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Member postings for DC31k

Here is a list of all the postings DC31k has made in our forums. Click on a thread name to jump to the thread.

Thread: Looking for DRO system with an output pulse on zero
01/05/2021 15:06:16
Posted by Clive Foster on 01/05/2021 13:13:31:

I do wonder just how difficult it would be to intercept the display driver for the usual inexpensive import DRO box and interrogate that to find all zeros so the power feed can be stopped.

But even if you did that, it will not mimic a fixed mechanical stop or a manually-controlled stop on a DRO zero. And it is that part of it, I do not think you yet appreciate.

Just switching off the power feed will stop at an indeterminate and unrepeatable position. Just think what might influence it: cutting load, slide friction, speed it is going when you switch it off.

Under the hood in Mach, etc. there is a lot of maths going on before the soft limit switch or zero count is reached. It looks ahead and takes action because it knows how far away it is and what it is doing on the approach to it. The stop comes as no surprise.

In a similar way, it is why you would always rehome the machine after you hit a hard limit (or the big red button). For that situation, the stop signal comes as a complete surprise to the machine. It does all it can to stop as fast as possible but the actual position in which is eventually comes to a halt is indeterminate.

01/05/2021 11:37:46

As you say, Mach 3 and LinuuCNC have the capacity to do what you want. Both ot them will have an internal variable in the stlye of CURRENT_X_AXIS_VALUE. You would have to write a macro that runs continually and compares that value to your required one and then dives off into an interrupt routine that rings the bell when the values become sufficiently close (not necessarily 'equal' ).

To do this in principle in either program is not difficult, but it is the time and effort spent learning how to do it that will weary you.

Someone has posted here an Arduino sketch that does a DRO summing (quill and knee). It would be possible to use that as a building block for what you want. You can intercept the signals from the scale, let the relevant part of that program decode them and them perform the routine described above for Mach. You would need to give it both the current value and the desired value so it can do its work.

The main thrust of this is to suggest you do some trials on the human-machine interaction aspect of your idea before going much further. Stopping something moving on the sound of a buzzer (triggered by your pulse) is not repeatable. What you do at the moment is to look at the DRO display, see how close it is to zero and how fast it is changing and adjust your handle turning to suit.

Rig up a dial indicator and a microswitch-triggered buzzer on the machine. Set the bzzer to sound when the indicator is at zero. Now cover the indicator and drive into the microswitch. See how close to zero you get. Repeat nine more times.

An analogue dial with a moving hand (or its on-screen equivalent) or even watching the numbers of a digital display count down will help you a lot more than a single tone.

Think of it in reverse: starting an athletics race or the Christmas tree at a drag race. The best athlete is the one who goes on the 'B' of the bang, not the 'G'. The winning car is the one that takes off as the lights start to dim, not when they are fully extinguished.

If you want to take the quadrophenia route, then the parking sensors on a modern vehicle might be a good model. The programming is not trivial as it has to take into account not only distance but speed and acceleration. It would be interesting to experiment to see if you can stop your car the same distance from the brick wall every time, just using the onset of the continuous tone to guide you.

Edited By DC31k on 01/05/2021 11:39:44

Thread: Inroducing lathes article in 303
27/04/2021 07:48:29

Your point is valid, but with a little thinking, it is not a great challenge to work out which line relates to which material.

Given the following list of materials, in what order of cutting speed would you rank them?

Tough steels, hard cast iron

Silver steel, stainless steel

Mild steel, cast iron, bronze, gunmetal

Free cutting steel, brass

Aluminium and its alloys

Plastic and wood

Thread: Gear, Gauge, or Cutter ?
26/04/2021 19:04:04

The cutter infeed, or tooth depth, is normally written as D + f, where 'f' is the clearance. Perhaps Dathan liked gears to be cut with a little extra clearance.

I suspect the calculation of 'D' will be the same whatever tooth geometry you choose.

Law gives 'f' as 10% of the tooth thickness at the pitch line, so Dathan's percentage might simply be bigger. Similarly, maybe the percentage for other geometry might differ.

Thread: Does anyone know what this is for?
26/04/2021 11:57:49
Posted by Nigel Graham 2 on 25/04/2021 23:02:13:

If so the lower wheel might be a Crimp Roll

There are a couple of challenges with the crimp roll theory. First, with a smooth upper roller, it is difficult to see how it would form a crimp. How is the metal pushed into the tooth spaces of the lower roller? Hand-held duct crimping pliers are like a pair of scissors with multiple blades (e.g. that form the crimp in the gaps.

If you ran a sheet of metal through that, the part of the metal where the teeth of the lower wheels contact it would be thinned, so the overall effect would be as a stretcher rather than shrinker. It is like hitting the edge of a piece of sheet metal with the cross of a cross pein hammer: you thin it and stretch it.

Second, the lower rollers have circumferential grooves in them so the imprint would be like a series of five Morse code dashes.

If it does its work on the left side of the machine as photographed, the big gap in the centre of the machine seems somehow wasteful.

Thread: Arris rail support brackets for concrete fence posts
25/04/2021 10:01:05

Toolstation code 92651.

However, on wooden rails the tenon is cut flush with the flat side of the rail. With the brackets, the tenon is relative to the pointy side of the rail so the position of the fence with respect to the centreline of the post will change or the fence will be out of plumb if you do not modify all rails.

The screw on ones can be used with a concrete post, but it might be better to use a non-hammer drill (such as a 6mm dia. diamond tile drill) for the rawlplugs.

Thread: Calling all Colchester Bantam owners.
25/04/2021 08:25:49

Fourth post in this thread:

Thread: Gear, Gauge, or Cutter ?
24/04/2021 14:54:19

It is a cutter for a gear shaper.

Perhaps the best known manufacturer of the machines that use it is Fellows. In the UK, Drummond made one.

There are some YouTube videos by them on 'The Art of Gear Generation' and the Vintage Machinery site has a copy of their book of a similar name.

Dathan were or maybe still are a gear specialist.

Edited By DC31k on 24/04/2021 14:56:08

Thread: Faster Screw-Cutting
24/04/2021 14:47:52

As a description of its function, 'leadscrew dog clutch' is OK. As a description of its location, it is maybe a little misleading. It needs to go immediately on the end of the spindle, before any gearing changes the angular relationship between spindle and leadscrew.

In some sense, it might be better described as a 'spindle dog clutch'; it is all about point of view - are you disconnecting the spindle from the leadscrew or the leadscrew (and all its associated gearing) from the spindle?

So, yes, it can go before a QC gearbox. It must go before the QC gearbox. It must go a considerable way before the QC gearbox, on the first place the machine sees the 'output' of the spindle.

Until I understood its operation, I often peered at the six-tooth dog clutch that disconnects my leadscrew from the gearbox, so the screw does not rotate when not required, and wondered if I could replace it with a single tooth one. I understand now why that is not possible.

24/04/2021 09:10:41
Posted by Chris Crew on 24/04/2021 08:41:44:

Something in the back of my mind tells me that Martin Cleeve also designed a similar 'gizmo'.

Martin Cleeve is generally remembered for his single tooth leadscrew dog clutch, detailed in his book and designed for many other machines by Graham Meek. It may be this that you are thinking of when Cleeve's name comes into your mind.

It achieves the same effect (stops the carriage moving under the action of the leadscrew) but in a different manner. Rather than opening the half nuts, it disengages the dog clutch using a spring action trip that has no significant delay.

The advantage of Cleeve's design is that the half nuts stay engaged so it can eliminate the need for a thread dial indicator and overcome language (imperial//metric) difficulties. A consequence of that advantage is that you have to reverse the leadscrew (maybe by a handwheel at the tailstock end) to reposition the carriage on threads where resynchronisation after opening the half nuts would be difficult.

Thread: Best way to cut/turn a 75mm Disc from a piece of Aluminium Plate
23/04/2021 19:37:34
Posted by Nigel Graham 2 on 23/04/2021 17:01:19:

However you don't need worry about the arbor thread, nor the pilot-drill, because those are supplied.

And if you do not want a 1/4" hole in your offcut?

Or you do not mind a hole, but you would like it to be no more than 4mm dia?

Or you have limited headroom and want the arbor to go directly into the Morse taper of your machine?

Or you do not like the 13mm A/F hexagon shank on a standard arbor?

Or you do not like the idea of holding a 10mm dia. SDS shank in a collet?

With holesaws, the bought-in arbors confine you to a certain path: a home brew one allows you to tailor something appropriate to your own needs. And for that, the arbor thread is about the only thing that is important.

23/04/2021 15:31:25

Next size up is 73mm so unlikely to leave enough for finishing.

I think the arbor requires a 5/8"-18 UNF thread but Google will confirm.

Superglue on a thick sacrificial disk and use a shortened pilot drill if you do not want a hole in the offcut.

Thread: Clarke AC180 ‘Automatic Battery Charger’
22/04/2021 07:12:29

From this page, which hopefully will not crash:

Clarke International
Shrubland Road
E10 7RB

Main Telephone Number: 020 8988 7400
Fax Number (all Departments) 020 8558 3622
Email: For ALL Departments - Click Here
Business Hours: Monday to Thursday 8am to 6pm, Friday 8am to 5pm
Find Us on Map Click Here


The trade counter is closed until further notice due to Covid-19. If you wish to contact us either email

Edited By DC31k on 22/04/2021 07:13:05

Edited By DC31k on 22/04/2021 07:13:32

Thread: Harrison M300 Taper Attachment
19/04/2021 19:57:29

If no-one comes up with measurements for you, do you have a manual for it?

There is one here:

and the same one here:

Print out the exploded isometric drawing of the TT attachment and scale off the size of the parts you do not have using one of the parts you do have as a reference.

There is a good photo of one here that you can use for scaling:

Edited By DC31k on 19/04/2021 20:10:41

Thread: Looking for a block of cast iron please
17/04/2021 14:20:53
Posted by Howard Lewis on 17/04/2021 12:16:52:

When you tighten the clamp screws for the tool, the cast iron is subjected to tension.

To quote from the original post "a toolpost support for my Chester DB10 to replace the compound".

Could you please posit a mechanism whereby a toolpost SUPPORT will be subjected to the tensile forces you mention.

I find it of great utility to read all of the words actually written in the original post rather than to omit or imagine some.

Thread: Greenwood Tools
17/04/2021 14:08:03
Posted by Mike guitar on 17/04/2021 12:54:30:

Kit-qd.....I've tried contacting on eBay viz spare inserts...I'm just trying to locate the manufacturer which will enable me to buy spare inserts

Greenwood's website is still alive and well. Details of the manufacturer (Sandvik) are given there and the insert code(s) are all there also.

Thread: Threaded milling cutters
16/04/2021 14:59:48
Posted by Dave Halford on 16/04/2021 14:26:11:

You only need 4 sizes of collet

6mm 10mm 12mm 16mm

I have those. I tried a 1/2" shank cutter in the 12mm one and it was a little tight. The collet did not seem much use afterwards so it might be an expensive way to work. Similarly, the 16mm one was a bit loose and it was difficult to remove the mill after welding it into place.

Thread: Kuroda Boring & Facing head
14/04/2021 19:14:49

Everything below implies it is a clone of the Wohlhaupter UPA3...

Thread: 5C collet chuck with integral DI-3 backplate,anyone bought one?
14/04/2021 14:30:17
Posted by Dave S on 14/04/2021 08:43:38:

I usually use the sleeve as it’s direct in the taper, and the drawtube is a little shorter.

But you can only use 5C in-spindle if the spindle taper will accommodate it.

If you happen to have a D1-3 with a 4 Morse taper, which is how I believe the Bantam is offered, it is too small. It is why 4 1/2 Morse was added to the range as it is the smallest that will accommodate 5C.

Thread: Abrasive belts
13/04/2021 07:34:26

Abrasive belts are specified by width and circumference and then chosen by grit.

So if you have the machine, cut open a used belt and measure it. Or use a piece of string.


where it appears that the width is the same but the girth differs by 5mm, which might be within the adjustment range of the tensioning mechanism.

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