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Member postings for Dave S

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

Thread: Tapered Square metal punch anyone?
22/08/2020 20:16:05

Click spring over on YouTube has a video showing how:

**LINK**

Seems fairly straightforward

Dave

Thread: Is a drip feed coolant advisable
01/08/2020 08:58:25

Don’t think I’ve ever used coolant on my Unimat.
I do have flood on the CVA and the Grinder, and use an oil can on the mill.

To clear swarf I keep a value tooth brush with each machine.
Having a reasonably long handle means hands clear from cutting tool, and the bristles/handle are soft enough to cut if it gets too close.

Dave

Thread: Change chuck on a seig c0?
31/07/2020 14:05:50

On my Unimat 4 (essentially the same) I open the belt guard and hold the pulley whilst unscrewing it.

There is a cross hole in the back of the spindle you can use to stop the spindle rotating of a gorilla has screwed on your chuck. In that case an adjustable spanner on a chuck jaw and a pin punch through the hole would do the job

Dave

Thread: Hardening EN8?
30/07/2020 22:01:53

I thought the point of filing buttons was that they were dead hard and so the file just skated over them?

Dave

Thread: Shellac questions
30/07/2020 17:39:53

Try holding a relatively long thin (say 0.5-1mm diameter and 10-15mm long) part to work on the end with superglue.

With shellac you can drill a hole, fill it up, warm it and then insert the part.
You can make the part run true with a little heat to soften and some careful pressing.

As with most things tool related it’s having the knowledge of the easy way which makes life simpler.

Dave

Thread: Static balance gadget
28/07/2020 19:35:40

I made the ends of my grinding wheel balance arbour the size of the largest bearings I had hanging around, IIRC they were about 15mm ID/30mm OD

I flushed out the bearings with wd40 to remove all the grease and then set them into v blocks.
That is sensitive enough to detect a a small out of balance on an 8” wheel, such that the spindle weights moved together make it rotate quite quickly.

Can you make the ends of your arbour small and do a similar thing?

Dave

Thread: Part breakout /fixturing
03/07/2020 21:54:29

Evening all,

Now my CNC has potential to work nicely I'm thinking about making things

I will be making some small watch parts, mostly 2d in general shape. I think I can effectively cut these out of sheet stock, but what's the best way to fixture it?

Additionally what do you do to prevent the part breaking out and jamming/snapping the end mill.

For general size the would be parts that require 1mm or smaller endmilll to get into internal radiuses, and typically 1mm or so thick.

I occurs to me that I could use (say) 1.5 mm gage plate,surface the top by 0.25, cut around the part leaving 0.25mm bottom stock. Then fill the "gutter" with shellac and flip over, probably on my surface grinder to remove the 0.25 left.

Any better techniques?

Dave

Thread: Measuring Gears (including pressure angle)
03/07/2020 16:52:43

Another method, assuming involute teeth:

Take some plasticine or other softish clay like material, create a small block on a flat surface and then roll the gear over it.

The matching rack form is then created and the pressure angle can be measured directly with a protractor from the sides of the flanks.

Dave

Thread: 2mm endmill help
01/07/2020 13:52:54

I stuffed the endmill into the collet further - as I could do now its ER16. This spindle is loads quieter, both cutting and idling.

I'll run the job from scratch once the bearings are sorted, but I am also interested - that should allow me to tune which is where I started this whole thing.

Dave

01/07/2020 13:03:59

Good news!
My CNC failed to snap my last 2mm endmill last night
The Job started:


and then it progressed some

As it was all looking good I even went and sat in the garden with a beer, keeping an ear out for the noise.
I was back to watch the pocketing process, as the rest of the cuts were small width, and this was the full width, after all the other milling.


took just under 2h20.

End result of the roughing pass:

Somethings gone wrong here, the pocket is supposed to be a curve:


Turns out the recycled bearing on the X Axis has collapsed/ jammed.

Must have happened pretty much at the end, as the other shapes look OK.

That's why I took the stock off - cant run the finish on it until the leadscrew is sorted, which means stripping the table out...

Still, massive progress, and the new spindle seems to have made a difference.
I think its now in the 'tune' stage, rather than the throw things at it stage

Thankyou all

Dave

29/06/2020 15:30:33

Many years ago I needed to do some very small precision drilling, so I bought one of ARCs ER16 high speed spindles.

That project got done and as part of workshop tidy the spindle got packed away for “later”.

I don’t think they still sell them, but similar spindles can be found out of China.

it runs of an invertor, 750w and 4-24k rpm IIRC

Bit overkill for this mill I suspect, but already in the workshop and should solve the runout issue.

Seemed worth a try for the time investment

Dave

29/06/2020 12:57:16

I've had a busy weekend in the workshop:

I didn't manage to run the CNC , but I did manage to re-spindle it:

Its all assembled, and the runout on this spindle is around 2 tenths with the same end mill as the proxxon one measured 2-3 thou. Speed should be more stable (and upto 24K rpm), and with the ER16 collets I can choke down to reduce the stick out.
I still need to check/fine tune the tram, and ensure the stepper is ok with the additional weight. I did a quick check before making the parts by cable tying this spindle to the existing head, and it drove that OK, so I think it should be fine.
Hopefully Ill be able to report success later in the week.
I'll also look at getting some different cutters if this moves ok - with ER16 I'm no longer limited to the 3.2mm max diameter, so the cutter selection should be wider.
There are pictures of the build on my twitter feed : @SolutionsByDave if anyone is interested.
Dave
26/06/2020 20:15:16

I have no idea how to drive a CNC, the little I did was many years ago. So I guessed a tool path, based on the few things I remembered being a typical clearing path as was.
I’ve never “run the numbers” as such on my manual mill, it’s built like a brick outhouse and being manual you can “feel” how the cut is going. It’s a while since I snapped a mill, iirc the last one was a 12mm rougher that I took an overly optimistic DOC into 316.

Im having a “family night” but hopefully some garage time at the weekend will allow me to try some more.

Ive already learnt loads and the video of a successful 2mm cut is encouragement.

If I’m being overly optimistic on my machines capacity maybe I need to rethink my longer term plan, but for now it’s the only CNC I’ve got.

Dave

26/06/2020 13:07:39

I sort of expected to break a few things on the learning path, but I was hoping it wouldn't all be at the start....

I clocked the runout on the shank of a cutter held in the collet where it exits the spindle. As I did this with 2 different sized collets I assumed it was the spindle, but maybe all my collets are a bit 'wonky'

Ill clock the actual nose tonight.

Does your spindle feel 'steppy' when turned by had - way stiffer than it fells like it should be? I assume this is cogging on the spindle motor, so if another one does then Ill ignore that.

Might also try a different lump of steel. My other mill has not trouble with this stuff, but then is full sized industrial and I rarely use less than 6mm dia cutters on it - its top speed is about 4500 RPM.

Dave

26/06/2020 12:47:46

Yes, as suggested by Jason - engaging more of the flute length in the cut, but with shallowed stepover. It felt like that was a sensible thing to try - it spreads the wear over more of the cutter - rather than relying on just the tips.

Sort of like vertical slab milling (if you squint a bit)

Dave

26/06/2020 11:27:59

Sad news, another 2mm endmill has been sacrificed to the cause of getting my CNC to work.

I used Jason's suggested toolpath - although I did re-generate it first as I moved the work coordinates.
However the basics were as he suggested: 0.2mm engagement, much greater DoC.

It all started promisingly:

And it made a couple of the passes all round to the back side before I was called to eat:

During the meal I was keeping a ear out, and when it all went silent I returned, mid meal(!) to discover an ex-endmill

So I paused the machine, and went and finished my steak and had a beer.
Seem the most productive thing to do at that point...

On the plus side the swarf looks more 'swarfy' than last time:

I put the part under the microscope, this is where it snapped from the side:

You can see the not quite left the metal cut that was in progress.
From the top there is no obvious extra width of cut:

I managed to find the end of the endmill from where it had been thrown behind the lathe.
It shows a single tooth has more wear that the other 2, and one of the other 2 appears to be poorly formed in the first place, or possibly chipped - its very hard to tell.

For comparison here is the last unused 2mm, not snapped one:

The edges on that however look distinctly rubbish compared to the 1mm Kyocera mill

After a serious dose of thinking about it I measured the runout on the tool - using the as yet unsnapped 2mm which has a long shank - ideal for an indicator to run on. approx 0.076 mm (a little over 3 thou). With a toolpath supposed to take a side cut of 0.2mm this is quite a significant change in cut load per rev I think.

I also checked with a 3mm tool, in case it was the collet - same result, so I guess that's the natural spindle runout.
I think I need less runout than that to successfully use tiny mills - certainly if I put in a 1mm end mill and the runout is nearly 10% diameter that sounds bad.

Should I formulate a new spindle plan at this point?

Dave

25/06/2020 17:59:30

I did some looking at my mills. The 2mm is about 10mm flute length, the real killer I think is the shank length:

Fresh one, last nights snapped one and the proxxon collet. The spindle bore is solid about 1/2 mm from the collet end, so you can see in the next photo how much extra stick out there was because of shank lenght:

Thats about 8mm extra, nearly doubling the stickout.

I also bought 3mm and 1mm, and they also have super long shanks compared to collet length.

Ive chopped a 2mm down (I bought 3 2mm as its the size I'll mostly be snapping using) so I can give that a go with revised tool paths tonight (SWMBO permitting)

Dave

25/06/2020 17:51:34

My conversion was done when I had little money, so its scavenged bits from printers and hacked together mounts. The handles are in the mill box, shoudl I ever be mad enough to want to use it manually - I really like my TOS, even for tiny things.

Overview shot, please excuse last nights swarf and spanners...

The X and Y ends have been replaced with alloy, which have pockets for the bearings to sit in. They are held there only be the lead screw tension. I had to turn a couple of adaptors to fit the inside bearing bore - where the leadscrew is thinner for the handle mount.

For the Z - because the lead screw is just 'hanging' I made a new top from bike crank arm with a pocket for back to back magneto bearings:


The top plate is held on with the original screws, which are a bit long at the front, but at the back they also hold the stepper mount piece - scavenged from an old dot matrix printier IIRC.

IT all looks a bit heath robinson, but the motion part seems to work ok. I built the stepper control box and PSU - this was before simple availability from China.

If you want any more details info just ask.

Dave

25/06/2020 13:41:08

I've not got to backlash yet - first I need a part...

However my plan is to try and remove it. The screws into the plastic lead nuts are pretty much backlash free, and I have the leadscrew 'stretched' between bearings, with back to back magneto bearings on the Z.

Ill post some pictures of the setup later if its of interest. A friend of mine had the same setup before he sold his mill and moved to an X1 based conversion - IIRC his was pretty much bang on, one of the reasons I picked up the MF70 (spindle speed was the other).

Originally I was running parallel port and tried Linux CNC and Mach 3. This was many years ago - somewhere around 2010 I think. So the tooling was not very simple, and I wasn't interested enough in battling computers after a full on day of real time control software writing.

Now with Fusion and its CAM processor the tooling is much nicer. Just hope that the CAM module remains available for hobbyist use, I'm quite against an annual subscription just to play in the garage - If it was a cost of making money its easier to swallow, but that's a whole other set of things to discuss

I have had a RepRap since around 2012 - and its tooling once sorted is good enough, with the USB interface working with most computers. That and the lack of parallel port machines that were reliable in my garage prompted the move to a USB interface, which lead me to GRBL in a round about way.

Dave

25/06/2020 12:48:08

Fusion link:

https://a360.co/2YuDK6X

I've added another setup with smaller stepover, and DoC. It was doing 1.9mm stepover. Hopefully I can try it tonight when I get in from work

I thought the surface wasn't that bad, but if it can get much better I'll be very happy

Ill take a Dremel to the shank and choke down on the tool as much as possible. I'll also get some smaller flute length mills. Didn't really think much about that aspect when I ordered them. My other mill is 1.7 tonnes, but I don't really use less than 6mm in that.

This is one of those times I miss the clumsy bstard, with a wealth of helpful knowledge 5 mins up the road.

Still this forum has given me lots to try, and some encouragement that I should persevere - Thank you all.

Dave

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