Cutting Points - up vs down, climb vs conventional

[dchristal]

I have a milling machine set up to cut points using a double angle side cutter. In my mind, it seems that I should only use climbing cuts as a conventional cut might tend to tear out the workpiece. Further, I only climb up out of the groove rather than climb down toward the A joint area.

Yesterday I watched a video on cutting points where a deep rough conventional cut from A-joint to main-joint was followed by a fine climbing cut back down into the groove. This is much faster than what I do and yielded good results on the video, but I'd like to better understand the error of my ways.

How do you guys do it?

 

[Tony Zinzola]

I use my mill with something like an 80 tooth blade. I cut in both directions. Never had a problem unless it's due to my own stupidity such as not locking the indexer as I did yesterday, ruining a gorgeous piece of Brazilian Rosewood.

 

[qbilder]

I cut from the "A" joint out, and then back in. I don't readjust the cutter depth on the reverse cut. It is only a "cleaning" cut that basically does just that, cleans the cut surface up.

 

[fugdbdt]

I am curious as well. Cue woods are so hard that i allways burn the cut and dull bits easier on climbing cuts with a router. Probably not an issue with your milling machine. I do like the climbing finish idea though. But i allways liked decending cuts because they seem to help me make up my mind how long i want the points to be on each piece.

 

[Dave38]

Not to sound stupid, what is a climbing cut? I have done my point cutting attemps with the 'a' joint end of forearm on the tailstock side with an offsettable boring head on it, and ran the router from left to right. The cuts have been very clean and sharp, but I take only a little off at a time.
Dave

 

[MVPCues]

Not to sound stupid, what is a climbing cut? I have done my point cutting attemps with the 'a' joint end of forearm on the tailstock side with an offsettable boring head on it, and ran the router from left to right. The cuts have been very clean and sharp, but I take only a little off at a time.
Dave

http://www.hanita.com/hanita_protected/tec00006.htm

conventional= walking forward scooping with a shovel.
climb = walking forward holding a tiller.

 

[Rybord]

Not to sound stupid, what is a climbing cut? I have done my point cutting attemps with the 'a' joint end of forearm on the tailstock side with an offsettable boring head on it, and ran the router from left to right. The cuts have been very clean and sharp, but I take only a little off at a time.
Dave

Cutting in at the deepest portion " A joint " and cut to the point until the tool clears the work piece. From deep to shallow.

 

[rhncue]

Cutting in at the deepest portion " A joint " and cut to the point until the tool clears the work piece. From deep to shallow.

I have the A-joint end in my indexer and the joint end in my center. I cut in both directions until I get close to my finished depth and then I climb mill only. On my final two passes I take a .020 cut and the final a .010 cut.

Dick

 

[BarenbruggeCues]

http://www.hanita.com/hanita_protected/tec00006.htm

conventional= walking forward scooping with a shovel.
climb = walking forward holding a tiller.

Nice article..........it explains about everything you need to know about milling and cutters and deflection of the cutters.

My question is though.....if your standing in front of the mill and your double angle cutter is turning in a clockwise rotation......which side of the table is the A joint of the forearm? Left or right. It'll make a diff if your climbing or conventional cutting for the milling op.

I just spend the better portion of a month rebuilding indexing and point cutting fixtures so I can use a high speed cutter canted at a 45. I was just thinking of this same thing....which way would be best to go.

 

[MVPCues]

Nice article..........it explains about everything you need to know about milling and cutters and deflection of the cutters.

My question is though.....if your standing in front of the mill and your double angle cutter is turning in a clockwise rotation......which side of the table is the A joint of the forearm? Left or right. It'll make a diff if your climbing or conventional cutting for the milling op.

I just spend the better portion of a month rebuilding indexing and point cutting fixtures so I can use a high speed cutter canted at a 45. I was just thinking of this same thing....which way would be best to go.

If the cutter is turning clockwise, and you are cutting right to left, it is climb. If you are cutting left to right, it is conventional. Which end the A joint is at does not change that.

Remembering a conversation with a friend, the "proper" way to do this cutting is climb milling. Another general rule is cut from the strongest position to the weakest, or cut so that the depth/severity of the cut decreases as you go. That would seem to indicate you should cut from the joint end, but it is 50/50 since by the time you mill out two Vee grooves, it is a toss up which end is offering the stronger position, ie unless you have wide gaps between the bases of the points, the joint end becomes pretty weak.

In the end, the type of setup and cutter, clearance, feed rate, etc will yield different results. The best way to go is the one that yields the best results (I am good at pointing out the obvious heh?)...but when it makes a difference, it seems to me climb milling has been better in what I have done.

Kelly

 

[rhncue]

If you are using a shovel to scoop dirt out of a trench you are conventional milling, If you are using a pick or a mattocks to loosen the dirt you are climb milling.

Dick

 

[BarenbruggeCues]

If the cutter is turning clockwise, and you are cutting right to left, it is climb. If you are cutting left to right, it is conventional. Which end the A joint is at does not change that.

I understand that...but some of the responses just said that they were cutting from the A joint to the tip of the point ....so I'm thinking it would make a difference if they were climbing or conven depending on which side the A was.

Remembering a conversation with a friend, the "proper" way to do this cutting is climb milling.

I've been told and from experience have found the same when cutting aluminum. I get the better surface finish when cutting a climb.

Another general rule is cut from the strongest position to the weakest, or cut so that the depth/severity of the cut decreases as you go. That would seem to indicate you should cut from the joint end, but it is 50/50 since by the time you mill out two Vee grooves, it is a toss up which end is offering the stronger position, ie unless you have wide gaps between the bases of the points, the joint end becomes pretty weak.

In my designs I leave a bit of a space between the points at the base. I try to get them as close as possible but my forearms are buried into my handles so getting them real tight is not a necessary option for me. I know some cut in 2 points 180 degrees opposite and then glue in stock and cut the other two.

In the end, the type of setup and cutter, clearance, feed rate, etc will yield different results. The best way to go is the one that yields the best results (I am good at pointing out the obvious heh?)...but when it makes a difference, it seems to me climb milling has been better in what I have done.
I have to agree with the climb style cut. I know when using a smaller cutter in the alum the climb has a tendency to push off the material being cut and the conventional does just the opposite and wants to dig in.

Kelly

I'll have to do some experiments with plunging into the A side of the forearm and climbing out to the point tips with the router bits. Not sure how a straight flute bit will plunge at a 45. I have to believe it should take it OK if I don't go too deep per cut.

Thanks for the insight.........

 

[rhncue]

I'll have to do some experiments with plunging into the A side of the forearm and climbing out to the point tips with the router bits. Not sure how a straight flute bit will plunge at a 45. I have to believe it should take it OK if I don't go too deep per cut.

Thanks for the insight.........

I'm sure you will have no trouble. Diekman, as you well know, does it this way with the router set at a 45 deg.

Dick

 

[BarenbruggeCues]

I'm sure you will have no trouble. Diekman, as you well know, does it this way with the router set at a 45 deg.

Dick

Actually I didn't know that. But thanks for insight. Maybe I did know that and just forgot it though.

On another note......I've done a little searching but can't seem to find any thing out on this.
Does anyone know the math formula for sweeping an indicator on a sine bar to set up a desired angle on a milling head?

 

[dchristal]

Does anyone know the math formula for sweeping an indicator on a sine bar to set up a desired angle on a milling head?

I don't have a tilting head, but if I did, and wanted to use a sine bar to set the angle, I think I'd arrange the correct amount of blocks under one side and look for zero deviation along the bar. In short, I don't think I'd be looking for a formula.

I apologize if this is completely off the mark. Thanks to everyone for your input.

 

[brianna187]

How i do it

The cutter comes in at the a joint and exits 10" at 0.... then does the same thing 4 times on the last pass it takes 20k then it indexs 90 degrees and does the sme thing after 4 locations it returns to zero less then 7 min.to do a forarm. prefect cut every time will are having these cutters made and will have them in about 6 weeks you can check our web site

 

[rhncue]

Actually I didn't know that. But thanks for insight. Maybe I did know that and just forgot it though.

On another note......I've done a little searching but can't seem to find any thing out on this.
Does anyone know the math formula for sweeping an indicator on a sine bar to set up a desired angle on a milling head?

Sorry, after I read that statement that I wrote I realized that I should have said "Diekman, as you are probably aware". The film I had, on building points, was purchased in 92 or 93 from Dennis. He had the set-up in a lathe, not a mill however. He had a bracket made that held the router at a 45 deg. angle using a 5/8 straight router bit for cutting V grooves. This was mounted on the compound. This arrangement will work well as long as all movement from vibration is eliminated. I used to cut my V's on the lathe but I used a 90 deg. V cutter and went straight in from the side. This is a poor way of doing it I found as the very bottom of the V doesn't get cut sharply because the very bottom of the bit is innefficient. The way you are considering and using a router bit where the outer circumference is in motion so that the bottom of the V is cut cleanly are, by far, the best solutions although there are, I'm sure, many others. The nice thing about your set-up, although more difficult to build the jig, once done, the bits are much cheaper and easier to find.

Dick

 

[cutter]

cutting points

Actually I didn't know that. But thanks for insight. Maybe I did know that and just forgot it though.

On another note......I've done a little searching but can't seem to find any thing out on this.
Does anyone know the math formula for sweeping an indicator on a sine bar to set up a desired angle on a milling head?

Dave,
Too bad Chester has gone away, he could spend two days telling you how to set up the sine bar. Comes down to length of the sine bar, then I believe it's the cosine of the angle you want to use that determines the height of the blocks you put in. Pain in the butt to set up. My bridgeport tends to drift a little left and right as I crank in the angle, so not only are you working the angle of the head you are fighting to keep it square with the table. Then comes the fun of getting the cutter height correct. But all said and done, when you get it right, I believe it is the best way to cut deep points. I use a shell mill that was designed for aluminium. Razor sharp. And of course, as soon as you get it set up, along comes something else that you want to do on the mill. Picture on my website/ shop page with the head cranked over.

If you ever saw Diekmans tapes, you would die laughing, He used 2 by 4's to mount things and measured depth by counting turns on his cross slide.
Nothing like using 4 turns on the cross slide for a reference.

Getting back to climbing and conventional milling. All those articles are written for metal workers. A forearm will flex more than the cutter will deflect, no matter which way you go about it. Especially if you do it between centers, and who knows how the 4th point will react with all the wood already removed from the other 3 points. I personally think that as long as you did it the same for each point, it doesn't matter which way you do it.

 

[brianna187]

after its turned

another shot after we glue in and turn down

 

[conetip]

A sine bar is called that because you use the sine of the angle to get the stack height for the bar. They are normally whole number of inches in length to the center line of the rollers. EG 4.000 inches or metric 100.00 mm long. You do the sine of the angle , like say 5 sine,0.0871557 then x length of bar say 4.0, = 0.34862 . This is the amount needed to be stacked under 1 end to make the angle. Then when the indicator on the top of the bar is zero the angle is correct.When using on a lathe is tricky as you need the bar to be at 90 deg. I use magnets to hold the gauge blocks in place and a stack of parallel blocks to keep it at 90 deg to the saddle.