Member postings for John P

Somehow doubt if BJ 11 would be interested in cutting a rack.
This one here took over 5 hours to cut the 159 teeth.

Was definitely a "OMG what a painfully slow process as you mill each one"
John

For those of you that are interested in saving the planet look
in at this video

https://youtu.be/uD4izuDMUQA

At somewhere around 3min 07 all life is nearly extinct if
you are still hanging in there at 6 .05 any surviving life that remains
find refuge around aging white dwarfs ,probably the descendants
of these half a dozen rich 'oiks' swanning around 'in space'
referred to by J Hancock a few posts back ,hope they have a good supply of
corned beef sandwiches and toilet rolls as Waitrose is shut for good, sitting
there desperately trying to read the re-run jottings of Geometer in the
umpteenth trillion issue of MEW by the dim light of an energy
efficient light bulb.
Getting back to planet E dimwit protesters blocking M25 no doubt
the offspring of these a*******s who thought it was a good idea
to put broken glass in baby food in the 70's or was it 80's
forcing suppliers to triple wrap items in plastic which is now floating
somewhere in the Pacific.

All this disruption has delayed my coal being delivered for my pot
belly stove in the workshop ,still i've saved all the junk mail the
postie has shoved through the letterbox all of the summer so i'll have
to use that to keep it warm for a few weeks .

Turn on the telly and there's that Attenborough chap who's made a fat living
jetting around the world with his crew for 50 odd years reporting on things
like the sex life of a dung beetle and now has a conscience trying to
conserve the planet.
Well i suppose global warming is here at least this Thunberg bird is
assured of a well rewarded career ,i expect when she has made
enough of a pile she will have her own private jet so she can travel
the world lecturing us all like that Kerry chap.

Is it my eyes or does the sun seem to to be a brighter yellow now than
some years ago.

Well did you make it to the end of the video ,i didn't there are plenty more
to see there on a similar theme ,watch enough of them and you will be
depressed enough and have to nip down to B&Q and buy a
length of rope.

Just as a postscript this tree hugging individual who portrays
himself as conservationist ,whilst we may have thought
this tree hugging was his attempt to connect with nature
judging by the pile of coal in his fireplace maybe he
was just sizing up the tree trunk to see if it would fit in
the grate.

Hi,
Use Timesaver yellow label abrasive for brass
https://www.heritagesteamsupplies.co.uk/lapping-compound-yellow-very-fine-3oz.html

Other grades available medium , fine and this one very fine.

John

Posted by brian jones 11 15/09/2021 22:27:24

Well PR post a pic of a hobbing attachment - not a specialised hobbing
machine - that doesnt count, its not for the hobby machinist.
My point here as I expect you noticed is that we all take for
granted that a lathe is generally designed to be able to make screw
threads. Its no big deal
But a mill isnt set up to make gears in a similar way
(nor a lathe for that matter)
In both cases you can go for a dividing head and laboriously
rake out each tooth
I dont know of a simple system that allows you to cut gears
with ease and speed (I am discounting the modern use
of stepper motors for the job for the purposes of this
discussion. No electronics allowable
You need to lock the spindle rotation with the gear
blank rotation by suitable gear chain and the whole should
run and chew out a gear - you may need some movement
of the cross slide if its a thick blank of course
Thats hobbing on gas
So is there a ready made attachment for mill hobbing?
Hence my pursuit of a cheap charlie way of knock
up spur gears - we already know the worm gear method
and this is an expansion of this method.

Have a look at Jeff Thyers gear hobbing unit made
for use on Maureen seen in MODEL ENGINEERS'
WORKSHOP magazine, issues 258 & 259
and at the video here.
https://www.youtube.com/watch?v=vuXyHe3VUpY

I cut many gears on my Doreen using the
methods seen in the book Gears and
gear cutting ,the gear cutting is all based
on using this machine with a little ingenuity
and the Jeff Thyers setup you may be able
to adapt the machine to hob gears on your
Doreen.

John

Posted by Mike Hurley 14/09/2021 09:50:53

Back in late 50's I remember my mother having a strange contraption
called a 'shopping bag'. This was reused thousands of times with no
waste whatsoever ( made from some kind of material / canvas or
similar), Now isn't that a clever idea?

If you want to save the planet i suppose recycling and re-using
is the way forward.

Posted by William Harvey 1 13 / 09 2021 20:43:15

What it doesn't show is how to achieve this and I am really struggling to some up with a
method of doing this.

If I make the template first, how on earth do I ensure the holes for the
valves are correctly located?

If I start by getting a sheet of template material and drilling two
holes with centres corresponding to the valve centres, which I
believe is 1.343"? How do I them transfer the template shape
onto this accurately, ensuring that the valve centre holes are
correctly located on the template.

Stumped.....

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

I faced a similar problem in locating matching holes in a blind plate,
although not the same as your situation the solution is much the same.
Seen here in the photo the two halves of a belt housing ,the main
part of the fabrication has some soldered in bosses to hold the cover
plate ,as these were in fairly random locations the cover had to be drilled
to line up with these threaded holes.Set up on the milling machine a
clearance drill is dropped into a hole to set the position and then the
cover plate which is oversize is held in place and just spotted ,the hole
is then drilled ,with the first hole in place the same procedure is followed
until all of the holes are drilled.The oversize plate is scribed around the
profile and bandsawn and filed to match the body of the housing.
The second part is much the same in the the centre hole has to line up
with the location hole in the rear of the body ,the housing is bolted down
and the centre of the location hole is located,the large washer and bolt
fitted to secure ,the cover plate fitted and the opening milled away.

It is useful to have a milling machine to do this sort of thing ,as you have
a pillar drill much the same can be done ,i would think that it would be easier
if you had a sheet metal template and by locating the valve guide with
suitable size rod in the chuck and then using a small drill to spot the
location with the template just held in position ,fixing then the template
with a suitable fixture in the first hole use the same procedure
to locate the second hole.

Posted by Michael Gilligan 13/09/2021 11:40:54

Whereas, this thread has run for four weeks … so far

Not a criticism, just an observation … I’m actually enjoying it.

MichaelG.

Michael
Quite an interesting observation since the third line in BJ's 11
opening post is

"OMG what a painfully slow process as you mill each one"

Four weeks in ,still no gears cut ,for the price of a couple
of gear cutters about £12 each or maybe in the time elapsed
could have made the Eureka device and made some of his own.
A couple of dozen gears could have been made by now by
a painfully slow process.

As time passes us all by the most valuable thing that you have
is time ,probably not the best thing to do is to waste it in some
futile quest.

John

Posted by Henry Brown 03/09/2021 11:51:13

"Has anyone worked out how to order these at the stated price on line as I
could do with a 3"? I've signed up and applied the special
discount code but it still states £93 odd!"

Hi Henry,
The September Advantage flyer has just dropped through
the letterbox and both of these vises are still on offer.
If you bring up the advantage page in the Special offers box and click on the code
for the vice on page 14
It will show for 3" list price £121.55 Web price £41.99 stock 83
and for 2" list price £98.69 Web price £31.99 stock 57

I usually place the order by phone on 0800 66 33 55
if you have no luck online give them a call at least you will
know what they are charging for this item. They are plus vat
and possibly a delivery charge about £4.00

John

Derek

That's probably the US site Google MSC J&L and you will find the MSC site.

I use my Quorn grinding head sometimes in the lathe ,flooded
with neat cutting oil keeps the grinding wheel clean no special
covering on the machine as the grindings fall away in the coolant
stream onto the normal swarf protection and are then just
washed away.

John

Hi Dave

The lining is there to insulate the firebox from the rest of the engine,
without the insulation layer in place the heat will transfer more quickly
to the upper parts of the engine,i expect that it is the same on your
engine in that the hot cap cylinder is isolated from the upper cylinder
with a heat resistant ceramic paper gasket similar to material
in the link that you have and sealed with some heat resistant
compound, i painted the hot cap cylinder end with black
heat resistant paint from Halfords (exhaust paint) .
I think that it would be a mistake not to have the insulation
layer in place ,substituting heat resistant paint in this application would be
completely useless.

John

Hi Dave

The engine that was made was also a Myers it was 3inch i think,
the firebox was lined with 4mm thick sheet similar to that below from RS
they still sell it its around £75 a sheet, they do sell the 2mm thick sheet
here for about £45 + vat Flame Retardant Calcium-Magnesium
Silicate Thermal Insulating Sheet, 2.8m x 610mm x 2mm , RS
Stock No 724-8906. Would probably be easier to fit in using 2 layers
with the fire cement that is how i fixed mine by laminating some layers
with the fire cement.
I could post a link here but it will be taken down almost instantly and
replaced with "online" which is of no use to anybody so i will send you
a PM with the link to the same material for a fraction of the price.
When i made mine i made some alteration the the firebox casting
by adding a support to form the lining at the roof of the firebox,
the two photo here show this ,it makes i easy to mold the shape
at the top ,the baffle is fitted low enough to allow the ring of bolts
that attach the hot cap end to fit and clear the space above is filled
with loose ceramic fiber blanket when assembled.

The engine was in model engineer from June 2013 4459 to
January 2014 4472.and is also seen here.

The photo gives no idea of scale it is about 24 inches to the top of the chimney.

John

Just follow the instructions on the drawing that you have shown , the lining
will hold fast ,the engine that i made for a friend the lining is still holding in
after nearly ten years ,looks very similar to the Rider Ericsson engine
that i made as you can see here.Some other photo's in album.
John

Hi

My Myford chuck is mounted in a similar way on a screwed
fitting on the rotary table ,to prevent it unscrewing during milling
operations you only need a long enough tee nut a piece of
studding and a hose clip or three fixed together as in the photo.
The tee nut will slide in and out to suit the diameter of the chuck,
the assembly is biased towards the undo direction as the
hose clip is tightened.You can mill in any direction you wish to.

John

I would have thought that the real concern here is the drainage
flow rate ,the pump you have seems to be 40 watt and 2 litres
a minute is barely sufficient as a coolant system ,most coolant
pumps are rated at about 20 litres a minute even if you don't
need it ,in any event the drainage from the tray should exceed
the maximum flow rate delivered by the pump otherwise you will
be needing a mop and bucket.

John

Hi Pete.

They are a good buy these vices at the offer price ,they come around on the
MSC flyer quite often ,the one i have exceeds the stated squareness and
parallelism by a good margin .
Worth keeping a look out on their offers on the Advantage and also
in their Clearance sale , i have bought grinding wheels for as little
as £3 each in the past.

John

Hi Pete.

I guess the flyer photo is the smaller of the two , the holes in the larger vice that i have
are just inside the hold down slots in either side ,the jaw movement and
mechanism works just the same as the Arc vices .

John

Hi,
For those of you who may be interested in buying this type
of vice have a look in J&L MSC Advantage Flyer August
page 13 at these Interstate vices on offer.

I bought the larger of the two some while back ,its very well
made.

John

Trying not to go of topic here. The OP 's aim is to be able to cut gears
using a tap by free hobbing , whilst this can be done as some have shown
on here quite successfully there is always the level of uncertainty as to the finished
result The photo here is a 90 tooth wormwheel cut using a 5/16" tap the finished
job works well using a piece of threaded rod, because this is done using a hobbing
unit you get 90 teeth every time even if the blank is over or under size.

90 tooth worm wheel

It is possible to cut a spur gear using a tap providing the tap is set over at the helix
angle and using the hobbing unit to time the motion .I think is less likely to be able to
do the same with a tap or even a proper hob in a free hobbing situation ,the situation
is worse with a tap and only 4 cutting edges as one cutting edge is disengaged
before the next is engaged so the blank has to revolve 1/4 tooth pitch on its own
with no driving mechanism,the most likely event is the cutting edge strikes the
tooth wiping it out or gouging some of it away.

Gear cutting hobs as seen here are mostly all threaded right hand at least all of
mine are ,the helix angle is indicated on the side of the hob,the largest here at
2.5 mod is 2 deg 20 min and the smallest 0.3 mod just over 1/2 deg .Usually
12 tooth the one on the left 0.9 mod made from silver steel flycut form relieved
in 3axis 8 tooth 3 deg helix ,again right hand could just as easily have been cut
left hand reverse the sense of one axis and incline the head 3 deg in the opposite
direction. To the right 0.5 mod 15 tooth Micron hob brand new bought of a junk
stall at ME show for 50 p ,what a bargain.

Gear hobs

In setting up the hob is inclined over at the angle indicated so the cutting action
is parallel to the table traverse ,from this spur gears and helical gears may be
generated in left and right hand using the same hob with no errors in pitch.
The spur gears will mesh and run with the helical gears with no problems at all.
The illustration here show the possible combinations and shaft angles.

Shaft angles.

Why is this the pitch of the hob dictates the pitch of the gear teeth and since
the set over angle remains the same nothing changes in making any of these gears.
The size of a helical gear will change for a given tooth count according to the
angle of the helix and is calculated by blank divide by cos , angle.

The sketch here shows the hobbing unit work head and the positions to cut
gears of the same hand and opposite hand ,this is really more to do with
accessibility than anything else as there are instances where it is difficult
to either fit the gear blank or get the cutter to a position to make the gear.
As the hobber is connected to the hob electronically there is no problem
in connection with the drive,the work head swings in an arc of about 250 deg.

Work head

There is however a variation in pitch if the hob is inclined at greater angle,
an explanation of this can be seen in Ivan Law's book Gears and
gear cutting on page 97 but has no real significance in cutting helical
or spur gears as this can only be used when cutting worm wheels.
At angles below about 3 deg this variation is ignored ,if the angle is greater
the worm is cut to match the worm wheel.

John

The hand of the tap or hob would have no influence on the
manufacture of left or right hand helical gears.
As here in the photo the hob is set over at the helix angle
and the work is set as here for right hand ,

and here for left hand.

John

Couple of videos for herringbone fans.

Don't blink for the second one.

https://www.youtube.com/watch?v=DFEN9_t150c
https://www.youtube.com/watch?v=9h7nn1v6D-E

John