Member postings for Brian G

Axminster sell a vertical bandsaw with a VFD offering speeds between 42 and 1000 m/min. I would love one if I had the cash and the space even though they say it can only cut 10mm mild steel plate and it costs £1,500. Realistically that would pay for an awful lot of laser cutting, and Bob's suggestion applied to a smaller machine would probably suit me more as I already have a hacksaw for thicker bar.

Brian G

Edit: Whoops, bandsaw speeds are not RPM

Edited By Brian G on 11/04/2021 20:39:41

Hi Brian

I am fairly confident that whatever pitch leadscrew the lathe has in practice, the metric table at least is based on a 2mm leadscrew, which agrees with Julian's measurement of what was meant to be an 11 tpi thread.

I had already tried 12tpi in my spreadsheet and according to the plate in the photo the metric threads work (at least approximately, apart from 2.5mm, which looks like a typo) if the leadscrew is 2mm pitch, but none of them come close at 12 tpi:

Pitch, 2mm L/S,12tpi L/S

0.5 mm, 0.500 mm, 0.529 mm

0.75 mm, 0.741 mm, 0.784 mm

1 mm, 1.000 mm, 1.058 mm

1.25 mm, 1.244, mm 1.317 mm

1.5 mm, 1.493 mm, 1.580 mm

1.75 mm, 1.750 mm, 1.852 mm

2 mm, 2.000 mm, 2.117 mm (56/84 x 60/40 = 1:1, suggesting 2mm leadscrew)

2.5 mm, 2.121 mm, 2.245mm (2.545 mm with 2mm L/S if 50t & 60t gears swapped)

The imperial threads are a mess with either pitch leadscrew, it is as if only the gears for metric threads are supplied.

tpi, 2mm L/S, 12 tpi L/S

10 tpi, 9.4 tpi, 8.9 tpi

11 tpi, 9.8 tpi, 9.3 tpi (2.585mm with 2mm leadscrew)

14 tp,i 15.1 tpi, 14.3 tpi (Pretty close if using a 12 tpi leadscrew)

19 tpi, 13.6 tpi, 12.9 tpi

20 tpi, 19.8 tpi, 18.7 tpi (Close again but with a 2mm leadscrew)

22 tpi, 18.9 tpi, 17.8 tpi

28 tpi, 30.2 tpi, 28.6 tpi

38 tpi, 34.3 tpi, 32.4 tpi

40 tpi, 41.6 tpi, 39.3 tpi (Close with a 12 tpi leadscrew)

44 tpi, 38.1 tpi, 36.0 tpi

Either there is something very wrong with my calculations (I rather hope for the sake of anybody with one of these machines that is the case), or the designers copied parts of the table from another lathe, perhaps unwittingly or else confident that only a small percentage of customers will try screwcutting before it is too late to return the lathe.

For comparison, the least accurate imperial pitches claimed by my son's metric Chester lathe are 8, 16 and 32 tpi, which all have the same percentage error, coming out at 8.03, 16.05 and 32.1 tpi respectively, which I think is reasonable from a metric lathe, whilst all the metric pitches are correct.

Brian G

Edited when I discovered that my attempts at tabulation were a dismal failure 

Edited By Brian G on 11/04/2021 17:43:43

I took this screengrab of the change gear table on a CD 210V lathe currently on eBay. I do very little screwcutting, so hopefully I am wrong, but the table looks spot on for 0.5, 1.0 and 2.0mm threads with a 2mm leadscrew (which leads me to fear I may be right).

It doesn't do as well for the others. The worst metric thread is 2.5mm which I think comes out at 2.121mm (56/80 x 50/33 x2 mm). It would be closer (2.545mm) if B & D were swapped, so perhaps this is a simple typo?

Imperial screwcutting appears totally chaotic, with only 20tpi coming close. Like Brian Wood, I can't get the numbers to work with a 12tpi leadscrew either, so I don't think they took this part of the table from an imperial lathe.

PLEASE will somebody prove me wrong, I really don't want to believe I am right.

Brian G

My guess would be that no.2 is an Austere Ada, a WD 2-8-0 in 2.5" gauge, serialised by LBSC during WWII.

Brian G

My guess would be that the cable is stiff because it is a hot condition type, and perhaps that is why the non-standard connector is used (like the difference between a computer "kettle lead" and a real kettle lead.

Having said that, this non-reversible connector looks similar, but without a drawing or clearer photo (from the supplier, not Michael) it is hard to tell.

Type C52 connector

Brian G

Provided parts were fitted to each other, would there be any need to measure more accurately than the 64ths divisions of a rule? Until recently the only way I would have been able to set the lengths of those axles would have been with a surface gauge and a 4R rule

Just because we can buy instruments graduated to 0.001mm doesn't mean we have to (or that the measurement will be that accurate). I spent a large part of my career explaining to engineers that specifying unnecessarily tight tolerances wastes time and generates an excess of either scrap products or concession notes, adding to the cost without benefiting the customer.

Brian G

I built one a while back, drawings and instructions were in the MEL kit. I think the original article was in EIM but cannot be sure (press and instructions left at my son's house so I can't check).

Brian G

EDIT

I'm pretty sure the kit drawings were different to the article, perhaps something to do with the guides.

Edited By Brian G on 25/03/2021 19:04:29

Maybe it is my nasty suspicious mind, but is it possible that the dial indicator has metric internals and an imperial dial? Approximately 0.020" is suspiciously close to 0.4mm, and I wouldn't put it past some makers in certain countries to do this. After all, you would get the same error using the compound slide on an "imperial" mini-lathe.

Brian G

Just type "sound playback module" into your online marketplace of choice (I tried eBay) and you will see many different types. (or wait until the shops re-open and buy a recordable birthday card, although I guess this will sound a bit tinny).

Alternatively, can you hide a larger bell (or a coiled clock gong) elsewhere?

Brian G

Same here, one by my desk and one in the workshop.

Brian G

I cant remember where I read this "The main difference between cheap and expensive indicators is the sound the owner makes when they hit a concrete floor"

Brian G

I think I was once taught why this happens, but it was over 40 years back and I've forgotten most of it so all that follows may be nonsense...

The magnetic field generated by the rotor windings is distorted by various factors that I freely admit I don't understand, but the net result is that in a motor which will normally run in one direction the windings are either advanced or retarded (my guess would be advanced as the field will need time to build and collapse - an Electrical Engineer would be handy right now but I dropped out after the first year) to compensate and obtain maximum efficiency. When the motor runs backward this compensation is the wrong way around and the motor is much less efficient, so it would probably run hotter as well as slower.

I suppose it is analogous to running a two-stroke engine backwards, the porting would still be symmetrical but the spark would be retarded instead of advanced.

Brian G

3D printing doesn't have to be slow. I have never bothered photographing these (NEM coupling adaptors for my son's 00 gauge wagons) but here is the setup on the Chitubox slicer. 32 at a time on the Elegoo Mars build plate take less than two hours to print, wash and cure.

Without an injection moulding machine, how else could I have produced them? Perhaps mill some bar to size and then mill the dovetail. Cut into 32 slices, then cut a slot in each of them and solder on a cap to form the socket. All dimensionally accurate to 0.002" and completed in less than two hours - I wish I had that level of skill, but have to accept that I don't.

Brian G

From recent experience two, one to install the necessary software and one to realise that the bulb was linked to the wrong account. And even then, "Alexa, turn on the light" can have totally unpredictable results depending on which Echo hears you first.

I'm starting to think rewiring the house to the latest edition in order to have all the switches at wheelchair height would have been simpler.

Brian G

It looks to me like a standard response/brush off where the sender is meant to insert "lathe", "machine", "item", "tool", "kitten" or whatever" in place of ***** rather than typing the whole message but omitted to do so.

Brian G

Perhaps there will be thread about Warco and baked beans saying "why should Weetabix have all the fun" ?

Brian G (who in his defence definitely isn't subscribed to Twitter but has a son who evidently is)

Hi John

It might be worth drawing your valve gear at different positions of the crank and comparing the valve openings to the Dockstader simulations. Several of them use an oscillating lever similar to yours, but derive their action from the vertical movement of the crank which is automatically 90 degrees out of phase with the piston.

Brian G

Hi John

It might be worth drawing your valve gear at different positions of the crank and comparing the valve openings to the Dockstader simulations. Several of them use an oscillating lever similar to yours, but derive their action from the vertical movement of the crank which is automatically 90 degrees out of phase with the piston.

Brian G

To be fair, their website does say this, albeit tucked away under "Ordering/Delivery".

Brian G

(No connection to GS Model Supplies, but having, like the OP, been caught out before I always read the shipping and payment terms. (In my case it was an eBay.fr item which required a bank transfer costing more to raise than the price).

I HATE cryptic crosswords, but think I have got this one. Nonsense could mean scrambled, in which case this thread is about Acrow props.

Brian G