T/D drilling jig accuracies

[Kopper1013]

Hey guys wondering how accurate your T/D drilling jig/tools are?

My wife purchased me one that’s kinda like a dowel-it a year ago and I’m finally getting around to trying it out. Before I drilled my limbs and riser I decided I’d square up a piece of red oak and drill some hole’s then caliper from edge of hole to side of the board and see how close to equal those numbers where....

To say I was displeased would be an under statement, I was getting a diffence of .02 on average but without trying to adjust anything the numbers where always slightly different.

Am I being to critical? How accurate is your setup?

[buddyb]

Please post some pics of the jig you have. I have a self centering jig i purchased from Bingham's back in the 80s and it works great. I haven't ever measured it for accuracy though.

[skeaterbait]

I have a Dowel It that does a pretty good job. Typically after I get it lined up and snugged down will put a little pressure on the center part then loosen and re-snug it a couple of times. That typically get's it pretty good.

[Kopper1013]

[skeaterbait]

The nut on the back side of that jig (as the pic shows it) should allow you to make some adjustment. You ought to be able to pull that in line pretty easy I think.

[Kopper1013]

Lonnie I’ve worked that nut, I’ll get it close on a hole try and drill a couple more holes and it’ll work right back out of alignment... bet I’ve drilled 24 holes tonight

[skeaterbait]

Ouch, I can see where that would be a let down.

[Roy from Pa]

Could it be possible the sides of the wood are not square?

[Crooked Stic]

I have done a crap ton of TDs with the self centering jig. They are close at best. Never hardly ever perfect though. You may think they are doing good until you bolt the limbs on and see the problem not perfect there  either. But you can get by with them. Best to leave everything a little wide then run it thru the drum sander after bolted up.

[Kopper1013]

I thought that could possibly be Roy so I ran the calipers down the piece and she’s nice and square, plus the holes are bouncing either side of dead center like there is to much slop in the jig...I’m gonna spend some time with it this weekend I just don’t wanna burn a riser or limbs up on bad holes

[skeaterbait]

One thing I like about the Dowel it is that all four holes are tapped so you can move the inserts around. Something that has bounced through my mind, not that I have tried it yet, is to not turn the jig around. What I mean is, when you drill the first set of holes and find you are off (for instance) .02 to one side of center, then you flip the jig to the other end of the riser, you are now .02 off to the other side of center. With the Dowel it instead of flipping the jig just slide it from one end of the riser to the other then move the inserts to corresponding holes. In theory this should make both sets of holes offset to the same side. At that point, as Mike said, bolt it up and run it through the drum sander again, OR, realize that as long as the offset is on the same side, who is really going to notice .02"

It would be nice to have an insert made that is 27/64" instead of having to redrill a hole without the jig.

[Crooked Stic]

Lonnie I have drilled all my holes 7/16s for years. Works fine for wood maybe not so much if you are tapping steel. And you are right about not flipping the jig if you dont have to.

[skeaterbait]

Greg, I apologize for the hi-jack, no intent I promise.


Mike, thank you for the tip.

[buddyb]

I took mine to a machinist and he redrilled my 3/8 to 27/64 for $20. 

[Buemaker]

Kopper, I think the jig you have is the one sold by Master Crafters and the people who took over that shop. It was supposed to be the best of its kind.

[Roy from Pa]

I can't see how it could stay accurate, after running a drill bit down inside those holes a few times?

Doesn't that affect the inside wall of the hole?

Plus trying to hold the drill exactly straight?

Seems to me that incorporating a drill press with a jig in a vice would be better?

But I never did this so what the heck do I know about gwass bows?

 

[skeaterbait]

I can't see how it could stay accurate, after running a drill bit down inside those holes a few times?

Doesn't that affect the inside wall of the hole?

Plus trying to hold the drill exactly straight?

Seems to me that incorporating a drill press with a jig in a vice would be better?

But I never did this so what the heck do I know about gwass bows?

 

The inserts and center piece is hardened to resist wallering. I am sure over enough time it could affect it but it's really intended to be a guide and not keep a lot of pressure on the bit.

However, that does make a light bulb for me. I have noticed, with mine, that some drill bits fit more snug than others indicating a certain amount of play in the guide. That could account for a bit of off center. Not sure if it would cause .02" or not but I am just thinking. (there you go Roy, have fun)

[Roy from Pa]

Lonnie, I hope a ckt breaker didn't trip when yer light bulb came on?

 

[Mark R]

Kopper1013 I have the same one I got it from the guy who makes or has them made for him, specifically for 3 piece take down Bows, there is minute slop in it but it is easy to work with and once tight it's as close as I'll probly get as any other way, I never assume everything is gonna be so perfect that I won't need to adjust a little here and there to make things work out properly, of course if it's so bad and not working out and you find a better way by all means do it. To be honest I never thought it was that inaccurate that I should check. 

[Roy from Pa]

Guess this is why I make one piece longbows.

Crooked Sticky has the solution, leave the limbs a little wide, then find your center line and layout the edges off that.