Boxford 5C Collet adapter

[Wedg1e]

Following on from my thread about the 'mystery' spindle taper on the VSL500, I've made a start on the 5C collet adapter.

I'd already used the lathe's reducer to set the topslide at the requisite angle for the taper, so a length of EN3B was squared both ends and centred in the 4-jaw.
Then battle commenced, with a carbide tool that had previously been chipped and reshaped on a diamond wheel. It proved to cut very nicely:

Once I'd got 'somewhere near' the right diameter I started removing the chuck and turning it round to try the adapter in the spindle (bloody autofocus picked the wrong target):

and then once it was 'very close' a quick smear of marking blue confirmed the fit (the un-blued area is where the adapter clears the bottom of the taper in the spindle so no contact):

Not a bad finish for carbide, I thought...

Next, I drilled a good 80mm or so deep up to about 8mm diameter, then drilled out the narrow end...



and tapped a short length to M12:

Time to part off, and although I knew exactly where I wanted to cut it I chickened out and made it over-length, which meant the blade was a bit close to the chuck (the coolant is pouring into the cut here):

Yes, I know you're not supposed to part off with tailstock support; I didn't complete the cut with the parting tool but used a hacksaw instead as it was a deep trench and the blade kept nipping. Eventually it was free, and removed from the 4-jaw...

A length of M12 studding was then wound in and the adapter mounted to the spindle...

...with a nut and some washers to pull it down firmly into the taper:

The idea, of course, was that when I opened out the collet bore it would have absolutely no choice but to be bang-on centre with the headstock spindle

 

[Wedg1e]

The adapter had reached this stage:

...but that big chuck nut would rattle about unless I used the 3D-printed retainer/nose protector that I found online and ran off overnight at work - you can actually take the nut off, if you remove that small socket-head screw in the front face of the chuck nut, but let's do the job properly...

Facing the parted-off end eventually broke through into the pilot bore...

...which was then opened out with successive drills to about 16mm, by which time I could get a boring bar in there:

This bar took the bore out out to about 22mm or so, and then it was time to swap for a meatier one (autofocus gets it wrong again )...

The 5C collet is nearly 32mm diameter so there's a good bit of swarf to be made yet - note the end of the M12 studding...

Eventually I'd got the hole just clearing the threaded section of the collet (about £7.50 from Chronos, 6mm chosen at random since I don't have any (yet))...

...at which point successive short excursions of about 0.02mm were made until the collet could just be persuaded to enter the bore:

The tool was run to full depth, the swarf and coolant wiped away and... [Churchill] Ohh yesss

Interestingly, at least to me, is that the boring bar got the hole on size to full depth in one pass, where I often find I have to take multiple passes at the same setting to counter the spring of the bar. Maybe it's the quality of the material (55mm diameter x 100mm long, about £13 posted from an Ebay seller).
Next I need to take some more off that front face, so I can get the collet closing taper deeper into the adapter. Five minute job
Meanwhile I've ordered a length of thick-walled 35mm CDS tube, which will become the closing drawbar...

 

[Ton-up]

Have you seen the Acrogrip 5c collet closer @bR39Da had for sale?

What is this...

Hi Brad, could you measure the diameter of the Acrogrip collet tube if you have one please.

www.mig-welding.co.uk

 

[Agroshield]

Maybe have a good think about any machining still left to do at the back (M12) end before shortening the front end.

Are you just going to shorten the back so the 5C threads poke through the adaptor or will the adapter be bored so it envelops the drawtube?

If you take away too much at the front, you might not be left with much parallel and concentric material with which to grip it to work on the back.

You might need a dog-point grub screw in the side of it to act as the key, to stop the 5C rotating.

What is the internal diameter of your spindle compared to the OD of your closer tube? You might need a (plastic) ring near the threaded end of the tube to encourage it to stay centered in the spindle bore.

 

[Seadog]

The VSL has a bore of 1-3/8", Brad.

 

[Wedg1e]

Maybe have a good think about any machining still left to do at the back (M12) end before shortening the front end.

Are you just going to shorten the back so the 5C threads poke through the adaptor or will the adapter be bored so it envelops the drawtube?

If you take away too much at the front, you might not be left with much parallel and concentric material with which to grip it to work on the back.

You might need a dog-point grub screw in the side of it to act as the key, to stop the 5C rotating.

What is the internal diameter of your spindle compared to the OD of your closer tube? You might need a (plastic) ring near the threaded end of the tube to encourage it to stay centered in the spindle bore.

The collet (once seated on the closing taper) is longer than the closer so the threads should be proud, but if the back end wall permits I was thinking of thinning it to accommodate the drawbar/ tube just to ensure full engagement with the collet.
Appreciate the thought about lack of material to grip; the idea was to back the studding off and get the bore as deep as possible from the front end so there's little to do at the small end, any error would be of minor significance as the parallel shank of the collet would be fully engaged in the closer. I tried it again this morning with everything cold and it's snug to say the least. I surprise myself sometimes.
Good point about a key; I'm used to ER and Autolock-style chucks where the collet is closed from the front, not the back. Sounds like an excuse for some brass-mangling - and a work-holding job for the dividing head.
AutoCAD suggests I can take 3mm off the front of the 'flange' before starting the closing taper; much shorter and the wall at the point where the flange meets the external taper becomes a bit thin. I wanted to allow a bit for potential future 'touching-up'
Have already anticipated the drawbar needing a centring ring, however 1-3/8" works out at 34.925mm and the tube I've ordered is 34.94 +/-0.2mm (allegedly) so there won't be much in it - the tube might need a shave, if anything. Not looking forward to the internal thread, though - luckily I bought a metre of tube so there's scope to salvage a cockup.
I've been contemplating the required accuracy of the closing taper angle; the collet is 10 degrees but obviously the closing action compresses the collet to some degree so a small imprecision in the taper shouldn't matter... I hope
I'd rather not take the closer out until that taper's turned, so using the collet to set the topslide angle would be a tad difficult. I'm sure the VSL's angle gauge is close enough - I reckon the concentricity is more important.

 

[Wedg1e]

Have you seen the Acrogrip 5c collet closer @bR39Da had for sale?

What is this...

Hi Brad, could you measure the diameter of the Acrogrip collet tube if you have one please.

www.mig-welding.co.uk

Now you tell me

 

[Agroshield]

I'd rather not take the closer out until that taper's turned, so using the collet to set the topslide angle would be a tad difficult.

Have a look at one of your own photos above with the collet 3/4 of the way in the closer. If you check it for concentricity in that position and then put some light retaining compound on it (superglue), you could use the collet's own taper to dial in the compound.

 

[Wedg1e]

Have a look at one of your own photos above with the collet 3/4 of the way in the closer. If you check it for concentricity in that position and then put some light retaining compound on it (superglue), you could use the collet's own taper to dial in the compound.

You're right.
And when you're right, you're right.
And you, you're always right

Something like this (after I'd taken 3mm off the front face)...

...and the VSL's angle scale isn't a million miles off 10 degrees either:

Boring commenced, but although it made a good job of the parallel bore, it didn't cut as nicely on the taper, although the clearances looked OK. I found it worked better coming outwards from the bore:

You can see some less than brilliant bits here...

This was as far in as the collet would go at this stage...

Once I'd got the closing taper almost to full diameter I slackened off the M12 stud a couple of turns, nipped it back up and went back to deepening the parallel bore. It took a few goes but eventually the studding was hanging on by about one turn. Then the cutting tool nicked it and spat it out, but the closer showed no sign of moving in the spindle so I cracked on with the boring bar and took out what was left at the far end...

...then, with a final tickle on the closing taper the collet slid snugly in:

A small chamfer just to take the sharp edge off (I realised it needed a quick redo once I'd taken the photo)...

You can just about make out the closer from the far end of the headstock spindle (Boxford clearly didn't think it needed a mirror finish):

Next: the drawbar.

 

[Agroshield]

Would you consider the 5C collet cheap enough to be expendable? If so, Loctite in a piece of rod of the correct diameter, chuck it up in a cordless and lap the taper of the closer to a finish with which you are happy.

It would be wise to consult someone like Pete. or pressbrake1 who would advise you on the correct lapping compound (you do not want it to embed into the closer. There is one called Timesaver, which seems to fit the bill).

 

[Wedg1e]

Need to update this, plenty more photos so will do that tomorrow (or is it today now?)...

Brad, the boring bars have a square shank with a round section leading to the tip, so the stickout is what it is (I think about 50mm on one of them).

Agro, sounds like a plan but at this stage I'm more concerned with getting the parts finished so I can see whether it all works, I'll do the vajazzle afterwards

As it stands, the drawtube is finished, I've threaded a bronze nut and am making an alloy handwheel to pull it all together. There's a handwheel on Ebay but it's for the smaller 3C set - and £30! I've had divorces that cost less

 

[Wedg1e]

Right, where was I?
Closer finished 'near enough', it was time to address the drawbar - sorry, drawtube, it wouldn't be as much use if it was solid.
I'd bought a metre of CDS tube which was duly sawn more or less in half ( I worked out there wasn't enough for three attempts).
It looked like a snug fit:

and so it was; this is the view from the chuck end of the spindle (or mandrel if you prefer):

Going back to the collet closer, there wasn't much of the collet thread protruding from the back of it...

and the closer is the same length as Boxford's own 3MT sleeve:

so rather than chop the closer down I opted to bore out the tail end to take the drawtube:

The guy who owned my house before me was one of those shotgun nutters and in the otherwise empty gun cabinet in a wardrobe he'd left a barrel brush, which is ideal for rodding yer lathe spindle free of debris

 

[Wedg1e]

Square up the end of the CDS tube...

and then work out how much of the wall to bore out to clear the collet core diameter:

As it was a simple boring job I'll spare you the details and make room for this bad boy

the 135/127 metric to imperial translation gear, which also meant digging this chart out:

Having altered the lathe gearing from this

to this

it was time to put the internal screwcutting tool to work. A wee tickle up the tube left enough of a helix to check with the thread gauge: definitely 20 tpi...

 

[Wedg1e]

I'm sure that if I looked hard enough I'd find the depth of thread for a 5C collet but winging it is what do most of, if not best, so a few passes of the tool were made (that's not a finger at left, it's the coolant nozzle!)...

until the collet started to screw in. It wouldn't quite go all the way on the first try (unlike a Darlington girl)...

but another shave and I was able to get it all the way in. And the collet, as well

All of which got me to here:

The tube was reversed in the chuck and clocked as true as I could get it, which was pretty close actually, that CDS is good stuff. However, I fancied working to a nice round number so it was turned down to 34mm (from about 34.9mm)...

and a runout groove added for the tool to clear into (turned out to be a bit shallow, that's winging it for you):

Having had mixed results over the years with brazed carbide and HSS threading tools I'd bought an indexable tool which had previously shown promise, although I think this was its first job:

As the lathe was already set up for 20tpi I thought I'd mix my measurements and cut an M34 x 20tpi - it was the sort of thing Harold Hall did in his books, so why not? Once it gets gloomy in the workshop I use an illuminated magnifier so I can see how badly the job is going:

Once I had what looked like a formed thread I called it a day; the handwheel thread would be made to suit anyway. State of play:

 

[Wedg1e]

Whilst casting about the place for stock from which to make a handwheel, I came across this offcut from a length of what I believe is some sort of bronze - it's a rough-cast cylinder with about 28mm bore and plenty of wall. I meant to PMI it at work but I'm not sure our machine is calibrated for much in the copper spectrum. Anyway, I thought it might be a better idea to use this for the threaded section and build an alloy wheel around it, rather than running an alloy wheel directly on the drawtube:

Working to the internationally-renowned M34 x 20tpi I opened it out with a boring bar

and then showed it some metallic lovin' with the threading tool

and after a few passes and the odd tickle (sounds like dating in the 1950s ) the drawtube screwed in...

As you can see, the thread on the tube isn't great, but it had a surprisingly nice feel with the nut, which came out all right, I thought:

For some reason that I've forgotten, I decided the nut didn't need to be all that long so I sliced the end off (if I remember, I'll PMI that offcut)

and ran the nut up and down the drawtube thread a few times, which smoothed things out a bit...

 

[Wedg1e]

I found some aluminium bar. This is 65mm...

and this 100mm diameter.

Obviously the 65mm is too small, but to carve a handwheel out of the 100mm would mean making a hell of a lot of swarf. The end of the lathe spindle is recessed 25mm into the changewheel guard, for a start. Ah well, it's got to be done. I turned on the bandsaw

About three minutes later...

Winging it as usual, I chucked the piece, and promptly centred it and ran a drill through. Then I gave myself a good because it didn't need that at all. It occurred to me that if I made it in two pieces, a 'hub' from the 65mm and a 'rim' from the 100mm, it would waste less material. So I ran a 38mm hole saw in from the freshly- (and unnecessarily-) drilled end and then parted off, to create the rim. The piece still in the chuck looks suspiciously like it would make a pulley

Then I switched to the 3-jaw and chucked a sawn-off length of the 65mm bar, then ran a hole saw through from each side...

The 65mm bar was then bored to take the bronze nut (which was stepped, largely from when I'd been experimenting with feeds and speeds, but the steps would help to seat it for thrust purposes (sounds plausible, anyway )...

Took a tap with a dead-blow mallet to get it in, but in it went:

I left the nut proud as it bears on the end of the lathe spindle and if it gets damaged it can be refaced without affecting the alloy hub.

 

[Wedg1e]

The 100mm 'rim' was then clocked in the 4-jaw and bored to take the 'hub', again as snug a fit as I could make it...

I considered TIG-welding the two together but if there's a sure-fire way for me to ruin a job it'll involve welding. Initially I just tidied-up the join between the two parts, but later I changed my mind and put a 5 degree taper on the whole face (not shown here)...

A quick test to see how it fit:

and how it looked on the drawtube...

Time for a change of machinery. Over to the Perrin with the dividing head; nothing too strenuous on the calculation front as I only wanted 6 holes in two sets at 120 degree spacing, conveniently the main gear has 12 holes at 30 degree spaces for quick setting with the locking pin. The hole circle plate is one I made earlier from a bit of 6mm alloy:

Holes were drilled...

and tapped M5...

and the parts locked together with stainless grubscrews. Then I chucked the assembly and added the 5 degree taper to the front face, rebored the centre hole to get rid of some turning marks and then recessed the rear of the wheel, again with a 5 degree taper.

The last task on this will be to knurl the rim: I only have a clamp-type knurl which won't open wide enough and anyway I feel that a straight knurl (which I don't have) might suit it better than a diamond pattern (plus the VSL's speed control dial is straight-knurled so there'd be some visual continuity). I've ordered a 'traditional' push-knurling tool with selectable 'coarseness' of the pattern, so that'll be a job for later in the week. I might also deepen the recess in the wheel, and shorten the drawtube by a few threads, but for now these are the parts:

 

[Wedg1e]

I ought to say that I did a quick test with the one 5C collet I have, the 6mm. The only stock I could find was either a bit of 1/4" brass which wouldn't fit, or a drill bit with a few marks on the shank, but it seemed to spin well enough.
I found that if I experimented by rotating the collet in the closer I could find a spot where the runout was confined to a flicker of the needle over the width of one scale mark! Worst case it was maybe a couple of tenths, but as the handwheel is too slippery to get much grip it could be that the lower figure will be repeatable once the collet gets pulled-in tightly. It might also have just been some muck on the closing taper...
I'll buy a collet at the upper end of the range (I think 28mm is as large as you can go in a 5C and this tube will pass that) and try some bigger stock.
Might also need to fit a key to the closer, as was mentioned further up the thread