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Availability:
In Stock.
Arrives
Monday, Oct 19
Size: 4" Size, 1 1/2"-8 Thread
Style: For 3-Jaw Chucks
Features
- Must be machined for concentricity
- Model Number: 3900-3212
- Item Package Dimension: 3.0" L x 6.0" W x 3.0" H
- Item Package Weight: 2.6 lb
Description
4" 1-1/2" 8 Threaded 3-Jaw Backplate Assembly instructions included. D is 4". D2 is 10 2.90". Bolt circle is 3.3". Number of bolt holes is 3.
Brand: HHIP
Material: Steel
Compatible Devices: Drilling Machine, Grinding Machine, Lathe, Milling Machine
Thread Size: 4 1/2-8
Capacity: 4 inches
Brand Name: HHIP
Included Components: 4 INCH 3 JAW CHUCK THREADED BACKPLATE (1-1/2-8)
Global Trade Identification Number: 70
Number of Packs: 1
Manufacturer: HHIP
Number of Items: 1
UPC: 769053022970
Unit Count: 1 Count
Item Type Name: 4 INCH 3 JAW CHUCK THREADED BACKPLATE (1-1/2-8)
Model Number: 3900-3212
Manufacturer Part Number: 3900-3212
Compatible Devices: Drilling Machine, Grinding Machine, Lathe, Milling Machine
Thread Size: 4 1/2-8
Capacity: 4 inches
Handle Type: Hand Wheel
Lock Type: Manual
Material Type: Steel
Frequently asked questions
If you place your order now, the estimated arrival date for this product is:
Monday, Oct 19
Yes, absolutely! You may return this product for a full refund within 30 days of receiving it.
To initiate a return, please visit our Returns Center.
View our full returns policy here.
To initiate a return, please visit our Returns Center.
View our full returns policy here.
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Top Amazon Reviews
Size: 3" Size, 1 1/2"-8 Thread
Style: For 3-Jaw Chucks
I purchased this so I could mount an ER 32 college check to my craftsman Atlas 12” lathe. I mounted it to the machine and took a skim pass to true it to my spindle. After receiving the check, I’m machine the register down to a very nice fit. This is a good product and a great value for me.
Reviewed in the United States on November 18, 2025 by Brian Grigsby
Size: 4" Size, 1 1/2"-8 Thread
Style: For 3-Jaw Chucks
I have an old craftsman lathe 36 inch bed 7 inch swing 1-1/2 inch spindle 8 thread her inch This fit fine had to face which was easy Items made out of cast-iron, not a problem Works great
Reviewed in the United States on August 11, 2026 by James
Size: 4" Size, 1"-8 Thread
Style: For 3-Jaw Chucks
Fit my 1946 Craftsman 101/Atlas 618 metal lath perfectly. 10 out of 10 would purchase again!
Reviewed in the United States on May 16, 2025 by weldor
Size: 3" Size, 1/2"-20 Thread
Style: For 3-Jaw Chucks
Good product for the money - was NOT balanced or centered for the threads? Was easy to machine to fix. Also does NOT fit with K11 chuck as "often bought together" said. Again was easy to turn down to fit ... but needed machining. The allen bolts sent with the chuck do not fit either, but #6 metric hardware ones do.
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Reviewed in the United States on February 25, 2021 by Steve C.
Size: 3" Size, 3/4"-16 Thread
Style: For 3-Jaw Chucks
I bought this baseplate so that I could mount an ER-32 collet chuck (HHIP 3901-5032 ER-32 Collet Chuck, 80 mm Diameter) by the same manufacturer to the spindles on both my Sherline lathe and mill. I was hoping that it would mate right to the chuck but it doesn't quite do that. That's partly why I only gave it three stars. The chuck looks like it is made of quality stainless steel. But this backplate looks like it is made from a lower quality steel that will rust. It didn't come as blue and shiny as the one in the photograph but it will shine up a little after doing some cutting I plan to do to make the two parts fit together. Luckily, the three machine screw holes align correctly so both will work with the bag of M6 hex bolts that I bought. The insert on the large end of the backplate is 76.6mm in diameter while the recess on the back of the chuck is only 74.6mm in diameter. I will have to cut the insert down in order for it to fit into the recess on the back side of the chuck. One could bore the recess of the chuck larger but it would remove material supporting the threaded holes in the chuck. But before I do this operation, a facing operation on the small end of the backplate needs to be done first. The 3/4-16 spindle threads do fit my machine's spindle but they don't go all of the way through the backplate. Also, they look pretty rough (with little burrs on them) but the device seems to mount okay. Taking off 5 or 6mm of metal off the small end of the backplate will bring the threads closer to the outer surface so that the threads on the spindle will have more to grab on to. I am hoping that the backplate is easy to machine because all of my lathe cutting tools are made of HSS. To do this facing operation, I will mount the backplate backwards onto the spindle and the backplate will become my work piece. After that machine operation is done I can turn the backplate around and mount it as it will when the chuck is bolted onto it. Turning the insert down by about 1mm will reduce its diameter and the chuck should be able to fit around it. The bolts are not for alignment but will just hold the two pieces together. If the backplate inserts snuggly then it will serve to hold the chuck precisely in position relative to the backplate and thus the lathe itself and its tooling. This will be the most critical part of the operation and I will need to check for fit between successive passes so that I don't overcut the insert. If the backplate had come to already fit the chuck then I would have given this product four stars. If it had also been made of stainless steel, then my review would have given it five stars. We'll see how the machine operation goes. -----------------------Later I did all of the machining operations and it was a success. I cut about 6mm off the small end and this exposed the 3/4-16 threads. This left some burs on the surface so that when I mounted it, the thing wobbled. Luckily I didn't panic. After eliminating the burs with a slight boring operation, the wobble went away and it was visibly very steady. One thing to note is that the insert on the large end has a slight taper as does the collet chuck that I bought this thing to mount. But I don't think the taper does much on such a short little insert which only protrudes about 3mm. But this is enough to register the chuck solidly. I made 0.01mm cuts the whole way because I feared making the insert to small in diameter which would ruin the backplate. I was testing for fit after each pass near the end. After the final pass the insert dropped in and I was done. I know I voided the warranty on this thing but now it is usable. Oh happy day! I can finally use 3/8" and larger end mill bits on my mill and I can mount round stock up to 20mm in diameter on my lathe without having to resort to the 3-jaw chuck.
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Reviewed in the United States on February 4, 2017 by Paul K. Mckneely
Size: 4" Size, 1 1/2"-8 Thread
Style: For 3-Jaw Chucks
Used this backplate to fit a ER32 collet chuck to my 9x20 lathe. I had to do some minor machining to fit the plate to my lathe, and the chuck to the backplate after installation on the lathe. This was expected and in fact necessary in order to achieve an accurate installation. Expect to have to do the same if you purchase this backplate. Material appears to be cast steel, not cast iron, and machines nicely. There was plenty of material on the projection on the front of the plate to allow for machining to match the recess in the back of the chuck.
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Reviewed in the United States on December 29, 2020 by Larry
Size: 3" Size, 1/2"-20 Thread
Style: For 3-Jaw Chucks
Perfect fit for my lathe and fastening my new chuck into.
Reviewed in the United States on July 6, 2025 by bearside
Size: 3" Size, 1 1/2"-8 Thread
Style: For 3-Jaw Chucks
Good fit on spindle. Cast iron, easy to machine. Used this on a collet Chuck for my lathe. Remounting on lathe keeps concentric within a few ten-thousandths. Can't ask for better.
Reviewed in the United States on February 10, 2020 by Amazon Customer