Skil 77 wormdrive saw

[mulk]

I have seen some discussion of the Skil wormdrive here and elsewhere.

I have a few comments and a question.

The Skill 77 is the best balanced circular saw I have ever used. It has plenty of power, and great ergonomics. I have maybe 20 of them, one a model E which was the first.

Regarding voltage frequency. All my modern ones are ac/dc. A universal motor doesn't care about cyclicity, so if you drop the voltage through a site transformer, you should expect no power reduction.

Regarding the diamond knock-out for blades. It has been suggested that this is to utilize the torque of the saw. I don't think that is correct. The blade clamp is free-running, and the reccommended tightening is one quarter turn. This is to allow for slippage in the event of potential kick-back. I have never had a problem in 30 years of use of this wonderful saw.

A question. Anticipating a return to Europe, the diamond blade knock-out presents a problem. I don't see any blades on Amazon U.K. with this feature. I did see a replacement blade-clamp for the '77, but of course I've lost it. What is the standard mertric arbor size for 7 1/4" , 8 1/4" , and 12" replacement blades in Europe ?

Can a Skil blade clamp assembly be machined to accept common metric sizes ?

 

[9fingers]

Give me a bit of time to make some measurements on diamond knockout blades I have here and I'll give you a considered reply.
Bob

 

[TrimTheKing]

Hi Mulk

I can't answer any of your questions but I have one of my own...why on earth do you own 20 of these...????

Cheers
Mark

 

[mulk]

Because I'm an old fart, and have been at it for many decades.

You gotta have 3, for rough, framing, and finish. Then there's the rafter cutter. Next a big one at 12" for beams. A couple of spares, and then the historical collection of worm-drives through the last century. Just for fun….

 

[9fingers]

Hi Mulk,

I'm guessing from your reference to collection of older power tools and the term "cyclicity" which we know as frequency, that you might be Andrew who contacted me directly a few days back?

Anyway, I've just measured up a diamond arbour blade here and it is about 25 x 35 mm across the vertices and 21mm across the parallel sides.

By far the most common blade bore in Europe is 30mm with some hand power tool using 25, 20 and 16. The latter is within a whisker of 5/8" so if you have tools with round 5/8" arbours there will be no problem and circular adapter washers between sizes are available.

The problem will be the diamond arbour. This is too big to take a 30mm blade and so would need to be machined down to fit. Most engineering shop should be able to do this for you. I'd be surprised if the material is hardened.

HTH

Bob

 

[mulk]

Yes. It's me. I wonder if there's a demand for Skil blade-clamps milled to accept 30mm circular saw arbors.

As I said, I did briefly see a link for such an adaptor, but lost it.

 

[9fingers]

Yes. It's me. I wonder if there's a demand for Skil blade-clamps milled to accept 30mm circular saw arbors.

As I said, I did briefly see a link for such an adaptor, but lost it.

The only adaptors I've been able to find are the inverse of the ones you want. ie they enable a blade with a diamond hole to be used on a saw with a circular arbour.

To be honest I can't really see how the adaptor you want can work. The blade would have to be offset to one side to avoid the diamond part of the arbour and this would push the blade out of line with the riving knife.

As I said before I think the only solution would to machine the diamond from the arbour.

Bob

 

[mulk]

Hi 9,

Yes, milling the arbor. I just pulled the blade clamp assembly from one of my saws, the flange is about 4cm in diameter.The long axis of the diamond is about 27mm. The distance between opposite sides is around 21mm. I don't quite see how an existing blade flange with the diamond can be milled to fit a 30mm or other blade. One would have to fill in the flats by welding and then mill that down. It might be simpler to get the whole thing milled. I'm no expert at welding and machine shop, so this is surmise.

 

[9fingers]

Just machine away the diamond to leave 16mm round arbour then use 16mm- 5/8" blades that are widely available. You may need a new dished washer under the clamp too but that is trivial to make.

Bob

 

[mulk]

Milling the diamond for a 16mm arbor would leave a scant 1mm shoulder, I don't know if that would be enough. What is your opinion ? What do you mean about the 'dished washer' ?

 

[9fingers]

Milling the diamond for a 16mm arbor would leave a scant 1mm shoulder, I don't know if that would be enough. What is your opinion ? What do you mean about the 'dished washer' ?

Referring to the skil manual online, the diamond on the "saw shaft" needs reducing to 16mm diameter so that none of the diamond protrudes though the inner washer, only the circular part of the "saw shaft" is left to hold the blade.
This has no impact on the size of the flange on the inner washer.

What would normally be called a dished washer, Skil call an outer washer. This needs to be replaced by one with a 16mm circular hole.
This is the manual I've been looking at http://mdm.boschwebservices.com/files/1 ... 8164v5.pdf

Bob

 

[mulk]

In reference to the diagram you are looking at. The 'saw shaft' terminates in a square which locates through to the 'outer washer'. The diamond which engages the saw blade is on the outer face of the 'inner washer', which runs free on the saw shaft. This is how the 'vary-torque clutch' works, by varying the torque between the inner and outer washers via the 'blade stud'. It is not shown on the diagram you are looking at, but the inner face of the outer washer has a raised ridge which locates *within* the hole in the inner washer, and thus should need no alteration. Essentially, the saw shaft is turning the outer washer, and the clutch slips at a point dependant on the friction between the inner and outer washers.

Since power is ultimately transmitted to the blade via the diamond protrusion on the face of the inner washer, it occurs to me that greater torque on the blade stud may be required to prevent slippage of the blade; although I am by no means sure about this. I'll have to think about it. However, I am still concerned that leaving only a 1mm raised ring to support the blade will provide inadequate support. This is why I was thinking about either filling the raised portion of the inner washer and re-milling it to some larger metric bore, one with many common and appropriate blades available, or simply getting complete inner washers milled to the new specification.

Somebody must have thought this out before, but I have not found anything. I wrote to Skil and have not heard back from their technical support yet….