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Member postings for Jed Martens

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

Thread: Has anyone watched this Girl
18/01/2020 21:31:30

As a novice I've found her videos for beginners to be very helpful. I enjoy the entertainment value of the popular youtube machinist channels (Abom, This Old Tony, et el), but Quinn's equipment and projects are much more appropriate for my level of experience.

Thread: DIY magnetic DRO
21/12/2019 15:46:46

And here it is fitted to the mill...


18/12/2019 22:36:30

I decided to go ahead with my first idea. But only for the Y axis for now, as it's the shortest and if things don't work out, it's easy to replace the tape.

I machined the read head enclosure out of aluminium. I started with a drawing but ended up free-styling a lot of it.


The bracket for the tape is pretty simple...


I ordered some armoured cables from Machine Dro. I removed the DB9 from one end and drilled a hole to accept the cable sleeve in the read head body (10mm). This is retained with a M3 grub screw. The cable quality is very good - all connections individually sleeved, and good screening. 20191218_100045.jpg

Next, I bodged together the electronics with parts I scavenged from the left-overs bin in the office. It ain't pretty...


But it works!


Ok, only the axis labelled "X" is live in the above GUI pic.I'm just moving the read head against the tape bracket by hand, but it increments in one direction, decrements in the other, and it changes by roughly what you would expect.

To be honest, it's all gone too well, so I'll stop now before something blows up. Next step is to fit it to the mill, and to consider how to tidy up all the electronics and mount it in some kind of enclosure.

Edited By Jed Martens on 18/12/2019 22:44:04

Edited By Jed Martens on 18/12/2019 22:51:02

Thread: Machining a curve
16/12/2019 15:58:15

Ok, done. Thanks for the prompt feedback.

16/12/2019 15:47:45

I'm trying to figure out how to make the part below. It's a "bell" that is used for crimping crown caps onto glass bottles. Most of it is simple turning and threading, but I'm not sure how to tackle the "bell mouth". My best guess so far so to successively approximate the curve using the compound, and then use some kind of abrasive to blend it together.

I don't think the exact nature of the curve is critical, just that it is smooth and gradual, and that the minimum internal diameter is spot on.

Is there a better way?


Thread: Slip gauges
15/12/2019 09:45:59

Thanks chaps, that's an impressive collection of advice in just 24 hours.

I appreciate the arguments for and against buying second hand, and I have no doubt that there are bargains to be had. But I don't have the experience to judge the quality of a second hand slip gauge, and given their role as a reference, I want to have confidence in them.

The gauge holders look interesting, and I can see how they would be useful. The holder itself appears simple to make, but am I correct in thinking that the jaws (placed either side of the gauge block stack) need to be of similar accuracy to the blocks?

Based upon the above advice, my feeling is that this 47 piece set will be more than adequate for my needs - cheaper than the ones I listed originally, and just the 5 micron block below 0.01mm accuracy.

47 piece set

Again, many thanks for all the input.


14/12/2019 08:49:03

I'm considering asking Santa for a set of slip gauges for Christmas. These will be for set-ups on the mill, checking the calibration of equipment, verify the accuracy of my work, etc. I think this means "workshop" grade (grade 2).

Are there any obvious pros/cons to look for?

If they claim compliance to some standard (eg: DIN861) can one consider the quality to be adequate?

Is 0.01mm resolution good enough, or are there reasons to go to 1 micron? My machines and measuring kit only go to 0.01mm...

Some of the sets I've been looking at...

88 piece set

56 piece set

Any advice gratefully received.

Thread: DIY magnetic DRO
28/11/2019 13:08:18

I've taken the plunge and ordered two read heads and tape, which I'll use for X/Y on my mill. If it's a success I'll roll it out to the mill Z axis, and maybe the lathe too.

I'm still pondering the pros and cons of the various ways to mount the tape to the table, thanks for the feed-back above. I like the simplicity of mounting the tape directly to the side of the table, and see the advantages of accessibility, but it makes mounting the read-head more challenging...


I've ordered the aluminium to make the tape bracket, should I chose to go down that path, as it was cheap, but I'll probably wait until I have the read-head and tape before I decide.

For the electronics I'm planning to go full DIY. Something like...

* RS-422 receivers to convert differential signal from read head to 3.3v single-ended.

* Small programmable-logic card to count the pulses and present the data on an SPI interface. This is timing-critical "real time" stuff, which I don't like leaving to software.

* Raspberry Pi with touch-screen, reading SPI data and running a DRO GUI. The software will be written in Qt (a cross-platform C++ IDE with decent gui/widget support)

I've used similar set-ups for other DIY projects so I'm not having to figure much out from scratch.

On a slightly different topic, I note that RLS also make rotary magnetic tapes, which are used in conjunction with the same read heads. Given that electronic lead-screws are en vogue, has anyone used a magnetic encoder instead of rotary optical encoders to track the spindle position? I imagine that the rotary tape could be fitted directly to the back of the spindle, and monitored with no physical interface, removing the timing belts and pulleys that I've seen the guys on youtube use.

Thread: Warco GH600
25/11/2019 20:56:52

Yes, the mechanism that attaches the lever to the control shaft is shoogly, and it can be depressed beyond the detent if you're not careful.

I hadn't thought this an issue as the tray itself stops you pushing it too far, but failed to considered the case where the lever is beyond the end of the tray...

Edited By Jed Martens on 25/11/2019 20:57:58

25/11/2019 17:24:11

Ian wins the prize, that red ball in the middle of the picture is the culprit. I had the carriage close to the tail-stock end of the lathe, turning a piece that was about as long as the lathe can manage. The lever was depressed to start the lathe (with power feed towards the chuck), and since I was watching the work, I didn't notice the ball hooking under the edge of the stand.

@Triumphboy, very grateful for the offer of help, but I'm up in Scotland

@John I think you're right, the top sheet of the stand is lifted a little around the front right corner of the lathe bed, which will likely have an affect on how straight the bed is. The irony is that the work I was turning was supposed to be a test piece to help get things into alignment - I've yet to seriously tackle getting the lathe set up properly. So at least I haven't undone any previous work in that regard. But now I need to do some metal-bashing before I can get back to checking if everything is true.

24/11/2019 15:31:09

Good guess, but the lathe is immobile. There was no other object involved, all damage was self inflicted.

The metal beating advice is much appreciated, as it's something I've never attempted before. As you say, yet another skill to master

24/11/2019 14:19:33

In other news, I had my first major oopsie with the lathe. I'm not sure if this a classic beginner's mistake, or my ineptitude is unique, but here's the result...


It's just bent sheet metal, that I might just be able to persuade back into shape. Does anyone care to guess how I managed it?

Edited By Jed Martens on 24/11/2019 14:20:24

24/11/2019 14:13:20
Posted by Triumphboy on 24/11/2019 12:25:54:

Hello Jed

If it makes you feel any better, I've wondered about the top table too but haven't given the time to think about it, so thanks for asking the question. laugh.

Yep, that does make me feel a little better :D There's no mention of how to operate the lever in the manual (no surprise there) and the diagram on the apron only illustrates two positions, so unless you're familiar with these things from previous experience, it is easy to overlook. That's my excuse anyway...

I haven't got around to fettling the gibs and so forth yet, but given my first attempt at parting was a bit of a disaster, it sounds like I should get onto it.

@Brian, sorry I missed your explanation earlier, your input since I purchased the lathe has been much appreciated.

24/11/2019 09:22:48

Thanks Bazyle - that explains it.

It still took a few seconds to figure it out. The lever appears to only have two positions - neutral and down (engages power cross feed). The third position is engaged by sliding it to the right and then up.

Thanks for the help


23/11/2019 23:56:39

I agree, that seems to be the sensible explanation...

But how to change between those two scenarios? The machine only has the one driven lead screw...

Unless there's some change-wheel combination that isn't obvious, the values in the top table appear unobtainable...

23/11/2019 20:51:12

I'm probably missing something simple here, but it's bugged me long enough to risk embarrassment on a public forum. I have no idea what the numbers in the top left table mean...


I'd always presumed they were feeds. In mm/s I would guess. There is a suggestion that facing is half the speed of turning, when using power feed, and that is indeed the case. But I can't make sense of the 0.044 figure (setting A1) for example.

What does make sense is the next table down, which is for thread cutting, and has a value of 0.25 for setting A1. The saddle does indeed move 0.25mm for each rotation of the spindle, I've checked with a dial indicator. I've also cut threads that work, so I'm pretty happy that the thread cutting table is correct.

But is 0.25mm / revolution the minimum feed rate? I was watching a youtube video where the machinist used a feed rate of 0.03mm / revolution, and checking the specs of his Emco 13 lathe, that is indeed the lower limit of feed rates. Is my minimum feed rate really ~ an order of magnitude higher?

It almost feels like there should be a change wheel or lever to switch between thread cutting and regular feeds. But I can't find a facility like that on the lathe.

Hopefully I'm just being daft and missing something simple. Humble pie is my favourite flavour


Edited By Jed Martens on 23/11/2019 20:52:12

Thread: DIY magnetic DRO
21/11/2019 12:35:19

I've been thinking about how to mount the magnetic tape and head to my mill. My idea is to make an aluminium bracket and bolt that to the x-axis of the table, with the tape on the underside facing down. The head will be under that facing up. As in the diagrams at the bottom of this post (apologies for my amateurish modelling).

Are there any obvious draw-backs to doing it this way? It seems that the whole ensemble is better protected from crude (and me dropping things on it), and the read head is easier to mount. I'll make an enclosure to fit over the read head too, similar to what Chris has done.



16/11/2019 20:18:40

Hi Chris - how is your magnetic DRO system working? I've considering using the same components for adding a DRO to my mill. I think the version with integrated RS422 driver would works best my case (differential signalling having better noise immunity)...

My main question - do you see any issue with using the high accuracy versions (~1/4 micron per edge, 8192 edges per 2mm)? Assuming the electronics at the far end can cope with the data-rate of course. I know that the mill isn't that accurate (and the operator even less so) but I see no obvious reason for going with a coarser output.

Thread: Warco GH600
18/10/2019 20:01:15

Hi Triumphboy, I'm a novice too, so I can't address all of your questions. But I think you can lock the saddle - if you look to the left and right of the cross-slide there are are a pair of socket-head bolts that hold the apron to the saddle. But on the right there is a 3rd bolt, above the other two, that can be tightened to lock the saddle.

I haven't used it yet, as I fear that I'll forget I've locked it and then engage the power-feed...

You can also lock the compound, but I've not found any way to lock the cross-slide.

Best Regards


Thread: Schaublin
02/09/2019 19:00:21
Posted by gerry madden on 02/09/2019 17:21:33:

Hi All,

In that good video the chap referred to 'precision ground stones'. I've never heard this term before, not even on this forum! Are these just ordinary stones ?


I believe they are ground flat. More info here...


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