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Author: Subject: Machining alloy with a forstner drill
tegwin

posted on 25/3/15 at 10:52 PM Reply With Quote
Machining alloy with a forstner drill

I need to make a couple of pieces from alloy on the lathe... I need to produce 25mm and 30mm holes with flat bottoms...

Suitable milling cutters are upwards of £25 each... Rather a lot for a one off job... If I drill out the meat of the hole would a forstner bit be man enough to finish the job with a flat bottom?


Failing that, anyone have a 25mm/1" cutter and a 30mm cutter they would rent me?





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owelly

posted on 25/3/15 at 10:58 PM Reply With Quote
I counter-bored a lump of ally with a flat wood bit!! It chattered a bit but with plenty of oil and a very low speed, it did the job. I would say the Forstner bit would do a better job as long as you can keep the shank short or well supported to stop it from wandering off!





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owelly

posted on 25/3/15 at 11:00 PM Reply With Quote
Incidentally, is it not possible to use a boring bar to make the holes? I find grinding up old files make good tiny boring bars!!





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coozer

posted on 25/3/15 at 11:02 PM Reply With Quote
Or a reamer??





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tegwin

posted on 25/3/15 at 11:19 PM Reply With Quote
Reamers don't tend to have a cutting face on the tip!

I could use a boring bar but it's faf. I need 6 holes. It's doable but a bit to just cut to the chase would be nice

Not used my lathe for so long i can't even remember where it is!





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owelly

posted on 25/3/15 at 11:49 PM Reply With Quote
I've also used a 10mm end mill in the tool post to chovel out a 30mm flat bottomed hole....
I bet my college lecturer is spinning in his grave.....





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r1_pete

posted on 26/3/15 at 07:45 AM Reply With Quote
I used a forstner bit to square off the 15mm holes for the injectors in my modified manifold.
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chris-g

posted on 26/3/15 at 11:59 AM Reply With Quote
I have had good results milling aluminium with wood router bits. They tend to be carbide tipped and you might get one in a diameter suitable for your purposes.
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MikeRJ

posted on 26/3/15 at 12:44 PM Reply With Quote
quote:
Originally posted by chris-g
I have had good results milling aluminium with wood router bits. They tend to be carbide tipped and you might get one in a diameter suitable for your purposes.


Yep, I've also had good results with router bits on aluminium alloys.

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