Member postings for Simon Williams 3

Adrian - If you search for "Myford Super 7 screw cutting gears (metric)" using the "Keyword" field at the top of these postings, you'll find yourself being taken to (one of several) threads on this subject. It's actually about metric threading, but that's irrelevant as metric threads on a lathe with an 8 TPI lead screw are only imperial TPI's with funny numbers, the principles of working out the actual TPI being cut is the same. The main attraction of this thread is that the OP (Allan) put up some annotated photo's which explain which gear is meant by Brian's phrase "the mandrel wheel"

In case you didn't know, Brian has written the definitive book on the subject - his "Gearing of Lathes for Screwcutting". It should have been subtitled "All you need to know about making your lathe cut threads it's never heard of!"

Best rgds Simon

Well, according to Brian Wood (Gearing of lathes for Screwcutting) all you need to do is to fit a 29T gear to the mandrel gear, and set the American gearbox to 23TPI. This combination will cut 19.04 TPI, but don't disengage the half nuts once you've started. I'm assuming as you don't have a 19TPI setting you do have the alternative 23 TPI.

So the problem transfers from not having a 38 T in the gearbox to needing a 29T.

No doubt Brian will chip in with some other suggestions?

Rgds Simon

Gear train can (will) lock up if the reversible gear isn't pushed fully home on its spindle, because both the 57 and the 19 tooth gears are in mesh together. If the swinging latch will close you should be safe, but just check that you have only got one set of gear teeth in mesh, and that you are not trying to drive the final gear by two different routes with two different ratios.

Robbo - forgive me if it's a silly question - I thought the tumbler gears on an ML7 were the same as those on an S7, in which case they are 28 and 30T. Am I wrong?

Although (as Brian says, and he would know) the tooth count doesn't matter as they are idlers.

Rgds Simon

Aluminised mylar blanket as used against hypo-thermia by the emergency services?

Fibre glass mat sold as a plumber's heat insulating mat foe soldering in awkward spaces?

I've got one about 6 ins by 8 ins, comes with a sewn border to stop it unravelling. I bought from my local builders merchant

(edit - several people type faster 'n me!)

Edited By Simon Williams 3 on 06/07/2017 15:07:57

Well I've got several scrapers made from old files, the two I use the most are triangular but there's a flat one and a half round too.

I wonder if you've got the hardness so far up the scale that the edge is brittle, and chipping off rather than cutting. Try tempering the end to a light straw and sharpen it again.

Makes no sense to me to have to soften, sharpen then re-harden, the scale from the heating will dull the edge. Putting a nice sharp cutting edge on would normally be the last operation.

FWIW I only lick the edge with a fine grind stone, quick and easy, sharpen it in 5 seconds.

Good luck Simon

There is a comment earlier in this thread about whether there are any bits missing from the taper turning attachment.

I can't see the female part of the dovetail slide. This is carried on the adjustable slide which I believe mounts to the back of the lathe bed, carried on a big cast iron bracket. Or at least that's how the Myford one mounts.

This is what the Myford own brand version looks like. The nut and two dowels line up with the rearmost slot on the cross slide. Take out the cross slide screw, and the motion of the cross slide is now controlled by the dovetail slider.

You've got the long slotted piece, this bolts to the cross slide. But I don't see anything that marries to the dovetail piece unless the long slotted bit has got a dove tail machined in the underside?

Not familiar with this version of the taper turning attachment, but there does seem to be something missing?

xxxxx

Looking forward to seeing it. Can we have some " in progress" pictures too please?

Good luck Simon

And the name of the journalist who wrote the report? "Ouch Sony"!

Priceless. Absolutely priceless. What a wonderful world we live in!

Edited By Simon Williams 3 on 03/06/2017 20:09:12

For the sake of clarity, the bit that got overwritten in this post as adjusted above was that the table of threads came from the handbook for my MK 2 Bantam, so it shows how to set up the change wheels for 5TPI as requested.

There does seem to be a little bit of confusion going round - if the lathe can cut everything down to 3.5 TPI as shown in the manufacturer's table, then all those finer threads (of which 5TPI is one) are available. Cutting coarser threads - numbers below 3.5 TPI - might be difficult and certainly needs extra care or a different approach. But a Mk 2 Bantam is a pretty robust beast, and I wouldn't expect to have too much difficulty doing 5TPI on it. Mind you it's a lot of thread to whittle out, it's going to take a bit of patience (and a lot of concentration) to make a reasonable job of it.

I'm sure I'm not the only one who'd like to see a piccy of the finished result.

Thank you Neil, at least I don't have to lie down now to read it!

Rgds Simon

Try this for size, copied out of the manual for my Bantam Mk2.

I saw some comments a few days ago about rotating the pictures, so I loaded this to see if I could rotate it after loading it. Fail. Sorry Neil, you haven;'t fixed it - or more likely I'm too incompetent to follow the instructions!!

HTH Simon

Edited By Neil Wyatt on 02/06/2017 13:37:33

Edited By Neil Wyatt on 02/06/2017 13:39:19

Edited By JasonB on 02/06/2017 14:03:33

Edited By JasonB on 02/06/2017 14:03:53

.....whilst calculating the expansion of the universe on the back of an envelope!

I guess the school book picture of Benjamin Franklin holding his knuckle to a key hanging from a kite string being flown into a thunder cloud has left a lasting impression. On me. As the story goes, he got away with it, though I never understood how,

During my childhood several people were killed sheltering from a thunderstorm under a tree at the annual Cooper's Hill Cheese Rolling event. The tree was struck by lightning.

Hacksaw - don't forget the church key to tie to the end of the kite string.

Good luck!

I quote from the manual for my Bantam:

IMPORTANT

Take careful note of speed limitations when using faceplates: 18 in faceplates should not be run at more than 410 rev/min and 10 in faceplates at not more than 1220rev/min.

Derate/re-rate by the ratio of the squares of the speeds gets you a limit of 1900 RPM for 8 ins dia. My sphincter tells me that this is far too fast and I wouldn't go above 1000 rpm for 8 ins, and that's assuming the load is balanced. If not derate by at least a further 2:1. If the whole machine dances across the floor then derate further.

And don't stand in line with the chuck!

Rgds Simon

I guess it depends what effect the author is trying to achieve - if he is trying to stress the accuracy of his marking I could accept your "to mark accurately" or (under protest ) your split infinitive (eugh!!). By all means play with the poetry of the language to make an effect.

However, on the face of it I would rather he was "to mark a round bar accurately".

Rgds Simon

Edited By Simon Williams 3 on 28/05/2017 23:14:49

Well, than you all for your expertise, and for such exhaustive advice.

I have gone for the conservative conservation approach, gentle abrasive and cleaning with solvent. Here's the results so far:

I think (though I'm not sure) that the graduations are engraved not etched, and I don't think they are filled. Under a hand lens I can see that they are indented into the surface, but not by much and they seem to be a change in texture more than a contrasting colour. In any case I could foresee difficulties as suggested in possibly etching the surface finish - so I have gone at it gently with 1500 grit wet or dry used mostly dry but wet where it needed a bit more attack, and clean with brake cleaner. The W&D paper was a thin strip glued to a lolly stick, this gives a good compromise between being too flat and only touching the high spots or rounding the corners of every surface.

I cleaned the knurled surfaces with one of those horrid mini wire brushes in a Dremel.  Saying to myself as I did so "please don't let this catch and throw it across my workshop..."

For the time being I've just oiled the caliper again to reduce the chance of my sticky finger prints rotting the surface, but I'm keen on George's micro-crystalline wax idea. It's a lot more practical than trying to keep things wrapped up in VPI paper.

So I think I'm going to quit while I'm ahead, maybe coat the caliper with something but I've done as much abrading and scrubbing as I want to. They'll never be new, but at least they are readable. I just need to re-calibrate the zero's for the vernier scales - I took both off to clean underneath them and I haven't got then absolutely bang on the right position again yet.

Many thanks for the advice, as ever the expertise available is second to none.

Rgd Simon

Edited By Simon Williams 3 on 08/05/2017 12:02:24

Good morning all, could I please ask for some advice about de-rusting and preserving a set of gear calipers I bought recently.

As you can see, they are dirty but also they have minor rust marks.

Do I:

1. Leave well alone, just oil them and store them in VPI paper

2. Clean them in say IPA or brake cleaner, oil and store as above

3. Selectively scrub at the obvious rust and then oil etc.

If option 3, what is appropriate abrasive? I'm thinking 1000 grade wet or dry glued to one of those coffee stirrer sticks from Starbucks. Steel wool is another possibility, scotchbrite seems to me to be a bit too aggressive.

Your advice please?

Thanks as ever Simon

Couple of thoughts -

Don't go anywhere near it with silicon(e), it won't stick to hardly nuffink (it's a gap filler) and once you've contaminated it with those little Si molecules nothing but nothing will stick to it., It's a common fallacy that it will seal a pressure joint, but it won't.

Some pipe fittings are injection moulded with ABS. At this time of night I'm struggling to remember if it's PVC glue that won't stick ABS, or the other way round, but I know one glue sticks (solvent welds) both and the other only sticks the one. But this assumes the valve is moulded from such. If you could put up a picture of the valve it might tell us what we're trying to deal with. If the ABS/PVC choice looks like the right line of logic I'll do the research.

Finally, anything Loctite related wrecks PVC or ABS, don't understand the chemistry but it won't seal no way no how, not never.

HTH Simon

Seems like it's Easter Egg Holiday Micrometer Modifying Friday!

In between toasting hot cross buns, I too have been modding my micrometer.

Here's the sleeve dismantled:

The brown crud on the inner is dried oil. Carburettor cleaner is wonderful stuff...

And here it is after taking 8 thou off the LH end of the scale sleeve and re-assembling it.

I did it by holding the sleeve into a 12 mm collet and popping it into the T&C grinder so I could control the amount of metal removed. Is it fixed? - time will tell!

Now, why has the toaster caught fire.....