SPINDLE NOSE TAPS
to cut the
Myford Spindle Nose Thread
However, the company that made the taps for me changed its ordering policies, and it is no longer practical for me to get these taps made.
I have therefore removed much of the info that was on this page about ordering these taps, but I have left in place some of the information, which some who come to this page may find useful.
...If you have a Myford lathe, a tap to cut the spindle nose thread on your lathe would be a very nice thing to have when you want to make a chuck backplate, or any other sort of spindle nose fitting, wouldn't it?
For example, in one of W.R. (Bill) Smith's clockmaking videos, he shows how he mounts a division plate on the chuck register of his Super 7, and anchors it there with a separate smooth circular nut that screws on the spindle nose thread. Very cool.
The spindle nose thread is the same on all Myford Series 7 lathes produced from 1946 right through to the end of 2000. If you own a Myford ML-7, Super 7, Sigma 7, ML7-R, or even a ML-10 or Diamond 10, the spindle nose thread on it will be 1-1/8 x 12 tpi right hand Whitworth. I got the exact specs for this thread, direct from Myfords, and had a tap made to cut the spindle nose thread on my Super 7. The tap maker was at first sceptical of the specs, but I double checked with Myford, and they confirmed that what they had originally told me was correct. So the tap maker made me a tap to that spec. I tested it, and it did a first class job.
(click on image for larger picture)
However, a full form 1-1/8 x 12 tpi right hand Whitworth tap is not a stock, off-the-shelf item. As you may know (and as I found out), having a one-off tap this size made is expensive (think in terms of Cdn$190 or so, plus postage, back about 2000.).
However, by getting several identical taps made at one time, the price came down somewhat, making it a do-able proposition for the average guy.
I had one (or possibly two) batches of Myford spindle nose taps made up, and sold them all. The taps were HSS plug** taps, ground thread, full Whitworth profile, 5-1/2" long overall, with a 0.67" sq. x 7/8" long driving square. They were made with correct geometry for tapping cast iron. I tested mine in aluminum, and it worked fine there too. I never tried to tap a cast iron backplate with it. However, I put it through a Myford catchplate I had which I had used possibly 5 times since new, and the tap took out only the most miniscule amount of fuzz, and some dirt.
The price of these taps was US$96 plus shipping, back when I was able to get these taps made. (Shipping varied depending on the customer's location.)
The following is an afterthought, which may have some validity, but I do
not make any promises about it. I am merely suggesting that it MIGHT be okay...
It is possible that a regular 1-1/8 x 12 tpi right hand Whitworth tap might be ok to use to finish a thread which has been carefully screwcut in a spindle nose fitting a person might be making for a Myford lathe. I always regarded my Myford lathe's spindle nose thread as something to be treated with great care (clean it, wipe it, oil it, etc.), but if you think about it, the thread is there to let you screw the item onto your lathe's spindle nose, but the purpose of the thread itself is only to keep the item attached to the spindle nose. It is the cylindrical part BEHIND the spindle nose thread, and the flat surface behind that, that are critical to the true running of whatever you want to screw onto your lathe's spindle nose. So maybe a fairly ordinary tap might be ok to stick into whatever you are making, and give it a twirl, as Mr. Trump would say, to finish off the thread you have screwcut ALMOST to final form. The Myford factory guys never said anyhing like this to me, and I'm not saying it is the best idea in the world, but maybe - just MAYBE - it would be ok. The place to go, to seek a 1-1/8 x 12 tpi right hand Whitworth plug tap, would be England. So it is entirely possible that some serious googlin' might locate a source in England. It's just an idea to think about.
Added later: I asked my friend Dennis Danich about the foregoing idea. He is a millwright, machinist, and machine tool rebuilder. It was with Dennis that I made my video on examining a used lathe and milling machine (lmv.htm) His reply was basically that a Whitworth thread is a Whitworth thread, so if the tap conforms to the specs in Machinery's Handbook, it should work.
A tap this big requires a pretty fair sized tap wrench to turn it. I expect a lot of guys (including me) would not have a tap wrench big enough to use on it. Big tap wrenches are expensive, and I suspect most basement machinists would not use either the tap or the necessary big tap wrench frequently. When they want such a tap, they want it, but they would probably just as soon not have to tie up $75 or more in a tap wrench for it. So, what to do?
If you go to this page twostories.html of my website, you will soon* find there info which you can order from me on a quick and simple substitute for a big tap wrench, Which is combined with a bunch of other useful information about bending and cutting sheet metal, etc. It'll take you anywhere from 5 to 30 minutes to make this tap wrench substitute, depending on which of my suggestions you follow. Cost to make will be modest, and as just noted, I also tell you several other things for which you can use this same item in your shop. If you want the info, you can send me payment as specified on the above page, and I'll e-mail the info to you the day I get your order.
* I say soon because I need to take some photos and possibly make a couple of drawings, before that document will be ready to send out. GBL June 24, 2017.
Here's something I learned while working on this project:
a Taper Tap has a 7-10 thread lead taper;
a Plug Tap has a 3-5 thread lead taper;
a Bottoming Tap has a 1-2 thread lead taper.
E-mail: GuyLautard46@Gmail.com. Click Here to go to my Home Page..