whats your favorite crowning tool
- Thread starter skeetlee
- Start date
JerrySharrett
Senile Member
Use a sharp, lipped HSSCo.
Since you are determined to use some inserts, for threading use an on-edge triangle in the TPMC-32NV or TPMA-32NV in a non exotic grade like a C-2 or C-5.
For crowning get Sandvik/Coromat's C-1105 grade in an 80 degree or greater diamond;
(their words, not mine)
GC1105 is available in many different insert geometries from edge rounded inserts for first stage machining to razor sharp edge inserts for last stage machining.
Razor sharp!
Where minimal deformation to the component is critical, we offer razor sharp ground G-tolerance T-Max P and CoroTurn 107 inserts to meet the esential criteria for a quality surface finish.
Minimized distortion and burr formation.
Smoother surface in precision cast components where ‘orange peel’ is a problem.
Excellent in finishing of thin walled components.
Reduced degree of taper and ‘push off’.
Enables precision machining when longer overhangs can not be avoided.
http://www.coromant.sandvik.com/
Since you are determined to use some inserts, for threading use an on-edge triangle in the TPMC-32NV or TPMA-32NV in a non exotic grade like a C-2 or C-5.
For crowning get Sandvik/Coromat's C-1105 grade in an 80 degree or greater diamond;
(their words, not mine)
GC1105 is available in many different insert geometries from edge rounded inserts for first stage machining to razor sharp edge inserts for last stage machining.
Razor sharp!
Where minimal deformation to the component is critical, we offer razor sharp ground G-tolerance T-Max P and CoroTurn 107 inserts to meet the esential criteria for a quality surface finish.
Minimized distortion and burr formation.
Smoother surface in precision cast components where ‘orange peel’ is a problem.
Excellent in finishing of thin walled components.
Reduced degree of taper and ‘push off’.
Enables precision machining when longer overhangs can not be avoided.
http://www.coromant.sandvik.com/
JerrySharrett
Senile Member
jackie schmidt
New member
I do not use inserts for crowning. Like Jerry, I use a positive rake tool with a hooked lip.
Lee, as you get more experience, you will just know when a tool is cutting correctly, and learn to modify your choices and decide which type of tool is best for what ever application you need it for.
Lee, as you get more experience, you will just know when a tool is cutting correctly, and learn to modify your choices and decide which type of tool is best for what ever application you need it for.
I dont have to use an insert at all. I dont have enough lathe time to make any claims as to what i do like. What i do know though, is that i need to get something that will work, so i can start making mistakes. LOL!! I always learn a little something from my mistakes. I just dont want them to cost me a bunch of money!! Thanks fellas, now i have some choices. Lee
JerrySharrett
Senile Member
From left to right;
Tool 1 - triangular threading insert (this one is a TNMC-32NV grade V5)
Tool 2 - HSSCo, hand ground with positive top rake for threading
Tool 3 - HSSCo hand ground for roughing the crown down to the last 0.005"-0.010"
Tool 4 - HHSCo hand ground and honed really sharp to take the finish cut(s)
(As you can see I don't see very well anymore by the many passes on the top lip of tool 4)
image host
Thanks a bunch Jerry.
I need to ask one more thing. I cant find any brass inserted screws to build my spider with. anyone know were i might buy something like that? I have my back plate here so we are going to drill and tap to make the spider. I just need to find some screws so we know what size to tap this plate. Thanks Lee
I need to ask one more thing. I cant find any brass inserted screws to build my spider with. anyone know were i might buy something like that? I have my back plate here so we are going to drill and tap to make the spider. I just need to find some screws so we know what size to tap this plate. Thanks Lee
T
tech-shooter
Guest
Lee:
I used 1/2# sections of #4 copper ground wire from the hardware store, epoxied into holes drilled into the ends of 3/8"X24 capscrews. Pictures on my tooling page here:
http://www.the-long-family.com/tooling.htm
I could have machined some inserts from brass rod, but the copper was faster to make. They have held up really well so far. IIRC, the oxide coated screws were pretty hard, and I had some difficulty drilling them with HSS brill bits. Had to go slow and use lots of oil, and snuck up on the ID using multiple drill sizes.
Cheers,
Chris
www.the-long-family.com
I used 1/2# sections of #4 copper ground wire from the hardware store, epoxied into holes drilled into the ends of 3/8"X24 capscrews. Pictures on my tooling page here:
http://www.the-long-family.com/tooling.htm
I could have machined some inserts from brass rod, but the copper was faster to make. They have held up really well so far. IIRC, the oxide coated screws were pretty hard, and I had some difficulty drilling them with HSS brill bits. Had to go slow and use lots of oil, and snuck up on the ID using multiple drill sizes.
Cheers,
Chris
www.the-long-family.com
Jerry,
On your hand ground threading tool, how do you keep 60 degrees with that positive top rake?
Your crowning tools kinda look like something you would use to turn aluminum. Interesting. My crowning tool looks like a RH turning tool, but with the bottom ground away for clearance. It's honed and dead sharp. It has always produced clean, burr-free crowns, but I'm gonna grind one up like yours and give it a try.
Have you (or Jackie) ever crowned with a tool similar to mine, and if so, how did the crown compare to crowns cut with your present tools?
Thanks,
Justin
On your hand ground threading tool, how do you keep 60 degrees with that positive top rake?
Your crowning tools kinda look like something you would use to turn aluminum. Interesting. My crowning tool looks like a RH turning tool, but with the bottom ground away for clearance. It's honed and dead sharp. It has always produced clean, burr-free crowns, but I'm gonna grind one up like yours and give it a try.
Have you (or Jackie) ever crowned with a tool similar to mine, and if so, how did the crown compare to crowns cut with your present tools?
Thanks,
Justin
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I do it a little differently.
I use HSS only for barrel work. I picture my cutter edge to be working like a miniature plow share slicing into the piece, curling the material away cleanly while exerting no "IN" or "OUT" pressure on the work surface. (For this reason I don't use carbide except to hawgg.....)
So..... crowning.
#1, it's done BACKWARDS.....
#2 it's done with FAST rev's and low rate of travel......
By backwards I mean I run the lathe in forward gear but grind the bit to cut TOWARDS ME from the bore outward, also that the bit be shearing the steel in such a way that it pulls it away from the bore as it leaves. When I'm done I've left a knife edge that'll easily peel fingernail.
By fast I mean 1000-1400rpms and low feed rate and take a really thin slice, the hair you get will be thin as cobweb and dangerous as an asp. DON"T TOUCH IT!!!
the things you'll have to learn by trial and error are just how fast you can set your feed VS depth VS rpm's and keep the bit "in" but not overheating. BUE (Built Up Edge) and discolored or "burnt" cutting edges are signs that you're making heat faster than the pieces can cool. You need to decrease speed, decrease feed, decrease cut or add coolant (air/water/oil) to get rid of excess heat.
BTW, don't be afraid to center up the bore by eye...... no matter what the dial sez, be sure the cutter's hitting all the grooves at the same time.
al
I use HSS only for barrel work. I picture my cutter edge to be working like a miniature plow share slicing into the piece, curling the material away cleanly while exerting no "IN" or "OUT" pressure on the work surface. (For this reason I don't use carbide except to hawgg.....)
So..... crowning.
#1, it's done BACKWARDS.....
#2 it's done with FAST rev's and low rate of travel......
By backwards I mean I run the lathe in forward gear but grind the bit to cut TOWARDS ME from the bore outward, also that the bit be shearing the steel in such a way that it pulls it away from the bore as it leaves. When I'm done I've left a knife edge that'll easily peel fingernail.
By fast I mean 1000-1400rpms and low feed rate and take a really thin slice, the hair you get will be thin as cobweb and dangerous as an asp. DON"T TOUCH IT!!!
the things you'll have to learn by trial and error are just how fast you can set your feed VS depth VS rpm's and keep the bit "in" but not overheating. BUE (Built Up Edge) and discolored or "burnt" cutting edges are signs that you're making heat faster than the pieces can cool. You need to decrease speed, decrease feed, decrease cut or add coolant (air/water/oil) to get rid of excess heat.
BTW, don't be afraid to center up the bore by eye...... no matter what the dial sez, be sure the cutter's hitting all the grooves at the same time.
al
JerrySharrett
Senile Member
As to the threading tool, just use a thread gage and view the tool from the top to maintain profile. Actually just grind the tool normally then rake the top. Remember with the compound at 29.5 degrees just the front edge is all that is cutting so you are are generating the thread form.
As to roughing the crown, I use several. The tool pictured is just one I used at the time. Most of those tools look just like my crown finishing tool except with more nose radius. The important thing is to take the last few thousands with a tool sharp enough to cut freely.
Al,
I do mine similar to yours. HSS, fed from the bore out. Seems to work just fine. Never spun one as fast as you, though.
All my crowning tool does is cut crowns. As soon as it's work is done, back in the Gerstner it goes.
Jerry,
I thread with the (GASP!) cross-slide...no compound. I'm not sure I could make that threading bit work like you can.
Justin
I do mine similar to yours. HSS, fed from the bore out. Seems to work just fine. Never spun one as fast as you, though.
All my crowning tool does is cut crowns. As soon as it's work is done, back in the Gerstner it goes.
Jerry,
I thread with the (GASP!) cross-slide...no compound. I'm not sure I could make that threading bit work like you can.
Justin
JerrySharrett
Senile Member
Something many new gunsmiths don't realize, your half-nut and thread screw contains a lot of "slop". Feeding straight in, you may not be cutting a constant pitch thread. Setting the compound on 29.5 only one side of the threading tool is actually removing metal. The other side is creating a back-load that keeps the slack in that half-nut/lead-screw going in the same direction.
What this means, simply, your threaded joint (tenon) will not be making full contact throughout the entire assembly.
JerrySharrett
Senile Member
Same situation exists here. If no back-load is present, the carriage, driven by the lead screw, is free to wander.
4
4Mesh
Guest
Jerry,
do you have a source for Sandvik inserts other than buying from DGI supply? I have a few holders I'd like to get some inserts for, and vice versa, but they're borderline-outrageous on price.
do you have a source for Sandvik inserts other than buying from DGI supply? I have a few holders I'd like to get some inserts for, and vice versa, but they're borderline-outrageous on price.
JerrySharrett
Senile Member
Sorry, but no. I don't use them anymore.
Edit-
I need to clarify this. Before I retired one of my functions was called "tooling development". In that I looked into a lot of different types of cutting tools for many applications, milling, drilling, turning, etc. At that time we were using many thousands of carbide inserts ,mainly in turning and milling. We bought a few hundred thousands of dollars of this tooling each year. Valenite, Kennametal and Sandvik, mostly bid on these annual " contracts to supply". Sandvik had the best products for low stress metal removal. Low stress metal removal meant machining without pushback from the workpiece (like you would have taking a turning cut from thinwall Inconel tubing for example).
After I retired and using a tool room class lathe I very quickly found out that carbide insert tooling was not the best way to go on these low horsepower machines and machining light amounts of metal as in, for example, turning a tenon. After all it just takes 3 cuts to go from 1.210 to 1.06" and get a close tolerance measurement and good finish. Making a too-long story shorter, nothing wrong with Sandvik super sharp inserts, I just don't feel the need for them for barrel work.
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pbike
New member
As of this year, Production tool is adding Sandvic / Coromant to their line of insert tooling. They have had in the past an agreement with Valenite / Walter, but both parties part ways (pun intended) this year. So the new 2012 Production tool catalog will have Sandvic coromant in it... Which is exciting since I get a healthy discount there.
Paul