Mortising Question

[David]

Hi folks,

I'm using a General mortising machine and I'm wondering if this is what I should be getting as a mortise?

I've adjusted the chisel and bit with the .40c method and tried a few variations but I still end up with that little collar at the bottom of the mortise.

I've sharpened the chisel using the Lee Valley cone sharpeners, I've gently tuned up the bit so that it is sharp.

have some suggestions as to what I might try to correct this?

I hope the picture is of sufficient detail.

Thanks for your time,

David.

[Edwin Pawlowski]

The purpose of the tenon is to hide that.

Look at the profile of the chisel and bit and you will realize it is not going to be a flat bottom.

[David]

Thanks Ed for your reply.

The collar I was trying to describe is on the outer edge of the mortise not the center, it's the thin ring (collar) on the outer edge that concerns me.

These 1/2" mortises are to receive 1/2" square metal spindles which will not seat on the bottom of the mortise because of this ring.

I didn't expect to have a flat bottom but I expected that if I drilled a

3/8"- 1/2" mortise I would be able to sink them that far.

From the picture I posted, is this what a mortise machine mortise is supposed to look like, thin ring (collar) and all?

David.

[RicodJour]

Post higher res pictures of the mortise and the bit setup from the side.

R

[CW]

Looks normal.

[SonomaProducts.com]

It looks normal for a one hit mortise. Typically Mortises are elongated so when you start doing slightly overlapping cuts it cleans out much of that and it's not that noticable.

You could pretty easily chisle that out. Make an X at the bottom with the right sized chisel then chisle down the edges with a chisle equal width to the sides. Light taps and lever it and it will p> Hi folks,

[David]

Here are some more pics.

Mortise & Bit Set up

HiRes

'Arrowed' the ring (collar) I'm trying to describe.

I hope this shows the problem better.

Thank you,

David.

[David]

Thanks for the input.

The center round "knobby" piece is not a concern.

It's the thin ring on the edge of the mortise that stands proud of that. I posted some more pics and pointed it out with an arrow.

I was hoping it was a chisel and bit adjustment problem as I'm not to keen on chiseling

100+ of the suckers to get the spindles to fit down in the mortise the required depth.

Thank you,

David.

[Paul D]

A little logical thinking Looking at the shape of the botom of the bit/chisel combo what do I see? Mirror image of bottom of hole

Are both bit and chisel are cutting clean? Yes, guess that means both are sharp.

Which part of the bit/chisel combo is cutting 'ring'? Its happening around the edge of the bit.

So how can I reduce it? Reducing the bit clearence will reduce ring

Can I expect to get a perfect square, flat surface fron a circular motion? Round pegs do not fit round holes.

You have 2 options Drill mortice a little deeper and allow tenon to rest on ring. Or chisel out botom of mortice by hand.

[B A R R Y]

Looks OK to me.

[Swingman]

Why do you think that it needs correction?

Chisel it out if you wish, but it is perfectly fine like it is. You'll find that a mortise should be a little deeper than the tenon length in any event.

[Bigpole]

That is normal. Maybe you can hit it again with a brad point or forstner bit to get rid of the collar. Ted

[Edwin Pawlowski]

OK, that is a slightly different appliction than the normal morise and tenon construction. Generally, the hole is deep enough that there is a bit of clearance and the holding is on the sides of hte joint. In your case, you either have to clean them out or go a little deeper if the fit is that precise.

The setup is perfectly normal. You'll have to adjust the stroke for your application if it is that critical. With wood, it is not. The construction of the bit and chisel won't allow you to get much better than what you have, but some playing around may reduce, but not eliminate, the collar.

[blmfldpaul]

Another trick you might consider is routing out the bottom of the mortise using an undersized pattern cutting bit with a top mounted bearing or straight flute with a collar. Plunge the bit into the mortise using the mortise itself as your pattern. This will ensure that you will not change the X-Y dimensions. You will get a flat bottom at a precise depth. The only thing to clean will be small pieces in the corners will are easily lifted with a chisel. I'm not sure how deep the mortise is but you can probably find a bit with the appropriate distance between the bottom of the bit and the bearing. Or use a collar if you have one. Of course, if you don't need square corners on the mortise you can skip the morticer and go right to the router.

Paul

[CW]

Yes, that is normal. Due to the construction of the bit, there is no way it can remove that.

[Leon]

That is normal. It also leaves a bit of room at the bottom for the glue to collect in. Because of the chisel design you will be hard pressed to not have the shoulder,

[Leon]

The bit would have to be the same width as the distance between opposite corners to get rid of the shoulder. Then you world have a larger round hole instead of a square one.

[Father Haskell]

You could make a punch from a 6" piece of square steel and hammer the bottom of the mortise flat, or you could just leave it as is for glue space.

[Leon]

I did not think of that.... ;~)

[David]

Thank you all for your responses.

I have never used a mortise machine before and didn't know what to exprect.

I'll be using a sharp chisel to clean the ring out of each mortise.

David.