Hand-Powered Saws for Milling Logs

A discussion of pit saws and an idea for adapting a bandmill blade for a hand-powered frame saw. May 11, 2005

Question
I would like to saw a few logs every once in a while on a serious budget, and am not afraid of hard work. I was thinking about buying a band sawmill blade, cutting a three foot section, and stretching it in a rectangular wooden frame like an old frame saw. Something like an old pit saw, without spending $100 in an antique store for a rusty piece of crap. Does anyone have suggestions as to the best blade width/size/etc. and who sells individual cheap bands instead of a ten pack?

Forum Responses
(Sawing and Drying Forum)
From contributor B:
You might consider finding someone local with a band saw that does custom work - you could probably buy one there. I think you are biting off a great big job. The teeth on my WM are 7/8" tooth spacing. For hand application, that would be like driving a nail in the log and trying to rip it out. Closer tooth spacing would help. I can not even imagine the time involved. The old timers did not use the pit saw because of efficiency; it's all they had.

Most commercial bands will not actually be flat, but have a curve in them, edge to edge, to assist in keeping them cutting flat as they spin. This will be a problem for you. In your frame, you will need a very wide blade to keep it cutting straight, as you probably cannot get the tension on the blade that we would find in a commercial unit. Being real honest, I do not think that you will find this to work very well. Remember that for each blade, you will need probably 50 hp. You also need a way to hold the log stationary as it enters the cut, is in the cut, and is leaving the cut. A frame saw makes a great boat anchor because of all the steel required to keep it from bending or moving. Why not contact WM and ask for their listing of custom sawyers? It would be cheaper to pay someone a couple times a year than to pay the bank every month. I hope you feel that I am negative about your idea... I worry about safety and performance issues.Here is a picture of a frame resaw that I made to resaw crotches and boards that are too wide for my band saw. The blade is a wood cutting blade 3 tpi, 1 1/4" wide x 4' long. Unless I read your post wrong, I can't imagine anyone using this kind of saw to lumber a log! But I've seen prints of old timers cutting veneer out of a log with one of these saws.

Re: Hand frame saw with band sawmill blade Mike Shenton 12/6You can still buy new pit saws. I have a catalog from People Powered Saws (I think) that has them in it.Re: Hand frame saw with band sawmill blade fp-vt 12/6How long did it take to saw that slab like that? At one time, maybe I'd consider trying my hand at it. I have even watched 2 man pit sawing at colonial Williamsburg. While it was partly exhibition and partly the way it was done, looked like it took a day to saw once through a 12' log.Surprisingly, not long. I believe it took less than an hour. The piece was an 8/4 walnut crotch that I resawed into four boards. Here is a closeup picture of the blade resawing a 4/4 butternut board. The saw cut the butternut a lot faster than the walnut, though. If anyone is interested in making one of these saws, the plans are in Bob Moran's book, "Woodworking: The Right Technique" published by Rodale Press, page 282.

I'm very interested in purchasing a pit saw. Crosscut Saw Co. in NY used to sell them, but no longer. I've been unable to find a supplier.crosscutsaw.com still has a few unhandled pitsaw blades. These are unsharpened. My check for one has cleared and I'm waiting for it to arrive. I found instructions for sharpening it in The Woodwrights Companion, ISBN 0-8078-4095-5.

Description

E-70A edge banding machine adds a cutter pneumatic adjustment function compared with the E-70 model edge bander. It can realize multiple functions in edge banding process automatically and quickly. For example, edge banding, end cutting, rough and fine trimming, tracking and corner rounding, scraping, polishing, etc. It is an indispensable edge banding machine for cabinet and office furniture making.

Features

1. The pneumatic adjustment function allows the operator to adjust the edge band thickness from the screen directly.
2. This model of edge banding machine is provided with the profile tracking and trimming function, which can make the banded panel corners more smooth. The self-designed tracking motion and gas circuit stabilize the tracking and rounding process.
3. The high-strength aluminum alloy structure ensures stable, safe, and efficient edge banding operation.
4. It adopts an industry-leading touchscreen, which has a friendly man-machine interface and quick response.

Parameters

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Frequent Asked Questions

Does this edge banding machine need air compressor? How much power?

What glue can this edge banding machine use?

What materials can be banded with this edge banding machine?

The Swedish sawmill industry has expressed an interest in the optimisation of bandsawing and the development of thinner cutting teeth. This allows for the production of a larger volume of timber while reducing the waste products such as sawdust and chips. The benefits are furthermore both economic and environmental as not only is waste reduced, but the volume of end products that can bind carbon dioxide for a longer time is increased. When developing more efficient bandsawing cutting tools, the cutting forces need to be considered with respect to the tooth geometry, such as the major cutting edge, clearance and cutting angles as these can increase the sawing yield and affect the cutting process [1,2,3].

The cutting geometry of a bandsaw tooth can be seen in Fig. 1 according to the ISO 3002:1 standards [4]. Note that the teeth are symmetrical in X-direction. The width of the major cutting edge (\(S_\text {t}\)) is a crucial geometrical feature of a saw tooth as it is responsible for the extent of material removal. Sawing teeth also have a clearance (u) (distance between the tooth tip (\(S_\text {t}\)) and the band (S): \(2u=S_\text {t}-S\)) which avoids contact between the back of the band and the wood as the cutting teeth create kerfs. The minor cutting edge angle, \(\kappa _\text {r}'\) (also called the radial clearance angle), as well as the uncut chip thickness, \(h_\text {m}\), is largely responsible for the minor cutting edge geometry interacting with the wood (see Fig. 2). The combination of the minor cutting edge angle, \(\kappa _\text {r}'\), and minor cutting edge clearance angle, \(\alpha _\text {p}'\) (also called the tangential clearance angle) determines the geometry of the minor first flanks, \(A'_{\upalpha 1}\) (also called the side faces).

Geometry of a single cutting tooth used in wood sawing according to ISO 3002:1 [4]

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Faces and cutting edges of a wood saw tooth according to ISO 3002:1 [4]

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The three principal forces acting on a saw tooth

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Wood is an elastic material and therefore when it is cut, some of the fibres bend over instead of being broken. These fibres return to their original position after the cutting edges have passed which is known as elastic spring-back. The wood that has sprung back will make contact with the minor first flanks, \(A'_{\upalpha 1}\), and major first flank, \(A_{\upalpha 1}\) (also called the clearance face). The elastically sprung-back wood will also lie in the cutting path of the consequent tooth, leading to an increase in friction.

The forces that act on sawing teeth are one of the factors that describe the overall cutting process. Others include the surface roughness of the workpiece, temperature, vibrations, etc. The conventional forces on a cutting tooth are defined by the cutting force (\(F_\text {c}\)), the feeding force (\(F_\text {f}\)), and the lateral force (\(F_\text {p}\)) (see Fig. 3). The cutting force (also called the main or parallel force) is responsible for material removal and is consequently the highest force. It acts on the tooth in the opposite direction of the bandsaw cutting movement, \(v_\text {c}\), which is linear in bandsawing. This force occurs on the major cutting edge but also on the minor cutting edges, depending on the uncut chip thickness (\(h_\text {m}\)). The cutting force can be split into different components as shown in Eq. 1 [5]. This equation states that the cutting force can be split into the force acting on the major cutting edge (\(F_\text {cS}\)), the force acting on the two minor cutting edges (\(F_\text {cS'}\)) and the friction force between the two minor first flanks and the workpiece (\(F_{\text {cS'}\upmu }\)):

$$\begin{aligned} F_\text {c}=F_\text {cS}+2F_\text {cS'}+2F_{\text {cS'}\upmu } \end{aligned}$$

(1)

Equation 1 can be modified to clearer distinguish between the different force components as show in Eq. 2. Here, the cutting force acting on the major cutting edge (\(S_\text {t}\)) is given by \(F_\text {cS}\), and the friction force between the elastically sprung-back wood and the major first flank (\(A_{\upalpha 1}\)) has been separated from \(F_\text {cS}\) and is given by \(F_{cS\upmu }\). This is indicated in the red Zone I in Fig. 4 and it represents the major cutting edge cutting. The cutting force on the minor cutting edges (\(S'_\text {t}\)) is given by \(2F_\text {cS'}\) and the friction forces on the two minor first flanks (\(A'_{\upalpha 1}\)) is given by \(2F_{\text {cS'}\upmu }\). These force components are indicated in the green Zone II of Fig. 4. To distinguish between major and minor cutting edge cutting, the equation has been split into two parts denoted by \(F_\text {I}\) and \(F_\text {II}\), each representing a different zone in Fig. 4. This paper concerns the force contribution from Zone II and is defined by \(F_\text {II}\) in Eq. 4:

$$\begin{aligned} F_\text {c}&=F_\text {cS}+F_{cS\upmu }+2F_\text {cS'}+2F_{\text {cS'}\upmu } \end{aligned}$$

(2)

$$\begin{aligned} F_\text {I}&=F_\text {cS}+F_{cS\upmu } \end{aligned}$$

(3)

$$\begin{aligned} F_\text {II}&=2F_\text {cS'}+2F_{\text {cS'}\upmu } \end{aligned}$$

(4)

$$\begin{aligned} F_\text {c}&=F_\text {I}+F_\text {II} \end{aligned}$$

(5)

When the major cutting edge is reduced, \(F_\text {I}\) is reduced, but the force contribution from Zone II, \(F_\text {II}\) remains constant and will therefore have a larger influence on the overall cutting force, \(F_\text {c}\). The force contribution from the minor cutting edges and the friction force between the minor first flanks and the workpiece, Zone II, has scarcely been investigated in literature. As the industry is moving towards smaller major cutting edges, it is crucial to better understand the contribution of these forces to the cutting force, and to pay more attention to the minor edge geometry and minor first flank geometry. Furthermore, when the Zone II cutting increases, the wear behaviour of the cutting teeth as well as the temperature distribution in the tooth can change, which could lead to tooth failure and instabilities during sawing.

The cutting force can be divided into two zones: Zone I major cutting edge force (\(F_\text {cS}\)) and friction forces on the major first flank (\(F_{cS\upmu }\)) and Zone II minor cutting edge forces (\(F_\text {cS'}\)) and friction forces on the minor first flanks (\(F_{\text {cS'}\upmu }\))

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Definition of cutting directions. Cutting force tests were made in the 90º–90º cutting direction, i.e. the cutting edge and the feeding direction were 90º to the longitudinal fibre direction of the wood

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Cutting by the minor cutting edges occurs in a different direction than cutting by the major cutting edge. For example, when the major cutting edge is cutting in the 90º–90º direction, the minor cutting edges cut in the 90º–90º direction, or in a 2º–90º if the minor cutting edge angle is 2º (see Fig. 5). The first number in this notation indicates the cutting edge direction with respect to the fibre angle, whereas the second number indicates the movement direction with respect to the fibre angle [6]. The cutting direction can significantly affect the forces [3, 6,7,8,9,10,11,12]. Cutting by the minor first flanks of the tooth occurs at 0º to the fibre angle and the tooth is moving in a direction of 90º to the fibre angle, a cutting action similar to veneering. Cutting in this direction has significantly lower cutting forces [6, 13]. Li et al. [3] found that Zone II cutting contributes up to 7% to the cutting force in the 90º–90º direction, but they found that the Zone II force contribution can be as high as 16.9% in the 0º–90º, where Zone II cutting is occurring in the 90º–90º direction.

The Scandinavian species Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) are processed in all environmental conditions, even when temperatures drop well below zero. Sawmills, therefore, process frozen logs, non-frozen logs and dry wood. This study considered Norway spruce and Scots pine in frozen, non-frozen and dry condition. The Zone II force contribution was analysed while changing the major cutting edge as well as the clearance, minor cutting edge angle (\(\kappa _\text {r}'\)) and minor cutting edge clearance angle (\(\alpha _\text {p}'\)). To the author’s knowledge, the minor cutting edge force contribution has not been reported in previous literature. Thus, this research can provide insight into the force behaviour on the minor cutting edges, especially as the industry is moving towards more efficient sawing with optimised cutting tools.