Tenon cutter not cutting square

[Albert Lee]

what am I not doing right? I lost about 1mm when I measured it.

The tenon cutter is Omas K408

Was I too quick in moving the carriage?

here is the video link



the hood was removed to show what was going on.

omas1.jpgomas2.jpgomas5.jpgomas6.jpg

[Stanea Laurentiu]

Mount a sawblade onto the spindle, place a magnetic dial indicator onto the sawblade and check if the spindle is perpendicular to the shaper table.

[Joe Calhoon]

Not going too fast Albert. Have you checked the travel height of the sliding table in relation to the shaper cast top? Using a dial indicator or feeler gauge to measure height of table from one end of stroke to other.
Is shaft square to the sliding table? Check this by clamping a straight edge between the spindle spacers checking with feeler gauge out 500 mm or so on the sliding table.

[Michael Todrin]

For diagnosis purposes check both of the shoulders for square relative to the tenon and to the stock. Maybe only 1 cutter is off. Also, maybe check the resulting tenon without pulling the stock back through the cutter.

[Lee Schierer]

Ordinarily you don't want to pull a piece back through a moving cutter. Try making a tenon without coming back through the cutter.

[Warren Lake]

looks like a new machine so would hope it came square to the table. Put a dial magnetic base or other way on the spindle and do a rotation see what the dials says to be sure its square to the table

what speed is the cutter head rated for
what speed are you running
feed rate looks a bit slow, or at least put a backer there as you slowed down more for less break out

dont pull back across the cutter head its already been machined
your blank is two laminations it should be one or three

[Rich Engelhardt]

https://www.scosarg.com/omas-adjusta...-4-v-4-b-31-57

Is this what you have?

[Albert Lee]

https://www.scosarg.com/omas-adjusta...-4-v-4-b-31-57

Is this what you have?

Almost, this is the one I have.
https://www.scosarg.com/omas-adjusta...4-v4-b-12-5-22
D is 250.

[Albert Lee]

Not going too fast Albert. Have you checked the travel height of the sliding table in relation to the shaper cast top? Using a dial indicator or feeler gauge to measure height of table from one end of stroke to other.
Is shaft square to the sliding table? Check this by clamping a straight edge between the spindle spacers checking with feeler gauge out 500 mm or so on the sliding table.

Thanks Joe, I will be doing that. looks like I will be doing a bit of checking today..

it appears the bottom cutter block is cutting concave, the top block is cutting ok if I move slowly.

The tenon in this video is actually one of the best result. others I am getting -2mm differences.

[Joe Calhoon]

Albert,
If I’m understanding right the tenon thickness varies from the shoulder to the tenon end? Or does it vary from one side of board to the other?

Looking at your bottom cutter I think it is Ok but check to see if the insert cutters are seated correctly and slightly below the knickers. I have seen these get off from the factory and that can cause problems. If the sliding table is solid without play it’s no problem to draw the piece back through the cutter. If there is play though this will cause a problem. A lot of in table sliding shapers have this problem but usually the side mounts are sturdy.

Here is how I check side mount sliding tables. See if the sliding table is square to the shaft. You can do the same thing with the cast top.
BD685C1D-936E-4D6D-93FF-4844AA158B4B.jpg 16B720E9-B6BF-4226-B782-5F2D0BF097F9.jpg
Check the travel of the sliding table to make sure it is not running uphill or down hill. This can also be done with feeler gauges if no dial indicator.
F72D515C-EB6C-4689-B1A3-90B8523AE530.jpg 7536597B-9FB3-4023-B48A-26767AE155F7.jpg

[Kevin Jenness]

It appears the tenon is tapered from the root out to the tip. I have seen this result from a tenoner with separate tenoning heads and inaccurately set knives, but I can't visualize how that can happen with two cutters on one vertical shaft unless the table is tipping on the return stroke. I would do the table travel test shown in Joe's second pair of photos and put some up/down torque on the end of the table while looking for variations at the indicator. It seems odd that you would have a problem there on a new heavy sliding table unless there is something loose. Have you tried checking the tenon dimensions without pulling the workpiece back through the cutters?

The feed rate in the video seems quite slow to me.

[Warren Lake]

Its cutting on the back stroke. there are also different results as albert said that is the best one. I never questioned why they taught us not to pull back and should have. Most people do it. Maybe pushing down on the forward stroke and lifting up pulling it back but there should be no play in that set up. Guys cut tennons on a chunk of plywood with a destatco clamps.

[Jared Sankovich]

It appears the tenon is tapered from the root out to the tip. I have seen this result from a tenoner with separate tenoning heads and inaccurately set knives, but I can't visualize how that can happen with two cutters on one vertical shaft unless the table is tipping on the return stroke.

I'm with you on the "I can't understand how you can cut a tapered tenon on a stacked vertical spindle"

Unless like you say the table has vertical play or can rock.

[Albert Lee]

Albert,
If I’m understanding right the tenon thickness varies from the shoulder to the tenon end? Or does it vary from one side of board to the other?

Looking at your bottom cutter I think it is Ok but check to see if the insert cutters are seated correctly and slightly below the knickers. I have seen these get off from the factory and that can cause problems. If the sliding table is solid without play it’s no problem to draw the piece back through the cutter. If there is play though this will cause a problem. A lot of in table sliding shapers have this problem but usually the side mounts are sturdy.

Here is how I check side mount sliding tables. See if the sliding table is square to the shaft. You can do the same thing with the cast top.
BD685C1D-936E-4D6D-93FF-4844AA158B4B.jpg 16B720E9-B6BF-4226-B782-5F2D0BF097F9.jpg
Check the travel of the sliding table to make sure it is not running uphill or down hill. This can also be done with feeler gauges if no dial indicator.
F72D515C-EB6C-4689-B1A3-90B8523AE530.jpg 7536597B-9FB3-4023-B48A-26767AE155F7.jpg

Joe I will do this check but what I want to know is, the tenon cutter is cutting tapper. why is that? if the sliding table is out of square, ok, I will cut trapezoid, but I am not cutting trapezoid, I am cutting a taper on both top and bottom plate.

[Albert Lee]

It appears the tenon is tapered from the root out to the tip. I have seen this result from a tenoner with separate tenoning heads and inaccurately set knives, but I can't visualize how that can happen with two cutters on one vertical shaft unless the table is tipping on the return stroke. I would do the table travel test shown in Joe's second pair of photos and put some up/down torque on the end of the table while looking for variations at the indicator. It seems odd that you would have a problem there on a new heavy sliding table unless there is something loose. Have you tried checking the tenon dimensions without pulling the workpiece back through the cutters?

The feed rate in the video seems quite slow to me.

My thought too, I can't visualise or think of a reason why it is cutting tapered, and yes you are correct, its tapered from root out to the tip.

looks like another interesting issue that can to be documented...