Ok, so back to the old question of SS screws. Seems to be difficult to find 8-40 flat head screws that I like. So my question is...if you run a 8-32 tap through say a Tib frame for the 114H( which is a 8-40 thread) do you risk screwing up the frame? Do you get a good fit? Aren't the screw dia. The same on an 8-40 and a 8-32.? Your just changing the pitch, right? Or do I need to tap to the next largest size?
Bob
I think as long as the walls arent to thin and the screw is lightly greased and fits well you will be fine
Be very careful.
First establish exactly what thread is in the Tib frame.
Are you sure it is not 8-36 UNF as 8-40 is a non standard size?
Also, the diameter is the same HOWEVER your going from 32 tpi to 40tpi which is a FINER thread and your screw may very well not hold and skip a thread ore two. Wait till you get more POSITIVE feed back. Keta/Lee is one our resident machinist whom I consult with on details such as this.
Leo
It should be ok.
8-32 major diameter .1631" minor diameter .1248"
8-36 major diameter .1632" minor diameter .1291"
major .1632-.1631=.0001 loss
minor .1291-.1248=.0043 gain
8-32 thread contact .0383"
8-36 thread contact .0341"
The re-taped thread contact will be .0332"
http://www.engineersedge.com/screw_threads_chart.htm (http://www.engineersedge.com/screw_threads_chart.htm)
SEE WHAT I MEAN? Thanx Lee for the link!!
Leo
So Lee & Leo, I should be alright if I tap out a existing 8-40 thread with a 8-32. The Penn 114H side plate screws are a 8-40 correct? If I tap them out to an 8-32 I believe there are many more options of SS screws that can be used?
Quote from: BMITCH on November 15, 2013, 07:43:00 PM
The Penn 114H side plate screws are a 8-40 correct?
Yes 8-40,which is a non standard size and hard to source other than from Penn.
Quote from: Irish Jigger on November 16, 2013, 12:02:36 AM
Quote from: BMITCH on November 15, 2013, 07:43:00 PM
The Penn 114H side plate screws are a 8-40 correct?
Yes 8-40,which is a non standard size and hard to source other than from Penn.
Tom, my point exactly! So if I tap out the 8-40 to 8-32 do you think there is enough "meat" to be able to bear down on the side plate screws??
Or maybe go up a size to a 10-32 and make the holes through the side plate and rings larger? I really don't like the penn screws. Not a cost issue more an aesthetics issue.
Bob
Bob Im not your guy for this question, just the referral to Keta/Lee
Leo
Bob,I would not cross thread the holes by tapping them 8-32 and would stick with the original 8-40 chromed brass screws.
You could try tapping a 114H post 8-32 and see how well the screw holds.
Quote from: Irish Jigger on November 16, 2013, 12:03:22 PM
Bob, I would stick with the original 8-40 chromed brass screws.
Same here.
Bob, run an 8-32 die/die nut down an 8-40 screw and see what the threads look like before contemplating tapping the Tib frame. ;)
Quote from: Irish Jigger on November 16, 2013, 03:38:38 PM
Bob, run an 8-32 die/die nut down an 8-40 screw and see what the threads look like before contemplating tapping the Tib frame. ;)
X2. I've successfully ran a course tap in a fine thread hole in steel but they were much larger.
Just a thought
http://www.noblefix.com/PDF/Helicoil/HeliCoil-Professional-Kit.pdf
I have used helicoils on carbs, chainsaws & a few other things. Have never fitted ones this small before though. Hope you have good eyes. I wouldn't recommend running a coarse tap into a fine thread of the same diameter.
Rgds
Mark
Helicoils are fantastic, of course. But I wonder if there is a concern of galvanic action between the stainless and aluminum in salt water?
Ron
The helicoils I've done before( only 5mm) this is small. I wouldn't trust them over time as Ron said.
Bob, I did tap a frame out to 8-32. It holds fine. I would like to caution you the tap needs to be straight. Preferably you would use a taper then a plug and then a bottom tap. I would try it out on something like an old post to satisfy its to your liking. Send me your address and I'll send you a post already tapped out.
Bob
Looking at a Heli-Coil flyer, they make phosphor bronze inserts for salt water applications. These and stainless screws would be the absolute correct answer.
Ron