Boring Jaws?

Hello,
I have been running a Quick Turn for about 6 years now, and I still haven't been able to figure out a good way to bore jaws, and keep the run out to .0005 or less. Kitagawa 8" chuck. Usually use aluminum jaws. Qt200.
Kind of self taught. I was hoping some people would share their technique.
Thanks in advance'

Roger

I have an old, very loose 8" Howa on the 1986 Mazak, which makes great parts. The avatar is the chuck holding a set of 15" jaws. It was loose before I got it, but this probably doesn't do it any favors. I can hold 0.0005" runout on OD and 0.0005" parallel on those big ass jaws (Hast X rings) in this machine using this method:

Clean jaws, grease chuck, take file card and clean the serrations well in the aluminum jaws with the wire brush side. File out any nicks in the teeth with a 60° needle file or metric thread file.

For gripping on OD parts: After jaws are on tight, set chucking to ID. Set jaw pressure to same setting you are going to run the job. Open chuck. Manually bore the ID to 0.050" larger in diameter than a small, round ring or plug. Stop spindle.

Do NOT use adjustable spiders. They cause the jaws to rock unevenly--especially on loosy goose chucks.

Blow out jaws and flip the chucking switch from ID to OD. Clamp on ring. Jaws will have 0.050" stroke from top of travel. Bore jaws in dedicated jaw boring program (work #1) using same chuck pressure and RPM you will use to run the part. Bore the ID of the jaws 0.000" to 0.002" smaller than your part.

Important--Be sure to undercut the ID corner of the jaws--easily done using the necking feature when using a TPG boring bar.

Never try to check the fit by sliding the part into the chuck with chuck still clamped on ring. If part fits, jaws are bored too big and will only touch on 3 points.

Open Jaws, remove ring. Clean jaws and then wipe them with a clean shop rag. Blowing them off is not enough--especially for pie jaws.

Chuck part. Lightly tap part into face of jaws with 1lb deadblow hammer to seat part. Verify runout is dead nuts. Make chips. Sell finished part.

boring jaws

The simple trick i found for boring jaws goes as follows:

depending on the size of the part your holding i usually invert the jaws and put the jaws as close together as i can. I then drill let say a .500 hole thru the center of the jaws. I then take a .460-.470 gage pin and put it in the hole it just drill and clamp the jaws. invert the chuck back to external. if you have to bore back an inch to hold part i will put the plug in 1.100 deep. then i bore my jaws. this alllows for the jaws to open up .030 to except part and you can bore the jaws to size instead of .020 over to allow jaws to release part. This works real well unless your part is longer than the jaws. Then i advise you to buy an 8 inch bore ring made for boring jaws. A company called Monster jaws inc in California sells them cheap along with 8 Inch kitagawa aluminum jaws. There only $29.97 a set and they are precision made.

alexor1971 said:

The simple trick i found for boring jaws goes as follows:

depending on the size of the part your holding i usually invert the jaws and put the jaws as close together as i can. I then drill let say a .500 hole thru the center of the jaws. I then take a .460-.470 gage pin and put it in the hole it just drill and clamp the jaws. invert the chuck back to external. if you have to bore back an inch to hold part i will put the plug in 1.100 deep. then i bore my jaws. this alllows for the jaws to open up .030 to except part and you can bore the jaws to size instead of .020 over to allow jaws to release part. This works real well unless your part is longer than the jaws. Then i advise you to buy an 8 inch bore ring made for boring jaws. A company called Monster jaws inc in California sells them cheap along with 8 Inch kitagawa aluminum jaws. There only $29.97 a set and they are precision made.

Click to expand...

Thanks for that input. We have one of the ajustable face rings on the way. Most of our stiff is longer than the jaws, so I think this will work best.

+1 on the bore ring. I think they are essential to making custom jaws that grip the part well. In my experience, if you bore jaws without one you'll end up with jaws that grip well at the back, but are a bit loose at the face of the jaws. With the bore ring, the jaws (chuck, etc.) flex as they will when you have a part clamped in the jaws, so when you bore the jaws, you'll end up with something that grips consistently along the bore.

kwmachine said:

+1 on the bore ring. I think they are essential to making custom jaws that grip the part well. In my experience, if you bore jaws without one you'll end up with jaws that grip well at the back, but are a bit loose at the face of the jaws. With the bore ring, the jaws (chuck, etc.) flex as they will when you have a part clamped in the jaws, so when you bore the jaws, you'll end up with something that grips consistently along the bore.

Click to expand...

I have noticed this as well. If I straight bore jaws with no pre load on the chuck. Then when I try to groove a part , say 1 3/4 dia. 3" from the face of the jaws, I end up fighting chatter. If I bore the jaws with a .002 taper (bigger to the inside) then the chatter problem goes away.