Cutting internal Keyway

I cut keyways this long and longer all the time on my Bridgeport vertical slotter. Not as rigid a unit as yours. But, I use HSS for the tool bit - better. The deflection force in the tool bit is a constant, i.e. it doesn't change from the start of the cut to the end. What changes is the length of the ram in the shaper, or how far out it is from the support. I suspect you may have something worn/loose in the shaper itself.

Karl

How about a broach?

John,

In my experience, the complete key to getting a shaper bit to not push away is the shape of the cutting edge. It has to have enough rake to bite into the stock. It also has to be sharp. Even a little dullness (use a magnifying lens to look for a line of light along the cutting edge - if found = dull).

You can go to a smaller tool, but that will take longer and have to be resharpened more often. Sometimes it works better to do a small tool for a way, then switch to a larger tool and repeat until at depth. If moving from side to side to create the final width, try to take the same amount of each side of the key.

As to how much you can cut - if it stalls, it's too big. You'll know. If you don't take enough per cut it will push out and chatter, dulling the tool and making it hard to get back into the cut.

I spent 30 years watching and working with some master shaper operators (they would hold tenths and often make complex pieces faster and more accurately than the CNC guys could). It all came down to very carefull control of all the angles and clearances of the cutters.;

Karl Pearson

That makes sense now that you mention it. I will check for play when I get home....not sure what to do if I find play in the ram besides tighten things down a bit.

As for using a broach, yep, could do that, but I am trying to use the shaper I paid for first. Just bugs me that I can't get this to work.

I made that on a shaper. Keyway was 5mm wide, about 50mm long. The tool was made out of drill-rod. Worked very good. Angles were 8° rake(?) and relief. If you want, I can make a photo of the setup.

Nick

If you have a loose ram on your Atlas shaper, it can be tightened up by removing a shim(s). Atlas have flat surfaces rather than dovetails - so layers of shims were used to take up wear rather than gibs. Also, try to make the ram travel length as short as possible to take advantage of the machine itself. You can adjust the ram travel length so it only moves say

The distance I have the ram traveling if much longer than need be, it was set up that way to match the (random) location I mounted my vise at. I have an extension table I build to support my Hardinge dividing head for working with gears, not that I have done this=E2=80=A6.just set up so I can=E2=80=A6.imagine that =EF=81=8A

Make your cutter out of 5/8 round stock. Drill a hole in the end for a set screw, and a through hole for a .25 cutter. Use the set screw to hold it in place and simply drop the cutter a bit every couple of passes, leaving the table adjustments alone. You may wish to mill a flat on the bottom of the round stock for chip clearance. But the sides of the hole in your workpiece will of course hold the cutter bar in place and not allow it to deflect.

Think of it as a single toothed reciprocating broach

Gunner

Political Correctness

A doctrine fostered by a delusional, illogical liberal minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.

snip----

Most likely a single toothed reciprocating broach that seizes in the hole. The solution to this problem, assuming a shaper is the machine of choice, is to learn to properly sharpen cutters, with the proper combination of front clearance, to control self feeding, and rake, to encourage the tool to dig in. Karl Pearson has it right.

Harold

Yes. This is the same as boring deeply on a lathe, where the boring bar is long and not so rigid. By adjusting the "angle of attack" you effectively multiply the rigidity.

Karl,

Can you expound on the degree of rake? And when you say sharp....are you talking razor sharp? To give some background, I put a 7 degree rake on the bit and made it somewhat sharp but not at all like a sharp knife.

Thanks again (and thanks to all for the very helpful pointers.

JC

Seven to ten degrees of rake should be plenty for mild steel. The rake angle depends on the material being cut. WIth brass or bronze, you might even end up with zero or slight negative rake.

As to sharp. A razor is not necessarily sharp. It has tremendous rake and back clearance, but it is what the condition of the last two atoms of the cutting edge that determines sharp. Once you have the correct rake, back clearance and side clearances established on the cutting tool, then you carefully use the softest wheel in the shop to 'touch up' the front and top of the tool. This should leave one clean surface from the cutting edge back in all directions. No bunches of little flats strung together.

Then you very carefully take a hone stone and 'refine' the edge.

Using the hone is one of the tricks. Lay the stone on the cutting edge AND the face being honed. (This face is usually concave from shaping it on the grinding wheel). Then move the hone stone across the cutting edge (many teach to only move it in the direction the chip will go - this isn't really necessary, but goes along with the teaching of properly using a hacksaw by cutting on the forward stroke and lifting on the return, which reinforces good habits IMO).

I like to do a couple strokes on one face of the cutting edge, then a couple on the other - reduces the chance of messing up the grind. six to ten strokes total on each face should be enough (depends on the courseness of the grinding marks).

When honed properly, you should be able to take a magnifying lens and see the cutting edge as a straight, unbroken line of nearly zero width. If, as you turn the edge this way and that to the light, you see a line - it's dull. Time to step back to the grinder and lightly touch it up and try honing again.

Hope this helps.

You should have heard my journeyman describe his stance at the wheel, how he held his elbows, how he watched the tendons on the back of his hand to judge his grip and how he worked to feel that he was finishing his grinding with just one piece of grit on the wheel touching the tool at a time. Very fussy, very pretty tools, could cut 1" deep, an then finish with a .001" pass and still take a chip without touchup.

Karl

This might not be on point, but I have found that locking the clapper so it cannot move helps prevent dig- in when cutting internal keyways. Yes, the tool rubs on the back stroke. Jim.

Nick I would love a photo...worth a thousand....well, you know :-)

thanks a bunch (too all)

I made even more than just one photo. :-)

See my other posting: "Keyways on the shaper. My way.".

Nick

Obviously you make the broach a some thousands smaller than the hole..but seize in it??

Gunner

Rule #35 "That which does not kill you, has made a huge tactical error"

I got the impression that you suggested using the hole as a guide. Most soft metals are pretty good at galling, so it likely would seize, particularly when you're making chips. All it takes is a tiny one to enter the hole between the hole and shank and it's all over. If it was a one stroke kind of deal, I probably would have a different opinion, but the idea of a fairly close fitting shank running back and forth inside a hole makes me a bit uneasy. Did I misunderstand you?

Harold

Nope..you understood me clearly. I also (IRRC) suggested cutting some flat on the bottom of the "broach" for chip clearence. A few thousand clearence between the "broach" and the side of the hole wont allow much chips to get in there of any size..it will wipe them off for the most part.

Least..thats what I did the last time I had to do a key slot in a large flywheel and I got deflection from the tool I made originally.

So I did exactly as described and it worked fine. A bit tedious letting out more and more cutter each couple of strokes..but it worked fine.

Gunner

Rule #35 "That which does not kill you, has made a huge tactical error"

I am convinced that it is my cutter shape and material. Is hardened Tool steel a satisfactory material? I heat treat it at 1500F, H20 quench, a file runs right over it, Seems very hard, I know HSS is preferred.

I will have to try your suggestion as soon as I make a holder for the bit and bar that fits the claper I have.

thanks again to all for the help