say the
thought experiment is about how some tools are recursive in nature, and
that being so, how accuracy comes about.

-------------------------------------------------------------

Perhaps a poor choice of words on my part ,but if if you take the
opening statement of:-

Is it possible to machine a lathe more accurate than the one you
machine it on? If so, how?

If you mean "make" as in machine then the answer would be no.
It may well be that some parts of a lathe can be made on a lathe
but i doubt if many of the the parts would finished on one , you only have to
look any lathe on sale just about every surface is finish ground and
with that comes the accuracy of the machine.

As far as being able to make another lathe there is simply not enough machining
capacity with a lathe to be able to make another one, but you can use a lathe
to make other machine tools to assist in making the lathe.

There is no doubt if the ingenuity of some of these early pioneers of the
industrial age were up against it . I just wonder how many others who perhaps
were attempting much the same but just simply fell by the wayside and those
who succeeded just were in the right place at the right time and had the
good luck to see it through.

Perhaps an example of this can be seen in this interview,
Sir Tom Sopwith interview with Raymond Baxter.
https://www.youtube.com/watch?v=4y0rBfJ8VGw

In the closing question Sir Tom was asked

At 96 a lifetime of amazing achievements behind you What do you attribute
your success?

He responded with "Pure luck"

Perhaps getting back to the thread in general if you look at some of the answers
they are all on the theoretical mostly what has been read in books, the
complete lack of documented and practical examples by respondents on
here can lead you to only one conclusion .

John

"Is it possible to machine a lathe more accurate than the one you machine it on If so, how?"

I suppose the question here is posed incorrectly and perhaps should be.
Is it possible to produce a machine that will produce more accurate work
that the machine 's that it was made on.

If that is so then it is here is one

This cylindrical grinder was made in just that way ,the cylindrical square here
held between centres is within 1 um along the entire length and stands
square on a surface plate to within the thickness of 1 um clock gauge
indicator needle in any 4 places around the diameter.

As for the how, ME have had the construction article for the last 7+ years
or so if they haven't lost it again.

John

Hi ,

Sound as if you are having similar problems to the Myford lathe in this posting https://www.model-engineer.co.uk/forums/postings.asp?th=173467 , all routes lead back to RGD.

The conclusion  was  on this posting  was

"An update, Myford suggested I return the screw and nut for appraisal, which I did. They detected tightness and suggested it was borderline on tolerance and sent a replacement "original" Myford screw and nut which I fitted today. The replacement is significantly better but lacks the silky smooth action of the metric screw and nut. I can't get it down to virtually nil backlash either.

I am reluctant to concede that it may bed in as I feel it should work out of the box."

Perhaps they just stuck the old one back on the shelf  for re sale!

I don't bother with such things now i just make my own  they work every time that way.

John

Edited By John P on 28/10/2021 08:32:44

Hi Steve,

Yes those three holes , it would be as well to assemble the parts as suggested earlier just to check the positioning before drilling the holes in the end of the table as if any of the the existing positioning is off it will lead to an error.

(because the ****** person who built the mill) as you had written earlier had obviously got some things wrong like having the table the wrong way round.

John

Hi Steve,

just as a postcript to the previous posting that i made be careful about following the drawings as it appears from the third photo down on your posting at 10:34:11 today that the 3 holes that hold the leadscrew nut may also not be in the correct position , that extra little cast in lug on the XY slide is for that third screw ,as far as i can remember the tapped hole sits more to the left and a little higher in that position.Would be worth checking before drilling any holes.

John

Posted by Steve 355 27/10/2021 14:07:24

Now I’ve just got to work out how to drill accurate holes in the end of that table.

Luckily I have a big pillar drill!

The easiest way to do this is to remove the XY slide from the machine,
lay the table upside down on a bench fit the X leadscrew nut in position
on the XY slide fit the XY slide on the table fit and adjust the gib in place ,
screw in the leadscrew and end bracket as far in towards the nut as it
will go ,if you view down alongside the table the leadscrew should be
visable and it will be easy to see if the leadscrew is parallel with the
slideways then looking down from the top likewise the leadscrew
will be in line with the slide bars.
Probably easiest to just fix the end bracket to the table with a dab of epoxy
glue let it set ,make up a long centre punch that fits in the holes of
the end bracket ,if the glue will hold you can carefully traverse the
XY slide along the table before marking the 2 hole positions to test
the position.
When satisfied with the positioning use the punch to mark the
hole positions drill and tap for the 1/4 bsw fixing screws if they are
still this size they are on mine.

John

Posted by Steve 355 27/10/2021 10:34:11

Is this statement true? :- It doesn’t matter if the milling table is not square to
the base of the mill (within reason). The milling cutter is round. What matters
is that the X, Y and Z axes run perpendicular. Tramming ensures the Z axis
is perpendicular. The X and Y axis should be perpendicular by
manufacture of the table.

Yes it is true , except for the last part after i had built my Dore westbury
the squareness of the X and Y was off by few thousanth's of an inch,
it is possible to re-machine the Dore westbury XY cross slide on a Myford 7
lathe cross slide because this is how i corrected mine.

There is little point to having the tee slots in line with the travel of the table
because of, 1 the longitudinal slots at each end are too short in all probability
to be able to mount any additional accessories (vice) without using some of the
other slots in either side of the table ,2 the tee slots in a Dore westbury are cast
in and not machined and are useless as a reference unless reworked
for that purpose.

As it is the 1st photo that you have posted showing the underside of the
table the dowels are in the correct slideway/ guide ,as you have surmised the table
has been fitted the wrong way round, however fitting the table as in the last photo
which is the correct way round also puts the guiding slide with the dowels on the
correct side, it is worth noting that if you remove either of the 2 guide strips from the
underside of the table they may be shimmed as this is the normal method on these
machines to control the table lift /clearance.

John

Edited By John P on 27/10/2021 13:35:41

If the edge of the table is not parallel to the direction of travel which seems to be what you are saying here, it is not anything to do with the slide way strip that you have shown in the photo with the caliper reading of 2.973" .The guide strip that is screwed to the underside of the table the one the gib strip runs on controls the position of the table ,you would need to check that the guiding edges of this strip are in line with table edge.

In any event apart from from a nuisance does not affect the operation of the machine in any way ,for what it is worth you would probably need to replace the strip rather than try to reposition the countersunk holes any distortion to the existing strip is likely to lead to more problems.

John

If you have half hour spare watch this video on building a home made lathe.

https://www.youtube.com/watch?v=z67A3Myy6XM

John

That looks as if it is ok as noted previously by Journeyman , have you checked also the gib strip adjustment on the Y axis slide way, try the test with the Y axis lock tightened.

John