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A good way to add a variable speed controller for my re-made Hobbies fretsaw. Answered

Hi folks.
I did ask this in the questions section but only got one reply which suggested I didn't really need one so I thought before I start on it I would give the forums a try.

I have decided I want to add a variable speed foot controller to my re-made hobbies fretsaw.

https://www.instructables.com/id/1950s-Hobbies-treadle-fretsaw-remade/

My question is what do you guys out there think would be the easiest, least costly (cheap) way of doing it?
I have given some thought to using a foot controller from a sewing machine possibly because this thing started life as a treadle fret saw & I guess it seems fitting that it should follow a similar evolution as the sewing machine.
I know very little about sewing machine controllers so if anyone has any ideas regarding this I would welcome them.
I plan to include an isolator switch on the machine itself, it seems a good idea as we have a small grandson who visits very often as well as two dogs & 'ible the kitten, as much as I try to keep them out of my tiny workshop it sometimes seems as if I am the only person in the house who has mastered the skill of closing the door so with all those feet around I want to be able to kill the power when I am not actually cutting.
I plan to do an 'ible about the job so I will happily give credit where it is due to any to any body/bodies that comes up with any ideas I use.
So there you go guys what does the combined genius of the 'ibling world have to suggest for my little project?

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steveastrouk (author)2010-11-06

Looking at it, a sewing machine motor on its own is probably too small. How many RPM is the old motor making ? That looks to me like an old washing machine motor, so reckon on ~500 W ?

Steve

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user

As I said in the 'ible I believe it is a washing machine motor, if you look at the pictures where the back of the saw is facing the camera you can make out the belt guides on the shaft.
As it was already like this when I got it I have no idea of the wattage of the motor, unfortunately it has no plates or any other identifying marks apart from the letters SF paint stamped on the casing nor do I have any idea of the rpm although that is one of the things I want to figure out today, I do have a motor I salvaged from a washing machine I scrapped a few weeks ago so I may look into the possibility of using this instead if I have to.
Do you think I could use a foot controller from a sewing machine on it? I have one I could "borrow" from our sewing machine & am quite certain I could get a more permanent solution from my FreeGLE group or the local car boot sale Sunday afternoon.

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user

Modern-ish WM motors are brushed and speed controlled by a separate board. See if you can find that.

STeve

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user

PS A sewing machine controller will MELT on a WM motor load.

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user

A very good point I hadn't thought of that Doh!!!!!!
I believe the one my friend had was actually cobbled together using an electronic fan speed controller from an air conditioning unit, we used to run an air conditioning company together so he had access to plenty of this kind of thing.
I am beginning to think I may have to go for a simple on/off foot switch & keep an eye out for something to give me the variable speed option later on.
I want to use it to make some things for Christmas gifts so I need to get it sorted quite soon.

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user

I think that may be going a bit too far :-)
To tell the truth I have thought about doing a web search & finding myself a new saw with all the whistles & bells but I seldom use it & would rather spend the money on building either a much bigger or second shed to use as a utility room so I can have a decent sized workshop without sharing it with a half ton of appliances.

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user

TBH, the motor looks about right, at 1/4 horse for what you have. To speed control that you need fancy.

Axminster do some nice saw stuff. I've got one of their fretsaws too.

Steve

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user

You are probably right but to fair I really couldn't justify paying out £140 to upgrade a anicent saw like this when I could pick up a secondhand bargain like one I saw on ebay this morning which went for a little over £45.00.
I would prefer to use the cash to buy the rest of the materials I need for my better half to have the outside utility room she wants so dearly.
I seldom use this saw so whatever I do to it has to be as cheap as possible, if that means merely having an on/off footswitch & waiting for a while to get a better one then so be it.
You have given me an idea though, I may get in touch with a guy from my old pub who works for a local tool sale/hire company & see if he can get hold of something re-conditioned.
Thanks for the pointer. :-)

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NachoMahma (author)2010-11-05

.  How variable is variable? Would a step pulley work for you?

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Nostalgic Guy (author)NachoMahma2010-11-05

That could be a good option I will have to see what I can pick up locally or online to build it as I certainly have nothing in the workshop.
I spent a few years as a machine shop setter/manager so I am quite familiar with step pully setups.
I would really prefer something a bit more along the line of what I used before which was controlled completely by the variable control in the foot switch, it belonged to a friend I have not seen since he left town, I belive it was very much a home brew setup but it worked really well especially when working with very soft wood.

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steveastrouk (author)2010-11-05

Well, you could use a sewing machine motor and controller.
Does the motor have brushes ?

Steve

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user

I know it may sound daft but until you asked it hadn't even occurred to me to look :-)
The better half & I are babysitting the grandsons tonight so I am being actively discouraged from spending my time locked away in a room alone with machinery (I'm not allowed to go play) but a cursory glance says no, there are no external signs of it having brushes that I recognize from any motor I have worked on before, I must admit however my experience is limited to a few domestic appliances like vacuum cleaners & washing machines & certainly nothing as old as this one, I will have a proper look in the morning.
Would a sewing machine motor be powerful enough? I have cut steel sheet & 1" hardwoods with this without a problem & am planning to make some quite detailed small pieces from steel when the saw has been modified either to a variable speed or simple on/off foot switch.

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