How to make a 1/4" dovetail cutter using HSS

[wannasteam]

G'day all

I am building the PM Research shaper and need to cut a 1/4" "inside" dovetail for the tool holder.

I've hunted around and I couldn't buy this thing for less than around $80.  I can't justify that for a one-time use tool.

I thought I'd make one out of 1/4 round HSS...but I can't find any resources on how to go about this.  Lot's of tutes/vids on making ones that use carbide inserts but none I could find on using HSS.

I can cut the basic shape on the lathe but I need a bit of help with the cutting edge geometry

I would like to ask the collective for any info, drawings, videos on how to go about this.

Cheers

Joe

[vtsteam]

What about using a slitting saw (if you have one), or even a fly cutter with a hand sharpened lathe tool and an angle vise?

[wannasteam]

Hmmm...hand sharpened lathe tool and angle vise.  Must have a look at that.

It's going to be tight tho...the dovetail is only 1/4" at the wide part.

[TLGriff]

How long is this dovetail? If it's not too long you can make a slotting tool to use in the quill of your mill. Here's a pic of a slotting tool I made to square up a slot in a receiver that I made.

Tom

[Arbalist]

That's not a bad idea Tom. 

[wannasteam]

Hi all

Thanks for the replies.  I've attached a photo to show exactly what I am trying to do.  As they say about a picture worth a 1K words...

I've got a piece of 1/4" HSS that I can grind to dovetail shape but I need info on the geometry of the cutting edge(s).

Cheers

[drmico60]

Hi all

Thanks for the replies.  I've attached a photo to show exactly what I am trying to do.  As they say about a picture worth a 1K words...

I've got a piece of 1/4" HSS that I can grind to dovetail shape but I need info on the geometry of the cutting edge(s).

Cheers

That is a rather small dovetail. I cannot see how you could make a dovetail milling cutter from 1/4" round stock to those dimensions.
In the absence of a suitable cutter I would make the dovetail using a different technique. One way would be to use a staight milling cutter and angle the work to cut the two dovetail faces. If you use a small cutter, say 3 mm, then you will not cut too much into the land between the dovetails. An alternative would be to redesign the part and us a built up dovetail as shown here:
http://mikesworkshop.weebly.com/making-small-dovetail-slides.html
Mike

[TLGriff]

That is a perfect application for the technique I described since it's a small dovetail and the material is brass. Just make a slotting tool with the angle of the dovetail align it with the bottom of the slot and work your way out each direction to form the angle, sort of like broaching. I would mill the cutter out of O1, harden it and stone the edges for a good finish or you could just grind it out a HSS bit if you have a way to hold it in the spindle (maybe a fly cutter). Don't forget to include a little clearance behind the cutting edge. You are correct, making a rotary dovetail cutter that small would be very difficult. The fun part is you can machine the whole thing without turning your mill on.

Tom

[GordonL]

I have done similar things using a boring head. You have to make a rather small "boring bar" and go slow.

[grg12]

Hallo

I was in situataion similiar to yours Joe - for some reason dovetail cutters small enough for my "mill" cost a fortune - so i tried to make one from 12mm from silver steel (in states it's called "drillrod"). Outside shape been turned on lathe, "tooths" cutout with these little brown abrasive disk (dremel tool) in indexing head. Hardened with propane torch (heat up to cherry red, throw in water, then clean a bit of surface near to cutting edge and begin to heat the cutter with small flame - directed at the shank - when the cleaned surface turns "yellow straw" - throw i in water) . Sharapend on the "front" face of tooths and ground a bit of relief on back with the same abrasive discs - "freehand". And then used it to cut some dovetails in 11SMnPb37
The big center hole is there to make sure that center part of cutter does not rub. Tooth "front" faces arene a little bit (half of the thickness of abrasice disc  ) deeper than the radius line, and freehand grinding of relief is easy if you don't clean back surface of the tooth - slowly grind the surface clean leawing a thin (0.5mm) black line at the cutting edge.

Gregor

[vtsteam]

Nice work grg12. 

[AussieJimG]

Well done Gregor

Jim

[wannasteam]

G'day all

Thanks for the many ideas. 

Much to consider and file away for future use.

What I'll try to do is mill off one of the legs of the dovetail so I can get a 3/8" dovetail to cut one side, make up a suitable other leg then screw them together.  This way, I can set the proper fit before I bolt them together.  I hope this makes sense.

I'll post pics later.

Thanks again.

Joe