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[4]

I need a turning tool made.

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Harvey

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#1
I need a 5/32" dia (5/16" Wide) round-nosed cutting tool made so I can groove the three rollers in my Harbor Freight slip roller and allow me to form a large radius bend in a piece of 5/16"OD 4130 tube (.035" wall). I think my HF rollers are mild steel.

The guys explained how to make this tool in another forum but since it would be my first time to grind my own tool, I lack the confidence to do it right. I probably need only one but if the price is right, it might be a good idea to have two made so I can have a backup. My quick-change tool holder can take up to 5/8 square tooling.

Thanks,

Harvey
 

JimDawson

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#4
I lack the confidence to do it right.

Harvey, the best way to gain confidence is to just do it. As long as the cutting edge is sticking out farther than everything else, then it will work. May not be perfect, but you're not getting paid by the hour either, you can always grind again. ;)
 

RandyM

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#5
Harvey, the best way to gain confidence is to just do it. As long as the cutting edge is sticking out farther than everything else, then it will work. May not be perfect, but you're not getting paid by the hour either, you can always grind again. ;)
Yup, try and try again. If you are too afraid to make mistakes nothing will ever get done. I know this stuff can be scary, but you have to try. And a tool bit is probably the best thing to experiment on. You just keep grinding until you get it right. You don't scrap the bit until it is ground down to nothing.
 

kdecelles

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#6
Harvey, the best way to gain confidence is to just do it. As long as the cutting edge is sticking out farther than everything else, then it will work. May not be perfect, but you're not getting paid by the hour either, you can always grind again. ;)
Yup, try and try again. If you are too afraid to make mistakes nothing will ever get done. I know this stuff can be scary, but you have to try. And a tool bit is probably the best thing to experiment on. You just keep grinding until you get it right. You don't scrap the bit until it is ground down to nothing.
Amen. I ground my second-ever bit last night . Turned like garbage. Wasn't the bit, was SFM (speed) issue. Way too fast. Read the books , follow the notes, "read the chips"


Sent from my iPhone using Tapatalk
 

Harvey

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#7
Thanks Guys. Please understand that I appreciate your encouragement to try grinding my own tool bit but I've decided to take UlmaDoctor up on his kind offer to make a tool bit for me.

My reasoning is multifold: My sole grinder is a worn-out Harbor Freight pedestal grinder that I bought 20 or so years ago and have only used it (so far) to sharpen my lawnmower blades. Yes, I could spring for a new (better) grinder, and a wheel suitable for grinding tool bits but that would be quite a price increase for the one 5/16d round-nosed bit that I need right now. While I will understand that your logical rebuttal will be that as a lathe owner I will likely need a quality grinder for fabricating additional custom tool bits in the future; the truth is that I've owned my Grizzly 12x36 lathe for 7 years now and this is the first and only time I've needed to make a custom bit. I MAY eventually resort to buying a better shop grinder in the future but as you can see, it's not financially justifiable right now.

That said, I'm not closing down this discussion of trying my hand at "rolling my own". I'm always willing to learn about and embrace new skills. Heck, that's why I joined this fine forum!

Harv
 
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HBilly1022

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#8
I'm in the "just do it" camp.

The best way to learn is to have an experienced machinist at your side showing you what to do and then trying it yourself. But most of us don't have that opportunity. So the second best way is to try it and if something doesn't work out, there is a huge community of people on this forum that are eager to help you get through it. There have been times when I needed a lot of help and always got it. There is a real sense of satisfaction when it all comes together and you finish the part. And it is made of metal, so you will get to admire your work a very long time.

Edit, posted while you were responding. I have a cheap grinder too and have found a way to balance the wheels that works great. Now the cheapo grinder feels and sounds smooth. If your interested there is a thread that shows it. https://www.hobby-machinist.com/threads/bench-grinder-run-out.65262/#post-545463
 
Last edited:

hermetic

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#9
Don't think for a minute you will have a problem making the tool, you will need to square up your grinding wheel with a wheel dresser, or a piece of scrap, but form tools of this type need a powerful lathe and a very rigid set up if you are going to plunge it straight in, so take out the bulk of the slot using conventional lathe tools, then use the form tool to bring it to the correct size and shape. Good luck with it!
 
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