Sunday, 19 March 2023

Cam bodies - machining the square sockets

Unless I screw up badly, this should be the last operation on the cam bodies. I'm planning on machining sockets that are 10mm across flats ie will accept the same chuck keys used by the 3 and 4 jaw chucks. 

Looking at the (male) keys themselves, there's a half decent radius on the edges, so I can machine the cavities with a sensible sized end mill, namely a 3mm diameter. I'll also want to chamfer the edges of the sockets and the ODs of the bodies.

Rather than plunge / ramp a 3mm end mill into the steel, I'll start off with an 8mm hole, down to the final depth of 7mm. Then rough and finish the square cavity.

I have some nice 8mm carbide end mills that can plunge cut. So off we go:

And the clearing / finishing with 3mm end mill:

Good. That went well.

Finish with the chamfer:

Loos good.

And it even fits.

Nice surface finish.

All done.

The chuck key doesn't sit as far in as on the std part but I haven't much meat left over for the retainer screw. It's possible I could have located the groove further inboard but here we are. A 7mm socket should be more than adequate surely.

So now I need to give them a bit of a polish, harden and temper them, then remove any oxidisation. Then I can move on to finishing off the main body and doing the final finish machining with it it in place on the spindle nose.

Sunday, 12 March 2023

Making the cams - PtII (eccentric machining and final features)

Bollocks (again). I let The Stupid Fat Bloke continue with the 2nd and 3rd cams, so you can guess what happened. On this occasion, he got the 2nd one done then let his success go to his head. The result is that the 3rd part ended up with a 1mm wide shoulder instead of a 3mm wide one. And given that that shoulder takes a fair bit of the thrust load, it's a scrapper.

So let's make another. I should have made up 4 from the outset really. Here's the stock, turned down to diameter and length. As before, use The Shiz to place a centre drill hole, offset 0.8mm to give the required eccentricity:

Then set it up in the 4-jaw, ready to turn the eccentric portion:

Sorted. You can see the one TSFB screwed up, second from the left.

Now to create the cylindrical feature using a boring bar. I need this to be 15mm diameter, so I'll drill some 12mm holes and set the tool to exactly 15mm before moving over to the cam bodies in anger.

Pretty close, given The function this feature supports:

I need to have some form of angular reference so that I can position the features consistently. They will be at 45 and 90 degrees to this reference bore, which is in turn 15 degrees from the point of maximum eccentricity.

I think I'm ready to machine the cylindrical faces:

Some careful setting up with the Renishaw probe and here we are:

Using some ground parallels and a vise stop allows me to place the other parts subsequently.

And there we have them.

Now I need to turn them 45 degrees so I can machine a flat. Here's my solution, using a pin in the reference bore and this digital angle gauge:

And finally, the flats are done. Looking good.

That's most of the main operations done now. It remains for me to machine the female square drive hole. I'm going to make this 8mm across flats, using a 3mm end mill. But that's for next time. I'd better not let TSFB fuck this up, as I have no spares.....

Sunday, 12 February 2023

Making the cams - Pt1

The cams need to be hardened, so the EN9T I bought recently should do the trick. This is like 1045 carbon steel ie can be hardened and tempered without any exotic processes being required.

I need a 19mm diameter but naturally I bought 20mm so I'll need to turn it down and this stuff isn't the nicest material to machine.

I just need to turn it down to 19mm, create a 3mm width groove, chamfer the edges and part it off.

There you go. Some deburring will be required before it will slide into the bore. Otherwise they came out nicely.

Now I need to machine the eccentric cam. The eccentricity is 0.8mm. How to machine this? There won't be much stickout on the lathe, so I'll drill a centre hole in The Shiz and bring up the tailstock.

I can find the centre using the Renishaw probe, then move the table to create the 0.8mm offset and then drill the centre hole.

Like this:

To set the blank up in the 4-jaw with the centre hole on axis, the simplest method is to use a centre and DTI. Once the runout is dialled out, the part is on centre.

The Tree has a hydraulic tailstock. You can set the preload using a adjustable pressure regulator in the valve block. The existing setting seems to work OK without driving the blank into the chuck!

It's going to be a bit tight in there....

Nearly there. Just need to clean up the shoulder with a parting / grooving tool.

That worked out OK. The final measurements are spot on.

I'm now out of time today but here's the second part set up and ready to machine.

Friday, 10 February 2023

Bollocks. Stupidly, I let The Stupid Fat Bloke set up the part in The Shiz and program the drilling / boring operations using dimensions from the 2D Drawing. 

Nice work, Fat Boy. But before you drill those radial holes, any blind idiot can see that the camlock stud bores are in the wrong place, by exactly 60 degrees. Apart from the fact it doesn't look like the 2D drawing, it's obvious that the fixing holes would clash with any radial cam bores. Dickhead.

But all is not yet lost, thankfully. The answer is to create another 3 holes for the cam studs, resulting in a total of 6. Three of them will stand as testament to the power of idiocy. These won't be so obvious when the chuck is fitted but the only alternative would be to start again and make another body from stock. Seems the path of least waste that my laziness will appreciate.

So firstly I will carry out the radial drilling / boring operation in the 4th axis, before replacing the thing in the vise and drilling / boring the additional 3 axial holes.

Initial step will be to (carefully) set up the work for the 3 radial bores. Luckily I'd set up the 4th axis during the last session, so apart from double checking, there's not a lot of actual, setup to do.

Off we go. However, I soon determined that my scepticism about the Indian 3-jaw chuck having enough grip to withstand the drilling forces required to force a 12mm drill through were justified. Never mind - this block of loominum can hold it in place against the jaws.

Nice finish from the boring bar.

Needs to plunge about 43mm which still leaves about 10-15mm clearanc.

Now back to the horizontal setup. How to align the holes? Actually, the Centroid software allows you to use CSR ("coordinate system rotation") to reorientate the machine axes to a measured direction that is picked up by to probed points. In this case, I've got  couple of tight fitting 12mm end mills and a straight edge. The Y axis will then be aligned to these 2 holes that are intended to be on the same Y coordinate.

With that done and some sanity check probing on the existing hole positions, I can get drilling and boring again.

That's the 12mm holes drilled.

...and bored

But - does it fit? Yes:

The cam studs are visible in the radial bores. They look about right.

Looks pretty good, if you ignore the 3 idiot holes:

Cool - I should be happy with that. Next I need to focus on the cam studs...

Cam bodies - machining the square sockets

Unless I screw up badly, this should be the last operation on the cam bodies. I'm planning on machining sockets that are 10mm across fla...