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  1. #1
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    Default milling aluminium with woodwork router bits

    I want to make a couple of hawse fairleads, like this
    https://www.amazon.com/WARN-94244-Ha.../dp/B018AIHO5W

    Planning on casting in aluminium. I've been looking at corner-rounding endmills and the price for one with around 1" radius is way over the top. I'm wondering if it is worth trying a woodwork rounding-over bit like this
    https://www.ebay.com.au/itm/264169233241?
    and what are the pitfalls of doing so?

  2. #2
    BobL is online now Member: Blue and white apron brigade
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    BIL is an Al boilermaker on shipbuilding duties at Naval base here in WA. His toolkit includes a bunch of ww tools including hand held WW circulars,, jigsaws, and routers. He regularly slightly over fills TIG & MIG welds and rounds over with round over router bits. He welds lots of curved surfaces and by the time hes finished they look seamless.

  3. #3
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    I used the wood router to cut this dovetail. It worked with mild steel and aluminium is softer.

    20160721_230016.jpg

  4. #4
    BobL is online now Member: Blue and white apron brigade
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    Wax or meths can be used as a lube for Al.

  5. #5
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    The V groove in these was cut with a router bit
    Attached Images Attached Images

  6. #6
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    Well that's very good to know, I'll have to get a suitable rounding-over bit and give it a try. Around one-tenth of the price for a router bit as for a milling cutter. Might be a bit of a challenge for a collet to hold onto a cutter with a 3" o.d. and a 1/2" shank, I guess I'll just take it gently.

  7. #7
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    Cast ally is easier to route than some hardwood.
    Having said that, Id consider machining them over casting them if you want them to last.

  8. #8
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    Quote Originally Posted by Pete O View Post
    Well that's very good to know, I'll have to get a suitable rounding-over bit and give it a try. Around one-tenth of the price for a router bit as for a milling cutter. Might be a bit of a challenge for a collet to hold onto a cutter with a 3" o.d. and a 1/2" shank, I guess I'll just take it gently.
    Hi Pete, Guys,

    3 inch diameter is a very big and expensive cutter even for a router toolbit ! I very much doubt that you will need one that big. If you are doing the ends in one operation, I would go for a form tool in the lathe and use a four jaw to hold the work.
    Best Regards:
    Baron J.

  9. #9
    BobL is online now Member: Blue and white apron brigade
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    Quote Originally Posted by Pete O View Post
    Well that's very good to know, I'll have to get a suitable rounding-over bit and give it a try. Around one-tenth of the price for a router bit as for a milling cutter. Might be a bit of a challenge for a collet to hold onto a cutter with a 3" o.d. and a 1/2" shank, I guess I'll just take it gently.
    The largest round-over bit I have seen BIL use is a 25mm OD cutter.

  10. #10
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    The inside radius where the rope comes out only needs to be around 10ish mm.
    Out side radius for aesthetics can be whatever you want, I commonly use an R3 for stuff like that.
    Both are significantly smaller than 3"

  11. #11
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    Quote Originally Posted by Pete O View Post
    I'm wondering if it is worth trying a woodwork rounding-over bit like this
    https://www.ebay.com.au/itm/264169233241?
    Pete,
    that bit has an 8mm radius. I think this is the one you want (maybe): https://unitedtoolsmckinnon.com.au/p...ver-router-bit
    Chris

  12. #12
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    Quote Originally Posted by Pete O View Post
    ...Planning on casting in aluminium...
    To ask the obvious, why? Unless you are planning on making lots of them by the time you have made a pattern, well, you have already made one. What's one or two extra...

    Quote Originally Posted by Pete O View Post
    I'm wondering if it is worth trying a woodwork rounding-over bit ...and what are the pitfalls of doing so?
    Carbide wood bits work fine on Al. The bigger the radius, the slower the rpm though. As others have suggested, for cosmetics any radius will do so chose something manageable.

    Michael

  13. #13
    elanjacobs is online now Apprentice gear maker and machine doctor
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    Quote Originally Posted by Pete O View Post
    Well that's very good to know, I'll have to get a suitable rounding-over bit and give it a try. Around one-tenth of the price for a router bit as for a milling cutter. Might be a bit of a challenge for a collet to hold onto a cutter with a 3" o.d. and a 1/2" shank, I guess I'll just take it gently.
    No problem holding it, I've run plenty of 2.5" diameter bits in wood, both by hand and in a CNC, and they don't go anywhere. Just go easy on the feed, use lube as mentioned above and don't try to cut too deep in one pass; once you start approaching full profile, I'd be doing no more than 1mm depth per pass

  14. #14
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    Quote Originally Posted by BaronJ View Post
    Hi Pete, Guys,

    3 inch diameter is a very big and expensive cutter even for a router toolbit ! I very much doubt that you will need one that big. If you are doing the ends in one operation, I would go for a form tool in the lathe and use a four jaw to hold the work.

    A router cutter with a radius of about 3/4" appears to have an outside diameter somewhere in the vicinity of 3 inches, just from looking at photos at present (edit- I was guesstimating based on 1/2" shank but the one I was looking at is probably 1/4" shank. So much smaller OD than I thought.)...I'm talking here about milling the inside of the slot to give a radius for the rope to run on, not the outside of the body of the thing. which I think is what you mean in the suggestion above about using the lathe? I can't see any way to machine the inside of the slot in a lathe rather than a mill.

    I'm actually going a bit cold on the casting idea, I was originally thinking of casting them with lettering or some other design but I've decided that's a waste of time so I'm now thinking just mill them from a billet. The better quality bought ones appear to be about 1.5" thick with a 3/4" radius on both the back and front inside the slot for the rope to run over. So I'm looking at a router bit with about that radius.

    Another thought- if I'm going to mill them from stock, what about steel stock? I know with this sort of thing, the harder the material the better, as it is damaged surfaces that damage the rope. I have some leftover offcuts of forklift tine (almost certainly 4140) in ideal dimensions; would I have any hope of radiusing that with a router bit?

  15. #15
    elanjacobs is online now Apprentice gear maker and machine doctor
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    Quote Originally Posted by Pete O View Post
    I have some leftover offcuts of forklift tine (almost certainly 4140) in ideal dimensions; would I have any hope of radiusing that with a router bit?
    The carbide grades used for woodworking tools are relatively brittle, I'm not so sure they would cope with something that tough. You might actually be better with HSS

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