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Grinding your own lathe tools?


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Is anyone out there grinding their own HHS lathe tools? I need to do some precision lathe work on wood. I have been using HSS lathe bits purchased online and even ground a few of my own.

I'm wondering if I could grind or even mill 1/8 - 1/4 inch brass square bar stock and use that to shape wood rather than using HSS. The brass would be much easier to shape on the grinder or mill and I'm thinking the brass edge would be sharp enough to use on wood. 

The project requires a small round over edge as well as a very narrow groove.

 

Thoughts?

Dave

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I expect most anybody with a lathe grinds their own cutting tools at one point or another. I don't see why brass couldn't be used for turning wood in a pinch, but why would you want to go to the trouble of grinding the tool in brass when a HSS tool would be no more difficult to make from a standard blank on the grinding wheel than the brass one and would be far easier to sharpen to an edge that would last much better than the brass one. (Lathe tools are ground, not milled, at least as far as my experience with them goes.) For custom shapes to turn wood, a custom-shaped cutter blade can be rather easily made from any scrap metal such as an old disposable utility knife blade or even a heavy single edge razor blade using a Dremel tool for grinding and shaping the edge you want for turning out belaying pins and the like. (When I do this, I put the blade in a small long-nosed pair of vise-grip pliers and rest the pliers on the turning tool rest.) Gerald Wingrove's book, The Techniques of Ship Modeling, covers this technique in depth. 

 

Most any of the many lathe operation manuals available for free download online, such as the excellent U.S. military training manuals. South Bend's How to Run a Lathe, and Atlas Machine Tools Manual of Lathe Operation, will have chapters on the proper grinding procedure for various types of cutting tools.

 

If all you want to do is turn a "small round over edge" and a "very narrow groove," in wood, I'd suggest you try cutting the groove with a jeweler's saw or similar saw or a suitably sized file and shape the rounded edge freehand with a flat jeweler's file or sanding stick. Grooves are easily made with a parting tool of the required thickness if you have one or a parting tool can be made of a piece of metal of the desired thickness with a corner sharpened.

 

 

 

 

Edited by Bob Cleek
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Dave, what Bob says is right. However, to answer your specific question, you can make a cutter out of brass which may suit the occasional odd job. It will not keep an edge and sharpening will probably change any profile you previously had. 

So, I reccomend sticking with HSS or carbide cutters. It's very rewarding to grind your own cutters and not difficult. 

HTH 

Bruce 

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Square stock for making shaft keys, (Keystock) is available from industrial supply stores and even some better hardware stores.  I don’t know the exact chemical analysis of this material but suspect that it is ordinary non  hardenable low carbon steel. This would work for turning tools intended for short term service and would probably last longer than brass.

 

I personally find an ordinary bench grinder difficult to use as the circular grinding wheel makes it hard to form straight shapes.  I have one of those stationary belt sanders with a 30in circumference x 1in wide belt.  I tried using this to form a lathe tool and it worked fine.  It also worked better at controlling the temperature of the tool blank during grinding than the bench grinder.

 

Roger

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Here is a further explanation of my question. I have decided to make this lower section of the mast out of a single piece of wood on the lathe. The cut at the top needs to be wrapped with a brass band. I can grind a HSS blank to make a tool for this without too much trouble.

 

Its the lower marked shaping I'm struggling with a bit. This is about 1/8 inch convex shape. I doubt I can grind accurately enough to make this tool and thought that If I made it from brass, I could use an end mill on the mill to cut it. I really dont want to try milling a piece of HSS.

 

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McMaster-Carr does make a tool for this is sizes from 1/32 and up as pictured below. But the cost for a single 1/4 inch shank tool is around $35.00. 

 

I'm assuming the size of the tool is measured by the distance between the red lines I have drawn. Please correct me if I'm wrong.

 

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I hope this clarifies things a bit.

 

Dave

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If you want to mill the tool to shape i suggest the following:-

 

Buy some silver steel.

Mill the shape you want into it.

Heat to cherry red and then quench in cold water. (this hardens the tool so that it retains an edge)

Touch up the edges with a diamond file if necessary.

 

Silver steel in its unhardened form can be cut quite easily with HSS tools.

 

I often use this technique for making tools for cutting brass so it will be fine for cutting wood.

Edited by KeithAug
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Chances are you already have miniature wood cutters like the ones pictured. There is also a chance that one of them is already suitable for your needs. These cutters have usually round shanks, but then either a V-type tool holder or a regular one with an additional V-grooved shim (both pictured) will suffice. Just an idea for a painless improvising.

 

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Using the router bit is a trick to be filed away for future use! Brilliant indeed.

 

But... for that shape I'd be tempted to make it freehand with a file or sandpaper on a stick.

 

I'd suggest the following trick: Take a piece of wood a little bit thicker than the thickness of the "ring" you want and with a sharp hand plane off a few nice, curly shavings. wrap these shavings around the spar at the place you want the "ring," laminating the wrapped shaving with wood glue. Add enough turns to make the glued on "ring" higher than the finished one you want to make. When the glue on the laminated "rings" is hardened, turn the spar in the lathe and turn the "rings" to the width, height, and shape you want with small wood turning chisels or jewelers' files. The laminated rings will be solidly part of the spar and adding them on, rather than trying to turn a much larger spar blank to size, should be a big time and work saver. Also, if for some reason you botch it up, all you need do is remove the glued "ring" by turning it off (or soaking it in alcohol if you used PVA glue) and apply another laminated "ring" and have another go at it.

 

This is also the way I make wooden mast hoops. I wrap a suitably sized wooden mandrel with plastic wrap to prevent the glue from sticking to the mandrel and laminate "hoops" the width of my plane shavings. Then I sand them down to the desired scale thickness and part them on the mandrel with a hobby knife or jeweler's saw (depending upon the thickness of the hoops,) and slide them off the mandrel.

 

Turning small shapes like you've illustrated above is quite easily done using a sanding stick and/or turning knife. It's much easier than making a dedicated cutter tool to do it, unless, of course, you need to make many of the same shape, e.g. belaying pints.

Edited by Bob Cleek
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