Dovetail fly cutter using HSS

E

ericc

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I have seen descriptions of homemade dovetail cutters using a turned cone shaped arbor with a single carbide insert. For small machines, it has been said that HSS should be used instead. Is there any way to modify this design to use an HSS lathe bit, and sharpen the bit correctly for cutting a shallow dovetail? One would suppose that the cone bottom would be slotted and set screws used to hold in the square shank bit. Would this be feasible? Web searches have not shown any pictures, and maybe that is because of the above two potential issues.
 
sketch it out with a pencil and paper and see if would clear whatever your trying to cut. on paper. if it looks good, try it for real.
my personal opinion of hss and carbide is, hss works better for lighter cuts, carbide does not do its best with light cuts, carbide loves heavy, hot material removal. try both and you will understand the concept yourself. for the price of carbide inserts i think i can buy quite a decent amount of hss blanks.
 
davidh said:
sketch it out with a pencil and paper and see if would clear whatever your trying to cut. on paper. if it looks good, try it for real.
my personal opinion of hss and carbide is, hss works better for lighter cuts, carbide does not do its best with light cuts, carbide loves heavy, hot material removal. try both and you will understand the concept yourself. for the price of carbide inserts i think i can buy quite a decent amount of hss blanks.
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Hi. Thanks for the reply. I did draw it out, and there is a bit of a challenge holding the bit. Also, the cutting will be shallow. There was a post on some forum saying that this was a limitation and there was a magazine article telling how to step down. I guess I'll just have to give it a try. I agree about the cost of the inserts. They are easy to goof up, and HSS is forgiving and inexpensive.
 
That looks like a good idea. I looked at the geometry, and it is not good for square lathe bits. For example, with a 7/8" diameter cone base, a 1/4" tool will give 3/16" thickness on the narrow side of the slot for a bit with it's cutting edge on a radial (center) line. But, 1/4" of an inch down a 60 degree cone with rise/run of .577, the maximum thickness is down to 0.04". This is less than 1/16" and will bend out easily. So that pretty much rules out the standard configuration. If the bit is centered, there will be quite a bit more meat, but then the edge rake would have to be ground in quite a bit to make it parallel or better to the radial line. This means that a square bit will only be able to be sharpened a few times on each end. That is probably why you mostly see the ones with inserts.
 
Most the dovetail cutters I have seen are not inserts but rather a form cutter on a shank. They make inserts for everything you could want. Even ones made just to take interupted cuts. But if making a tool hss is the way I would go. And I use carbide for most all my turning. But a dovetail seems it would beat the snot out of the tool. 80% of the time it would be in the air and when it hits the meat it would be cutting on 3 sides. I would just buy a cutter for 20 bucks or what have you if one is out there
 
Here is a shop made dovetail cutter. you could use an A.R. Warner HSS insert.
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More here
http://www.hobby-machinist.com/show...tail-cutter-from-drill-rod?highlight=dovetail
 
CIMG2207.JPGThis was my quick solution to finishing a dovetail after breaking a factory one. It's a little slow but gets the job done. Advantage is it can be set to different sizes. It's a 1/4" hss blank in a 6" piece of 1144 stressproof. Turned a 1/4 turn from normal orientation for a boring bar and set at 30 deg. wop,wop wop,it goes.

CIMG2207.JPG
 
I have cut dovetails with HSS in a boring bar as well. It is slow going, but it certainly works.
 
I made this adjustable fly cutter head specifically for making dovetails. The tool bit can be swiveled/adjusted to any angle needed. It’s not my design, saw it on the net somewhere? Very simple to make. Fun one-two hour project. And yes, I know the cutting force/pressure is on the capscrew instead of the cutter body. Couldn't think of a remedy?…Good Luck


flycutter.JPG

flycutter.JPG
 
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