I’m considering a Jet Bench top saw and a Hitachi Job Site Saw. The Jet is belt driven and the Hitachi is direct drive. which would be better for accuracy and durability? Any help appreciated. Max
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Replies
Belt driven is generally better in all respects. Direct drive saws are usually bench top models where weight is more importaint.
Pardon my spelling,
Mike
Make sure that your next project is beyond your skill and requires tools you don't have. You won't regret it.
I think direct drive saws need more clarification for the average woodworker. Direct drive stationary saws like Northfields, old Oliver, Tannewitz were 3650 rpm motors. Benchtop saw use universal motors like you would find on a router (20,000 rpm) and are either geared down or like many, use a cog belt to lower the rpm. So there is no such thing as a true direct drive benchtop saw and the so called direct drive is most likely an actual belt drive. This is true on miter saws. Typically they are noisier than a router.
Edited 2/5/2007 9:19 am ET by RickL
Very true, but I dont think that is the type of saw he is looking at.Pardon my spelling,
Mike
Make sure that your next project is beyond your skill and requires tools you don't have. You won't regret it.
I don't think you understod my post. Direct drive on these saws isn't simply direct drive. There's either a gear or a belt to reduce the motors rpm from a universal motor so in most cases the so called direct drive is really a belt drive. I know the difference in a belt drive contatctor saw. That type has a V belt and the motor hangs off the back. My point is most folks are mistaken as to what a direct drive saw really is.
So are you saying that bench top saws are geared down (or up) and not directly driven?Pardon my spelling,
Mike
Make sure that your next project is beyond your skill and requires tools you don't have. You won't regret it.
On portable bench table saws they are not a true direct drive like you would find on a large commercial table saw or radial arm saw. They use universal motors the same you would find on a router and in most cases a cog belt reduces the 20,000 rpm to 3,450 or there abouts which gives it increased torque. Same on a miter box. I spent 10 years working as a tech for a dealer and had to replace many a belt on these type of table and miter saws. All you need to do is look at a schematic. The other simple clue is if the motor takes brushes it's a universal motor. Typically they use a cog belt for this but I've seen it done with a gear as well. Your handheld circular saw uses a gear to reduce the speed of the universal motor. The standard belt drive like you would find on a Delta Contractor would be a longer lasting way to go as the motor is seperate. The so called "direct drive" motors are lighter and makes the saw more manageable so it's a compromise on your needs and usage.
Edited 2/8/2007 8:14 am ET by RickL
i guess i'm confused, what i consider to be direct drive is when a motor has a threaded arbor that the blade is attached directly to.
is that not the case?
Yes. A direct drive tablesaw ( or any other divice ) will have the motor shaft turning the blade. Or in the case of a turntable for playing vinyl records, turning the platter. No belts involved. At least outside the motor
Paul
Edited 2/8/2007 1:17 pm ET by colebearanimals
That is interesting. I didn't know that. I even own a Ryobi BT3000 (or something like that) but I never use it.....Pardon my spelling,
Mike
Make sure that your next project is beyond your skill and requires tools you don't have. You won't regret it.
"The other simple clue is, if the motor takes brushes, it's a universal motor"
This is getting out of my field, but doesn't a repulsion induction motor have brushes - not that they would ever use one in this application?
Thanks for your input everyone. With limited space I think the Jet Bench Saw (5000rpm) might be my best bet. Gracias Amigos
Point taken but the only repulsion induction motor I recal seeing in WW is the ancient ones found in old Unisaw. I just think people toss the term direct drive around without really knowing what it means and don't really understand the difference between motor drives. Even the proverbial myth of a 220 volt motor running cooler and giving more power than the same motor on 110. Just went through that rigamarole with someone and it took the motor repair shop and several good electricians to set the record straight of that being a total myth.
I have an old one third HP repulsion induction motor from the farm - used to pump water. Really old - dates back to the thirties. I remember back then that the motor repairman said "they just don't make RI motors of that size anymore. It hasn't been used in many years. I should try to see if it works some time. Wished I knew more about motors. Have always been interested in electrical things. Wish I had some of your knowledge. Do they make RI motors of any size now a days?
Off the top of my head I can't think of any. In my business of woodworking, metal working, machine repair the only one I run across is the old Unisaws and pretty infrequently.
Hi RickL,
So, small bench top tablesaws aren't really " direct drive ". I seem to have been misinformed. I have an old makita 8" bench top tablesaw that i used to use on job sites. Dug it out yesterday and turned it over. Looks like they mounted a skillsaw upside down. Would there be a belt or gear here? Not that it really matters, just curious. Thanks for shairing your expertise.
Paul
I think they are still used in floor machines. Buffers, scrubbers.
Repulsion start motors were, at one time, commonly used on shop size air compressors. They have high starting torque (from 300 to 500 per cent of normal running torque). I suspect that the main reason they are hardly used anymore is due to the cost of manufacturing this much more complicated type of motor. I have one on an old WABCO air compressor, built in 1949. It still runs fine.
FYI The Jet bench top is rated at 5000 RPM, All other cabinet/contractor Jet saws are either 4200 or 4000 RPM.Work Safe, Count to 10 when your done for the day !!
Bruce S.
Belt drive tends to be smoother with lower vibration.
Accuracy is different from durability.
Belt driven motors average longer (and quieter) life than direct driven ones, given the demands of tablesaw use.
Accuracy comes more from a good fence than any other factor.
Expert since 10 am.
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