Member postings for john jennings 1

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Hi Graham,
As the material is aluminium I would try to make a broach from a long Allen key. Using a carbide tool I would turn a number of grooves spaced a little over 12mm apart They only need to take the points off the hexagon. I would then turn the first section to 7mm dia and the following sections to slightly larger diameters until the last section was the full hexagon. It should be possible to force this through a 7mm round hole as each step would only be removing a small amount of metal and only one groove would be cutting at a time. This is only an idea - I have never tried it.

Les.

Les Jones method can be made to work. Years ago I wanted to fit an operating lever on a large ball and socket head and wanted it immune to rotation. Luckily I had both brass hexagon (for the operating screw) and mild steel hexagon (for the broach). the hexagon was about half inch across flats and the hole about the same in length. As described I machined about ten grooves and steps and pushed the resulting "broach" through the pilot hole with a long suffering drill press.

John

I would have thought that a TAP WRENCH was overkill leading to tap breakage etc.

Suggest that the smallest pin chuck that is big enough is a better choice and gives a much better "aim" to ensure squareness.

john

Living in the countryside I am often rung by carriers seeking directions after SatNav has lost them. Often it occurs to me that the old advice " I wouldn't start from there if ..... " would be appropriate if not helpful.

To some extent this advice applies here. Murrmac has purchased some material to use in a manner previously found satisfactory in terms of time effort and result.

A further batch is different (deficient?) to the extent that a number of dangerous/expensive/toilsome procedures have been proposed and condemned.

I obviously don't know the costs/amount involved but is the best solution to source material nearer in specification to the originally used material rather than the " How do I get round being supplied with X which isn't quite right and needs fudging to work approach" which is often discussed in these columns?

John

Can only agree with comments on drilling machine/motor.

Firstly the drilling machine seemed to be vastly complex for its purpose.

The new motor was and is the novel aspect of the total device.

It seemed that such motors could be used for drilling/milling/grinding operations ( and were speed controllable as well as compact. As such they might form replacements for existing devices such as the Geo. Thomas Drill/Staking tool

Will we ever know?

John

An inspirational clip.

Far too short!

http://www.bbc.co.uk/news/magazine-24211691

I have used varifocals for some years now and apart from initial "wobblies and bendies" get on fine.

The small lens size that fashion dictates is not helpful especially if you have a stiff neck to cope with.

I found a useful middle way was a pair of "office varifocals" which are basically a normal vari focal with an additional "closeup lens" integrated. In practice this means the maximum sharp focus is a few feet (2 or 3) and looking straight ahead (as at a computer screen) is sharp, with closer focus as you look downwards. Distance like out of the window is blurred.

I did try a pair of bifocals engineered in the same way but they were not easy to use - the dividing line was always in the way!

John

I would think that a taper turning device wouldd be deployed for shallow tapers (Morse etc), a top slide at an angle for what is essentially bevelling - 45 deg 30 deg etc.

The topslide on the Compact 5 has only a short traverse, there comes a point where insuffient dovetail is in contact to give rigididty, hence only short tapers possible. The other problem is of course setting to the required angle. A simple cross slide used as a feed device for the cutting tool while the taper is put on by the taper set on the device is needed

Designing a full blown taper turning device for the Compact 5 has also got to cope with the inflexibilty of not having a disconnectable half nut on te lead screw.

John

"One of these days I'm going to treat myself to an LH caliper gauge".

I did. Absolute boon for measuring in chuck items near the headstock.

John

Is casehardening by what ever method the best or easiest way forward?

It appears that the mild steel block is worn and needs (?) remaking, if so a better solution would be to up-rate the material used to a hardenable steel which would then be hard all through and not just on the surface.

John

These are very similar to some lower tech items I made some years ago.

The start point was a number of spare chucks (5/16 capacity) for some brand or other of handrill (the sort with a geared handwheel disc driving pinions) bought after a local store had a flood. The chuck screws on to the main arbor and is closed as the arbor screws home and therefore has a 0 to max capacity.

After cleaning and derusting the initial addition was a T handle to use primarily as a tap wrench.

This was followed by a 1" square and 1" hexagon bars (3" long ) turned and screw cut one end to receive the chuck. The required thread was some odd diameter 19 t.p.i. but needed screwcutting anyway to ensure concentricity.

Not precision kit but a useful trio of extra hands.

It should be possible to remove the steel chemically leaving the copper untouched.

(the factors are similar to those discussed in the recent pickle thread)

Diluted acid: sulphuric or phosphoric or citric are possible choices (after cleaning of any cutting oil or grease) . Copper sulphate, somewhat acidified is best, will also remove the steel by replacing it wth copper - which will be powdery in nature and crumble away. Some hours/days of treatment may be needed periodic agitation with a nylon fine paint brush will also help.

Hydrchoric acid best avoided due to general rust promotion .

Ferric choride will dissolve the copper: I think the concept of the setting up of a anode/cathode cell in the mechanical circumstances that exist are small. For effective action a circuit needs completing possibly also with a small applied DC voltage. The tap I guess would need to protrude by 1 or 2 mm to make this possible.

I would stick by the above soak and wait strategies!

John

As a much retired chemist the following points may help.

1. The pickle used for "calcium deposits" may just have been neutralised so as to be ineffective. Try a fresh diluted solution.

2. The pickle is usually doing two things removing scale - essentially copper oxides - and removing/dissolving flux residues. The oxide should dissolve in any dilute acid, thus hydrochoric,sulphuric or citric will be ok. Sodium Bisulphate (aka Hydogen sulphate) is half neutralised sulphuric acid a should also work OK it is like citric acid a solid which may be more convenient.

3. Nitric acid will also dissolve the scale but even dilute nitric acid will slowly dissolve copper (sulphuric should not).

4. As an aside all acids will remove the zinc from brass leaving it copper coloured

5. Hydrochoric acid is a gas HCl dissolved in water it will tend to escape and attack bare steel and iron intiating serious and rapid rusting. Keep it out of enclosed workshops!

6. What do the elfins allow you to buy in 2012? Even citric acid, from health food shops, has moved under the counter but ask. Hydrochoric acid is sold as patio cleaner. Strongish Sulphuric acid is I guess still available as battery acid and will need carefully diluting acid to water. (pure concentrated 98% ,an oily dense liquid, is probably difficult to obtain and would need very careful diluting as adding the concentrated acid to water generates enough heat to boil the mixture if done too rapidly, AVOID)

Some years ago when replacing old steel hinges with posher solid brass ones it always annoyed me that most brass hinges seemed to be countersunk to fit ODD number screws. The normally available No.8, No 10 etc being either two big or two small for a properly "fitted" look . Was there any reason for this?

John

Tubal Cain in his book “Simple Workshop devices describes making a set of RoseBits or Hollow Mills derived in part from clockmaking devices for making . screw blanks Essentially they are four toothed end mills with a central hole the desired diameter. They cut on the end only and of course a one size only device. Providing they and the stock to be reduced are both held in accurate chucks alignment should not be a problem. The length of the reduced diameter is not unlimited.

The Jacot tool mentioned previously is more of a filing and burnishing rest than a fixed/travelling steady for turning.