Saw Kerf with respect to the insert centerline

[edflorence]

Where it comes to rest is seldom an issue. At least not one of importance.

I would like to be able to mark a cut line, on the table insert, that could be used for placement of material being cut. In fact, I have often thought about some way to scribe a line on the main table.

If it does nothing else, it extends the life of the ZCI.

It has never seemed to be much trouble to use the quill feed as necessary and even to move headstock or table or some combination of all to get the blade centered in a pre-cut zci. In fact, this has to be done when shifting from a zci cut for vertical cuts to one cut for an angled cut with a tilted blade. So I agree with Dusty having the blade "automatically' centered under the zci is seldom if ever an issue.

However, there are times when it is nice to have a gage line on the table. What I have done in the past is to lay masking tape on the infeed side of the saw blade and then use a straightedge against both sides of the saw blade to extend lines out on to the tape. The two parallel lines then show exactly where the cut will occur. This is very handy for multiple cuts, but obviously is only good for one setting of the blade.

[dusty]

My second Mark V is not equipped with the rubber bumper (I placed a parts order today that includes rubber bumpers) but if I manually set the carriage and headstock separation the blade is a lot closer to the center line.

I don't know what to make of that but I found it interesting.

Bottom line - there will come a day in the very near future when they are nearly the same and centered within the insert. Why? Because I think that was the original intention.

If you look at the pictures in PTWFE, the saw kerfs all appear to be right on the center line.

[algale]

My second Mark V is not equipped with the rubber bumper (I placed a parts ordered today that includes rubber bumpers) but if I manually sent the carriage and headstock separation the blade is a lot closer to the centerline.

I don't know what to make of that but I found it interesting.

Bottom line - there will come a day in the very near future when they are nearly the same and centered within the insert. Why? Because I think that was the original intention.

\If you look at the pictures in PTWFE, the saw kerfs all appear to be right on the center line.

This is going to be fun to watch!!!

[JPG]

This is going to be fun to watch!!!

Yes I think so!


I also think you may be hailed as a prophet!;)









Hmmmmmm. ((1/2" - 3/8") / 2) = 2/32!:D Wonder where the other 1/32 came from? Front holes?


Regardless, firm stop rings(IMHO) are a 'solution'(or at least as close as all the other varying tolerances will allow).

Wonder if Dusty has an extra thick rubber washer on the quill behind the quill stop ring? Sorry Dusty, that just now occurred to me! Must have been the unconscious suggestion of 'other' things varying.

[reible]

Hi,

As I mentioned before I have looked at portions of this several times over the years. I don't feel like attempting to find previous posts so I'll go from memory here. If anyone does find the old posts go by the numbers there as these might be off a bit.

One subject was repeatability. If say one were to rip a board then raise the table and slide the headstock down to the other end, carriage/table to the other side. Without moving the fence or adjusting the blade position how close do you get when you "mate" them again without any special help? What I found on my 520 was about .006" on average.

I think this is repeatable by other with a 520 if you care to try. Procedure is to use the dial indicator clamped to the table and adjusted to measure the position of a tooth on the blade. Record the dimension do the separation and then return to the tooth and record again.

On some of my machine pictures you will see a wood piece clamped across the tubes. That would either be my lamp holder or my test fixture. The test fixture was equipped to fix the distance between between the headstock and the carriage by way of a threaded bolts that would locate to fixed points on each side and was slightly larger then the normal operation of the rubber bumper. This information I have never published as I was never happy with the results. The goal was .000" the best I got was more in the .003-.004 range.

So why was that? This turned out to be a table stability issue. I have posted about this before too. Sitting on just the stock two tubes you can generate movement. Going to a 4-tube set up is a lot more stable. At this point I revisited my first data and when I disturbed the table on two posts things got worse. (I believe at some point in time after this Nick did a show on this.)

It was clear that more needed to be looked at.

My next trick was to build a runner for the miter slot, a block of wood to attach the runner that would come close to the blade edge. Added a nylon bolt so I could tweak the distance from the blade to the miter slot to use as a measurement. Since different blades give different distances it has to be variable, hence the lack of a more simple cut-off method. This is not without problems. The headstock when tighten moves, as does the carriage, so as you attempt to have the tooth and the bolt head just touch things move as you work. End result is again close but that is all.

I wish I could have found a magic solution but for now I can get with in a couple of thousand.

While these efforts were to a different end they do relate to problems you will have with centering a cut in a ZCI.

Now here is another post I don't feel like trying to find so I try and cover it here. I like to have a mark were the edge of the blade cuts as a reference. This can be done with magic transparent tape. I'll post a couple of photos to give you the idea from here at my computer, too cold to work in the shop now (39.6 degrees).

You simply stick the tape on the insert, then run a scrap of wood (say 3/4 x 3/4 by 12" through the blade, keep holding the stock against the miter gauge and don't let it move. Now slide it back to where the tape is and mark. Move the miter gauge to the other side and do the same thing. Now you have both sides marked. Just remember to change tape and marks when you change blades... just another think I've been doing for more then 50 years now.

[ATTACH]16173[/ATTACH]

BTW you could add a special circle in your home made inserts that could be replaceable that you could score lines on as you go.

Ed

[algale]

[quote="JPG40504"]

I also think you may be hailed as a prophet!]

A prophet, eh? Sure hope it is profitable.

[dusty]

[quote="JPG40504"]Yes I think so!


I also think you may be hailed as a prophet!]

You guys do know how to issue a challenge. But that is OKAY.

BTW - remember the quill spacers made from credit cards? I thought about that but that increases my error. There are NO extraneous spacers.

[dusty]

Hi,

As I mentioned before I have looked at portions of this several times over the years. I don't feel like attempting to find previous posts so I'll go from memory here. If anyone does find the old posts go by the numbers there as these might be off a bit.

One subject was repeatability. If say one were to rip a board then raise the table and slide the headstock down to the other end, carriage/table to the other side. Without moving the fence or adjusting the blade position how close do you get when you "mate" them again without any special help? What I found on my 520 was about .006" on average.

I think this is repeatable by other with a 520 if you care to try. Procedure is to use the dial indicator clamped to the table and adjusted to measure the position of a tooth on the blade. Record the dimension do the separation and then return to the tooth and record again.

On some of my machine pictures you will see a wood piece clamped across the tubes. That would either be my lamp holder or my test fixture. The test fixture was equipped to fix the distance between between the headstock and the carriage by way of a threaded bolts that would locate to fixed points on each side and was slightly larger then the normal operation of the rubber bumper. This information I have never published as I was never happy with the results. The goal was .000" the best I got was more in the .003-.004 range.

So why was that? This turned out to be a table stability issue. I have posted about this before too. Sitting on just the stock two tubes you can generate movement. Going to a 4-tube set up is a lot more stable. At this point I revisited my first data and when I disturbed the table on two posts things got worse. (I believe at some point in time after this Nick did a show on this.)

It was clear that more needed to be looked at.

My next trick was to build a runner for the miter slot, a block of wood to attach the runner that would come close to the blade edge. Added a nylon bolt so I could tweak the distance from the blade to the miter slot to use as a measurement. Since different blades give different distances it has to be variable, hence the lack of a more simple cut-off method. This is not without problems. The headstock when tighten moves, as does the carriage, so as you attempt to have the tooth and the bolt head just touch things move as you work. End result is again close but that is all.

I wish I could have found a magic solution but for now I can get with in a couple of thousand.

While these efforts were to a different end they do relate to problems you will have with centering a cut in a ZCI.

Now here is another post I don't feel like trying to find so I try and cover it here. I like to have a mark were the edge of the blade cuts as a reference. This can be done with magic transparent tape. I'll post a couple of photos to give you the idea from here at my computer, too cold to work in the shop now (39.6 degrees).

You simply stick the tape on the insert, then run a scrap of wood (say 3/4 x 3/4 by 12" through the blade, keep holding the stock against the miter gauge and don't let it move. Now slide it back to where the tape is and mark. Move the miter gauge to the other side and do the same thing. Now you have both sides marked. Just remember to change tape and marks when you change blades... just another think I've been doing for more then 50 years now.

[ATTACH]16173[/ATTACH]

BTW you could add a special circle in your home made inserts that could be replaceable that you could score lines on as you go.

Ed

You mention 'table stability' , Ed. Table stability or the lack thereof coupled with the headstock stability are two issues that will never be resolved except by redesign. Those factors are inherent in the Mark V.

To rid oneself of those issues requires the incorporation of 'old iron' and the elimination of the 5 in1 concept. You can achieve that 000 tolerance factor with old iron but not with the Mark V.

I have previously stated that I have adapted a .005 standard for myself. With that standard - your test scenarios were all great successes. I believe you have demonstrated that quit well.

What got me started on this centerline issue is not a matter of thousandths. My centerline is off 3/16 of an inch. It is, however, quit repeatable ( to within .005").

[dusty]

The solution (at least the initial one) was just too simple. It is called a spacer. Actually it is a supplement to the rubber carriage spacer ring.

[ATTACH]16174[/ATTACH]
This picture shows the centerline, the original offset kerf and the kerf cut with the supplemental spacer installed.

[ATTACH]16175[/ATTACH]

[ATTACH]16176[/ATTACH]
This picture shows the solution in place along with the carriage spacer ring.

[ATTACH]16177[/ATTACH]
This will be "it" for a while. If this proves to work, I will build a "final solution".

UNLESS - the new carriage rings are wider.

I believe I will wait to cut the kerf in the new ZCIs that I built in conjunction with the ZCI sled project. I should probably also wait to recut the ZCI sled kerf.

[reible]

Hi,

Table stability was given a major upgrade with the addition of the front/rear rails and tubes. You now can have 4 or even 6 vertical tubes. To see this major improvement you need to add an extension table then a set of bars to connect the main table and extension. BINGO major improvement.

Keep in mind you are after getting a blade to center line on an insert while my work was done to obtain repeatability, they just happen to have overlapping areas.

I guess if I felt compelled to center the cut rather then have a kerf edge on the center line I might visit the washer that Red mentioned. They were once upon a time changed out and thus could account for portions of your "misalignment".

The second change could be caused by how the main table is aligned. We have a 1/2" hole and a 3/8" bolt, if they happened to be centered in one direction in the design then when adjusted could be a 1/16" off with no problem at all (either way). So the next time you have the main table loose for alignment it is likely you will need a new spacer.

Have you had time to see what effect your offset has with splitter alignment alignment?

BTW I did look at the standard table insert and yes it slot is centered.

Just a few more things to think about.

Ed

You mention 'table stability' , Ed. Table stability or the lack thereof coupled with the headstock stability are two issues that will never be resolved except by redesign. Those factors are inherent in the Mark V.

To rid oneself of those issues requires the incorporation of 'old iron' and the elimination of the 5 in1 concept. You can achieve that 000 tolerance factor with old iron but not with the Mark V.

I have previously stated that I have adapted a .005 standard for myself. With that standard - your test scenarios were all great successes. I believe you have demonstrated that quit well.

What got me started on this centerline issue is not a matter of thousandths. My centerline is off 3/16 of an inch. It is, however, quit repeatable ( to within .005").