Table Saw Molding Head

THe single cutter at a continuous feed rate would remove the same ammount ......BUT ... the 3 cutter removes it in 3 smaller chips as opposed to one large one giving much better quality finish.

At any given feed rate the single cutter is taking a larger bite.

Although it would be a relativly small hole at those speeds it would go straight throug you assuming you hit no bone. Assuming also you have hit no major organs I hope you keep at least 2 band aids in your safety kit.

Having done a lot of moulding work over the years I would not touch a single cutter cutter head on that type of setup. I would sit down and scrape the mould by hand using no more than a blunt butter knife rather than use it. It is possible that the head may be balanced with a counterweight opposite the knife. The only problem with this theory is how do you compensate for different size/shape/projection/weight knives? I can not imagine how but maybe the head is designed with a depth limiter to limit feed rates. If it is not you are talking a major risk of kickback at that diameter and speed.

Although not a recomended practice but an accepted practice is to use different shaped cutters on the same head at times on spindals (shapers). Occasionally for a one of run you might only grind 1 knife and just use a blank on the opposite side. Whenever I do this I always have a rubber lined

What I was trying to get at was that the single cutter removes more "per cutter" than the 3 cutter design at any given rate.

Which I do not dispute, given the cutter speed vs. feed rates the single cutter does remove more per revolution but certainly not 3 times "dangerous capacity". Regardless of which configuration is being used the cutters are not removing a large quantity of wood. The feed rate would have to be close to the speed of the cutter head, "50 mph" for the 3 to 1 capacity ratio to come into effect. More likely for each revolution and the typical feed rate, each triple cutter probably removes 1 or 2% of its capacity and the single probably removes 3 to 6% of its capacity. I believe feed rate would have to be drastically increased before a significant increase in danger would be noticed between the 3 and single cutter head design. By comparison, a 30 tooth blade is not much more likely to cause a tragic problem than a 90 tooth blade.

Naw. The fragment might cut you cut certainly not go through you. I have been hit by fragments of wood many times thought the years and they mostly bounce off. And while that is only wood, I have also had fragments of carbide go flying also and never see any signs of it hitting anything. Do you think a pro baseball pitcher could throw a small fragment of carbide hard enough to go through your arm or hand? Not likely and he can throw pretty much as fast as the tip speed op a 10" blade on a TS. I have had a fragment of a 22 bullet hit me and it did not penetrate although I did receive a red spot. There simply is not enough mass to overcome the resistance.

Now if a whole tooth or cutter came loose, that would be a different story, still I don't think it would go through you as a 22 bullet seldom goes through at speeds 7 time faster.

After doing that for several days on end, you might reconsider using the single cutter design. LOL If you have never seen one in operation, don't knock it.

Tthe counter ballance is more likely engenereed to be dynamically balanced like car tires are balanced. Counter balance weights are spread over an averaged out area in multiple spots so that minor variations are not so significant. Typical wheel weights on automobiles are placed in as many as

The only problem with this theory is how do you compensate for

Size and shape will not have any effect on balance if the cutter unit is balanced. Balance on a spinning object concerns weight, not shape or size. I strontly suspect that different shaped cutters made ofr a single head cutter will be shorter or longer so that different profiles each has equal mass regardless of shape. You would not want to run the cutter head with out a cutter in it or a 3 cutter head with only 1 or 2 cutters in it.

This would be a totally different situation and while it may be accepted, that is truely throwing the cutter head out of balance by introducing different weights in other locations.

Again, if the single cutter is balanced the load on the bearings is a non issue.

A spindle running collars runs at around 4000rpm, 4500 is

Again, a single cutter head cutter will be balanced so vibration will not be as great as you make it out to be. A cutter does not have to be perfecetly symetrical to be balanced.

And needless to say the risk of throwing a knife

While I'll bite at the possiblilty of a kick back providing your feed rate is "much faster" than recomended , the increase chance of throwing a knife is non existant when copmpared to a 3, 12 , or 90 tooth cutter. Think about single flute router bits that spin at 25,000 rpm. It's all about balance when it comes to spinning irregular shaped objects.

Ok, lets stop and think here for a moment. This single head cutter is not a fluke, flash in the pan tool that was here today and gone tomorrow. I first saw them some 25 years ago. I have heard of no incidents regarding problems with the cutter, have you? True they probably do not leave as smooth of a cut given the same feed rate but as long as the cutter is balanced there should be no vibration. I suspect that if there was significant vibration that the tool would have never made it out of the R&D department. Huge and heavy by comparison engine crank shafts are very irregular in shape and when balanced can spin at speeds in excess of 12,000 rpms.

Leon, I think we are misinterperating each other somewhere.To hopefully make things clearer we will exagerate things a bit. Material is being fed at a constant rate. Keyword being constant, Regardless of that being 5" per hour or 50mph. Lets say that the stock moves into the cutter 3/16" and the cutter has done one revolotion. The 3 knife cutter has removed 3 X 1/16" chips through this 1 revolution. The single knife has removed 1 X 3/16" chip. The same amount of material is removed in either case. It is just the size of the chip(s) that has varied.

Regardless of the feed rate you still have one head cutting one chip per revolution compared to the other cutting 3 small chips per revilution. You can feed a 1000mph if you like the number of cuts per revolution does not change. The one knife head will still cut one and the 3 knife head will still cut 3 per revolution.

I'm sorry, maybe I am spinning in reverse, but i don't follow what you are trying to say here. Per revolution each cutter should remove 100% of its capacity. Three knife will revove 33.3% per cutter and the single tooth

Any increase in feedrate always generates larger cut regardless of number of knives an thus increases risk of kickback. Refer previous comments on chip size

That I agree with, but here you are talking a totally different cenario. Thats like comparing a triangular or square wheel to a round wheel.There is a major difference between 1 tooth going chunk, chunk, chunk compared to to a 30 or 90 tooth saw blade running smoothly through a revolution.(once again chip size) A 30 tooth blade is slightly more likely to cause kick back than a 90 but it is a very very marginal ammount.

I hope that clears things up little. In summary Slower feed rate regardless of number of cutters means smaller chip size which in turn means better finish and less danger. Higher feedrate means larger chip size which means poorer finish and greater danger. More cutters at specific feedrate means smaller chip size which means better quality finish and less danger of kickback.

Maybe not crazy, but not as safe as a perfectly balanced molding head. The more balanced the the cutter head, the less vibration. A well-balanced blade assembly will give you a cleaner cut too.

"Leon" wrote in news:kC7Oh.2092$ snipped-for-privacy@newssvr19.news.prodigy.net:

Craftsman.

SNIP.

LOL... I think we are probably on the same page here Paul. I am only trying to make the point that while a 3 cutter vs. a 1 cutter head probably makes a smoother cut, with a given constant recommended feed rate cutters on both units are most likely well within their capacity of making a safe cut. While your example of the amount removed ratio is correct, I suspect that the amount removed by either stile cutter head at operating rpm is in the low thousands of an inch per cutter pass. If the 3 cutter head is removing

That said, LOL, the single cutter is probably more likely to give a crisp clean cut than a 3 head cutter providing your feed rate is 1/3 that of the 3 cutter version. I have the 3 head version and the cutters do not perfectly fit in alignment with each other. When I use the beading bit the resulting bead is not as perfectly formed as the profile on any single cutter. Because they do not register in perfect alignment on the head they each cut at a slightly different location resulting in a profile that is not exactly like any one cutter.

Yeah -- Old memories. My cousin was cutting moulding with a Craftsman

The surgery and recoup from trying to restore part of the fingertip was almost worse than the injury itself. Horrible looking mess. He was a union utility worker at the time and had to have all of his digets in working order.

He is a talented woodworker to this day but the old RAS, and moulding head is ancient history to him.

RonB

RonB

CORRECT. LOL And the 22 caliber is 7 times faster than a 10" TS blade tip and only 2/3's the muzzle velocity of a 45.

Not even close to the same neighborhood. In fact, the table saw isn't even close to the lead sled speed of a .45ACP.

I too would prefer a router or a shaper for the job, but that's because I generally try to stay away from tools that have been adapted to a secondary use. Having said that, if you think about the speed of your router and the speed of your table saw, and you throw in the fact that routers have been known to throw carbide (especially with cheap bits), you might be more concerned about that router. It's typically somewhere near 3 to 6 times faster than that table saw blade.

Doubt it I have lots of patients and besides if its achoice between somthing taking a long time or having the hands to do it with, the hands wins hands down

Its asicly the same as set of collars with one knife and one blank except larger.

The only practical option i see here that might wirk to allow for differing weights/projections would be a fluid filled head working on the same principle as an. automatic transmition torque converter,You must also remember that increasing projection also upsets balance.

I strongly disagree here. Change the weight or the amount of projection and you affect balance considerably. For a spinning object to balance it must be balanced at that particular configeration. Change that configeration and you upset the balance.

Even at equal mass if one cutter projects further than another it will affect balance.

So is changing the one cutter in a single cutter head

that is true IF a single cutter is balanced.

Unless it has some form of dynamic balancing that will 'adjust' itself on the run it will not balance with varying knives

No it does not. I have some knives which are different but designed to run as a pair. But the design of knives in this situation takes considerable design considerations taking into account weight distribution in relation to projection to compensate for varying shapes and centrifigal force.

Sorry I do not follow your point there. The increased risk of throwing a knife is due to the inbalance, nothing to do with the number of knives

Thats right ... weight is distributed equally in any direction from centre, bit is balanced although oposing sides are different. Now lets take that same router bit and grind or break half the carbide tip of ( simulating changing cutter shape) ...... woops what happened to that perfectly balanced bit.

Not the best brand but it will do the job. Be very careful, use guards, and feed very slowly with hold down and push sticks. Wear eye protection and preferabley a face mask.

I did say I was exagerating a bit. 3/16 was just a nice convenient figure to work with. Maybe i shoul have went to 3/8 LOL

I theory the single knife cutter head at 1/3 the feed rate should give exactly the same quality of finish. I dont know about you but I am not getting any younger and might not have enough time left to take 3 times as long to do the same job

Any multi knife cutter suffers from the same problem. It is the combination of the shape of the 2 or 3 knives whatever the case might be that determins the final outcome. When hand grinding knives like I do it takes quite a considerable number of years practice before you can grind a near perfect set of knives so that they all do their fair share of work and are balanced. Note I said near perfect. Although it is possible to make a perfectly matched pair of knives freehand the time involved far outweighs the benefits. I did do it once for a very special set of knives but you wouldn't want to be paying me for the hours spent stoning / checking/ stoning / checking .... and it goes on. At times this 'feature' is actually useful. Lets say I am grinding a set of knives for a particular moulding to match clients house and I accidently go a little deep in one spot .... woops ... not to worry I just have to make sure that that particular spot on the other knife is correct.

Just as a side point for anyone interested, grinding a set of knives to match a particular moulding is not as simple as 'tracing' the shape onto the cutter and grinding away. The shape has to be projected to take into account the rake angle of the particular head you are using and the projection of the knives. Set up those knives in the same head a second time but project them out a little more or pull them back a bit and you will get a slightly different shape on the moulding. Put those knives into another head with a different rake angle and once again you get a slightly different shape moulding. The difference is not that noticable to look at but don'y try to mitre or butt join the two pieces together ... it will make you look like a poor woodworker.