# HSS Lathe form tool shaping



## Michael Tod (Jul 18, 2018)

I need to make some 1/2 inch HHS form tools for my lathe I was thinking of buying some blanks then shaping them using a carbide tool on my mill. 

But from what I can tell that's a bad idea.

Does anyone have any other methods short of surface grinder (I don't have one ) or buying tool steal then hardening ?

I need to make a 5/32 half round for some brass dynamo connections.

Thanks
Mike


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## abby (Jul 18, 2018)

Mike surely you have a bench grinder ? I can't imagine a home machine shop without one. You grind all your HSS lathe tools by hand and finish if you need to using a diamond hone.
For more complex form tools use carbon tool steel , machine or file the desired shape then harden and temper .......straw colour.
Dan.


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## Michael Tod (Jul 18, 2018)

abby said:


> Mike surely you have a bench grinder ? I can't imagine a home machine shop without one. You grind all your HSS lathe tools by hand and finish if you need to using a diamond hone.
> For more complex form tools use carbon tool steel , machine or file the desired shape then harden and temper .......straw colour.
> Dan.



Thanks

I do a few in fact but this is a Radius all my grinders are flat I thought about the tool steel approach but where I'm at that could be difficult.
I don't have any way to heat it and the neighbors may not like me torching some metal.

Mike


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## MachineTom (Jul 18, 2018)

You can buy preformed HSS cutters. If you want a 180 degree bead use a carbide Burr type cutter eats through HSS. However be ready to deal with chatter, when making that bead depending on work material, lathe etc.


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## tornitore45 (Jul 20, 2018)

Tool steel is easy to machine in its annealed state and easy to harden with a torch,

If you have a piece of O1  carbon steel put in the wise at 5 degrees and mill the half round into the face.  That will give you the 5 degrees front relief.

You certainly have a 1/2" piece of drill rod laying around.  Mill it rectangular for about 3/4" in length and then proceed as above.

I have done about a dozen 1/2 round form tools this way.


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## SmithDoor (Jul 20, 2018)

I use a 1/4" x 6" grinding wheel for shape tool bits

Dave 





Michael Tod said:


> I need to make some 1/2 inch HHS form tools for my lathe I was thinking of buying some blanks then shaping them using a carbide tool on my mill.
> 
> But from what I can tell that's a bad idea.
> 
> ...


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## TonyM (Jul 20, 2018)

I have made form tools for half round by grinding left and right quarters. Not too onerous on an off hand grinder followed by honing.


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## Wizard69 (Jul 20, 2018)

Hand grinding at the bench grinder is something that needs to be practiced as sooner or later you will need a tool that can only be had that way.    That being said it can take a very long time to grind quality HSS. 

If you are looking for specific radius cutters you might want to look at carbide insert tooling using round inserts.    This only works if a standard radius meets your needs.    

Your next choice is to get a tool grinder set up with a radiusing facility.   This can be done  DIY with a bench grinder or you can build a more elaborate tool grinder.   You would still be shaping HSS but wouold have more control over radius quality and size.

Another choice is to learn how to make "form" tooling on the lathe from tool steel.   This is a very good choice for light work and can actually allow you to create a variety of cutter shapes. with good precision.   You will need to learn how to harden O1 and similar steels.    Lot sof info on the net for making form tools and the holders required.


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## tornitore45 (Jul 20, 2018)

I think the OP is talking about making a nearly spherical shape NOT a semicircular groove.   Dynamo connection posts.   Is a lot easier to grind a round nose tool than one with round depression in the front.  Use an end mill on tool steel and harden it.


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## Hopper (Jul 20, 2018)

If it is a convex tool bit you want to make -- in order to turn a groove in the job -- rough it out by hand on the bench grinder, using a radius gauge as a template. Then finish to fit the gauge with a diamond file or abrasive slip stone. Even a bench oil stone as used for sharpening knives and lathe tool bit edges. If you don't have a radius gauge, make one by drilling a hole in a piece of sheet metal and cutting it in half through the hole. If it is just for a dynamo connection it does not have to be a precision shape, it just needs to look good.


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## goldstar31 (Jul 21, 2018)

Probably a 5/32nd rat tailed file might be suitable????

Norm


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## gmaf (Jul 21, 2018)

Michael,
Since your cutting brass you can use a method I've been using for years. First of all hand grind two thirds off the underside of your 1/2 " tool bit.  You won't need that much thickness if your cutting brass.Plus it makes it A LOT easier grinding your radius. Just remove an area right under where you plan to grind your radius. Use Dykem or a magic marker and then scribe your radius using a radius gauge.  Using a Dremel cutoff wheel grind away as much material as you can but stay shy of your scribe line. Using a cone shaped stone burr , come up from underneath and slowly grind to your scribed line. The cone shape of the stone automatically puts relief on the cutter. You'll probably have a slight bur on the top of your cutting edge but a few laps on a flat stone fixes that. 
Dremel cutoff wheels are great for making very fine lathe bits.  They can be shaped with a diamond hone to a knife edge or radius to fit a lot of needs. I've attached some photos of bits I've made. Keep in mind these were made for cutting brass.
Regards,
George


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## redhunter350 (Jul 22, 2018)

George is on the money here, I too have made many HSS form tools this way for producing one to form a sphere or half sphere, it does depend on how accurate you need to be, is the sphere functional or cosmetic? I have also dressed a wheel to size to make the form.
There is also merit in using gauge plate then hardening, when drilling tilt the work so the hole is at an angle to create the clearance, I useually finish with an end mill or slot drill when doing this
John


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## john_reese (Jul 23, 2018)

Bench grinder with a reinforced cutoff wheel to form the nsrrow features.  1/4" white wheel to form the larger features.  Dress  the wheel edges to the needed contours.  If needed finish with a dremel and diamond burrs.  Instead of grinding away half the thickness of a tool bit start with 1/2 x 1/4 .


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## XD351 (Jul 23, 2018)

You can make them from gauge plate or even an old annealed file will do for brass  ,just machine , cut , grind or  file to shape and then harden & temper then a quick hone and your away .


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## desbromilow (Jul 24, 2018)

if you go the guage plate method, 5/32" is a common size in chainsaw sharpening files - so reasonable finish, and parallel sided round file.
as for hardening and tempering and the neighbours - there is no reason why you can't harden and temper a small tool on the gas burner of your kitchen stove. the oil quench might represent its own challenge, but if it's water hardening , no problem.


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## mcostello (Aug 2, 2018)

I don't know about Your bench grinder, but Mine naturally seems to end up with a 1/8" radius on the corners. Fairly close with a little bit of tuning up to make what You want.


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