Backsaw tutorial.

[swagman]

Hi all. I recently completed a backsaw tutorial on a different woodworking site after receiving the request to do so.

Here it is.

Stewie;

The saw bolts I use are suited to a maximum handle thickness of 23mm (flush on both flat faces). Allowing for a little extra to cover later flat sanding, my starting thickness for most of my handle blanks is 24mm, dressed on both sides.
A solid template of the handle design I am going to use is then traced onto the handle blank face and cut out with a scroll saw.

I then check to insure all the edges around the handle shape are at 90 degree's to the face side. if there out I will use a fine rasp to make the required adjustment.

For this handle I am using a new design I came up with. Its looks good in non 3 dimensional form as a drawing, but I will have a better idea near the end of the backsaw construction if this design ticks all the boxes from a visual perspective. The handle wood I chose is Tasmanian Tiger Myrtle.

Here is the handle after the steps mentioned above were all followed but additionally I have drilled and installed the 3 saw bolts. As you will note I have left saw bolt nuts on the non face side of the handle slightly below the flat surface. This will prevent the depth of adjustment slots from being worn down by later flat sanding.





Moving on to the installation of the saw bolts. If your after a neat tight finish with the saw bolts I would recommend you try an alternate method to that of a forstner bit. As they are generally not available with a pilot guide, its very easy to end up with a slightly oversize or elongated fit that mars the final appearance of your saw handle. A better option is to look at purchasing a pilot counterbore with a depth stop fitted. The type I use has a 3/16 pilot rod and a 1/2" main bore. Klaus & Isaac got me into using this method of installation and the results have been high quality. Here's the a photo of the pilot counterbore I am using. It comes standard with the 3/16 drill bit. The depth stop and 3/16 pilot rod are not supplied. I wont mention the supplier but if you have a look on ebay you should be able to track one down fairly easy in the size your after.



When it comes to cutting the blade slot for the handle it can be done in a few different ways. What suits me is to use a slitting blade that's fitted to a bench mounted router. It cuts a starting slot that I can later deepened to the full depth with a backsaw. I wont go into much detail on how best to set up your router table to this job as its a post topic on its own. Other than to say the speed of the router needs to be slowed down to accurately slot the handle.

I know Dom is now using this method for his saw handles, and he may wish to add a post on this subject if you make the request.

Here's a photo I took a while ago when I testing my set up on a scrap handle.



Moving on to the brass back fit within the handle mortise. Because I prefer to keep the top line of the brass back flush or slightly above the top mortise line of the handle, mortising down the full depth of the brass back height 19mm
would leave my 2 top saw bolts much lower than I would prefer. A tip I picked up from Klaus & Pedder with the construction of their backsaws it to create a stepped tenon and mortise fit.to As you can see on the following photo I have shaped the tenon so that it depth decreases by 5mm. I have also cut the length of the tenon so that the step down will be 5mm inside the handle to create a stronger union.




I wont bother detailing the process involved in cutting out the mortise itself other than to mention I use the router table with the slotting blade fitted to cut each side of the mortise which is then cleaned out with a mortise chisel that's 1/4 " width.

As you will see from the next photo I have completed the handle mortise and have fitted the blade assembly to the handle. As mentioned early I made sure that the top line on the brass back lined up with the horizontal line marked previously on the handle, prior to drilling out the saw bolt holes on the saw plate. Once fitted, the toe of the brass back and saw plate were measured then cut to size. I also have shaped the heel of the saw plate to a curve that follows the cheek shaping.




On this close up photo of the handle, I have darkened the area of the cheek to best represent the way I have slotted the handle for the blade fit. Because I wanted this slot to also pass through the full length of the handle mortise I have cut the slot in 2 passes. The 1st pass is on the angled line, and the 2nd pass is from the back of the mortise vertically down.

 

[swagman]

Here are the rasps I predominately use to shape my backsaw handles. I can highly recommend the 2 Logier Modellers Rasps in 14 & 15 Cuts as well as the Japanese Feather File. The teeth on the Gramercy Rasp are not as good as the hand stitched Logiers. Logiers Curved Handle Makers Rasp would be far better option to purchase with its additional curvature and hand stitching. http://www.hand-stitched-rasp-riffle...aker-rasp.html



From top to bottom. Logier Modellers Rasps 14 & 15 Cut. (150mm x 11mm x 3.5mm.) http://www.hand-stitched-rasp-riffle...s/effilee.html ; Gramercy Tools Saw Handle Makers Rasp http://www.toolsforworkingwood.com/s...m/GT-SHRASP.XX ; & a Japanese Feather File (100mm).

I have marked both flat faces of the handle ready for rounding the outside of the handle grip. The 2 outside lines marked on the edge grain represent each side of the brass back mortise, while the 3rd line is the centre thickness position of the blade slot.



Here you can see that I have finished rasping the rounded profile to the outside grip, and have started to smooth this area off 150 grit sandpaper. Before commencing the sanding I applied a coat of shellac. This will help me to removing any high or low spots and indication how close I am getting to the profile line marked on both flat faces of the handle. After this 1st sanding, I then recoat the area with shellac and sand again with the same grit to make sure its perfect. The ends of the top and bottom horns will also be shaped and sanded and sanded smooth. When complete I recoat the outside grip with shellac ready to move on to the inside grip and cheek line.







The inside grip and cheek line profile marked onto the 2 flat faces of the handle ready for rasping.

 

[swagman]

In this photo I have finished rasping the profile to the inside grip and cheek line. Next I coat the area with shellac and then start smoothing off with 150 grit. Then repeat the same process again with 150 grit to make sure its nicely rounded. Another coating of shellac is then applied before moving onto to shaping each side of the mortise area as well as rounding off the front toe to the inside grip.

Notice the reasonably good finish left after using the Logier 14 Cut to ruff out the waste, then redoing this same area again with the Logier 15 Cut but with much more care taken to get closer to the flat face profile mark.



The handle after all the shaping has been completed and sanded with 150 grit. The handle is shown after its been recoated with shellac ready for the next stage of 220 grit.



Here you can see the handle after being fully sanded using 220 grit.



The handle after being fully sanded using 400 grit, and recoated with shellac ready to be sanded with 800 grit.




I primarily using the shellac as a grain filler. As I work through the finer grits of sanding what I am aiming for is to reduce the depth of any fine scratches upon the wood surface. Everytime I recoat the handle with shellac and change to a finer sanding medium these scratches get smaller in size and become less and less apparent with the ultimate goal of creating a totally flat flawless surface that is able to reflect light and create shine. It is the shellac that is imbedded within the pores and grain of the wood surface that also create the colour change. The intensity of that colour change can be controlled to a large extend by the type of shellac used. Garnet, Amber, Blonde. As a further example of the technique I use, when I flat sand the face grain of the handle I am using the last coat of shellac to tell me how well I am progressing at getting the handle face completely flat. Any part of the surface that is not dulled through sanding will show up as being shiny, letting me that I need to sand further until all this shine has been removed. Enough explaining, lets move onto another photo that shows the handle after being sanded with 800 grit, recoated with shellac, then sanded with 1200 grit, and then its recoated again for the next stage of 2000 grit sanding.



While I leave the handle shellac to further harden before final buffing its a good time to start filing the flat bevels on the brass back.

 

[swagman]

Finished shaping the bevels on the brass back. This was later sanding to remove any fine scratch's. I will give it a spit and polish with brasso later on.

The handle received its final sanding with 2000 grit, a single coat of paste wax, then mechanically buffed. I will give the flat faces of the handle another coat of wax after the backsaw is totally completed.









I decided to go ahead with the idea of filing the teeth progressive tpi.

16tpi 2 1/2" from the toe, followed by 14 tpi. Soft rip tooth.





Preparation.

Adhere the paper tpi template to the top edge of the saw plate.

I also apply a strip of 2" masking tape to each side of the saw plate, to protest the plate from scratching up while in the saw vise.

Working from heel to toe I use the jewellers 3 square file to lightly notch the V position between each tooth.

The paper template is then removed without disturbing the masking tape.

Shaping the teeth. Soft rip tooth.

The normal process I follow during shaping is to apply a full stroke of the file to each V, before moving on to the next one.

Because I am using 2 different sizes of tpi this time around, I will only apply a full stroke of the file to each tooth position up to where tpi changes from 14tpi to 16tpi. That way I have a greater chance of keeping the flats on all the teeth as close to the same width the deeper I file the V's.

On the 2nd run, the same full stroke with the file is completed but I also pick up the section of 16tpi at the toe end of the tooth line.

After the 3rd run of filing, any tooth that has still has more flat on average to the majority of the teeth will need additional attention on the next run.

Make the decision if the teeth need to be jointed prior to commencing next run.

On the 4th run of filing I am purely focused on evening the size of the flat to each tooth.Where the flats are too great between to adjacent teeth I add a 1/2 stroke of filing. Where single tooth stands alone I rotate the cutting edge of the file slightly forward and apply a half stroke to the non rake side of the tooth.

Joint the teeth prior to commencing next run.

On the 5th run of filing. With all the flats in correct proportion to each other its now time to add enough file stroke to each V that the flat left to each tooth is a very fine line.


Make the decision if the teeth need a final jointing prior to commencing next step.


Note: I generally joint the teeth 3 times on average prior to applying any set.


Applying set.

It is at this stage before final sharpening that I like to apply the set to each tooth. Light pressure is only needed. This will be later fine tuned.


Sharpening.

After applying the set to each tooth, its now time to remove the remaining flat to each tooth; creating a sharpened point to each tooth.

Fine Tuning Set.

A high performance backsaw will generally have minimal set remaining to each side of the saw plate. There is a couple of options available to fine tune the tooth set. One includes stoning each side of the saw plate. I prefer to use the other method which is to utilize a machinist vise. The next entry will cover how this is done.

For high tpi filing 12tpi and above,I prefer to use the Vallorbe Swiss 3 Square Needle Files in Cut #3, 180mm length. Shown as Ref:10-307-000 on the following attachment. IMO they are best quality you can buy based upon the overall quality and endurance of the cutting edge.

http://jewellerssupplies.com.au/images/pdfs/P96_101.pdf

To achieve optimum performance on a high tpi backsaw its preferable to reduce the tooth set so it just clears the saw plate on each side to prevent binding within the sawn kerf.

There are options available such as stoning the set, but my personal preference is to use a high precision machinist vise. In order for this method to work effectively you need to use a packing agent each side of the saw plate so as not to compress the set completely. My method using a single layer of masking tape to each side of the plate, positioned inside a 1/4" below the tooth line.

The size of the jaws on the vise in not critical as long as they have a smooth internal face. For those vises that don't installing a flat surface packer to each jaw would remedy this. Such as steel or brass plate. What is critical is that the vise be of high precision that allows the jaws to mate correctly when fully clamped.

As you will see the process is not overly complicated. Start at one end of the tooth line, close the jaws tightly, and move the saw plate further along and repeat the same step until the entire toothline has been completed.





After the fine tuning of the set has been done, its time to do some test cuts with the saw.



End grain. (The teeth are following a straight line so the set is even on both sides).

Job completed. Time to move on.



Stewie;

 

[swagman]

There's been a bit of discussion on woodwork forums in the past on the shelf life of shellac once its mixed with spirit. I marked the date on the top lid of the jar I mixed the brew. 12/7/2012. Nearly 20 months ago. Its still good to use. The shellac was Tiger Flakes Shellac purchased back then from TFW. http://www.toolsforworkingwood.com/s.../item/MS-TF.XX

What I put the extended use down to storing the shellac in a sealed jar away from direct sunlight and variable temperature changes in the workshop inside an old refrigerator that doesn't have the power turned on.

Stewie;

 

[swagman]

I use a 1/4" wide artist brush to coat the whole handle through the 150 & 220 grit phases. After 220 grit I use a small rolled up piece of makeup wipe as the applicator for the shellac. They resemble a normal tissue paper but are slightly moist when fresh. I maybe wrong but it smells like their moistened with baby oil. Anyway, I generally keep these stored so that they naturally dry out before I need to use them. I think from memory it was Klaus that supplied the tip on using these. The key is to cut a inch to inch 1/2 long strip. Roll it up so it forms a soak pad, dip it into the jar of shellac, and squeeze out any excess with your fingers before rubbing onto the wood surface. That way you can apply an even coating without the concern of heavy build up areas on the handle surface. Unlike the 150 grit sanding where I applied 2 coats of shellac during sanding, 220 and above receive just the 1 coat, then sand, then coat again before moving onto the next finer grit.

Here's a photo of the wipes I use.



Stewie;