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Member postings for John Haine

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

Thread: CNC Knurling
06/09/2021 12:55:01

Martin, actually it's 42 passes in each direction and the "tooth angle" is 8.571 degrees. It makes one cut right-to-left turning 360*, then another L-R turning another 360 in the same direction. Then advances by 8.571* and repeats. Since the diameter is 12.7mm the leads is pi x 12.7 = 39.898 mm for 90* diamond knurls. The A axis always goes the same way to avoid backlash problems.

This works when the length is equal to the lead, for shorter lengths it's more involved especially if you want to avoid lots of waits while the rotary axis moves to the next position.

DC31K, I started by thinking how deep the "teeth" should be for comfy gripping - I decided no more than 0.5mm. Then had some geometry for the depth of cut for a square tooth and used a spreadsheet goal-seek to find a convenient cut depth to give an integer number of teeth. Bit of trial and error gave me 42 and a cut depth of 0.492 mm. Actually it's less than this as the geometry isn't quite as I thought when you cut crossing "threads" and the peak diameter is reduced to 12.15mm.

Edited By John Haine on 06/09/2021 12:56:22

06/09/2021 12:39:05

Ian, the sheet does both. It has a section that calculates the dimensions, feeds etc needed, then these are converted into g code using formulas such as this:

="G00 X1 Y0 Z"&($H$3+1+C3/2)

The first bit quotes just writes G00 X1 Y0 Z into the cell. The & symbol in Excel concantenates this with what comes afterwards, which is the result of the calculation in the brackets which just contains standard cell references. The result in this case (for certain parameters) is

G00 X1 Y0 Z67.595

I'm cheating here because I've inserted some of the numbers by hand, but in other examples I've done all the numeric values are inserted from other cells in the sheet. So once I've built the sheet I can generate the code for specific dimensions by just changing the parameters. Done things like tapers, cams, crossing out, special pallet profiles for clocks etc.

06/09/2021 11:04:59

I have seen something on the web about using an endmill, but have never been able to find it again! Difficult to do a fine knurl as I think you have to have the cutter offset to one side and at 45* to the axis, so anything but a small cutter produces quite a wide tooth. The engraving cutters are carbide and about a fiver for 10 from China!

Thread: Tom Senior
06/09/2021 10:25:35

Ketan Swali at **LINK** is a mine of information on bearing types and may well be able to advise on what to get. Could also supply from the UK or given his international contacts recommend a supplier in Thailand. Bearings are usually made to global standards.

Thread: Good morning all, new member here.
06/09/2021 09:51:26

Welcome, and inverter = VFD. Well worth fitting.

Thread: CNC Knurling
06/09/2021 09:17:26

The recent thread on knurling tools triggered me to go back to a project I had in mind to try knurling on my CNC mill using the rotary axis.

pxl_20210410_115434268.jpg

I wrote a little spreadsheet to generate the g-code. Basically it uses an engraving cutter to mill a spiral groove along the workpiece whilst rotating it - initially for simplicity I'm making it move for one full lead while rotating 1 turn. On a half inch bit of brass that's ~41mm lead The cutter has a 90 degree point with a small flat (basically a PCB engraver). Hare are some pics of the first trial.

pxl_20210905_211158063.jpg

pxl_20210905_211253512.jpg

Came out quite well though it took a long time - just over an hour. I wound't want to do it much faster as the spindle speed is a bit low (~6000 rpm) for the cutter. Also the depth of cut is slightly too large as I forgot the flat on the end of the cutter, and the number of "teeth" could probably be reduced. Sufficiently good though that a better "wizard" that can generate shorter knurls is probably worth writing, though the calculations are more involved. I now have some knurled bar to make a small batch of thumb nuts!

Mod edit: rotated photo.

Edited By SillyOldDuffer on 06/09/2021 10:50:04

Thread: They see you coming
05/09/2021 08:57:15

Years ago my boss acquired a newish Vauxhall from his father who couldn't stand the rattling it made any more. The agents couldn't find anything wrong so in desperation he bought a different car and handed it on to my boss for a suitable cash adjustment. My boss didn't like the noise much either so did some delving and found the loose spanner left under the back seat....

Thread: Machine Lamp Recommendation?
04/09/2021 14:00:29

+4 for Jansjo from Ikea. One on each mill, one on lathe, one general purpose gets moved around.

Thread: I need to cut chamfers into x64 pieces of mild steel - any advice?
04/09/2021 12:40:58

From another thread...

**LINK**

I think the OP has plenty of advice now, I suggest he makes a choice of method and has a go and reports back.

Thread: Aldi belt & disc sander
04/09/2021 12:39:05

That link looks dodgy - try this one

**LINK**

Thread: optical mystery parts
03/09/2021 20:53:33

You may have a Nicol Prism.

https://en.wikipedia.org/wiki/Nicol_prism

Thread: I need to cut chamfers into x64 pieces of mild steel - any advice?
03/09/2021 20:11:36
  • Given you have invented your new product some similar ingenuity applied to designing the production method would be a good idea. Usually any product designer would consider the manufacturing method as a design constraint.
  • If you don't do it by hand, either the mitre will have to be milled or ground - people have described how you could do the job either way.
  • Since it's clearly not cost effective to buy a mill for this one job I think an abrasive disc machine is more likely to do the job for you. As Howard suggests setting up a mitred clamping jig and a fence to control the depth is the way to go. You have shown one of the blanks sitting in a vee block - how could it be clamped in that position (hint - consider a round bar clamped in the vee to hold it)? How could you then use the vee block as a jig (hint - run the fence in the groove machined in the side of the block)? Think carefully about the risks and work safely.
  • Is the chamfer essential, could the design be modified to work without it?
Thread: optical mystery parts
03/09/2021 16:15:10

Iceland spar?

Thread: XYZ AT4 VFD Parameter For Slow Start
03/09/2021 16:14:01

If you mean a clamp on current transformer, whatever you measure the volts with it's the same - rms or peak.

Thread: Myford super 7 lead screw
02/09/2021 18:28:34

I have had mine off once to adapt the RH end to fit a timing pulley. As far as I can recall it was very easy to re-fit, need to remove one of the bearing brackets depending on which way you want to feed it in. If it's not going past the apron the most likely reason is either that the half nuts are closed or they are misaligned. Did he dismantle the Apron too?

Thread: Newman Motor Star To Delta?
02/09/2021 15:54:01
Posted by Andrew Johnston on 02/09/2021 11:29:43:
Posted by John Haine on 01/09/2021 22:53:35:

So a star connected motor expects to see three phase wires and one neutral wire..........

None of my machine tools, running on a 3-phase supply, have a neutral connection; just the three phases and earth. In theory at least for a motor running in star there would be no current flowing in a neutral wire connected to the star point, which is why it is not connected.

Andrew

Yes, that's quite correct you don't need a connection to the motor star point, I should have said that you could connect the neutral to the star if you wanted to. Of course if you want to run a single phase pump, or axis drive, or worklight, then either you need a neutral connection or a 415:230 V transformer.

01/09/2021 22:53:35

Whoever wrote that web page for Inverter Supermarket should hang their head in shame! A awful bit of explanation.

And could I just repeat, yet again, that a "normal" 3 phase supply is ~400V phase-to-phase, but nominally 230V phase to neutral. When single phase is delivered to our houses the neutral comes from the STAR point of the substation transformer and we get one of the 3 phases as the live. So a star connected motor expects to see three phase wires and one neutral wire, and each winding sees 230V. However ordinary VFDs can't generate that much voltage because of the way they work, but can generate 230V phase to phase, which is why you need to reconnect the motor into delta so each winding sees 230V. Just to repeat, a "415V 3-phase supply" from the mains is just 3 "230V single phase supplies" where the supplies differ in phase by 120 degrees.

Thread: Tightening a Threaded Bolt
01/09/2021 11:40:02

Can you get a nut on the back?

Thread: Is the EV industry in too much of a hurry ?
01/09/2021 10:12:57

Whereas petrol or diesel of course is entirely safe...

Typical petrol car has a tank capacity of 40 litres, the energy density of gasoline is 33.2 MJ/litre so the stored energy is ~1200 MJ. Tesla model 3 battery has a battery capacity of 76.5 kWh so stored energy is 76.5 x 3600s x 1000 Ws or Joules = 275 MJ, about a quarter of a fully filled petrol car. Battery volts is 375, comparable with the peak mains volts. Skills for safe working surely comparable to a domestic sparks - and they aren't so skilled these days in my experience!

01/09/2021 09:25:34

I seem to recall a few huge refinery fires in recent years and I believe the incidence of ice vehicles self combusting is around the same as EVs. If you store a lot of energy in a small volume it's inherently somewhat risky and low probability risks only show up in high volume production.

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