An OXA boring bar holder

[WobblyHand]

Lacking an adjustable parallel, you could set dowels in the dovetail with the ends protruding and take an outside measurement instead.

Could be possible, thinking it would require some creative clamping. Otherwise another pair of hands. I will try to see if I can do that. Might work!

 

[mattthemuppet2]

Find a holder that locks up the way you want it to, then use two pins (or drills) that touch the sides of the dovetail and measure between them with a digital caliper. Then all you need to do is cut the dovetail to the same gap between the pins. That's what I've done for the ones I've done recently and each one fits perfectly.

 

[T Bredehoft]

Be careful...

I made a bunch of small (AXA) tool holders, was very careful with the 'dovetails', one went over by a couple of thou, now I have to lock it with the lever at 7:00. I wouldn't have thought that would make that much difference.

 

[mattthemuppet2]

Yes, you have to hold it to a thou to get a consistent lock up

 

[WobblyHand]

I need to wait for the variable parallels, or come up with a better technique.

Tried using O1 pins and clamping the pins to the female dovetail with toolmakers clamps and measured the OD. The pins overhang by 0.25". No good. The small 3/16" pins are deflecting slightly. You can feel it when trying to get the ratchet to click. Can't get repeatable measurements. (+/- 0.002") Oh, the distance is just large enough to force me to my 1-2" Shars "old school" micrometer at 1.04x". My Digimatic Mitutoyo goes to 1.033". (0-1") As one might expect, the nicer micrometers have a much better feel to them. I can try measuring at first touch, would this be consistent?

Re-did the setup. Measurements are consistent now. Ratchet not affecting result. Must have had some crud in the way.

Measurements: pin diameter D=0.18775" (both pins!)
dovetail height h=0.2645"
outside dimension between pins clamped to female dovetail = 1.0421"
equivalent inside dimension between pins = OD - 2*D = 0.6666"
Known: dovetail angle = 60*
Calculation: b = ID + D*( 1 + 1/tan( angle/2 ) ) = 0.6666 + 0.18775*( 1 + 1/tan(30*) ) = 1.1795"
top opening size (theoretical, pre-chamfer) of dovetail = b - 2*(h/tan(angle)) = 1.1795 - 2*0.1527 = 0.8741"

 

[mickri]

I think that you are making a mountain out of a mole hill. Over thinking to the max. You are only making one tool holder. Not gearing up for a production run.

Take one of your existing holders that you like the way it fits on the tool post. Place it on your material and scribe a line of the dove tail. Hog out most of the center and cut the dove tail on one side. Then slowly cut the other side's dove tail until you get the fit you want on the post. You are done.

Just my two centovos.

 

[WobblyHand]

I think that you are making a mountain out of a mole hill. Over thinking to the max. You are only making one tool holder. Not gearing up for a production run.

Take one of your existing holders that you like the way it fits on the tool post. Place it on your material and scribe a line of the dove tail. Hog out most of the center and cut the dove tail on one side. Then slowly cut the other side's dove tail until you get the fit you want on the post. You are done.

Just my two centovos.

Guilty. I do want to make more than one of these, but still guilty. Can you tell I like math?
Yeah, I'll do it like you suggested. It's still good to have numbers as a sanity check.

For basic order of operations, what's first? The dovetail or the boring bar hole?

 

[benmychree]

There are two types of Aloris tool posts, the wedge type and the plunger type, the one shown in the video is the plunger type, the wedge type has the sliding gib, and is the most repeatable type, but not particularly more rigid than the plunger type, which is designated with an (X) in the model number.

 

[mickri]

I would do the dove tail first followed by whatever holes that need to be drilled and tapped so you can mount it on the post. Once mounted on the post you can bore the hole starting with a drill followed by an end mill held in a chuck on the lathe. This will ensure that the hole for the boring bar is concentric and on centerline with the spindle.

 

[WobblyHand]

After a bit of struggle and finagling, managed to cut the dovetail and drill and tap the adjuster hole. The dovetail fitting involved more than I expected, but it fits ok. Looks like I need a slightly larger adjuster, because I moved it a little from the edge. I can make one out of 3/4" brass. Need to get a set screw, just used a M6 SHCS to set it up.

Next is to figure out where the bar goes and gives me sufficient room for the clamp screws. I'll measure stuff carefully and work out where to start drilling the initial hole for the bar.

I'm thrilled that it's beginning to start looking like a holder. Literally sweated over this, not so much the machining, but it really was hot in the shop. Thanks for the helpful suggestions so far.