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Member postings for Martin Connelly

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

Thread: Can anyone tell what these are for please
12/02/2020 16:43:21

If you search for images of Taylor Hobson Engraving machines you will see this part on some of them.

Martin C

Thread: cylinder boring
11/02/2020 12:38:17

Models of the Red Wing I have seen build logs for have piston rings. Is this the case with yours? It may make the order of cylinder bore and piston diameter less important.

Martin C

Thread: Cutting fluid
10/02/2020 13:32:13

Most modern cutting fluids are fine. I use a trigger spray bottle rather than flood coolant and only small quantities. I also use water from a rainwater butt to dilute it so it has no minerals or chlorine in it. Your tap water may be ok but why risk it if you have rainwater. I think the biggest problem is from flood coolant collecting in a sump and just lying there for a long time. I use a paint brush and RTD thread cutting oil for threading, just a smear on the surface is all that is required.

Martin C

Thread: gauge plate
10/02/2020 12:58:07

There is no grain, just grinding marks on the surface when supplied. Orient it the way that works best for you, polish it if you want to get a smooth surface.

Martin C

Thread: VFD drives
10/02/2020 12:21:55

The advertised VFD is probably for a single phase supply, you can get them for 3 phase supply. Have you mis-interpreted the specs? If you look at the terminals they usually have live, neutral and earth input and u, v, w output for a 3 phase motor. A 3 phase supply VFD will have earth and r, s and t for input. Have you got a model number for the VFD?

I have one of these (AT1) but notice in the paperwork there is a model designated AT2 which is for a 3 terminal single phase motor. I think in this case it is for a synchronous single phase motor and so is for a very specific type of single phase motor and not just any off the shelf single phase motor. If you buy one of these you will possibly need to get a suitable motor as well. The AT1 and new 3 phase motor may be the cheaper option.

vfd terminals (2).jpg

Martin C

Edited By Martin Connelly Picture added

Edited By Martin Connelly on 10/02/2020 12:44:28

Thread: Screwcutting on the lathe
10/02/2020 00:23:01

If you put a micrometer across the newly cut threads you will probably find the diameter has increased compared to the original stock diameter. There is usually some plastic deformation of material near the crests that pushes it out rather than perfectly cutting it. This is why you can buy full form threading inserts, they clean off this material. The problem is you need one to suit each thread size so are usually not worth the expense for hobbyists. It is also why the earlier advice to run a file over the new thread makes sense. The accurate way to measure threads is the three wire method which ignores problems with crests and roots but is probably over the top for you current needs.

The advantage of threading in the lathe is the thread pitch should be correct, the thread form should be axial to the stock and the thread can be made tight or slack as required. Cutting a thread with a die in a die stock with the material in a vice can result in wonky (technical term) threads. Using a die in a tailstock die holder may result in pitch errors if there is too much resistance to the die following the thread as it is formed. However once the thread has been formed in the lathe it can be polished with a suitable die in a die holder. If you have a split die start with it opened up and see if it removes some material. Try the nut on it and if it is too tight close the die slightly and try again. Repeat until you have a good thread.

Martin C

Thread: CNC conversion of axminster (seig) SX4
07/02/2020 19:13:30

The Axminster SX4 is similar to the Grizzly G0720R so searching for that may give the information you are after, they probably sell more machines in the USA than Axminster do in the UK. Here is someone selling kits for converting it and there is a link to a PDF instruction manual on the page,

Heavy Metal CNC

Here is a YouTube video of a conversion.

Martin C

Video added

Edited By Martin Connelly on 07/02/2020 19:25:52

07/02/2020 18:09:33

So it does, silly me.

Martin C

07/02/2020 17:46:57

Please specify which model you are referring to. Axminster sell a large variety of milling machines.

Martin C

Thread: Effect of Tensioning a Boring Bar
07/02/2020 17:41:01

DaveD, diameter being bored not the internal boring bar diameter.

Martin C

06/02/2020 15:50:11

It is a system not just a tube. Some of the system is in tension and some in compression. This is to some extent the same as a piece of hot formed bar where the core and the surface may have part in compression and part in tension. It may change the resonant frequency of the boring bar but thinking it is due to tension alone seems debatable. Best bet is the biggest diameter you can get away with.

Martin C

06/02/2020 13:01:00

Isn't the centre push rod under compression? Resonance is caused by a variety of factors, with a VFD it is easy to change rpm and go into and out of resonance. The stick out and stiffness of a boring bar, the rpm used, the depth of cut, the feed per rev, the geometry of the cutting edge and the material all have an effect. Change any one and you will get different results. I have read that putting a lump of plasticine on a boring bar can reduce chatter but have not resorted to it yet.

Martin C

Thread: What is This?
06/02/2020 12:46:22

The curved pointy ends look like o ring removal levers. Maybe a hydraulic cylinder servicing tool.

Martin C

Thread: A good 2D dwg package ?
06/02/2020 10:07:54

I recently looked at QCAD. The instructions for getting the trial widget to go away are out of date (at least for windows 64 bit version). I had to go to help/about/plugins on the menu bar to find which dll files were listed as part of the professional setup and delete them. Otherwise it does what is expected from a cad program, just slight differences from what I am used to.

Martin C

Thread: milling crankshaft on cnc mill using A axis
05/02/2020 14:39:15

Here are the test pieces from my Gcode. They are machined from a slug from a Rotabroach cutter which I saved for uses such as this and are 20mm diameter (roughly) and 25mm long.

Pins are 5mm diameter on a PCD of 14mm. Offset from one to the other is 120 degrees. Cutter was 1/4" 2 flute.

The pause from one pin to the next in the video is due having to edit the code for the offset of 120 then manually move the x axis then reset the a axis to zero to avoid a long reverse rotation to zero plus offset before running the code again.



Martin C


Edited to embed video instead of a link.

Edited By Martin Connelly on 05/02/2020 15:08:59

Thread: Clarke cl 500
04/02/2020 21:13:03

I have just seen the other thread regarding this lathe. I wonder if you have bought a machine that has had a three phase motor fitted already. The standard stop start wiring would be disconnected if this was the case. Single phase motors tend to be defined by rpm and 3 phase by poles.

Martin C

04/02/2020 21:03:11

Search ebay for 16mm shaft motors and see if one suits. Note a 3 phase motor and VFD is well below £400 so don't dismiss this as an option.

Martin C

Thread: milling crankshaft on cnc mill using A axis
04/02/2020 20:42:37

; This code assumes the units are mm, may work with inches but not checked.
; It is essential that the cutter is long enough to pass between the webs when the pin is at its lowest point.
; y zero and z zero (bottom of cutter) should be on the a axis centre line.
; Set x axis to suit your requirements for each pin.

M0 ; set a axis to zero if required to avoid long wait.

; The following parameters should be set by the user to suit the part being made.

#1=[10] ; Bar diameter
#2=[6] ; PCD of the crank pin
#3=[3] ; Crank pin diameter
#4=[6] ; Cutter diameter
#8=[0] ; Pin offset from TDC.
#9=[1] ; a axis rotation. Set this to -1/+1 if the a axis rotation is wrong direction. Check before cutting any material.
#12=[250] ; Set the speed to suit your cutter and material.
; The following are calculated parameters.

#6=[[#1 /2] + #2] ; Calculated z start height for first pass.
#7=[[#2 /2] + [#3 /2]] ; Calculated z finish height for final pass.
#5=[[#6 - #7] / #2] ; Calculated step size.

; The number of passes is taken as the pin pcd #2.

; This gives a step size close to 1mm but increases if the bar diameter is much larger than the pcd.
#10=[#2] ; Step counter for looping the sub-routine.
; Used as a multiplier to set the z axis before each rotation.
#11=[1] ; Adds 360 degrees to the angle each rev to save rotating backwards each pass.

; Initialisation
G0 G49 G40.1 G64 G17 G80 G50 G90 G98
M6 T1
M03 S4000

G19 ; Set circular motion to the yz plane.

; Start motion

G0 z[#6 + 2] ; Go to initial start height.
G0 a[#9*#8] ; Move a axis to TDC plus offset.
M98 P003 Q#2 ; Loop subroutine #2 times

; Polish passes.

G1 z[#7 + #5*#10] y[#4 /-4] F[#12] ; Reposition cutter to clean up more of the pin.
G03 a[[#9 *#11 *360] + [#9 *#8]] y[#4 /-4] k[#2 /-2] ; Circular motion 360 degrees.

#11=[#11 +1] ; Increase degrees multiplier for final rotation.

G1 z[#7 + #5*#10] y[#4 /-2] ; Reposition cutter to clean up the centre of the pin.
G03 a[[#9 *#11 * 360] + [#9 *#8]] y[#4 /-2] k[#2 /-2] ; Circular motion 360 degrees.

G0 z[#6 + 2] ; Go to initial start height.
G17 ; Set circular motion back to the xy plane.
M5 M9 ; Turn off spindle, coolant etc as required.
M30 ; End program

O003 ; Circular motion subroutine.

G1 y[#4 *-1.5 *#9] F[#12] ; Move slightly to one side.
#10=[#10 - 1] ; Multiplier for z height.
G1 z[#7 + #5*#10] y0 f[#12 /4] ; Ramp down to inital cutting position for circular motion.
G03 a[[#9 *#11 *360] + [#9 *#8]] y0 k[#2 /-2] F[#12] ; Circular motion in yz plane 360 degrees.
#11=[#11 +1] ; Increase degrees multiplier for next rotation.

M99 ; End subroutine.

Had to delete spaces to post it.

Martin C

04/02/2020 20:38:01

After my earlier posts in this thread I read the earlier thread referred to on 3 Mar by Jason and was very surprised to see that it was claimed by John Stevenson that using G19 got complicated quite quickly. I have written a new parameterised program that uses rotation in the yz plane (G19) that should give a better finish than the 360 facet version that John used. I have also added two polishing passes at y=1/4 and 1/2 of the cutter diameter off the a axis centreline to reduce barrelling of the pin. I have given it a physical run and it works fine on my machine. I will set something up tomorrow to photograph and video.

I have not tried to make it efficient so it still does a lot of air cutting but it does not rotate the a axis back to zero with each pass.

The code is posted in the next post due to character limitations, if spacing looks odd it was done in a text editor with fixed character width.

If yo want to see the toolpath in Mach 3 you need to drag the window around with the left mouse button as the default view shows nothing.

Martin C

Thread: New Nimrods arriving
04/02/2020 13:15:21

My wife's cousin has industrial deafness which he blames on being aircrew on Shackletons for many years.

Martin C

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