I have a few further thoughts. Some of them might be a bit confused as this idea has evolved on 3 separate threads.
You mentioned having a 24mm head which might now be reduced in diameter to match Qwas Dogs. On The Qwas webpage he says " The small shoulders assures the dogs are aligned with the hole rather than inaccuracies in the table surface from glue, saw kerfs, or water spillage" It would seem to be a good point though one of the rail dog designs I came up with had a 28mm diameter intending to reference the table top for extra stability. I still don't have the time or funds to try it out.
I rambled on about it here
I think a bigger diameter dog that also uses the table top for stability could be an advantage. It might mean checking the table for defects by running your hand over it before using a hole. Any defects could quickly be remedied with a light sanding. You could also put a thread in the bottom of the dog and have a bolt and washer which could be inserted easily from underneath to really lock the dog into position. This probably wouldn't be necessary when cutting most sheet materials but would give a lot of extra stability on thicker stock where any lateral forces exerted by the guide rail on the dog could cause greater inaccuracies. The ability to simply and easily lock the dog could also overcome what I perceive to be a flaw in your design. The hole size of your target market is out of your control and you will have to contend with 2 generations of MFTs and home produced 20mm tops. Qwas has a solution for the larger holes on the MFT3 by pulling the dogs closer together. You can't do that with your solution and if you machined a dog that perfectly matches the MFT3 you will possibly be excluding people with older MFTs users or shop produced solutions. Securing the dogs from underneath would be a minor inconvenience when compared to the added accuracy, wider compatibility etc. You could also clear most of your workbench very quickly by removing only the front dog which is easily accessible.
I also keep thinking about the marriage of two dissimilar metals with the steel pin and aluminium body. It's been years since my engineering training but some minor alarm bells are going off in the back of my mind. Others might be able to expand on this? Will there be any corrosion issues 6-12 months from now?
I'm still not convinced by the two component design though I know you have mentioned that it will keep production costs down. Can you not have a piece of 1 inch aluminium machined down to whatever diameter you decide upon that projects above the table top by whatever height necessary. I don't understand the need for different height pins as I can't see how a pin that projected even up to 100mm would affect the functionality or get in the way of the saw. It would be a simple component and a dedicated rail dog. Any possible additional cost would be offset by not having to bore holes in all the rest of the dogs.
The other thing that would concern me is the tolerance required to get a good seat between the pin and the bored hole. Even if they were made of the same material there could be issues when you consider that these will be stored in the back of people's trucks. The temperature range they will have to work in will therefore be something like -15 to 45 degrees C. The two components will expand or contract at different rates across a 60 degree temperature range. There's no point having the accuracy of a CNC lathe if this simple fact shoots you in the foot. This could actually be made worse or possibly better by having two different materials. I can't imagine users being impressed if the pins get stuck in the holes.
I think your overall concept is brilliant and it solves a lot of what I perceive to be issues with the Qwas rail dogs. The part of your design that attaches to the guide rail is superb, I just think you have over designed the rail dog element. I feel that the perceived benefits in functionality and cost you have mentioned could easily be outweighed by the potential problems I have mentioned above. The only way to know for sure is field testing and I am happy to sit back and watch others do that.
Hopefully someone on here can shed some more light on this as my understanding of metallurgy and engineering is a little rusty!
I also still think that you have a marvelous opportunity to include extra functionality in the clamps that attach to the guide rail. There must be a way of including simple and cheap functionality that facilitates the easy attachment of an off the shelf parallel guide solution. I know that you have said that this will affect cost and possibly over complicate things at this stage of development but it is obvious that you are striving to achieve excellence in your solution. It would be the dream ticket for me and many other users if you could improve on the shortcomings of the MFT, Qwas Dogs and the parallel guides with one simple component. Cost would hardly be an issue if you can provide pefect cross cutting and rip cutting. The way I see it is that anyone who wants to do perfect cross cuts also wants to do perfect rip cuts and will happily pay for the privilege. There must be a ready made fence that could attach really easily.
That is another reason why I think matching the diameter of the Qwas Dogs could be a real red herring as your solution once it has fully evolved will blow all the others away. Dogs of different diameters could still mix and match perfectly well for a lot of their use provided they are used in a different planes.
Good luck and keep up the excellent work. You are so close to a truly amazing solution.
You mentioned having a 24mm head which might now be reduced in diameter to match Qwas Dogs. On The Qwas webpage he says " The small shoulders assures the dogs are aligned with the hole rather than inaccuracies in the table surface from glue, saw kerfs, or water spillage" It would seem to be a good point though one of the rail dog designs I came up with had a 28mm diameter intending to reference the table top for extra stability. I still don't have the time or funds to try it out.
I rambled on about it here
I think a bigger diameter dog that also uses the table top for stability could be an advantage. It might mean checking the table for defects by running your hand over it before using a hole. Any defects could quickly be remedied with a light sanding. You could also put a thread in the bottom of the dog and have a bolt and washer which could be inserted easily from underneath to really lock the dog into position. This probably wouldn't be necessary when cutting most sheet materials but would give a lot of extra stability on thicker stock where any lateral forces exerted by the guide rail on the dog could cause greater inaccuracies. The ability to simply and easily lock the dog could also overcome what I perceive to be a flaw in your design. The hole size of your target market is out of your control and you will have to contend with 2 generations of MFTs and home produced 20mm tops. Qwas has a solution for the larger holes on the MFT3 by pulling the dogs closer together. You can't do that with your solution and if you machined a dog that perfectly matches the MFT3 you will possibly be excluding people with older MFTs users or shop produced solutions. Securing the dogs from underneath would be a minor inconvenience when compared to the added accuracy, wider compatibility etc. You could also clear most of your workbench very quickly by removing only the front dog which is easily accessible.
I also keep thinking about the marriage of two dissimilar metals with the steel pin and aluminium body. It's been years since my engineering training but some minor alarm bells are going off in the back of my mind. Others might be able to expand on this? Will there be any corrosion issues 6-12 months from now?
I'm still not convinced by the two component design though I know you have mentioned that it will keep production costs down. Can you not have a piece of 1 inch aluminium machined down to whatever diameter you decide upon that projects above the table top by whatever height necessary. I don't understand the need for different height pins as I can't see how a pin that projected even up to 100mm would affect the functionality or get in the way of the saw. It would be a simple component and a dedicated rail dog. Any possible additional cost would be offset by not having to bore holes in all the rest of the dogs.
The other thing that would concern me is the tolerance required to get a good seat between the pin and the bored hole. Even if they were made of the same material there could be issues when you consider that these will be stored in the back of people's trucks. The temperature range they will have to work in will therefore be something like -15 to 45 degrees C. The two components will expand or contract at different rates across a 60 degree temperature range. There's no point having the accuracy of a CNC lathe if this simple fact shoots you in the foot. This could actually be made worse or possibly better by having two different materials. I can't imagine users being impressed if the pins get stuck in the holes.
I think your overall concept is brilliant and it solves a lot of what I perceive to be issues with the Qwas rail dogs. The part of your design that attaches to the guide rail is superb, I just think you have over designed the rail dog element. I feel that the perceived benefits in functionality and cost you have mentioned could easily be outweighed by the potential problems I have mentioned above. The only way to know for sure is field testing and I am happy to sit back and watch others do that.
Hopefully someone on here can shed some more light on this as my understanding of metallurgy and engineering is a little rusty!
I also still think that you have a marvelous opportunity to include extra functionality in the clamps that attach to the guide rail. There must be a way of including simple and cheap functionality that facilitates the easy attachment of an off the shelf parallel guide solution. I know that you have said that this will affect cost and possibly over complicate things at this stage of development but it is obvious that you are striving to achieve excellence in your solution. It would be the dream ticket for me and many other users if you could improve on the shortcomings of the MFT, Qwas Dogs and the parallel guides with one simple component. Cost would hardly be an issue if you can provide pefect cross cutting and rip cutting. The way I see it is that anyone who wants to do perfect cross cuts also wants to do perfect rip cuts and will happily pay for the privilege. There must be a ready made fence that could attach really easily.
That is another reason why I think matching the diameter of the Qwas Dogs could be a real red herring as your solution once it has fully evolved will blow all the others away. Dogs of different diameters could still mix and match perfectly well for a lot of their use provided they are used in a different planes.
Good luck and keep up the excellent work. You are so close to a truly amazing solution.
