Removing Flex in 9x19 Compound Slide Base / Gibs

[November X-ray]

It would be really easy to disassemble the compound slide and measure to ensure the ways are parallel using two pieces of drill rod and while it is apart make sure the gib adjustment screw holes are drilled thru and also check the gib strip for uniformity as well as checking the corners of the ways. There could be a burr or trash, debris, casting sand, whatever that has been trapped somehow. Also while apart it is relatively easy to lap the compound ways, just have plenty of elbow grease ready!

Good Luck!

 

[Richard King]

Yea, those are solid, I replaced them when I built the beefier 4 point ring for it. There is no movement there, there is a few thous of rocking between the actual slide lower half and the upper half (the sliding half.

12bolts,

I initially described it a little wrong by saying the gib set screws where on the bottom half. I have attached a pic for clarity. Note, this is not my lathe or pic, I have just used it for the purpose of drawing on since it would be quicker than taking new photos. The circle is just to note where the movement is and the line drawn is to simulate where the gap appears when rocked (between the two halves). It isn't much, just a few thous, but that is enough to effect the finish.

View attachment 38437

ScrapMetal,

After I shimmed out the lathe again and ensured it was level I just tested it, and it still creates a taper. I've ran my dial indicator (anchored to the cross-slide) down a straight bar that has been centered using a 4 jaw chuck and centered at both the chuck end and holds center at the unsupported end while manually turning (left off tail stock just to see for sure) and it test dial holds 0 while moving the carriage up and down the stock which should mean the tool should run even up and down the stock and cut even. However, it still gives me a taper on this longer stock. I normally turn small parts on this thing and now that I'm using a longer piece of stock that requires some precision I'm just noticing it and I'm baffled how the taper could be introduced. I'm going to test again with the lathe running and make sure centripetal force isn't throwing the end out a bit causing the taper but I suspect it will be true because it is being supported.

Sorry, this sounds like I'm trying to throw a bunch of issues into a single thread, but I swear this isn't my first rodeo but I've only recently started using this 9x19 lathe for more stuff now and trying to clean it up.

I was in Oklahoma last winter where a company had a old Summit lathe and it had a taper in shafting. The frist thing we did was level / align the bed. It is more important to have the machine aligned then level. A level is used to check alignment. When someone says the machine has to be level I say "How do you level a slant bed lathe level or how do you level a lathe on an ship? They are not leveled. They are aligned.

The machine in OK was worn and cut a taper so I twisted the bed a little to compensate for wear. You would be better off micing the shaft and moving the tailstock in or out to get the taper out. There are a number of things you could be dealing with. You say you indicated the side of the tailstock quill, have you checked the top? make sure you move the cross-slide in and out to get top dead center of the quill and see which way it is pointing, when they are new they point up about .0005" so as the dirt gets under the front of the bottom slide it wears and as it wears it wears better.

The one guy who suggested dismantling it and cleaning, stoning it, checking it with drill rod I would suggest using hard dowel pins and the the size can be the ones that the OD is touching as close to the center of dovetail as possible.
If you have a precision parallel (I would use a scraped straightedge) also check the flatness of the ways or if you have a surface plate set the dismantled compound base on the plate and use a surface gage to see if the flat ways are straight. I hate to insult you Grizzly owners, but they are not built real precision.
The one guy who said his compound uses pins under the set screws may have found your issue.

Another thing..your level should be at least .0005" per 12" per line precision. Many times I will set my level on the top of the compound (front to back) and shim under the bottom when the saddle is cranked as close to the chuck as possible. shim the level so it reads level there near the chuck. then slowly crank the saddle to the right and watch the bubble. It should stay the same, if not the bed is twisted. The level is following the tool bit path. As i said your bed maybe worn and you will have to find a happy medium and put an small twist in the bed to compensate for wear. Getting it perfect may not be possible. As I said, I find talking on the phone is easier to explain. Maybe we can have a Skype multiple group forum sometime, I am not sure that is possible, but sounds fun. ha ha. Have fun , Richard

 

[Metalmann]

Yes, I've told guys the same thing:

" When someone says the machine has to be level I say "How do you level a slant bed lathe level or how do you level a lathe on an ship? They are not leveled. They are aligned."


I remember aligning some of the old dinosaurs, and having to tell the shop owner that. Some of them didn't believe me at first. Then, later; I'd hear the owners telling one of the other employees about it.

But, speaking of Grizzlys; my lathe came out of the crate cutting .0005 on a 18" test bar I made. That plenty tight enough for today's standards. I still have it on one of the skids it came with, because I like it a little taller than most folks. After moving it from two different shops, it's still holding .0005 in 12". I haven't tweaked it in over 3 years. I'm sure it's not as tight as it was, originally. Someday, I'll make up another test bar. Lost the original in the last move.

Speaking of gibs, the Grizzly mill table would not snug up. After checking it out by removing the table, adjusting the nut, resetting the backlash to .001; I found out the X gib was way too long from the factory. Had to cut off a little over 1" to make it fit.

Grizzs definitely need adjustments and tweaked; but they hold tolerance just as good as the more expensive machines, if you know what you're doing.