Details for a scroll saw

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Details for a scroll saw

This topic has 15 replies, 11 voices, and was last updated 29 January 2016 at 10:54 by Robbo.

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26 January 2016 at 17:29 #32638
Sam Longley 1
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@samlongley1
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26 January 2016 at 17:29 #222702
Sam Longley 1
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@samlongley1
I want to make a scroll saw for thin metals, grp sheet, ply & balsa ( model aero building).

I would appreciate comments on the following:-

1) How many oscillations per minute do forumites reckon I need. I will have a simple eccentric & the number of revolutions will govern the number of times the blade goes up & down.

2) How far up & down would you reckon the blade should travel. This will govern the size of eccentric. is 20mm enough or too much? Should it be faster & less stroke length or slower & a longer cut. Presumably the upper spring will have to adjust to this & thus govern the stroke. But it must affect operation somehow

3) I seem to recall a standard single phase motor of about 0.25 HP runs at 1450 RPM. Is that correct? & any ideas where I can source one cheap?

4) I will cut the gears from tufnol as I have only just bought the lathe & mill ( Promised delivery Friday– Hurrah!!!) so I want to go easy on the cutters.

So how big should the teeth be. I know the ratio is set by number of teeth to number of teeth but should I be looking at very small teeth. How does one decide on tooth size on gears . Is there a table somewhere that one follows. Would smaller teeth be better on tufnol ? Bigger may be easier/ quicker but will the tooth snap off? should I have small teeth for quieter running or will they just strip off?. Or is it decided by the divisions available on the dividing head?

Finally – No; I do not want to buy one. Half the fun is making it ones self

Thanks
26 January 2016 at 18:38 #222719
JasonB
Moderator
@jasonb
1000-1500 strokes would be about right so could come straight offa 1450rpm motor and save having to make gears.

15-20mm stroke is usual.

Use sheet tufnol not rod
26 January 2016 at 19:10 #222722
Michael Gilligan
Participant
@michaelgilligan61133
Posted by JasonB on 26/01/2016 18:38:25:

Use sheet tufnol not rod

.

… and, it should be one of the fabric grades, not paper.

MichaelG.

.

Edit: There is a very useful document linked in my post on this previous thread..

… Ooops: the link to Tufnol's document is dead

… But this should suffice.

Edited By Michael Gilligan on 26/01/2016 19:21:44
26 January 2016 at 20:31 #222729
frank brown
Participant
@frankbrown22225
Glass fibre is brutal on teeth, choose cheap bladed for this, Thin metal will require really fine teeth 60 TPI?, wood can be a lot more coarse 20 TPI. I saw a man cutting out wooden jig saw in a booth at the sea side. fascinating, the blade was very thin and narrow, consisted of 4 teeth in one direction then 4 teeth in the opposite direction followed by a space equivalent to the series of teeth, then another series of teeth. So it cut on the up and down motion. quite slowly, 2 strokes/sec?

Speed of motor is related to its construction (number of coils) and not its power. 1450 is a 4 pole motor, about 2900 is a cheaper 2 pole motor.

I some times mount a switched on jigsaw under a modified stool, so the blades pokes up where the seat would be. So its a bit like a fret saw with a thick black. I think this is the easiest way to go, do this with a spring loaded top support for your blade and you can be away in a day or so.

Frank
26 January 2016 at 20:41 #222730
Sam Longley 1
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@samlongley1
Posted by frank brown on 26/01/2016 20:31:43:

I some times mount a switched on jigsaw under a modified stool, so the blades pokes up where the seat would be. So its a bit like a fret saw with a thick black. I think this is the easiest way to go, do this with a spring loaded top support for your blade and you can be away in a day or so.

Frank

Actually I had thought about that. I have 4 or 5 jigsaws from my joinery business & had considered just making a blade grip. & doing exactly what you suggest. The variable speeds would enable me to experiment.to get best cutting speed. I already have a startright bandsaw

I just fancied trying some gear cutting & making the eccentric

Edited By Sam Longley 1 on 26/01/2016 20:42:33
26 January 2016 at 22:21 #222742
Emgee
Participant
@emgee
Sam

Check out the design used for the Emco Unimat SL jig saw, you have a lathe so just follow the SL design and build it to suit your machine, you won't need to worry about cutting gears as you have different speeds available on the lathe spindle. If you need pictures and dimensions of the SLdesign just ask.

Emgee
26 January 2016 at 22:50 #222747
daveb
Participant
@daveb17630
Not sure a stool is the best place for an upside down jigsaw, some of us are getting on a bit, could forget and sit down, probably jump up quicker too if a bit younger.
27 January 2016 at 10:15 #222780
Ian S C
Participant
@iansc
If you look at old copies of "Popular Mechanics" there are a number of scroll saw designs, some dating to before WW2, there are 3 in the PM book "Forty Power Tools You Can Make" published in 1941/42/44, you would find them on the PM web site.

Ian S C ps, I have a home made scroll saw that I got at a church fair, about the only metal is the table, the arms are wooden, as are the pulleys.
27 January 2016 at 15:19 #222825
Gary Wooding
Participant
@garywooding25363
Judging by the types of items you envisage sawing, I'd go for a scroll saw that uses piercing saw blades. I do a lot of piercing in my work as a jeweller, and I once purchased a Hegner scroll saw for the purpose. The good points were the Hegner reputation and the fact that it accepted piercing saw blades.

It was OK in most respects except it was too fast (60-110 strokes/min is ideal for piercing blades) and the stroke was nowhere enough to use the full length of a blade. A minimum stroke of 50mm (70 would be better if its adjustable) is required otherwise the blade is worn out over just a short section. I had the Hegner rep come to see the problem and the agreed that it wasn't suitable and accepted it back. Pity, 'cos it was a nice saw; just no good for piercing blades,
27 January 2016 at 16:16 #222830
Martin Kyte
Participant
@martinkyte99762
Here my take on this for what its worth.

1. The bigger the stroke the better. You buy the whole blade so use it.

2. Much lower speeds for metal than wood so ensure you have a good low speed range.

3. Engineer in a vacuum extract nozzle to clear the dust so you can see and for fibreglass material you don't inhale the stuff.

4. Maybe a fitting for a suitable magnifier.

5. CNC controlled material feed. (optional)

regards Martin
27 January 2016 at 16:56 #222837
Sam Longley 1
Participant
@samlongley1
Posted by Martin Kyte on 27/01/2016 16:16:38:

Here my take on this for what its worth.

3. Engineer in a vacuum extract nozzle to clear the dust so you can see and for fibreglass material you don't inhale the stuff.

4. Maybe a fitting for a suitable magnifier.

5. CNC controlled material feed. (optional)

regards Martin

The amount of GRP will be minimal. Just a few inches of cut per year. Possibly a bit more for thin brass etc

the idea of magnifier is sound

But as for CNC – not sure that is much use on a scroll saw
27 January 2016 at 19:14 #222853
herbert punter
Participant
@herbertpunter99795
This is worth a look

**LINK**
27 January 2016 at 19:19 #222854
Michael Gilligan
Participant
@michaelgilligan61133
Posted by herbert punter on 27/01/2016 19:14:43:

This is worth a look

**LINK**

.

It sure is

Thanks

MichaelG.
27 January 2016 at 20:07 #222863
frank brown
Participant
@frankbrown22225
Gary, same problem with jig saws cutting sheet steel, about 20mm blunt 30mm unused. Next time, sit the jigsaw on a 22mm bit of chip board sitting on the steel to be cut. You can now blunt the next 20mm.

Frank
29 January 2016 at 10:54 #223019
Robbo
Participant
@robbo
Sam,

Have sent you a PM re suitable motor

Phil
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