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View Full Version : How do (side,front)(relief,rake) angles differ between lathes and shapers?



Elninio
02-25-2011, 04:57 PM
How do (side,front)(relief,rake) angles differ between lathes and shapers? How are these angles calculated in the first place (I guess they were found by trial and error), and does cutting speed affect the angles?

ammcoman2
02-25-2011, 07:32 PM
Basically the same as for a lathe toolbit except for front clearance. 3 degrees for a shaper and about 7 for a lathe. For fine finish work I like to use a radiused tool bit with lots of side (20 degrees) and back rake (about 10 degrees).

I suspect the size of the shaper would allow for some variance - mine is an Ammco (as you may have suspected!!!)

Geoff

Forrest Addy
02-25-2011, 07:47 PM
How I grind a HSS cutting tool for a lathe, shaper, planer whatever depends on what I want the tool for: what material, part senitivities, etc but generally I grind them about the same angles.

I usually start with 7 degrees clearance all around, a nose radius of 4 x the feed rate, and no top rake HSS or carbide. Add top rake, chip curler (VERY seldom), etc as conditions develop. Stone clearance angles to remove grinding marks and to smooth the cutting edge and try to align the top rake finish parallel to the chip flow.

Break the keen cutting edge about 1/6 to 1/10 the feed rate if mill scale, hard material, interrupted cut are part of the problem. The edge radius acts like the radius on the edge of a sidewalk: keeps it from crumbling.

Black_Moons
02-25-2011, 09:02 PM
A little breif on rake angles:

0 rake seems to cut just about everything. Might not give the best finish, but it won't dig in on grabby materials, and won't snap off/chip easily on harder materials.

Back rake, (Sloped back from the tip to make a sharp knife like edge) Makes the bit cut easily, But makes it more fragile, It also makes it more likey to dig in on some materials. Digging in usally causes serious failures unless its limited by the clearance angle.. But back rake is best avoided on any material that grabs. (IIRC copper and brass are such materials that dig in when given backrake)

Forward rake, (sloped forward to the tip, producing a fat wedge shape) Produces a bit that is harder to cut with, But is much stronger due to more material to take the force, and to absorb heat away from the tip. Good for hard materials where back rake would dull/chip quickly. Good for interrupted cuts as well.

Side rake functions similar to back/forward rake, depending on the side of the bit you are cutting with, But helps deflect the chips in a diffrent direction, And can adjust the cutting forces angle. Some materials seem to perfer more siderake then back rake, and others its the other way around. Some perfer no rake.

Elninio
02-25-2011, 09:23 PM
Basically the same as for a lathe toolbit except for front clearance. 3 degrees for a shaper and about 7 for a lathe. For fine finish work I like to use a radiused tool bit with lots of side (20 degrees) and back rake (about 10 degrees).

I suspect the size of the shaper would allow for some variance - mine is an Ammco (as you may have suspected!!!)

Geoff

For finish work, is that what they call a 'shearing tool', or is that something different? I've seen pictures of it, I suppose the only difference is a huge side rake, which side of the side rake does it cut with?

.RC.
02-26-2011, 12:16 AM
A little breif on rake angles:

0 rake seems to cut just about everything. Might not give the best finish, but it won't dig in on grabby materials, and won't snap off/chip easily on harder materials.

Back rake, (Sloped back from the tip to make a sharp knife like edge) Makes the bit cut easily, But makes it more fragile, It also makes it more likey to dig in on some materials. Digging in usally causes serious failures unless its limited by the clearance angle.. But back rake is best avoided on any material that grabs. (IIRC copper and brass are such materials that dig in when given backrake)

Forward rake, (sloped forward to the tip, producing a fat wedge shape) Produces a bit that is harder to cut with, But is much stronger due to more material to take the force, and to absorb heat away from the tip. Good for hard materials where back rake would dull/chip quickly. Good for interrupted cuts as well.

Side rake functions similar to back/forward rake, depending on the side of the bit you are cutting with, But helps deflect the chips in a diffrent direction, And can adjust the cutting forces angle. Some materials seem to perfer more siderake then back rake, and others its the other way around. Some perfer no rake.

To me that just makes everything so confusing calling everything some type of rake...

To me rake is always the cutting edge only, which can vary in position on a lathe tool depending on whether it is for facing or longitudinal turning...

J. Randall
02-26-2011, 12:24 AM
To me that just makes everything so confusing calling everything some type of rake...

To me rake is always the cutting edge only, which can vary in position on a lathe tool depending on whether it is for facing or longitudinal turning...

RC, not confusing to me at all, although I think of them as positive, or negative, and side rake. Anything that is not on the top of the tool, is a clearance angle, works for me.
James

ammcoman2
02-26-2011, 10:45 AM
" For finish work, is that what they call a 'shearing tool', or is that something different? I've seen pictures of it, I suppose the only difference is a huge side rake, which side of the side rake does it cut with? "


yes, I think you are correct. As far as which way to cut - I have found that it doesn't seem to matter. Perhaps something to do with the very light cuts one makes with this tool. If one used this shape on a lathe the leading face would be low.

Geoff

Elninio
02-26-2011, 11:07 AM
Geoff, do you have a photo album of your shaper, and associated projects?

mc_n_g
02-26-2011, 02:15 PM
Back rake will tend to induce chatter on smaller shapers. I like to use only shearing type tool bits. I grind the cutting surface 30-45 degrees from side to side (looking from the end makes the tool look like a triange shape or a wedge). Make them for both left and right directions. Four roughing I normally have an approximate 30 degree angle rather than a 90 vertical cutting edge. I only use a near verical cutting edge when I have to reach into a corner, etc.
I use a well rounded shearing tool for finishing cuts if needed. Just a light 0.002-0.010" cut and it just peels of in nice curls.
The finish on an 8" logan shaper. (it is loud becuase the video camera picks up wasy too much sound and the motor plate is beginning to vibrate, rubber mounts disintegrated over time)

http://www.youtube.com/watch?v=5hY6UGMUG3k

Elninio
02-26-2011, 02:33 PM
Are you saying your roughing tool has 30-45 side rake, and 30 back rake? What about relief?

mc_n_g
02-26-2011, 04:29 PM
No just ground at an angle of about 30-35 degrees. The relief rake is still standard to clear the material. I do not put any intentional back rake on the tool. The may be 1 or 2 degrees from grinding it but nothing I intentionaly grind into it.