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Saws & saw sharpening

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Blog entry by rilanda posted 782 days ago 1441 reads 2 times favorited 1 comment Add to Favorites Watch

This is an article I found a few years ago, those of you who like to sharpen their own saws may find it of interest and perhaps useful. It refers to Photographs in parts of the text sadly after searching my computer for these photographs I have not found them, should they turn up at some time I will try to add them to this blog.

This article is specifically aimed at maintenance of handsaws of the “Western” world type including tenon, dovetail, and gents saws etcetera it does not embrace either “Japanese” type handsaws, or circular saws or band saws. The saw has been in use since the time of the Pharaohs some 4 ½ thousand years. Its sole purpose is to cut wood in either a straight line or a curved one depending on the type of saw and its design purpose. Modern saws are vastly different to those early varieties, the quality of the material they are made from is far superior, and the technology applied during the saws development has made a more accurate, efficient, and easier tool to use. Saws fall into several differing categories these are handsaws, backsaws, compass saws, pad saws, coping saws, & fret saws. With the exception of the fret, & coping saws they all cut on the push stroke of the sawing action.
HANDSAWS.
Handsaws [see drawing & photograph] are made from good quality carbon steel the best being produced in a rolling mill. They need to be flexible to allow the cabinetmaker some control over the cutting line by providing the ability to “turn the cut” as is required when “scribing”, (scribing is the term used to describe when a timber member is marked to fit up to a wall or ceiling and the saw is used to cut a wandering cut). Most handsaws are fitted with a closed wooden handle on the better quality saws; plastic handles are usually fitted to the cheaper saws. The saw blades are deeper at the handle (heel) than the toe, this provides the saw with some rigidity, and it gives the tool balance. Some manufactures will grind the saws thinner towards the back to assist with giving the saw clearance in the cut; this can also mean that less set would be required for that clearance. The saw blades are also tensioned during manufacture to stiffen the cutting edge while allowing the saw to remain flexible. Handsaws by the manner they are sharpened and length of blade would then be referred to as either ripsaws or crosscut saws. RIP SAWS [See drawing] are filed to the ripsaw tooth pattern usually 4.5 to 6 TPI (teeth per inch although some prefer to use the term points per inch PPI) and are commonly 26” long, they frequently have a taper ground back. Rip saws may also have smaller teeth at the toe end of the saw to assist the user in starting the saw in the cut on some older saws a start tooth (sometimes referred to as a grannies tooth) was cut into the back of the saw a short distance in from the toe of the saw. CROSSCUT saws [See drawing] are sharpened to the crosscut tooth pattern (6 to 10 TPI) and can be 26” long, this to can be taper ground to the back. The PANEL SAW is a shortened version of the crosscut saw (10 to 12 TPI) and is generally 22” long these may also be taper ground.
BACK SAWS.
This is a collective term for saws such as the tenon saw, and dovetail saw [see drawing & photograph] where the blade of the saw is captivated in either a steel or brass back that is tightly folded over the blade to keep it rigid. These saws have much shorter blades than handsaws and they are thinner, hence the reason for the back, they may also be fitted with an open handle (occasionally called a pistol grip handle). The 10” to 14” long tenon saw is sharpened like the crosscut saw, albeit with smaller teeth (12 to 16 TPI) as a compromise; the tenon saw is a saw used for most work therefore it could be used for both crosscutting and ripping timber. Crosscut teeth will rip but not as efficiently as rip teeth whereas rip teeth although they can cut across the grain will only do so by producing an extremely rough cut producing a lot of spelching. The saw can also be difficult to use with a constant jamming in the cut. The much shorter 8” long dovetail saw, because it is most likely to be used specifically for dovetailing should be sharpened with a rip like tooth (16 to 22 TPI) albeit a great deal smaller than the tooth of the hand saw.
COMPASS SAW.
This narrow bladed saw can be bought in sets with various lengths of blade 12” to 16” and an interchangeable handle from some manufacturers, although the usual way is a single bladed tool with a fixed open handle. They are used for cutting curved work and may be sharpened as a crosscut saw with 6 to 8 TPI. They need to be kept sharp and well set to allow the saw to cut freely around the curves. They can be susceptible to jamming in the cut with the subsequent buckling of the blade. They have been largely superseded with the introduction of the powered jigsaw.
PAD SAW.
This is a smaller version of the compass saw; it has a removable turned handle through which the blade passes held in position with a knurled thumbscrew. Sharpened to the same tooth pattern as the crosscut, like the compass saw it is very prone to buckling in the cut and has been superseded with the powered jig saw.
GENT’S SAW.
These are smaller versions of the backsaw, 4”, 6”, 8”, and 10” long with teeth of about 19 to 22 TPI; they are sharpened with teeth as the crosscut outline since as the tenon saw they could be used for many purposes. If the saw is used specifically for dovetail work then sharpen the saw to the rip outline tooth.
COPING SAW.
These are steel framed fitted with narrow pin ended blades 6” long and 14 to 16 TPI. They are used for fret cutting and cutting timber in difficult to reach situations. Usually sharpened to the ripsaw tooth outline they cannot be re-sharpened and require replacement when dull. They can be mounted in the sprung steel frame with the teeth cutting on either the push or pull stroke. My own personal preference is to cut with the teeth on the pull stroke; this will reduce the amount of breakages experienced when using this tool.
FRET SAW.
Very similar to the coping saw except the frame is much deeper to allow the tool to reach further into the work. The blades available are 5 ¼” long with plain ends and vary from an 11 TPI up to 60 TPI for use on precious metals. Also available are blades that are a spiral cut; this allows the saw to cut in any direction eliminating the need to keep turning the frame. Some blades are very fine and produce a very narrow kerf (the material removed by the saw on its passage through the wood) allowing the tool to be used cutting veneers for marquetry. The blades are fixed into the frame and held with two thumbscrews or wing nuts. As for the coping saw my own preference is to fit blades that work on the pull stroke.
PIECING SAW.
A smaller version of the fret saw and originally designed for the jewellery trade; it is available as either a fixed frame or an adjustable frame. The tool uses the same blades as the fret saw; it is in all other respects the same as the fret saw and will do similar work but of much, more limited nature.
SHARPENING SAWS
Saw sharpening can require four separate operations to return a saw from a bad condition to one in pristine condition these operations are:
 A inspection
 B topping-out
 C re-cutting
 D setting
 E sharpening
These operations should be carried out in that order if the work is to be successful in producing an evenly sharpened saw that is sweet to use. Not all saws will require this amount of work this being the worst-case scenario, some will require sharpening only, which is usually a relatively quick operation. However let us take each of these operations in turn and look at what is required for each.
INSPECTION
This is to determine how much work is required to return the saw to good condition a visual inspection of the saw and teeth. Hold the saw up to the eye and site along the tops of the saw teeth [See photograph] they should be even and either flat or with a slight convex curve along the tops of the teeth. The teeth should be all the same with the points terminating at the same height. Most saws will have a natural curve in their thickness imparted into it by the user this “bend” is natural. If the saw blade has a sudden change in direction within its thickness then the saw has been “snagged” (damage invariably inflicted during use, most probably to be caused by lack of set and rough use); this damage unfortunately cannot be rectified and is liable to lead to the saw developing a crack. Should the inspection reveal that the saw teeth are irregular in size and height then we need to move onto the next stage, if however the teeth are regular and even, check the set and decide if setting is necessary or not, a saw in this condition could then proceed to either setting and sharpening or sharpening only.
TOPPING OUT.
This is achieved using a 10” mill-saw file working along the tops of the teeth [see drawing & photograph] along the length of the saw. The saw is held in a saw vice during this operation and the file must be kept flat across the tops of the saw teeth and 90 to the side of the saw. This position must be maintained and any rolling action over the tops of the teeth must be avoided. A simple holder [See drawing] can be easily made to assist with maintaining the 90 angles and aids in safely holding the file [See drawing & illustration]; the direction to work is from the heel to the toe of the saw. Continue filing until all the teeth have been filed down to the same height as the lowest tooth, constant visual inspection is required to determine this point. NOTE: IF THE SAW IS ESPECIALLY BAD DO NOT REMOVE ALL THAT WOULD BE REQUIRED TO TAKE THE SAW DOWN TO THE LOWEST LEVEL HOWEVER MOVE ON TO THE NEXT STAGE AND RECUT THE SAW TO THOSE MARKS. NOW, RETURN TO THE TOPPING OUT STAGE AND TAKE THE SAW DOWN TO ITS LOWEST POINT, FINALLY RE CUTTING IT FOR A SECOND TIME. THIS PROCEDURE CAN BE REPEATED UNTIL THE SAW HAS BEEN CORRECTED. On satisfactory completion of this stage, you should check that the edge is straight and flat or very slightly convex it should NOT be concave.
RE-CUTTING
This is the most testing of the five stages; it is carried out using one of the following types of saw file.
 1 Mill saw file usually 200 mm or 250 mm long with either one round edge and one square or two round edges. This is the file to use for topping out; it was originally intended for sharpening circular saws.
 2 Taper saw file made in a number of lengths from 75 mm to 200 mm long
 3 Slim taper saw file available from 100 mm long up to 150 mm long.
 4 Extra slim taper saw file available from 100 mm to 150 mm long.
 5 Double ended saw file available from 150 mm to 200 mm long.
Selection of the correct file is important [see drawing & photograph]; for optimum results the width of the file should be a little more than twice the depth of the saw tooth [See drawing], the triangular files should also have a slightly rounded edge to avoid making sharp corners in the bottom of the saw teeth. It is also important that the saw should be mounted in a saw vice or stock; this can be a manufactured item (if they are still available?) or a self-made one [See drawing]. The one illustrated is a copy of the one I have been using for many years with several hundred saws having been sharpened within it. The main sections of the vice are made from 70 mm x 45 mm P.A.R softwood with two-ply reinforcements to strengthen the uprights. The uprights have a slot cut in the top that is 90 mm deep, 45 mm wide at the top; finishing with a 20 mm  hole at the bottom. The slot is then continued down a further 50 mm finishing with a 10 mm  hole to prevent the timber from splitting. The vice is held in the bench vice; it is important to make the height of the saw vice to suit the individual. To determine this height; it is the height when the saw file being held comfortably horizontal to the floor in both hands as if filing a saw. This is the height for top edge of the saw and the vice should reflect this. The saw cheeks are made from Beech or a similarly tough hardwood they have tapered slots in their side that correspond to the tapered slots in the saw vice they must be straight & flat and they must be a pair. They have cut backs at one end to allow the cheeks to pass over the saws handle. The saw is placed between the cheeks that are then as a unit inserted into the saw vice grooves it is then simply tightened up with a few light blows with a mallet.
To re-cut the saw fix the saw into the saw vice with about 6 mm of the saw above the vice cheeks; hold the saw file into a gullet so the file automatically assumes the angle of the gullet. The filing action should be slow deliberate strokes horizontal to the floor and square across the face of the saw. The file should always be fitted with a handle for safety; this should be gripped in the right hand with the thumb on top of the handle and the index finger down the side of the handle. This will fix the file orientation and allows filling to continue until the saw is complete. The flat tops produced by the topping out should all just be removed and care must be taken to try to keep the teeth even and all the same size and shape. Nothing should be done at this stage to bevel the teeth this being left until the final sharpening.
SETTING
Setting is bending the teeth alternately from one side then the other to produce a saw kerf that is not more than 1 ½ times the saws thickness [see drawing & photograph], this provides clearance for the sides of the saw. The most common error made during the sharpening process is to over set the teeth; to much set makes the saw less efficient and because it is producing a wider cut it will require more effort by the operator. A lot of saws are taper ground to the back to assist with clearance these saws will require less set than a standard saw. Setting is completed using a saw set; these resemble in some respects a pair of pliers. The saw set has a rotary anvil that is inscribed with number that represent the TPI of the saws this should be rotated until the number that correspond with the TPI of the saw to be set then locked into place. The saw set is place on top of the saw teeth with the hammer of the set lined up with the tooth. When the handles are squeezed together, the set grips the side of the saw before the hammer bends the tooth. This process is continued down the saw on each alternate tooth until the saw is completed. Then the saw is reversed over and the teeth are set from the other side. Points to remember when setting: -
 1 Deal with each tooth similarly using the same pressure on the saw set to ensure the setting remains even.
 2 Make sure the set is NO MORE than half the depth of the tooth maximum, one-third depth being the optimum. Setting the tooth from to low down can lead to tooth breakage.
 3 Do not over-set; aim for a saw kerf of approximately 1-½ times saw thickness.
 4 NEVER, set teeth from one direction to the other, this could seriously weaken the tooth ultimately causing it to break out of the saw.
SHARPENING
The saw can be sharpened in one of two differing manners, it will either be sharpened for ripping or for cross cutting.
RIP TEETH are sharpened with the file held horizontal and square across the saw [See drawing], this produces chisel shaped teeth that remove the timber in small curly shaped shavings. The procedure required to achieve this is as follows; -
 1 Fit the saw to the saw vice with approximately 6 mm above the vice cheeks.
 2 Select the correct file for the teeth to be sharpened; right width with rounded corners.
 3 Working from the toe of the saw towards the handle (butt) of the saw, file each alternate tooth straight across until that side has been completed.
 4 Reverse the saw over and file the remaining teeth from the opposite direction until that side is completed.
Sharpening the saw in this manner will produce a well-sharpened saw that does not run in the cut.
CROSS-CUT TEETH are sharpened alternately at an angle of 65 to 75 to the side of the saw to produce a point on the teeth. This point should be on the side of the tooth where the set is at its maximum [See drawing]. The points of the teeth incise the timber on either side of the kerf leaving the centre portion for the teeth cutting edges to break away producing what we know as sawdust. The procedure for sharpening a cross cut saw is very similar to that for the rip saw the major difference is the angle at which the file is presented to the saw this should be 65 to 75 from the side of saw. Each alternate tooth should be filed with the saw file held at this angle and presented to the saw to maintain the –14 angle of hook required for a crosscut saw. The procedure is down to grip and stance at the saw vice; the file should be level with the floor, the file gripped in the right hand with thumb on top of the handle and index finger down the side of the handle. The left hand should be firmly gripping the leading end of the file; lastly, the feet should be spread apart to give a firm base. Sharpening should be a slow, methodical, but determined action with constant observation taking place.
BACK SAWS
The same process is required to service all back saws however the cutting edge should be straight; as previously mentioned the tenon saw because of its general purpose use is invariably sharpened as a cross cut. The dovetail saw because it is most likely to be used for the purpose it is designed for should be sharpened as a rip saw. Albeit the teeth of these saws are much smaller than handsaws, the hook, and angle across the face of the tooth should be the same in both instances. Sequence should remain the same and the depth of set should reflect the height of the tooth to which it is being applied.
Final note all saws with hardened teeth (sometimes called HARDPOINT) cannot be sharpened or even re-set; once they become dull they are only suitable for the scrap metal bin and a new one must be purchased.
FOOTNOTE
Master the skills of saw sharpening and it unlocks a number of doors that before would not have been possible. Over the years, my selection of handsaws and backsaws has grown with the addition of saws purchased from car boot [See drawing] sales for a pittance. These were inspected before purchase for faults that would render the saw as scrap for example seriously snagged saws and saws that are cracked, also heavy corrosion would deter me from buying a particular saw. The shape of the teeth and a coating of light corrosion would not prevent me from purchasing a saw. I would then look for a name on the saw or a medallion in the saw handle to determine if possible the saws original manufacturer. However even without this information if the saw looked right, I would buy it and search for the makers name during the cleaning up. If the saw was right but with a broken handle I would still buy and either repair or make a new handle for the saw. The saws I now possess include Philadelphia Henry Distons, Spear & Jackson, Taylor Brothers of Sheffield, and Tyzac, and several other eminent saw manufacturer’s saws. These are superiority saws that have over the years given me good service and will no doubt continue to do so, they are equal to in quality and performance to many of the modern quality saws that are available today. Invariably they would have been bought for £0.50p to £1.50p each, however, some work is required to put them back into service, but that can be a pleasure.

Regards

Bill

-- Bill, Nottingham. Remember its not waiting for the storm to end, but learning to dance in the rain that counts. If you dont make mistakes, you make nothing at all.



1 comment so far

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Brit

5127 posts in 1477 days


#1 posted 782 days ago

Thanks for posting this Bill. When you have some time, I’d love to see some photos of your saw collection. I’m sure many others would too. I’ve yet to buy a decent saw in the £0.50p to £1.50p range, but I live in hope. LOL.

-- Andy -- Old Chinese proverb say: If you think something can't be done, don't interrupt man who is doing it.

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