Radius Cutting on the Lathe - Quick Way

Introduction: Radius Cutting on the Lathe - Quick Way

About: Aerospace welder and party animal

Attention to details is very important ... those little things are the things that make a project stand out or keep customers coming back.

I have been in the children's science museum world for years now designing and building world class exhibits.

Number 1 priority is no one gets hurt which means no sharp edged and the finish work is complete to safe levels.

Number 2 is learning and having fun ( maybe that's 2 things but I can't decided whats better)

Various sized radius edges on parts is very important for safety - heres a quick look at how its done and to blueprint

I come from a background of 10+ years as a certified aerospace welder and prototype fabricator and these tips and tricks I share are some of the lessons I have learned from the pros.

Want to know more about me and my background - MonkeyLikeShiny.blogspot.com

Step 1: Different Types of Radius Tooling

starting from left to right

tool #1 Carbide radius tool designed for the lathe - designed for cutting harder to cut metals such as Stainless but works well for softer as well - these are some of the best tools for life span but expensive and not always in the radius you need to keep a part to spec. If you need a special radius or profile, the carbide requires a special grinding wheel which makes it an extra step not easily accessible to small shop users. Often you buy them with preset radius.

Custom ground High Speed Steel cutters - both the #2 and #3 cutters are different styles of cutters I have ground to do jobs on the lathe. These are great but you spend time and need radius gauges to check your grind and make sure you have the right profile - The plus side of these tools is that it can be shaped on a basic pedestal grinder with a normal grinding wheel to get the exact shape and the steel blank cutters are cheap or can be found by the boxes at garage sales or swap meets due to professional shops moving to carbide for everything and like carbide tooling listed above these tools are designed for a good amount of work load.

Tool #4 and #5 are High Speed Steel cutters designed for milling machines with a bigger shank and multiple cutting surfaces. They have a preset radius already and is written on the side of the tool making it easy to do cutting to blueprints.

TIP - the coolest part of having a mill cutter with 4 cutter surfaces is you can grind in theory 4 different profiles if you need ( this will make it useless as a milling machine cutter ) but then you will have a custom tool with 4 different radiuses you can keep by the lathe for various jobs.

Tool #5 and #6 are carbide cutters used for a router - they are very easy to source and as you know when your working on a project late on a Saturday night... theres nothing worse then not having tools until Monday... so to the big box store you go, which most likely has a large assortment of router bits with all kinds of wild profiles and radius.

Remember that using router bits for lathe work needs to be noted that the shank is 1/4 inch so extreme cutting and tough materials can cause breakage, the router bits shouldn't be run on big radius with heavy cutting.

USING Radius cutters of any size or shape needs to be done safely!

It is important to understand that your speeds and feeds of the lathe need to be correct, along with tool hights, this is important because of the cutter engagement - You are making a full face contact with a tool so having the tool too low can cause it to grab the more engagement you have, either causing the tool to chatter, wrecking your part, tool breakage or risking safety.

Step 2: Cutting With a Milling Radius Tool

as you can see it works well.... its my favorite because I have a bunch of different sizes, they are ridged and have 4 cutting surfaces as they wear out and the most important thing is that I can use them on the mill and lathe so I can save money and not buy so much tooling!

Because of the full radius engagement it is always recommended to keep the speeds lower and heights correct, running at the wrong height could cause chatter, tool breakage, parts becoming scrap or your own safety.

Step 3: Router Bits... Quick and Dirty....

Not always recommended because of their strength of the smaller shank, the router bit is a quick way to get some radius needed and because all the hardware stores carry them in almost every shape and size its a great thing to use on lighter materials such as plastics and aluminum and when you don't have time to wait for a supplier to ship you a radius tool.

Here I used a weird profile shape on some aluminum to create something that might turn in to a cool art project. Just neat to try some of the shapes and see what it looks like when you put some cool edges to your round parts.

Try it and have fun... Remember SAFETY is so important when working on the lathe and in the shop !!

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    5 Discussions


    6 years ago on Introduction

    the best part about using a milling radius cutter is not that each cutting edge can be groung to a different radius.
    It is because the extra cutting edges provide the ability to index the dutter, when one edge becomes worn or chipped!
    Also, remember to rough cut your shape using traditional tooling, to minimize wear on your 'speciality tooling'

    Great idea though!


    4 years ago

    how do you turn an exterior radius like whats on a ring?


    Reply 2 years ago

    You could use the same procedure, just pivot your form tool so the center axis of the radius is perpendicular to the ways.


    2 years ago

    Making & using radiused form tools is pretty cool.

    I followed the headline to here looking for a 'radius bar' to do larger arcs. I eventually found a cool article in the December 1958 popular mechanics (pages 193-196) which had good pics.

    Basically, you make a double-pointed bar of the radius you want, (they suggest it works for 3" radius minimum) and use it as a spacer between the cross-slide and the tailstock or headstock. Then you keep light pressure with the feed wheel against the radius bar as you traverse with the cross-slide, letting the radius bar control the path. The pics at PM are good--then ends of the pointed radius bar fit into shallow holes drilled into your cross-slide and tailstock, or they also suggest making a wooden pivot block with a hole to clamp to the bed. Also, the compound slide is set parallel to the ways, so you can use the compound slide to take deeper and deeper cuts.


    6 years ago on Step 3

    Very helpful. I loved the idea of using a router bit for softer materials.