milling gunmetal

[old wrinklyParticipant @oldwrinkly]

[old wrinklyParticipant @oldwrinkly]

I all, just about to start milling gunmetal horncheeks, not sure if you use coolant or not, also speed. will use a 8-10 mm end-mill (afraid to make a mess) dek

[JasonBModerator @jasonb]

Cut dry but with a SHARP cutter, if in doubt buy a new one. If your cutter is leaving burrs its not sharp enough.

[old wrinklyParticipant @oldwrinkly]

Hi jasonb thank you for the info, would it be a help if I first removed the top layer with a used endmill first or am I getting confused with cast iron, (have some wheel castings to do in the near future) dek

[KWILParticipant @kwil]

No need to deal with "a top layer" with GM, cuts like butter.

[JasonBModerator @jasonb]

As KWIL says its quite a soft material and does not have a skin like CI, the fact it cuts like butter is why you need sharp cutters a sblunt ones will push up a large burr.

A quick going over with a wire brush won't hurt just to make sure there is no sand stuck on the surface.

I do sometimes use a bit of soluable oil when drilling large holes in the stuff as the drill can get hot and stick.

[old wrinklyParticipant @oldwrinkly]

Hi guys thanks for your replys, I feel alot more comfident after reading your replys, will get the wire brush out tomorrow and crack on, thanks again dek

[julian atkinsParticipant @julianatkins58923]

hi dek,

on locos i machine the facings to fit the frames with a tight fit (with as Jason and KWIL describe a sharp end mill), then rivet to the frames, and use a long end mill to machine the sides for the axleboxes taking very small cuts and setting the frames back to back in the mill. i have a few special long end mills i use only for such jobs. perfect parallel slots are then achieved which of course assists everything else latter on.

cheers,

julian

[old wrinklyParticipant @oldwrinkly]

Hi julian

sounds a better way than in the sweet pea book, but I have already bolted the frames together, if I mill the horncheeks and fit only one on each slot, and square of the frames, then mill the axleboxs, and place them in position, and push the other horncheek against it, drill and bolt, it should give a good fit. (what do you think)

regards dek

[KWILParticipant @kwil]

That all depend upon whether your frames when assembled are dead in line. If you have the machine space, assemble the frames. take the final cuts across from one to the other, dead square as well then on the axles.

[old wrinklyParticipant @oldwrinkly]

Hi all, I think I can just make it with your idea kwil, will measure next time in the workshop, thanks to all, dek

[Chris GunnParticipant @chrisgunn36534]

Just be careful when drilling holes in gunmetal, the drill can easily snatch in the work, so make sure the work is securely clamped in the vice, and the vice is clamped as well. DO NOT be tempted to hold the workpiece by hand. Also do not be tempted to put a pilot drill through and then open up the hole, as the drill will snatch for sure.

Chris Gunn

[julian atkinsParticipant @julianatkins58923]

hi chris,

that will only happen if you havent backed off the edge of the drill same as you would do when drilling brass.

i have a set of drills and reamers each for brass, steel, and cast iron and i never mix them up!

cheers,

julian

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