Cutting problems

[weekend_woodworker]

Hi, we have had a sheppach scroll saw for about a year now and are trying to make some things for Christmas. However when trying to cut this inch thick oak the blade does not seem to be cutting vertically. Are there any suggestions as to what might improve it?

This is the photo of the back and this is the photo of the front:

And these are the blades we are using:

I think they are suitable for hardwoods an inch thick. We are getting the blade nice and tight, but it seems to need a reasonable amount of force to push the wood through the blade. We had been using some Olson blades before, are these better?

Thanks

Mark


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[loftyhermes]

Are you sure the blade is square to the table? If it is then you could be unintentionally putting side pressure onto the blade, take your time and let the blade do the work. Also if you cover the pattern with clear packing tape it will stop the burning in the cut. Try thinner wood if you can, that pattern will be good on wood down to 1/4" thick and will make cutting easier.

 

[AES]

Am I correct in seeing that the blade you're using is a Pegas No. 11 Reverse?

Apart from making sure the blade is tight enough (listen for the "ping" when you pluck it - BEFORE you insert the blade into an entry hole), and checking that the table is square to the blade, you're probably pushing too hard, and/or accidentally pushing off to one side or the other as you negotiate some of those tight corners - that's "just" a matter of practice (sorry)!

Though your wood is quite thick, and heavy, you could also try a finer blade (something like a No. 5 or perhaps 7) and try a blade without the reverse teeth down at the bottom, but skip tooth instead. In all such cases you'll have to reduce your feed (speed into the cut) quite a lot, but that in itself should help keep the blade vertical as you make those tight corners.

Personally I use Pegas, but have tried Olsson before and size for size, find them both much of a muchness - it's just easier for me to get Pegas rather than Olsson (which for me seems to be only by Post from the USA).

HTH

 

[Lons]

If it's hard oak then possibly at the limit of saw and blade, 1" thick oak can be a bit of a beast for a thin blade.
I use Pegas blades and consider them to be excellent, as previously said probably just pushing too hard.
I don't push at all, just let the blade do it's work as fast or slow as it's able and guide the wood rather than push.

Nice design btw, hope it works out well in the end

 

[weekend_woodworker]

Many thanks for the advice. The blade appears to be square to the table. There is some masking table beneath the picture, but we can try putting some sellotape over the top. The blade is a straightforward skip blade. Perhaps we are just expecting to cut too quickly. Would you expect a reverse skip blade to be quicker as that is what we had in before?

Does the blade number refer to the the front to back depth of the blade? So the thicker the wood the stiffer the blade needs to be.

Thanks

Mark


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[AES]

The number of the blade refers to both the thickness (gauge) of the flat wire it's made from, AND the TPI (see attached which is for Pegas, but other manufacturers seem to work to same/similar standards from what I can see).

The main thing to think of is the lower the blade number, the "finer" it will be - so a No. 2 for example, will have a LOT more teeth than your No.11, AND be made from much thinner wire. That of course means a much thinner kerf (width of cut) and that also mean a tendency for the blade to get clogged up (and therefore possibly get bent off course). AND that also means that you must much reduce your feed (the speed at which you push the job forward into the blade). As above, it could well be that you are simply trying to cut too fast, so try not only pushing the job into the blade more slowly but also try slowing the machine speed down a bit, especially when making those tight turns.

And, as ever (sorry!) there's a certain amount of trial and error which, with practice turns into "this is what works well for me".

Going back to the possibility of finer blades getting clogged up with sawdust, as mentioned above, of course a lot will depend on how thick the wood for the particular job is, AND on how much dust the wood produces when you cut it clogging. For that reason I suggested a "skip tooth" blade - i.e. a blade where "every second tooth" is missed out. This allows more space for dust to build up, and for the bigger gullets of the blade to clear the dust more easily/quickly.

A reverse tooth blade has the last few teeth at the bottom of the blade pointing upwards instead downwards like all the rest of the teeth. Personally I find such blades very useful for cutting thinner woods and ply, especially if the ply is not top quality. But for a thick-ish piece of oak, as per your current job I THINK (am NOT sure) that your reverse tooth blades could be making matters worse (by not allowing dust to be cleared quite so easily.

It's all a bit confusing, especially when starting a new project with different thickness & other wood, but as above, it's not so complicated and you'll soon discover what works best for you.

Meantime, there's the chart/s from Pegas:

View attachment Pegas Scroll Blades Wood Rev etc Blades.pdf

View attachment Pegas Multi-Scroll Blades.pdf

View attachment Pegas Multi Scroll Blades.pdf


HTH

 

[KT -andy]

Can't help with your cutting woes , I'm brand new to this fret sawing !
Where are you people getting your blades from ?
127mm pinned .
Cheers andy

 

[AES]

Axminster Tools are the UK dealers for Pegas blades (see the Pegas blade charts to download in the above post).

There are of course other brands than Pegas though most here seem to be happy with them. Most other blades seem to come from the USA, though Hegner UK and Hobbies UK sell other blades too.

 

[weekend_woodworker]

The number of the blade refers to both the thickness (gauge) of the flat wire it's made from, AND the TPI (see attached which is for Pegas, but other manufacturers seem to work to same/similar standards from what I can see).

The main thing to think of is the lower the blade number, the "finer" it will be - so a No. 2 for example, will have a LOT more teeth than your No.11, AND be made from much thinner wire. That of course means a much thinner kerf (width of cut) and that also mean a tendency for the blade to get clogged up (and therefore possibly get bent off course). AND that also means that you must much reduce your feed (the speed at which you push the job forward into the blade). As above, it could well be that you are simply trying to cut too fast, so try not only pushing the job into the blade more slowly but also try slowing the machine speed down a bit, especially when making those tight turns.

And, as ever (sorry!) there's a certain amount of trial and error which, with practice turns into "this is what works well for me".

Going back to the possibility of finer blades getting clogged up with sawdust, as mentioned above, of course a lot will depend on how thick the wood for the particular job is, AND on how much dust the wood produces when you cut it clogging. For that reason I suggested a "skip tooth" blade - i.e. a blade where "every second tooth" is missed out. This allows more space for dust to build up, and for the bigger gullets of the blade to clear the dust more easily/quickly.

A reverse tooth blade has the last few teeth at the bottom of the blade pointing upwards instead downwards like all the rest of the teeth. Personally I find such blades very useful for cutting thinner woods and ply, especially if the ply is not top quality. But for a thick-ish piece of oak, as per your current job I THINK (am NOT sure) that your reverse tooth blades could be making matters worse (by not allowing dust to be cleared quite so easily.

It's all a bit confusing, especially when starting a new project with different thickness & other wood, but as above, it's not so complicated and you'll soon discover what works best for you.

Meantime, there's the chart/s from Pegas:








HTH

Thank you for the helpful advice. You identify the machine speed which is one of the variables I haven’t considered properly. How should one decide what speed to set the machine at?

Many thanks

Mark


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[AES]

For me two things work regarding speed. First, as a general rule of thumb, thin stuff = "fast"; thick stuff = slow". But for me anyway perhaps more important is how you feel when making the cut; i.e. on complex cuts if you feel yourself being rushed then slow down to the point that you feel you can comfortably complete the "loop", tight turn, whatever it is. Then when you come out of that bit on to a more open, sweeping curve, you can speed up until you come to the next tight corner or whatever it is.

HTH

 

[Roland]

Having had to cut oak last year the things I learned were:
1. Use a skip tooth blade to help the dust clear.
2. Use a faster cutting speed than you would for a softer wood.
3. Take your time, and be very careful to not put any pressure on the blade.
4. Change blades more frequently than you would for softer wood. I was changing every two or three feet of cut.

It’s very tempting to put pressure on the blade, even when cutting a straight line, and that’s when the blade curves out of true. Ask me how I managed to cut the aluminium platter of my saw.

 

[AES]

"Thanks for your Thanks" weekend-woodworker. It's appreciated. I hope you found something of help in all the above.

Another thought has crossed my mind, though I definitely do hesitate to mention it, and it's not a recommendation. Have you tried spiral blades? Pegas do them (amongst other makers) and they're listed in the 2nd download above. They vary from No. 2 to No. 8 sizes.

As the name suggests, they're actually likely ordinary flat wire blades, but are twisted into a helix. This means that unlike all the turning and right-angle corner tricks we've learnt to use with ordinary blades, here you can, theoretically at least, just push the job in any direction you like and it will still cut. Sounds ideal?

Well I dunno. I've tried them several times and frankly I don't get on very well with them (but I do still try now and then). At least one member here, who has a helluva lot more experience than I do, and who produces a standard of work that I can only aspire to, describes spiral blades as "the spawn of the devil"!

OTOH, if you look at some of the scrolling videos on Youtube (mainly US of course) you can see several examples of people producing excellent results using ONLY spiral blades. And I THINK there's at least one other member here who uses them regularly too.

Like I said, personally I dunno, but as a packet of a dozen blades is really only pocket money you may want to try them? They COULD maybe help with your present quite thick and complicated project?

Let us know how you get on please

 

[weekend_woodworker]

"Thanks for your Thanks" weekend-woodworker. It's appreciated. I hope you found something of help in all the above.

Another thought has crossed my mind, though I definitely do hesitate to mention it, and it's not a recommendation. Have you tried spiral blades? Pegas do them (amongst other makers) and they're listed in the 2nd download above. They vary from No. 2 to No. 8 sizes.

As the name suggests, they're actually likely ordinary flat wire blades, but are twisted into a helix. This means that unlike all the turning and right-angle corner tricks we've learnt to use with ordinary blades, here you can, theoretically at least, just push the job in any direction you like and it will still cut. Sounds ideal?

Well I dunno. I've tried them several times and frankly I don't get on very well with them (but I do still try now and then). At least one member here, who has a helluva lot more experience than I do, and who produces a standard of work that I can only aspire to, describes spiral blades as "the spawn of the devil"!

OTOH, if you look at some of the scrolling videos on Youtube (mainly US of course) you can see several examples of people producing excellent results using ONLY spiral blades. And I THINK there's at least one other member here who uses them regularly too.

Like I said, personally I dunno, but as a packet of a dozen blades is really only pocket money you may want to try them? They COULD maybe help with your present quite thick and complicated project?

Let us know how you get on please

Many thanks I have got some spiral blades as I thought the children might find them easier when having a go with the saw. In practice we have not played with them much. I am hoping to have another go this afternoon I will start trying the skip tooth blade with no pressure and a bit of a slower machine speed.

Thanks

Mark


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[weekend_woodworker]

Some progress. Seems to be working much better now. We tried the no11 skip tooth which even with a new blade seemed very slow. I tried a spiral blade which was better. In the end we decided that a no 9 skip reverse blade works best. We are running the machine at about half speed and have taken off the foot.

I think the key difference has been not pushing it so hard, so thank you for all the advice.

Mark


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[AES]

Thanks for the update. Glad it's working better now. It's largely all a matter of practice and finding exactly what suits you and your machine.

Project will be finished by Christmas then ;-)

 

[weekend_woodworker]

The finished article!

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[AES]

Well done mate, very good, especially (IF I've remembered correctly!) this is your 1st attempt at such a lot of internal cuts in thick timber. =D>

Thanks for showing the final cut results. Did you try a spiral blade on any of it?

I don't want to tech granny to suck eggs, but some tips I've picked up here (and Youtube) involves final sanding. Some small scraps of sanding paper wrapped around bits of dowel and slightly wedge-shaped offcuts will help a lot for final finishing (before staining/waxing/varnishing?), AND those "emery boards" used for filing finger nails are useful too. Works for me.

Happy Christmas.