Table Saw Moulding Head

[Anonymous]

You must enter a message when posting

 

[Scrit]

Surely, then, it's an issue of scale. The table saw moulding head seems only capable of accommodating cutters of a similar size or scale to those available for routers, but because it runs at a lower speed the surface finish is likely to be poorer (less cuts per inch). The size limitations of cutters means a larger moulding would have to be built-up in sections - which is much the way our forebrears created many complex mouldings with hand planes. Modern portable routers can and do accommodate much larger cutters than you could run on the saw, including some amazing (and at times worrying large) panel raisers, but as you rightly say these require multiple passes for safe usage against the single pass normally taked on the spindle moulder and some of them cost a mint.

I agree with you over the issue of "specials" and large mouldings such as some architrave and cornice mouldings. For those the only suitable machines are the through feed moulder and the spindle moulder, but even there if you run compliant tooling (and since 2000 that's all we've been able to buy and if you are in the trades is what you are obliged to use) you either have to buy a tool grinder (£3k to £10k new) or have a grinding service make you up some knives at a cost of £30 to £40 a pair (and that's ignoring the requirement to have limiters which almost doubles the price). So frankly doing it the way you are supposed to isn't that cheap either.

Scrit

 

[Anonymous]

You must enter a message when posting

 

[Scrit]

It's not illegal for me as a sole trader to use non-compliant tooling ASFAIK and in any case I couldn't afford to do otherwise.

Then why is it illegal to sell non-compliant tooling, especially as a machinery/tooling dealer even to an amateur or sole trader? In the event of an accident you may find that your insurers don't actually agree with you on this point and decide on a "partial liability" claim. But then perhaps I'm viewing this from the perspective of a former employer where a risk assessment was a legal and insurance requirement (and still is with my current insurer). Personally I don't see why anybody in the trade should be allowed out of this one as the risk is the same self-employed or "cards in".......

Machine copied cutters are never quite as accurate as hand made ones suprising though this may seem. The explanation for this being that hand making involves repeated "offering up" to the profile sample to be copied, until no error is perceptible.

The "machine made" cutters you are talking about are generally produced from a hand made template used on a manual profile grinder - if the template is right, then the tooling will be, too, as I'm sure many (ex-)engineers on here would agree. If owned in-house the profile grinder can be used to "tweak" a cutter set in the same way as doing it by hand, but is likely to be more consistent if the template is corrected.

Machine made copies could be fettled up in the same way, but safety blocks with pegs, limiters etc inhibit fine adjustment.

But that is why if the base template is right to start with then this "adjustment" shouldn't be necessary. If you're having to do that then surely there's something wrong with the template you're working from.

I'm almost thinking that you're going to start decrying the demise of the French cutter and the square block, both of which I have used and neither of which are legal any more - mainly because they were so ruddy dangerous (and I, personally, still have a soft spot for the French cutter - much easier to grind than the Whitehill)

Scrit

 

[Barry Burgess]

Scrit I am glad to see this gets you worked up - I value your comments and will steer clear but Philly's dado demo today got me going. I will have to buy one of those up market Yorkshire macs and search the top shelf but I am not 6' so maybe I will need the hat.
Barry

 

[Inspector]

Scrit you said.

"Surely, then, it's an issue of scale. The table saw moulding head seems only capable of accommodating cutters of a similar size or scale to those available for routers, but because it runs at a lower speed the surface finish is likely to be poorer (less cuts per inch)."

I will have to disagree because although the router bit is turning faster and in fact may even have a faster tip surface speed than the table saw moulding head. The resulting surface from the moulding head will probably be better, especially in the wilder grained woods, because the 'cut arc' is larger (effective lower cutting angle) which produces a cleaner cut.

The principle can be observed by using a 1/2" diameter bearing guided pattern bit and a 1" or larger diameter one, and comparing the results of the two. On a shaper given the choice between a 4" cutter or an 8" diameter one, which would you pick to produce the best finish?

I won't argue any of the other pro / con items of the moulding head but probably the reason they have fallen out of favour, even in North America, is with the huge selection of now cheap carbide router bits along with routers of far greater capacity, also cheaper. You need to remember that in the heyday of the moulding head, there were few large routers and only carbon and high speed steel bits available. I'm certain that you can still remember how easy it was to dull a high speed steel router bit. That left it for the table saw /radial arm saw to do the heavier moulding and shaping operations for the hobbyest and small shop that couldn't afford a shaper.

It might also be remembered that it was easier to modify or grind new profiles for a moulding head than for router bits , because the balance and profile symmetry issues of a router bit are magnified.

I haven't got a moulding head for my saw, by the way, since I have all I need with the hand tools, 4 routers and a planer/moulder too. If I did see a need, then I would buy a good one.

Darn. I did say that I wouldn't mention the pros / cons, but I have to say that the one area that they do shine is, for cove cutting on the table saw. With round tipped blades they are reported to produce a cove that requires almost no cleanup, compared to the one made with a regular blade. OK. Now I'm done.=D> =D> =D>

 

[Anonymous]

You must enter a message when posting

 

[Scrit]

The resulting surface from the moulding head will probably be better, especially in the wilder grained woods, because the 'cut arc' is larger (effective lower cutting angle) which produces a cleaner cut.

The principle can be observed by using a 1/2" diameter bearing guided pattern bit and a 1" or larger diameter one, and comparing the results of the two.

I think you'll find that router cutter designers take this into account - compare a 2in diameter 2-flute with a 1/2in 2-flute and you should be able to discern some difference in angle, but even of that weren't the case the router cutter does take a much smaller "bite" out of the work by dint of it's higher rotational speed. 2-flute @ 18,000 rpm = 36,000 cuts/min (router cutter) against 3-flute @3,000 rpm = 9,000 cuts/min (shaper head on saw). That translates to a much higher number of cuts per inch (25mm) assuming a feed speed of 1 metre/min (40 in/min): 900 for the router, just 225 for the saw spindle. Which is going to appear or feel smoother? Failing to take feed rate into the equation means that you miss what I feel is a significant factor.

Another thing to be taken into account is the consistency of feed rate - on a CNC router the feed rate is controlled as is the toolpath, the result is that most cutters used in that environment are rarely more than 50mm in diameter (unless complex in design) but the surface finish is generally superb. This consistency of feed on a spindle moulder can be obtained by employing a power feeder and if you go from manual feed to power feed the improvement on surface finish can be very noticeable indeed. Another factor in improving surface finish is the employment of limiter tooling on spindle moulders (most router tooling in Europe is if this design in any case). When I was first told of this, by a technical rep. from a tooling company, I was to say the least sceptical, but limiter tooling ensures that when manually feeding it is impossible to overfeed, which in turn promotes a rough cut and I have to say that in hindsight the he was probably correct. The downside, however, is that limiter tooling won't allow a fast and rough (hogging) cut by dint of it's design so alternative techniques such as roughing-out on the table saw sometimes need to be employed

One of the biggest problem with guide bearing bits is the diameter of the bearing on the cutter and the quality of the template. Using a non-guided bit in conjunction with fences will considerably improve the quality of cut.

On a shaper given the choice between a 4" cutter or an 8" diameter one, which would you pick to produce the best finish?

In reality this isn't a choice that you can make. Spindle moulder profile blocks are generally between 75mm (3in) and 125mm (5in) in diameter. I normally choose the largest head you can and run it at a lower rotation speed simply because of the extra smoothness you get from the bigger heads due to their inertia, just like the wheels on a bandsaw (the flywheel effect). A solid steel 125mm diameter block running a 50mm high cutter weighs quite a bit more than a 75mm one and consequently requires a bigger motor to drive it, bigger bearings and a bigger brake to stop it. Incidentally the smaller 75mm ally blocks have come in mainly to accommodate the weaker braking on lightweight spindle moulders.

You need to remember that in the heyday of the moulding head, there were few large routers and only carbon and high speed steel bits available. I'm certain that you can still remember how easy it was to dull a high speed steel router bit. That left it for the table saw /radial arm saw to do the heavier moulding and shaping operations for the hobbyist and small shop that couldn't afford a shaper.

Oh, yes, I know how easy it is to burn HSS and tool steel. But the heyday was surely pre-1980. Since the 1970s big routers have become steadily better whilst carbide tooling has become cheaper. It has to be remembered that the Germans more or less invented carbide tipped (Widia = wie Diamant) tooling to cope with their WWII wondermaterial, Spannplat or chipboard, and although TC was initially a military product (designed to tip anti-tank projectiles fired from aircraft such as the Ju-87G Stuka), TCT tooling appeared in woodworking in the UK as early as 1950 (source: Wadkin catalogue) - and we were relatively late adopters here due to the need to import tips. TCT tooling has therefore been around for a long time and has become steadily cheaper, certainly since the late 1970s probably because of the improvement of grinding techniqes more than anything else. Here in Europe I remember deWalt selling the 3-wing moulding heads for their radial arm saws, indeed I had one, but the inherrent lower rigidity of the radial arm saw and consequent vibrations made it a very poor substitute for either the spindle moulder or the router and now I'd think twice about a design which periodically could eject cutters (the securing bolts could occassionally loosen or shear which is possibly why DW sold a substantial steel guard to go with them). I'm sure the modern cutters have a wedge-lock design which means that this is not possible, but they are still as awkward to guard as a dado head (Oh darn it! I went and used the G-word )

Scrit

 

[Inspector]

Scrit you are a worthy foe and advisory. ccasion5:

I did not mention feed rates as I was assuming that it was a given that they were to be optimum for a given cutter.

](*,) I will remain stubborn in my belief that given all other factors being equal, a larger diameter cutter will produce a better finish. ](*,)

If both our posts are blended, filtered, and distilled. The conclusion might be that the moulding head has not advanced with the times. It has not had the benefit of design and material improvements that have benefited the router bit.

Anyone that has or wants to put a moulding head to work needs to be aware and understand it's limitations and dangers in order to put one safely to use. Given that the vast majority of people do not have the background and knowledge to use one, they are far better off working with the safer and more versatile router.

 

[Barry Burgess]

Inspector
Scrits comments are 99.9 % of the time the best practice and are for me the way to go - if I choice not to follow his advice I am at risk and I better be aware - it could cost me bits of my fingers
Thanks again Scrit the source of knowledge.
Barry