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Valve Base

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sbwhart:
Hi Darren

Another way to open the hole out would be to mount it on a face plate up against a sacrifical plate and just bore it out, the technique has been shown elsware on MODMODDER I think it was Bernd who posted it, but I stand to be corrected on this.

Have Fun
 :wave:
Stew

Bernd:
Darren,

Yes, that is what I was thinking about. I said for cutting wood because it would give an idea of approximatley what I was suggesting. Bog's has elaborated further on this.

Stew has another idea which I think would work if it is possible to mount the plate on a faceplate. Yes Stew I believe I've mentioned that some were on Madmodder.

The last thing I would resort to is the chain drilling method. Punch out the center part, file the sharp edges and then if you have a mill, use a boring tool to bore to size. Ofcourse if you have many parts to do then this would be a pain in the you know were. :)

Just some different ways to get the job done. I guess it will depend on what tooling you have at your disposal.

Bernd

Rog02:
The trepanning tool Bog shows is basically the same as I use to cut inspection holes in aircraft panels.  I think mine is a General Tool which is a pretty decent quality tool and if I remember correctly I think it set me back about $15 USD.  I turn it either by a cordless drill or with an old fashioned wood brace and as others have stated, it requires a steady hand when free handing a hole.  I also have used it to cut instrument holes in a panel blank that could be placed in a drill press.  That works much easier!  Turn the tool slow and have the material well clamped as the cutter can and will try to dig in.  A slow feed is required with enough back force to prevent the digging in.

A Google search turned up a lot of high dollar versions for mills, but for the infrequent use this tool will normally see those are way overkill.

The other alternative, if you have a boring head for your mill, would be to make an offset bit for that and use it to cut the hole. 

Darren:
Thanks for the tips guys, after reading all the suggestions I had a dig around of what I had that may do the job. But first a picture to show some scale of the project.
As you can see, mounting on the faceplate may have been a tad difficult in this case.



So digging out some candidate tooling from the lathe I gathered these. They are turret tooling for the Smart and Brown lathe.
The two outer ones didn't have enough adjustment to go to 60mm. But the center one though not having fine adjustment looked promising.



I am of course holding the tool bit in the wrong direction for lathe work, but should work as a trepanning tool on the mill. My only reservation was the fact that the tool bit was only held with one screw. However, this proved more than adequate when it can down to it.



You can see that I have marked the work out by drawing up in CAD and then printing onto an A4 sheet. held to the work with sticky tape. If you have several identical pieces to do this can save a lot of work in marking out time. For me, well it's just more accurate, center punch through the paper as normal.

Just beginning to take a cut, working ok but I decided that the tool tip was a bit too wide, so reground it to a point. You can see that I have a 45 deg chamfer on the tool. My thinking was that if the cut came out a little rough I would always lower the quill to tidy up the finish by increasing the size of the hole. Again this worked quite well.



The result, quite tidy I'd say, took minimal cleaning up and didn't burn the painted finish at all.



Then to drill the two valve base mounting holes with a 19mm hole saw. This was easy of course.



Transformer now the right way up and in position, Lovely jubley !!!




The trapanning was done at the slowest speed of my mill. Cutting proved to be stable if a little on the slow side.
(112rpm digitally tested with my new "cheap" tool from the far east. I had no idea what speeds my mill was giving me and the belt positions were very confusing to say the least)

bogstandard:
Nice one Darren,

A clear case of making do with what you already have.

Using dedicated machine tooling for use to do other things is a method I use.

I remember a couple of years ago, when ball turners started to become popular. I hacked together a fixture that used the boring head off my mill to do the job about 10 to 15 years ago, with very good results.

Use what you have got and keep the pennies in your pocket.

John

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