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Member postings for Andrew Johnston

Here is a list of all the postings Andrew Johnston has made in our forums. Click on a thread name to jump to the thread.

Thread: Cleaning my lathe
02/09/2021 11:20:18
Posted by petro1head on 02/09/2021 11:06:28

Spring clean, so it looks good as new

Never, but once or twice a year I do a more thorough clean, checking adjustments and oil levels. My lathe is ex-industrial so it's never going to return to showroom condition.


Thread: Using a ginding setup on a lathe
02/09/2021 11:15:14

It is possible to turn hardened silver steel with carbide inserts or, even better, with CBN inserts. See here for results:

Turning Hardened Silver Steel

I've not tried turning HSS, but it's certainly possible to mill HSS with ordinary carbide cutters.

If a material is really tough then I'll use my cylindrical grinder. smile


Thread: 5 Rotary Table/Tailstock/Chuck Kit Info/Questions
02/09/2021 11:05:06
Posted by Dr_GMJN on 01/09/2021 21:47:49:

......the first part I’d use it for is the small (c.30 mm) diameter aluminium output shaft blank for my son’s rc car (as per earlier thread) The Chuck would seem the obvious choice to hold it, but the height restriction could be an issue. What would be the best way of centering and holding a piece like that direct to the table? Make a temporary base plate and screw the bar vertically to that, then clamp the plate to the rotary table? Or something like that?

I'd concede that a chuck might be the simplest solution, but not necessarily the most accurate. My rotary table has a 1" parallel hole in the centre, which is way more useful than a Morse taper. So I'd make a 1" spigot with a flange for clamping to the table and a recess to locate the work. There would also be a hole for a screw into the part to be machined.


Thread: 9/32 hex steel bar
02/09/2021 10:58:12
Posted by malcolm conomy on 02/09/2021 10:48:05:

more like 3000

I was going to say make your own 9/32" hex by milling from round but not practical for 30m.

I'd use 7mm hex - hope you've got a decent repetition, capstan or CNC lathe.


Thread: Cleaning my lathe
02/09/2021 10:52:42

Old paint brush plus dustpan and brush and kitchen towels. In the drip tray i have a rectangle of steel sheet for moving swarf around the drip tray, and over the edge into a bucket. There's also an old hacksaw blade for moving swarf from awkward places.

I aim to remove swarf and excess oil - not the slightest bit interested in the lathe looking pristine.


Thread: 5 Rotary Table/Tailstock/Chuck Kit Info/Questions
01/09/2021 21:31:40

When I bought my (secondhand) rotary table I also bought a small import 3-jaw chuck. I've never fitted it and not missed it, so I never will fit it. I mount work direct on the table.


Thread: Is there such a thing as an 'external reamer'?
01/09/2021 09:37:33

A UK supplier, although still not cheap:

Hollow End Mill


Thread: Scribing with verniers
31/08/2021 16:45:12

Wow, scribing lines? That really is old school. smile

I very rarely mark out now; mainly for sheet metal that will be filed/drilled by hand, and for the odd reference point to aid setting up a casting. I use a secondhand mechanical vernier height gauge and surface plate and very rarely odd legs; never used my vernier calipers. But then again I rarely use my calipers as I prefer micrometers.


Thread: Mounting stuff to a Faceplate
30/08/2021 22:13:42
Posted by Nick Welburn on 30/08/2021 20:47:15:

Is it the done thing to drill and tap the face plate..............

Definitely not, large faceplates are not cheap! I use existing slots, but if needed I'll make a smaller plate, or block, to hold the part:

teper plug reaming.jpg


30/08/2021 20:39:28
Posted by Nick Welburn on 30/08/2021 20:01:28:

Do I just use t nuts and my wedge things with the little serrated triangles? This looks like a dangerous option for launching metal at speed.

Nothing wrong with normal clamps and blocks, or anything else for that matter, provided the setup is thought through in terms of what might move under cutting forces. You'll not be running fast, no more than low hundreds of rpm. Here are some examples:


water pump bypass spigot.jpg



Thread: Traction engine build
30/08/2021 19:55:32

Welcome to the forum. thumbs up

I assume you mean Live Steam Models aka LSM? I'll start by stating that whatever advice I offer it is inevitable that somebody will pop up to say they made a 6" scale engine on a mini lathe. teeth 2

A Boxford is on the small side for a 4" scale traction engine. There will be a substantial number of parts which simply cannot be machined on it. I have a 13"x40" lathe which will swing 18" in the gap. That is sufficient for all the turned parts on a 4" scale Burrell SCC. While it is possible mill on the lathe again there will be a substantial number of parts that are too big for a Boxford. For milling I have Bridgeport vertical mill which is sufficient for most parts. While gears can be cut on the Bridgeport I have a large, but cheap, horizontal mill which greatly eases the cutting of the 5DP and 6DP gears needed and also doubles as a cheap horizontal borer.

Before building my engines I bought the plans, worked out what the largest diameter and longest parts were, and chose a lathe accordingly. The mill is less critical but the bigger the better, as bigger has more rigidity and a greater metal removal rate. A look at my photo albums will illustrate the nature of the tasks that need to be done. As a caveat I like to make all parts myself rather than buy in when required. So far the only big jobs done professionally have been the boilers and vulcanised rubber tyres.


Thread: Coolant pump - how to slow flow rate?
29/08/2021 20:04:24

Interesting; most of my coolant pumps, 3-phase industrial and single phase home brew, simply have a tap on the output to regulate flow. Ironically the only pump that failed (motor winding short) was the 3-phase OEM pump on the Bridgeport, which didn't have an output tap.


29/08/2021 08:36:00

Put a clamp on the hose or fit a valve in the hose.


Edited By Andrew Johnston on 29/08/2021 08:36:38

27/08/2021 10:53:33

Set screw is the correct technical term. But unfortunately sloppy definitions mean that set screw can also be used to mean a grub screw. Machine screws imply a non-hexagon head.

It's almost as bad as describing a milling machine as universal just because it has horizontal/vertical capability.


Thread: Mill vise and rotary table
25/08/2021 11:43:23

Another consideration is that having a heavy item at one end of the table makes it much harder work to wind the handles, in all axes.


25/08/2021 09:49:01

I find having multiple items on the table never seems practical, something always seems to be in the way. So I generally fit just the item I need to use; my mill table is 48" long.


Thread: Getting accuracy with my newly added DRO.
23/08/2021 21:26:34

I'm not sure what the problem is? Edge finding and cutter diameter are separate issues. All my standard carbide cutters are on size, or a maximum of 0.01mm under, on the shanks. For general work I never worry about the cutter diameter not being as stated. if i use old HSS cutters, or a slot or edge distance needs to be accurate (say better than 1 thou) then I'll cut 'n' measure using depth micrometers or gauge blocks and adjust as needed.

In all the years of using a CNC mill I've never used cutter compensation. Parts fit together straight off the mill. Occasionally I'll tweak the CAM program to cut under, or over, by a small amount as required.


Thread: cutting spur gears on a mill
23/08/2021 21:02:17
Posted by JasonB on 23/08/2021 20:45:40:

....they are likely to make better hobs than a standard tap.....

Specifically spiral flute, as opposed to spiral point.


Thread: Is there such a thing as an 'external reamer'?
23/08/2021 10:12:00
Posted by John Reese on 23/08/2021 00:42:22:

For a dozen parts special tooling cannot be justified.

Oh dear, I've been making special tooling for onesies and twosies:

cutting tools.jpg



Thread: cutting spur gears on a mill
20/08/2021 08:48:17
Posted by Martin Connelly on 20/08/2021 08:36:56:
Anyone who has ever cut gears will know that there is great satisfaction in it............

final drive gears fitted.jpg

worms and worm gears.jpg

Cast Iron Gears

governor bevel gears me.jpg

skew gears.jpg

Must be careful not to get over-excited. teeth 2


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