Carriage lock screw - Any reason not to

I've got a 1440 Chinese lathe from Precision Mathews. Its not the cats
meow, but its still better than any other lathe I have. Often when
taking facing cuts or parting cuts I like to lock the carriage. The
bolt for that is a recessed socket head screw. It works ok, but it
seems I am always looking around for the hex key when I want to release
it and move the tool away from the stock. Unless I am holding it in my
hand the whole time it always takes me a couple seconds longer than I
would like to locate where I set it down.
I've been thinking about about making a taller head replacement bolt,
drilling it for a small vise handle. I've got a bit of 4140QT shaft on
hand and a bit of 1/4" 1144 rod. Making it should be no big deal. Any
reason why I shouldn't. I'd keep it as low as possible, and make the
handle about half the difference in length between a short arm and a
long arm hex key that size.
Speaking of such I'd also like to lock the cross slide from time to
time. There isn't a lock on it, but it does have a tapered gibb that's
easily adjustable with a screw at each end. Usually I just keep the
gibb adjusted a little bit tighter than is perfectly comfortable to spin
the hand wheel, but on heavy roughing cuts it can still back off on
longer pieces of stock. I wind up standing there with my hand on the
hand wheel and my eye on the DRO the whole time. Is that just the best
way to do it?
Reply to
Bob La Londe
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I bought several 'vintage' box wrenches for square-headed bolts and made replacements for missing lock and clamp screws on my 1965 South Bend to fit them. There's been no problem with the square head carriage lock.
When not trying to match a style and period I make as many fasteners as possible on home made machinery fit the same pocketable gear wrench, normally 9/16" for 3/8" bolt heads.
The SB has a Threading Stop which is a bar that locks into the dovetail and limits in or outfeed, so the cross slide can be retracted to quickly move the carriage and then run back against the stop for the cut. It serves the same function you are looking for without messing with the gib adjustment.
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Reply to
Jim Wilkins
Another idea is to make it such that your chuck key fits it...
I bought a cheap set of HF metric ratchet wrenches that have reverse on them:
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I leave the 12mm on/in the tail stock locking bolt. One more idea :)
Reply to
Leon Fisk
Another idea is to make it such that your chuck key fits it...
**** Not a bad idea, and I do have a location specifically for the chuck key(s), but which chuck key depends on which chuck I have on the lathe.
I bought a cheap set of HF metric ratchet wrenches that have reverse on them:
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I leave the 12mm on/in the tail stock locking bolt. One more idea :)
**** This lathe has its own lever locking system for the tail stock. I have to adjust it once in a while, btut not tools required to lock it in place, or to adjust the lock. I do leave a 3/4 box end wrench ont eh tailstock clamping bolt on my smaller 8.5x 18 lathe.
Reply to
Bob La Londe
If you have only two lathe chucks -- make a wrench with two ends, and the tommy-bar in the middle.
Cheap and not capable of much torque -- but quite likely sufficient for your specified needs.
Enjoy, DoN.
Reply to
DoN. Nichols
DoN, if you see the tail-stock it makes a lot more sense:
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They just give you a bolt head to secure the tail-stock. You can't quite release it with one grab using a standard wrench. So you have fiddle with the wrench on/off the head to both loosen and tighten the tail-stock.
I also added a spring underneath between the wedging nut and the stock. Helps to release it a bit sooner.
What it really needs is the cam-lock mod but I'm lazy...
Reply to
Leon Fisk
You might try facing the bolt head and nut bearing surfaces square with the shank and threads to see if that makes the tailstock lock and release with less rotation.
My lathe's tailstock was refitted with a 1/2-13 bolt that clamps tight (enough) or fully releases in 1/8 of a turn. I found an old wrench like this and made a hex nut+washer that is 0.80" across the flats to fit it.
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Reply to
Jim Wilkins
I'm sure that wouldn't make it any worse but the main problem is part #1021 rocks around, sloppy below the bed. So if you loosen the bolt slightly (actually the nut I see) and then try to move the tailstock it jams up by going a little cockeyed. The spring I put above #1021 helped by keeping some downward pressure on it.
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For what I do with it the ratchet wrench and spring combo works good enough :)
Reply to
Leon Fisk
On my lathe that part is a hunk of steel some trade school student hogged out to replace the missing original. I filed and block-sanded it until the end mill marks were the same degree of barely visible all over.
I've fitted two surfaces I couldn't machine, a 5HP gas engine and its welding-warped mounting plate on my log splitter, by marking the high spot contacts by pulling sandpaper through and grinding the scratches off with an angle grinder, then filing as the fit improved. I stopped when a feeler gauge 0.003" thick (IIRC) wouldn't go into the open corner, because the offset weight of the engine was interfering with a delicate feel.
Reply to
Jim Wilkins
Yeah, it's amazing what you can do with simple hand tools with a bit of training, thought and wana-get-it-done attitude :)
A guide pin or two for that part on my lathe would help a lot. Or so I think it would. If I was moving it often I would probably work on it some more. The real solution for slick operation would be Steve's mod:
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or something similar.
There are only a few days a year that I can comfortably work on it or with it. Most of the time I end up taking care of stuff that just won't wait any longer...
Reply to
Leon Fisk
Here's something similar that requires no change to the tailstock. I made adjustable cam lock clamps for a sheetmetal brake using this type of fixture bolt:
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The cam is 1.250" drill rod, cut about 3x the thickness of the bolt eye long, and cross-drilled 0.050" off center for the pivot pin. The bolt eye fits into a slot milled across the center of the cam, with enough D-shaped thickness left below the slot, connecting the round sides, to drill and tap for the operating handle.
On the brake the handle can swing all the way around to run the bolt threads in or out for coarse adjustment to sheetmetal thickness. Since it would have limited rotation on the tailstock you might need a thumb nut underneath to adjust the tension. It can be tightened either by rocking the handle down toward the thicker side of the cam or rotating it to screw the bolt tighter, or both.
The feed clutch cam on my South Bend is a very similar design.
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Reply to
Jim Wilkins
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Indeed it makes sense.
I wish that the nut for my 12x24" Clausing were that accessible. It is in a cavity only accessible from the back of the tailstock.
The original design was a lever and cam to pull up the nut, but that is not with mine (lost before I got the tailstock) and no longer stocked by Clausing last I asked. So, I have a slip-on hex wrench made for a Logan, with a long hex nut, with the center of the hex turned to a cylinder so I can pull the wrench up a bit and slip it to the next teeth in the socket. (No, I can't get to the back easily enough to switch the ratchet direction on your inexpensive wrenches. Maybe I can make a remote for the reverse switch and then use your wrench type for the task.
Pretty much everything else in the lathe uses a single square head which fits the supplied wrench. (The other end of the wrench accesses the nuts holding the compound adjustment at need.)
For yours, what about making something to fit in the other end which is hex of the right size for the wrench and has an extension also hex (or square if so needed) to fit the carriage lock -- and if necessary, Loctite it into the hex socket in the wrench. That way, one wrench for both jobs.
Great idea.
Someday ... :-)
Enjoy, DoN.
Reply to
DoN. Nichols
I suspected that it was a whole lot more complicated and a generic drop in wouldn't be a simple fix. Or you would have done it already :)
It annoyed me when I first saw how it was made. But frankly I just don't use it enough for it to be a problem. I now have Your's, Jim's and my own ideas on how it could be made better if it becomes cumbersome in the future...
Reply to
Leon Fisk

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