Another new project... a QCTP (Quick Change Toolpost)

Gallery, Projects and General > Project Logs

<< < (9/18) > >>

AdeV:
Cheers Rob - much appreciated... I need encouragement after today... it was one of those "2 steps forward, 1 step back" days in the workshop :(

First job was to enlarge the first piston hole to be the same size as the other one (1.400" square). This went OK-ish... oddly, the same setup as I used yesterday (6mm roughing cutter, followed by 1/4" end mill) didn't work; the roughing cutter over-cut. I've no idea why, the only possible explanation I can think of is; the 1/4" collet I was using yesterday has stripped its threads, so I was using a different collet. Maybe the old one had some runout or something. Anyway, the result is, the 1/4" end mill didn't do anything useful to the finish, so I'll have to be a bit careful with that piston.

Anyway, on with the show... I've been pondering for some time how I would retain the pistons within the body of the QCTP. The only solution I've seen is a fellow madmodder's (sorry, I forget who) idea of drilling up through the base & screwing in a pin which sticks into the body of the piston, thus retaining it. Whilst I can see how that works, It doesn't seem very elegant to me. So, I figured I wanted something a bit neater. Then.... inspiration! I have a "Quillmaster" for my Bridgeport, which allows me to mill inside of things. So, a bit of fiddling later (including shortening a 3/16" end mill so the whole kaboodle will fit inside the main bore):

And then, having lined everything up & dialled it in using the "bump" method (bump the cutter into the work, call that near as damnit 0.000" + 1/2 cutter width), and got ready to take the first cut.... a thought occurred. Anyone who knows me will probably slap their forehead & groan at this point, because it's bound to get more complicated... Today is no exception :D

I decided that, this would make a very ugly flange. It would be nearly 1/2" deep at the edges, yet only a few thou at the centre. This offends my sense of symmetry - the flange should be the same thickness all the way around. And.... it can be! All I need to do is mount the block on my dividing head, and I can cut the flange on a curve! The only problem is, the dividing head has a fairly small 3-jaw chuck on it, and I really don't want to disturb it. The chuck is too small to grip the outside edges of the block (and besides, they'd be off-centre), and is too big to grab the inside edges of the small hole in the bottom; and I can't use the big hole 'cos I need that to get the Quillmaster in....

....so I spent the rest of the evening making a mandrel to hold the body in the dividing head.... After much cursing and one (luckily minor) toolcrash:

I don't have a decent 60o threading tool, so rather than try to cut a threaded stub, instead I drilled it with a handy 0.435" drill & tapped it 1/2" UNC - to match my milling machine mounting kit. The threaded stub is the shortest stud in my kit, screwed in as far as I could get it. The flange bolt also comes with the kit. When it's all put together:

It then sits nicely in the dividing head:

The only issue - visible in the 2nd photo - is that line about 1/2 way down the main diameter. After the tool crash (more of a hard tool bump really), the mandrel was knocked slightly off-centre. After some colourful cursing, I re-dialed it in as best I could, but I couldn't quite get it exactly bob on. So, after finishing the 1" bore (which goes into the QCTP body), I took just enough thousandths to ensure the mandrel would run true in the dividing head. Unfortunately, I couldn't reach the last inch or so, due to the chuck, and guess what - yep, the dividing head jaws are deep enough to grip on the slightly off-centre (larger) diameter. Agh! I'll have to pop it back in the lathe & take another cut to narrow the back diameter just enough that the trued diameter is being gripped. THEN I can use the Quillmaster!

Finally, the answer to the oil question... Dave is remarkably close, really...

Firstly, one cannot just pour oil into the funnel. If you go too slow, the oil all dribbles down the big barrel, and you're there forever.
If you go quick enough not to spill oil down the barrel, then the funnel fills up & tips over, dumping at least a pint of oil on the floor. Don't ask
me how I know this. Similarly, finding a corner is no good, as the funnel will ALWAYS tip out of the corner, even if that seems to be physically
impossible. Lastly, even if you find a way to support the top of the funnel, as long as it's resting on the oil can, it will form a perfect seal
which prevents the funnel from draining in anything less than 3 weeks. Again, don't ask me how I know this.

So, I had a chat with Heath Robinson, and he suggested this:

Funnel is held in an old brake disc, supported between the Comedy Bandsaw and the Bin of Paper Towel Death. The oil can is sitting on a can of old paint,
another project in the making, and finally my ER32 collet set, to bring it up to the perfect height. I can now fill the oil can in just a few seconds, with
as good as no spillage whatsoever, result!!!

Naturally, the very next day, the brake disc fell off its perch, scattering everything far & wide as it fell.... Ho hum, such is life...

Baldrocker:
Hi Adev
I only have a Falcon left front disc brake, will that fit? (Don't be rude)
BR

AdeV:
:bang:

Damn Quillmaster wouldn't go far enough into the bore before it hit the thread in the arbor; so I would only be able to cut the flange 1/2 way down the sides of the piston - no good! So, I spent a good hour pondering, turning down a nut to 1/2 it's original depth, cutting a shorter piece of threaded stud, and modifying a large washer (needed a bigger hole), the end result of which is...... I got within 3/16ths (the cutter width, approx) of being able to cut the flange on the bottom edge, but no further! Aaargh!

Faced with the prospect of trying to lose another 3/16" off the nut/washer combo (impractical, I fear, there won't be enough nut left to grip properly), I decided enough was enough. So, I did a bunch of draw filing, which is surprisingly hard work - unless I'm doing it wrong, and have now called it a night.

I may yet give up on the Quillmaster & flange route; Instead, I'm thinking of making the piston holes (and the pistons themselves, obviously) tapered, so they'll go in the holes from the inside, but can't pass all the way through. The other option is to find another way to clamp the block onto the dividing head...

Hmmm.... :scratch:

Rob.Wilson:
Ade

I now have tool envy ::) cool bit of kit you av there (quill master) :dremel:

Rob

AdeV:
Rob - I got it at quite a reasonable price (I thought) too - only £85 (they seem to go for £150+ on ePay); however, so far all its done is take up space in a cupboard... it's gone back away now, 'cos I'm going to part-taper the pistons instead, MUCH easier than tring to make the quillmaster work. Ah well, I'm sure it'll earn its keep one day, even if it's on eBay...

Only a bit of machine time tonight; I put the block back in the lathe to cut the underside recess (the toolpost will ride on a base, this will allow it to rotate without falling off & causing the baby jesus to cry). The base is a separate section of 1/2" plate which also needs some work...

So, anyway, here it is: Misuse of a boring bar #1 (but hey, it's currently the best facing/turning/cutting tool I have...):

Gotta love power feed :dremel:

Then, as the lathe seem to be cutting particularly well tonight, I took the skimmiest of skim cuts off the bottom, partly to get it dead nuts flat relative to the top (I'm not convinced it matters, but what the heck), but mainly to make an impression on those machine marks that the mill left:

I took about 0.006" off in total, in 3 passes (yawn).

Then, over to the filing bench, I spent the next 2 hours draw filing various sides. Even that didn't get rid of ALL of the machine marks, but I'm hoping the metal blacking will cover a lot of sins...

More tomorrow :wave:

Navigation

 Message Index

Go to full version