Author Topic: How do you machine these?  (Read 898 times)

Offline Moxis

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How do you machine these?
« on: September 18, 2018, 07:01:24 AM »
For my Marcher build I have to make several flanges, valve rod glands etc. according to attached picture. But how do you guys machine them? I am sure there is a nice fixture or a trick available to make them, but how?

Offline Jasonb

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Re: How do you machine these?
« Reply #1 on: September 18, 2018, 07:08:45 AM »
Well you can file them to shape for one.

Or as they are tangental lines linking a large central diameter to smaller diameters at the end I use a rotary table for the straight parts, central arc and then file the ends using buttons. Take a look part way down this post

http://www.modelenginemaker.com/index.php/topic,4438.msg89333.html#msg89333

There are a coulple of other methods if you want a more oval looking gland which either use a boring head or a jig in the lathe which works out fastest if there are several the same size.


Offline Jo

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Re: How do you machine these?
« Reply #2 on: September 18, 2018, 07:47:38 AM »
Hi Moxis,

You need to start with the flat faces. Yep they are a bit thin and the flange looks impossible to hold and machine without causing damage - it is difficult so we are not going to use it  ;)

Give the casting a fettle get rid of any lumps on the front and back faces. Give the gasket face a rub on a bit of abrasive paper to get the surface reasonably flat. Measure - check you can get the flange thickness out of it and where the excess metal is. Decide how much you can take off the back and how much you can take off the front.

Find a bit of scrap bigger than the front flange and put it in the chuck and face it. Using either a drill chuck (or in this case I used an ER 32 chuck as the flange was too small to grip) hold the casting by the boss in the tailstock and super glue it to the scrap in the chuck. Let the super glue set then turn the flat, the boss and drill the centre.

Turn it over and hold by the boss. You options are to use a collet chuck like a 5C which can hold short bits or to make a pot chuck which is a tight fit on the boss. In the worst case you could just counter bore the bit of scrap for a good fit on the boss and then superglue on again to face the back  ::) )

Now you need to find where the mounting holes are to go. I hold the casting by the flange in a collet chuck that I have centred and drill the holes. In the old days people would make a drilling jig that slipped over the boss and guided the drill to where the two holes need to be drilled - just make sure you find the centre line that gives you maximum area for where the nuts are going to go.  I would check the nut/boss spacing first as you can see from these flanges there was no space for the nuts to rotate and I was forced to use smaller studs/nuts  :disappointed:

As Jason said the easiest way to shape the outside is using filing buttons  ;)

Jo
Usus est optimum magister

Offline Jasonb

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Re: How do you machine these?
« Reply #3 on: September 18, 2018, 07:58:51 AM »
Jo, they are not supplied as castings in the Marcher kit, as the drawing says just machine from GM or brass stock.

So just turn the spigot, drill and CSK in the lathe, then over to the mill and rotary table hold vertically to shape before back to the lathe to parting off.

Offline Jo

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Re: How do you machine these?
« Reply #4 on: September 18, 2018, 08:21:25 AM »
Jo, they are not supplied as castings in the Marcher kit, as the drawing says just machine from GM or brass stock.

They are in my kit  ::)

Jo
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Offline Jasonb

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Re: How do you machine these?
« Reply #5 on: September 18, 2018, 11:30:52 AM »

Offline Moxis

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Re: How do you machine these?
« Reply #6 on: September 18, 2018, 02:41:03 PM »
Well you can file them to shape for one.

Or as they are tangental lines linking a large central diameter to smaller diameters at the end I use a rotary table for the straight parts, central arc and then file the ends using buttons. Take a look part way down this post

http://www.modelenginemaker.com/index.php/topic,4438.msg89333.html#msg89333

I think that's the way I am going to try making them. Thanks a lot Jason and also others who have replied to my question. Very nice people here indeed!