Thread: Mafell, why no worm drive models?

Hi Pumice!

Thank you very much for reading my posts! I'm very honoured, i read and understood your question and i'm preparing the answer. I'll make something special out of it, but it takes a tick. I hope to have it ready and posted on Friday.

for now, all the best from Holland!

gerhard

Hi Pumica,

back again on Friday Dec. 9th, as promised. The text was getting so long that i feared i might lose it when the forum connection should be broken for some reason. So i made a Word document out of it, for you to download and read at leasure. It's not finished yet, though.

greetings

gerhard

Wow! What a reply, brilliant history lesson.

Many thanks.

Mick.

Originally Posted by gerhard

Hi Pumica,

back again on Friday Dec. 9th, as promised. The text was getting so long that i feared i might lose it when the forum connection should be broken for some reason. So i made a Word document out of it, for you to download and read at leasure. It's not finished yet, though.

greetings

gerhard

Thank you for the time and effort you put into the reply.

Worm drive saws are really a West Coast preference. What I hear is that on the East Coast, they use sidewinders. I wonder if the preference for worm drivers in the Pacific NorthWest is due to how much it rains there, making the wood quite moist, necessitating high torque saw .

Bosch makes a worm drive that is identical to the Skil so it must be rebadged. Bsoch used to sell the worm drive as a rear handle or top handle but now I only see the rear handle on the website.

My friends in the roofing and construction field use the saw while the they are perched up on beams,rafters etc.. They say the rear handle means they can just let gravity pull the saw down and use one hand operation.

You're welcome, Mick!
and hi Pumice,

that the Skil and Bosch worm drive saws look like very very close relatives, is no coincidence, since Bosch owns Skil since 2003:

Excerpt from Wikipedia-article, nicely summing up the activities of Bosch in the US:

2003 - The formation of the Robert Bosch Tool Corporation and acquisition of S-B Power Tool Corporation and Vermont American Corporation including the brand names for Bosch Power Tools, Skil Power Tools, Dremel, Vermont-American, Primark brands, and Gilmours.

Bosch built a factory in Greenville, North Carolina, to cater for the US market with specially adapted products. The belt sander GBS100A(E) is made there, and since this is a conventional model that suits safety and normalisation standards almost worldwide, Bosch can sell it worldwide and does so. But their worm saw is not available on the Euro-market (neither is the Skil 77). The same goes for their 1617/1618 model routers, which are of a typical American style.

It is quite regular for big global brands to set up a plant somewhere, that specialises in local demand. Makita also has a US-setup, in Buford Georgia. Here they make SCMS's -amongst other things- with a typically American flavour. Black & Decker did the same in Europe; their Italian works made adaptations of American professional designs and also carried out their own specific designs, both complying to European standards and particular demands. This made for some products that were quite unlike their US repertoire.

The fondness of worm drive saws is so strange and interesting, that there is almost a mystical quality about it. Like i said in the reply (which isn't finished yet), i can't imagine form a purely physical standpoint, where the higher torque level in a worm drive comes from when it has the same ratio as the spur drive that it is compared to. The gear ratio and the rpm of motor and blade of a 77 are virtually the same as those of the average spur gear saw of the same blade gauge and motor wattage. Does the worm drive really perform better at low rpm (by which i mean severe load situations, that all the practice guys praise this saw for)? That's contradictory, again from a physics standpoint, since friction increases considerably at very high torque asituations. This friction is converted to heat instead or power and must be subtracted from the motor's wattage.

This is a very interesting topic and i just can't put my finger on it; which makes this marvellous stuff to delve into. I also have yet to find a perfectly satisfory scientific explanation for it, in all the forum entries and comments i've read so far, real facts and measurement results that could be considered as definitive proof.

So i wondered what else could cause superior torque, should it turn out that it's not (or at least not exclusively) due to the worm drive. Right now i put my money on the motor and on the successfull combination of all ingredients. I think this is one of the rare products that has been tried and tested and reexamined and improved and honed over many decades, to such extent that motor, drive, specs, handling and the machine's behavior have become the perfect blend or marriage. So many people are fond off this thing, so many hours of experience and user input have gone into its development, that the factory has obviously provided the perfect answer for all that the customers have asked for.

I wonder what would happen if a 77's motor would be fitted with a spur pinion and strapped to a sidewinder saw. That would be interesting. I noticed many times that American electric motor designs seem to have a larger diameter (and somewhat shorter in length) rotor and stator than their European equivalents have. Especially in circumstance of high torque and severe rpm loss, larger diameter rotors have a definite advantage. Short rotors also experience less airflow cooling difficulties than long sleek rotors do. So the reserves of these short stocky motors must be larger than the reserves of the thinner longer motors that are usually found in European saws. Since the Japanese are very fond of American technology and tend to copy it, Makita's and Hitachi's heavy duty power tools also show the preference for these shorter American electric motor designs. Which may be one of the explanations for American users reporting of having enjoyed reliable and durable use from Japanese power tools. Japan has also followed the Edison's standard of 100 Volts and since the thicker wire gauge (due to the higher Amp flow through the motor) is harder to wind mechanically, shorter rotors and stator are easier and quicker to wind. That's another reason for resemblance between American and Japanese brush motors. A lower voltage is a coil has the additional advantage that there is a lower voltage difference between neighbouring windings, and in case of severe heat and resulting compromittation of the wire's insulation material, the chance of voltage flashover and thus the beginning of a short-circuiting in the coil, is slimmer. So, American brush motors may weel have more stamina in adverse circumstances and in that department, the Skil 77's motor has all the right specs and sizes going for it.

I wonder how others think about this, notably motor coil repair specialists and other pros in the field. Up to now i found no torque curve graphics of a Skil motor, to match against the curve of a sidewinder motor. That would put a new angle in the discussion of the worm drive saw's discussion, i guess.

Pumice, since you're from the States, i wonder if you'd know a reliable source to obtain a brand new HD 77 from. I've gathered that the original HD has been out of production for some years now and that dwindling stocks (while they last) are the only remaining source. From all the comments and opinions that i've read on the newer SHD, i concluded that this is not the version to go for.
My tool collection cannot be complete without this renowned type of tool. I remember having seen a star-spangled-bannered commemorative version to honour and help sponsor the brave firemen on the occasion of 9/11. There was an occasion on the web, of purchasing and importing one and i missed out, for which i can still bang my head against the wall up to this day.

greetings

gerhard

i added some pics to illustrate my comparison between the Skil 77's motor and their average counterparts (as used in 7 1/4"sidewinders) of European design. While studying the picture of the Skil's field, i saw that its poles are divided into larger main parts, with narrower auxiliary parts on either side. In wonder why that is, since i never came across such a layout in European circular saws . For me this is interesting stoff and worth looking into. I'll be back when i found out the reason.

bye for now

gerhard

I have the skill worm drive..weighs a ton...but i really like using it. When i bought the saw it was expensive and there was no real justifiable reason to buy it other than i liked it...
Mine i would say is maybe 15yrs old..maybe a little more and done very little work.
Gerhard...spur drive or Hypoid???I wouldn't think it is possible to have a spur drive..i would have thought it is either a bevel or hypoid.....But i'm no expert.