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Member postings for Mike Donnerstag

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

Thread: Angle Plates and Fixings
03/10/2020 14:10:54

I have two angle plates - a little Myford one (3" x 2" x 1.5" and a much bigger one (6" x 5" x 4.5". Both are cast iron and neither have webs. The casting thickness of the large on is 1". Both have one face slotted but the other face plain.

My question is: Is there any advantage to having a plain face on an angle plate, i.e. without any fixing holes or slots? Or... are these made with a plain face for drilling to suit the machine on which it will be used? The reason I am asking is that I am considering drilling the larger plate to suit my Sieg SX3 mill table.

Many thanks,

Thread: 5BA Threads
29/09/2020 09:38:21

Michael Gilligan: I haven't used Elcoda, though I do use Paulus Bowparts who are also in Germany. Although they don't make the BA thread bow screws (reduced to 3mm) as used by the Hills workshop, they do the '3mm Inch Thread' bow screws, which are a reduced 5-40 UNC thread, as in the photo below:

inch thread screws (paulus).jpg

I have made these screws myself using a 5-40 die, closed down to give a nominal diameter of 3mm. However, like the 5BA bow screws, it seems I will need to make a custom tap in order to tap the thread on the brass eyelets.

I assume I will need to use silver steel, hardened and tempered. However, it's a very small tap and I'm wondering whether there is a way of holding it in a mill vice in order to mill the 'teeth'. Prior to milling I will need to turn a taper, as it will be a taper tap for through threads. I've never done any of this before, and would appreciate any advice anyone can give. I have ER40 collet blocks and a full set of collets which, although large, may help?? Even better may be holding the straight shaft of my ER20 collet chuck in the ER40 collet block, which may give more clearance for the milling bit. Does anyone have a process for making their own accurate taps at this scale?

Many thanks,

27/09/2020 23:21:07

Having done considerable investigation and experimentation, I found that many threads used for instrument bow screws were in fact modified by over-tightening the die to reduce the major diameter from 3.2mm to 3mm. This was true of the 5BA screws and the 5-40 UNC ‘Inch thread’ screws and means that the standard tap is too large.

Can anyone give any tips on making custom 3mm diameter taps?

Do any bowmakers on here know whether these ‘special’ taps are available anywhere?

Many thanks,


24/09/2020 20:03:32

That answers my question - many thanks chaps!

24/09/2020 19:33:04

I'm sure this should be an easy question to answer. I understand that the nominal diameter of a 5BA thread is 0.126" (3.2mm). Is the actual external thread diameter (e.g. of the average 5BA bolt) less than this and, if it is, why is this?

Unfortunately I don't have any to measure, though I do have a 5BA tap and split die, which of course are impossible, or at least not easy, to measure. I suppose I could tap a 5BA hole and adjust the split die to cut an external thread to fit it, and then measure the resulting external thread??

If there are any instrument bowmakers reading this, I have been told that the Hill workshops used a modified 5BA thread for their violin, viola (and possibly cello) bow screws. However, my limited experiments point to it being a straight (unmodified) 5BA.

Any information very much appreciated,


Edited By Mike Donnerstag on 24/09/2020 19:34:01

Edited By Mike Donnerstag on 24/09/2020 19:34:23

Thread: Sievert blowtorch - regulators and hose failure devices
19/09/2020 21:02:47


I have tried the Sievert kit with a small (3.9kg) propane bottle and can confirm that it works perfectly with the hose failure device as the only 'regulator'. In fact, I found that the jewellery supplier Cooksongold supply a 'beginner's torch kit' which, like my kit, is only regulated by the hose failure device. My thinking is that, if it's stable enough to do silverwork, it should be good enough for my purposes. My burner (a 28mm burner giving 7.7kW) is far more powerful than the jewellery burner (a 17mm burner giving 0.25kW), and I only intend to use the torch for applications where my MAPP gas torch isn't man enough.

Once again, many thanks to all who replied.


19/09/2020 15:07:36

Many thanks again to all who posted, particularly Bill Phinn and Robert Atkinson 2. You both confirmed what I suspected.

Doing a little more research, it seems that many of Sievert's torch kits come with no 'regulator' as such, but just the hose failure device, including all the roofing kits such as those stocked by Screwfix, as well as the needle-flame jeweller's torch kits (so it must be reasonably good at keeping a steady flame!).

I found the following link which gives instructions on torch kits and even lists the 305401 hose failure device in the Regulator column

Being second hand and fairly dirty, I intend to give the torch and hose a wash with some detergent before cautiously trying it (probably outside until I'm completely confident with the controls!).

Once again, many thanks to everyone. Now... does anyone happen to know where I can find my glasses are that are usually on the coffee table in my lounge?


Edited By Mike Donnerstag on 19/09/2020 15:08:21

Edited By Mike Donnerstag on 19/09/2020 15:08:35

Edited By Mike Donnerstag on 19/09/2020 15:08:58

Edited By Mike Donnerstag on 19/09/2020 15:14:48

19/09/2020 10:26:24

I managed to pick up a Sievert blowtorch kit from eBay, though instead of a regulator it has the Sievert 305401 hose failure device. This has the POL (left hand thread) connector to connect it directly to a propane bottle.

My question is, do I need/would I benefit from a separate regulator? I notice that many torches only have the hose failure device, so does this mean that the pressure is controlled by the torch valve?

Many thanks in advance,


Thread: Hello
16/08/2020 10:57:44

Welcome Paul,

I haven't been here that long either. I'm not an engineer, nor do I make models, but I restore (and will shortly make) instrument bows (violin, viola, cello and bass). I also have an unhealthily growing interest in engineering and a hunger for engineering knowledge, as well as a reverence and envy for the skills of those people who are long-time contributors to the forum.

I'm sure you'll find all kinds of useful things the engineering lathe can help you with, from making tools to making guitar string pegs.


Thread: Can anyone tell me what this might be?
24/07/2020 19:13:12

Think I might rupture something, or just produce a loud raspberry which may offend the neighbours.

I have a compressor, so I'll try with that instead.

24/07/2020 18:54:07

Jeff and Tim: That's really interesting about the early tyre patching machine.

Bazyle: I haven't dismantled it as yet. I've been busy changing the bed on my Super 7, though having cleaned all the bits and bobs I'm now waiting for a replacement wick, so curiosity may lead me to give it a go.

Speedy Builder 5: The chrome lever just clamps the split casting onto a 1" bar. I attempted to blow into it, but I couldn't get any air to enter.


24/07/2020 15:50:39

Can anyone tell me what the item below might be? It has a cast iron body which fastens to a 25mm bar. It also has a fitting for a flexible pipe (hydraulic or pneumatic?) with a spindle? on the other end. Unfortunately there are no maker's names, though I understand it came from a deceased model engineer near Newark.

Photos below:



And before anyone says it, I'm almost sure it isn't Buck Rogers' ray gun.


Edited By Mike Donnerstag on 24/07/2020 15:55:39

Thread: Engineers' Level adjustment - why 4 holes?
24/07/2020 08:50:58

Thanks chaps - I bought a second-hand Moore & Wright ELS recently without instructions and, of course, it needed adjustment. I rang Bowers Group (who I understand own M&W) who told me that it was not possible to adjust it and there was no repair service! Not very helpful at all!! A good case of management too far removed from the manufacturing - they knew nothing about the product at all. I found through trial and error that the inner screws were there for adjustment, though I didn't know that the outer screws needed tightening afterwards, so I've learnt something there.


Thread: Hard felt alternatives for wipers?
22/07/2020 10:02:19

I realise this thread is old, but for those interested, I found this on eBay. It's 100% wool and used for oil seals:



Edited By Mike Donnerstag on 22/07/2020 10:02:45

Thread: Fusion 360 Whitworth Threads
19/07/2020 23:22:27

I'm just learning Fusion 360 and noticed there were no British threads as standard. I found that custom threads could be added if you downloaded or created the relevant XML file. I added ME and BA threads in this way. However, I couldn't find any file for BSW and BSF threads. Does anyone have XML files for these?

Many thanks,


Thread: Myford Mk1 Super 7 restoration
17/07/2020 11:04:42

Many thanks Pete. Sorry to hear about your health - hope it improves soon, and I look forward to your updates.

Which do you think is easiest: removing the spindle or removing the countershaft? Also, this may be a silly question but... how do you know if your rear headstock bearings need replacing?


16/07/2020 19:18:33

This is a very interesting thread to me, as I'm just about to replace the bed on my Myford Super 7 and will shortly be removing the headstock and motorising assembly from the old bed. Do I need to remove the spindle and remove the drive belt to allow the headstock and motorising assembly to be separated?


Thread: Myford Apron Dovetail Damage
16/07/2020 19:10:18

Great advice - thanks to all who posted. I did order some JBWeld, though I will probably just leave it smoothed.

The whole saddle was quite black, perhaps leftover from some kind of rust remover? I tried to shine up the non-bearing surfaces in several ways, in the following order, moving from mild to more agressive, all of which lubricated with WD40 or white spirit:

1) a slipstone to remove any high spots, though this was very of course very slow in removing the 'black' surface

2) green scotchbrite, which didn't do much either

3) fine emery cloth, backed with a small square of wood, which did slowly remove the black surface, leaving the silver cast iron

I assume it doesn't really matter how I make the non-bearing surfaces more cosmetically appealing, though does anyone have a quicker way that they use for all flat cast iron surfaces? Citric acid perhaps?


15/07/2020 10:29:17

I recently purchased a Myford Super 7 power cross-feed apron, but unfortunately the dovetail was damaged in transit, with a small chip around 5mm long and 2mm wide removed from the top edge, as in the photo below.


My questions are:

1) Is the saddle still usable? Am I right to assume that it isn't usable as-is, as it would result in wear to the gib?

2) Can it be repaired? If so, should it be brazed, silver-soldered or welded? I seem to remember having read somewhere that weld on cast iron can create brittle areas and therefore braze is better. Am I right?

Many thanks,


Thread: Myford S7 Cutting Barrel Shaped Cylinders
05/07/2020 22:14:13

Great advice Martin - makes complete sense. Am I right to assume that these surfaces need to be ground rather than milled?

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