Threading Tool Grinding Gauge

prusaprinters

<p>This tool is used to gauge the grinding the a thread cutting tool for a lathe. This idea is not original with me - all credit goes to this Shop and Math video :</p> <p> <figure class="media"> <oembed url="https://www.youtube.com/watch?v=DQadHSyx_Zs&amp;t=608s"></oembed> </figure> </p> <p>The STL file from that video is here : <a href="https://tinyurl.com/y84atxne">https://tinyurl.com/y84atxne</a></p> <p>The above video is well worth watching for tips on how to use the gauge, as well as tips on actually grinding the thread cutting tool.</p> <p>The original gauge from the above link is quite good, but I wanted to create my own version(s) for several reasons. First, I always like to re-create STL files in CAD whenever I can, because it's a good way to improve my CAD skills. Second, I thought of a couple of what I believe are minor improvements in the original design. And finally, the original design is for 3/8" lathe bits only, and I wanted to also make one for 1/4" bits for my mini-lathe.</p> <p>The minor improvements I made are as follows:</p> <ul> <li>I redesigned the alignment and angle posts to give them all a large fillet (stronger)</li> <li>the angle gauge posts for the 60° tip have straight sides, which I think makes for easier checking in the early stages of grinding</li> <li>I added an "angle line" to check the 8° face angles of the point</li> <li>I added a chamfer to the bottom of the scribing guide for scriber clearance</li> </ul> <p>The Shop and Math video talks about how to use the gauge, but here are some brief instructions anyway See photos):</p> <ul> <li>mark the tool bit with a sharpie, Dykem, etc., and then use the scribing guide (the triangular opening) and a scriber to mark the angle to be ground on the end of the tool bit.</li> <li>grind the end of the tool bit to fit the triangular opening on the right end of the gauge</li> <li>grind the relief angle on the two faces to match the angle mark (with the tool bit sideways)</li> </ul> <p>An additional note about the relief angle: The two faces are to be ground to a relief angle of 8°; as a result of this, the profile angle of the tip will actually be closer to 13.5° (which is the angle of the angle guide on the flat of the gauge).</p> <p>The OnShape 3D CAD files for this are here :</p> <p><a href="https://cad.onshape.com/documents/2c7fd8c744729c5ce3078e14/w/68fcd572ef0487ef654c7152/e/b1b948e61dfbc075943df0e6">https://cad.onshape.com/documents/2c7fd8c744729c5ce3078e14/w/68fcd572ef0487ef654c7152/e/b1b948e61dfbc075943df0e6</a></p> <h3>Print instructions</h3><p>Use the 3mf files provided to print in PLA.</p> <p>Note that the gauges are provided in two sizes as noted previously - one for 3/8" and one for 1/4" tool bits.</p> <p>The gauges can probably be scaled to work with other tool bit sizes, but I have not tried this. Note that you must use a gauge sized to fit your tool bit if you want the cutting point to be centered.</p>