Milling Dovetails

[chucketn]

I am in the middle of making Harold Halls Deluxe Grinding Table. I need to mill dovetails in several parts. The dovetails are 60° and 8 mm (.314 in) to 8.5 mm (.335 in) high . As I’m getting ready to order my first dovetail cutter, what size is recommended?
I will be ordering the cutter from LMS and sizes available are 3/8”, ½” and ¾ in. The cost difference isn’t that much, but I don’t want to order all three now.
Any other comments on milling dovetails welcome, as I’ve not done them before. Speeds and feeds? DOC? Multiple passes? Material is mild steel. Mill is an HF X2.
Go easy on this noob, eh? Thanks in advance.

Chuck in E. TN

 

[Omnimill]

I've just measured my 1/2" cutter (3/8" shank) and it won't cut much deeper than 1/4" so I guess you'll need the 3/4" or make up a custom fly cutter.

Vic.

 

[websterz]

Cut as much of the material out as you can with an endmill then use the dovetail cutter just for the angled bits. When using a dovetail cutter I like to make one climb cut as a finished tool pressure pass, just to make things nice and neat.

 

[chucketn]

Would it help, or be worth the trouble to clear some of the undercut part with a woodruf or T-slot cutter? He-he, don't have one of those either... ???

Chuck in E. TN

 

[hobby]

No,
Once you have a clean slot, go directly to the dovetail cutting.

Because a 'T" slot cutter will take out to much dovetail angle material.

Youll find out how easily it is to use the dovetail cutter, just take light passes testing for chatter, and just keep working it, I find it helps to raise the dovetailbit a few thou. above the bottom of the slot, but that's just my preference.

 

[chucketn]

So the bottom of the female dovetail bit doesn't have to be perfect? I have seen mentioned it's harder on the cutter to face the bottom of the dovetail opening with it.

Chuck in E. TN

 

[hobby]

If the bit bottoms out, you now have 2 surfaces at one time in contact with the bit.

If you want to bottom it out for the sliding fit of the male portion, then by raising the bit a couple thou. above the slot bottom, then do all the dovetail cutting, then after, yu could lower it to the bottom to clean it up.

That should not affect the overall dovetail slot.

 

[chucketn]

Thanks to all who replied. Love this place!

Chuck in E. TN

 

[hobby]

Your welcome.

I think I need to correct myself on the bottoming out part,
as the dovetail cuts deeper into the side walls, it will of course have both surfaces of the bit in contact with the bit, however, the bottom contact is gradual unlike it the whole bottom of the bit was touching the bottom at one time,

As a side note, (I don't think) it would not cause any major problems if you did, allow the bit to bottom out, as long as you work the cutter chatter free, with DOC. and feed rates, speed etc...

 

[Omnimill]

Many production Dovetail slots I've seen had the centre relieved a little - ie a slot drill was run through first, and a little lower than the subsequent Dovetail cutter. This means of course that only a portion of the Dovetail cutter was cutting on it's lower surface.

 

[chucketn]

Omnimill, that's what I was talking about a few post's back. I think I'll try that when I get the cutter and start on those dovetailed parts.

Chuck in E. TN

 

[steamer]

Depends on which surface your bottoming out on.

In machinery handbook, check out the concept of roll dimensions also....makes cutting mating parts much easier.

Dave