Bow blocks

[Barry J. Griffiths]

I've seen frog and tip blocks both with flat bottoms and hollowed bottoms. I've done rehairs with both types. I was just wondering what some board members might consider the pros and cons of each method.

Barry

[Oded Kishony]

I put a small hollow with a #11 gouge. I think it leaves a bit more space for the hair and more contact area for the plug.

Oded

[Brad Dorsey]

I've seen frog and tip blocks both with flat bottoms and hollowed bottoms. I've done rehairs with both types. I was just wondering what some board members might consider the pros and cons of each method.

Barry

I think that hollowed bottoms look more elegant, and they are an indication that the person making them put in a little extra effort. However, I don't think that they offer any functional advantage, and I have never bothered to hollow the bottoms of my plugs.

[danielmiller]

The advantage to putting in a groove on the underside of the plug is that it helps to keep the knot in the center of the mortice and it gives the sides of the plug a little more depth to fit against the walls of the mortice for a more secure fit. However, this is not necessary for a good re-hair. It all depends on how you tie the knot and fit it into the mortice.

[Craig Tucker]

I've seen frog and tip blocks both with flat bottoms and hollowed bottoms. I've done rehairs with both types. I was just wondering what some board members might consider the pros and cons of each method.

Barry

Hollow - for sure.

The extra room is not strictly necessary on all blocks, but I think it is required on a great many of them, and I always put it in, and adjust the bolck thickness to accomodate the knot with the hollow.

[Brad Dorsey]

The advantage to putting in a groove on the underside of the plug is that it helps to keep the knot in the center of the mortice...

As I see it, the groove is unnecessary to keep the knot centered in the mortise, because if the plug is otherwise correctly shaped, the knot will automatically be centered. The critical factor in this respect is the gap left for the hair to pass through between the end of the plug and the end of the mortise. If this gap has an equal width all the way across, and if it is just wide enough for the hair to pass through and no wider, then the knot cannot be anywhere else but in the center.

[Craig Tucker]

As I see it, the groove is unnecessary to keep the knot centered in the mortise, because if the plug is otherwise correctly shaped, the knot will automatically be centered. The critical factor in this respect is the gap left for the hair to pass through between the end of the plug and the end of the mortise. If this gap has an equal width all the way across, and if it is just wide enough for the hair to pass through and no wider, then the knot cannot be anywhere else but in the center.

I agree with this completely - this is one of the critical factors for a good rehair.

On the other hand, from my perspective, depending on the bow, though the hollow on the plug may not be directly connected with those specific requirements mentioned above, if the knot is tight or too tight in the mortice - then a hollow on the wedge, as an entirely seperate factor, may have a necessity of its own - allowing the knot to fit comfortably, and for the plug to have more contact surface area.

In particular with the tip mortice - which is often tight.

Then too, in my opinion - there are plenty of instances where this distinction becomes more a matter of personal choice - than a question of which way is more or less correct.

[Brad Dorsey]

...if the knot is tight or too tight in the mortice - then a hollow on the wedge, as an entirely seperate factor, may have a necessity of its own - allowing the knot to fit comfortably...In particular with the tip mortice - which is often tight...

I saturate my knots with super glue then squeeze them flat with pliers, so they require less "headroom" in the mortises than they would if I left them round. Flattening the knots also makes them tighter.

I almost always find adequate space in head mortises for my plugs and hair knots. However, I often find that the frog mortises of cheap bows are too short and too shallow, so I cut them longer and deeper.

[Barry J. Griffiths]

I saturate my knots with super glue then squeeze them flat with pliers, so they require less "headroom" in the mortises than they would if I left them round. Flattening the knots also makes them tighter.

I do the same, usually with a hollowed block. I find that flattening the knot also keeps the bundle from rolling off axis, causing a twist in the hair.

Barry

[Mat Roop]

I saturate my knots with super glue then squeeze them flat with pliers, so they require less "headroom" in the mortises than they would if I left them round. Flattening the knots also makes them tighter.

I almost always find adequate space in head mortises for my plugs and hair knots. However, I often find that the frog mortises of cheap bows are too short and too shallow, so I cut them longer and deeper.

Brad...

1-Superglue sets instantly... so if you compress the knot after saturating, are you knot breaking the glue set and loosening the knot before the customer even gets the bow?

2- I've tried saturating the knot with superglue but find that it wicks past the knot into the hair making bending into the mortise difficult... how do you deal with that?

Cheers!... Mat

[Brad Dorsey]

...1-Superglue sets instantly... so if you compress the knot after saturating, are you knot breaking the glue set and loosening the knot before the customer even gets the bow?...

Knot quite instantly. I figure I have a few seconds to squeeze the knot before the glue sets.

...I've tried saturating the knot with superglue but find that it wicks past the knot into the hair making bending into the mortise difficult... how do you deal with that?...

As I squeeze the knot I bend the hair at a right angle around the jaw of the pliers. So if I put on enough glue to wick past the knot, the glue fixes a right angle bend in the hair just beyond the knot when it sets.