A machining question.

andrewnummelin
Posts: 238
Joined: Mon Jul 21, 2008 9:43 am

A machining question.

Postby andrewnummelin » Fri Jun 12, 2020 8:25 pm

I was wondering if anyone could suggest a good method of making the part shown in "C" (with fittings) and "D" (plain) below: the side elevation is in "B", "C" and "D" are views from underneath.
Capture.JPG

My initial thoughts are milling (but I'm not sure what cutter could do the seating for the domed washer) or taking up a different hobby!
Regards,

Andrew Nummelin

davebradwell
Posts: 272
Joined: Fri Jan 18, 2019 3:48 pm

Re: A machining question.

Postby davebradwell » Fri Jun 12, 2020 8:48 pm

The seatings for the domed washers are the easy bit - ball ended cutters are available. As to machining something around 0.8 wide, that's clever stuff and the shape suggests cnc or several operations. Take heart that I'm not a qualified machinist so this is just a passing view.

Actually, domed washers sit happily in conical seatings.

In working out how to make it, some idea of required accuracy is usually important.

DaveB

davebradwell
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Joined: Fri Jan 18, 2019 3:48 pm

Re: A machining question.

Postby davebradwell » Sat Jun 13, 2020 8:57 am

Getting closer to my ex day job, I'd ask if the bosses need to be circular and how many you want? What material? Can the top piece A be made thicker so that the seatings can be machined into it and saving 2 fiddly little bushes and an assembly job? I fear that after machining part D it could take a while to straighten it out again. How about a casting but that gives different problems?

It might be easier to use balls, if acceptable, which can be drilled in a collet, than make tiny domed washers, unless these are a proprietary part. (Pushing my luck with the punctuation there).

DaveB

Jeremy Suter
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Joined: Tue Apr 14, 2009 6:56 pm

Re: A machining question.

Postby Jeremy Suter » Sat Jun 13, 2020 12:51 pm

Well that is a challenge.

What is it. What do you want it machining in, and how many do you need.


It might be possible on my pantograph milling machine, it can certainly cut that shape, but the thickness of material is against it. Machining it in Brass or Nickle Silver even going about 5 thou at each cut. It would take quite a while to cut that thickness, and you could still suffer with heat distortion along that narrow middle section.
The holes would be put in before cutting the sides and drilled to the correct size later, To get the taper and cup shape paddle drills could be shaped to what is needed.

It might be easier to do them in thinner material and laminate them or cut them slightly thicker and file them down or even to cut one side correctly then make a jig for it to sit in before machining the other side in the vertical milling machine.

nigelcliffe
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Joined: Mon Jul 21, 2008 8:31 am

Re: A machining question.

Postby nigelcliffe » Sat Jun 13, 2020 3:53 pm

I'd be tempted with "etch it" for the long sections - possibly more than one layer - then turn cylindrical parts to fit through the etch at each end, and join the whole lot together with solder of whatever temperature you can get away with.

Terry Bendall
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Joined: Sun Jul 27, 2008 7:46 am

Re: A machining question.

Postby Terry Bendall » Sun Jun 14, 2020 9:35 am

My question would be what is it for and why does it have to be that shape?

Terry Bendall

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Mike Garwood
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Joined: Sun Aug 03, 2008 4:51 pm

Re: A machining question.

Postby Mike Garwood » Sun Jun 14, 2020 10:14 am

What’s wrong with printing it (3D) ?

Mike

nigelcliffe
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Joined: Mon Jul 21, 2008 8:31 am

Re: A machining question.

Postby nigelcliffe » Sun Jun 14, 2020 11:02 am

Mike Garwood wrote:What’s wrong with printing it (3D) ?


I've experience in printing metal centres for loco wheels in stainless. Its accurate, but not perfect, and any holes will need cleaning out.
If only needing one or two, and putting them on a single sprue it may be cost effective at about £30-£40.

andrewnummelin
Posts: 238
Joined: Mon Jul 21, 2008 9:43 am

Re: A machining question.

Postby andrewnummelin » Sun Jun 14, 2020 11:38 am

Gents,

Thanks for the advice and questions that have made me think...

Accuracy needed? Visually irrelevant, good enough to work - I've no idea what that means numerically!

Number needed? Three (so six suspension links), so no need to think of "mass production" unless the carpet god gets very greedy.

Material? Metal because the project is essentially metal working; but I'm not insisting on iron & steel!

Milling or lamination (with inserts)? I'd also wondered - probably I'll try milling (and will probably have to make a supporting jig) first. Lamination would push me towards etching that I would like to avoid for this project.

3D printing? Intriguing: would a metal insert seat be needed or would the moulding be OK on its own. Presumably it would have to be a cured resin print because of the size. I've often wondered about getting a resin printer - I wonder when supplies will return to normal after the pandemic.

What's it for? Practice for a loco I'd like to build (GWR 1350 0-4-4ST, ex MRCC 49) starting with a lockdown challenge https://www.scalefour.org/forum/viewtopic.php?f=89&t=6843#p73958 .
Regards,

Andrew Nummelin

nigelcliffe
Posts: 556
Joined: Mon Jul 21, 2008 8:31 am

Re: A machining question.

Postby nigelcliffe » Sun Jun 14, 2020 5:14 pm

3D printing - I'd assumed we were talking about printing in metal. Which I've done (now running at many hundred parts), sending a CAD file to Materialize in Belgium. Their "high detail stainless" could produce the parts, but any shafts/running surfaces would need additional work, and the printed stainless is very hard and eats drill bits fairly quickly.

Example 2mm scale, 10mm diameter driving wheel, steel tyre, steel axle, 3D printed centre. Yours for £12.50/pair at the 2mm shop...
http://www.2mm.org.uk/products/images/s3-009.jpg

- Nigel


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