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What Did You Buy Today?
- Thread starter darkzero
- Start date
- Joined
- Nov 23, 2014
- Messages
- 2,634
The backing plate on a chuck typically has something called a "register" which fits tightly to the back of the chuck. Somewhat like the tapered centers dropping into your tail stock, though the chuck register usually doesn't have a taper. It's machined square and is a slip fit onto the chuck.
The backing plate has countersunk clearance holes for bolting to the chuck (if the chuck back is threaded). The register radially aligns the chuck to the backing plate, tighten the cap screws in the backing plate to attach it to the chuck. Guys typically leave the register a few thousandths undersize so you can do a little "truing" with a brass hammer on the chuck if needed.
Set-tru chucks have cap screw holes through the face of the chuck and the backing plate has the tapped holes. The register is turned for more clearance. The amount of clearance is the limit of your adjustment. For example, if the pocket in the back of the chuck was 5.000" and your backing plate had a register diameter of 4.5", you'd have 0.5" of total adjustment (0.25" on the radius). There are typically 4 socket head set screws at 90's on the outside of the chuck that thread all the way through so they can touch the register. These 4 screws act like the jaws on a 4-jaw chuck.
In use, I mount the work in the chuck and check run-out with an indicator. I loosen the 3 clamping cap screws on the face of the chuck. My set-tru has the adjusting set screws labeled 1, 2, 1, 2 as I rotate the chuck. I rotate the chuck so a "1" is close to center vertically and zero the indicator. Then rotate the chuck 180 so the opposite "1" is centered vertically and note the number. Suppose it's 0.006". I use two Allen wrenches, one in each "1" screw and loose one side. Tighten the other and move the indicator to 0.003". I rotate back 180 and read the opposite side; should be 0.003" but sometimes it takes a very swings to dial it in.
I then zero the indicator and double check "1" to "1". If it's good I rotate so a "2" is at center height. Adjust the two "2" screws until the indicator reads zero.
Once everything is dialed in (much like dialing in a 4-jaw chuck), I snug up the 3 clamp screws on the face of the chuck and re-check runout.
Bruce
Here's a link to a thread on my install of the set-tru chuck on my G0709 lathe
Potd - Project Of The Day- What Did You Do In Your Shop Today?
Nice job. What is the reason for narrowing the wheels? I thought most people wanted wider wheels.
www.hobby-machinist.com
Now this is a scroll chuck correct?The backing plate on a chuck typically has something called a "register" which fits tightly to the back of the chuck. Somewhat like the tapered centers dropping into your tail stock, though the chuck register usually doesn't have a taper. It's machined square and is a slip fit onto the chuck.
The backing plate has countersunk clearance holes for bolting to the chuck (if the chuck back is threaded). The register radially aligns the chuck to the backing plate, tighten the cap screws in the backing plate to attach it to the chuck. Guys typically leave the register a few thousandths undersize so you can do a little "truing" with a brass hammer on the chuck if needed.
Set-tru chucks have cap screw holes through the face of the chuck and the backing plate has the tapped holes. The register is turned for more clearance. The amount of clearance is the limit of your adjustment. For example, if the pocket in the back of the chuck was 5.000" and your backing plate had a register diameter of 4.5", you'd have 0.5" of total adjustment (0.25" on the radius). There are typically 4 socket head set screws at 90's on the outside of the chuck that thread all the way through so they can touch the register. These 4 screws act like the jaws on a 4-jaw chuck.
In use, I mount the work in the chuck and check run-out with an indicator. I loosen the 3 clamping cap screws on the face of the chuck. My set-tru has the adjusting set screws labeled 1, 2, 1, 2 as I rotate the chuck. I rotate the chuck so a "1" is close to center vertically and zero the indicator. Then rotate the chuck 180 so the opposite "1" is centered vertically and note the number. Suppose it's 0.006". I use two Allen wrenches, one in each "1" screw and loose one side. Tighten the other and move the indicator to 0.003". I rotate back 180 and read the opposite side; should be 0.003" but sometimes it takes a very swings to dial it in.
I then zero the indicator and double check "1" to "1". If it's good I rotate so a "2" is at center height. Adjust the two "2" screws until the indicator reads zero.
Once everything is dialed in (much like dialing in a 4-jaw chuck), I snug up the 3 clamp screws on the face of the chuck and re-check runout.
Bruce
Here's a link to a thread on my install of the set-tru chuck on my G0709 lathe
Potd - Project Of The Day- What Did You Do In Your Shop Today?
Nice job. What is the reason for narrowing the wheels? I thought most people wanted wider wheels.
- Joined
- Nov 23, 2014
- Messages
- 2,634
It is. Set-tru chucks are scroll 3-jaw but can be finely adjustable to get no run out.
There may be other set-tru chucks out there that I'm not aware of. I could see uses for a 2-jaw, but can't say I've ever seen one.
Bruce
- Joined
- Nov 26, 2015
- Messages
- 5,124
I don't, but you could just call Starrett and ask?
- Joined
- Nov 14, 2016
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