Post By bosleyjr
Milling V-Grooves for tube mitering fixture
I've been making small fixtures for holding bits of bicycle tubing for mitering operations.
My method has been "stick a 45d angle in the vise and then mill the length of the block with an endmill"
Yeah, it makes something that looks like a 90d notch in the stock.
But I want to be able to do this operation with a lot more accuracy. I want to get the bottom of the v precisely in the centerline of the block, and I want the notch to be symmetric.
I know this is apprentice-level work at-best. Do you guys have any advice on how to do this job more accurately and more controlled w/ the tools I have? (a vise, an edge-finder, an adjustable angle support block, some milling bits, and the DRO).
I want to learn to make arbitrary notch angles with good placement accuracy with those tools. I don't want to pay 200$ for some custom notch-eating bit.
Well, I found one answer here: Vertical Milling of the Clamp Details Details 9 and 10 - V-Groove : Blue Ridge Community College : Free Download & Streaming : Internet Archive
The guy just uses some dykem and simple geometry to do it.
This is actually probably good enough for my specific project.
But I thought I heard him say the tolerance was 1/10'000th" I cannot imagine how this technique is accurate enough for that. The scratched line itself wouldn't even be that tight.
Still wondering if there are other techniques.
I'm pretty sure he said the tolerance is 10/1000 (ten one thousandths) which some folks abbreviate by saying "ten thousandths" since most of the time it's not ambiguous (think "seven thousandths" or "25 thousandths").
Start with an over size block. After the vee is milled put an accurate rod in it and indicate/mill it centered and squared. Mill block to size after it is squared/centered................Bob
Instead of a 90* V I would think a 120* V would be be a little easier for holding various sizes of tubing. You can get a larger range of tubing without as much of height on the V-block.
Can you tilt/nod the head of your mill or are you stuck with angle plates?
Typically in Vee blocks, you put a small square groove in the bottom. Like 1/32 wide by 3/64 deep (guesstimate is from memory, so take with a grain of salt). If this is acceptable, this should be doable with one assumption. That is, I'm assuming that you have an accurately made block that is square and uniform in dimensions. If so, then make a fixture to hold the block at a 45° angle. Rough mill the groove, then use a sharp, accurate end mill for a final pass, but then reverse the block for another final pass.
You may have a very small ridge in the bottom of your vee. If so, tweak your fixture and remill until you get rid of this, or, put the block in a mill vise and run it through a horizontal mill to cut a small groove. In either case, because the process is symmetrical, and your block is true, the sides should be symmetrical and the vee groove should be on center.
EDIT: Upon thinking about this, if you use a mill, you ALWAYS should have a ridge, because if you don't, the mill would be hitting both sides of the vee. That's the point: you want the mill to do one side, then when you switch and do the other side, it's exactly symmetrical. But it leaves the ridge, which you get rid of with a slitting saw or very thin milling cutter.
BTW, here's a hint I hope is handy: To make the degree symbol, °, hold down the Alt key, and type 0176 on your keypad. Et voila!
Last edited by bosleyjr; 07-16-2012 at 12:43 PM.
Hint Follow-up: ALT + 248 (on the number pad) does the same... and it's one less number! °!
Originally Posted by bosleyjr
Hey, but I get my ° for 72 cent cheaper! Thanks Royaldean
Originally Posted by Royldean