Single Point Threading Tool Angle Accuracy

[projectnut]

In fifty years of working with nuts and bolts I can count on one hand the number of times that I have had one fail in service. Most cases of snapped fasteners have been due to rusting in place. In fact, it is a common practice for me to remove rusted on nuts on bolts to tighten rather than loosen to deliberately shear the bolt. It takes a surprising amount of torque to do so.

Aside from fasteners like head bolts and the like, the vast majority of fastener situations we encounter will never come close to testing the design limits of a fastener class.

While there is some concern about fastener failure, most times I use grade 5 bolts for an extra margin of safety and peace of mind. Most prints for hoisting lifting and equipment suspended overhead call for grade 5 or higher bolts. I follow the callout on the prints whenever there is one. For the difference in price between a grade 2 and grade 5 bolt I stock mainly grade 5.

I do have some grade 2's but find most these days are made off shore and often times thread quality is not the greatest. I seriously wonder if most could pass the marked design limit. I have popped the heads off more than a few 5/16 and 3/8 hex head bolts without too much effort. I'm sure my weinie 70+ year old arm isn't putting anywhere near 4,400 lbs. of pressure on the bolt using a 10" long box end wrench.

 

[RJSakowski]

Actually, an Acme thread is a totally different kettle of fish. Its purpose is to deliver very high dynamic thrust loads as compared to static loads of a fastener. The 29º angle results in a 14.5º flank angle which is what high work load gears use.

As Joe pointed out in the video, if the angle on the right hand cutting edge is less than the compound angle and you are using the compound to advance the tool, you will cut steps. The 29.5º will ensure that doesn't happen. 29º or 28º will also work, Extreme advancement angles such as straight in via the cross feed can cause issues such as chatter, particularly on smaller, less rigid lathes.

To ensure setting up a 29.5º, I made a gage to set that angle reproducibly, and effortlessly.

29.5 Deg. Angle Tool For Lathe

A 29.5 degree angle is most likely the most used angle set on the compound on a lathe. The Grizzly G0602 lathe has a difficult to read dial with 2-1/2 degree graduations. My solution was to make a gage that would provide easy and accurate setting of this important angle. I made mine from a...

www.hobby-machinist.com

Without the gage, I would set a smaller angle to allow for the inaccuracies of the 602 protractor.

 

[RJSakowski]

Early on, I bought grade 2 in bulk. Grade 9 bolts weren't readily available at the farm supply store and were more than twice the price. Nowadays, they are available in bulk at little more than the cost of grade 2. Even grade 8 bolts are fairly common. I just finished disassembling a New Holland 66 bailer and the fasteners used thoughout were grade 2.

I tend to buy and use grade 5 except for critical applications where I will use grade 8.

 

[devils4ever]

Yes, I wasn't talking about the compound angle, but the actual lathe bit angle to the work.

I always try to get it as accurate as I can, but I'm not sure if I'm off a bit sometimes? It LOOKS okay, but I could be off a few tenths of a degree or more. Does it matter?

 

[682bear]

A few tenths of a degree won't really matter... 'as close as you can' will be good enough unless you are working for NASA... and might be good enough then...

-Bear