power hack saw

[dkwflight]

Hi
I recently purchased an old cast iron power hack saw.
I am in the process of making bushings and replacing a 1" bar the big gear runs on.
I had to make a blade tension lever that was missing. It runs 12 inch blades.
I need a motor. Harbor freight has a 1/2 HP unit that should be satisfactory.

 

[Wizard69]

You probably could get away with 1/3 HP. The motor is geared down a lot and assuming hacksaw blades for hand sawing shouldn't see a massive load from cutting.

 

[dkwflight]

You are right.
I mounted a hand saw blade and did some sawing turning the pulley by hand.

 

[Wizard69]

You are right.

I mounted a hand saw blade and did some sawing turning the pulley by hand.

Now that i think about it, the trick will be finding the right motor RPM. This will likely require determination of the belt "gear" ratio so that you end up at the right SPM.

 

[velocette]

.
Hi
a couple of pointers Aim for 60 to 80 strokes per minute with the crank turning Anti Clockwise cutting on the pull stroke.
I.E. teeth cutting to the right.
Hand Hacksaw blades work OK is smaller machines well tensioned and up to about 5 kgs weight of frame
Keep us posted on progress

Eric

 

[dkwflight]

Hi Thanks for the tips.
I think my Dad had one about 50 years ago. I did not pay much attention and I don't thik I saw it operate.

I was wondering which direction to turn the pulley.
THis machine does have a spring connected to the frame arm by way of a cam on the big gear.
I thought it was to add some pull down on the cutting stroke.
It may be to add some pull down on the idle part of the stroke.

I am looking for a small motor at a good price.

I have been looking at the saw and the cam timing.
Looking at the connecting rod and turning the pulley, top to the frame. the cam lever pulls the frame down as the big end of the connecting rod goes over the top. This will pull the frame down on the out stroke. This would increase the down force on the frame.

Turning the other direction top of the pulley away from the frame the spring force would pull the frame down. I think this would pull the frame down in the cut.
I guess I will have to try both directions to see how smooth it is.
I will be looking for a reversible motor, maybe a two speed blower motor.

 

[terrywerm]

Some people will tell you that bandsaws are the only way to go, but for a few of us a power hacksaw has a certain therapeutic effect while it goes about its business, moving to and fro.

Most power hacksaws cut on the draw stroke, in other words while pulling the blade toward the crank. The blade should always be cutting while trying to keep the stock tight against the stationary vise jaw. Looking at the photo of yours, it follows that method. Based on that, and what you have said about the mechanism providing downward pressure when the connecting rod passes over the 'top' of the stroke, it appears to me that your crank should rotate in a clockwise fashion when the saw is running. This assumes that you are looking at the saw the same way as your photo was taken.

 

[dkwflight]

Hi
Youtube has a number of power hack saw vids.
Interesting.
Most by far most are cutting with the connecting rod pulling on the bottom of the gear.
This pulls the blade down into the cut .

The better old ones even have mechanisms to lift the blade away from the cut a bit on the return stroke.

 

[Blogwitch]

Some people will tell you that bandsaws are the only way to go, but for a few of us a power hacksaw has a certain therapeutic effect while it goes about its business, moving to and fro.

Like if you are cutting a bit of 2" diameter bar, it is so therapeutic and relaxing, you can go indoors, make lunch for 4 people, eat it and wash up afterwards, and if you are lucky, when you go back in the shop it should be almost finished cutting.

I bought a rather expensive new power hacksaw from Sieg that used rather good 12" x 1" blades, and that was s o o o slow for cutting I sold it and bought a super fast cutting bench bandsaw instead. Cuts a 2" billet in less than a minute.

John

 

[Mechanicboy]

I bought a rather expensive new power hacksaw from Sieg that used rather good 12" x 1" blades, and that was s o o o slow for cutting I sold it and bought a super fast cutting bench bandsaw instead. Cuts a 2" billet in less than a minute.

John

A super fast cutting bench bandsaw means you will save electricity bill. :thumbup:

 

[DERoss56]

looks like you have a model 3100 sawmaster. they are "push cut" saws so the teeth should point towards the moveable vise jaw. They have an 8" drive pulley which will operatemachine at 90 to 100 strokes/minute with a 1725 rpm motor with a 2-1/4" O.D. pulley. A 1/3 H.P. motor is more than adequate. Gear rotation is counterclockwise when viewing from gear side of saw, otherwise pressure on blade won't be applied at proper time on forward stroke, and blade lifts on reverse stroke from cam on shaft behind gear. I've got 2 of 'em, a 3100 & a 3101, use 'em a lot even though they're slow, love 'em.


Regards, Doug

 

[dkwflight]

Hi
I just looked at the tag. It is a 3100.
Thank you for the info.
You are sure it is a push cut?
Of all the Youtube vids I only saw one push cut.

 

[DERoss56]

Yep, all sawmasters are push cut & saw lifts on reverse stroke.
It's in their manuals which you can down load from vintage machinery.org and some other sites on the web.


-Doug

 

[dkwflight]

thanks
I did find a manual that covers the 3100 and other sawmaster saws.

 

[dkwflight]

Hi
The saw is now operational. It made its first cuts under power with w hand hack saw blade 32TPI.
Naturally it is slow but the cuts are good and square enough.
10tpi and 14 tpi blades coming.

 

[dkwflight]

A vid clip experiment.

did not work

 

[dkwflight]

[ame]https://www.youtube.com/watch?v=soH9kqa4QcM[/ame]

 

[Wizard69]

Hi
The saw is now operational. It made its first cuts under power with w hand hack saw blade 32TPI.
Naturally it is slow but the cuts are good and square enough.
10tpi and 14 tpi blades coming.

That is a quick rebuild and paint job! Looking pretty.

 

[ROB 123]

that's a really nice job.
Rob.

 

[dkwflight]

Thanks for your comments.
I am pleased with the speed of the cut even with the 32tpi hand saw blade.
The down pressure in the cut from the red handle and spring adds pressure in the push direction speeds the cut. Maybe you can see the spring connected to a cam follower in the shadow below the red knob.
You can see I dd not build a stand.
I intend to store the saw under a bench, maybe some casters to help slide the saw out for use. Small shop space!