Oh Blimey I bought a CNC Lathe !!!!

[vtsteam]

I know your widgets are to be copper,Andrew, but have not yet gleaned their function, unless I missed it somewhere back. If secret at this juncture, carry on, But otherwise, what the heck are they?

[awemawson]

No secret Steve.

Did you see my thread regarding the Stud Welder? It uses copper collets to hold the studs, and because of the huge discharge current between the collet holder and stud, they are expendable lasting maybe 100 studs before they are consumed.

I have a few in a limited number of bores, but decided to do 'a run' of 3, 4, 5, 6 & 8 mm collets  as a 'production exercise'. I'm trying to make it so they are made effectively in 'one operation' involving boring and slitting the gripping end and boring and threading the adjusting end. This is just an excuse (and learning exercise) to play swapping parts from the main spindle to the opposing spindle so that the part can be worked on on both ends.

The collets are available commercially and frankly aren't very expensive, but that's not the point 

[dsquire]

No secret Steve.

Did you see my thread regarding the Stud Welder? It uses copper collets to hold the studs, and because of the huge discharge current between the collet holder and stud, they are expendable lasting maybe 100 studs before they are consumed.

I have a few in a limited number of bores, but decided to do 'a run' of 3, 4, 5, 6 & 8 mm collets  as a 'production exercise'. I'm trying to make it so they are made effectively in 'one operation' involving boring and slitting the gripping end and boring and threading the adjusting end. This is just an excuse (and learning exercise) to play swapping parts from the main spindle to the opposing spindle so that the part can be worked on on both ends.

The collets are available commercially and frankly aren't very expensive, but that's not the point 

Andrew

Isn't that the point, if you can't make it for twice the price it wouldn't be any fun.

Cheers 

Don

[vtsteam]

Makes total sense to me, Andrew.

[awemawson]

Playing with the soft jaws I got fed up not 'quite' locating them in the right serration. They have 60 degree serrations at 1.5 mm pitch, and you'd think it dead easy to slap the three of them on and bolt them up so they all sat in the same radial position prior to boring for accuracy. Several times I'd put a set on, torque the bolts, spin the chuck and there'd be one very obviously one serration out. 

Fed up with this I made a little gizzmo. Fit one jaw, set the gizzmo to it, fit the rest using the gizzmo - works a charm 

Took all of an hour to make

[mattinker]

Hi Andrew,

I'm glad I dropped in before Christmas, your posts have taken on new meaning knowing the context in which they're set!

Best wishes, Matthew.

[awemawson]

Matthew it was nice to meet you and your son. Open house, kettle's always on 

[mattinker]

Love to drop in again, but it'll be a while before I get over again!

Regards, Matthew

[awemawson]

Fed up with craning my neck round trying to read DTI faces upside down and back to front, I went on a hunt through my measuring gear and came up with a long forgotten Mahr Feinpruf transducer driven high resolution measuring whatsit.

Actually this has been sitting on the shelf for a year waiting for a 'round tuit' as it's input mains fuse holder is flopping about and needs replacing, and it's resisting all attempts to get inside the box !

[awemawson]

So last nights 'get you to sleep' design exercise was a holder to allow me to swing the chuck mounted probe round the test piece, and this is what I came up with, and was duly made first thing this morning

[awemawson]

So popping it in the chuck having slackened and hand tightened the tool holder bolts it took all of ten minutes to tap the tool mounting block round on it's circular Tee slot to zero out the error, and re-torque the bolts.

I am amazed how accurately you can tap things with a plastic mallet to shift them a few microns. The indicator in this picture shows zero, where full scale either way is 3 microns, which indeed is where I got it at the four quadrant points, but that's a bit deceptive, as the ball screw backlash and indeed just leaning on things moves it a few microns.

Just need to re-pack it with grease and put it back together. The replacement O ring arrived yesterday (3 mm cord by 164 mm id), available on ebay for less than £3 delivered !

[awemawson]

So now that the 'tool mounting hole' centre line lies on the axis of the lathe I can tweak the machine parameters to accurately set tool offsets. The value of X in this picture (which I'm putting here so I can refer back in the future ) is the absolute position of the X axis to get on centre

Before all the tweaking the value was 137.832, but that difference of 0.152 mm is not all 'X' and not all 'height' as the tool mount has been rotated to zero the error

[Pete.]

Neat tool Andrew. With it reading so fine, do you leave any allowance for flex in the holder when turning the probe from 12 to 6 o'clock?

[awemawson]

Pete the holder is very stout - obviously there must be flex but frankly plus or minus 10 microns would be absolutely no issue in this situation.

[Pete W.]

Hi there, Andrew,

I think I might be able to match that fuse holder if you need to replace it.  It might take some digging to find it, though!       

If your fuse holder is broken send me a PM with a close-up photo.  I do know I've got a few of the type with the 5/8" fine thread fixing nut (I used one of those nuts to load the quill bearings on my Tauco bench drill!)          

[vtsteam]

Andrew enjoyable to watch you work out every problem and improve this lathe.

The mallet adjustment reminds me of my first disappointments using a 4 jaw chuck, having plunked down good cash for it. I was used to tapping pieces on the Gingery lathe faceplate with a plastic mallet to center them. Using an indicator, you rotate the faceplate by hand, find the high spot, tap to half that reading and rotate to check. Tighten hold down bolts or whatever and go. What used to take literally seconds on the faceplate now took minutes of cranking back and forth (for me) with the 4 jaw.!

Later discovery through Doubleboost of the two chuck key method of adjusting a 4 jaw helped a lot, but sometimes I still feel that the faceplate tapping method was faster and easier for me. The only reason I didn't go back was because I wanted to train myself to use the 4 jaw quickly -- and because the faceplate on my Craftsman lathe has a big hub which blocks the most useful part of the slots. Most of the old workholding fixtures I made for the Gingery are too small for it.

Anyway, sorry to go on -- I love the fact that even on a big complex CNC machine, tapping with a mallet works well for precision adjustments sometimes!

[awemawson]

Hi there, Andrew,

I think I might be able to match that fuse holder if you need to replace it.  It might take some digging to find it, though!       

If your fuse holder is broken send me a PM with a close-up photo.  I do know I've got a few of the type with the 5/8" fine thread fixing nut (I used one of those nuts to load the quill bearings on my Tauco bench drill!)         

Thanks Pete, I'll take a photo

Steve thanks for the kind words - just now trying to get my head round the various offsets that have to be set to compensate for the tool post position - the description is just a bit stark! I need to work it from first principles

[awemawson]

Pete,

With your encouragement I have at last fathomed out how this thing comes apart and managed to remove the broken fuse holder.

The original is a Rafi 1.04002 rated 6 amps @ 250 volts and holds a 20 mm fuse. Thread diameter is 14.75 by measurement (nominal 15?) and protrusion behind the panel cannot be much more than 30 mm including the terminals.

(It turned out that what appeared to be holding it together was actually holding an internal assembly on)

[Pete W.]

Hi there, Andrew,

Red face here and big apologies to you!!!                    

I should have ensured brain was engaged before operating keyboard!!!   I deserve a session of     or even of 

All the panel-mounting fuse holders I have are for 1¼" x ¼" fuses.  You'd be welcome to have one or a few of those if only I could find them!!!  I think they're in a cardboard box, in a bigger cardboard box, in a cupboard, behind lots of heavy stuff!!

I'm sorry if I've caused you to dismantle your instrument for nothing.   

[awemawson]

Pete thanks for looking - the offer was much appreciated 

As it was apart I grafted a slightly smaller (12.5 mm thread) holder in by sandwiching it between two suitable washers, so at least the instrument is now much safer to use and I know what's inside. It looks like it grew like Topsey, rather than being a decent paper design - definite look of a prototype inside - in fact quite a bodge, but it works splendidly. I have a slightly more modern similar instrument by a different maker, but it has the same sensor connector - I tried one in the other and amazingly they are compatible so maybe there is a standard.

[awemawson]

At the request of PeteW I'm posting some details of the ISOMA centring microscope that I'm using to help me set the correct tool heights on this lathe.

I've been assured that setting height using VDI30 tools is easy, as the top surface of tools is in alignment with the tip height, and the upper surface of the tool holder is on centre line. However in my experience neither of these theories is correct by quite a distance 

Now on a manual lathe I'm antediluvian, and use the 'trap a 6" ruler 'twixt tip and work and set to vertical' - works for me, but in this machine firstly it's all inside a sealed enclosure, secondly the X axis is slanting  at a steep angle, and thirdly the tool is held upside down as it is on the far side of the work from the operator 

Hence experimenting with the ISOMA, which I've had for decades but have rarely used.

I'm afraid the 'through 'scope' shots are pretty dim - but that's the way it is 

[awemawson]

I've been experimenting with increasing the illumination - currently it's a 15 watt 6v 210 lumen microscope bulb and as you see, rather dim. I ordered a Chinese torch claiming to use a 2200 lumen CREE LED - this would not only have had a much brighter light, being battery powered it would avoid me having to unplug and reel in the cable every time the door has to be shut to make an adjustment.

However it would seem no brighter than the original lamp, so I have to assume that Chinese lumens are approximately 1/10 of standard lumens

Bit of a give away that it claims 12 watts, whereas I measure a best case of 4.9 

[Manxmodder]

Nice scope,Andrew.
Seems the torch seller doesn't know their watts from their wotsits,or their lumens from their lanterns 

Maybe a better description would've been 'as bright as one chinese lantern' 

.....OZ.

[Pete W.]

Hi there, Andrew,

My lovely but shy assistant wonders what you're doing in the workshop - shouldn't you be outside lambing?

I take it that your third and fourth photos are using the original Isoma lamp, am I right?

I suggest that you do a check with the 'scope off the lathe to see if the image is erect or inverted.  Draw a target on a piece of paper and look at that, perhaps.  Conventional compound microscopes give an inverted image but the Isoma has a prism to send the image to the screen - it could be erect in one axis (e.g. conventional X) and inverted in the other (conventional Y)!  You need to know before you can move forward.

If you use the LED torch instead of the original bulb, will the LED light source be in the same place as the Isoma bulb was? 

[awemawson]

Pete, we have a theoretical two to three weeks before lambing, but you never can be sure so we have an 'emergency bay' set up in the stable just in case.

Yes the dim pictures are using the "13347W" 6 volt 15 watt ba15 based T6 shaped bulb. Not yet tried the led  - I'd intended to dismantle the torch and just use the cree LED so that I could get it in the same plane as the  bulbs filament, but as it's no brighter there seems little point.

Seeing which way up is simple - I just rested a thin feeler gauge on the tip - then you can see which is the cutting face I'm interested in 

(I think I've rotated one of those pictures too many quadrants  )