Member postings for Robert Dodds

I've never seen one of these but is there any connection to the print industry?
I can imagine a print roller bearing nesting in the cup, a matching setup at the other end of the roller and you may then adjust print pressure by jacking up and the lateral movement will facilitate print synchronisation with other colour rolls on the same machine

Anybody else got a flight of fancy on it?

Bob D

Jamie,
Well spotted and yes , thats the right way to go.

your dilemma now is whether to go for 3/8 whit or M10 tapping in the shank of the arbor. That depends on whether metric or imperial threads dominate in your existing kit. you will need a screw or studding to secure the arbor to the RT

Good luck with it

Bob D

I fell out with varifocals because of the poor peripheral vision from them. When driving, objects coming into view from either side were initially blurred and took longer to register and react to than without them A bit scary!
Swapped them for 2 ordinary vision pairs but now I specially request mid range focus that allows me to get best focus on a pc screen.
I was also fortunate in having one short focus and one long focus eye until my late fifties which meant I managed without glasses for a long time.

Bob D

I notice that in MEW 218 there is an advert for Avon tap and die

avontapdie.co.uk
they dont list 62tpi but claim to make any tap or die and as new advertisers may be eager to please
probably worth a call

Bob D

Muzzer,

I'm curious about your reverse screwcutting. If, as you say, you haven't inverted the tool but cut outwards from the far side of the bore by my reckoning you cut a LH thread. I have used this technique on occasion to produce cap ends and the like but the provisos are

1 You need a full undercut at the blind end of the bore to accommodate the tool whilst the work is stationary
and
2 Beware of unwinding the chuck off its spindle as the cutting torque in reverse tends to undo screw on chucks, predominantly found on modelling lathes. Moderate cuts and a good slam as you screw on the chuck are generally sufficient to keep it intact.

Bob D

Martin,

Just producing three holes doesn't justify spending a lot of money but in another age I used to use "slow helix drills" to produce holes in the copper pipes for urinals. Burrs on the inside from break through were not encouraged (you get sprinkles down the trouser leg) and the slow helix reduces the tendency to grab the thin wall copper tube.
Not being sure if they were still produced I googled and then stumbled on this site from Tomsk University http://portal.tpu.ru:7777/SHARED/p/PRONINA/documents/files/f9.pdf
Its set out like a tutorial but theres lots of relevant info in it

Bob D

David,

You could try "socket shoulder screws" if you require to separate the parts and reassemble with accuracy They are a bit like a screw in dowel and you can get both M5x6dia or M6x8dia in various lengths. you will need to drill part way into the lower part and ream to size so that the larger shoulder diameter is a close fit and provides the register. The fit of the thread then becomes far less critical.

Bob D

Continuing the idicator theme I recall seeing an alternative, may be even a de-luxe, version in the bottom of my toolbox. The pic shows a Verdict Junior, which research suggests was patented in 1943 so its a bit later than the Unique (1928)

The mounting arrangement is a bit more sophisticated, clamping securely on a 1/4" bar and also incorporates a split nut that allows the indicator body to be swivelled round to any angle and as with later Verdict indicators the stylus has a stiff slip joint to alter the strike angle

regards 

Bob D

Edited By Robert Dodds on 13/04/2014 20:28:26

Ian,

Have you seen Precision Polymer Engineering, Aberdeen

They list a 40 shore as one of their materials available but I have no idea what form they offer it in,
They do have design services and consultancy so may be worth talking to.

Bob D

Neil,

Are all your failures associated with intermittent cuts? Check your overall tool clamping and stiffness as you could see at least twice the cutting load applied at the moment of restarting the intermittent cut and this may flex your whole mounting structure (toolholder , toolpost, topslide etc) If this flex leads to a digging in of the tool you could expect occasional chipping and tool failures.

Not withstanding this, the other suggestions are all relevant,

Bob D

Hi
I've not seen much mention in this thread of bending stresses in cast iron. That is the usual failure mode of the T slots of a cast iron machine table. If your T nut or bolt is either damaged or distorted from previous use so that the inner edge of the T section touches the upper face of the T slot first you are going to produce a bending stress in the cast iron. Likewise if the T nut or bolt is significantly narrower than the T slot section you will again induce bending more readily than when using a full section width. (clear at the bottom, of course).
The main way of avoiding excessive bending stress in table clamping situations is to try to clamp through metal as with vices that have slots to take the bolt or stud and T nut. The other way is to avoid the bridging clamp type of fixing. It is this configuration that sets the middle tightening screw it tension and without any support on the table T slot this produces a bending stress in the cast iron and is when cracking and damage is most likely to occur, especially if there are long spanners or gorillas about. Sometimes its the only practical way of clamping and you may need more clamps and/or lighter cuts but it is important to keep your nuts in good order (bolt heads too)

Bob D

Geoff and Lofty
After 3 years+ I had come to the conclusion that I was alone on the planet with this Nodding Donkey but they do say "Never give up hope"
My research back in 2011 found Alan Dake, author of the video and collector of model engines, whom I spoke to and it was clear that his model had subtle differences around the horse's head. My detail shows two clamp bars for fastening the wire links and the lower one fouls the horizontal guide bar, preventing full rotation of the mechanism.
Alan's version does not have or use that lower clamp. However he didn't have an in depth history as it was an acquired model rather than being home built.
At the end of the day the pump part is a bit of a compromise since in working practice the Nodding Donkey , also known as a Sucker Rod Pump did its work with the wires in tension, pulling oil UP the well tube whereas our model works on the down stroke, pushing the wires and only working as a model by virtue of the relative stiffness of the wires.
See http://web.mit.edu/2.972/www/reports/sucker_rod_pump/sucker_rod_pump.html for more detail of the working principles.
My other concern was regarding the slip motion at the top of the pump.

The pump's max stroke is 1 7/16" and there is 1 13/16" slip motion above that. I measure about 2 7/8" for the head stroke( if you disregard the offending clamp ). The upper pump body, which contains the slip mechanism is just 1 13/32" long so on each stroke the little cross pin pops out of the top of said body and has to find is way back in on the down stroke. No lead ins or chamfers are indicated and it is probably a bit much to expect a 3/32" pin to stay a press fit for very long. Some sort of retaining cap needs to be fitted on the piston slide to act as retainer and guide for the pin as it transits across the mouth of the upper pump body..
Knowing someone else is out there with one of these may spark me back into actively working on it and finalising a solution for the cross pin on the pump..

Regards

Bob D

Get your bed reground before you take it up there and please spare a thought for the old fellow whose going to get it down one day. One day you might be fit to drop!!!

Bob D

Norman,

What I was implying in my cack hand way was that the lathe is worth more sold as parts rather than as a complete machine as is seen so often with respect to bare bones machines offered through trade outlets leaving Lots of Lolly to be made from the accessories.
Perhaps if I'd known it was off an Adept I would have bid down a bit more but I was happy anyway!
So far as the Adept is concerned IMHO restoration might be an interesting challenge for an impecunious but well skilled engineer but will be forever limited in it's capacity to remove metal and handle anything of substantial size.
My personal starting point for hobby work was a 3 1/2" Zyto which I still have and treasure but it was soon supplanted by a 5" Atlas as a more appropriate workhorse. Needless to say it came at the right price and with as many extras that I could get thrown in. Holbrooks and Acme Gridleys figured in my commercial engineering.

Bob D

Hi
Although I was aware of the Adept previously I was sufficiently inspired by this thread to look at Lathes.co.uk entry for the Adept which leads me to say don't scrap it as John S suggests.
The old adage "The sum of the parts is greater than the whole must surely apply" as I gladly parted with a fair sum of money to acquire a small X-Y table courtesy of H.Wshop that I now recognise as being the saddle and cross-slide from an Adept.
I'm looking to use it to provide the traverse movement in my quest to make a 4 facet point grinder for mini drills. The dilemma is "Do I now search for the remainder of an Adept or stick with my Proxxon?"

Bob D

Chris123,

You mentioned previously scraping the ways. Where and how much ?.Have you made any checks of the possible lift of the rear of the saddle due to clearance between the rear shear and the saddle retaining strip(it's not a gib strip as such)
Under cutting load if this clearance varies as you move along you can get the tool to push away from the workpiece by a variable amount and give a tapering effect.
one way to check with a dti is to use a suitable crow bar, with wood to protect your shears, to lift up the saddle against its weight and check for unusual clearances.

Bob D

Geoff,

I've not seen the Barker tool before but have used this bead breaker to good effect when punctures were a regular occurrence.

Edited By Robert Dodds on 03/02/2014 22:42:47

Graham,

Look on Associated Spring web site for constant force springs. There is a large range of sizes in stainless if you have to resort to making from new.

Bob D

Murrmac,

There are ready made M3 inserts that are within your size range and designed for both plastic or wood applications

**LINK**

They also offer M4 threaded inserts complete with a hex socket drive to help with insertion if you can accomodate the larger diameter

**LINK**

there is an online shop and you can get small quantities.
I have no connection with them but have used similar parts in the past to good effect.

Bob D

Does this guy in Australia qualify? He seems to have found a good use for old and unloved spanners!

http://wheelnroundworkshop.blogspot.co.uk/2013/10/the-spanner-man-john-piccoli.html

Bob D