Member postings for Dave S

The original bar bed Unimat made extensive use of zamak, so as a material for small lathe use Emco already had experience (and presumably a supply chain).

Atlas (I think) lathes in the USA used zamak changewheels, and various other machine parts in various other machines are made of it.

It’s relatively cheap, casts well and is roughly as strong as brass, whilst being slightly softer than iron/steel.

I believe it also has good vibration damping properties.

Dave

Pretty sure the saddle is not "aluminium". I think it's mazac or similar alloy.

The headstock and tailstock castings are also the same mazac type alloy.

Dave

Edited By Dave S on 17/06/2023 21:37:17

This is the problem, hence asking if anyone had direct experience of this.

An equivalent Eclipse (to name one well known brand) chuck is out of my affordability.

The pics on the chinese one look 'ok'. The lack of end fence ( thin end) is not an issue for me - I never use an end fence anyway.

The Chinese are easily capable of producing a good (or at least "sufficiently not shit" chuck, but they are also capable of (shall we say) somewhat overstating the quality, and its not simple to tell. Poor english is not a good guide - their english is way better than my chinese...

My current chuck is too small for some work I need to do on the grinder, but its also chinese in origin ( I imagine anyway - it came from Arc many moons ago).

Maybe I should just buy one and rely on the 30 day amazon money back in case its truely rubbish...

Dave

Looking for a new mag Chuck for my J&S 540.

Come across this on Amazon : **LINK**

Anyone got any experience of this type of fine pole Chinese mag Chuck?

Dave

Small bicycle brake disks tend to be stainless steel of one sort or another. The central flange of most car disk brakes is quite thin, and probably of sufficient size.

Dave

I replaced mine with brass rectangular bar of unknown alloy.
whilst 7075 is one of the harder alloys I would use mild steel or cast iron in preference.
sort of Brass > Iron based metal > aluminium based metal.

Whilst your there also do the cross slide gib.

Not sure where in the world you are, but DIY sheds (B&Q etc) often have eye wateringly expensive small bar stock.

You could probably hack a suitable piece of iron type metal from a small car brake disk

Dave

Because silicon fluid is not hygroscopic any water in the system remains as water, and ends up as small pockets of low boiling point fluid. It only takes a small pocket of steam to knacker the system to the point of no brakes. The reason for microscopic fluid is the more general degradation of boiling point in the whole system.

No need to use a DRO on external threads.

Engage half nuts as though cutting whatever thread it was.

advance the correctly ground cutter using the cross slide, and line it up with the topslide as it engages the thread.

I've done this many times to pickup an existing thread.

Even works with metric on an imperial lathe.

Cant say I've needed to do it on an internal thread - where the visibility of the tool is some what less.

Dave

The late JS of this parish used to move Bridgeports not infrequently.

An engine crane, a good enough capacity van are required, along with some spanner’s.

I suspect a search here or on the Uk rec models engineering list (googlewill search it ok) will find the details, but iirc it’s off with the ram, off with the table remove knee if required and then sling the bits into the van. Reassembly is the traditional Haynes reverse of taking apart…

Dave

Option 5: lower speed motor. 1400 is iirc a 4 pole motor. 6 pole and 8 pole are available.
8 pole would halve the input speed for no other changes.

Might be enough?

Cunningly arrange a solenoid or 2 inside the cylinder and put the batteries in the boiler?

Nearly always

For 2D DXF LibreCAD would fit.

Start with bar, bosh in m12 thread, thread onto m12 arbour, turn features.

use m12 to fixture in mill for odd angled holes

Dave

Just to update this. I used microkerf after getting a few quotes.
Ordered back end of last week and the parts turned up today.

very happy, they all fit as designed.

Dave

I’m making progress on my CNC build, and I now need to find someone to cut some 5 or 6 mm steel plates for various bits of the structure.

Any recommendations?

Dave

Iain,

you might do better brazing a small carbide tip to a piece of steel. I have an old circular saw blade I use for this sort of thing. It’s bstard tough steel to cut mind…

The tips can be sharpened using one of the now ubiquitous diamond plates.

Dave

I tend to hold the HSS toolbit in a pair of mole grips, grind away and then use. Saves both time and burnt fingers...

I have heard the micro crack theory, but not seen it happen. Dunking a piece of red hot silver steel to harden it doesn't tend to cause issues, so I don't see why a much cooler piece of tougher steel would fail.

I suspect that the micro crack 'myth' (going to call it a myth for now) propagates from the cemented carbide world - where certainly older carbides were prone to premature failure if the coolant supply was intermittent.

Dave

Why wont this myth die? HSS holds its hardness at red heat. Thats the whole point of HSS.

It is *very* unlikely you will be able to temper a piece of HSS using a bench grinder.

Dave

Blued Pivot Steel is a generic term used to cover what is typically a normal carbon steel that has been hardened and then tempered to a dark blue.

This is the 'normal' state that the various shafts with pivots are turned in. The hardened steel tends to take a much better finish than 'soft' and you don't have to worry about heat treat distortion.

This (grain of rice for scale) is turned from blued pivot steel:

probably 2.6mm 'raw' diameter looking at the collet markings. It cuts beautifully with a properly sharp graver.

It was then rivetted back into the balance -

So riveting of hardened and tempered steel at watch scales is a 'normal thing.

I also use a Unimat4 with a piece of angle iron as a graver rest sometimes. The biggest thing that makes a difference is proper magnification/lighting. I use variously a stereo microscope or an optivisor.

Occasionally Ill do tiny things on the CVA (10" lathe), but that's usually because I want to bore a very small hole, and the power feeds make a difference to not snapping the fragile tool...

Dave