Keyseat type cutter needed

[Mark Soderquist]

The angled cutter is required to make the 10 degree locking notch.

 

[Mark Soderquist]

Mostly a HSS is hard and a thing that it won't cut must be harder so Carbide is needed.

The time that this is not true is when the HSS cutter is hard enough..but the fixturing is not solid enough to resist cutting forces, so the HSS cutter quickly dulls.

One test is to strike a part with a file, if the file can cut the part then a proper set-up should allow HSS.

At a certain part hardness, the carbide cutter can be a cost-saving.

The part held in the lathe photo (post 17) would be considered a poor set-up.
A skilled machinist would put a mill jack under the part if forces were toward the table
If the cutting forces were to the cross direction, then an angle plate would be placed/bolted in the go-direction to bump solid the part perhaps with the angle plate touching or with an adjustment screw to bump the part.

The set-up shown would be poor with a HSS or carbide cutter.

I usually consider a mill fixture should be made of 1/2" stock.

Grinding fixtures often can be 3/8 stock if not too long..

Thanks for the advice. Yes the set up was poor also. I'll incorporate those ideas for a better more solid set up. The carbide cutter did chew right through it though even with the poor set up but it's better to do it right.

 

[michiganbuck]

The simple test for milling is to push hard with one hand and see very little take-up of a thow or so (none is best) and then get rock solid. For grinding you push with three fingers. This is for light work, like in the hobby class.

To appreciate cutting force, consider how hard you need to push a 3/8 drill just to drill through a mild steel part with a hand drill motor, or how hard you need to push a HSS lathe tool bit into a bench grinder wheel.

A poor setup may do the job but will dull a carbide cutter (any cutter) more quickly.

 

[michiganbuck]

How do you index for milling the next notch?

Making that setup more solid would not be my choice, I would put the cylinder on the machine centerline and then index the next notch.

The simplest improved setup might be to wrap the cylinder with heavy-duty (6 Mill) masking tape and put it into the lathe chuck jaws...Might also add a fine thread brass screw touch to the go direction.

Very handy would be to have an index of some sort so with making the first location good, you could just 6 index to the next position.

An index that goes on the back end of your spindle can be handy, perhaps bore out a 12 tooth gear to close fit your spindle tail end.

 

[Mark Soderquist]

How do you index for milling the next notch?

Making that setup more solid would not be my choice, I would put the cylinder on the machine centerline and then index the next notch.

The simplest improved setup might be to wrap the cylinder with heavy-duty (6 Mill) masking tape and put it into the lathe chuck jaws...Might also add a fine thread brass screw touch to the go direction.

Very handy would be to have an index of some sort so with making the first location good, you could just 6 index to the next position.

The notch is pretty basic the complex part is the tapered lead. I have figured out a way to mill it by clamping the cylinder to the rotary table by running a fixture through one chamber making it offset the correct amount from the center line of the rotary table. Then I mill .020 deep and rotate the table so that the cylinder turns away from the cutter gradually. Next set up required taking everything apart and resetting.After your advice I am thinking of a way to run a second fixture through the opposite chamber and fasten it to the rotary table also to provide much more stability with two points of contact on the cylinder.The cylinder will have to rotate off center to get the taper unless I missing something. Pic is of what I'm trying reverse engineer.Second pic is a Bob Munden cylinder which is better the lead is tapered on the curve

 

[Mark Soderquist]

I will use these test procedures to verify the set up. Thanks!

 

[michiganbuck]

QT: [After your advice, I am thinking of a way to run a second fixture through the opposite chamber and fasten it to ]
So still 3 setups, seems a waste of time and chance for error.

The correct set-up is to fixture it once and then index it to the other locations.

 

[Mark Soderquist]

QT: [After your advice, I am thinking of a way to run a second fixture through the opposite chamber and fasten it to ]
So still 3 setups, seems a waste of time and chance for error.

The correct set-up is to fixture it once and then index it to the other locations.

How do you "fixture it once" to do six (12 with the lead cuts) operations with each fixtureing requiring an off center position?

 

[michiganbuck]

with one part chucking at the center. and using a 6 place index so each next index would match the first setting.

 

[Mark Soderquist]

with one part chucking at the center. and using a 6 place index so each next index would match the first setting.

Explain to me how you do a tapered cut like this with "with one part chucking at the center."?

 

[Mark Soderquist]

with one part chucking at the center. and using a 6 place index so each next index would match the first setting.

The lead (grove leading to the notch) is tapered on the curve of the cylinder.