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Member postings for Will Bells

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

Thread: Gear cutters- DP,Mod and Pressure angle
12/09/2015 01:38:25

Hi John

Unfortunately the pressure angle (pa) of the cutters mean that they are not compatible. I must admit that I have not checked the size properly, but I think the PCD of 32dp is probably about 10pc bigger than .8 mod which sounds too much difference for any speed.

Practically if the speed is slow and you are not bothered about wear or noise (and you calculate the new centre distance correctly) then yes they will probably run together, but if you want a nice smooth running pair, then no.

Regards - Will

Thread: Brush finish on Stainless Steel
11/09/2015 16:51:25

Anyone out there perfected the art of a brushed finish on stainless sheet with the usual range of DIY power tools ?

I can get a great finish using scotchbrite on stainless tube in the lathe. That turns out really well.

But on a flat sheet I have only seen professionals do it with some sort of proper drum burnishing machine. Actually it was someone resurfacing a Delorean bonnet on Wheeler Dealers, which I don't have ( neither the tool nor the car).

Cheers - Will

Thread: Machining Hard Materials
11/09/2015 16:38:43
Posted by Andrew Johnston on 10/09/2015 21:59:29:

I've also milled HSS tool blanks without issues when I need to remove significant metal before finish grinding.

Andrew

Hey Andrew - Doh, Guess it's obvious, but I never thought of machining HSS cutting tools before, that's smart. Do you use standard carbide cutters or coated / special ones for that (before I make an expensive experiment)

Cheers - Will

Oooops - Trigger Happy  sad

Edited By Will Bells on 11/09/2015 16:41:28

11/09/2015 16:32:10
Posted by Andrew Johnston on 10/09/2015 21:59:29:

I've also milled HSS tool blanks without issues when I need to remove significant metal before finish grinding.

Andrew

Hey Andrew - Doh, Guess it's obvious, but I never thought of machining HSS cutting tools before, that's brilliant. Do you use standard carbide cutters or coated / special ones for that (before I make an expensive experiment)

Cheers - Will

Thread: Twist drill speeds
28/08/2015 19:28:46

Oh dear ..... slightly embarrassed blush

I select my medium speed for drills and my (geared) low speed for tapping and for the very occasional big drill. I have no idea what speeds they are.

My drills are not broken or burned and my holes tend to be reasonable round. So it works for me

Cheers - Will

Thread: Multiple machines from one inverter
27/08/2015 00:48:07

Hi Robin -

I think there are different types of phase converters and the more expensive ones work as Jon described. They are often called Plug and Play type because they act just like a rotary converter.

The cheaper VFD type that most of us buy for one machine are not capable of running more than one machine at a time or switching at the machine.

Cheers Will

Thread: Educating me - Work hardened?
02/08/2015 12:46:38

Hi Pgk

Sounds like you did well to get it to the parting stage.

The good thing about getting material from scrappies is that it can cheap.

The bad thing is you mostly have no idea what you have.

Chances are you have a defunct half shaft from a crashed Morris Marina. Tough as old boots, hence the good finish with carbide but a worn HSS parting tool.

As tempting as it might be financially, I don't do that any more - I put my short hands into my long pockets and buy stuff I know the grade of. Goes against my Northern roots though .......

Cheers - Will

Thread: Arduino project with stepper motors
18/07/2015 14:08:08

Hi Muzzer

First the warning - I'm a hammer yielding mechanical engineer; the finer points of CNC control are certainly beyond me, so I arrived at a working solution by good luck and perseverance rather than skill !!

So to answer the MESA question, I don't use either to control the motors. I used the DMM controller board for the motors and the emergency stop and fault functions, which seemed an easy first step, plus a Mesa 5i20 inside an old HP Pentium computer feeding a couple of MESA 7i37's for the rest of the i/os.

img_0755.jpg

I suspect using the DMM board, which uses DIR and STEP is doubling up on some of the capabilities of the 5i20 and probably compromising the performance, but it works really well for me, so I don't really understand it so have not tried to optimise it - let sleeping CNC machines lie is my adage.

The base machine was a Defiance Innovations small high speed CNC mill, an American company that went under in the early naughties, so no support and next to zero information is available. It was a capable machine originally, fitted with some good stuff, but I ended up replacing the motors, all the control system and even the spindle (field burned out, so perhaps one day I will have it rewound and get auto tool change back) plus totally rewiring. OK, I admit, it was mostly for the fun of it.

The photo below shows the machine (note this morning I removed one of the bellows for repair as it had become torn and I am paranoid about keeping motors dry now).

img_0752.jpg

img_0754.jpg

The nice thing about the Defiance is it's an accurately built machine with proper ball screws, slides and lubrication and even with the refit it is cutting very accurately. I run it quite slowly though, with the maximum velocity at 500mm/min and generally cut no more than 350, which means that so far I have been able to run it off a 13A domestic socket without having to put a bolt back in the plug fuse holder ***

Linux was OK to set up and once I'd got my head around how the program was structured, the I/Os were straight forward to add. You are more than welcome to have set up files if you want them.

img_0753.jpg

Using the machine is easy - I also use Fusion 360 to do the CAM bit and it writes G code in almost perfect LinuxCNC without any code manipulation, unlike another big CAM system that I previously had access to. I never leave it running alone, but It's got to the stage where I trust the code and I'm so confident I don't normally do a dry run of new code, just let it go straight into cutting metal. You watch, later today, having made that claim, I'll plough a big jagged channel into the bed ...

Lastly, I am aware that I still have not got adequate fault protection and it's surprising how many IOs are required for a half decent set-up. Obviously the DMM board has a watchdog and other fault protection, but I still need to be more clever on the spindle side. If this stops rotating for any non obvious reason, I will be caught out and the Chinese spindle does not have sensors as did the original. I am starting to work out what signals I need from the VFD to catch more faults, which I will sort shortly.

Cheers Will

*** DEAR SAFETY ELVES, ONLY JOKING ABOUT THE BOLT, HONEST angel

18/07/2015 09:15:39

Hi Muzzer

I also used Mesa/DMM/linuxcnc on my mill and it works a treat. Brilliant actually.

I did make a stupid oversight initially where I didn't fully protect one of the servos from the suds (was under bellows and part shrouded) and the encoder went haywire which cost me dearly. Obviously the DMM motors are not waterproof, nor would I expect at the price, so I added additional shrouding and sealant. That not going to happen again.

So would highly recommend

Cheers Will

Thread: What's your best tool purchase ?
16/05/2015 00:27:09

Best Purchase ?

Perhaps not strictly the best, but I have some simple quality tools bought second hand, that I really enjoy using.

First to spring to mind is an eclipse tap wrench. Honest, quality tool that has the edges worn smooth through (I like to think) hours of useful past work.

Worst ? Yep, I agree, cheap, bargain tools that break first outing and have been replaced. I tend not to get "duped" like that nowadays !

(brilliant topic Peter, by the way)

Cheers - Will

Thread: Problems with G-code etc.
10/05/2015 14:16:52

Hi Bob

Perhaps if you post some of the lines of code someone may be able to help, but the 500th line does sound suspicious.

I know absolutely nothing about SputCam, but I do know that not all GCode details are the same between systems. Perhaps you have not selected Mach3 in SputCam ?

Whatever, good luck. Will

Thread: Asian High speed ER collet spindles
06/05/2015 21:46:10

Hi John

I bought a 1.5kw water cooled spindle off ebay which I use on my CNC milling machine. Brilliant for the price and has run for many hours without a hiccup.

I use it down to 3000 rpm without problems - but as JS says, it's probably not meant to run at that, but it stays cool with a proper chiller and runs well.

But there's not a cat in hells chance of using a 12mm cutter in it - 6mm in aluminium is on its limit. Steel with a 4mm is about right.

Cheers - Will

Thread: What did you do today (2015)
22/02/2015 23:33:17

Andrew - that's a crisp piece of screw cutting. Very nice indeed !!

Cheers - Will

Thread: Moving a heavy lathe
20/02/2015 21:08:16
Posted by Neil Wyatt on 20/02/2015 20:47:05:

You need one of these:

Neil, as Editor, do you have a special direct help line to them, just in case things go badly wrong, such as a postal strike ?

Cheers Will

20/02/2015 20:57:23

Hi Fizzy

If you can get enough height on the engine lift, then I agree with Capnahab. Stripping it is not the best idea if you can avoid it.

My hoist is sturdy enough, but wouldn't lift a lathe high enough, so I moved a reasonable sized Denford lathe and a Horizon mill on a hired car transporter/trailer. The sort that hitches to a car, has a tilting bed, a winch and a full solid bed (ie, not one with just a non-structural central composite board strip). I did it single handed and without drama, but not both at the same time.

On both machines I made bars (twice the lathe width) with swivelling wheels on the end, which I bolted to the machine through the feet holes to make them stable and let me move them around OK.

So get it to the trailer, drop the bed, use the winch to get it so far up the bed (to the centre of the pivot point), wind the bed down, then position the lathe in the middle and make sure it's absolutely secure. Drop off is the reverse.

It's probably a bit over the top and unconventional for most, but it worked well for me and because the car trailers are long and wide, they are very stable.

BUT I warn again, not all trailers have the right construction.....

Cheers - Will

Thread: Parting Off MEW225
18/02/2015 23:20:08

So, having chewed on that, I now have to wonder why on earth did classic HSS parting tools always had such a big top rake ??????

Cheers - Will

18/02/2015 21:53:34

Hi Neil

(Sorry Cabeng for jumping in here)

The sweet force shown as Fa is the force acting in the horizontal direction by the work onto the tool tip. The reason for the force comes from the tool being wound into the work.

I know you know that, but think along the lines that if it didn't exist, the tool would sink into the work piece without anything to stop it and all the force would be purely vertical, which clearly isn't true. The diagram is shown as the forces on the tool tip, so it's the force required by the work piece to oppose the tool.

The diagram could have been drawn with the forces imparted by the tool on the work and they would be equal and opposite.

Cheers - Will

18/02/2015 19:45:21

Hi Cabeng

The force diagrams look very sensible to me for normal turning regardless of the tool shape within reason.

But I think Chris' point about a parting tool with zero top rake versus large top rake coupled with backlash is very relevant. A small top rake, such as shown on your Carbide tip photos is likely to behave as Chris says and not want to dig in under reasonable use, regardless of backlash (my guess), which also matches your force diagram nicely.

A HSS parting tool is normally ground sharply with a high top rake, used at slow speed and fed so that the cut is actually quite high per rev. The bigger the top rake, the more the resultant for F will tend towards the vertical (down) direction but theoretically, it cannot go past vertical unless something else is happening.

It's most likely that the chip thickness is that "other something".

So my guess (and that's all it is) is that the dynamics are along the lines of .....

Wind the tool in which cuts normally. Either a gnat's more force or feed rate than is necessary to keep the status quo takes a higher cut, increases the chip thickness, changes the resultant force direction and uses up spring or backlash in the system. And, digs in!

I suspect that parting with sharp tools with top rake at slow speed is inherently unstable with our class of lathes, so thanks to the boffins that gave us Carbide for those of us without the skills to work on a knife edge.

Thank you Cabeng for providing some great analysis and driving a challenging discussion for all of us.

Cheers - Will

Thread: "New" Old Stock Kasenit; Does it expire?
17/02/2015 18:34:37

Think mine's from the 80's. Grab it while you can

Will

Thread: Parting Off MEW225
16/02/2015 10:45:56

Hi Cabeng

The sprung tool that I made was not like the swan-neck variety. Because I wanted to control the geometry and I had no idea how the spring system would behave or whether it would work at all, I made the tool holder part of a pivoted swinging arm and added an adjustable compression spring. The tip definitely swings down and out by a meaningful amount when it needs to as the pivot is close to the front and higher than the tool.

In terms of chatter, with the current lathe it's not a problem. I'm sure that I have had chatter at some point when starting, but I cannot recall a specific event so it's rare.

I do not use auto feed with the Carbide tool. I like to control the cut by feel and keep the chip constant (I think deep down I am still psychologically damaged by early attempts), but I do feed at a reasonable rate, yes. When I first made the swing tool I did play around with it extensively and I used the auto feed sometimes then, primarily to see if the constant feed would help things.

Cheers Will

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