Checking My Nuts

[EdK]

(02-19-2015, 07:27 PM)Mayhem Wrote: There is a difference between a screw cutting gauge and a screw pitch gauge.  I'd follow Greg's suggestion.

I know that now but evidently the company selling the gauge doesn't. My own fault.

Ed

[Mayhem]

Ahhh - OK, that wasn't clear when I read you original post.

[EdK]

I made the gauges as best as I could and neither fit the thread perfectly but the acme fit it best so I'm going to assume it's an acme thread. I think the next thing to do is to make a trial nut out of aluminum and see how it fits the thread. Any tips on cutting an internal acme thread?

Ed

   

[f350ca]

When you make your cutter, grind the sides till the point is too narrow for 10 tpi, then remove metal from the nose, it needs to be a little narrower then the crest on the male thread your matching. This gives you clearance at the bottom of the female thread.

[EdK]

I assume you cut this as a form tool rather than like a pointed thread where you use the compound to move in to cut on one side of the cutter. Is that correct?

I'll be using the attached chart for the dimensions I need.

Ed


  acme thread spec.pdf (Size: 29.52 KB / Downloads: 4)

[f350ca]

I use the compound Ed, may not be the right way but it works, Set it to 14 1/2 in this case. Then plunge with the cross feed for the last couple of thou.Those numbers will be close but are or an external thread at 29 deg.

[EdK]

Goggling how to cut this thread does show that you can use the compound so I will do it that way. One thing I've run across is that there is mention of taking into account the helix angle of the thread when setting up the tool for cutting. I've not found any information on what that entails though.

Ed

[Vinny]

When I made the new screw for my compound I used the cross slide - couldn't use the compound, there was no screw! It came out perfect anyway.

I watched a Tubal Cain video on cutting an acme thread. He shows how to grind the tool and he used the compound to do it. It was actually a lot easier than I expected (expected = read people on forums saying how hard it was).

[f350ca]

I imagine the references are to grinding the tool to accommodate the helix angle.You need no or negative clearance angle on the right side of the cutter, the helix looks after that.
If we simplify the thread to straight lines a 1inch dia 10 tpi would be angled at 5.7 deg. So the left side needs probably a 10 deg clearance angle, and none on the right. Thats the sides with the tool facing the work ready to cut, opposite if your looking at the tool from the business end, or the other side of the lathe, if its not against a wall, then you'd need a mirror and Im not sure which side would be up then.
No idea how to get a sketch on here to give you a better idea Ed, draw up what you think I mean and I'll tell you if thats what I was thinking, if I can remember that far back.

[EdK]

(02-20-2015, 06:27 PM)f350ca Wrote: I imagine the references are to grinding the tool to accommodate the helix angle.You need no or negative clearance angle on the right side of the cutter, the helix looks after that.
If we simplify the thread to straight lines a 1inch dia 10 tpi would be angled at 5.7 deg. So the left side needs probably a 10 deg clearance angle, and none on the right. Thats the sides with the tool facing the work ready to cut, opposite if your looking at the tool from the business end, or the other side of the lathe, if its not against a wall, then you'd need a mirror and Im not sure which side would be up then.
No idea how to get a sketch on here to give you a better idea Ed, draw up what you think I mean and I'll tell you if thats what I was thinking, if I can remember that far back.

OK, I'll have to digest your post a few times to get it clear in my thick head. Then I'll make a drawing showing what I think you're saying.
By the way, I checked the lead screws and the X is a right hand thread and the Y is a left hand thread so I'll need to grind two bits correct? I've never cut an internal thread before so this is going to be interesting.  

Ed