Bizarrely, I found that 1 set would came with free P&P but if you increased the qty to 2 sets, the P&P would cost. WTF?? Go figure etc etc. So obviously I placed 2 separate orders - from 2 separate stores. Duh.
They took a fair while to arrive, as promised (free P&P, 20-40 days). And sure enough, they rougher than a bear's arse, albeit having been polished externally.
But first, I realised that although I have quite a few ER32 chucks with BT40 taper, I have none in ISO40 that will actually go on the machine. I'm going to struggle to try out the hoopy new collets without a suitable chuck. I've successfully converted these before - by TIG welding a threaded collar onto the end of the BT40 taper. Time to do a couple more.....
So first, turn up a couple of threaded extensions:
I've had a fine piece of 1" diameter mystery stainless steel for many years, since I won it in a scrapyard just outside York around 1977 - yes that's about 40 years ago. It's managed to survive intact since then, partly due to my reluctance to sully such a valuable piece of material. But seriously, if you don't use stuff, why bother keeping it?
The shoulder on an ISO40 toolholder is 25mm diameter and 25mm long, with an M16 coarse thread for the drawbar. So these extension collars are pretty simple to make:
- Turn the 1" stock down to (slightly under) 25mm.
- Drill through 9/16" (M16 tapping)
- Part off at 25mm long.
- Counterbore 16.5mm both ends (M16 clear)
- Chamfer inside and out, both ends.
- Thread M16 using a tap.
...then TIG weld onto the end of the BT40 toolholder.
Job done, so now see if it's any good. But first, these BT40 toolholders need to be modified slightly to clear the drive dogs. That's a 3/8" carbide cutter (in the manual mill) which had no problem skimming off the top of this hardened toolholder.
Checking runout of the modified toolholder:
That's pretty good - about 6-7 microns ie just over half a division on the scale. The Mitutoyo DTI only resolves 10um increments but you can interpolate (estimate). The Baty DTI agrees closely. It seems that the BT40 toolholder was a decent quality part and I haven't completely buggered it in the process of converting it to ISO40.
Now for the Chinesium collet:
Not so good but probably what we would have expected - over 50 microns total runout(!!).
Conclusion - these "collets" are only good for holding drills. No great surprise. It's just a pity they arrived after Xmas, otherwise they could have gone into Xmas crackers. At under £3 each, what do you expect?
Check out the new turning inserts:
Also this morning I received some CCET collets from APT Tools in Glasgow. I ordered them before Xmas but they were closed until yesterday.
Also this morning I received some CCET collets from APT Tools in Glasgow. I ordered them before Xmas but they were closed until yesterday.
These are CCET060202R-E UM25 ie right hand. The geometry is interesting, with a large-ish top rake and a straight, deep chip breaker. Given that it resembles the HSS geometry I have used very successfully in the past, I was hopeful that it would be better in my modest lathe than the default CCMT or CCGT inserts.
So first, some parameters. The insert box shows the parameters which translate into 1500rpm (for 25mm dia stock), 4 thou per rev and up to 1.5mm depth of cut.
First roughing cut - hardly a mirror finish:
But with a light cut, the finish improves:
This is the full 1.5mm cut:
Note the deep blue chips. They break up nicely into short lengths (20-30mm) but are hot enough to melt plastic and char wood. However, the work stayed touchable (ie < 50C) after roughing out as shown - most of the heat ends up in the chips.
By way of comparison, here's the same cut using a Korloy CCMT insert:
And a Korloy CCGT uncoated insert (actually intended for cutting aluminium but generally pretty good for medium and finishing in steel):
I'd say the CCET is an improvement over the CCMT for medium cuts and finishing (0.25mm min) but hardly a transformation.
That's it.
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