The manufacturers of the Flat Lying Trammel Set (which was reviewed in A WW # 149) have released a Profile Scriber. As with its other products, M-Power seeks to develop handtools that make common tasks easier.
When mating a board to an uneven surface, the standard method is to draw a line on the board parallel to the other component. This can be done with a compass or with a pencil stuck in a homemade guide.
The problem with both these tools is that it takes a lot of care to keep the tool exactly at right angles to the irregular profile while drawing the line. Any significant inaccuracy will result in a gap in the finished joint or a ‘bump’ that will prevent the two sides of the joint mating.
Design M-Power’s solution is a spring-loaded pencil in a round insert.
The insert fits into one of four discs, giving an offset (radius) of 14.Smm, 2Smm, 3Smm or 4Smm respectively.
For a smaller offset, the pencil can be reversed in its holder – the metal cap screws off, releasing the pencil and the spring. This provides an offset of 8.7Smm. However, the cap does not have a rolling action, unlike the guide which is fitted with a ball bearing for smooth operation.
What happens when the pencil gets shorter? There appears to be a fair amount of travel in the spring. However, if you like to use most of the pencil, you may have to insert a piece of dowel as a spacer.
Operation For simpler marking out tasks, the Profile Scriber is very easy to use.
Choose the offset you require or prefer. In most cases the smaller wheels work better but if for any reason you can’t get the workpiece close enough to the mating surface, you do have the option of the larger wheels.
You can also make your own wheels with a hole saw, bandsaw or on the lathe. The main criterion is that the wheel must be perfectly round to give an accurate marking. The manufacturer’s web site gives the centre hole as 0.92S” dia. which we expect is a very difficult drill size to source. However the Metric equivalent is 23.5mm which should be a bit easier to purchase.
With the wheel fitted, position the Scriber on the board. I held the barrel close to the wheel (base) to avoid accidentally tipping the tool as I ran it along the profile being copied. Not only was the process very easy but the marking is completely repeatable. Mark out the profile a dozen times and each marking will be exactly the same, due to the constant radius of the wheel.
Accuracy
It might be called the Perfect Butt, but the geometry of the Profile Scriber is not perfect. The Scriber marks a line parallel to the immediate face of the profile. However what is actually required is a line parallel with the joint. Along the sides of the recess, the line is equidistant to the sides whereas it should be flush.
Initially I thought that the Scriber would be quite sensitive to curves in the joint, but that this is not the case. Where the radius of the curve is smaller (ie. there is greater curvature), a smaller wheel is more accurate. However even the larger wheels will provide a good join.
There’s also the question of how much accuracy is actually required. Being precise to 0.1 mm is of no great use if you can’t cut the material to that accuracy.
From my observations and using the Scriber on-site, the tool is ideal for marking any out-of-alignment in built-in work.
Complex joints Method Two
Where there is a major change in the line of the joint, the Perfect Butt Profile Scriber can still be used, but a two-step process is required. This process is outlined in the instruction leaflet that accompanies the tool.
The idea is to create a template with the Profile Scriber. Then, using the template and the Profile Scriber with the same wheel attachment, a line is marked on the board. Most of the errors introduced by the Scriber in the first step are removed in the second.
About the only problem left is inside corners. I formed them by extending the sides until they met at a corner.
This method, while being more tedious because a temp late has to be drawn and cut, does have the advantage of producing very accurate joints when the profile is very irregular.
While the Scriber will mark out both simple and complex outlines, it is not suited to profiles where there are small narrow changes. Even the smallest wheel will tend to produce smooth flowing lines rather than pick up any small gouges in the mating surface.
Other Uses
With a little thought the Perfect Butt can be applied to other tasks. For example, if you are laying up a component in laminations, you can make full size templates using the Scriber to mark the offset formed by each layer of wood.
The Tool
Manufactured in England, the Perfect Butt Profile Scriber is made from solid brass, as is the smallest wheel. The three larger wheels are made from a durable plastic.
It’s a well-engineered, well-manufactured marking tool designed to provide repeatable accurate markings.
The Scriber can’t be applied in all situations but it will work on most joints and make the job much faster and easier.
