BTC , dose this stand for Bloody Terrible Chucks?

[Peter Gibbs]

Gentlemen , you to Geoff Two years ago I bought a new Lathe from Hass fitted with a BTC chuck. I really wanted a Pratt Bernhard from the UK (as I had used them for seveal years with excellent service) but was persuaded by the salesman that BTC made great American Chucks.. So reluctantly I agreed.

When the lathe arrived and was installed I was impressed by the visual impression and apparent construction of the chuck , very pissed off with HAAS for sourcing a chuck with a 2.8in bore when the lathe was touted as having a 3 inch spindle...some thing I did not find out about till I had quoted on a job that was to be made from 3" in dia stock .. not BTC fault of course, not very bloody professional of Hass however. ***** over.

IT is a 3 jaw 10 inch chuck six face mounted bolts and the ability to be trued via cross drilled set screws similar to a set true chucks.

My Lathe although 2 years old it has done about 400 hours it is not used in production it is only ever used by me... you will see by the pics it is in as new condition. To date I have only used it to turn odd jobs and nothing that requires multiple operations till last week , I was attempting to make some crank shafts for my vintage BMWs and was having trouble with concentricity when I put some thing back in the lathe.

That led me to investigate a couple of things , and to my amazement the work light revealed that the jaws would not close up along their length, a check revealed that they were 0.3mm (whats that about 11 thou) bell mouthed.. that is the inside edge of the jaws were touching and the end was open point three of a mm.

A close exam of the jaws showed witness marks that would indicate that the jaws were biting harder on the inside than on the end see att pic...

I rang the HAAS agent and he then measured a similar chuck on a new lathe and reported to me that the jaws on that lathe didnt close square either but to a differing degree.. and that if I expected accuracy I should buy some soft jaws... Not good news,...

So as I am in Brisbane Australia I cannot easily send the chuck back to BTC for checking or repairs.. I was going to attempt to grind the jaws insitue* but thought I should ask advise as to the best procedure and or what other checks I could make before attempting such drastic measures..

I have checked that the outer jaws are fully cleaned and seated correctly...

I have NEVER used any extenyion tube on the Tee handle to effect more leverage

I would be greatful for any advise Kind Regards Peter
*

[Caravera]

We use a Haas Tl-2 at our shop.
We have the 10'' chuck on it and we have similar problems as you.
We only use the hard jaws on raw material though for accuracy we always use soft jaws.
They are very easy to produce in house we always make our own jaws.

[Geof]

I don't know if I should respond considering the implication in your post.

That is b***** terrible. I bought Bison chucks and they are far better than that. My suggestion other than tearing all your hair out in a fit of rage, or maybe after you have done that, is work around it by making soft jaws (can you get blanks I wonder). Also if you have not done it yet delay trying to grind in position and see if you can true them up using shims under the outer edge of the removable jaws.

The reply you got about "if you expect accuracy...." is a bit inadequate to put it mildly.

Regarding the 3" spindle bore that is a myth I discovered. You would have been unable to get 3" diameter round bar in the spindle because it is actually 2.997".

P.S.

I do have another suggestion: If you pay me a few thousand dollars shipping I will drop off a 10" Bison Set Tru when I am passing through Brisbane next year in March.

[HuFlungDung]

I've often bored hard jaws 'straight'. Straight is a relative term, because you have to consider preloading the jaws at various pressures will affect the amount of deflection. Make up some kind of a heavy ring with allen caps or something to fit in the bolt holes of the jaws so you can close the chuck jaws against this rig.

I prefer a bored jaw for a hard jaw that will be used in roughing as the scallop effect of the tool marks creates more gripping power than a ground surface. Use something like a 1.5" boring bar and a carbide insert at moderate rpms, and a fairly coarse feed and of course, take a light cut. The insert should live long enough to make it all the way from front to back. You might even consider using an old TNMG insert, grind the chipbreaker off to make a nice sharp edge. The honed edge of a new insert does not cut quite as accurately on hard stuff because the depth of cut is so shallow.


BTW, most chucks can be bored out. One thing you'd want to check is how deep the pinion gears seat into the chuck because you'd not want to be boring the chuck out only to expose the end of the pinion bores. But I bored 1/2" out of a 12" Rohm to make it swallow 4.125

[Donkey Hotey]

I've got a BTC 6-jaw, 8 inch chuck on my TL-1. I'm not thrilled with it either for exactly the same accuracy issues you cited. If it's true at one diameter, the scroll seems to be well off somewhere else (0.005" or more).

I also noticed recently that at one diameter (the size of a particular bar of stock), one of the six jaws doesn't grip tightly. That chuck is on my list of things to upgrade. I already owned it when I bought the TL-1 so it was about cost savings at the time.

As for truing the chuck, I have a friend that did it once with a die grinder. He mounted the die grinder to the toolpost, used a round stone and a clamping ring on the jaws (as already described above). He touched up the inside of the jaws as it spun. Of course he had to take it all apart afterward to clean out the swarf.

In my case, I suspect the scroll on my chuck may not be the most accurate, so I haven't bothered (it would be right at one diameter and wrong at others).

[Peter Gibbs]

Gentlemen thankyou for your prompt replies, I will see what I can achieve in the next few days

Geoff How long are you in Birsbane for? thanks Peter

[Geof]

Originally Posted by Peter Gibbs .....Geoff How long are you in Birsbane for? thanks Peter

I have to admit I am a nitwit with a poor grasp of geography; it is not Brisbane it is Perth I will be calling at. Having checked on a map I now know they are a few miles apart.

[Peter Gibbs]

Well true, not far when your on a 14 hr flight but still a little ways to catch up and have a beer .....only 3400klm I expected more from a KIWI peter

[Geof]

Originally Posted by Peter Gibbs Well true, not far when your on a 14 hr flight but still a little ways to catch up and have a beer .....only 3400klm I expected more from a KIWI peter

I'm getting old

The 14 hour flight will let me off at Auckland, then after a day or two a much shorter flight puts me in Sydney to board a ship for a cruise ending up in Cape Town.

[cmacclel]

How did it go?? Did you get the chuck issue taken care of?

Mac

[Peter Gibbs]

Hi Mac No I wasnt really happy.... but they did say the the reason the chuck "looked " out of truth was because it was closed beond its normal or reccomended closing dia. Fair cop I guess....

I asked about their claims that as Zero set chuck can be ajusted to ,... 0005th which is correct but you have to undo the face screws and adjust it.. for each time you change the job...

..if fact you can adjust like a 4 jaw and get it perfect ....till you tighten the face screws the you end up with .0005, ....if you work at it... it takes time though...
..and I must admit that I fell down here on the conversion of thou to mm when I convert the 0005 thou to mm thinking it was a wonderfully made chuck....it is .015 which when you are making a crank shaft is like a door step... so I sat down and made 5 sets of soft jaws ..

.. we will see how that goes... looks like I had too high expectations I explained that the instalation instructions were nebulous at best cheers Peter