PSI Corner-B-Gone Pen Blank Rounding Jig Copycat

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egnald

Member
Joined
Jun 9, 2017
Messages
669
Location
Columbus, Nebraska, USA
Hello all and Greetings from Nebraska.

Today I built a copycat of the PSI Corner-B-Gone jig. Previously I had a couple of bandsaw jigs to cut the corners off of my blanks based on an angle that was a fixed distance from the blade. I had one for 3/4 and one for 7/8 blanks. The problem was that not all of my blanks are square and I also don't always get the tube perfectly down the center. These problems cause the blank to be quite out of round when I start to turn it.

I liked the idea of PSI's Corner-B-Gone jig because it uses the tube to reference the blade rather than a stationary guide on the fixture. This compensates for off-center drilled holes and it allows me to not only trim off the corners but also to trim off any excess width on oversized or non-square blanks. I used it to prep some blanks for Southwest Mesa kits and it worked much better than my other jig. It is also less bulky and takes up much less storage space. Whoever engineered this for PSI was one clever designer.

The copycat jig is essentially made from some 1-3/4 square blocks of Poplar, a piece of 1/4-20 Ready Rod, some spare barrel trimming sleeves (used for spacers) and a couple of 1/4-20 star knobs. I had all of this stuff on-hand so the cost was negligible. Mount the blank using the bushings, set the bandsaw fence to the desired distance and run the blanks through rotating the jig a quarter of a turn between cuts first to square up the blank with the tube, then by rotating the blank in the fixture and another four passes to cut the corners off. After eight passes you are left with a relatively symmetrical octagon shape on center with the tube.

Anyhow, a before picture of one of the blanks showing shape irregularities due to my segmenting glue up along with a couple of pictures of the jig and the results of the blank after it was drilled, tubed, squared, and rounded on the jig are attached. For comparison I also attached a picture of my 3/4 inch fixed size rounding jig that it replaces.

Regards,
Dave
 

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Wmcullen

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Joined
Dec 1, 2020
Messages
96
Location
Fairfax, Virginia
Dave, this is fantastic! Specifically, I like how the jig works off of the center hole that's already drilled. All the pictures and the labeled image were very easy to follow, which I appreciate since I'm not familiar with the original jig. Overall you made this process very accessible. Thank you!
 

egnald

Member
Joined
Jun 9, 2017
Messages
669
Location
Columbus, Nebraska, USA
Dave, this is fantastic! Specifically, I like how the jig works off of the center hole that's already drilled. All the pictures and the labeled image were very easy to follow, which I appreciate since I'm not familiar with the original jig. Overall you made this process very accessible. Thank you!
Shortly after I posted I saw your Facet Jig post - pretty cool. It is almost identical in function except I rotate the entire jig for each facet instead of just the blank. I'm sure your printed jigs have much better accuracy than what I hack together out of wood. Originally I was planning on cutting the blocks into octagons so I could simply rotate the jig through all 8 cuts, but then I realized that since my fence extension is only 3/4-inch tall the octagonal blocks wouldn't ride against it properly so I left them square and simply rotate the blank between each set of 4 cuts. - Dave
 

Wmcullen

Member
Joined
Dec 1, 2020
Messages
96
Location
Fairfax, Virginia
I really like this design and your execution.
Now I understand why the blocks are 4-sided instead of 8-sided and I'm tracking your reasoning. In fact it could be a feature if you ever wanted to try octagonal pens with unequal sides... could be interesting and your setup would allow for that flexibility. Hmmmmmm now you got my wheels turning. ; ) THANKS!
Cullen
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egnald

Member
Joined
Jun 9, 2017
Messages
669
Location
Columbus, Nebraska, USA
Hi All:

I just finished making version 2.0. As discussed prior in the post the jig used square guides instead of octagonal because of the height of my auxiliary fence. So this version has both a taller auxiliary fence and octagonal guides so that the blank does not need to be adjusted between the two sets of 4 corners. It should also provide a more consistent and accurate octagonal shape than my previous version because no re-positioning adjustment is necessary.

The blank and associated bushings get mounted on the 1/4-20 ready bolt between the two metal spacers. The knob on the right can be used to move the right guide in and out to change the overall length of the jig leaving the knob on the left to retain the blank without having to screw it in a long ways each time. Of course a simpler version could be made by eliminating the right adjusting knob and the end piece while gluing the bolt it into the right guide.

Regards,
Dave

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