Eine Dampfpumpe or a steam pump

[Sanjay F]

Time to stop before any mistakes are made!

The long holes vertically and horizontally have been made and now opening them up to the correct depth. I'm using cutting oil and running about 500 rpm, but its very 'grabby' so lots of stopping, cleaning out swarf and proceeding with caution. Any advice on making it less 'grabby'

[Jasonb]

Lock the quill and lower the head so the matal can't pull the drill down as easily.

I would usually say don't pilot drill just go in at finished size but as many of those holes are counter bored you can't do that so easily.

Some people stone the edge of the drill to reduce the rake but it is not something I do.

[Sanjay F]

The drill bit you see in the photo is 5mm, the next counterbore needs to be 8mm; I'm not feeling confident about going straight in with 8mm; do you think I should increase the drill bit size incrementally, and if so, how much should I go up by each time?

The drawing shows the red arrowed surfaces to be flat, do they need to be milled or drilled? I've drilled to the bottom interface between the 3mm to 5mm hole, I hope that's ok, I have very limited metric end mills if they need milling?

[Jasonb]

If a ball sits on the surfaces which it looks like it does then the edges need to be good and true, first 5mm hole would be reamed then a D bit or boring used to enlarge the holes and give a good machined seat.

Due to the depth you could go most of the way with a drill and then just finish off with a D bit to flatten the bottom or bore the whole way.

[Sanjay F]

I have the following end mills (luckily) -

- 8mm which should fine for the top interface as its only 12mm deep, 
- 5mm 2 flute and a 5mm 4 flute - I'm concerned by the shank on the 2-flute as it may not reach

I think given the 4 flute looks better lengthwise, I'll drill then finally bore, to flatten. Given I've already drill one of the 5mm holes to 35mm (on drawing), what depth should I flatten to ..... would another 1.5mm to 36.5mm be okay or would impact the operation?

[Jasonb]

Provided you don't break into the hole at the bottom depth is not too critical.

[Sanjay F]

Nearly a disaster the workpiece jumped in the vice as you can see from the first picture; its an awkward piece to clamp and I should have listened to my doubts in the beginning and not ignored them 

Now I have it clamped on this pallet with 4 clamps the whole thing is much more solid. I'm finding it easier to drill to nearly the required depth and then milling the last couple of mm.

Lot's holes to be made in this one ..........

[Dave Otto]

Glad that you averted the disaster, when you were talking about having to go down into a previously drilled hole to open it up, I was thinking to my self, man that drill bit could rip that casting right out of the vise in an instant. Maybe I should have said something?
Like Jason I have never been one to stone the cutting edges of drills for brass and bronze, but I have used some this way and it does work.

Dave

[Sanjay F]

It's okay Dave, it wasn't terminal

Shame it was at the end of the day when I had the idea, but I made this little jig to hold the workpiece which would have saved a lot of pain and nervousness whilst machining - better late than never I guess, especially as the next operation is drill/bore a 10mm shaft vertically down through the centre section. (see red arrow)

It might be worth making another Ali block for the otherside too in order to make it ultra rigid......yes, I'll do that, I'll only regret it if it goes wrong! 

[crueby]

Can never have too many clamps. Clamp blocks. Jigs...  Sometimes we actually remember in time to use them!  Been there, done that...
 

[Sanjay F]

Question

When stoning drill bits does that mean to make them more or less pointy (technically speaking?). I don't want to wreck my good drill bits but have some sacrificial ones I could use....

[Dave Otto]

Here is a short video from Click Spring that will give you an idea of what you want to do.
<a href="https://www.youtube.com/watch?v=pAngKHIZgyA" target="_blank">http://www.youtube.com/watch?v=pAngKHIZgyA</a>

Dave

[Sanjay F]

Brilliant, short, simple and to the point (forgive the pun!  ). I have a spare set of bits which go up in 0.5mm increments and I think I'll make them into the 'brass drill bit set' as suggested in the video

[Chipswitheverything]

Good thinking on the various extra precautions of both tooling geometry and the holding when approaching the machining of an intricate and expensive little casting like this one.
Unless a component has decent areas of reliably flat surface, like working from cleaned up bar stock ( burrs and muck removed ), or making a part on the end of parent stock of that sort,  I tend to be wary of hoping that clamping up in the machine vice on a mixed bag of small contact areas will be proof against some disaster , especially with non ferrous. Occasionally I end up with an awkward forest of clamps and packing on something, and it looks like overdoing it, but getting the procedure done without an OMG moment is the main thing!  Dave

[Sanjay F]

I've been discussing the distance in the red arrow with Michael as it is the only measurement so far which has not been to scale. 46mm would mean the 10mm diameter hole would go into the vertical column according to the drawing.

After 'stoning' a 4mm drill bit I have made the initial hole all the way so its breaks through, then by measuring that using the method below determined the breakthrough distance is 47.18mm. My question is, is the 46mm critical as that seems VERY close to 47.18 mm, should I just making in 44 or 45mm to give a margin?