View Full Version : Attn: Oldtiffie, here's the spindle spider

02-02-2010, 05:57 PM
Well, I just finished fixing my screwup. I made a sleeve, threaded it with the left hand 45mm x1.5mm thread, bored the spider out and pressed the sleeve in with a .0005" interference and high temp, high pressure locktite.

Threading setup for removing and testing. Thread is about a class 3.


Spider with sleeve pressed in and bore trued up.


Spider in the spindle, cover open to show it better.


02-02-2010, 08:29 PM
Lot easier to dial in a 4 point spider..... :)


No thousandths harmed... It does not rotate or move in spindle once tightened down. Everything is indicated before use anyway...

02-02-2010, 10:24 PM
Nice job and a very nice recovery Carl.


After years of leveling tribrachs on surveying instruments, the "three-screw" is my preference too.

I am a bit ambivalent about the "four".

But if you wish, there is no reason why you can't make it a "12" and have 3 and 4 to cover most stuff as well as a 6 and some "spares" to cover most of the "irregular" stuff.

Following on from what you said, and the previous thread on our spider etc. I am well "into" a post on thread measurement (internal, external, class of thread ("fit") and clearance ("back-lash")) with one and 3 "wires" and thread micrometers etc. It needs a lot of work yet - but its on its way.

As you are very well "into" and "up with" threads, I'd appreciate your comments on it. Its weeks away yet.

02-02-2010, 11:26 PM
I am very interested in what you come up with. Measuring OD is no problem but measuring an ID thread is always a bugger and reverse figuring the internal dimensions is tricky for me.

Several times I had to make a part that screwed on a thread at a customers shop. the male thread part could not be removed and brought to the shop. I had to go and measure the thread with wires to make an exact duplicate and I mean exact. Some stuff we did required a class 2 or 3 fit of the female thread.

For that I would make a stub test thread from the wire measurements because the thread on the machine would be worn or not the expected class fit it was when new. With care I could make a replacement part with the proper fit they wanted.

I feel real confident cutting an internal thread if I have the proper thread cut on a stub shaft to test with.

Even cutting the thread on this tool and getting a snug thread would have been impossible had I not been able to remove the part and test the thread in the spindle. I removed it four times to get the fit right and was able to index it perfectly each time easily.

I love threading, just watching the metal curl off and a thread appear on the work is fun each time I do it. As I said, one of the first things I did when I bought my first lathe was cut a thread. It was like magic and I cut thread after thread after thread until I thought I better start learning some other things about machining. It's more like a job now but I still love cutting threads.

02-03-2010, 01:33 AM

I will try to show that only one wire is needed and will work just - almost? -as well as three as regards measuring/copying an existing thread as well as getting the right "class of thread/fit" using the Machinery's Handbook formula (same as the one used in LMS or CDCO "three-wire" sets and the Class of Thread tables (similar to the standard "Class of Fit" tables)).

Thread "slop" - aka "backlash" is one of the keys.

The reason I am saying this early is that I was hugely impressed with the way you stuck to and went about the thread for the spider and that you have the "what it takes" to see that I am - and to keep me - "on track".

I am rather hoping that Glenn Wegman and a few others of like ilk will run checks and offer advice as well.

Its going to be "different" to what many "was taught" but I'm pretty sure I am on the right track.

If this works, there are a lot of people who will benefit - even if only to see that there is "another way" - which is just a re-hash of the "old way".

There will will be "thous" and a few "tenths" - but no microns.

So - thanks in advance as I really do appreciate it as its all too easy to make a mistake on paper too!!