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I am making a spider nut to support long thin stock through the headstock spindle of my lathe. The spindle nut is made of CRS and is 1.25 long with an internal bore of 25.5mm. The threads only need to go approximately 5/8” deep.I made a spring loaded center to decrease the chance of thread misalignment. The spring loaded center will be chucked in the tailstock while the spider nut will be aligned with a 4 jaw chuck.Since I have never threaded anything this large before, I would like some advice to decrease the chance of making a costly mistake.A M27 x 1.5 hand tap (plug) costs $40.00 on ebay or 53.00 from enco. Based on the cost, I know these are not top notch hand taps. I do not currently have a boring bar for internal threading. The manual of my lathe states it is capable of threading metric 1.5mm threads. However, I have never performed any internal threading before. In addition, I’ve read there are issues requiring reversing without opening the split nut on the lead screw.It sounds like hand tapping might be the best route. But.......I may be wrong. Might be best (and cheaper) to pay someone else to do it.I would appreciate some professional advice as to what is the best route to take. Thanks! Attached Images
Reply:I vote for threading with a boring bar. It takes a bit of getting used to but is much easier if you thread the full length of the nut and in to the space behind. You can then move your bit away with the cross slide and power it back out. Return your cross slide to its original position and advance the compound. the compound will be turned toward you and set at the 30 degree threading angle ( 29.5 deg if you use that method on outside threads.) Holding that round collar while you try and cut a thread with a tap would be tough. I see it spinning in the jaws.
Reply:i would just chuck it up in a lathe,chuck a tap guide in the drill chuck, a T-handle and some muscle... i would use a good tapping oil/fluid... i like ez-foamy, tap-magic, anchor lube works good in softer material. not familiar with the brand of taps your using, if they are decent it shouldnt be to bad.. just back out and clear the chips.. problem you might run into is collapsing/crushing the nut when you clamp down on it in the lathe.. you probably would have been better off tapping them at the same time as one piece, then sawing them and then facing them off or parting them off..Last edited by brucer; 07-10-2011 at 09:20 PM.tackleexperts.comwww.necessityjigs.comhttps://www.facebook.com/groups/mach...dingequipment/
Reply:Make sure to not drop the half nut out of engagement until your thread is complete, and checked with :-) your gauge/template/whatever. You will have a Dickens of a time picking up the lead again. Internal boring bar is by far your best option. Cut a practice piece, it's not too hard to get used to. Get/buy/make a boring bar. It will be a far better investment than a $50 tap which you will, likely, never use again.
Reply:Originally Posted by brucerproblem you might run into is collapsing/crushing the nut when you clamp down on it in the lathe..
Reply:If you can skinny maybe a 1/4" thread relief on top of the 5/8" threaded length doing the threading with a bar and single point would be the way to go (I assume you have an inch lead screw machine).If you have enough thread length on the spindle I'd thread both those pieces and saw one and use it as a jam nut to lock the spyder nut.Matt
Reply:Originally Posted by joedirt1966The lathe chuck will not crush the nut. The wall of the spindle nut is .421" thick (27/64+") The internal bore is approximately 1" (25.5mm).
Reply:Originally Posted by Matt_MaguireIf you can skinny maybe a 1/4" thread relief on top of the 5/8" threaded length doing the threading with a bar and single point would be the way to go (I assume you have an inch lead screw machine).If you have enough thread length on the spindle I'd thread both those pieces and saw one and use it as a jam nut to lock the spyder nut.Matt
Reply:If you have a lathe and time then by all means learn to single point internal threads. The wall is fairly thick and should not deform when chucked. Single pointing threads does not require that much force to secure the part. You can build your own boring bar if money is a problem. The boring bar may be ugly but it works.Russell Attached Images
Reply:I made a boring bar a few weeks back to do 1" internal threads. Very similar to the pic Russell posted. Cut the threads almost complete, then ran the tap through them. Got the best of both worlds....My name's not Jim....
Reply:I've been pricing boring bars with indexable inserts for internal threading for the last couple of hours. WOW! The internal threading carbide inserts are pricey!A homemade boring tool may be the next project.Thanks to all for your advice!
Reply:Interesting...Some friends and I were talking about making some custom nuts, 40mm x 1.5... we have single pointed external threads, but never internal threads... didn't know if you could do it.
Reply:Here is a link to a section on my website. It describes my attempt to create an ER collet chuck. The pertinent portion is about 1/4 way down where I describe the internal threading. I finally created my own internal boring bar. Worked well, too. I couldn't use the compound for this project, & had to do "full contact" threading. I don't recommend that method; however, sometimes you just gotta make do.Best to you,Jerry in Anchoragehttp://www.akpilot.net/ER-32%20Colle...t%20Chuck.html
Reply:What type of chuck are you running? I have a six jaw, self scrolling that I really like in case I am ever worried about collapsing something. It really distributes the load.
Reply:Muskt,Thanks for the link. Originally Posted by jmtebbensWhat type of chuck are you running? I have a six jaw, self scrolling that I really like in case I am ever worried about collapsing something. It really distributes the load.
Reply:Thanks to all for the input. Went with Boostinjdm's suggestion. Single point internal thread chased by tap. Worked like a charm. Attached Images |
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发表于 2021-8-31 22:28:05