Thread: custom lathe tool
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05-30-2019, 02:47 PM #21
I think Sami was offering to grind it for you for $150.
You could do what is essentially a parting cut using a .050 square-ended tool ... but keep in mind tha your tolerances call for the diameter at the bottom to be .030-.050. Especially for a newbie with "not much of a lathe" to work with, awfully likely that you'd wind up with something larger than .050 if that is the size of your tool.
Why not make a tool .040 wide and put a radius on it. Your tolerances are such that it does not appear that a perfect radius is required, so long as the overall width stays within .030-.050. Rather than a form tool to cut the angled sides, just set the compound to cut the angles and make two passes.
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05-30-2019, 04:05 PM #22
I used to make form cutting tools. I think a full form would not work in any kind of plastic. There is just too much area to cut so even a .001 in-feed would be to much stock to cut. Plus you would need positive rake all around the cutter..
Going to depth with a parting tool , and then cutting the two 15* sides one at a time with the likes of a single point tool bit may be the best way to go. Yes the compound at 15* this way and then at 15* the other way so you might shave .015 or so per pass.
Parting tool .050 could have the .025 radius
Figure 3/16 on one side and 3/16 on the other side and .050 that is almost 1/2 inch of in-the-cut x .001 of in-feed is more that many machines will cut.
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05-30-2019, 08:36 PM #23
would this work for me if I get the tip radiused?
45621 Solid Carbide 30 Degree Engraving 0.035 Tip Width x 1/4 Inch Shank Signmaking
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05-30-2019, 09:25 PM #24
the radius is for stress relieving to prevent cracks, the cable only rides on it, like the elevator sheaves the traction is from side load and flex/lack of flex of pulley/cable (same as v belts, morse taper tools, ect.). a .0625 cable will not sit in a .04 hemisphere, it sits on a .04 hemisphere.
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05-31-2019, 12:58 PM #25
I think that a parting tool is the way to go, now I need to get this tool radiused and profiled.
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05-31-2019, 02:14 PM #26
I think a few here are having a problem reading the numbers on that dwg. :-)
...lewie...
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05-31-2019, 02:55 PM #27
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06-03-2019, 09:39 PM #28
Yeah, I discovered that after I posted the link. Local tool grinder quoted me $67 to build me one and he is supplying the cutter. Now I need to make a mandrel to put in my 5c closer.
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06-03-2019, 10:08 PM #29
This is kinda like a pulley grooving tool.... oh wait it is a pulley groover just not steel being cut so different clearance and rake.
Just curious is the $67 carbide or HSS? Top hook or other? This material likes very high shear plane angles.
Thats a real decent deal as my setups would eat that price tag for lunch and still be hungry.
Bob
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06-04-2019, 11:23 AM #30
just a thought and coudl be totaly wrong what if he had the parting tool and then a left and right side tool ground that way with a QCTP you could swap them out faster then adjusting the whole tool pos for left and right side cuts
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06-04-2019, 12:01 PM #31
When I get stuff like this I almost always redraw it, for the radius I draw the two side angles hitting a flat root at the bottom of the intended radius. Then a circle tangent to the sides and root. 99/100 (or more) it's "perfect" as the radius there is just a clearance anyway. If it's a functional radius and customer sent a dumb drawing then yes a call is in order. Doesn't always clear things up but it'll CYO a little at least!
For something like this pulley I'd probably chop out a simple brass gage and 3 HSS tools for sides and root. Easier to measure the male part.
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06-05-2019, 02:22 AM #32
I would assume it is HSS. I wish I had a picture to see so I can get it in my mind how the cutter is supposed to be set up to cut phenolic. I just looked at 2 of the pulleys that I bought from someone, they just used a threading tool to cut the groove. Not to spec and I think the cable will slip in short order. What about using a custom ground threading tool that will fit my BXA tool holder vs. the parting tool holder.?
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01-09-2021, 07:23 PM #33
I know that this is an old thread, I wound up getting a glass impregnated phenolic and it may be tougher to cut than I expected. There is a local machinist who says that he is willing to try to make the pulleys, I still really need to decide if I make a .040 wide radius straight tool and then a finish cut with the 15 degree tool or if I can just cut it with the 15 tool.
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01-09-2021, 08:39 PM #34
Qt ; [I still really need to decide if I make a .040 wide radius straight tool and then a finish cut with the 15 degree tool or if I can just cut it with the 15 tool.]
You might make/grind a parting blade to the width and radius..easy on a bench grinder.
And then come in on each side to single-point using the compound for 15* right and then left angle to intersect the radius.
If needing only a few pulleys this may be best/Ok.
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