Butt pad grinding is a necessary evil in this trade.
Someone at some point is going to ask me to change the length of pull of their shotgun/rifle and fit a new butt pad. Last week was typical of this with three shotguns requiring new pads with one to be balanced at the same time.
The owners were looking to reduce felt recoil so we agreed on KICK-EEZ pads which are manufactured from Sorbothane and really do have a dramatic impact on recoil, the downside is it is like grinding chewing gum and is one of the filthiest jobs I can think of, well other than actual polishing.
I had not planned on writing about this job so I have missed a few images however it was when I saw the state of the grinder that I felt it was worth a picture or two.
First job is determine exactly where the stock should be cut, I wrap the wood in masking tape on the underside and cut area to protect it and measure and mark multiple times.
Then off to the band saw, I use a Startrite vertical machine with a 1/4″ bi-metallic blade. This is one machine that I always keep a blade guard on and it is worth taking a lot of care when setting up as not only can you mess the stock up, you can also very easily remove the odd finger or two.
The key points here are keep the stock horizontal and I add shims taped to the underside in the wrist area to ensure this is correct and secondly use a guide which is adjusted and locked in place for each job. The cut takes only a few seconds and gives a remarkably fine finish, however I can finish on the 300mm bench sander as needed.
Time to attach and mark the pad, probably the most awkward part is marking the vertical centre line and I check this a couple of times before marking with a sharp wax pencil, once done I can locate the pad in place and mark the top hole with a correctly sized transfer punch. I always drill a pilot hole for the screw, and once in place I can mark and drill for the bottom screw and securely fit the pad.
At this point I need to mark the material to be ground away. In the past I would scribe and chalk the line in however this leaves a line that is hard to see and the scribe can ride up and mark the wood so I use a white wax pencil which gives a clear line to work with and cannot damage anything.
Next job is fit the butt pad, I use a fixture that is attached to the bench grinder and replicates the angle of the butt from the wrist area. With the pad in place I start grinding, this is a truly filthy job, especially if you have a 2-3 pads to grind in one go and I end up covered in rubber as does that part of the workshop regardless of extraction. If you are wondering, I use 150 grit Aluminium Oxide, it is a bit slower than say an 80 grit however it is a lot harder to take too much material off and gives a finish that needs a lot less finishing.
I test the fit and grind further as required and finish with foam sanding blocks, this gives a smooth finish with any previous grinding marks removed.
Finally, I oil the freshly cut section of the butt, grab a coffee and then fit the pad securely. I usually give the sides of the pad a light coat of a beeswax polish I make for my own use and it leaves the ground sides looking good.
One concern here is fit of butt pad to butt and I aim to have no step in the transition between the two. If you wish to do this job yourself I recommend aiming for the same or with the pad being very slightly larger than the pad so you can always finish it with a sanding block and in the absence of a sanding block use some 220 grit Aluminium Oxide paper wrapped around a piece of wood.
As well as producing a lot of rubber/Sorbothane dust the disk itself clogs up badly and I use a dressing block to remove this build up. It is a piece of natural coloured rubbery material, I have no idea what it is however it works superbly and restores the disk to as new in a couple of seconds. You can see the pad sitting on the top of the grinder table. Before you shout, yes the gap between table and disk is wider than it should be and this is deliberate and allows the ground away material to be sucked down into the extraction port.
Final job on a Browning 325 was to balance to the pin and this required an additional 118 grams of weight in the butt stock. Sorbothane is not as dense as hard wood and the customer had added extended chokes to a gun that was already balanced quite a bit forward hence the weight required.
I typical need to add anything from 105-120 grams to bring the gun back to the pin with material added or removed if the balance needs to be moved back or forth.
So that was the middle bit of grinding and fitting a butt pad, I will take some pictures when I remember so you can see the marking, cutting and final job.