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fortycoats
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Surface Grinding to Achieve a Bullnose Finish?

07/13/2010 11:41 AM

Hello All,

Not sure if this is in the right section but here goes anyway. Is there a tool that can be used to create a bullnose / round finish on the end of a 1.5mm Nitinol rod? We tried using a grinding machine but this created more of a chamfer (beveled edge) as opposed to a rad (bullnose) ideally I would like a tool that could be fitted into a chuck and used with a drill.
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farmatt
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#1

Re: Surface grinding to achieve a bullnose finish?

07/13/2010 11:58 AM

not sure about Nitinol rod, but we use a system in a hydraulic press to put a bull nose on steel rod when we make gate hinge pins on the farm

Judging from what I see from googling it, this method may not work

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Unredundant
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#2

Re: Surface grinding to achieve a bullnose finish?

07/13/2010 12:02 PM

If the rod is not too long (in danger of whipping), chuck it in a drill or drill press and hand dress it with a file.

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fortycoats
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#3
In reply to #2

Re: Surface grinding to achieve a bullnose finish?

07/13/2010 12:07 PM

Thanks for the prompt reply. Unfortunately the rod is 15 inches lond so i will need to clamp the rod and get at it with something on the end of a drill. I thought about using a lathe but the chuck is too big.
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Unredundant
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#5
In reply to #3

Re: Surface grinding to achieve a bullnose finish?

07/13/2010 12:16 PM

If it is not super critical you can use the lathe and hacksaw or slitter wheel to make a collet and use the collet as a shim for the lathe chuck.

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kramarat
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#10
In reply to #3

Re: Surface grinding to achieve a bullnose finish?

07/13/2010 6:22 PM

The flat holding surface beneath the chuck on my drill press can be loosened and lowered, or completely swung out of the way. If your making a lot of these you may be able to contact companies that make grinding wheels and get them to customize something for your application.

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#9
In reply to #2

Re: Surface grinding to achieve a bullnose finish?

07/13/2010 5:46 PM

Nitinol, if I'm correct, is an extremely hard material. It is used in high security locks and hasps. If you try to cut it with a hacksaw, it will just take the teeth off. Only a diamond wheel can be used to shape this material. Chucking it in a lathe and holding a diamond sharpening stone against the end will work, but it will be a freehand operation.
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lyn
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#4

Re: Surface Grinding to Achieve a Bullnose Finish?

07/13/2010 12:13 PM

A quick search of "outside radius cutter" National Supply Source Radius Cutters National Supply Source suppliers of Radius Cutters. ... ideal for use on chuckers • Use for generating radii on outside diameter of workpiece • Amoung others. Also: Search GlobalSpec for outside radius cutter.
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fortycoats
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#6
In reply to #4

Re: Surface Grinding to Achieve a Bullnose Finish?

07/13/2010 12:31 PM

Lynlynch, You're a mine of information! you were helping me out on a totally unrelated topic last week aswell
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Doorman
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#7
In reply to #6

Re: Surface Grinding to Achieve a Bullnose Finish?

07/13/2010 1:38 PM

Well done, partner!

I will do the customary thing after an OP identifies the solution as helpful. I will hit the 'Rate' button in the left hand corner of your post #4, and select 'Good Answer".

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lyn
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#8
In reply to #6

Re: Surface Grinding to Achieve a Bullnose Finish?

07/13/2010 2:16 PM

I hope it's mostly good information. I see you made progress on the PVP problem.

Thanks all.
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The Mechanic
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#11

Re: Surface Grinding to Achieve a Bullnose Finish?

07/14/2010 8:08 AM

You can grind the parts yourself. There is a tool called a tangent radius dresser. It does what the name implies. Use it on a surface grinder to dress the wheel for custom applications. These are used with gage blocks to adjust the height of the dressing diamond to dress concave, convex radii as well as straight lines tangent to the radius. They are expensive but worth the money when you have a real need for it.

Another option is a norbide stick. Made of boron nitride they can be used to free hand dress a grinding wheel made of medium grit, medium and soft-grade and a vitrified bond. It is not as expensive or accurate. But if the application does not require a high degree of accuracy this would be a great choice. I keep one of these in my tool box to dress grinding wheels when I need a custom shape that is not real precise.
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fortycoats
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#12
In reply to #11

Re: Surface Grinding to Achieve a Bullnose Finish?

07/14/2010 9:14 AM

Very good. That is the proper tool i think. This will probably be a once off job but I will look into purchasing this equipment. If its not crazy dear i might get one. I also found this. I requested a quote. Not as accurate but it might do the trick. page 9 of the attached document.
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Hooker
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#13

Re: Surface Grinding to Achieve a Bullnose Finish?

07/14/2010 12:01 PM

When I was in the shop, we used to make lathe cross-slide attachments like these for radius/sphere cutting.

Seems hardly worth it for 1.5mm rod though if you could just chuck it up some how and hit it with a file.

Hooker
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Anonymous Poster (1); Doorman (1); farmatt (1); fortycoats (3); Hooker (1); kramarat (1); lyn (2); The Mechanic (1); Unredundant (2)

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