Who needs a surface grinder?

[Gritineye]

Inherent problem with shapers is they will always cut at a angle. This may be absolutely tiny on the best shapers but never the less is true.

Interesting statement, I think I know what you mean but would like to know more please..

 

[Wallace]

Shaper slideways are not designed for grinding grit like a surface grinder.

 

[Wendelspanswick]

Interesting statement, I think I know what you mean but would like to know more please..

I was pondering that as well and didn't understand the comment.
On a Shaper the table traverses on the return stroke so all the cuts are perpendicular to the front edge whereas on a Mill the table is constantly traversing so the cut is at a slight angle to the front edge when fly cutting.

 

[MrFluffy]

The cutting action of the shaper tends to produce wedge shapes when they have a few miles on the gibs and you fixture off the original table I think is what people are hinting at.
You can bolt a sub plate the table and shape it place then bolt the vice to that to sort of compensate, or spend a long time sorting the gibs out. The table support at the front and if people have bothered to use it plays a big part in if this is bad or not. Some of these old beasts have a lot of miles on them now. Maybe you can take the ram off and surface grind it flat on the surface grinder you didnt need to save eons rescraping it back plane

Also a shaper tends to knock things about slightly on the table unless they are very very firmly clamped.
I spent two nights shaping out a belt pulley on mine this year only to find it had knocked the indexing rig out of parallel out near the end and cut the teeth taper shaped slightly. 8 hrs of being thumped at the start of the cut, yes I probably got too ambitious at times and wound too much cut in due to the length of the task but it was frustrating all the same.

 

[Rocketman]

Interesting statement, I think I know what you mean but would like to know more please..

Firstly I believe it's to do with deflection of the shaping cutter. So the longer the item the harder to hold a specific tolerance over it.

Secondly as the machine wears (on a decent machine in good order this probably isn't so much a issue) the ram at maximum extension there will have the most available movement compared to far less at minimum extension.

 

[Wendelspanswick]

Firstly I believe it's to do with deflection of the shaping cutter. So the longer the item the harder to hold a specific tolerance over it.

Secondly as the machine wears (on a decent machine in good order this probably isn't so much a issue) the ram at maximum extension there will have the most available movement compared to far less at minimum extension.

But that's no different than a mill with wear?

 

[Rocketman]

But that's no different than a mill with wear?

Not quite. Basically with the shaper the forces on the cutter and machine increase as the ram extends where as in a mill or surface grinder the forces are much more constant - right in the middle.

So yes a worn mill, VMC or surface grinder will be pants in the situation where all is good they are not effected by the same forces.

 

[Gritineye]

As long as your shaper is well set up and maintained there is no reason to get a less than perfect finish on even the hardest material....

sent in Morse code from my mobile shaper ratchet.

 

[MrFluffy]

Your into dangerous down the rabbit hole territory with that last statement , first define perfect. Then define how your measuring it in terms of flatness and rugosity & can I check it with my optical flat afterwards, or will it be blue on a surface plate flat, or looks ok held up against a straight edge?
Even when mine is cutting well, it still makes a slightly uneven cut at the start of the cut when the shock load of the tool hitting the workpiece is still reverberating round the tool and I have very oversize tooling to try and eliminate flex (first indication of flex is the thump of the vice hitting the floor after its been pushed off the table if the belt is having a really good day. Looks nice to the eye though and for most of the time it works for the job I have planned for it. I like using it because its relaxing to use as a machine from another time thunking away quietly, but then I like using the sg to get things really flat or a bearing fit/shoulder or profile ground into a rod in the spindex stuck to the mag etc.