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Kevinb71
12-18-2012, 01:57 PM
I have a model 1875 10" Logan lathe. I am rebuilding this machine. So far i have rebuilt the headstock, the quick change box and cleaned up the carriage. I now have found that the tailstock quill is cracked along the MT2 taper and the threads in the quill and the threads on the leadscrew are shot. I have been thinking that I could just build a new one(logan wants over $300) and a leadscrew. My question is this. Speedy Metals lists turned, ground and polished 1 1/8" shaft in three materials. 4140, 1045 and 1144 stressproof. They all are listed as 1 1/8" +.000/-001. The 4140 seems from their materials info to be fairly hard. As I will have to drill and bore then turn the taper on the inside for the MT2 I am not sure if this is too hard or not to machine. Which of the three materials would you guys think best? I have not ever turned a taper to say nothing of an internal taper. I will practice on some aluminum first. Any thoughts on this part of the operation?

strokersix
12-18-2012, 02:07 PM
I vote 1144. strong stuff but machines nice

Dr Stan
12-18-2012, 02:19 PM
The 1144 does machine nice, but I'd go with the 4140 for longevity.

To cut the taper get a good #2 MT dead center with a center hole in the large end. Take a piece of scrap about 1/2" or so in diameter and mount it in a drill chuck in the tailstock. Put a #4 or 5 center drill in your 3 jaw chuck or collet and drill a center hole in the piece of scrap. Leave it in the drill chuck once you've cut the center hole.

Mount a piece of round stock in the 3 jaw or collet and turn a 60 degree center. Mount the dead center between centers and use it to dial in your taper. This should get you very close.

When cutting the internal taper use the #2 MT dead center as your gage along with Prussian blue to check your fit.

Once all the lathe work is finished you can cut a shallow slot in which you can bed in a part of a 6" scale so you'll have a scale on your TS.

Kevinb71
12-18-2012, 03:29 PM
Good info Dr. Stan. Thanks
Strokersix I was leaning that way for the machinability, but thought maybe the 4140 would last longer as per Dr Stan.

JCHannum
12-18-2012, 03:30 PM
1144, chances are that the original is made from leaded steel, probably 12L14. 1144 machines beautifully and will outlast you.

Kevinb71
12-18-2012, 03:52 PM
What would be the best material for the new leadscrew?

firbikrhd1
12-18-2012, 07:16 PM
Unless you are dead set on building these things for yourself you might be wise to try to find them used. Some of the Logan parts are interchangeable between various models or can be modified easily to your machine. For example, I bought a QC gearbox for my 820 but the original lead screw wouldn't work. I was able to obtain a very nice one from Sobel Machinery in NJ that fit the QC box but was too long. It was an easy fix to shorten the screw and turn the bearing area at the right end. In another instance i was able to obtain a good tail stock for not too much money. I don't know if Sobel even exists anymore but at the time he was a good source. Ebay is another source for parts. You might even try Search Tempest for an entire machine that could be used for parts.
Another option for the lead screw would be to purchase Acme threaded stock and modify the ends to suit your needs. The gearbox end may require grafting on a portion of the original shaft, for example. Roton sells it buy the foot in many sizes RH & LH thread.

Dr Stan
12-18-2012, 07:41 PM
Another option for the lead screw would be to purchase Acme threaded stock and modify the ends to suit your needs. The gearbox end may require grafting on a portion of the original shaft, for example. Roton sells it buy the foot in many sizes RH & LH thread.

Ditto on the screw. Lots of places offer it and the screw for the tail stock does not need the precision of the lead screw.

Duffy
12-18-2012, 07:44 PM
Plaza Machinery usually lists a fair selection of Logan parts. To make a leadscrew, try a length of acme screw stock from Keystone Threaded Products.