As I have written several times – JoPo interchangables are the best on the market!! As a pro shop operator and JoPo installer, I have learned a few things which I’m passing along to you. This is a kind of lengthly document, so you may want to print it! Or go get your favorite beverage and get ready for a good read! As always, if you have any questions or comments, let me know.
Installing a JoPo interchangeable thumb is just like most similar systems. JoPo’s use an outer (receiver) sleeve with a thumb insert inner (insert). What follows are some do’s and don’ts we recommend. Welcome to the last thumb insert system you will ever want to use! And for PSO’s a great option for your customers!
The hole for the receiver is 1 ½” in diameter. The depth is the difference. For JoPo’s, the hole depth needs to be 3.22” (approx. 3 
¼” – 1/32”) . This distance is from the bottom of the stop collar (if your drill bit has one) to the first edge of the clearance wings (see illustration). Note: As a practice, we drill a pilot hole deeper than the hole for the receiver. This provides a place for excess glue to gather.
Next is the receiver. The key is to rough up the outside face of the receiver – this is the part that comes in contact with the ball. I use the course face of a wood rasp. Go around the entire outside of the receiver. Note the verical grove on the outside face of receiver. Mark it with a yellow or white grease pencil – this is your alignment line at the back side of the thumb hole.
Use a paper towel with rubbing or denatured alcohol to remove any loose materials from inside the cut hole – get this as clean as possible of drilling dust. Place our JoPo Super Glue around the inside of the hole – you will have 45 seconds to place the receiver. This glue is thin and runs fast, so it helps to place the glue with the hole horizontal with your work bench. With ball still horizontal, place the receiver with the groove to the backside of the thumb hole. I typically mark the centerline mark on the ball at the bottom of the thumb hole with an “X” so I rotate the outer in the correct position. I usually press the front (thumb pad side) to ensure a positive mechanical connection with the ball.
Once the glue has set, you can trim any excess material of the receiver above the hole off – usually about 1/32″ +/-. We use a plug cutter made by Turbo. And you can, at the sametime, place the insert and trim it as well. That is all there is to it! One last process we perform is to place a little Vaseline on the Insert Tread and Alignment Pegs. The JoPo Twist fits together snugly. The Vaseline helps with placing and removing the insert.
If you have not worked with the JoPo Insert (inner) blank before here are some suggestions when gluing in a thumb insert. Please note: the insert cannot be larger than 1 1/4″ diameter. For larger thumbs please get our 1 3/8 insert with slug material:
1) Test fit your insert solid into the JoPo Blank Insert – make sure it will fit!
2) Use a wood rasp (as noted above) with a course grate for “roughing” up the outside surface of the insert solid
3) Use a 100-grit sandpaper or screen to rough up the inside of the blank – I typically go in a horizontal rounded direction so the course sanding is perpendicular to the rasping of the insert solid. If the blank and the insert fit snugly from step one you may not need to do this – check twice – glue once!
4) Use a fairly long setting adhesive – this will give you time to place the solid in the blank. Fast curing glues are not a good solution. I would not recommend that approach. If I can, I let the glue set overnight. However, I typically use a two part 5 minute epoxy glue form JB Weld. I found mine at Home Depot – it is pretty common.
5) Make sure when you are placing the glue inside the blank, you spread it thin. The roughing up process will make for a tight fit – excess glue will squeeze out in that case. Do not place huge amounts of glue around the inside of the blank. But make sure the glue goes down toward the bottom of the hole.
6) Check the bottom of the Blank Insert – see if there is any excess glue at the bottom, wipe it off as soon as possible. The excess glue can make the insert difficult or impossible to place inside the JoPo Receiver. Pay pictular attention to the three alignment tabs. Typically, I turn the insert upside down with the alignment pegs facing upward. And I will place the upside down insert on wax paper. If any exess glue gets on the paper it is easy to remove.
One final thought: I know from practice some of the glued blanks tend to swell during the year. I do two things: sand the outside of the blanks after the glue has set – test fit and sand as needed. And the second thing is, to put a thin coating of Vaseline on the outside of the Insert theads and alignment pegs. It all depends on what seems to be a problem – if it is hard to screw in – it is a thread thing; if it is hard to click into place – it is a peg thing. You will need to test it.
Alwasys remember this: if you don’t hear the click, the two parts are not correctly joined!
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I hope you find this helpful. It is our goal to make this process as repeatable for you as possible. If you have any questions or comments, let us know. Bowl well and have fun,
John
