{"id":36,"date":"2016-02-06T18:45:00","date_gmt":"2016-02-06T18:45:00","guid":{"rendered":"https:\/\/blog.hslracing.com\/workshop\/2016\/02\/06\/first-gear\/"},"modified":"2021-06-08T18:27:42","modified_gmt":"2021-06-08T17:27:42","slug":"first-gear","status":"publish","type":"post","link":"https:\/\/blog.hslracing.com\/workshop\/2016\/02\/first-gear.html","title":{"rendered":"First Gear"},"content":{"rendered":"

My Lathe has a 4 teeth per inch (tpi) lead screw, and the chuck thread is 1 1\/4″ 9tpi BSF.<\/p>\n

According to the screw threading data, I can cut this thread using a 40 tooth drive gear on the spindle, an idler and a 90 tooth gear on the lead screw.<\/p>\n

There are other combinations that would work, but this is the simplest.<\/p>\n

A full set of change gears for my lathe looks something like the following:<\/p>\n

20, 25, 30, 35, 38, 40, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 127.<\/p>\n

Unfortunately, I am missing most of the gears for my lathe below 55 teeth,  as well as the 127 tooth gear.<\/p>\n

Other 4 tpi lead screw lathes, such as the Cromwell 3 1\/5″ lathe, also include a second 80, a 110 and 120 tooth gears for metric and imperial threads, and then 31, 39, 43, 48, 53, 59, 66, 73 and 81 for cutting B.A. Threads.<\/p>\n

I am not overly worried about cutting the B.A. threads as I have a set of B.A. taps and dies, so can safely ignore all of the gears that are specific to those threads, however I could do with making up the missing ones from my basic set – 20, 25, 30, 35, 38? 40, 45, 50 and 127.<\/p>\n

My 60 tooth gear could also do with being replaced as it has a couple of missing teeth.<\/p>\n

Back in July 2014 I bought a set of involute gear cutters off ebay, so that I could make any of the missing gears that I needed, as finding suitable 16dp gears on the second hand market could take a while.<\/p>\n

<\/a><\/div>\n

Since I currently have a requirement to make a few chuck back plates and adapters, I thought now was as good a time as any to start with a 40 tooth gear so I can cut that 9tpi thread.<\/p>\n

A friend of mine kindly gave me some pieces of aluminium a while back and a slice off one of these makes a good starting point.<\/p>\n

First I cut off a 10mm slice on the bandsaw and then fly-cut the sawn face to make it smooth.<\/p>\n

Next I drilled the hole in the centre out to 19mm (3\/4″ is 19.01mm) and milled a keyway with a 3mm cutter (1\/8″ is 3.175mm).<\/p>\n

Next I made a mandrel out of some steel rod so I could hold the blank in the lathe and also on the rotary table.<\/p>\n

I chucked the blank on the mandrel in the lathe and reduced the outside diameter to 66.675mm (2.625″), this being the crest circle diameter for a 40tooth 16dp gear.<\/p>\n

<\/a><\/div>\n

Next I transferred the blank to the rotary table on the milling machine, using a 2 morse taper ER32 collet chuck and a 20mm collet to hold the mandrel.<\/p>\n

I set up the dividing attachment using the plate that includes a 20 hole circle and set the arms for 5 holes – my rotary table has a 90:1 reduction worm, so for each tooth I will need to rotate 2 turns and 5 holes on a 20 hole plate to give me 40 teeth in total.<\/p>\n

<\/a><\/div>\n

Cutter #3 (for 35-54 teeth) is mounted on an arbor and then set to the centre height of the blank in the rotary table, at which point I lock the Z axis.<\/p>\n

I locate the edge of the blank, dial in 1mm of cut and lock the Y axis.<\/p>\n

It is then simply a matter of making a cut on the X axis and then advancing the rotary table to the next position.<\/p>\n

<\/a><\/div>\n

Advance another 1mm and start on round two.<\/p>\n

<\/a><\/div>\n

Same again for round 3<\/p>\n

<\/a><\/div>\n

The final depth of cut is 1\/8″ or 3.175mm, so a finishing cut was taken at this depth<\/p>\n

<\/a><\/div>\n

Finally I returned the blank to the lathe and knocked off the sharp corners with a file and here is the completed gear.<\/p>\n

<\/a><\/div>\n

I have checked with some of my other gears and this gear meshes well.<\/p>\n","protected":false},"excerpt":{"rendered":"

My Lathe has a 4 teeth per inch (tpi) lead screw, and the chuck thread is 1 1\/4″ 9tpi BSF. According to the screw threading data, I can cut this thread using a 40 tooth drive gear on the spindle, an idler and a 90 tooth gear on the lead screw. There are other combinations…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[6,5,14],"class_list":["post-36","post","type-post","status-publish","format-standard","hentry","category-uncategorised","tag-gears","tag-lathe","tag-metalwork"],"_links":{"self":[{"href":"https:\/\/blog.hslracing.com\/workshop\/wp-json\/wp\/v2\/posts\/36","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.hslracing.com\/workshop\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.hslracing.com\/workshop\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.hslracing.com\/workshop\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.hslracing.com\/workshop\/wp-json\/wp\/v2\/comments?post=36"}],"version-history":[{"count":1,"href":"https:\/\/blog.hslracing.com\/workshop\/wp-json\/wp\/v2\/posts\/36\/revisions"}],"predecessor-version":[{"id":288,"href":"https:\/\/blog.hslracing.com\/workshop\/wp-json\/wp\/v2\/posts\/36\/revisions\/288"}],"wp:attachment":[{"href":"https:\/\/blog.hslracing.com\/workshop\/wp-json\/wp\/v2\/media?parent=36"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.hslracing.com\/workshop\/wp-json\/wp\/v2\/categories?post=36"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.hslracing.com\/workshop\/wp-json\/wp\/v2\/tags?post=36"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}