Machining Techniques

Machining Techniques

Postby Bernd » Fri Apr 28, 2017 7:41 am

Brain,

Let's use this thread for discussing machining questions. I've copied your questions here and will try to answer them as best to my knowledge as I can.

1 - Often, I create rivets (Sherline CNC, too) by:
a) drilling rivet-pattern holes in a plastic sheet underlayment
b) fixing the model/pattern material to the plastic with 3M #665 double-sided tape
c) drilling holes in the pattern material within a few thousandths of cutting all the way through
d) with the spindle off, press a probe into the hole so that the impression is formed in the underlayment holes


This sounds like an interesting technique to get perfect aligned rivets. I haven't tried that yet. Some where on the forum I believe I posted the manual riveter I made many years ago. I've used that successfully, but only for HO scale.


I'll look, but maybe you have an idea about acquiring different-sized probes (I'm thinking of the scriber as a probe, but maybe the end is too sharp?) to create varying-sized rivets? I've got a benchtop grinder, but I've never used it.


On my manual riveter I used drill rod sharpened to a point and then hardened.

2 - With your machining experience, I've got to ask, are you concerned about metal particles dropping onto your Sherline's Y-axis lead screw? I've found an accordion pattern online and have folded up a couple to attach to each side of the mill table. Maybe it's not worth the bother? I'll upload a photo of them, only if you're interested, though.


Since I only use brass on my Sherline mill I'm not that concerned about particles falling on the lead screws. I also have a pattern for way covers but have never made any. No need for a picture unless somebody else is interested in seeing what it looks like.

(I've been learning Fusion 360 software and have begun 3D drawing an injection milling machine. I've never cut metal on my Sherline, but looks like I'm going to have to tackle that pretty soon. If you're willing, I'd like to ask you some speed/rate milling questions when the time comes.)


I don't use any formulae to figure feed and speed. I do it by visual, sound and a gut feeling. This may sound non technical. It's a "feel" kind of thing with me. From past experience I think calculating feed and speed gets you close. It's also of over 30 years in machining experience that helps. I guess that's not much of help to you here.

3 - When I create seams, I use either a small end mill (got 'em down to .005" diameter) or sometimes a pyramid cutter. Is there an advantage to using a scriber in this situation, or is it six of one and a half-dozen of another?


One reason I use a scriber to create seams is the speed. In other words I can crank up the feed rate and get the scribing done fast. A cutter of say .005" would need a very high spindle speed. My Sherline is only capable of a few thousand RPM's so the feed rate would be very slow. Plus I think a lot of cutter would get broke before reaching the ideal feed and speed. A "pyramid" cutter would leave a wider groove at the top the deeper you go. That was the reason for choosing a scriber versus a "V" groove cutter. At the depth to make a visible groove for the boards I wound up with a wider groove than board width.

Thanks much, Brian


You're very welcome.

Bernd
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Re: Machining Techniques

Postby ConnRiver » Fri Apr 28, 2017 9:51 am

Good stuff, thanks, Bernd.

-Brian

P.S. - And, quit calling me Brain (if only it were true).

;-)
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Re: Machining Techniques

Postby Bernd » Sat Apr 29, 2017 7:55 am

ConnRiver wrote:Good stuff, thanks, Bernd.

-Brian


You're welcome.

P.S. - And, quit calling me Brain (if only it were true).

;-)


Ok, ConnRiver it is then. :smile: :wink:
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Re: Machining Techniques

Postby ConducTTor » Sat Apr 29, 2017 11:49 pm

Great topic - thanks for starting.
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Re: Machining Techniques

Postby Bernd » Sun Apr 30, 2017 7:55 am

ConducTTor wrote:Great topic - thanks for starting.


You're welcome Alex.

We have a good pool of members here that are making things. Perhaps one of them will be the next Bachmann in TT scale. You never know. Or some major manufacturer stops by to see what we are doing and helps out. You never know.

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