G0602 tailstock driving me nuts

[dewbane]

I use the tailstock on my g0602 constantly, and it has been driving me nuts for the longest time.

One of the more common things people do is just leave a 17mm wrench on the tailstock at all times. I've read lots of posts in various places, talking about how "it only takes half a turn" to snug the thing down.

Yeah, not so much. The casting for the bed on my particular lathe is machined quite satisfactorily on the top surface, but the bottom surface is just some raw, ragged nonsense. Imagine taking a cast iron surface plate and bashing it against a hard edge at a weird angle until one end of it finally snaps off.

If I start with the tailstock snugged down at the far right, and start moving toward the left, here's how it goes: Loosen about 1/2 a turn, I'm good to slide for some distance. Thunk. The clampy thing on the bottom has now collided with the ragged edge on the bottom. To get over the hump, I have to loosen the nut, maybe half, maybe a whole turn. I continue sliding for some distance. Thunk. By the time I get up near the headstock, I have had to back the thing off maybe three full turns.

So, the leave a wrench on it approach is never going to be satisfactory. The other main approach people take is to build a cam lock lever activated deal to actuate the clampy thing. I have mixed feelings about this approach. I have a cam-actuated tailstock on my wood lathe, and it's not difficult to cam it right over until it's completely loose. I've read some threads here and there warning about that problem on a metal lathe, and I feel like my problem is greatly compounded by the irregular clamping surface. My chances of building a cam with just the right offset seem rather slim.

So I'm just kind of scratching my head, trying to figure out what move to make on this one. I suppose I could disassemble the lathe, and try to machine the bottom of the casting. I mean, it's not like I spent hours and hours fine tuning it, and dialing the twist out of it or anything. Heaves to Betsy no! This shining example of the output of the People's Republic of Perfection couldn't have ever had any such flaws!

I'm sort of halfway talking myself into machining some weird tapered blocks to bolt on the underside, so at least the top is a lot closer to being parallel to the bottom than it is now. That seems possibly doable, but I'd have to flip this "benchtop" machine on its back, and the last time I had to move this "benchtop" machine anywhere, I ended up renting a Bobcat.


Anyway, it was a rough day, and I zoned out and lost my train of thought. It happens. Discuss!

 

[Nutfarmer]

Any chance of reworking the under side ways? I had to on my 6300 Clausing when the bed was re ground. Even a milled surface would be better than a raw casting. Let us know how it turns out.

 

[dewbane]

Any chance of reworking the under side ways? I had to on my 6300 Clausing when the bed was re ground. Even a milled surface would be better than a raw casting. Let us know how it turns out.

In a perfect world, I guess I would have about six strong, strapping sons who could just man handle the thing onto my little g0704's table, and hold it up while I hog off some material with a perfectly balanced carbide endmill that would never shatter. I would never have to worry about anything again, because from that point forward, a miniature leprechaun riding on a flying unicorn would rush to the rescue to solve all of my machining challenges with rainbow magic.

In the real world, what? If I had a good idea, I would have just done that, and bragged about it.

Sigh.

 

[Nutfarmer]

I used a grinder and a file. I agree that in a perfect world we could send it off and have it ground. None of us live in a perfect world ,but I have seen some members do some fantastic work with less than optimal equipment. I am amazed at the work sometimes.

 

[Mitch Alsup]

An Idea:: on the clamping side of the clamping thingie are two little ledges (one on either side). If you could affix (glue) some abrasive {Paper, stone, file} onto those ledges, you can then use the tailstock and push/pull/run it up and down the ways, slowly tightening the clamp, and have the abrasive on those little ledges slowly remove material that is preventing smooth operation.

 

[jwmelvin]

My g0602 has the same issue. I’d also like to fix it. I do have an engine hoist to lift things. I’m thinking that lifting the tail stock end would allow access to find the high points of the clamping surface and ease them a bit with a grinder and/or file.

 

[RJSakowski]

I use the tailstock on my g0602 constantly, and it has been driving me nuts for the longest time.

One of the more common things people do is just leave a 17mm wrench on the tailstock at all times. I've read lots of posts in various places, talking about how "it only takes half a turn" to snug the thing down.

Yeah, not so much. The casting for the bed on my particular lathe is machined quite satisfactorily on the top surface, but the bottom surface is just some raw, ragged nonsense. Imagine taking a cast iron surface plate and bashing it against a hard edge at a weird angle until one end of it finally snaps off.

If I start with the tailstock snugged down at the far right, and start moving toward the left, here's how it goes: Loosen about 1/2 a turn, I'm good to slide for some distance. Thunk. The clampy thing on the bottom has now collided with the ragged edge on the bottom. To get over the hump, I have to loosen the nut, maybe half, maybe a whole turn. I continue sliding for some distance. Thunk. By the time I get up near the headstock, I have had to back the thing off maybe three full turns.

So, the leave a wrench on it approach is never going to be satisfactory. The other main approach people take is to build a cam lock lever activated deal to actuate the clampy thing. I have mixed feelings about this approach. I have a cam-actuated tailstock on my wood lathe, and it's not difficult to cam it right over until it's completely loose. I've read some threads here and there warning about that problem on a metal lathe, and I feel like my problem is greatly compounded by the irregular clamping surface. My chances of building a cam with just the right offset seem rather slim.

So I'm just kind of scratching my head, trying to figure out what move to make on this one. I suppose I could disassemble the lathe, and try to machine the bottom of the casting. I mean, it's not like I spent hours and hours fine tuning it, and dialing the twist out of it or anything. Heaves to Betsy no! This shining example of the output of the People's Republic of Perfection couldn't have ever had any such flaws!

I'm sort of halfway talking myself into machining some weird tapered blocks to bolt on the underside, so at least the top is a lot closer to being parallel to the bottom than it is now. That seems possibly doable, but I'd have to flip this "benchtop" machine on its back, and the last time I had to move this "benchtop" machine anywhere, I ended up renting a Bobcat.

View attachment 338490
Anyway, it was a rough day, and I zoned out and lost my train of thought. It happens. Discuss!

I have the same issue with my 602. I suspect that the top side and under side of the ways were milled into the casting and in grinding the top side, the parallelism was lost.

I measured the thickness of the front side of the ways and got a minimum thickness of .6282" at the far left and a maximum thickness of .6444" in the center for a difference of .0162".

Rather than trying to machine the underside of the bed, consider changing the clamping bolt. The OEM bolt is a 3.5" M12-1.75mm bolt. This amounts to ..0689"/turn. A 1/2-13 bolt has a pitch of .0769". In turning the nut from full lock to loose within the confines of the tailstock casting allows around a 170º rotation and 170/360 x .0689 =.0325". On my lathe, I required about another 1/12th turn or 30º. 200/360 x .0689" = .0383". Substituting a 1/2-13 bolt, 170/360x.0769 = .0373" which was enough for the cross slide to freely traverse the ways.

If the 1/2-13 bolt doesn't provide enough range, a 1/2-12 Whitworth bolt has a pitch of .0833". 170/360x.0833 = .0393" which should be more than enough. Finding a 3-1/2" 1/2-12 Whitworth bolt may be a bit challenging but we have a lathe, right? 1/2-12 Whitworth nuts are available on eBay.

If I were making a bolt, I would make it with an oversized rectangular head. When I looked at the bearing surface of the clamping plate, I noticed quite a bit of wear due to the small contact area of the bolt head. Making a rectangular head of 3/4 x 1" would vastly improve the bearing surface. For those going with the 1/2-13 UNC bolt, McMaster Carr sells square head bolts.

 

[dewbane]

I used a grinder and a file. I agree that in a perfect world we could send it off and have it ground. None of us live in a perfect world ,but I have seen some members do some fantastic work with less than optimal equipment. I am amazed at the work sometimes.

A miniature leprechaun riding in on a flying unicorn. I have to laugh at myself. I hope you took that in the silly spirit I intended, because it sounds a little snarky to me now. Anyway, as far as less than optimal equipment, I'm pretty happy with my g0602 and g0704 on the whole. There are limits, but they're pretty high, really.

An Idea:: on the clamping side of the clamping thingie are two little ledges (one on either side). If you could affix (glue) some abrasive {Paper, stone, file} onto those ledges, you can then use the tailstock and push/pull/run it up and down the ways...

That idea has merit, but that would be more for fine tuning after I work out some way to hog off about 0.100" from the high side. As far as that goes, when I think about it, this casting is already a little funky. There are some discolored areas out toward the far right that refuse to clean up with stones, because they're places where material contracted after it was machined, leaving low spots. If I create new relief in this wonky casting that clearly has weird stresses in it already, I might really screw things up. Hmmm. Better would be devising a way to add material to the low spots.

Rather than trying to machine the underside of the bed, consider changing the clamping bolt.

That is a line of thought I hadn't considered at all. More travel per turn could indeed make the problem go away. As screwy as the casting is on the bottom, I'm not having problems turning tapers or drilling holes off axis or anything. The clamping mechanism absorbs the error well enough. I just need a clamp that moves more for less wrench travel. If a normal thread won't give me the travel I need, I can just make one up from scratch, like a 1/2"-4 McIntyre thread or something just stupid. Intriguing. Of course, I haven't gotten around to learning how to thread yet.

Well thanks for all the ideas, guys.

 

[hman]

I definitely agree that you have a problem on your hands. This sounds incredibly bad for a name brand lathe! How long have you owned it? I'm wondering if Grizzly is letting their quality control slip?!?!

No idea how to approach the roughness problem. Just a caution ... Most cam locks I've had experience with have had pretty limited travel. I don't know if it's practical to build one with enough range to handle a surface as rough as you describe yours to be. If it has too much range, it may not have the leverage needed to hold securely. Best wishes solving your dilemma.

 

[dewbane]

If the 1/2-13 bolt doesn't provide enough range, a 1/2-12 Whitworth bolt has a pitch of .0833". 170/360x.0833 = .0393" which should be more than enough.

So I scrounged a 1/2"-13 bolt in my mystery parts box, and doctored it until it met parameters. Good enough for testing purposes. It did offer a negligible improvement, and I'm going to leave it on there and get to work on something else.

After surfing McMaster-Carr for awhile, I settled on 1/2"-10. I picked up a 6" lead screw, a brass nut, and a hex nut for a total of about $30. I plan to machine the nut to fit the slot in the bottom clamp, and Loctite that end of the lead screw into the nut to make my T, then just use the standard hex nut up top. It has a 7/8" head, same as my toolpost, so that will be convenient. If I don't have enough clearance for a nut that big, well, I guess in that case I'll have something to figure out.

I think this will get it. I lose all credibility as a machinist by buying the stuff from McMaster-Carr, but another way of looking at it is that if you like McMaster-Carr as much as I do, I have a duty to do my part to keep them in business, and I am carrying out that duty here. Plus I had to order some oddball drill bits anyway.

PS - I wonder if I'm going to be able to clamp a 1/2"-10 acme screw in a 5C collet. Hmmmmmm. I ordered the shortest length they stocked, which was 2" too long. Cut it off with a bandsaw, and ideally I would like to mount it in the lathe and put a nice round top on it, like my Aloris toolpost. Not really critical, just attractive. I mean if I can't, I'll just have to freehand it into the bandsaw. Do not want to booger up the threads to make the end pretty!!!