The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)

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awemawson:
Miserable fellow - you could have picked up my M10 couplers from Screwfix AND had a cup of tea :lol:

awemawson:
At long last I've been able to get a bit of time to return to this project. Life (or rather death) had got in the way. Sadly one of my long term flat tenants died suddenly leaving rather a mess to sort out, shame as he was a nice chap and very reliable (but his next of kin is in Panama!) and another problem tenant left again leaving a horrible mess. It all takes time, and not an inconsiderable amount of dosh to sort out.

However today I did actually manage to knock up a little G code program to surface the 'spoil board' and then sort out the CNC mill to mount it and machine it. The material is some very gummy aluminium alloy that I can't seem to get a good surface on, but that's OK it isn't particularly critical so long as it is flat.

The spoil board at 300 x 330 mm is pretty much the largest object that I can mount and work on with a 50 mm face mill without running into the limits set on the machine. In deed to find the centre I would normally use the Heidenhain probe, picking up each edge, lie to it to say that it was circular, and use the centre as X=0 Y=0, but the probe can't go far enough past the edge to work, so it was an eyeball job!

I used my Mitee-Bit clamps to edge hold it as the machining had to run off all edges, but first I hand filed the 'nasties' that have accumulated over the years, removed the heavy Kurt vice, and had a detour / diversion mining in the swarf to rescue the Allen Key and Tee nut that I managed to drop in there :bang: This plate was a test sample I was given literally decades ago and it has at times had to live outside

No more playtime as it's guest check out / check in time

awemawson:
I managed to get a little more done this afternoon between tasks.

The spoil plate needs a circle of eight M10 x 1.5 mm holes drilled and tapped to marry up with the matching circle of 15 mm holes in the billet clamp flange. So a bit of transferring co-ordinates from the flange drawing, specifying an 8.5 mm drill and M10 spiral flute tap in the tool crib, then actually mounting them and measuring their Z off sets before . . . Pressing the button :bugeye:

It's always a bit bottom clenching waiting for the machine to smash your tools to shreds and ruin your work up to date, but no - it all worked without dramas and the billet clamping flange is loosely mounted.

The M10 hold down bolts are in 15 mm holes in the flange which I hope gives me sufficient wiggle room to get things aligned when I have to invert the billet having machined one side - time only will tell !

I may cut another machinable wax as a test before doing the EN19T billet - haven't decided yet

. . . back on duty now . . .

awemawson:
It occurred to me that if I were to loose the X=0 Y=0 setting on the machine that determine the centre of the circle for those bolt holes it wouldn't be easy to re-establish it - unlikely as the machine control maintains them, but better safe than sorry so I need a feature that I can get the probe at (as the plate edges are too close to limits for the probe to work)

So this mornings fill in job while waiting for the postman was a nice and simple task - bore a 25 mm hole 20 mm deep accurately on the centre as previously established

Apart from checking that the loaded 22 mm slot drill WAS centre cutting, and that it's Z offset was correct - dead easy. So now if we have a power glitch etc I can get back to where we are now. Probably always sensible to incorporate some such feature in a part - even a spoil board !

awemawson:
I've Fallen Down Another Rabbit Hole

Today's 'simple' job was to turn a plug to go in the 25 mm hole in the spoil board incorporating a 10 mm upwards facing spigot, then fair face one face of the EN19T billet and centre drill and ream a 10 mm hole for the spigot. So the first action was to confirm that the hole in the spoil board WAS accurately 25 mm. A rough check with digital verniers lead me to question it.

So I dug out my 'Insize Digital Bore Gauge', a nice bit of kit that I've never used as someone had dismantled the probe end and not put it back together properly. A bit of intelligent 'looksee' showed that they'd fiddled with the range setting - easily corrected with a pair of miniature spanners. Checking against slip gauges showed that it was working fine .Note the picture with the gauge blocks shows it reading 4 microns undersize - that's just me not having zeroed it.

OK measure the bore in question gave me 24.894 or about 100 micron undersize - but why ?

At first I was sure that the 22 mm slot drill that I had used must be undersize as I've never had reason to question the accuracy of the Beaver Partsmater positioning system. A crude and rough check with a digital vernier seemed to confirm this but it's very difficult to get it bang on the maximum diameter of a two flute cutter - or at least I find it difficult.

So time to bring out the big guns - the PCM Toolset Tool Setter - BUT the extreme cutting edges of the two flutes at the tip were pretty well bang on at 11.007 mm and 11.020 mm.

Remember that the program orbits this 22 mm cutter to form the 25 mm bore -an undersized cutter will give an undersized bore and vice versa. If anything this cutter is very marginally oversized at 22.027 or 27 microns too fat.

So where is the error? Well I don't know, hence the rabbit hole comment, I need to find the source of this error before I proceed any further, so I think that I need to do more tests with other cutters and see what errors I get.

It can't be an undersized cutter as I've measured it

It can't be a bent spindle or holder as that would make oversized holes

The program doesn't leave a finish allowance so that's not it

Here is the program in Heidenhain conversational language

0 BEGIN PGM 14 MM
1 L Z0 R0 F15000 M91
2 TOOL CALL 10 Z S1455
3 L X0. Y0. R0 F15000 M6
4 L X-0.23 Y0. R F M3
5 L R F M8
6 L Z2.54 R F15000 M
7 L Z-20.0 R F192 M
8 L X-0.829 Y-0.781 R F384 M
9 CC X-0.074 Y-0.74
10 C X-0.15 Y-1.493 DR+ R F192 M
11 CC X0. Y0.
12 C X-0.15 Y-1.493 DR+ R M
13 CC X0. Y0.
14 C X1.5 Y0.034 DR+ R M
15 CC X0.744 Y0.017
16 C X0.842 Y0.767 DR+ R M
17 L X0.018 Y0.229 R F384 M
18 L Z25.4 R F15000 M
19 L Z0 R0 F15000 M91
20 L R F M2
21 END PGM 14 MM

So please if anyone has any suggestions I would very much like to hear them.

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