Member postings for Hopper

Engineers Edge is a wonderful online reference for all things design and more. Their o-ring summary for dynamic applications is here **LINK** and there are more specific pages if you search the site. Being American it's imperial but it does give percentages of compression and clearance so you could calculate it for a metric size. It is a good rundown on the how and why grooves are the sizes they are.

It certainly teaches you/enhances patience and perseverance, both handy skills outside the shed too.

+1 on that for small holes where the job is critical. Drilling for rapid but rough metal removal. Boring for concentricity and location and parallel. Ream for final size and finish.

Their method for pushing that drill through the steel with a simple length of timber and a chain is brilliant in its simplicity. Wish I had been smart enough to think of that when working on various construction sites over the years.

We should do like some charities do with collecting used spectacles to send to developing countries, only with model engineers' used safety boots.

A bit of anti-seize on there and it should be ok.

But will the SX1 rev slowly enough for such a large job -- needs about 50 rpm -- and have enough torque to power the cut?

Maybe you could fit a hand crank to the top of the spindle and do it that way, slowly slowly. Taking the hard skin off the outside of the rim on the bench grinder first would speed things up. Then a very sharp HSS toolbit for the final turning.

Edited By Hopper on 08/01/2023 02:09:02

Ah that makes much more sense now. Thank you.

A 3/16" HSS boring bar and a 2" hole should not be mentioned in the same sentence. As you have found, the one is not suitable for the t'other. So you do need a bigger boring bar, but going to 1" diameter is overkill on a mini lathe, unless you are going to bore 2" hole 12" deep or some some such madness on a mini lathe.

Those small 3/16 HSS shank boring bars, commonly refered to as micro-boring bars are more for small holes about 1/4 to 1/2" diameter and maybe 1/2" deep. They are very good for that. But they are designed for CNC work where the hole is drilled nearly to size first and the micro bar is used for a light finishing cut. Not for serious metal removal.

But for your larger holes, all you will need is one or two of those boring bars that Mick B1 posted above, with a steel shank with square hole in the end to hold some 3/16 or 1/8" HSS. They come in varying shank sizes so if you get a 5/16, 3/8 and 1/2" shank set, you will have most jobs covered.

Now, grinding the toolbits for a boring bar so they cut cleanly and chatter free is a bit of a dark art and perhaps not for the raw beginner without someone there to give hands on instruction, so you might consider buying a set of carbide insert boring bars like the one in the picture I posted way above boring the 2" in a red block of steel. I bought a cheap set of four with shanks ranging from about 7mm to 12mm . The tooling code for them is SCLCR 06 and then the shank size. The standard inserts are CCMT060204 but if you get the ground inserts CCGT060204 they have a sharper cutting edge and will work better in a small lathe like yours.

They work very well with minimal fuss. The shanks seem to be made of alloy steel and are claimed to be hardened and tempered, and are very rigid for their size. I think the 12mm one will have capabilities that far exceed those of your mini lathe so no need to go any bigger.

Someone made a suggestion in another thread of spraying ISO32 hydraulic oil using a discarded kitchen or laundry product spray bottle. Haven't tried it but it sounds like a quick easy way to spray down ways etc with a protective oil coating.

For three months I would not worry about belts. I worked for years on large air conditioning systems that sat unused for half the year or more and never saw a V belt that took a set in that time. Several years might be something to worry about but not several months.

It's getting the tack lifter into the zero gap between the head of the drive screw and the soft aluminium data plate without scarring it that defeats me.

I am mystified by this. Perhaps you can elaborate? You can see a piece of 3/16" HSS flex? How far is it sticking out of the boring bar?

And with your "DOC to 3D" are you refering to the HSS cutting tool diameter?

If you think you can take a boring cut of 6 x 5/16" or even 3 x 5/16" deep in a mini lathe, you are dreaming. That is 15/16". Not going to happen. If you can take a depth of cut of about .100" in a small lathe like that you can consider yourself to be doing quite well, boring or turning. Assuming you are talking about steel. But even aluminium you might get double that depth if you are lucky.

Some pics of your set up and details of what you are wanting to bore would be helpful. There are many other factors beside boring bar diameter that could be affecting your boring .

Material to be bored and the depth of the hole to be bored are important too. For instance, if you want to bore a 2"hole in a piece of steel plate 1" thick as in the pic I posted above, one way to skin that cat is to drill say a half inch to start with, then use an ordinary turning tool to face hole, starting at the small pilot hole in the middle and cutting outwards towards the outside diameter, taking cuts of say .100" inches at time, depending on your lathe's rigidity and power, both of which are not huge on a mini lathe of course. Then when your facing cuts are all the way through, a final boring cut or three with any small boring bar like the any of the ones pictured above will finish the job.

Ano

Thanks for the suggestions guys. Some very good ideas there. I had not though of dremelling a slot and trying to unscrew them, always assumed the long lead on the sprirals would not lend itself to that so will give it a try next time. I like Ifoggy's specialist pliers too. Must try to find some on the net. They look very handy indeed.

Would be very handy for removing date plates from 1970s motorbike frames before sandblasting or powdercoating, (although I am not a fan of powdercoating myself) without damaging the underlying plate. Some of the other cunning ploys with wood chisels and protective washers sound pretty useful too.

The taper letting go will not be a factor. I have successfully drilled 1" diameter holes in steel in my old Drummond Flagelator lathe with a No1 morse taper in the tailstock. Those tapers hold better than you might think, if clean and tapped home with a brass hammer etc. No idea though on how big the rest of your mini lathe can take.

How big are these holes you want to bore? It seems tothe like in a mini lathe you should not have to go any larger than the toolbits you are already using. For most work I use a boring bar with a shank about 3/8 or 7/16" diameter taking a little 1/8" square HSS tool bit in a square hole at the end. It will take a fairly decent cut.

It's all about how you sharpen the toolbit. They need a lot of extra clearance on the side next to the curvature of the hole being bored. And a good bit of top rake to provide a sharp cutting edge. Also don't put a big radius on the cutting tip, it increases chatter. I grind mine to a sharp corner than just round it off on the bench oil stone a tiny bit.

The other alternative, I bought a set of those cheap as chips insert boring bars that are everywhere on the net. Four boring bars ranging from about 6mm shank to 13mm shank and they work a treat. Very good for shifting metal quickly. But a well sharpened HSS will give a smoother finish on fine finishing cuts and better control over final sizing.

Pics show 1" drill in MT2 on the ML7, and 13mm shank insert boring bar doing a 2" or more hole in steel.

Yes. Petrol prices go up and down all the time. I have yet to ever see retail steel and aluminium prices go down. Or most other consumer goods for that matter.

i don't know of any tidy way to remove them without mashing up the plate below them. Very, very carefully grind the head off and remove the plate undamaged, but then you are left with nothing much to grip to try to pull out the remainder of the drive screw. And of course you can't drill them out, being hardened.

Trying to unscrew them with vice grips never seems to work. Can't get a good grip on the rounded head. So it's down to prying them out and that always mashes up the aluminum or brass plate and looks awful when you put it back.

There has to be a better way but I can't think of one. Anyone got any better ideas?

Yes according to free market theory, competition should force prices back down. But somehow in reality it rarely works out that way.

Interesting video, Jason. The definitive answer. How much higher than the headstock did you make the tailstock to get that pronounced result? Just curious as to the relationship between diameter and offset to achieve such a result.

Prices are unlikely to drop, even when energy costs and logistics issues are resolved. Once sellers establish a price that the market will bear, why would they drop it? Nice work if you can get it.

Which raises its own question:Why is it so? Why are power station cooling towers that circular hyperboloid shape?

Having worked in and on a few powerstations and always admired the graceful shape of the cooling towers, I always was told they were that shape because of a venturi effect that would draw more air up through the tower and increase cooling efficiency.

But more recently I have seen several things on the net saying the venturi effect is not a factor and that cooling towers are that shape because they are easier to build, without expensive formwork and specialised scaffolding because the single layer of thin concrete blocks is self-supporting as they go upwards in construction. Also it is a cost saving as the shape allows the use of thin blocks in a single layer, not massive thick concrete walls like the smoke stacks. (You could drive a small car around the top rim of a stack, it is that thick.)

Having never seen a cooling tower under construction (We always arrived to do the mechanicals after all the "sand and gravel" work was finished.) I have no idea if this is correct or not but it sounds plausible.

Edited By Hopper on 06/01/2023 03:24:07

Thanks Jason. I have caught up, finally!

Just checked Connolly's bible Machine Tool Reconditioning and he allows 0 to .001" high for vertical alignment of tailstock.

Edited By Hopper on 05/01/2023 11:20:49