Kapex Hold down clamp

[Martin S]

"Santa" brought me a Kapex....I was using it a lot this weekend to cut 2x4 blocking and was thinking it would be nice to have a "Hold down clamp"  on both sides, however I do not see it in the assessory section of the website.  I presume I am just not seeing it?

Martin

PS. it is an engineering marvel...

 

[peter halle]

Martin,

Congrats on your Kapex.  I didn't see it on the website either, but in the print catalog the part number is 494391 and the cost is 65.00 USD.  I will caution you that you probably should not use two clamps at the same time.  Increases the risk of pinching the work and the blade.

Peter

 

[Martin S]

Thanks Peter.  Good point...Had not thought of that...bad idea. 

Martin

 

[Neill]

Martin,

Peter is correct.  I actually read somewhere that you should not use two clamps.  In the event you want to do it anyhow, the part number would be the same since the clamp is interchangeable from either side.

Neill

 

[mwhafner]

It is handy to have clamps on both sides, especially when you are making straight cuts, or slightly angled cuts.  Just, as Peter pointed out, don't use both of them at the same time. 

 

[chrisrosenb]

I have 2 clamps, but only use one at a time.
I did not like switching  the one clamp from side to side.

Chris

 

[Rick Christopherson]

I will caution you that you probably should not use two clamps at the same time.  Increases the risk of pinching the work and the blade.

No, this is not correct. Clamping on both sides will not cause a blade pinch.

I think this belief might have originated from the notion of not using a stop block on the side you are not holding or clamping, which will result in a binding problem. If the workpiece and offcut are both constrained, they can't move after the cut, and therefore, cannot result in a pinched blade.

 

[tbellemare]

Rick:

I have the highest respect for your observations and opinions and in this case, I have to ask you a question - it relates to the "if" and "except" when related to what you just posted...

What "if" the work piece is dangling on the off cut side (or either side). The two clamps can cause the part of the work piece around the near future kerf to be planer to the saw table because there are two points holding the work piece down. After the cut, there is only one point holding the dangling off cut (or work piece) to the table and it is closer to the fulcrum. The result can be, Pinch!

"Except" I know the proper way to do the cut is to have both sides supported outboard as necessary, and I think that is probably what you meant, but I have seen just what I described above and it can grab.

Tom

 

[Rick Christopherson]

Rick:

I have the highest respect for your observations and opinions and in this case, I have to ask you a question - it relates to the "if" and "except" when related to what you just posted...

Come on....say it like a man....you doubt what I say!!!  It's not like you are the first...and you certainly won't be the last.[poke]

What "if" the work piece is dangling on the off cut side (or either side). The two clamps can cause the part of the work piece around the near future kerf to be planer to the saw table because there are two points holding the work piece down. After the cut, there is only one point holding the dangling off cut (or work piece) to the table and it is closer to the fulcrum. The result can be, Pinch!

Yes, the closer the clamping point is to the fulcrum point, the easier it will be for the workpiece to tilt, and this is irrespective of whether the operator is holding the workpiece, or a clamp is holding the workpiece. However, because the fulcrum point is outside of the blade kerf, any tilting will result in the workpiece moving away from the blade, not towards it. The cosine of any angle greater than zero is smaller than the cosine of zero, so the more the workpiece tilts, the farther away from the blade it becomes as it tilts. It is the antithesis of a binding condition. Moreover, that same condition or scenario would still exist, and be even worse, if the operator was attempting to control this assumed cantilevered offcut instead of a clamping device controlling the offcut.

The only time where a clamped workpiece/offcut combination might result in a binding condition is when the piece being cut is crowned in the center and not resting on the mitersaw table before the cut is made. After the cut is made, it will be resting on the table, and the comment I made above about cosines becomes the reverse condition, and binding will occur. (i.e. the angle went from larger to smaller, so the workpiece moves closer to the blade). However, this condition will still occur to some degree regardless whether either piece is clamped or not, and is the specific situation I had in mind when I cautioned users to not cut warped material in the Kapex manual. Any time you cut material that is crowned, it will bind on the blade, regardless whether it is clamped or hand-held. Clamping will actually minimize this, because the clamping force will tend to straighten the crown before the cut is made.

If a binding condition occurs, it is not the result of clamping, but the result of a crown in the uncut workpiece. Crowned workpieces should be handled with care regardless whether they are clamped or not.

 

[greg mann]

The only time where a clamped workpiece/offcut combination might result in a binding condition is when the piece being cut is crowned in the center and not resting on the mitersaw table before the cut is made. After the cut is made, it will be resting on the table, and the comment I made above about cosines becomes the reverse condition, and binding will occur. (i.e. the angle went from larger to smaller, so the workpiece moves closer to the blade). However, this condition will still occur to some degree regardless whether either piece is clamped or not, and is the specific situation I had in mind when I cautioned users to not cut warped material in the Kapex manual. Any time you cut material that is crowned, it will bind on the blade, regardless whether it is clamped or hand-held. Clamping will actually minimize this, because the clamping force will tend to straighten the crown before the cut is made.

If a binding condition occurs, it is not the result of clamping, but the result of a crown in the uncut workpiece. Crowned workpieces should be handled with care regardless whether they are clamped or not.

I was going to comment on this condition and had actually started to type out my thoughts, and then figured someone would question you about it. I agree with you completely on this one, Rick. In fact, I think one can easily make the case that a warped board which does not make contact with the fence on either side of the cut is the optimum time to use 2 clamps, and also apply a bit more pressure than normal, while easing through the end of the cut. This is the point at which an unclamped workpiece will collapse back to the fence and surely bind. Of course it may not stall the blade or even result in kickback but it will certainly spoil the cut surface. How many of us have done just this and then taken a second light pass on the newly severed board now fully positioned against the fence on the keeper side, just to restore the end cut? I'll bet all of us have. The point is that the 2 clamps mitigate the forces that would move the board towards the fence just as it becomes 2 boards. Two clamps on each side would be even better but probably overkill. (Sorry guys, it's my metal machining background getting the better of me.) That would keep the board from pivoting under the clamp. This isn't rocket science but it certainly is something to be on the lookout for, especially when cutting up rough stock before it has seen the jointer, or the plunge saw and rail, to get a straight edge.