Scroll saw--difficulty cutting

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craniac
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Scroll saw--difficulty cutting

Post by craniac » Sun Jan 25, 2009 11:55 am

Hi,
I am kind of clueless. I put a 15 tpi blade (teeth pointed downwards) on a borrowed scroll saw, adjusted the tensioner and tried to cut out my son's derby car profile. I had to push pretty firmly and the cutting went very slowly--a few millimeters at a time. Is that normal? Am I doing something obviously wrong?

note: the saw is an old sears craftsman, and I experimented with higher and lower speeds.

Thanks! We race on Tuesday and I wish I had discovered this forum earlier.



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gpraceman
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Re: Scroll saw--difficulty cutting

Post by gpraceman » Sun Jan 25, 2009 3:04 pm

I also use 15 tpi blades with the speed maxed out. You do have to press harder than you might think you should. I tried 10 tpi blades, which are supposed to cut thicker wood, but they would surge through the cut.


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Awana Grand Prix and Pinewood Derby racing - Where a child, an adult and a small block of wood combine for a lot of fun and memories.

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Re: Scroll saw--difficulty cutting

Post by Mr. Slick » Tue Jan 27, 2009 8:59 am

If you go to lower teeth per inch, you have to make sure that the tension on the blade is fairly high or you risk having a bowed or cupped cut instead of one that is straight up and down. I normally use 10tpi on my saws but I have the tension set fairly high on them. Since I am not the one doing the cutting it doesn't seem to take too long. :wink:

I have noticed that depending on the block of wood, some people finish their profile cuts much quicker then others. Even drilling the holes for the weights I notice lots of variation in the wood that effects the speed/progress of the drill press.


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roosclan
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Re: Scroll saw--difficulty cutting

Post by roosclan » Sun Jan 24, 2010 6:50 pm

I use a 7tpi blade and set the tension very high (about 1/8" of flex in the blade -- at most). I run at high speed and am able to cut through the blocks rather easily.


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Re: Scroll saw--difficulty cutting

Post by FatSebastian » Sun Jan 24, 2010 7:33 pm

:welcome: craniac! Your experience of slow cutting with the Craftsman saw sounds similar to ours, and we've tried lots of different blades. While I believe scroll saws are intended to cut wood much thinner than PWD block, it will cut eventually - although it goes a lot faster if you're not cutting through a full-thickness block. We now usually cut our block down into a thin plank or wedge with a band saw before trying the scroll saw cuts.



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Re: Scroll saw--difficulty cutting

Post by Nitro Dan » Sun Jan 24, 2010 9:30 pm

At our first workshop we tried using scroll saws to cut the blocks. The lines quickly backed up and people started complaining. We brought in band saws at the next sessions and the lines went immediately to zero waiting time. Like FatSebastian, we only use the scroll saws now-a-days for shaping a thin plank that was cut off the block with a band saw.

The band saws are much more dangerous than the scroll saws, but their speed makes them a necessity. Because of their power, we don't let the cubs use them; in fact, only the owners of the band saws are allowed to use them. We make sure that the owners carry their safety keys on them, so they are the only ones who can turn them on.

-Nitro Dan


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Re: Scroll saw--difficulty cutting

Post by Mr. Slick » Sun Jan 24, 2010 9:40 pm

I use 3 scroll saws at the workshops. We also have 7 other stations to do their wheels, axle heads and axle shafts at. With the weight addition station and the two tables that can easily fit 2 families at each for design work, we have a total of (3+ 7*3 + 1 + 2*2) = 29 stations. This has eliminated the wait at the saws. We limit the workshop to 30 cars per night and are usually all done in a couple of hours. They even get their cars up to 4.75 oz before they leave.

The loss of safety by using the band saws by kids is not acceptable in my opinion. It virtually eliminates the kids from being able to participate in cutting out THEIR cars.

Please put SAFETY FIRST! Pinewood derby workshops are NOT a place to practice first aid.

Besides, if people complain about waiting, just remind them that the urgent care wait for stitches is much longer. ;)


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whodathunkit
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Re: Scroll saw--difficulty cutting

Post by whodathunkit » Fri Aug 02, 2013 8:51 pm

Older Topic I know..

It is difficult to make very specific recommendations in blade selection
because of the following reasons..

The industery is not completely standardized.
A number of variations among manufacturers do exist
When scroll saw blades made by foreign manufacturers are included.

The preformance of blades can very from "batch to batch"

For example,
You may be able to put one blade to a lot of tension and get extensive use from it;
however,though the next blade is identical to the first one,
the second one will dull or snap in less then half the time,
even though all of the outher conditions appear the same.

The human element plays part in determining which blade to use,
because individual judgments are different.

What is considered a moderate feed rate to one person can be interpreted as something entire different by another individual.

There is no blade that is the absolute best for a given job.
Each blade will handle a range of jobs with various materials and different thickness.

However keep in mind the general guidelines for blade selection:
The finer the blade,the less the thickness that can be cut without problems.
With thick stock and thin blade, the feed rate must be slower;
the results will be a smoother cut and less frequent blade breakage.
roosclan wrote:I use a 7tpi blade and set the tension very high (about 1/8" of flex in the blade -- at most). I run at high speed and am able to cut through the blocks rather easily.
Maybe because the 7tpi blade is used most for heavy duty,fast cutting..
for all woods up to the saws capacity.

Remember,-the thinnest blades are for the thinner materials..
However also remember that medium-size fret blades such as those in the 5 to 9 range are still
very narrow when compared to blades widely used for conventional cutting jobs with a rigid-arm scroll saw.

One more general guideline should be noted:
As the thickness of material increases, use blades with proportional fewer teeth..
In short use a coarse blade for thick material.

The importance of haveing at least two,preferably three,teeth in contact with the work piece.
Because of unique cutting capabilities of the constant-tension saw blades that are finer then usual
can sometimes be used to cut thicker materials.
However don't feed the material too quickly more tension is required:
Slower feed rate at curves to avoid bellied or unsquare cuts.

The amount of detail of your particuar project is very specifically related to blade selection..
Always use the widest blade possible,but one that will still allow you to make the desired curves
with ease.

For sawing soft woods 3/4" or thicker, some have recommend a blade with 7-10 teeth per inch.
for hard woods, use a blade with 10-20 teeth per inch,depending on the type of turns required.
For hard wood 3/4'' thick or thicker,use a blade with 10-15 teeth per inch.
In general,the thinner the material to be cut, the more teeth per inch there should be in the blade to be used.
The coarser the teeth in the blade, the faster the cutting will be.
However, where sanding is to be kept to a minimum, it is often more practical to use a
finer-tooth blade to minimize the surface tearing of the edges cut.


What type of automobile can be spelled the same forwards & backwards?

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whodathunkit
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Re: Scroll saw--difficulty cutting

Post by whodathunkit » Fri Aug 09, 2013 8:39 pm

Mr. Slick wrote:

The loss of safety by using the band saws by kids is not acceptable in my opinion. It virtually eliminates the kids from being able to participate in cutting out THEIR cars.

Please put SAFETY FIRST! Pinewood derby workshops are NOT a place to practice first aid.

Besides, if people complain about waiting, just remind them that the urgent care wait for stitches is much longer. ;)
Mr. Slick
It would be nice if we could get a saw blade stoping system for the band saws or scroll saws..
Like this table saw has.. "That will not cut fingers".
http://www.sawstop.com/?gclid=CInpzJ3o8 ... 7AodVUwAFg" target="_blank


What type of automobile can be spelled the same forwards & backwards?

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