Buttress Thread Cutting Tool, Would Like To Borrow...

Richard White (richardsrelics)

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I am curious if anyone has a thread cutting tool for the Buttress thread? I have a project forthcoming that will need that particular thread and spending $500 for a 10 pack of inserts is a bit out of my league. If someone has an extra insert and would be willing to part with it I would gladly be willing to buy just one.

Thanks
 
Richard,

I deal with hundred's of different Buttress thread forms in my design work I do for a living. Is this a standard ANSI Buttress thread form as shown in the Machinery's Hand book? If so, what is the thread pitch? Are you cutting external or internal? What kind of tool holding do you want threading tools to fit? I do have a few inserts on hand, but I need to know this information to see if any of them will match up.

Ken
 
External and pitch is 14 tpi. And as for which one, I would have to get my book out to look at which one is closest to matching up..As for tool holding, I have at this point the original tool post holder for my Logan 820. I will have to sell a boat motor(s) to get the dough to get a good tool post holder..
 
Can you provide the flank angles and root width of the thread profile? And which direction it will be cut from. Ie- load bearing flank direction vs non-load bearing flank? Probably have to grind something, which I could do.
 
The item I am wanting to machine is a 60+ year old seal removal tool for outboard motors. So all I have and it belongs top someone else is one of those tools. I took it to a local shop with an optical comparitor,(sp) and at that point we identified it as a Buttress thread but which one exactly is not known. It would almost be easier to talk on the phone, but I cant fairly ask you to grind a cutter. I could do that, although it would not be perfect it probably would work. That being said, the American Standard Buttress would probably work. If I had a way to send you a scratching I would be better able to describe it, since I have not threaded on a lathe in over 20 years, my nomenclature is probably so far off, I would more than likely give a you a tire tread size...LOL. Trick is I will have to thread on a taper, so that really throws a wrench in the gears...LOL But picture 15 degree included angle, length of the threads is about .575 or so with the small end of the taper around 1.1 od and the large end around 1.23

Now for which way the threads face. Orient the small end on the right side, and large on the left... doing external threads of this profile the pressure flank angle would, by the Machinery's Handbook, be about 7 degrees and I need it on the right side of the thread. I do not know which edition MHndbook you have, I have 2 choices, 15th and 26th, my 17th edition is at work...Does this make sense???
Here is a VERY crude sketch, hope this helps.

Crude thread drawing.jpg


Thanks for your help

Richard
 
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Thank you for posting more information. The ANSI Buttress thread form has not changed since it's beginning that I'm aware of. Just very minor things that would not affect form, fit, or function. So it should not matter on which MH you use. I would suggest hand grinding a threading tool since the thread is not being mated to another thread in this case. It's just being used as an "easy out" type of thread for extracting a seal as you have mentioned.
I hope you have a taper attachment that will handle that steep of an angle. I think as long as it has some sort of taper to the thread, it should work. Sounds like a cool project to tackle. I don't have any threading tools ground up for a Buttress thread that fine of a pitch. I have some Top Notch inserts that I believe are ground with a 45 deg angle on one side and 0 deg or perpendicular on the other that may work. It would require a top notch holder to hold the insert.
As I said, I believe your best bet is to grind a tool. Let us know how you make out on cutting the thread.
Ken
 
The taper attachment I have been working on will get me +/- 20 degrees so more than enough. I have prints, or will have a complete set to turn loose for ANYONE that wants to add one of these to their lathe. Mine does not attach to the way but rather the actual bed and is movable so that it can be utilized on either end of the bed... I do not know the cost to make it, but surely less than $1200+ from the factory..lol Even with the prints, there will be some tweaking depending on it is attached to the lathe and it is easy enough to be modified to attach to the ways should that be the way the individual wants to go. and if you think the buttress thread for this particular tool is wild , you should see the thread they used for the prop shaft seal,, LOL, Here is the thread, just gotta throw it in here. I believe it is also Buttress, but it is more like 8 tpi:
prop shaft seal tool.jpg



Many thanks for your help

Regards

Richard
 
That thread is definitely special. You could cut it as a square thread first, then come back and chamfer the one flank to give it the look as shown. Probably has a sharp pointy crest to the thread.
 
how do they cut those threads that just end like that without having any kind of groove to finish in? Are they cut or ground in a single action with the tool being withdrawn from the cut at the end? Just curious.
 
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