Pinging John Stevenson - help !

[nheng]

John,

UPDATE: the chuck is going back so this is informational / entertainment

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I read an old post of yours in RCM regarding a Pratt Burnerd chuck which you sent back. I bought one without digging a little deeper here.

It's a 6" Set-Rite which is supposed to be built in the UK. I zero'ed it on a 1/2" ground rod and it held 0.0002" over the rod length (about 3" protrusion). Then went to 1" and it was still within 0.001", re-zeroed and it's around 0.001" over 8" (some repeat problems though, even with careful reseating, rotating, etc.)

Then all hell broke loose. At 3/8", it's off by 0.002" and at 1/4", over 0.003"

The grind on the jaws appears a bit rough and I suspect that once the rod diameter falls below that of the grinding wheel, the "grabbing" surfaces have some sort of problem.

What was your experience with PBA? My darned Bison (another machine) is within 0.001" on just about anything!

added - also, John, the jaws are badly scratched on the sides in a feeble attempt to deburr the end edges. The chuck has a "catalog number" which no one recognizes (data sheet, distributor, web). No speed limit on chuck. No model number. Nothing except the Pratt stuck on (no more rivets) nameplate. The pinion looks like it could be Asian. The pinion feels like it has interference against the scroll (clunk-clunk). Looking head on at the ground teeth, the are trapezoidal in shape instead of clean rectangles like the Bison. They are either off the center line or are correcting the raw jaw being off center.

The Set-rite is supposed to be made in the UK but I have my doubts now on that and on the materials (although the body looks pretty good).

Thanks, Den


[This message has been edited by nheng (edited 09-28-2004).]

[This message has been edited by nheng (edited 09-28-2004).]

[nheng]

<refreshing the ping for John>

[John Stevenson]

Den,
Not sure what's happening at Pratt Burnerd.
I was told their grip tru was staying in the Uk and the bread and butter chucks were being sourced out to TOS.
The one that J&L sent me looked as if it had been kicked from Poland or wherever.
It has inserts bashed into grooves in the chuck for the sides to work on and they were rough.
Most of my chucks are TOS chucks and are good.
I have one big 12" Bison chuck but I have had jaw problems with that and they won't help out at all. That one has just been replaced with a TOS and this also now has the inserted sliders but of a decent quality.

I sent the Pratt back and had they send me a TOS. I ordered the Pratt as I was told to get a decent chuck and money wasn't a deciding issue, The TOS that replaced it was far better and a lot cheaper.

Last month I bought 3 6" TOS chucks from J&L. These also had the inserts to the jaw sliders but quality was good.

My take on this is that either Pratt were being ripped off or they had spec'd a low end model or could have been teething problems whilst they felt their feet with a new supplier.

John S.

[nheng]

Thanks for coming back on this one as I'd still like to know what's going on.

My biggest problem is having a new chuck which does not meet their own spec, has had coarse paper or stone taken to the jaws, etc. etc. and a $780 price tag.

Have you seen recent Rohm (Hi-tru) products?

I may stick go Bison but although the Bison I have is accurate, it is quite loose (pinion, jaw slides) and will only get looser unless they've come up with a way for them to tighten with age

The only things I've seen tighten with age are the wrong things

[speedy]

Den, maybe an eastern country has gone and named a town UK. Do you remember Japanese products (way back when they were begining their industrial expansion)that were labeled made in USA, yeah , they went and named a town/industrial area USA; that is the story I was told.Maybe Pratt Burnerd only package in the UK these days. It seems to me that far too many companies now build down to a price and compromise quality; it`s a damn shame. Give me old iron any day.

cheers, Ken