PDA

View Full Version : Cutting an internal keyway on a shaper?



Black Forest
10-01-2014, 06:31 AM
A friend asked me to cut an internal keyway in mild steel on a part he had made for his wood splitter. The keyway needs to be 14mm wide and 4.5 deep. The widest tool I have for the shaper is 12mm. So that will mean at least two goes at it. Would it be better for me to use an 8mm wide cutter whereas I have to set it over anyway?
Or center the 12mm cutter and then skim each side or take one 12mm cut and set it over 2mm to bring it to dimension?

My gut feeling is to use the 8mm cutter. Or should I grind a 14mm cutter?

My shaper is quite large with a 550mm stroke and weighs around 700 kg.

Sun God
10-01-2014, 06:51 AM
Go with your gut. Smaller volume of cut -> less part flex, less machine flex, less clamping force required on the part. It might take longer but if it's a government job and you're going to have to make two passes anyway, what difference does it make? May as well make them two good passes.

becksmachine
10-01-2014, 08:28 AM
Don't get greedy here. :)

Have you cut an internal keyway in the shaper before? Do you have a method of holding this part to allow access to the bore and a poke bar to hold the tool? Also the clapper block will need to be tied down or the tool won't stay in the cut.

It may be that you have a stout shaper, but the weight/brand of the shaper is not going to be the limiting factor here.

Think of it this way. If you were using your lathe to take a great hogging cut on the OD of some part, would you attempt to cut a 14mm wide groove in one pass with a 14mm wide tool bit? Just think of trying to use a parting tool that was 14mm wide. Do you think it would chatter?


Now imagine trying to put that groove in the bore of that same part, holding a 14mm wide tool in a boring bar. Do you think that would chatter?

My point here is this, cutting an internal keyway in a shaper is going to require the use of a "poke bar" which is roughly equivalent to a boring bar in a lathe, and this will be the limiting factor. I think you will need to take many more than 2 or 4 passes to accomplish this feat.

You may both be better served to invest in a set of broaches to cut that keyway using a press, much quicker and more reliable.

Dave

Black Forest
10-01-2014, 09:07 AM
Don't get greedy here. :)

Have you cut an internal keyway in the shaper before? Do you have a method of holding this part to allow access to the bore and a poke bar to hold the tool? Also the clapper block will need to be tied down or the tool won't stay in the cut.

It may be that you have a stout shaper, but the weight/brand of the shaper is not going to be the limiting factor here.

Think of it this way. If you were using your lathe to take a great hogging cut on the OD of some part, would you attempt to cut a 14mm wide groove in one pass with a 14mm wide tool bit? Just think of trying to use a parting tool that was 14mm wide. Do you think it would chatter?


Now imagine trying to put that groove in the bore of that same part, holding a 14mm wide tool in a boring bar. Do you think that would chatter?

My point here is this, cutting an internal keyway in a shaper is going to require the use of a "poke bar" which is roughly equivalent to a boring bar in a lathe, and this will be the limiting factor. I think you will need to take many more than 2 or 4 passes to accomplish this feat.

You may both be better served to invest in a set of broaches to cut that keyway using a press, much quicker and more reliable.

Dave

Yes I have cut internal keyways on my shaper.
I have many tool bit holders for cutting internal keyways.

Yes I have a way to hold the workpiece.

By passes I was referring to the setting over of the cutter after cutting the first keyway. Not the correct terminology I think. So I mean if I cut a first keyway 8mm wide by 4.5 deep then I will set the workpiece over 6mm to get my 14mm total width.

Old Hat
10-01-2014, 10:52 AM
The lenght of the keyway is what matters relative to the tool's width.
You'll need to adjust your rake angle to ballance out side-pull on a long keyway.
Hench trimming right and trimming left wil require separate grinds on a long keyway.

Preferred method is a full width tool bit, you can heat and upset the end of the bit.
If high-speed just let it cool quickly in an air currrant.

Now grind to 14mm wide.
14.0003mm if for an ISO keyway . . .. :p

becksmachine
10-01-2014, 11:52 AM
Yes I have cut internal keyways on my shaper.


Ok, good for you!

I just didn't know. :o

Dave

Black Forest
10-01-2014, 02:02 PM
Ok, good for you!

I just didn't know. :o

Dave

I appreciate you telling me all that you did. I am no expert that is sure. I have cut quite a few internal splines recently and they turned out very good. Just never cut an internal keyway 14mm wide. 12mm was the widest I think.

boslab
10-01-2014, 06:58 PM
It's a hell of an odd keyway, it doesn't sound standard, I would take it out with a narrower tool, a 14 is going to generate a hell of a force on the tool, I'd have a guess at a bit of chatter, or worse a bit of shatter!
I have cut big ones but on a slotter with an insert cutting tool, not carbide btw!
Mark

mickeyf
10-01-2014, 08:23 PM
I would not try to do it all in one go. You can either use the less wide tool and move it over for a second (third, whatever) cut, or use an undersized tool and then finish with an exactly sized tool after having removed much of the material first. I've tended to do the first, mostly due to having a non-critical application and being too lazy to take the trouble to grind a perfectly sized tool for a finish cut.

dp
10-01-2014, 09:04 PM
Having given this some thought I think it best to plunge cut one side of the slot then shift over and plunge cut the other side. That way you're flexing the tool holding bar only in the vertical plane rather than having spring cuts in two planes. The cutter should be relieved on both sides as well as on the work side.

Black Forest
10-02-2014, 03:40 PM
I got to 3.6mm deep on a target depth of 4.5 when I encountered this defect. It looks like they welded a hole closed but did a bad job of it.

I actually cut the keyway on my lathe. The part was too big to hold easily on my shaper without building a special jig to hold it. It went quiet fast on the lathe. I was able to use the power rapids on the carriage so no hand cranking. I ground a 14mm wide cutter and did cut the keyway full width. I did get a lot of chatter but based on the terrible job of machining on the workpiece I wasn't too concerned. The inside boring where I cut the keyway is so rough it looks almost like they cut threads! Overall a very sloppy job of machining.
http://i853.photobucket.com/albums/ab91/burnandreturn/woodsplitteradapter_zps385b7249.jpg (http://s853.photobucket.com/user/burnandreturn/media/woodsplitteradapter_zps385b7249.jpg.html)

Old Hat
10-03-2014, 02:38 AM
It's gorgeous!
Well Done!

Black Forest
10-03-2014, 05:00 AM
It's gorgeous!
Well Done!

Just to be clear I did not machine the original part. I just put the keyway in the part. Gorgeous it ain't but it might work for the intended purpose which is to have one of the conical screw type woodsplitters mounted on the part and driven by the owners tractor.

Old Hat
10-03-2014, 09:00 AM
The keyway! Dufuss, it's Gorgeous!
Sharp, perfectly trunkated in the hole.... Crimmany! yer a hard man ta please.

thaiguzzi
10-03-2014, 10:33 AM
Bit late with the reply, especially that we now have a photo, but i was going to suggest/ask the op - we don't know the size of the bore. If it was 2.5", no probs making a 2" diameter boring bar, then a 14mm wide keyway could be done in one pass. In hindsight with photographic evidence, that is a large bore (pretty obvious really with a 14mm keyway!) and a large boring bar could quickly have been cobbled up to fit in the bore, hence rigidity.
My current project is making a batch of 10 Dickson tool holders on my 8" Boxford shaper. Two billets of steel 7.5" long to clear the stroke give me 5 tool holders each. As some of you are aware, the Dickson interface between holder and toolpost is 4 x 90 degree V's and a T slot to pull it in. Now, some operations could no doubt be quicker, and possibly simpler on my vertical mill (73 Tom Senior M1), but the project is an exercise in my own and the shaper capabilities. The T slot is being done in one pass about 1/4" wide, hand feed about a thou to 2 thou max DOC. Slow, but no extra milling cutters purchased and a nice job. Every detail is being done on the shaper. The mill will not see any of the work. Toolbit is 5/8" shank butt welded HSS r/h lathe grooving tool modified and sharpened to suit on my little Stent T&CG. Gotta love your shapers!

MichaelP
10-04-2014, 06:19 PM
A friend asked me to cut an internal keyway in mild steel on a part he had made for his wood splitter... Just to be clear I did not machine the original part. You have to choose friends more carefully. He is not German, is he? ;)