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In the market for scroll chuck 8 TPI
- Thread starter finsruskw
- Start date
- Joined
- Feb 13, 2017
- Messages
- 2,138
I can't direct you to a chuck assembly directly. But the part particular to your machine is actually the "backing plate". A chuck is a chuck is a chuck. They differ mostly in the final accuracy. And most are bolted to a backing plate. I would say to find the chuck you desire, and probably afford, and then find the proper backing plate for that size chuck.
There are several sources for them. For a small machine at 1-1/2x8, I usually look to Grizzly first, then Little Machine Shop. There are many others, I just can't think of their names off the top of my head. But you're looking at $100 or less for the backing plate. It must be trued to the specific machine that its' used on. Then machined to fit the particular chuck to be mounted.
Neither is difficult, although a bit time consuming. There are many uTube videos on the subject. The research on the subject will probably take as long or longer than the actual job itself. It doesn't take that long. I've done several over the years. With a 3 or 4 jaw scroll chuck, center matters. A 4 jaw independent will be more forgiving, being a matter of balance rather than absolute center.
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There are several sources for them. For a small machine at 1-1/2x8, I usually look to Grizzly first, then Little Machine Shop. There are many others, I just can't think of their names off the top of my head. But you're looking at $100 or less for the backing plate. It must be trued to the specific machine that its' used on. Then machined to fit the particular chuck to be mounted.
Neither is difficult, although a bit time consuming. There are many uTube videos on the subject. The research on the subject will probably take as long or longer than the actual job itself. It doesn't take that long. I've done several over the years. With a 3 or 4 jaw scroll chuck, center matters. A 4 jaw independent will be more forgiving, being a matter of balance rather than absolute center.
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- Joined
- Sep 22, 2019
- Messages
- 942
The chuck I have now is a 25$ used unit and it screws onto the spindle, no problem there.
So, there are no backing plates already threaded & ready to install as well as no chucks as well?
Am I correct in my assumption that the backing plate needs to be the same diameter as the scroll chuck them?
Found this on the bay
So, there are no backing plates already threaded & ready to install as well as no chucks as well?
Am I correct in my assumption that the backing plate needs to be the same diameter as the scroll chuck them?
Found this on the bay
Heavy Duty South Bend Lathe 6" Face Plate 1-1/2" x 8 TPI Threaded Excellent USA | eBay
This is a heavy dutySouth Bend Lathe 6" Face Plate with 1-1/2" x 8 TPI Threads. Threaded 1-1/2" x 8 TPI. South Bend Lathe face plate. 1-1/4" Thick at hub.plate is 9/16" thick. Carefully cleaned and lubricated.ready to go right to work.
www.ebay.com
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- Joined
- Dec 20, 2012
- Messages
- 9,422
This is a brand new 5" Bison 3 jaw chuck with universal jaws with a 1-1/2-8 direct mount. It is not a Set-tru but on a 3 jaw chuck used for first operations that isn't important. Currently no bidders and starting at $315, a decent price for a high quality chuck. If you're the only bidder you might just pull it off for that price.
- Joined
- Feb 13, 2017
- Messages
- 2,138
There are any number of backing plates threaded for 1-1/2x8. The back side, opposite where the chuck mounts, will be approximate, sometimes a rough casting surface. You will mount the backing plate backwards on the spindle. A light cut, 2 or 3 thou is usually all that's required. When the backing plate is reversed on the spindle, where it's facing the right direction, it is true to the spindle.
The next consideration is to true the "front" surface. Again, a couple thou is all that is usually needed. There is a raised "nub" in the center. That rise, or nub, must match a recess on the back of the chuck. There is a very slight taper on the edges. That taper should be maintained. Once the chuck fits it well enough, the back plate is true to the spindle. When the holes are drilled and the chuck bolted up, any (in)accuracy now is a function of the chuck itself.
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I just followed the link from a new post above for a chuck with a back plate installed. There is another, a German model for $299 plus whatever. I can't see eBay on Firefox now so just have to look at the listings. When a chuck comes supplied with a back plate, there are some checks that can be done when it is installed. If the accuracy is sufficient it can be used as received.
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A three jaw, actually any scroll chuck, has limits to its' accuracy. The really important issue is that the chuck jaws are parallel to each other. That they grip the entire length of the jaw for all jaws. There are limits to this accuracy as well. But if there is no daylight to be seen, they should be good enough. Center accuracy can be adjusted sometimes by shifting the jaws around slot to slot. I mark 1, 2, 3 with a sharpie, rotating until I have the lowest offset. Then I cut grooves in the jaws and punch marks on the body so they can be removed and reinstalled the same. The jaws will always be in sequence 123, but shift slot to slot.
Any work done in that chuck will be true to its' own center. So long as the work is mounted in the chuck. When it's removed and reinstalled, that center is lost. If the center is vital, the work should be done in a 4 jaw, trued up each time with an indicator. There are practical limits that only you can determine if your machine meets those limits. Usually, a half a thou at six inches is close enough. Only you can go up or down from that.
True separation of the "men from the boys"(like me) is the time it takes to achieve the desired accuracy. Where a master can do a setup in an hour or two, it takes me several days. That's my perspective though.
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The next consideration is to true the "front" surface. Again, a couple thou is all that is usually needed. There is a raised "nub" in the center. That rise, or nub, must match a recess on the back of the chuck. There is a very slight taper on the edges. That taper should be maintained. Once the chuck fits it well enough, the back plate is true to the spindle. When the holes are drilled and the chuck bolted up, any (in)accuracy now is a function of the chuck itself.
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I just followed the link from a new post above for a chuck with a back plate installed. There is another, a German model for $299 plus whatever. I can't see eBay on Firefox now so just have to look at the listings. When a chuck comes supplied with a back plate, there are some checks that can be done when it is installed. If the accuracy is sufficient it can be used as received.
=
A three jaw, actually any scroll chuck, has limits to its' accuracy. The really important issue is that the chuck jaws are parallel to each other. That they grip the entire length of the jaw for all jaws. There are limits to this accuracy as well. But if there is no daylight to be seen, they should be good enough. Center accuracy can be adjusted sometimes by shifting the jaws around slot to slot. I mark 1, 2, 3 with a sharpie, rotating until I have the lowest offset. Then I cut grooves in the jaws and punch marks on the body so they can be removed and reinstalled the same. The jaws will always be in sequence 123, but shift slot to slot.
Any work done in that chuck will be true to its' own center. So long as the work is mounted in the chuck. When it's removed and reinstalled, that center is lost. If the center is vital, the work should be done in a 4 jaw, trued up each time with an indicator. There are practical limits that only you can determine if your machine meets those limits. Usually, a half a thou at six inches is close enough. Only you can go up or down from that.
True separation of the "men from the boys"(like me) is the time it takes to achieve the desired accuracy. Where a master can do a setup in an hour or two, it takes me several days. That's my perspective though.
.
- Joined
- Oct 16, 2019
- Messages
- 6,580
I bought a 1.5 x8 TPI backplate for my 4-jaw from Shars.
Other than them sending a defective one the first time I’m quite pleased with the end result.
Sent from my iPhone using Tapatalk
Other than them sending a defective one the first time I’m quite pleased with the end result.
Sent from my iPhone using Tapatalk
- Joined
- Dec 20, 2012
- Messages
- 9,422
The chuck I linked to above is a direct mount, meaning the chuck is already mounted to a Bison back plate that fits the chuck as the maker intended. Just the back plate alone sells for almost $200 on ebay. Adding a Bison chuck with universal (reversible) jaws to it makes this one a serious deal.
I grant you that there are better chucks out there than a Bison but they are still pretty good chucks. For this price, I would jump.
I grant you that there are better chucks out there than a Bison but they are still pretty good chucks. For this price, I would jump.
- Joined
- Oct 16, 2019
- Messages
- 6,580
I agree with Mike on the Bison, definitely a good deal!
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- Oct 18, 2016
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- 2,872
A standard 3 jaw chuck will have a certain amount of run out in the jaws. A set-tru chuck has a provision for adjusting
the jaws in order to eliminate or minimize run out. This is important for accurate work, and makes it possible to machine
a part, remove it from the chuck and turn it around, and still run true, or nearly so.
the jaws in order to eliminate or minimize run out. This is important for accurate work, and makes it possible to machine
a part, remove it from the chuck and turn it around, and still run true, or nearly so.
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