Tools, to make tools...

[AdeV]

Recently, I bought a shiny new set of Chinesium gear cutters, to make the back gears for my Boxford. They sat, lonelyly, in their box for a while, as I didn't have a suitable holder for them... So, time to rectify that!

I bought a lump of 50mm AF mild steel hex bar. Hacked it to length in the hacksaw, then drilled/bored out a recess in the back. My thinking was, if I get the nut all the way in, it'll stand on its back face too. As it happens, that didn't work out, although there's no reason it couldn't in the future. (pic 1)


After that, I turned it around and drilled it 1/2" all the way through (convinced that my drawbar was 1/2" UNF.... not the 7/16" UNF it actually is! Hey ho, it's not a problem this time). Then bored all but around 1/4" to the R8 shank size + a few thou clearance. 

The R8 blank arbor I bought from the lovely chaps at RDG Tools had a suitable flat face on it, so pinning it in the hole with a live centre allowed me to set up the compound slide to the exact taper - lots of swearing at that job I can tell you, but I got there in the end & bored out enough of a taper that maybe 2mm of the collet ends up sticking out of the nose when it's tightened up.

Penultimate job - turn, thread, and cut the hex end into a custom nut, which pulls the collet tight. Finally; turn the end of an M6 bolt down until it fits in the slot of my most recalcitrant collet, drill & tap a suitable hole in the collet block, apply screw, and tada!

(pics 2-5).

It worked out very well, and can be dialled in on the 3-jaw to around 0.002 TIR, given a big enough hammer 

[AdeV]

So... having made the collet block (because for some reason no-one makes a commercial one?), now I could turn my attentions to the arbor. This was pretty straightforward really: Turn part of the soft nose down to the 22mm bore my gear cutters have. Sneak up on final dimension, until we get a nice sliding fit - it's actually a smidgeon undersize, which is annoying, but I can live with it. Then drill & tap the end for an M10 bolt.

Final job, take a perfectly good piece of bar, and cut a 22mm recess into it, sufficiently deep that it just grips the gear cutter before bottoming out. Drill 10mm clearance hole for the bolt, heavily chamfered so the bolt sits flat on the backside. Fit, and sneak down to a more sensible diameter 0.010" at a time. I settled on 28.60mm, for no apparent reason.

There's one more job to do with it - the gear cutters have a keyway, so they don't spin on the arbor. Since I'm fairly sure I can't be bothered milling a key slot, then trying to make a key the exact right size... I think I'm going to cheat like hell: Make an aluminium ring to take the place of the gear cutter, mill a slot into that the right size for the gear key, then mig-weld through it into the steel. If I'm quick enough, I should be able to get a decent enough key in it before the aluminium melts... Put it back in the collet block to mill any rough scabs off the key, and we're done.

Until next week...

PS: I forgot to mention, that screw sticking out of the collet block.... I do intend to cut that off flush, maybe add a screwdriver slot, then Loctite it in. I just can't quite lay my hands on my bottle of Loctite right now...... more on that subject soon too.

[AdeV]

PPS: The reason the collet block won't stand face up when there's a collet in it.... can be seen in the picture 

Basically, the recess is too shallow, the washer too thick and the nut too tall... On the plus side, it means you can tighten it with a spanner, when a socket would have done.

Also, I must have got the taper fairly close, because it needs a good thwack with a blunt object to release the collet, if it's been snugged down nice and murder tight... 

[vintageandclassicrepairs]

Hi Adev,
Nice work
A maybe easier way to add a key would be to drill and tap a hole to suit a suitably sized grubscrew?
That said I made a slitting saw arbor and didnt bother with a key just relying on the clamped faces
Works for me
John

[chipenter]

Try it without the key first you can put a key in later if the cutter slips , and its a safety measure .

[PekkaNF]

OK, I have rad this twice and come to conclusion that this is actually two only loselely related tools:

1) Hex R8 block because you can! Ok, you might use it to tighten saw/gear cutter into arbor, but sounds splendidly elaborate for that only, when simple flats on the arbor would have done nicely....therefore I think that you have other plans for this - as the collet manequin hints.

2) Key for the gear cutter....can't really tell if it needs one. I have milled several keyways with four flute carbide mills - looks accessible. Even though many people absolutely hate woodruff key, that looks like ideal canditate for it.

3) Key for the HEX-block....think that dog end set screw should do nicely here. Generally it is really bad substitute for a key when real key needed, but here maybe forces are not that great? I actually don't know because I don't use R8, that taper is nearly self releasing, maybe it does not need much extra help?

I have been reluctant to contribute, because I am not sure if this is any contribution - but I am curious and this is interesting thread.

[AdeV]

Well.... I did think that an R8 collet block might come in useful in the future; but beyond machining this specific fixture, I had no actual planned purpose for it. On the other hand, it was a "nice to make" and pretty simple, other than setting the taper (which wasn't as difficult as I'd expected). As it happens, I could have probably just held the collet in the 3-jaw chuck, and taken light cuts. But why do it the simple way, when there's a more complicated one available? Also it forced me to finally dig out another toolholder blank for my QCTP - getting fed up of swapping tools between them, that is NOT how they're supposed to work!

Anyway - why hex: Why not? Other than round aluminium, I didn't have any suitable material in stock, and hex has the advantage it can be held in a vice or a 3-jaw chuck pretty easily. Beyond that, no, I can't think of an real use for it just now... but if anyone wants to borrow it, they're quite welcome

So - key for the cutter: I'm also not sure (now...). I was only sure before because there was a cut out for it. But I guess that's more for a horizontal mill, which might not tightly face-clamp the cutter. So for sure, I'll just go with clamping forces first, and add a key if it's a problem.

Finally, the key for the hex block; is just there to prevent the collet from rotating with the bolt when you're tightening it up. Once the taper has a grip, it's doing all the work anyway. For some reason, the slot on my 1/2" collet is shallower and narrower than all the rest of them - but it works just fine in the mill, so it must be man enough for the intended task.

[PekkaNF]

I have ER32 square and hex blocks. Really usefull on very many things, specially on the milling machine: Set material end stop or jaw stop to define x-axis location and then you can index 90 or 60/120 degrees in vise and 90 degrees to them with V-block/clamps. Also very useful when in vise AND angle block.

And very good idea to make something to learn new things.

[kayzed1]

Just spotted this AdeV. I have an R8 X 1" if you need to borrow it..
Lyn.