The Stars Have Been In Alignment For Me This Week. Just Got My First Lathe, A D/r 11x36, 25-100

[thenrie]

Yes, I am aware of that. I don't think the shrinkage would be significant or critical in a follow or steady rest, as long as there was sufficient material left in the base to machine it to the proper height. Every thing else should shrink equally, leaving everything centered. It would really be nice if I could get the price of the raw castings down under about $75 apiece. With the additional machining and work I would suspect the completed part would come in under $150 easily, if you make the rest of the parts yourself and don't count your labor, even if you have some of the machine work done locally. In my book that's a lot better than paying antique collectible prices upwards of $325 apiece!

Actually, this is starting to sound like a fun project to me. I've got to get some other things squared away first, but I may start seriously considering this route, once I get my decks cleared a little.

 

[astjp2]

When you get to Provo, I will lend you anything in my shop. I am getting run too thin with school and work and my shop to add something to my plate right now. I want to rebuild my machines, and we will be having a scraping class sometime soon in Utah with Bebop (Don), he is friends with Forrest and I think learned from him. Once I get my shop cleared out and some benches in place, it should work for a weekend class. I want to learn so I can use my skills to go through several other of my machines. Get the Connley book. It will explain a lot, from lessons learned. Tim

http://www.amazon.com/gp/product/9996967085/ref=oh_details_o02_s00_i00?ie=UTF8&psc=1

 

[thenrie]

Thanks for that, Tim. I'll surely take you up on it. In fact, once I get out that way, you may wish you hadn't mentioned it.:LOL:

It was a little cold and windy out here today. Went out to the workshop, built my first fire of the year in the old cast iron stove and piddled around with the lathe. I cleaned all the end gears and levers. Looks a lot better now. Forgot to snap a picture. I'll post one tomorrow. I think I'll tear the carriage down tomorrow and take a good look at it.

I've got my eye out right now for a 3hp 3-phase motor to make myself an RPC. Decided to go that route, so I won't have to buy another VFD when I get my mill...whenever that is. No luck so far finding anyone to build me a lead screw. I have a couple more places to check down in Richmond.

Ordered a couple books as primers for me. Ordered Metal Lathe for Home Machinists, by Harold Hall, and Shop Reference for Students and Apprentices, by Christopher McCauley. They had good reviews from the perspective of a rank beginner. I'll get some of the other recommended books as I get a little more familiar with terminology and processes.

How difficult is it to machine a keyway the full length of a long lead screw by cutting the keyway in sections on a mill with a short bed? Can a long keyway be cut on a lathe?

 

[Pacer]

I can offer a few comments on casting and doing a lead screw...

I have been casting in aluminum for many years (Dave Gingerys books) and have poured a follow and a steady for a SB with marginal success, mainly/mostly because we didnt have an original to copy from. Getting an original and either using it directly for a pattern or copying it in wood (likely need to do a split pattern). Casting is a lot more than getting some metal hot and pouring it into some sand, making up a complicated pattern can take hours - or days, then you need a furnace that will get to the proper temperature, and the sand is much more than a couple bags of play sand from H depot, etc. But, aside from all the gloomy talk, casting is another area of metalworking that can be a real hoot.

Lead screw - I have made a couple of them up ant the split nut also. There are several sources for the bare Acme rod - I got mine from
http://roton.com/Screw.aspx?line=Acme (Note they have a min order - $60)
They also have the nuts .
Mcmaster Carr also has Acme...
Hopefully you dont have an odd thread count and they have what you need - some of the thread counts they dont have.

On cutting the key way youll almost have to have a means to loosen the acme and reposition it further down the table to continue the key way cut while maintaining the line of cut, devise a system of "keys" to key it to the table to do this (Unless youve got one of those loooong tables) I laid the rod in the 5/8" T slot on the mill table, devising a "key" system in order to be able to loosen it to move further down and continue the cut. With some creative thinking you can get a lead screw made.

 

[astjp2]

I will just send the screw to a shop that has a 6+' table and let them do it. I cant do it as cheap as I can get it done for. Tim

I can offer a few comments on casting and doing a lead screw...

I have been casting in aluminum for many years (Dave Gingerys books) and have poured a follow and a steady for a SB with marginal success, mainly/mostly because we didnt have an original to copy from. Getting an original and either using it directly for a pattern or copying it in wood (likely need to do a split pattern). Casting is a lot more than getting some metal hot and pouring it into some sand, making up a complicated pattern can take hours - or days, then you need a furnace that will get to the proper temperature, and the sand is much more than a couple bags of play sand from H depot, etc. But, aside from all the gloomy talk, casting is another area of metalworking that can be a real hoot.

Lead screw - I have made a couple of them up ant the split nut also. There are several sources for the bare Acme rod - I got mine from
http://roton.com/Screw.aspx?line=Acme (Note they have a min order - $60)
They also have the nuts .
Mcmaster Carr also has Acme...
Hopefully you dont have an odd thread count and they have what you need - some of the thread counts they dont have.

On cutting the key way youll almost have to have a means to loosen the acme and reposition it further down the table to continue the key way cut while maintaining the line of cut, devise a system of "keys" to key it to the table to do this (Unless youve got one of those loooong tables) I laid the rod in the 5/8" T slot on the mill table, devising a "key" system in order to be able to loosen it to move further down and continue the cut. With some creative thinking you can get a lead screw made.

 

[thenrie]

Where are you going to have yours done, Tim? I asked a shop here that has the capability and he told me it would be in the "thousands" (of dollars) to have a lead screw made, even after I mentioned just milling a keyway in a stock threaded rod. Then he simply said he really didn't want to get into the leadscrew making business and told me to get a used one on eBay. Of course, after an answer like that, I wouldn't have this shop sweep my floor. I'm still looking around.

 

[thenrie]

Before and after pics of my end gears. Looks better.



I'm working on the carriage now. Not unexpected, but disappointing, I'm finding a lot of wear in certain gears and shafts and it looks like I'll be replacing a few parts. Incidentally, it looks like re-tapping the half-nuts won't be that much of a problem. At least from a rank amateur, eternal optimist point of view. I'll be looking around for a used tap and see what I come up with. Maybe after I get mine done, I can pass the tap around on a "you-break-it-you-bought-it" basis.

Also found my cross-slide screw pretty worn, as well as the feed nut. I a'm considering chasing the threads to make them all even, then making the nut out of Acetal to remove all the backlash. I figure if it doesn't work out, I haven't lost anything but time. I can simply replace the screw and make a new brass nut.

I'll try to post more pics tomorrow of the carriage parts.

 

[astjp2]

Acetal will wear too fast, just use the bronze and tap it. It will last for years with some good oil and some TLC. We have several local shops that will cut the slot, set up time is what is most of the money, if we take several raw screws in, it should be simple for us to then turn down the ends to fit each lathe's specific needs.

Was this the tap you were looking at? http://www.ebay.com/itm/3-4-X-8-NA2...ultDomain_0&hash=item19d71ccc1a#ht_404wt_1133 Tim

 

[thenrie]

That's one of them. There are several listed in the same price range. However, I looked at the screw last night and if I'm not mistaken, it's a right-hand thread, rather than left. Correct me if I'm wrong.

There are several articles I have read about making the feed nuts from Acetal that indicate it does not wear faster than the bronze and that with it you can reduce backlash to literally zero. They also indicate the strength is sufficient. The threads are formed on the plastic by controlled heating of the screw and compressing the plastic around the screw to form perfect threads. The nut is then removed and the threads cleaned up with a home-made tap (a flat ground on the end of a piece of screw), and voila! A nut with no backlash. This method has been used on several lathes in the size range of our 11s with very satisfactory results. Thought I'd give it a shot and see how it works, since my cross slide feed screw is pretty worn, just making a new bronze nut would still leave plenty of backlash. However, if I chucked the screw in a lathe and turned the threads all even, I could make a plastic nut by the method above and have a custom nut for the "custom" threads in the screw. That should not affect the accuracy of the dial on the handwheel, since threads would be the same, just thinner. If it doesn't work out satisfactorily, well, no loss, I would have had to replace the screw and nut anyway. Worth a try. It might be a good solution while I'm waiting for the right feed screw to come along, at the least.

See this thread: http://www.hobby-machinist.com/showthread.php/13041-Acetal-Delrin-cross-slide-lead-screw-nut

and this one: http://bbs.homeshopmachinist.net/th...-leadscrew-nuts-the-easy-way?highlight=acetal

 

[thenrie]

Woops! I see I already posted those links and had that discussion on your thread.

Here are a couple shots of the some of the apron parts off my lathe:



I don't know the proper names of the gears, but I'm sure you'll know what they are. The carriage drive gear is very worn and needs replacement. It is a pressed-in fit in the larger diameter gear, which is in good shape. The half-nuts are worn out. I believe I should be able to repair those, though, but clamping them tight in the bracket, and running a tap through to re-cut the threads. The clutch gear (brass one) is also very worn and needs to be replaced. Seems like I saw a post somewhere where somebody had made some of these and was offering them for sale. Anybody know who it was?

There are several bushings that need replacement as well. Looks like the bushings can be bought off the shelf for less than what I could make them for. There are also a couple 1/2" shafts that show some wear that it wouldn't hurt to replace.

I was looking at my cross slide screw. It looks pretty straight forward, as far as replacing it with an off-the-shelf section of screw, until you look at the end toward the handwheel. It is drilled out for about 6" and has two keys broached into the inside diameter for the first 1-1/4". That looks like it would be a challenge, especially for a novice like myself.