Checking runout

That's really the point of a griptru - once set to a particular size, they have good repeatability, so can be used in production for gripping same size parts. Otherwise I believe that they are no more accurate than a standard chuck. Super precision chucks have better run out over the whole range. I have my SC chucks fitted on a backplate with a slightly small register that gives about 10 thou adjustment - a poor man's griptru.

Rod

Bought the lathe with the chuck so want to use everything I can to keep the costs down as funds are non-existent at the mo, so if I can get the accuracy of a four jaw by using the Griptru then that's a bonus and will just have to bite the bullet when it comes to turning square stock later on, John

I cannot remember when I last used my Grip tru chuck, sat on the shelf unused for at least the last10 years.

Maybe one day when I have a lot of larger repetition parts it will be put to use, in the meantime ER series collets suffice for smaller round parts.

Gents having read with interest this thread I couldn't help add my bit I have a super 7 with a griptru Dad bought it new in about 1976 I "inherited it " when he upgraded to a 254, neither he nor I have ever had any problems with this setup and only observe there seems to be little mention of " check your machine is level" it is the most important part of any lathe setup procedure cheers

I never realised that Tubal Cain was American! The video was very interesting but confused me a little by talking about FOUR adjusting screws when my Grip-Tru has only 3.

He's an imposter . The "real" Tubal Cain, the well respected writer for ME (and EIM, dare I mention it?) was Tom Walshaw, a Brit.

Rod

Already checked level Mike, this was more a chuck issue which is now pretty spot on once I knew how to adjust it! Think I will have to get a four jaw sometime soon though as I work thru Harold Halls test pieces, John

Thanks Rod, I also didn't know that the real Tubal Cain was Tom Walshaw; I really must get out more!

My main Griptrue chick is about 30 years old possibly more, the new one is about 20 years old. I have hardly used the new one. I have the outside jaws on the new one and standard jaws on the old one. I just change chucks instead of switching out the jaws. One thing that I thought of when I 1st got the lathe as it came with this chuck, was to adjust the chuck with the least amount of pressure to hold the part true. I think they can be damaged by over tightening the adjuster taper screws. When ever I need to hold something very tight, I use the 4 jaw chuck for that. I rarely need the 4 jaw.Over the range the old chuck is upto 0.05mm tir out. But if zeroed in on a size it is still better than 0.01mm every time. I have not taken it apart for a service yet, but will do after reading the info and articles. Here is a picture of modifying a 6x15 bearing outer race to become a magneto bearing. The bearing is a very light press fit into the fixture with castor oil to allow the over size part to assemble. There is an extractor screw to take out the bearing shell. It was set up in the Griptrue because if the inner race did not run true to the outer race, I could adjust it to be true, then I could turn away the part of the bearing to the race center line. It happened with this bearing that no adjust was required.

Latest update, chuck all adjusted stock bar running about 1 thou out and turned a 6" long by 1" dia test bar and this has 0.0005 runout of parallel over the 6" so am pretty pleased with that. First attempt at grinding my own HSS tools in 30 years and got pretty good finish too, let's hope all the lathe adventures go as well! John

Am I right that no one has mentioned the point made by GHT about Griptru adjustment? He devoted nearly two pages to the subject in his MEs Workshop Manual, the central (!) point being that he counselled easing off and re-tightening the body screws before and after adjustment.

I had a look at my chuck, it has belleville type washers under the cap screws holding the chuck together.

What you say does make sense about the body screws. I have never has any issues with my chuck though.

Glad to hear the OP has found the cure to getting it running well again.

Hi ega, yes I read a write up by Tubal Cain in his book on work holding so I did crack the chuck/backplate bolts before adjusting and then tightened up after, John

Sorry to be a pedant but Tubal Cain is in the Bible: he's the first metalworker.

Hence the inverted commas. Irony (see what I did there?) doesn't seem to work very well over the intenet

I believe he gets one brief mention in Genesis but Ray Winstone managed to make a meal out of him in the film Noah. Mackay managed to construct a whole poem around him **LINK**

Rod

Mea Culpa Rod. It seems that it's not only our American friends who don't get irony!

I think the Mackay of the poem must also be the author of one of my favourite books - "Extraordinary Popular Delusions and the Madness of Crowds". I like the works of the "real" Tubal Cain too.

Cheers,

Dave

Dave,

That Mackay book, I think it must be the same bloke, looks fascinating - just my sort of thing. Now downloaded to my Kindle.

Thanks,

Rod

.

The latest incarnation of Tubal Cain has just today posted this video that relates to the OP's question.