Thread Bar Project, nothing is going right and I need help

Very good Mr. Smith, looking forward to seeing more of your work but I can't for the life of me think of what machine that thread bar goes on.
 
This may seem like a silly question but is the diameter of the cut in the thread the spec (ie: 3/4" x 24tpi with final product larger by the cut depth) or does it specify the O.D. of the final product?
 
not sure what you're trying to say. it's 3/4 x 11 tpi i believe it was. it specifies the OD of the final product and measure with 3 wire is calculated and larger than 3/4 by a little bit. that is how we measure the thread depth.
 
Thanks Contact, I think you've got the gist of what I'm trying to understand. Using an S.A.E. 3/4" x 11 tpi bolt as the example, does the 3/4" represents the material that's left? How deep is the cut into the material in this example?
 
netfences said:
Thanks Contact, I think you've got the gist of what I'm trying to understand. Using an S.A.E. 3/4" x 11 tpi bolt as the example, does the 3/4" represents the material that's left? How deep is the cut into the material in this example?
Click to expand...

OK. yes 3/4" is the actually size of the thread. this means that the top of the thread is approx. 3/4". as far as how deep this one is, I'd say like .145 thousandths deep. I calculated it using the formula I was taught but it was always like .060 thousandths bigger for some reason. Either way it worked out.
 
netfences said:
Thanks Contact, I think you've got the gist of what I'm trying to understand. Using an S.A.E. 3/4" x 11 tpi bolt as the example, does the 3/4" represents the material that's left? How deep is the cut into the material in this example?
Click to expand...

The "3/4" part indicates the nominal major diameter of the thread; the part measures about or slightly less than 3/4" in diameter. The depth of cut required to cut the threads is typically calculated with a formula, of which there are several. One such formula is: 0.750 / TPI. In this instance, 0.750 / 11 = 0.0682", so you would incrementally feed in with your compound a total of 0.0682" to create a full depth thread.

All such calculations are estimates and you are wise to check the thread depth well before reaching the calculated depth by using either the three wire method or a screw thread micrometer. The readings obtained with either of these methods is compared to a table that lists the tolerances for a given thread. These tolerances vary with the fit you are going for, a 2b or 3b and so on. Once your thread falls within the tolerances you choose, you are at the proper depth of cut and that thread should take any nut that is made to the same standards.

Hope this is clear. If not, shout out.
 
Not that I'm any kind of a "precision" threader,try a follower rest ask in your shop.
I fear fear your shop doesn't really have a Teacher ; one of the most necessary
skills lies in keeping up hope and pride in his students. .........BLJHB.
 
A 6" vise is overkill for a RF45 style mill. A 4" is more appropiate for that size mill & IMO 5" max. I have a 5" GMT vise on my PM45 & it's slightly too big. Not enough Y axis travel to make use of the 5" full capacity. Better to save your money rather than getting something too big & most importantly the weight. I take my vise of the table quite often, a 6" is still light enough for me to be carried by hand but I'm glad I have a 5". I also have a 4" vise as well. I prefer the 5" though.

But those GMT 6" Premium vises are pretty nice. I'd love to have one but don't need one on my current mill. But if you plan on upgrading to a full size knee mill in the future than the 6" will be perfect.


Here's what the 5" looks like on my mill.
Img_1921.jpg


I couldn't even complete this cut without my bellows & DRO scale getting in the way. Not enough Y travel & the 5" vise is not even maxed out.
Img_7597_zpscb8b5dd7.jpg


Here's what a 6" vise looks like on another PM45 (gt40's)
View attachment 253544
 
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