Imperial mortising bits for slot mortiser?

[Martin Shupe]

I was told that one could find quality English (inch) bits for a slot mortiser, instead of buying ones measured in mm.

Can anyone suggest a good source for such bits?

I am looking for 1/4, 3/8, 1/2, and 3/4.

Thanks!

[Rick Fisher]

http://www.lagunatools.com/accessori...ories-mortiser

I would ask if they are actually imperial or just close, but they are marked as imperial and don't seem really cheap ?

[Kevin Jenness]

Buy end mills from any machinist supply house (MSC, McMaster Carr, Enco, etc.) The shorter and stouter the better to produce accurate mortises. I have several long bits like the ones I have seen on the Laguna site and they are next to worthless due to bit whip- the mortises produced are wider at the mouth than the bottom. Plunge in small increments to minimize this problem.

[John TenEyck]

What Kevin said. I tried some Amana mortising bits. They whip so badly that I consider them worthless. Two or three flute, center cutting end mills, however, produce a perfect mortise. They also are cheaper.

John

[Rick Fisher]

Wow .. great info .. I will remember this ..

[David Kumm]

Spiral end mills are not the best choice for a hand operated mortiser like the FB 250. Straight flutes are better as they don't have a tendency to pull the bit into the cut. Particularly on large 1/2-5/8" mortises. I ran an FB for years but have replaced it with a used BacciDSCN2884.jpgDSCN2885.jpg The spirals work well on the automatic machine. Dave

[Rick Fisher]

David..

When I look at the Bacci, it seems like it has less features than the Felder or Griggio / Martin.. Yet something tells me its another step up ? Whats your opinion having owned both ?

[Kevin Jenness]

David has a good point about the tendency of large spiral end mills to self-feed on slot mortisers with low friction mechanisms. Mine is a Steton with dovetailed ways and enough friction in the feeds to largely avoid the problem. I did experience it once when using a long (3 1/2" cutting length) 5/8" end mill which started working its way out of the chuck. I went down to a 2 1/2" cut length which has less vibration and stays put in the Westcott chuck.

When I was using a Felder mortiser I found that spiral mills over 3/8" were not a good idea as they were too hard to control. We used 4-flute birdsmouth bits from Onsrud (they seem to have discontinued making them- Morris Tool has them up to 1/2") and Mini-Max. They are not suited for plunging and have to be ramped into the cut. They can be sharpened without loss of diameter and cost more than end mills.

Looking at the Laguna link from the initial post, the 1/4" - 1/2" bits at the top of the page should work well, though 4-flute bits tend to be stiffer. The long mortise bits shown there are similar to the ones I have had problems with.

The Bacci and similar machines known as oscillating slot mortisers are a different class entirely. They have an adjustable infeed rate that minimizes bit whip and produces more consistent results than a manual machine. Naturally they cost more- I see them offered used for $6-8,000.

[David Kumm]

I have about 2500 in the Bacci. I make doors and the 5/8" bits on the Felder got tiring in a hurry. Mainly just my issue as leaning slightly over the joystick caused me back problems. The benefit of the oscillating mortisers is they are faster and more uniform. Slot mortisers can leave a slightly different sized mortise in end grain vs long grain- just enough that you need to rasp one a little. The auto machines minimize that tendency. There is a lot going on with them pneumatically so they are tough to figure out if you buy one not working. I have a mediocre video on you tube showing it in action. Dave