Member postings for Tendor

Here's an old book, available online.

"Harmonic Vibrations and Vibration Figures" by Joseph Goold. 1884.

https://archive.org/details/dli.ministry.13780/mode/2up

or... Internet Archive link

Edited By Tendor on 01/08/2023 06:58:08

Nice machine!

Just a heads up: In the video it is running in reverse. It should be slow stroke forward, rapid stroke return.

As well as the E.W. Sheppard article (1 Oct 1976, p974) there were two interesting follow up letters on the topic that are noteworthy. ME 7 Jan 1977, p49 and 18 Feb, 1977, p208.

I have gone a little way down the path of investigating this for the same purpose. My preliminary results were not very encouraging, but I report them here for the information of interested members.

I acquired an old HDD and extracted the three 90mm diameter aluminium disks. (Newer HDDs have glass platens and are only 65 mm diameter). From one of them I cut 5 small circles of 33 mm diameter - the largest possible (given the hole in the centre of the 90 mm disk).

Using an optical flat they were tested for flatness by rigging up a very rough 'monochromatic' light source (a compact fluorescent bulb with green cellophane over it - about 550 nm wavelength).

Attached are the fringe images of two of the ten surfaces available (both sides of the disk are recording medium). Only one was 'nearly flat' (parallel straight fringes). The other image is one of the "less flat" examples. Fringes are half a wavelength apart - about 275 nm in this case. One fringe deviation from straight is therefore about 275 nm. Hume's book on autocollimators mentions that reflectors should be flat "within a few millionth of an inch" (~ 75 nm)

My conclusion is that these are not really good enough for autocollimator reflector use. However, beware that this was a single test on only one platen. Others may be better.

Found this at an Australian forum post from 3 years ago. metalworkforums.com/f223/t200445-hand-shaper

A "T.N.C. hand shaper" is described for sale. It has a logo that matches yours. Lathes.co.uk has this in relation to the Adept No.1: "Also made in (or exported to) Australia and marked (like the Adept lathes) as a TNC". Some photos of the shaper itself shown at the metalworkforums link above.

"... but 50*50*2 is roughly twice as flexible as 40*40*3"

Is this observation relating to flexibility in bending? Or some other loading type (e.g. torsion)? Or localised loading on the thinner 2mm plate?

I ask since resistance to bending is a function of the flexural rigidity EI. For the same material, the comparison is formed by the ratio of the second moments of area of the section - (bo^4 - bi^4)/12 for a square tube. For the ratio of SHS second moments of area for the dimensions quoted, this becomes (50^4 - 46^4)/(40^4 - 34^4) = 1.45. It appears that the 50x50x2 will be 45% stiffer in bending than the 40x40x3 section.

Confirm 4:1 for first, and think it's 4:3 for second.

An alternative thought to imbalance.

It appears that the motor is single-phase and hard mounted. A single phase motor does not produce a smooth torque, but 'pulses' along at 100 pulses per second. The reaction torque on the stator is transmitted through the hard mount to the machine frame. This may be the principal cause of the vibration.

The pulsing torque will also cause the rotating parts to alternately accelerate and decelerate, particularly as there is very little mass here to act as a flywheel. This can lead to the quill spline 'rattling' when the drilling load is insufficient.

On my old rig I conjured up a resilient mount for the motor to largely overcome the vibration from the hard mounted motor. The spline rattle would need a flywheel or similar on the motor shaft. The best solution is a three phase motor, but perhaps with me, not easily arranged.

You could do the following tests: If it is as described above, the vibration will not alter with belt ratio (spindle speed) and you will hear/feel 100 Hz (two octaves below G(above middle C)). If motor imbalance, and it's a 4pole motor (1475 rpm), the vibration will be at 25Hz unloaded (i.e. once per rev).

Reference: Theory of Machines, L. Toft & A.T.J. Kersey, Pitman, London, 6th edition, 1949.

It seems that posting these extracts will be 'fair use', fitting the purposes of this discussion.
Here then are the letters referred to above [14/2/2017 03:35:10]. Rod.

The discussion above correctly concludes that the rolling diameter of the centre of the wire must be the gear's PCD (hence disk diameter is PCD less one wire diameter). This applies when the cutting tool is shaped as a matching rack tooth.

Just to complete the record here, the 'Base Circle' ME article of 14th Sept 1950 was followed by some correspondence that discussed the 'pitch circle disk' as opposed to (as two correspondents suggested) the 'base circle'.

12 Oct 1950, K.Horsfell (suggesting base circle)
2 Nov 1950, J. Pearman (suggesting base circle)
2 Nov 1950, 'Base Circle' (replying to Pearman and making (the correct) case for PCD)
23 Nov 1950, A.A. Sherwood (replying to Horsfell, also making case for PCD)

I have scanned copies of all of these letters if wanted, but probably should not post here due to copyright(?).

Rod.

Damian has provided some information re the Tom Senior over at the original link. (See first post in this thread by Michael Gilligan)

Thanks for that Damian. I appreciate the information.

I had come to the conclusion that the Tom Senior must have had the plug/peg that you describe. I think that I will modify the Hercus 270 in that fashion. The (frequently used) locking screw thread will however be working in cast iron and so I guess that a coarse thread would be better for thread strength and wear, while a finer pitch thread would be better for the locking force.

Re the sketch that I posted. The holes for the clamping bolts are not slotted but just oversized to allow the gib to be adjusted. It appears that the draftsman left out the dotted line that should be there to represent the RHS of the hole.

Thanks again. If you ever have the Tom Senior disassembled again, a photo of the plug/peg through the gib would be of interest for the record.

Rod.

This diagram of the kinematics of a commercial universal hobbing machine (DEMAK) might be of interest.

It might not be obvious, but to cater for hob lead and helical gears, the hob axis can be tilted about the axis of gear pair H-I.

Many thanks Michael for taking the time to photograph and post the various locks. I really appreciate it!

On Damian's Tom Senior, I think that the lock screw must act on a cylindrical plug (far end slanted to match the dovetail angle) that fits a hole bored through the 'solid' gib. That might also be a good way to do it.

Thanks again,

Rod.

Very much appreciated thanks Michael. I agree that it appears some modification/addition is likely needed.

Any examples of 'good' lock designs for these 'solid'-type gibs would be of interest and appreciated.

Rod.

Thanks Michael,

I did not want to make the first post too long, but I'll add a couple of extra photos here...

No, the gib is plain. This photo shows the underside. Note especially that the three contact pads are co-planar. They appear to have been machined in a single pass under a shell-type cutter. It is original and not modified. I have confirmed this with other owners. I have considered that the centre pad should be lower than the outer pads, thus allowing the gib to bend under the action of the locking handle. But, there is no evidence of that and I also don't think the thick section would allow much bending action for a reasonable applied force/torque.

This photo is viewed from above with the gib removed.

I have had contact with another owner and also an owner of a Douglas shaper from which the Hercus is derived (Hercus took over the manufacture and made some mods). Both confirm the their locks don't work in the sense that very little, if any, extra friction is added when the locking handle is tightened. On mine, I can detect only a tiny change. So, if the two clamp bolts are pulled up, I cannot see how this lock can possibly function properly.

By the way, with the clamping bolts "nipped up", the adjusting screws act as very firm locks with very little torque. However, that cannot occur when the clamping bolts are tight (as I am supposing they should be).

Rod.

Thanks for the account Damian - a really inspiring job.

Your photo in post 24/09/2016 00:19:29 shows the vertical slide gib arrangement and raises a question that you and/or the forum members might be able to assist with. I hope it's not too dumb of a question.....

The Hercus 270 shaper that I'm overhauling has the same gib arrangement on its vertical table slide; that is a 'solid' trapezoidal-cross-section gib, adjusted with adjusting screws (with lock nuts) and then clamped with hex-head bolts at right angles.

My question is: How is the gib adjusted so that the locking action is able to function? From your photo, the Tom Senior lock is formed by another screw acting in the same direction and manner as the adjusting screws.

In the final stage of adjustment, are the clamping bolts tightened so that the opposite flat face (A) of the gib is pulled hard onto its mating surface and thus imposing the correct alignment to the gib? If so, how does the locking screw subsequently move (or bend, doubtful?) the gib so that the angles surfaces are pressed hard together?

Alternatively, are the clamping screws only 'nipped up' so that the locking screws is able to force the (slightly free) gib to slide in the locking direction? If this is so, then in the unlocked condition the gib would not be fully constrained and there is nothing to make the angled surfaces lie actually parallel. (The gib would likely rotate a little about the tips of the adjusting screws and only the leading edge of the dovetail would make contact).

Just to muddy the waters, the Hercus locking screw/handle differs from the Tom Senior. It is in the direction of the clamping bolts. I cannot see how it can possibly work as intended. What am I missing? (For the shaper, this slide is not intended to move under cut - it should be locked.) The Hercus has two adjusting screw/clamp bolt pairs. The locking nut acts on a through stud (shown protruding in photo) but could equally be a bolt.

Any thoughts appreciated. (Don't want to hijack this build thread - will move to a new thread if more appropriate.)

Thanks,
Rod.

Stamp says W.J.Steer - Maker

No one seems to have mentioned that the ebay unit has a mains lead running right up to the magnetic base which is therefore exposed to the machinist's environment of hot swarf, cutting tools and sharp-edged lumps of metal. The cable's sheathing is very 'minimal' whereas most machine tool mains leads have, or should have, substantial sheathing.

On the other hand, the Jansjo is powered by the SMPS located at the wall socket with the lamp supply lead at about (IIRC) 4V. Putting aside the possible failures within the SMPS, it seems to me that the Jansjo-style with 'remote' SMPS is the safer option for the machinist's environment.