29.5 Deg. Angle Tool For Lathe

Is this off setting the cutting tool tip to the axis needed if one uses a coolant to take the heat & friction out of the thread cutting ?
IE.
When using indexable pre ground TC tips
 
David,
The compound would be set to the 29.5º and the tool holder 90º to the axis.
The compound set to 29.5º instead of 30º isn't terribly important on small threads but is helpful on deeper threads, some set it to 30º and feed straight in, mine is set to 29.5º and the compound is used for feeding for all threading.

I bet there are plenty of examples on YouTube showing the set up to clarify if needed.

Ken
 
That looks beautiful!!!!

I'm no expert, but I wonder if an angle block is really needed unless your compass is missing or way off. The big thing is making sure you are at exactly 30° or less. 29.5° gets you close without having to worry about going over 30° if the protractor on your compound isn't exact or too small to see. Some use 29°, some use 29.5°, while some try to nail 30°, so it probably don't matter that much as long as you stay under 30°. I use 29.5° and my last cut is always a small plunge cut.

If I were going to make an angled gauge block to sweep with a indicator to set my compound I'm wondering it if would try to make it something like 29.9° since I'm checking it so accurately.

Chris
 
Once you are satisfied with your set angle put a scribe mark on the compound and the compound base in some conspicuous place, doesn't have to be in or on the degreed area, next time all you have to do is align the scribe marks and you're done with that, a real time saver.

Ken
 
Necroposting this because this morning I had a thought of making a 29º angle block to use up against the compound. Using that and a dial indicator I would dial in the compound. However, since I already have 30º angle blocks I'm wondering about this.....

Using a 3" long 30º angle block affixed to the vertical side of the compound; using a DI to get the 30º vertex end away about 0.0227" by rotating compound counter-clockwise. Using a sine bar I figure 3" length piece at 30º is 1.50" height. A 29.5º setting is 1.4773" (rounded) height. So 1.50" - 1.4773"= 0.0227".

Would this get me a 29.5º compound setting? Am I off my rocker and laying on the ground? o_O Forgive the crude drawing but wanted to show you what I'm talking about:

mine (Phone).jpg

To the OP, sorry for hijacking your thread here.
 
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Splat said:
Necroposting this because this morning I had a thought of making a 29º angle block to use up against the compound. Using that and a dial indicator I would dial in the compound. However, since I already have 30º angle blocks I'm wondering about this.....

Using a 3" long 30º angle block affixed to the vertical side of the compound; using a DI to get the 30º vertex end away about 0.0227" by rotating compound counter-clockwise. Using a sine bar I figure 3" length piece at 30º is 1.50" height. A 29.5º setting is 1.4773" (rounded) height. So 1.50" - 1.4773"= 0.0227".

Would this get me a 29.5º compound setting? Am I off my rocker and laying on the ground? o_O Forgive the crude drawing but wanted to show you what I'm talking about:

View attachment 368494

To the OP, sorry for hijacking your thread here.
Click to expand...
Short answer, yes. The 29.5º angle isn't critical. It is used because it is slightly less than the 30º flank angle of the thread so as the compound is advanced, it make a light shaving cut on flank parallel to the compound advance, cleaning up any step that might have formed from the previous pass.. Any angle less than 30º will work with 0º being equivalent to the advancing in with the cross slide that some prefer. For that matter, you could go up to 30º in the opposite direction which would result in the main cut being on the right. ( I wouldn't recommend it as the cutting pressure would be aiding the feed rather than opposing and any backlash could create a problem.)
 
I should've mentioned I'm familiar with the whole angle debate. I've been using my above method for 30° but lately I eyeball for about 29°. I see my lathe's compound angle scale is off by about 0.3°. A jig or more precise way to measure would be ok with me, hence my question. Was just wondering if my proposed setup would work like I'm thinking. Thanks RJ.
 
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