Cutter to Use on Deluxe Lathe

[opiesbro]

Chris - Does using router bits help avoid the push off?

Chris

I have made like 4 cues like this before I got my deluxe and a router. The router is way better. For instance I tried to retaper a cue that was made by cutting it with a qctp and carbide tool out of solid birdseye with phenolic joint and butt collars. It was a little big to start with in diameter so I thought I would try to turn it round with my router and taper bar. Yeah right!! That thing was so egg shaped from the push of the tool that it was about the size of a shaft by the time it all came out. I was so pissed and now I'm in the process of making him a new one to replace it.

About a month ago a customer had an extra shaft from JOSS that he wanted a nice sneaky butt for it. I retapered a blank from from Schmelke and it was perfectly round with no visible run out at the tip when laying the joint on a rail and turning. I could have never done that good of work just by using the qctp and a carbide or HSS tool.

 

[ChampionsRepair]

Most run-of-the-mill routers have fixed speeds, and would require some sort of external control to change that. Not MY routers, since I use variable frequency drives throughout the shop, but most of those used on the home/hobby equipment prevalent around these parts are not easily set up for Precise (pun intended) rpm control. More importantly - your argument notwithstanding - trial and error experimentation can still result in a feedrate/headstock-rpm ratio that will balance with a particular router head speed, and usually the feedrate & headstock are more easily controlled.

Does every post you make need to contain the assertion that the tools or abilities of others are inferior to your own?

Cutter mass is irrelevant. It's the size of the cutting edge [presented to the work surface] that determines stock pushoff. Presumably any decent shaft turning setup will have a very rigid cutting spindle, so the only thing to push the shaft away (instead of cleanly cutting it) would be the resistance of the wood surface to the penetration of the cutter. Beyond any shadow of a doubt, the smaller and sharper the cutting edge is the more easily it will penetrate the wood (rather than push it away).

Mass [of the cutter] has NOTHING to do with it.

Your assumption of 100% cutting efficiency is impossible. The laws of physics apply to even you, Thomas. The math involved in calculating the unintended dynamic forces transferred to the workpiece is beyond my abilities also. But denying that they exist is naive and, or ignorant. Mass is not irrelevant, nor is the surface area at contact as you have suggested.

I still don't get how the weight has any impact on how clean the cuts are.
Table saw blades are a ton heavier but at 1/8 kerf, they have less pushoff than the regular wing cutters I think due to frequency of cuts.
Wing cutters' interrupted cuts ( the contact with wood has an interval ) might be another factor how clean the cuts are.
I get mine grind with a little relief so the tips " scoop " on the wood instead of gouging it. But that can be just mental.

Weight is only one variable of the equation. By reducing both the mass and velocity when using a smaller diameter cutting tool, you are reducing the overall force transferred to the workpiece. With the assumption of the same surface speed of the cutting bit and the same efficiency of cut in tool design, the unintended off axis force transferred to the workpiece will be reduced. As cutting force is also reduced, there will be a point of diminishing returns when other issues can be introduced into the process.

I would only be speculating as to why saw machines result in less push off. But, I am willing to suggest that the rigidity of the machine, the lower rpm, in general, of the cutting tool, and narrow kerf would be the most obvious reasons. I believe that it is also a consensus among makers tapering with a table saw that blades having approximately 60 teeth perform better than blades having 80 teeth or more. This would suggest that with a fixed rpm, blades with fewer teeth likely produce the result of a reduction in unintended off axis forces transferred to the workpiece.

 

[Thomas Wayne]

Does every post you make need to contain the assertion that the tools or abilities of others are inferior to your own?

That you infer such is only a reflection of your own insecurities. The simple fact is a LOT of part-time and/or amateur cuemakers do not have spindles that allow them precise control over cutterhead rpm - making your advice about adjusting spindle speed [as part of the the feed- and travel-speed equation] somewhat moot. Had I not acknowledged the existence of precisely controllable router spindles I'm sure you would have jumped on THAT "mistake" instead. Damned if I do, damned if I don't...

Your assumption of 100% cutting efficiency is impossible. The laws of physics apply to even you, Thomas. The math involved in calculating the unintended dynamic forces transferred to the workpiece is beyond my abilities also. But denying that they exist is naive and, or ignorant. Mass is not irrelevant, nor is the surface area at contact as you have suggested.

Well, in that paragraph you shoved a bunch of concepts into my mouth that I didn't actually present. I made no such "assumption", I did NOT deny being bound by the laws of physics, nor do I deny they exist. Maybe it would be more reasonable to discuss what I DID say instead...?

That aside, cutterhead mass IS irrelevant within the scope of a high-speed router exerting a cutting force against a spinning spindle 30 inches long and 1/2-inch in diameter. Oh sure, one can argue that no change in cutterhead mass can possibly be "irrelevant", but those are the sort of nitpickers who would also argue that a fly landing on a heavily-loaded 1-inch steel cable will cause the cable to deflect. It's true, the mass of the fly can do that... but not to an extent that we are actually able to measure it - making it a functionally irrelevant fact.

Once the cutterhead is up to speed and has established the spinning path it's "comfortable" with, a rotating cue shaft is NOT going measurably deflect it more (or less) based on the bit's mass. The table saw shaft-cutting rig mentioned above is all the proof I need of that statement. If your argument is that a router bit with less mass will cut smoother simply because of the mass differential - which I contend is absolute bullshit - then you really shouldn't waste time arguing with me. You need to focus on the hundreds (maybe thousands ?) of table-saw-shaft-cutting cuemakers who are putting out baby-butt-smooth shafts using a cutterhead that has a mass of roughly 50 to 100 times as much as your little router bit. Explain that first, then take pot shots at me...

Weight is only one variable of the equation. By reducing both the mass and velocity when using a smaller diameter cutting tool, you are reducing the overall force transferred to the workpiece. With the assumption of the same surface speed of the cutting bit and the same efficiency of cut in tool design, the unintended off axis force transferred to the workpiece will be reduced. As cutting force is also reduced, there will be a point of diminishing returns when other issues can be introduced into the process.

I read most of that paragraph as "Blah, blah, blah". Assuming a decent router spindle (with negligible run-out), between the two variables of cutterhead mass and size of cutting edge [presented to the work] the edge size is FAR more important - as you theorize the in the final paragraph of your dissertation:

I would only be speculating as to why saw machines result in less push off. But, I am willing to suggest that the rigidity of the machine, the lower rpm, in general, of the cutting tool, and narrow kerf would be the most obvious reasons. I believe that it is also a consensus among makers tapering with a table saw that blades having approximately 60 teeth perform better than blades having 80 teeth or more. This would suggest that with a fixed rpm, blades with fewer teeth likely produce the result of a reduction in unintended off axis forces transferred to the workpiece.

Thank you for finally agreeing with me - albeit probably unintentionally. Obtaining the best surface finish primarily requires finding the best combination of cutterhead profile, carriage speed, and part-rotation speed - all toward the goal of achieving the optimum surface speed for the material being cut. In my experience (30+ years worth), cutterhead mass is so unimportant in this equation that it's essentially irrelevant.

TW

 

[cueman]

Chris - Does using router bits help avoid the push off?

Chris

Yes it almost totally eliminates it.

 

[ChampionsRepair]

Once the cutterhead is up to speed and has established the spinning path it's "comfortable" with, a rotating cue shaft is NOT going measurably deflect it more (or less) based on the bit's mass. The table saw shaft-cutting rig mentioned above is all the proof I need of that statement. If your argument is that a router bit with less mass will cut smoother simply because of the mass differential - which I contend is absolute bullshit - then you really shouldn't waste time arguing with me. You need to focus on the hundreds (maybe thousands ?) of table-saw-shaft-cutting cuemakers who are putting out baby-butt-smooth shafts using a cutterhead that has a mass of roughly 50 to 100 times as much as your little router bit. Explain that first, then take pot shots at me...

The directional component of force has been ignored in this debate so far. You have also ignored the effect of velocity on force in your table saw example. The saw blade in your example with a mass 100 times that of the router bit, would also have a velocity approximately 1/10 that of the router bit. Reducing the influence on force by a factor of 10. My assertion would be that the angle of incidence to the center axis of the work piece would be approximately .5 degrees for a 10" saw blade with a .05" depth of cut, making for a significantly more efficient rotary cutter. With a more efficient transfer of overall force to cutting force reducing unintended force transfer to the work piece. A 2" diameter slot cutter would have an angle of incidence of approximately 6.5 degrees for the same depth of cut. This would result in a less efficient transfer of overall force to cutting force. Further take in to account the directional component of the unintended force and I believe that I have provided a reasonable explanation. May "pot shots" continue?

 

[Thomas Wayne]

The directional component of force has been ignored in this debate so far. You have also ignored the effect of velocity on force in your table saw example.

"Ignored"? Those considerations haven’t even been introduced until just now – how is it that I’ve “ignored” them?

Getting back to the original poster's dilemma, one of the absolute easiest ways to reduce stock pushoff is to simply reduce the size of the tool cutting edge presented to the work. Until you can muster enough bullshit to counter that fact, perhaps adding new "components" to the equation (on an almost daily basis) is maybe just a little too much smoke for the room.

The saw blade in your example with a mass 100 times that of the router bit, would also have a velocity approximately 1/10 that of the router bit. Reducing the influence on force by a factor of 10.

Well, let's just apply some REAL numbers to your junk science here for a moment, shall we? Suppose the router has an rpm of 24,000 rpm, and the tablesaw has an rpm of 3,400 rpm - both reasonable values for those tools. Further assume we're comparing your 3/4" diameter bit to a 10" diameter saw blade.

Surface speed of your router bit = .75" x 3.1416 (pi) x 24k rpm = 4,712.4 feet per minute (surface speed).

Surface speed of tablesaw blade = 10" x 3.1416 (pi) x 3,400 rpm = 8,901.2 feet per minute (surface speed) - almost TWICE the surface speed of your precious little router bit.

(As an aside, my tapering lathe, using a Perske High-frequency router head and custom "slotter" produces a surface speed of just under 11,000 feet per minute)

It's pretty clear from these simple (and indisputable) calculations that your argument regarding the much slower tablesaw rpm [producing less "influence on force"] fails miserably. With ten times the MASS of your router bit and almost TWICE the surface speed, the “influence of force” – a term I’ve NEVER seen applied to tooling calculations – would have to be much greater, wouldn’t it? So why does the saw rig produce smooth cuts again...?

Most interesting, you now fail to mention your earlier hypothesis about the saw blade having a narrower cutting edge... probably because it directly supports my position and is [one of] the correct explanations for the smooth cuts produced by a saw rig. Here, allow me to refresh your memory:

[...]
I would only be speculating as to why saw machines result in less push off. But, I am willing to suggest that the rigidity of the machine, the lower rpm, in general, of the cutting tool, and narrow kerf would be the most obvious reasons. [...]

“Narrow kerf”, huh? Isn’t that pretty much what I said earlier - that a narrower cutting edge can be expected to produce a smoother cut?

My assertion would be that the angle of incidence to the center axis of the work piece would be approximately .5 degrees for a 10" saw blade with a .05" depth of cut, making for a significantly more efficient rotary cutter. With a more efficient transfer of overall force to cutting force reducing unintended force transfer to the work piece. A 2" diameter slot cutter would have an angle of incidence of approximately 6.5 degrees for the same depth of cut. This would result in a less efficient transfer of overall force to cutting force. Further take in to account the directional component of the unintended force and I believe that I have provided a reasonable explanation.

Wow. And you feel this somehow supports your small-diameter, low-cutter-mass argument? Really?

Help me understand your thinking here. Your contention in this last paragraph is that a smaller cutterhead diameter, which results in a greater angle of incidence, will produce “less efficient transfer of overall force to cutting force” – and that this is a bad thing... right? Well then why in the world would an EVEN SMALLER diameter cutter be better?

Now, I have no idea how you’ve calculated the values for angle of incidence that you list above, but my calculations for a 0.050" depth of cut produce the following values:

10” saw blade - ~ 8.1*
2” slot cutter - ~ 18.2*
3/4” router bit - ~ 29.9*

Regardless of whose numbers are more accurate, the inescapable conclusion here must be that if a 2” slot cutter is less efficient than a 10” saw blade (due to diameter), then a 3/4" router bit can only be even LESS efficient than either one.

May "pot shots" continue?

Given your tenacity in arguing a clearly fallacious position, I’m sure they will.

However, getting back to your original contention that MASS of the cutting tool is important in getting a smooth cut – and that LESS mass is “best” – I just wanted to mention that in over 30 years of study and practice in machining wood and metal I have never heard such a claim. In fact, on every table or chart I can find regarding optimum feed and tool speeds, cutter mass is NEVER part of the calculations.

So if you’re right, why the hell are you wasting your time posting on a little billiard forum like this? You need to get your superior knowledge out there for world of manufacturing to see and learn from! The worlds of woodworking, metalworking, and similar related manufacturing are constantly seeking better techniques and processes – get out there and enlighten them, man!

Just don’t be surprised if they consider your contentions as silly as I do.

TW

 

[Paul Dayton]

Increasing or decreasing the mass of the cutter might make a difference if only we weren't talking about a flimsy, flexible workpiece. A shaft is not a 900 lb piece of metal being turned down 3/8 of an inch. It is a thin piece of wood rotating between 30" centers while it is being slapped with the cutting teeth. The mass of the cutter is meaningless as long as it is enough to hold the razor sharp teeth in a truly fixed location around the center of the blade.

Thomas is right. Thin cutters with concentric sharp teeth ground at the proper rake and top angle produce the best cuts. The shaft doesn't know or care what the mass of the cutter blade is only that when the tooth meets the rotating wood there is very little force needed to make the cut.

 

[JoeyInCali]

The only thing the mass might matter is to the router, I THINK.
The lighter the cutter, the less stress it puts on the router and less vibrations overall.

I like my 4-wing thin slot cutter.
Joey~Not debating ~

 

[whammo57]

Are you kidding me.......... turning a shaft involves the following?????

MASS of the cutting tool, values for angle of incidence, low-cutter-mass, surface speed, influence of force, effect of velocity on force, efficiency of cut in tool design, unintended dynamic forces transferred to the workpiece,


Lets just put the shaft between centers, not squeeze it too hard, mount a router on the cross slide, and cut with the lathe spinning slowly and the router spinning rapidly.

WOW !!!

Kim

 

[scdiveteam]

Hi,

I have found that controlling feeds and speed of the lathe RPM and the lead screw rpm with separate dc motors on saw machines is the absolute best combo for the RMS nirvana.

JMO,

Rick

As the dia. of the piece changes the speeds and feeds must be adjusted for a maximum efficiency.

 

[Thomas Wayne]

Hi,

I have found that controlling feeds and speed of the lathe RPM and the lead screw rpm with separate dc motors on saw machines is the absolute best combo for the RMS nirvana.

JMO,

Rick

As the dia. of the piece changes the speeds and feeds must be adjusted for a maximum efficiency.

Which is why, long ago, I switched over to a fully controlled CNC tapering lathe. Not only can I control the feed and spindle rpm, I can program them to vary during any given pass.

Once you've found what works best you can repeat it exactly, at will.

TW

 

[dakota]

Considering a couple different bits...

First of all, thank you for everyone that has taken time to share their knowledge. I just ran into the frustration of a bit dulling which resulted in some barber polling on shafts that were nearly complete. With that in mind I need to get a new slot cutting bit and I am trying to decide between the following cutters:

Freud 58-108 1/8-Inch 4-Wing Slot Cutter for 5/16 Router Arbor

Or

Whiteside 6801 6-WING DRAWER SLOT CUTTER 1-1/4 DIA X 3/16" KERF

If anyone has any experience with either of these slot cutters, please let me know...

Thanks,

dakota

 

[juspooln]

get both you can use the slot cutter for billets if you don't like the result and the six wing for roughing if you like the slot cutter with your setup

6 wing works great for me but it took some time to get everything figured out there is no bit that's going to give you perfect shafts without a little experimentation

 

[olsonsview]

the six wing whiteside

I have been using them for years now on shafts, core dowels, and butts. I have no complaints. Used on my Taper Shaper, they produce shafts that look like I sanded them and no barber pole grooves that I can see or feel. But like all the guys have mentioned, you have to find the right combo of lathe rpm, carriage travel speed, Tail stock pressure, router rpm, and depth of cut in order to get dependable results. Once you find these simple settings that work on YOUR equipment, all is well.
I also like to coat all my bits with Bostik DriCote to make the tool run cleaner and longer. All my cutting bits seem so cut at peak performance for many more shafts with the coating, and build up less pitch, just thought I might mention that, if it is of some interest?

 

[scdiveteam]

I have been using them for years now on shafts, core dowels, and butts. I have no complaints. Used on my Taper Shaper, they produce shafts that look like I sanded them and no barber pole grooves that I can see or feel. But like all the guys have mentioned, you have to find the right combo of lathe rpm, carriage travel speed, Tail stock pressure, router rpm, and depth of cut in order to get dependable results. Once you find these simple settings that work on YOUR equipment, all is well.
I also like to coat all my bits with Bostik DriCote to make the tool run cleaner and longer. All my cutting bits seem so cut at peak performance for many more shafts with the coating, and build up less pitch, just thought I might mention that, if it is of some interest?

Thanks for sharing that OV,

I just ordered a can online and will try it on my saw blades and CNC mills.

Rick G

 

[Naked Cues]

Just as a follow-up:

I used a new 3/4" two-flute carbide cutter, spring loaded live center, and slowed the speed down to the lowest setting the HT lathe would do...and it cut a perfect purpleheart shaft w/ zero chatter.

Thanks again to those who helped out! You guys saved me a lot of headaches...!

-Jason.

 

[JerseyBill]

cutting shafts

Guys , this is great, i've learned lots. Wonderful discussion....

 

[Lexicologist71]

I seem to get better results using a larger diameter cutter than with narrower. I guess the shallower angle of attack reduces impact on the wood.

 

[cueman]

I seem to get better results using a larger diameter cutter than with narrower. I guess the shallower angle of attack reduces impact on the wood.

Yes and the speed of the cutting surface of the bit is increased also with larger diameter. There is a point with bit size on smaller machines that increased vibration will out weigh the benefits.