Member postings for DrDave

What didn’t I do today? Turn anything! I pressed the “go” button on the remote for the lathe and nowt happened. Fortunately the supplier led me by the hand, via email, to reset the inverter. Some more troubleshooting pointed to the remote. Fortunately I have a spare, so swapped them over and all is well again.

At the risk of going back on topic…. Lasaero.com list both 2024-T3 and 7075-T6 in 0.040” thickness. 2024 is out of stock, but would not really suit: they only do Alclad, which has a thin coating of pure ally both sides, so it fails the scuffing requirement. They do have 4’ x 2’ sheets of 7075-T6 showing as in stock at £45, and they are based in the UK.

I dropped in on our local auction house yesterday. Out-bid on what I went for, but I came home with a lovely little oscillator steam engine instead. It would have cost more to buy the brass to make one, so quite chuffed (no pun intended) with it.

Hi Neil,

To be honest, I haven’t used my F1 for a while, so I am working from memory. I normally use 6 mm or 10 mm cutters, occasionally a 25 mm insert slot drill. I don’t feel the need for larger: just get your CAM software to program a suitable path (I use Fusion 360).

Feeds and DoC? In the higher strength aluminiums, I would think that full-width on a 6 mm HSS cutter, I would be conservative and have a depth of 0.5 - 1 mm. The machine has an ammeter for the motor current. I find that very useful to tell me how hard it is working. And when the cutter is getting blunt!

I have milled steel (up to En8, nothing fancy), but I forget the details. It seemed to take forever, so I might have been pussy-footing. 0.25 mm DoC, perhaps and trying not to use the full cutter width.

I hope that this helps

Dave

Pink Floyd’s “Welcome to the Machine”?

Oops. My “steel buildings” was a bad choice…. I did the analysis of a couple of lifting frames last year. Bolted together with clearance holes. By reference to Shigley’s book, we have assumed that the holes yield until all the bolts are active at ultimate load. But we digress.

Duncan, I see your point. Tightening the top nut gives a preload on the lock nut, which in turn transmits part of this to the bolt shank. This suggests that you should only use lock nuts where the preload is unimportant.

Why interesting, Michael? A modern steel building is held together by shear bolts, and the average aeroplane is peppered with them. I agree that applying shear through the threads is a no-no, but they bolt shank is fine.

Ah! That's got the hornets going again... To address the earlier point (which appears to have been removed) if you put the thin nut on first, it will strip when you dissemble the joint. If you consider what happens, this is clearly not the case.

I.e. install the (thin) lock nut first and tighten to, say, 25% torque. This gives roughly 25% preload. Add the main nut & torque fully. This unloads the thin nut (and actually reverses the load that it sees, providing the locking function) and gives full preload to the assembly.

If the main nut is removed, it goes back to a thin nut applying the 25% preload: it cannot retain the full preload because that was introduced by the (now removed) full nut.

We do seem to have moved into two spheres here: the "technically correct" thin nut on first, and the "historically or aesthetically correct" thin nut last!

One point that might have been missed, asI found from the ESDU Data Sheet that I referenced, is that this all applies to bolts that are predominantly loaded in shear. For those in tension, a lock nut is not required (have you seen many on a car engine?).

And lastly, as others have pointed out, lock nuts are not an acceptable locking mechanism for safety critical applications anyhow. So is the order really that important?

I've finally got the flywheel for my Corliss engine as one part, rather than a bag of bits. I seem to spend more time making tools to make tools to make things than actually getting bits made! Just need a couple of rattle cans from Halfords to finish it (after cleaning off the excess adhesive).

I have been following this thread (no pun intended) with interest because I was also in the thin nut on top frame of mind. Now that I am back at work after the Christmas break, I have been able to look up "lock nuts" in our technical libraries. The first reference that I found was in the ESDU (Engineering Sciences Data Unit) library, one of the go-to sources of data for Aerospace Stress Engineers. ESDU 14002 "Lock nuts and other thread locking devices" notes that "it is preferable to assemble the thinner nut first because the threads of the second nut are required to carry a greater load. However, this is not essential". In addition to this, the Data Sheet gives the theory behind this statement, showing the load transfer between the various parts of the bolt and the two nuts during the various stages of tightening.

OK, it still looks wrong to my eye, but the thin lock nut should go on first, as noted by the OP and the references that he has linked to.

Dave

A DH Rapide has been flying around south of Bedford most of the afternoon. I suspect that it has been visiting Old Warden, possibly to give pleasure flights.

There was an air show at Old Warden on Sunday afternoon. Possibly aircraft from there. There was (I think) a Spitfire holding north of the airfield mid-afternoon that you might have seen/heard.

The first scheduled flight that I took was on a Dakota. Every time I see one flying, it makes me feel old…

An interesting concept. Thanks for highlighting it.

And she’s just gone over us (south of Bedford) on her way home.

Dave

ITER is aiming for 150 million degrees. JET is probably similar (it is over 25 years since I worked there...). The point of ITER is to scale up the JET reactor to get closer to a power reactor, i.e. one that can run for months and produce significantly more power than it uses. I am not sure how making a smaller tokamak fits in with that progression.

Blimey, you have a good memory, Michael! I never did manage to find any info on my drill...

Dave

Spurred on by this thread, and an Amazon voucher from my employer for Christmas, I finally bit the bullet & invested in a Sovol SV01 printer. It only took a matter of days for Mrs Dave to go from "and what are you going to use that for?" to "magic has entered the house!".

After printing a few tool and collet holders from Thingiverse, I tried a dial gauge holder: not only is it too big for my dial gauge, but it didn't fit the QC tool post either... So, out with the CAD, measure up a standard Myford tool holder and a few hours later, this appeared:

The gauge is a nice push fit and it fits the tool post as-is. It just needs the screw for height adjustment (I printer an M5 thread to see how effective this would be.

Chuffed with the result!

Dave

My go to company for most milling cutters is Cutwell. And MSC can have tools at a respectable price in their monthy “Flyer”.

Dave

Byron,

If you removed bearing R2' and increased the shaft diameter between the remaining two bearings, that would give you a small increase in stiffness. The biggest increase in stiffness would come from adding a bearing in the left hand housing, on the opposite side of the turbine from the existing bearings: is there a reason that you cannot do that?

And keep up the good work. It is fascinating watching your development process.

Dave