Reverse lead screw on a B2227L

[digiex-chris]

I've got a Craftex (Busy Bee) B2227L that's got a nice geared head, but not a quick change threading gearbox or anything, just the usual changable gear train for threading. Soon I'm going to need to cut a left hand acme thread, so I decided it was time to get going on making this thing move the lead screw the opposite direction.

I couldn't use the methods many people use on the Grizzly lathes, I don't have the space for it and the gearing is setup a little differently. There's a 4:1 reduction inside the headstock to another spindle that's used for the output for the threading gears. This has a nice effect of reducing the error doing metric threads to so small no one cares except if you need an entire foot of thread engagement or are making metric leadscrews or something.

I picked a location for the extra gear so I could use almost any gear in the box as the idler/reverse gear and make it fit allowing me to make reverse threads of anything that's on the chart for my machine.

I needed two bolts, one to pivot the bracket on, and one to lock the pivoting. I popped the top open and measured the thickenss of the headstock casting, and found I had 0.375" to work with on the edge where I wouldn't break into the oil filled cavity inside. That let me use M6 bolts for everything and match the machine's metric fasteners. It's a funny machine, imperial leadscrews and threading capability, and metric fasteners holding it together.

Here's a photo of me milling the curved slot on my lathe using an old Taig headstock mounted to an angle plate. Worked pretty well, though it would have been a lot better if I had a faceplate to clamp the work to instead. Dear Santa, please send me a rotary table for Christmas. There's 3 holes in the bracket (well, 2 holes and a slot). The bottom hole I screwed a post into and made a bushing to go between the gear and the post.

And here's the finished result.

 

[Jtrain]

I have the same Craftex 2227L lathe. Very interesting set up. I'll look into doing the same or similar. Thanks

 

[Brian Rupnow]

I have that same lathe, and although I have found it to be a fairly good lathe, unfortunately the lowest speed is 150 RPM. I have never had good results with cutting threads, and after discussion with quite a few machinists far more advanced than myself, I have reached the conclusion that it simply doesn't have a slow enough speed. I have thought different times about doing something to the gear train to slow it down by another 50 percent, but have never got around to doing it.---Brian

 

[digiex-chris]

I was thinking the same thing. Big diameter cast iron stuff, it goes too fast! I might see if I can squeeze a larger top pulley in there, or maybe some kind of back gear gearbox off of that top shaft and drive it with a shorter belt, or something. Starting to cramp that shroud though, might have to make a new one and go more vertical with a pulley/gearbox. Since I'm not doing production work I'm ok with changing gears with a wrench, maybe I'll just do the same and make a plate hold a pair of gears and change which pulley is being driven to choose normal or back gear...

 

[digiex-chris]

btw, that's the 55 tooth gear but almost any work except that larger idler gears restrict the size of the gear that can engage it. The littler gears work just fine too, they just tuck under the driving gear more than being on the side. I might remove the loctite from the post and make it removable so I can still use it with smaller driving gears. If anyone wants those dimensions, let me know and i'll measure it up. I eyeballed it to make it. I got away without removing the shroud and drilling through it. I half-ass located the edge by poking a small hole at the top and bottom of the headstock from the headstock side.

 

[Dunc1]

Another B227L'er. Terrific mod! Would love to have the dimensioned drawings.

Ref the low-end speed. I have been scheming (well, dreaming more like) with the idea of replacing the motor with a jack-shaft to carry the existing motor pulley. I would remount the motor behind the lathe and add a belt drive reduction. So far, just thinking. I looked (drooled is more like it) at the Myford site before it disappeared. I gather that the Myford in Back-gear could go to 30 rpm or perhaps a bit less. On that basis, 3:1 reduction should be ball-park. What would be a suitable means to transfer the power/torque from the motor to the jackshaft -single pulley & belt (larger cross-section), link belt, double pulley & belt, or... ?

 

[velocette]

Hi digiex-chris
Love your Idea pinched it and fabricated one and it works great.

"I was thinking the same thing. Big diameter cast iron stuff, it goes too fast! I might see if I can squeeze a larger top pulley in there, or maybe some kind of back gear gearbox off of that top shaft and drive it with a shorter belt, or something."

Can I make an attempt to return the favour

this is the way I reduced the speed on a very similar lathe to give Normal speed 115 Middle 87.5 and low @ 57.5 approximately

See pics attached

Motor pulley steps are 30 mm 40 mm 50 mm Gearbox 95 mm 85 mm 75 mm

Eric

 

[digiex-chris]

That's a perfect solution! There's enough space for that in the enclosure. It'd be a double V per step, but that's no problem. I was thinking about this last night, and thought belts were the way to go, because if you went gears, you'd need a third gear to reverse it back to normal rotation.

edit: err duh, could totally change to a different belt type if it was more convenient. It's pre-coffee right now.
edit 2: you wouldn't need another gear, just flip the forward and reverse directions on the switch.

 

[digiex-chris]

Ok, here we go. It at least gives you the heights of the gear and such. Replace whatever threads with whatever you like. The boss location used to be about 0.300 to the right, but I found it wouldn't quite engage properly with any size idler gear. Moving it to the left solved that, and seems to engage with every combination that I've tried (55t and smaller). I made a keyed carrier for the gear so that no wear would result on that gear from rotating. I also have an oil hole cross drilled in the boss (part A) and length wise out the front so I can oil the thing without removing it.

(see attached)

p.s. I've also done a cam-lock for the tailstock and am in the process of doing a cam-lock for the carriage, I'll draw that all up too next time I take them apart for cleaning. And if you find you're stripping the T-bolts holding the compound down, make new ones out of drill rod and harden/tempter them to a blue color, no more of that going on! That's one thing I'm disappointed with, the soft soft fasteners that it came with.

View attachment Leadscrew Reverse B2227L.pdf