Machining large stock for pergola Knee brace.

[johnnyb]

a quick check shows your right. sorry! Read my tops as bottoms and vice versa. it makes sense in my twisted world.

 

[Markvk]

Ah, johnny, now I think I see why I misunderstood you. You seem to have reversed the terminology I'm used to for bearing guided router bits.

The description 'top bearing bit' is normally given to bits where the bearing is nearest the cutter's shank, the part that goes into the collet, commonly described as something like a top bearing flush trim bit.
And the descriptor 'bottom bearing bit' generally applies to a bit with a bearing at the exposed end of the cutter, i.e., furthest from the collet, and commonly described as a bottom bearing flush trim bit.

I apologise if I've got your meaning wrong. Maybe I'm just being dense. Slainte.

You live and learn... i thought it was the other way round but the way you describe it makes much more sense! either way i need one of each!

 

[Markvk]

If it's a one-off, I agree a bandsaw and a bit of chiselling and sanding (bobbin sander or not) would suffice. But if there are several I'd go with a router, as I described earlier. But I do have a lot of router experience and know how to set up for safe operation, in both hand-held and inverted in a table mode. A 75 mm long cutter used at its maximum length is not one to mess around with in either set up if you're at all unsure of what you're doing. I've no idea how experienced and confident Markvk is with router set up and use. Approach this routing task (if you decide to go with it) with great care Mark if you're not very experienced around routers. Slainte.

Thanks Sgian.

i am well aware of the dangers involved with having 75mm of high speed finger removing equipment sticking out of a table, I am going to buy a bobbin sander to try it but i think given the fact that i have 32 to make i will end up using the router table.

Whilst my experience with routing is not exactly broad, its not to bad either. As far as i can see if i seat the cutter properly in the collet and select the correct speed for the cutter, theres not much else to do setup wise? I cant see any way of using cutter guards.

As long as i take my time and dont try to take too much material in one go and keep my fingers well away hopefully all will be well....

Ill have the air ambulance on speed dial....

 

[Sgian Dubh]

i am well aware of the dangers involved with having 75mm of high speed finger removing equipment sticking out of a table, I am going to buy a bobbin sander to try it but i think given the fact that i have 32 to make i will end up using the router table.
As long as i take my time and dont try to take too much material in one go and keep my fingers well away hopefully all will be well....

I assume you've watched the video, the link to which you posted. I noticed in that something that concerns me; it's the fact that the template used doesn't have a lead-in or lead-out portion, it's the exact required profile and no more. He has to engage the bearing of the cutter by plunging into the wood he's cutting until the bearing meets the template, which increases the likelihood of kickback when used in both an inverted table mounted router configuration and in hand held router use.

What would have made it better (safer) in my experience would have been to extend the template profile beyond or away from the required profile so that the bearing can be engaged with the template before the cutter engages the wood. So, for example, if you have a required arc in the wood you're shaping that is, let's say, an arc length of 300 mm with a radius of 400 mm, you make the template with the same 400 mm radius, but make the arced portion something like 350 or 400 mm long: this extra length allows you to engage the bearing before the cutter engages the wood. There are other ways of creating a lead-in or lead-out for profiles, such as a run out portion of the template that deviates away after the required part of the profile, but that's just one example. Slainte.

 

[Markvk]

I assume you've watched the video, the link to which you posted. I noticed in that something that concerns me; it's the fact that the template used doesn't have a lead-in or lead-out portion, it's the exact required profile and no more. He has to engage the bearing of the cutter by plunging into the wood he's cutting until the bearing meets the template, which increases the likelihood of kickback when used in both an inverted table mounted router configuration and in hand held router use.

What would have made it better (safer) in my experience would have been to extend the template profile beyond or away from the required profile so that the bearing can be engaged with the template before the cutter engages the wood. So, for example, if you have a required arc in the wood you're shaping that is, let's say, an arc length of 300 mm with a radius of 400 mm, you make the template with the same 400 mm radius, but make the arced portion something like 350 or 400 mm long: this extra length allows you to engage the bearing before the cutter engages the wood. There are other ways of creating a lead-in or lead-out for profiles, such as a run out portion of the template that deviates away after the required part of the profile, but that's just one example. Slainte.

Perfect, thanks. This is exactly the kind of advice that i am after. Given the amount of copies that i need to make its bordering on obvious that I need to go down the router route. If that this is the process need to follow I'm grateful for any ideas that minimise finger loss..

My bobbin sander arrives on Wednesday, and i will play with it, ill order the cutters on Tuesday after speaking to wealden once i decide the best way forward ill post pics of my process and hope that you guys will help me through it.