1953 Leblond Regal 17" crossfeed screw

[Mgdoug3]

I contacted Leblond about getting a new crossfeed nut and screw and it was around $2400. That's more than I'm willing to pay and I can use my second lathe to make a new screw and my mill to make the nut. I can still make accurate parts but I want to get rid of the excessive backlash.

Does anyone have a picture of the cross feed screw? I do have a taper attachment. Before I disassemble everything, I would like to have the metal on hand so my lathe will only be down for a couple of days. I can measure the thread size and pitch but I need to know what the largest diameter is to order the appropriate diameter and length.

I also had an idea of cutting out the old threads and buying the correct thread size and pitch or just machining that section. I could then drill and tap sections of the old screw and cut threads on the new section. This should make sure when I screw it all together that it's centered and straight. I would weld it together and it'll never come apart. My thought process doing this is not having to machine the entire shaft and worrying about copying the old shaft perfectly. Is this a viable option?

 

[matthewsx]

I see you checked. $2400, wow.

 

[FOMOGO]

You have the original right?, and the specs should be available on line. Put a pair of calipers on it and order the closest available size up from that, or a quarter inch larger, if you want to practice some. Same for the length. Better to have it all new, as your old one is probably worn in more than one place, and if you bore and thread your own nut, you can get the fit just so. Might as well just do it right the first time, instead of having to do it twice, or be unhappy with the result. In the end it's just more experience doing what your interested in. Even if you have to do it twice it will be knowledge well earned. Mike

 

[Mgdoug3]

My materials came in from McMaster Carr today. I bought a 3/4-8 LH Acme tap, 954 bronze flat stock, 3 foot of precision acme thread and also a solid bar of 3/4" 1144. I may try to graft a new section of thread in and make a completely new shaft at a later date on my bigger lathe. I'm worried my smaller lathe isn't rigid enough to cut 15" of acme thread.

I got my nut made today. The 954 bronze is tougher material than I thought. I cut it a little longer and then milled it to size. I drilled and tapped the 5/8-18 hole first. Next I center drilled where I thought the original hole for the crossfeed should be and moved over to my lathe. I used a dead center to line up the center drill in my 4 jaw. Drilled a 1/4" hole and then stepped up to a 1/2.

I noticed the drill bit was wondering a little so I used my boring bar next. I was worried a 5/8 drill bit wouldn't leave me enough to bore to 0.641" for the tap. I used my calipers until I was close but I didn't grab my inside micrometer quick enough. I thought my calipers measured large for ID but I was wrong. Accidentally overshot by about 0.005" but that might be OK. The tap is only suppose to be used in 1.5" of bronze and my piece is 1.9". I started the tap in the lathe to make sure I had it started straight then went to my bench vise and used a lot of cutting oil.

I moved the nut around in the jaws again using a dead center and machined the boss to 1" but missed my mark by 0.0005. Close enough in my book. Gave it a small chamfer and took it to the mill to put a radius on the bottom side like the original.

I test fit it on the precision rod and it's a great fit. I can't feel any play and nut moves freely. It's not 100% like the old nut but i believe I have all the critical areas the same. I'm hoping I have time tomorrow to make the crossfeed screw and put the lathe back to work.

 

[matthewsx]

Nice work

 

[Mgdoug3]

I finished up the shaft today. One end of the shaft was 0.556" with a 1/8" keyway. I figured I could turn down one end of the new Acme thread and cut the keyway on my mill. I chose this route so I only had to graft one section in instead of two hoping to minimize runout. I machined a bushing to go on the back side of my headstock to help keep the shaft flopping when trying to dial it in on my 4 jaw chuck.

I decided to cut 3/8-24 stud on the Acme thread and a corresponding hole on the old shaft to splice it together with 680 Loctite. I measured several times before I cut the shafts. I don't have anything more precise than a tape measure for anything over a foot but the tape measure shows that it's the same total length.

Installed the screw and checked my backlash. I went from almost 0.100" to 0.005". If I machined the threads I probably could have improved that even more but I am very happy with the outcome. I like that when I reverse the dial now my cross slide moves almost immediately. My lathe does make me money on the side so I wanted to make sure it's in good shape. Thanks for the help and tricks to get my lathe back into shape.

 

[matthewsx]

Awesome fix and ~$2300 saved to boot

 

[FOMOGO]

Nice job. Up and running is a good thing. Mike