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Member postings for Calum Galleitch

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

Thread: A mandrel for long narrow tubes
13/05/2022 22:50:33

I'd like to make a Delrin tube, of 2mm wall thickness, 12mm I.D., and around 210mm long.

I can drill out a thicker piece of Delrin rod fairly successfully with a pilot hole made with a single-point silver steel drill and following up with a standard, then long series 12mm drill.

To then turn the O.D. to final diameter, I want to mount the part on a mandrel both to stiffen the part while turning - it's wobbly stuff at this size) and to be able to finish the O.D. in one pass.

There doesn't seem to be much out there about mandrel designs for this specific application, so I have come up with a rough concept:


Four widgets slide on a shaft; the edges are chamfered to create a V-groove in which an O-ring sits. They are tightened by a nut on the end of the shaft which expands the O-ring and holds the workpiece.

So far, so theory! I'm finding it difficult to imagine the magnitude of forces at play here: would this thing actually grip against a cutting force? Obviously Delrin is soft stuff but I'd be taking a good bit off per pass, ideally.

Second, perhaps daft question: From my sketch, it seems to me an o-ring of 2mm thickness and 8mm internal diameter would be about right, but how would I go about being more exact about this? Presumably I can play around with the size of the chamfers and O-ring to achieve an optimum, but at this point I'm not necessarily sure what optimum even looks like!

Thread: Thread gears for Warco GH-1322 lathe.
04/05/2022 13:42:48
Posted by DC31k on 04/05/2022 13:14:55:

Why would you need a 127 gear to do metric threads on a metric machine?

I'd guess it was listed as such to act as a spacer.

Tristan, it's worth looking at your chart and thinking carefully about what's physically going on, because there's often different ways of doing something when it comes to the change gears. My lathe for example lists a specific setup for most metric pitches, one of the gears for which I don't have (my lathe also came from a school and arrived without the other changewheels...some kind of vortex, perhaps). However, close inspection reveals the "missing" gear is just an idler, so can be replaced with any gear that can be made to fit.

It's also worth figuring out what the calculation is to derive the thread pitch, as once you have that you can then work backwards and invent your own change wheel combinations.

Thread: Workshop warming
28/04/2022 22:07:39

A couple of months ago I realised that condensation would do for everything in my workshop if I didn't address it. I now have a very cheap fan heater attached to a little plug-in thermostat. It kicks in when the temperature drops to 6C and off again at 7C. It obviously consumes some power but watching the meter for the last couple of months I can't discern any impact, and we don't use electric for heat or hot water at all here.

Obviously 7C is not a lot but it made the workshop tolerable for me. I did have an old gas fire in there which gets the place toasty in short order, but it gives off so much water it's like a sauna after an hour or two. Since putting the fan heater in it hasn't been on once.

Thread: Stud bending on threading
26/04/2022 21:53:02


Here are two M8 threads I made recently (on the left; originals on the right). All I can say is that die thread imparts a considerable twisting moment - think of how hard you have to turn a die, and consider that force is being applied at a radius of a few millimetres. Fortunately in the case of these t-nuts I don't have to look at them, but I'd be interested to hear any tips on getting them straighter as well!

Thread: Hoover Motor wiring
23/04/2022 10:40:08
Posted by DC31k on 22/04/2022 21:02:45:

Again, on the killing himself part, repeat the exercise methodically and see how it is possible to produce a configuration where this is possible.

I think the point is that if you're not confident, then there is a fair chance that you will not in fact be methodical and end up holding two ends of a live wire. I did it myself some years ago replacing a bathroom downlight; having got the thing to bits I couldn't see something clearly so muscle memory took over and a hand reached around the door and flipped the bathroom lightswitch...zap! Fortunately I was only holding on with one hand so nothing more serious than a spicy thumb, but it was a useful lesson, one which could have been learnt an easier way.

Thread: Ping - and a screw is lost
19/04/2022 20:22:58

Perhaps a substance sold as "funky foam": a closed cell sponge sold in varying thickness of sheets in various sizes, many with a peel-off-and-stick backing.

Thread: Before calculators
19/04/2022 20:21:15
Posted by Nealeb on 19/04/2022 18:59:47:
Posted by JA on 19/04/2022 18:04:18:

All will give me the square root of 40 but none will give me the square root of -40!


Well, just imagine that!

Sounds complex to me.

Thread: ER16 Collets from Ebay
17/04/2022 12:40:42
Posted by SillyOldDuffer on 17/04/2022 11:29:08:
Posted by Calum Galleitch on 15/04/2022 23:37:26:

... They aren't great quality but for their purpose - workholding in the wood lathe - they are ideal. ...

Can you define exactly what you understand by 'great quality' please Calum? It's a hobby horse I know, but in engineering 'quality' is meaningless without a specification.

Well, I haven't measured them, but they came without any specification, and at least one of them has a slit where the slitting operator got about halfway through, was interrupted for some reason, and started again leaving a very obvious ledge of saw kerf. Once the ER collet for the big lathe is done I will try indicating a few with some circular ground stock and see how bad they really are!

Thread: work slipping while threading ...
17/04/2022 00:58:50

Assuming you are not peeling off tenths with your turning tools, you're applying as much force with a cutting tool as you are with a die, or thereabouts.

The two obvious things to me, besides checking the chuck is in good order, are (a) is it definitely mild steel and (b) is it definitely a 3/8" die and it hasn't been cranked up tight by the Incredible Hulk?

Thread: Redundancy, electrical
16/04/2022 23:08:51

It's a real pest, and one of the reasons I have over the years stuck with a hi-fi, vinyl and CD collection. I do have a small MP3 player but I consider it disposable. I bought one of the very first hard-drive music players, preceding the iPod, and it was wonderful, and longer lasting than the typical iPod, but the software to rip and download files to it have not been available for decades. I have a £20 digital radio in the workshop but in general I try to avoid clever consumer electronics. I also avoid laptops and use desktops with standard components for the same reason.

The fundamental problem is that hardware once sold brings in no cash, but programmers to update firmware and maintain websites and so on cost a fortune, so anything that relies primarily on up to date software is at risk. I think this is gradually becoming less of a problem - my phone is five years old and still in good order, and doesn't appear hopelessly clunky and out of date as a five year old smartphone once did. The raw power of modern electronics is starting to struggle to find a use for most of us.

None of this fixes your Echo Dot, though! The answer has to be regulatory, I think; you could complain to Amazon, and if you were very pushy/lucky [delete as appropriate] you might get a replacement or a refund, but honestly I think the person to complain to, daft as it sounds, is your MP. They are the ones who can actually create a repairable ecosystem of devices, or mandate that hardware be documented for open source programmers to use.

Thread: Myford ml7. Longbed for under 200
16/04/2022 22:45:42

You can just see what looks like a cross-slide on the floor in one of the shots, so there's a chance there's more there than pictured, but even so, a project is right!

Thread: An ER32 MT5 collet holder
16/04/2022 15:49:35

> This is the sort of thing I'd rather buy than make

The irony is I agree with you on the principle, but for various reasons I think this one is worth tackling myself as a learning exercise (and I very much appreciate all the comments and caveats, which are a huge help). One of the things I want to make later on is a tapered reamer for chanters, which will be about 400mm long, have a taper of about 2.5 degrees, and will then need to be ground to a D section

> firmly holding the part during each machining operation

My thought was initial facing, centre drilling and OD turning in the three jaw, then between centres to cut the Morse taper, possibly back in the three jaw to drill the drawbar hole and face to length, and the rest of the machining in situ. I do need to check I can get my toolpost up that close to the spindle nose.

> machine the whole from a long rod passing through the lathe

I did think of this, the main issue being my compound only has 80mm of travel - I know with a bit of care one can overcome this sort of problem but I think it's easier not to give myself problems to start with!

> you need to check the the spindle taper runs true

Thanks John, a very good point - I think I measured the parallel section of the bore as being very close to 38mm but I will check it again. I have an MT5 dead centre on the way so that will be a useful check as well.

16/04/2022 13:13:09

> If they are not ideal for milling cutters, what is their designed purpose?

My understanding is that ER collets are not suitable for high torque applications, including heavy milling. Not that I intend to be doing heavy milling in the lathe anyway!

> A purchased ER32 collet block held in a four jaw chuck

Yes, I have one of these and I considered it, but I don't want to mar the external surface, as I want to be able to use it accurately in a vice, and I definitely don't want to have to dial a tool in every time I move something (my 4-jaw chuck is excessively large, a story for another day!) I was also unsure how secure a hold such a setup would really have, though it's interesting to hear that others have done.

> How will you produce the perfectly flat-bottomed holes shown in your drawing?

I will assert they are flat, and none of you will be any the wiser :D No, the ends of the holes will be left as is, I don't think they're particularly crucial.

> there is no guarantee that the "turn down ER end OD" will remain concentric, so forming this at such an early stage is wasted work.

It creates a space for the taper to run into, meaning that as I turn the taper down I can easily measure when I have hit the big end dimension that I want, and then use that end as a reference to face the small end to length. No, not concentric, but adequate for the operations that I'll be doing with it, I think - I don't think a drawbar has to achieve perfect concentricity. I might turn that initial OD between centres anyway just for the practice of doing so.

> You will need very straight, parallel stock to run an indicator against

Quite. It was off topic but part of this exercise will be making a between centres test bar as I've never aligned the tailstock, although it is pretty good as is for the small stuff I have done so far.

> How will you check the fit of the taper?

I'm planning to use Harold Hall's "flange" method to dial in angles both for the morse taper and the collet taper - if his claims for the accuracy of the method are true then there shouldn't be much test fitting required. But taking the piece out and removing the dead centre for a test fit isn't that onerous.

> MT5 to MT3 sleeve and your existing holder

Yes, and it would probably be sensible to have a couple of such sleeves on hand. My existing holder is MT2 which feels like a big step for these sleeves. I want to make from scratch for a few reasons though - the experience of having done it (these are all skills I want to use on trickier projects), less fiddling around hunting for things (given my ability to lose things this is not unimportant...), plus (hopefully) the accuracy of the thing being made in situ.

> As a 'constructional' point, it doesn't need the 24mm hole up it - the more metal in the neck of the shank the better..

I take the point, but there's over 8mm between the bottom of the hole and the outside taper - an MT5 taper is a beefy thing! For milling I certainly don't need all that depth, but it might well come in handy at some point for other purposes.

> If you drill and tap the M10 all the way through you would make it easier to tap and you can then screw the studding in to act as a back stop.

That's a good idea - thinking about it a drawbar probably isn't ideal as a precision backstop as it will probably move when tightened a bit but there's plenty room there to run say an M6 thread down the middle. I'd probably make it adjustable from the spindle end though as my spindle is about 400mm long so getting an allen key down there might be tricky!

16/04/2022 01:17:52

I'm in the process of getting set up to do some basic milling in the lathe with a vertical slide, so one thing I need is something to hold on to those pesky cutters with. I already have an ER32 collet set, so while ER collets aren't necessarily the ideal for holding miling cutters, they seem an obvious choice. I did consider a collet chuck but I have a D1-5 spindle nose, and I don't fancy making six of those cam pins, or the price of a backplate.

I have about fifteen metres of M10 threaded rod lying around, as you do, so that will be pressed into service as a drawbar. Otherwise, the part essentially designs itself: an MT5 taper, with an M10 tapped hole, an ER32 nose and taper, and some flats to grip it with.


Plan, such as it is:

  • Face and centre drill
  • Turn down ER end OD
  • Cut taper between centres with set-over tailstock, test fit, etc.
  • Drill out and tap drawbar hole
  • Mounted in spindle, drill and bore
  • Set up compound for 8 degree angle and cut
  • Thread run-out groove and thread.
  • File some flats
  • ???
  • Profit!

I will also need to make a washer for the far end of the spindle bore.

Should anyone be interested, my OnShape model is here:

Thread: Newbie looking for advice
15/04/2022 23:56:42

Although the old adage is "you can make small things on a big lathe", there is a lot to be said for starting out on a smallish lathe. The 3.5" lathe was the standard hobbyist lathe for most of the twentieth century, and although 3.5" doesn't sound like much, swinging a 7" diameter part soon gets alarming, I promise! It can be quite surprising what can and has been done on such machines.

The thing about bigger lathes is that when you go from, say, 3" to 4", all the other numbers don't go up by 30%, they go up by 50-100%. Price, weight, power, danger...

There's a lot to be said for getting as big a lathe as you need, but speaking as someone who did exactly that, I will say that getting it fully equipped and doing what I want to do with it would (and will) have taken far less time if I'd curtailed my initial ambitions and gotten something smaller. On the other hand, the very small (7x14) lathes are really limited in what they can do out the box and it's questionable whether learning to deal with their inadequacies is time well spent.

The old metal v. Asian lathe debate will rumble on till the end of time and at the end of the day a well set up lathe is a good lathe, whatever its history. Old lathes now are, well, old, and perhaps sometimes fetch prices in excess of their value.

What I would suggest in your search is that you make some good notes, maybe start a spreadsheet, and think through all the different points that you and others raise, but at the end of the day, just get *something* and get started, and if in a year's time you need a replacement, you'll be that much better informed.

Thread: ER16 Collets from Ebay
15/04/2022 23:37:26

For what it's worth, I bought a set of ER32 collets plus MT2 holder off eBay in 2020 for £35 - it was a bit of an odd set, not a complete range of sizes with a few missing. They aren't great quality but for their purpose - workholding in the wood lathe - they are ideal. For the price I've no complaints.

Thread: Before calculators
15/04/2022 13:18:52

For the benefit of anyone as confused as I was!

screenshot from 2022-04-15 13-16-09.jpg

Thread: condensation
14/04/2022 13:45:48

I had damp problems in my little workshop (an old stone farm building) and I seem to have mitigated them pretty effectively with an electric fan heater attached to a plug-in thermostat. It is set to run when the temperature drops to 6 degrees and stop running when it rises to 7. The fan heater itself is adjusted as low as it can go and I think runs at a few hundred watts when it is on, which as far as I can tell isn't much, especially now the temperatures here have risen a bit. The workshop feels dry to the touch now, bits of paper left in it don't feel damp and greasy.

Thread: Acme internal threading
14/04/2022 13:13:40

There are inserts available for Acme threads, and if a suitable holder can be found at a reasonable price I think I'd be tempted to go this route. I've seen a few videos of people using Acme taps and in general, I like to see the machine doing the work, not me!

Thread: Making gears in the lathe
11/04/2022 23:47:08

Thank you all. Yes, I have Ivan Law's excellent little book, and I had forgotten it went into a fair amount of detail on setup; when I read it, I was more interested in the theory side as I knew nothing about it. I see from a quick scan that my notion of mounting it on the vertical slide facing backwards isn't completely ridiculous.

The change gears are definitely Mod 2.5 - the measurements are correct, the manual says they are, and the tooth profiles match the module 2.5 cutters I bought!

On making threads, no, I don't intend to produce vast numbers, but the ones I can do are fairly constrained and I do want to be able to do some very specific ones - for example, at some point I want to make an ER collet holder to fit in the MT5 spindle, as commercial items are £££-y, and I can't pick my own thread for that! But cutting just a 33 tooth gear would open up a lot of useful sizes.

John, thanks very much for that photograph - it makes me wonder if my cover plate is 100% correct - I've still to find time to sit down and work through the rest of the calculations, but it does seem a bit strange that it calls for a 20/40 pair there and nowhere else. Also the labelling of the ABCDE gears is different from my machine which I think matches the manual.

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