Member postings for Martin Dowing

Be carefol with such items.

I forgot where it was but sometime ago hospital device with its cobalt-60 also found its way to a public scrap.

Martin

I have never regretted overengineering something but on few occasions I did regret *underengineering*.

I love to make things to last and to have them trouble free. As a hobbyst I care little about money while making a project. If I have found that money might be an issue it will be concluded that a project is not affordable and something else will be chosen.

It is rather rare that I sell something so I am not really concerned about cost of materials etc. However if I *do* sell something, I will often get few years later enquiries from my customer how the item is made because after years of use and abuse it seems indestructible in its duty or could I make more for profit.

I will kindly explain that repetitive work is not my cup of tea and refuse. Profits in engineering and other industries are to be made in China and Europe with its red tape, taxes, welfare etc is best to be left a a hobbyland.

Lets enjoy while party last and once we are dead deluge and egyptian plagues may come. Stupidity here gone too far to have any hope for a timely change.

Martin

I know a gimnastician, now in her 30-ties.

At the age of 21 she was considered a granny with no prospect to win anything and she was made retired.

From then onwards she never had a stable job. She hates rehabilitation and she hates to become PE teacher.

Martin

Set your spindle carefully in another lathe and make sure it turns true on external diameter close to chuck, in the middle and far away.

If you succeed then spindle is true. It is impossible to achieve it with a bent one.

Once done insert test bar into taper socket and check with DTI both ends of the test bar.

If the bar "wiggles" then your taper socket is surely misalligned. If it doesnt then you are not reasembling your spindle correctly.

Another approach is to install a chuck in your existing spindle mounted in the lathe.

Then grab test bar, eg 1 inch diameter linear bearing bar in the chuck and allign it true (make sure chuck grabs it straight). Make DTI readings on both ends of bar, close to chuck and close to far end.

If you get the same readings your spindle must be straight. Now insert test bar with tapered end into Morse socket of the spindle.

If wiggling increases with distance (towards end of test bar) *and* your initial test with test bar was OK then tapered socket is *definitely* misalligned and need correcting.

Martin

Maybe there is a small current leakage from motor to the earth through your lathe and this is detected on controller.

Some sort of residual current detector.

Martin

@David Taylor,

Did you use your wife's scarf to lift that lathe?

If so what it is made of?

Martin

Hi,

I have surrendered and purchased appropriate block of duraluminium 2017A. Suppliers here in Poland were complaining that they have been tricked into buying a bad lot of aluminium which was not conforming to norms.

Perhaps cheap, cheap cheap mentality backfired.

Many warehouses were flooded with this stuff but now situation is back to something what was in the past a norm, at least according to their assurances.

So the pulley will be made of aluminium at the end.

Irrespective of this subject I have one more question about Tufnol.

How tough are internal threads in Tufnol? Eg would they cooperate nicely with M5 male screw applied without overtightening?

Martin

@Ady

You will deform many parts beyond what is acceptable this way.

For those lacking electric furnace best idea is to use domestic oven or a hotplate. You may cover object on the hotplate with some thermal insulator.

Martin

ML 7 I can just lift up to my waist myself and put it where it need to be. It is just a bit over 100kg or so. Super 7 is a bit heavier but if you take off motor and tailstock it should be a piece of cake too.

You may ask someone to help as well. For 2 heathy men it is absolutely non issue.

Martin

It is rather diamond what is being destroyed by hot steel and not steel being affected by diamond. Diamond grinding discs used to be expensive (now thanks to Chinese this got changed), so reckless use leading to accelerated wear was discouraged.

At lower speeds problem is not as great.

Martin

Yes, I need to cut keyway, tommorow I will. Have a broaching set and it will come handy. Bought it few months ago.

Btw after hot pressing bush bore have contracted a bit. Had to reopen it a bit with a reamer.

It is important not to forget about a hole for a setscrew *before* pressing such a bush. Otherwise there will be unnecessary hassle.

Martin

Yes, it is a Top Secrect project, will run uranium centrifuge at 200 000 rpm.

Realistically it will be used for a grinding setup with 1hp motor at 1450 rpm.

Martin

Manufacturer of Loctite 636 suggests that at 250*C it is fluid enough to disconnect parts. Monomeric urethane acrylale which can be found in the bottle would polymerize at this temperature (that is what we want anyway), polymer should be barely stable but in liquidous phase.

Anyway thanks for radiant heat related explanation.

@Hopper, no this part does not belong to ML7/S7 lathe. Just a pulley.

Martin

Hi, Thanks for comments and advise.

Here is the part already made:

As you can see, it is nothing particularly sophisticated and I bet you already know, how it was fitted...

@Samarsanda, Duncan, John Olsen:

Once brass bush from my ML 7 pulley fitted in old Myford (Nottingham) gone loose I have decided to add Loctite as an additional insurance in power transmission systems whenever practical.

@Mark Rand, Chris Gunn & XD351

Actually it went in nicely at 250*C @ 2thou per inch of interference. All what was needed was a mallet and wooden block, which was not really critical but applied to bottom it down to shoulder.

@Neil

I agree. Loctite is just an extra security here and worth using.

@not done it yet & Duncan,

I ofen use liquid nitrogen for precision parts but this one seemed unsophisticated and liquid nitrogen would not be compatible with Loctite - it would freeze it. I will one day test liquid nitrogen with loctite to confirm this belief, eg I will find out, how fast is freezes.

Duncan, I am not sure about about slower heat transfer in low temperatures - when you look on thermal conductivity tables it seems to go drastically up in very low temperatures. There must be something more to it.

@Hopper,

My freezer goes to -20*C so I can win 50*C, eg 0.5 thou per inch. Every little helps, particularly if you have plenty of time to waste and patient wife.

Anyway, excitement is over and job is done. I hate spoil my work and I have seen professional guy stuffed half way with hot pressed bush. I have seen some obviously messed up job in corner if his shop, asked what have happened (what was already rude perhaps). After bitching for a while he explained that cold bush didnt drop in like it usually does and press didn't square... more bitching followed.

Martin

Edited By Martin Dowing on 28/03/2018 22:56:17

I need to hot press a bush into an awkward object which is too big for a working space of my bar press. Bush is cast iron, casing is a steel. Hole is 1.5".

Parts are made to medium interrupted fit. I may go to some place where they have a bigger press but I am tempted to stuff bigger part to the oven, smaller one to freezer and then bang them together with a mallet or with a hammer over a plank of wood.

Alternatively I could smile to my friend, get 2-3 liters of liquid nitrogen, cool down the smaller part and do the same. Unfortunately with the second method which I know would work I cannot use anaerobic retainer because it will solidyfy upon contact with cold part and I would like to use it.

So I am left either with hot "percussion" pressing or with going to engineering firm which have bigger press.

What would you do?

Martin

Bottoming of gears?

Thanks for comments.

@Robbo & Baz,

This is perhaps the best idea. Issues related to space were causing most concerns. It is important for stones of top grinder not to allign with your eyes, just in case...

Just try not to buy too many similar machines because even if now space is still there it is not difficult to stuff up workshop to the point that some other machines might no longer be feasible.

@Journeyman,

All suppliers of CBN electroplated wheels searched by me are shy of recommending them for carbide. I am sure they will cope, but maybe their life is going to be drastically reduced...

@Mike,

Diamonds are not recommended for HSS, unless used on low speeds, much below speed of my grinder. I have some cheap Chinese variete on lapping machine and it is doing its job very well

Due to increase of use of carbide tooling I have installed green carborundum wheel on my grinder. It works well with carbides, eg it sharpens them but it is rather crap for HSS. Of course I can also install normal corundum wheel on the other side of spindle but by doing so I will loose my roughing up wheel which is used and abused quite a lot and I cannot live without it.

Is there any way out of this conundrum, eg a grade of wheel which will deal with both carbide and HSS or buying second grinder is the only practical way forward (because replacing wheel on the spindle is invariably associated with trueing)?

Martin

All my MK2 tangs are slotted and threaded M8 to have both worlds.

Martin

If you think that they are dumb in business, go and compete with them. Try to sell them some European engeneering goods to begin with. Good luck.

Martin