Alignment pin to bolt distance

Watsonjay · October 19, 2025, 09:35:39 PM

Is there like a standard measurement for bow limb bolt to alignment pin distance?

Watsonjay · October 19, 2025, 10:34:19 PM

The only commercial 3-piece I have to measure is a black hunter and that is Chinese of course. It seems to be about 2 3/16 from center pin to center bolt. Just wasn't sure if this is standard or if there is one.

mmattockx · October 19, 2025, 11:07:44 PM

Quote from: Watsonjay on October 19, 2025, 09:35:39 PMIs there like a standard measurement for bow limb bolt to alignment pin distance?

ILF mounts have the two connection points at 2 5/16" centres if that helps any.

Mark

Kirkll · October 20, 2025, 12:23:02 AM

I've always used 2" below and 1/2" above, but some of my designs I use 1/2" and 2.5" below the bolt, and I always elongate the lower pin hole in the limb .040 so it doesn't bind up and the always fit perfectly. I don't care for a single location pin set up.

Watsonjay · October 20, 2025, 07:52:58 AM

Thanks guys. Sounds like there really isn't a standard unless it's ILF.

mmattockx · October 20, 2025, 10:55:34 AM

Quote from: Kirkll on October 20, 2025, 12:23:02 AMI've always used 2" below and 1/2" above, but some of my designs I use 1/2" and 2.5" below the bolt, and I always elongate the lower pin hole in the limb .040 so it doesn't bind up and the always fit perfectly. I don't care for a single location pin set up.

This is the better way to go. In machine design we never use a bolt for location, it is always just to clamp the parts together and location is set with pins or pilots into a bore, etc.

Mark

Watsonjay · October 20, 2025, 01:30:21 PM

I was just going to build a 3-piece and send it to a buddy who lives on the Island of Guam. I thought maybe if he wanted to get different limbs he could order them from a vender and have it fit without having to have me make him new ones which was why I was wondering if there is a standard in the industry so he could buy heavier or lighter limbs from anyone.

Crooked Stic · October 20, 2025, 08:15:57 PM

I use a block mounted on a flat plate. The ideal setup would be your bolt hole centerd between the pin holes. That way you can drill from the same side keeping the down sides down. Then if your mill job is not perfect uneveness is all on one side

Kirkll · October 23, 2025, 10:55:49 AM

Quote from: Watsonjay on October 20, 2025, 01:30:21 PMI was just going to build a 3-piece and send it to a buddy who lives on the Island of Guam. I thought maybe if he wanted to get different limbs he could order them from a vender and have it fit without having to have me make him new ones which was why I was wondering if there is a standard in the industry so he could buy heavier or lighter limbs from anyone.

Building a 3 piece bow sucsessfully that tracks straight is totally dependent on limb alignment. Even using a milling machine that has excellent results getting uniform hole alignments in both the riser and limbs, they still need to be mounted and checked for straightness before shaping the limb profile. It's not uncommon for those limbs to be off center at the tips a wee bit, and need a straight edge to determine center of limb. This is std procedure, and critical.

Bottom line is your idea that someone could retro fit finished limbs on an existing riser you build is not realistic unless you incorporate a lateral limb adjustment system.

Also.... Checking your limbs for accuracy making sure they are exactly 90 degrees at the butt and the tips is vey important before you mount them on your riser block. You can easily build a twist into your limbs that will be a nightmare to adjust tracking on even if they are perfectly aligned.