Member postings for John P

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https://www.youtube.com/watch?v=DVLXsq7pi9Y&t=12s

John

Posted by Howard Lewis 28/07/2020 21:15:43
I made, if that is the right word, a granite surface plate for The WaterWorks Museum.
It was "floated" on a bed of wet plaster, on a sturdy (2" angle iron) frame, fitted with
levelling screws. In place on its bespoke stand, the table was levelled in both planes
before use. The stand is not moved around, but kept in one place. It is also kept
covered when not in use.
My surface plate is never moved.

Refering to the FAQ , question 12 on the site below
Mounting surface plates in the way described above is not recommended
The also point out that levelling is not necessary ,i suppose they would know .
Probably the reason the plate should not be stored in any other way
than on these three points.

https://www.starrett.com/precision-granite/precision-granite-faq

My own stand seen here in an earlier photo is mounted on the
three indicated marks on the underside,the mounting points
are on the two cross bars the four uprights at the corners
are a safety to prevent the plate from moving out of position
but do not touch the plate.

John

I have my surface plate mounted on a movable trolley made from
square steel tube,the height above the floor is about 36 inches
which suits me.No problems with stability .
A couple of loose pieces of square tube allows the cover to sit
alongside the plate as a temporary storage for parts etc.

The space underneath has 5 plywood draws for storage,when
not in use the top is fitted back on and the tubes are stored
inside the long top top tube of the stand.
The plate is 12 x 18 inch.

John

Hi John

There are some hobs on this site here ,i have never bought from them so have
no idea if they are any good.
Beware of e bay sales of hobs in case you end up
with one that has been sharpened many time and is at the end of its life.

www.aliexpress.com/store/group/Gear-hob/1503094_510830882.html?spm=2114.12010108.0.0.30fe2a2eMkcaRV

Some info on its way to you soon.
John

Hi John

The Warco machine that i have is an A2F ,Warco no longer sell these,
Chester still do as the 830 VS so you could compare with yours.
They are not all that different mine has an R8 spindle 30 x 8 inch table
i think the motor is 1.5 kw.
I use the hobs that were sold by Arc euro,at the time i started with this
hobbing they had only just started to sell them.Very good cutting tools
its a shame they no longer sell them,i think as the stock run down they
just never got any more ,i think i bought one of the last in around 2015
this 20 DP Myford changewheel size hob is about 50 mm diameter
most of the hobs they sold were around 25 mm dia.
I have under way and for some time a modified version of the hob
relieving attachment that was in MEW 57 page 37 ,some of the
parts here are seen in the photo along with the 20 DP hob as above
shown in the foreground on the left.
This is intended as a part cnc/mechanical endeavour where the cnc
part just provides some automation to the proceedings,there is still
quite a way to go before it is up and running.

I don't hob gears above 1.25 mod / 20dp as i find most of the stuff
i make suits these sizes.

John

Hi John

The photo here shows the encoder on the mounting plate,
in the box is a 500 line encoder wheel geared at 2:1 and reading
on the two channels would be 4000 ppr.
Seen here this 2000 line encoder driven in the same way would
have 16,000 ppr,
With this sort of setup it is very easy to get any number of pulses
that you need.
I have had this system operational now for 10 years and cut
hundreds of gears for my own use.You would need to contact
Richard Bartlett to find out if he still has these and the cost .
I will send you a PM with the contact details as this may be
his home number and i don't wish to put this here.
This Syncron system is only the electronics for the hobber
the power supply and stepper motor driver needs to be obtained
additionally as does all of the mechanical parts.

John

Hi

In reply to your opening post.

I have an optical encoder fitted on the quill of my Warco mill when it is set
up for hobbing.I made a split collar that clamps around the spindle turned
in situ that remains in place all of the time ,the drive gear is a close fit on
this collar and secured with 3 screws. You would of course loose the access
to the spanner flats or maybe you have already done so from your posting
of 13/05/2020

(Would it be a good idea to turn up a steel ring and loctite it in place?)

The photo here shows the encoder clamped around the column and gear
being hobbed.The original article appeared in MEW 193 Sept 2012 .
The hobbing unit was designed by Richard Bartlett who makes the Compucut
cnc system ,when i enquired on behalf of another forum member he
still had about 12 of these units in pcb form available.I still have all of this
information available if you are interested.

John

Hi Phil

I'm also on the south coast ,still interested in model aircraft but
have not been flying for 15 years,here is the photo of the last
3 models that i built and have never flown and may not do so now.
The 2 either side are identical and based on a Lobbit design
that was in the GTBA papers, the middle delta was based on
on a Finecraft delta i think the Firefly ,modellers of a certain age
will remember the Chris Foss team flying these in formation
at the Sandown park show.
All these models are for Gas turbine power ,the one on the right
has a Shreckling type engine runs at about 100,000 rpm with
only about 6 lb thrust not much by todays standards but probably
enough to fly.The one on the left has a Super Tigre 60 engine
which i had fitted to test fly the model.
The delta has no engine at the moment i have some parts made
for a Kj 66 style engine here in the photo is milled from the solid
compressor wheel on the balancing machine.
I suppose my only claim to fame was with this Ducted fan H.S.Hawk,
bit of a grainy photo from a print won a first place at the Shuttleworth
scale rally in 1982 ,i had left before the end of the show so they had
to send me the trophy ,sadly no cheque .

John

Posted by Andrew Johnston 13/07/2020 22:13:49

Quite so, but even measuring a cutter diameter is non-trivial. In theory
an even number of flutes can be measured with a standard micrometer.
But it's not easy to determine if the flutes being measured are precisely
in line with the measurement axis. An odd number of flutes is more
of a problem. Of course one can buy flute micrometers for 3
and 5-flute cutters. A quick search found a Mitutoyo 3-flute
micrometer on sale at the bargain price of £224, plus VAT of course!

Hi Andrew

I use much simpler methods for doing this as seen here in the photo.
With the cutter mounted in a vee block the relative height of the shank
and the highest point of any cutting edge enables the cutter diameter
to be calculated.

I would normally do this at the time the cutter is sharpened as the
cutter can be rotated on the machine about its center and measured in
this way , if a specific size is required since the diameter is known it
is a simple matter to regrind to the required size.

The real fun starts if a tapered cutter is ground since there is no reference
diameter, a small test piece is cut to work out the relative center distance
at the full cutter depth.This pair of 6 mm cutters were reground at approx
3 deg taper and 1 mm radius edge to cut the vanes on this turbine
compressor wheel.

John

Hi
Contained withing this thread from 2012 by Phil W
"Pneumatic brake for CNC rotary table"
will lead you to his site here which
has a circuit for a 9 cylinder version of
what you need .

http://philsradial.blogspot.com/2013/02/glowplug-driver.html

Don't Know if this will be of any use to you but may be of some use

in a modified form.

John

Continued
The internal grinding spindle assembly mounts to the surface grinding
spindle housing with 4 bolts and a clamp and is driven from the spindle.
The 3rd photo here shows the workhead at the far end of the table here
also having the 2 morse taper being ground in situ.The internal grinding
spindle swings up as you can see by the shape of the mounting bracket.
For sizes above 10mm i use bore gauges as these are relatively long
and would foul a fixed spindle ,the mechanism has a quick release and
uses spring pressure to hold providing a constant force for a repeatable
repositioning. The work head mounts on a column similar to a Quorn
grinding machine but much larger and is made in such a way that the relative
centerline relative to the table has eight different positions.As the head can
swing 360 deg and can point up of down by about 30 deg with
work mounted it is possible to get an out of bounds setup ,to some extent
having this arrangement makes this less likely.
Initially i used water based coolant but got fed up fairly quickly about the mess
with this and having to take the parts off the table to clean them,leaving the machine
after use resulted in little black spots after about a day ,rust ! ,that all had to go.
I use neat grinding oil now excelcut 433 is about a 10 grade oil and runs away
as fast as paraffin ,no rust problems no tramp oil no wheel loading and much
more pleasant to use.
Keeping it clean (the oil) with only a 15 litre tank presented a whole new load
of problems,eventually solved by controlling the way the oil runs off the
machine ,through a fine mesh filter to collect the large debris ,slowing the
passage of the oil down through a magnet array ,then through a centrifuge
of about 5000g finally into 2 tanks the lower one having a pumped filter
system with throw away filters.

The basic specification of the machine
Surface grinding
14 X 5 inches ( maximum traverse length 18 inches)
Maximum height 5 inch grinding wheel to table 9.500 inches.

Cylindrical grinding
14 inch between centres
Maximum diameter between centres 6.500 inches, the swiveling sub table allows
around 7 deg taper in either direction .
Grinding wheel sizes 4 inch to 8 inch dia 1/4 to 3/4 inch wide variable speed
spindle from around 2,000 to 4,700 rpm , internal spindle to 31,000 rpm.
It's been an interesting project that will probably never be finished in as
much as the list of things that i need to complete gets shorter but the
list of thing that i would like to make grows ever longer .
All about time i suppose.

John

Posted by Joseph Noci 1 03/06/2020 07:06:50

John, could you explain your setup in more detail please? Interested as to how that setup works.

How did you set over the job on the magnetic chuck to the MT angle, bearing in mind the relationship
to the sliding axis? How DOES the sliding axis work? Does the mag-chuck slide, or the grinding
head, ie, what moves to make the abrasive wheel move in and out of the job? Can't see from the
photo - is that a commercial grinder or a shop built one ( the whole machine, not just the grinding head)
Maybe some more photos of the whole thing from different angles.

Looks interesting!

Hi Joe

It is easier to explain if you view the 1st photo ,the machine is a home
built fabricated machine and initially was styled using the basic dimensions
of a Myford MG 12 grinder but at about 2/3ds size.From this the table
moves left/right and the grinding head fore and aft just the same as a normal
cylindrical grinder.The protruding shaft housing just above and behind the
tail stock is the shaft used for surface grinding,for this the the head and
tail stocks are removed along with the swiveling sub table the head swivels
round 90 deg and then the machine can be used as a surface grinder
as seen in the 2nd photo.In front of the table there are 2 micrometer
adjustments for the stop bar,the machine has a 2 axis dro the table has a
5 um scale the crossfeed a 1um scale, to set the angle for the morse taper
a true running test bar was mounted on the nose of the rotary table and the
table traverse set to 5.125 inch at this length a difference of .128 inch is
correct for a 2 morse taper half angle.Setting the rotary table on the mag
chuck and using a dti and the dro to check and set this measurement.
As the grinding head height can be set anywhere is is a simple matter
to align using centres in the spindle and the work.

Continued next post

My 4 axis rotary table 2 morse taper i have never been happy with ever
since i made it a long time ago it runs true enough close to the nose
but was obviously off further in as the run out increased away from
the nose.As i have had the table apart for some modifications to adjust
the step count i have taken the opportunity to regrind the morse taper.

Seen here in the photo using the cylindrical grinder the rotary table is
mounted on the magnetic chuck and set over to the required angle.At the
back of the table there is a thread to push out the morse taper arbor
and this provided a fixing for a temporary pulley to drive .The grinding
work head provides the drive via a heat joined belt.
The first attempt was not too successful as the grinding spindle was
too long and thin so i made a new thicker spindle tapered like a
morse taper and set the grinding head at an angle so the spindle
entered with some clearance.

As with any grinding job the setting up can take quite a long time in
comparison to the actual grinding.
The end result shows zero runout at the nose and about 2 tenths
at the end of the test bar about 5 1/2 inches out ,happy with that.

Reading up on the current practice on grinding spindle arbors they
seem to be made these days from tungsten carbide ,they seem to
be listed as POA which i guess means they are not cheap.
It's a different world out there ,doubt it much it would fit anyway
with my home made kit.

Still have another one to do later in the week .

John

Posted by lfoggy 01/06/2020 14:30:08

I'm currently building the Quorn Mk3 and am working on the spindle assembly.
The threaded end caps to the spindle assembly incorporate an annular groove
as part of the labyrinth seals, machined into the face of the caps, that is 1.6mm
wide, 4.9mm deep. I've never machined anything quite like this before.
What's the best way to achieve this ? To machine it on the lathe would
require a special cutter with considerable clearance which I think would
be quite fragile.I am thinking of maybe milling it with a slot mill on the
rotary table....

Hi lfoggy

Unfortunately this is one of the chicken and egg type moments when building
a Quorn grinder ,if you had a Quorn grinder the tool to do these would be
easy to grind .The were a right pain to do when i made mine 35 + years ago,
the slot has to be concentric with the thread and also the inner bore and
inevitably requires a turnaround 2nd operation which has to be clocked in,
hole saws and the like are just asking for trouble as this part has to run true
for the complementary other part of the labyrinth on the front of the
spindle and also the pulley hub.

I have just recently completed 3 off grinding spindles similar to the
Quorn spindles. They do share some similarities with the Quorn spindles but
i have altered the construction thoughout so that each part can be turned as
a single operation and the part that you describe is now made in two parts that
eventually are loctited together to form one.The slot that you describe
is no longer trepanned but is formed by boring on one part and OD turning
on the other.This is a much easier method of construction but still requires
some careful machining.
The photo here of these three spindles in the lower right hand corner and top
left you can see the end caps reasonably clearly, the end cap and the
inner part that forms the labyrinth seal.It may not appeal to some doing
this but these spindles run very well to above 30,000 rpm.

John

Posted by John Hinkley 31/05/2020 08:03:57

Thanks for that. It's pretty much confirmed the direction I'm going on this one. Tried the knife
edge wheels described in my post with the CAD screenshot. That didn't work
either, I'm going to try a pair of 6mmØ silver steel rods fixed to the top of the fixture
and add three levelling screws for good measure. Failing that, I'm resigned to
ordering some new material for the "scrap bin",

Hi John

I think for the roller type of balancing cradles to work effectively the rollers need to be
large ,if you look in the lathe's web site at the Jones and Shipman page the balancing
cradle shown has rollers nearly 6 inch in diameter ,it all starts to get a bit big for hobby use.

Some useful articles have appeared in MEW long in the past .
An article Keith Johnson in MEW 180, Balancing grinding wheels , although written for balancing
wheels for the Quorn grinder the balancing cradle that he has designed would be useful
for balancing wheels.Uses round bars for the cradle.

Also worth reading
An article written by Michel Christiaens in MEW 139 Grinding wheel selection ,safety and
dressing.

Very little ever seems to appear in Mew in connection with grinding in general and
grinding machines,i think it is a much neglected aspect of this hobby.

Having said that Alan Jackson's small surface grinding machine made from a Dore Westbury milling machine has made a refreshing change.

John

Hi Pete

Looks like this machine has been quite well looked after ,so many of
these sort of machines have been badly abused ,the last place i worked
had a Myford MG 12 that had been poorly looked after at some time in its life.
The main problem was the head and tail stock had been dragged along the
table before it had been cleaned damaging the surface ,hope yours is not like this,
the result is the machine needed paralleling up every time either was moved.

Hope you will post some more photo's as the machine gets up and running.

Some useful videos to watch
Jeffery Badger The grinding Doc
and
Suburban tools grinding videos

John

Here is what i made to do the same job ,this balancing frame made from
pieces of old steel channel bolted together some slots milled in each side
for some hardened pieces of gauge plate.Fitted on the machine and
ground flat some pieces of aluminium at each end to stop the wheel rolling
off ,three jacking screws to level the frame .The edges should be ground to
knife edge but the balancing shaft is soft so i left them square.
Simple and little to go wrong just have to keep the edges clean.

John

Interesting video here on a restored Myford MG 12 also has the
video listings of the restoration process .
Not an MG 9 but interesting all the same.

https://www.youtube.com/watch?v=IdQlRLEQd0g

John

Hi Neil

From an article that i wrote in MEW 164 there are some calculations for 1/5 xl 3/8L and 5 mm htd i can't find the article among my notes .For 1/5 xl it is .200 x number of teeth divide by Pi - .020 inch = OD,

100 tooth pulley = .200 x 100 = 20 inches divide by Pi =6.366 inch - .020 inch = 6.346 inch ,in all

cases the pitch diameter is always is always greater than the OD.

John

I use 2 of these stepper motors which came from Arc euro they are
rated at 6.5 Nm .This Warco mill table size is 30 by 8 inches (760 x 205 mm)
so a similar size to yours ,there is a slight reduction in the output of these
motors as the machine uses a unipolar system but it still moves the table as
fast as the Align power drive .
Here is a copy of the specification sheet as a guide.
John