View Full Version : power cutoff limit switch for shapers

02-21-2011, 06:48 PM
What kind of switch do I need to cut power to the motor for a 1hp motor on a small shaper? There are roller switches for this kind of thing, but is there a cheaper way to do it? Or perhaps I can control the spikes which will allow me to use some weaker switches ...

In this picture on Kay Fischer's shaper page, he recommends mechanical switches (why?); i thought the purpose of the AC adapter was supposed to reduce the need for bulky resistant switches:

Optics Curmudgeon
02-21-2011, 06:59 PM
If I was doing it, I would use a regular magnetic starter and hook the limit switches (normally closed) in series with the stop switch. You would have to back the feed screw off of the limit by hand, but this is a "last ditch" protective scheme anyway, right? A mag starter is the thing to use for a 1HP motor anyway.

J. R. Williams
02-21-2011, 07:00 PM
I added a large mushroom head emergency stop switch to my small shaper. All it takes to stop the unit is to hit the switch and it stays locked out until you rotate the head. The unit was mounted in a box on a plate installed behind the 'as built switch' so no additional holes were drilled into the cabinet.

02-21-2011, 07:02 PM
I have a large power-off switch in case of emergencies, but I'd like to use this small limit-switch scheme for automatic operations

02-21-2011, 07:43 PM
Look for micro switches. Lots of different versions available, sealed, plunger, roller, etc. Just need one to handle an Amp or so and place it in series with the latching relay of magnetic motor starter. The Stop button will also be in this loop.

Place these where Kay shows "limit switches" and thereby use 12V DC to energise the coil of the AC motor starter.

If you wire it right, you can reverse feed, hold Start button down until table backs off the micro switch then magnetic starter will latch and you can take your finger off the button. It will run until the latch circuit is broken by Stop button or limit switch.

These micro switches will be "mechanical" but are definitely a case of small switch/low voltage controlling big switch/high voltage.

03-08-2011, 06:07 PM
I'll be continuing this discussion in another thread (found here http://bbs.homeshopmachinist.net/showthread.php?p=648405). Will post all the parts, and schematics ...

Forrest Addy
03-08-2011, 07:31 PM
Why would you need limit switches on a crank drive shaper ram?

Safety first: First thing you do after changing the stroke length or the ram extension is slowly jog the ram through a complete bull gear rotation to make sure there are no collisions. In a clutchless machine you hand crank the ram. In a clutched machine drift the clutch to gently set the bull gear in rotation.

A hydraulic machine already has limit stops.

One thing to sweat in a machine packing lots of mechanical inertia: chopping motor power doesn't safely stop it. It coasts down until it comes to rest via friction or via breaking off expensive parts. If you want a quick safe stop you better think motor brake.

03-08-2011, 07:40 PM
Why would you need limit switches on a crank drive shaper ram?
Probably so he can set up a job and then go and do something else. Machine stops when it reaches the limit switch. I seen similar setups before.


Forrest Addy
03-08-2011, 08:18 PM
Ah! Cross travel L/S. My misconception.

Which brings another point: Why would shaper cuts lead to enough time to accomplish anything meaningful. Good finishes and size control shouldn't take forever. When a shaper is properly set up, the DOC, feed, and tool grind are selected to meet finish requirements, the cut moves right along. This is what is meant by economical machine tool operation.

A L/S on the cross feed might be a safety feature but its implications that it makes blocks of time available for the operator to perform alternative tasks disturbs me. There are books available detailing the efficient use of machine tools including the shaper and planer.

You noobs and home shop machinists working in isolation have to learn that fine feed finishes are usually wasteful of productive time besides raising complications with tool failure during the cut. Learn to select tool geometry, DOC, feeds, and speeds that take each cut and operation quickly and efficiently to the size and finish you seek. Self teaching in the absense of a mentor can be difficult but it is possible especially in these days of the internet home shop fora. You can't do the same things the same way every time. You have to experiment and that may lead to ruined work and possibly collisions so use discretion.

Work safely but - well, do good work but don't take forever.

Bob Farr
03-08-2011, 08:41 PM
I like what you're doing Elninio. Thanks for sharing the circuit diagram. AMMCO avoided the whole cross feed crash scenario my removing the last few threads off the end of the feed screw. The nut would screw itself off the screw before the table crashed at either end.

Could the surface finish issue be a belt slipping?

03-08-2011, 08:52 PM
Look at Honeywell 14CE2 series limits for hermetically sealed type switches.
Also 1.2 amps is WAY too high for the input current for that SSR, it is in danger of a very short life, I am suprised if it lasted a day.
I would check the input resistance or max input current first.

03-08-2011, 09:50 PM
I like what you're doing Elninio. Thanks for sharing the circuit diagram. AMMCO avoided the whole cross feed crash scenario my removing the last few threads off the end of the feed screw. The nut would screw itself off the screw before the table crashed at either end.

Could the surface finish issue be a belt slipping?
Could be - the ram has a bit of resistance in it. I just never imagined it because the material should be consistent; I bet the belt slipping is the problem.

03-08-2011, 09:52 PM
Why would shaper cuts lead to enough time to accomplish anything meaningful

Imagine you have to face a 12" long piece, doing 0.005" per stroke. I don't have a surface grinder, the shaper will have to do. You're right, but this feed stop mechanism isn't a direct replacement for what you've said. It's similar to how surface grinders can be programmed to stop after 'x' number of canned cycles.

03-08-2011, 09:59 PM
One thing to sweat in a machine packing lots of mechanical inertia: chopping motor power doesn't safely stop it.

The point is not to stop in a corner, but to stop aproximately after it's done facing the part, but before reaching the limit of the table. Let's say at worst it takes two additional ram strokes before all inertia is transformed - that's about 0.010". This means if my switches were bolted to the ways like a micrometer stop in a lathe, it would be okay since the switches activate by more than that. In reality it takes less than a stroke's length to stop the ram after the power has been cut, and my switches will be held by magnets to the ways - this is since I don't want to lose the width of the switches worth of travel of the table.

Forrest Addy
03-08-2011, 10:32 PM
ElNino, I understand what's planned but consider: if you feed 0.005 pwer stroke the cut takes X minutes. If you feed 0.050 per stroke the cuts takes X/10 minutes. You need to learn broad nosing technique. It features a shallow depth of cut and a wide feed. If you go about it right applying coolant, cutting tool geometry, etc to suit the material yu don't need no effin' grinder.

A good broad nose tool finish looks like parallel satin ribbons even on mild steel. The finish if competently made has no feed marks perceptable to a questing fingernail. Finishes as fine as 16 microinch can be obtained with practice. The chips come off looking like tinsel or foil. The tool looks like a wide parting tool and the tool is offset backwards from the clapper box face. The cutting edge is flat and keen set accurately parallel to the surface being cut. A typical depth of cut is 0.005" for semi-finish and 0.001" for the final cut. Coolant ranges from dry for cast iron, WD40 for aluminum, to 15% soluable oil in water for steel. And variations.

This technique requires a little practice and the acquisition of "gooseneck" tools but it is applicable from very small shapers to very large planers. I've done it on 7" South Bend shaper with a 3/32" wide tool and on a 36 ft Nile planer with a 2" wide tool and everything in between.

What I have just presented is old lore lost with the disappearance of planer and shaper from the machinist's trade. Used to be experienced hands knew it, applied it when necessary, and never thought a thing about it.

03-08-2011, 10:36 PM
The problem is ... I only have 1/4" square toolbits ... for now. I'm always aiming for wider or deeper cuts. I was reading about the gooseneck tool on Kay's page just recently, I will have to try it; do you think it can be made, or is the tool holder made of the same material as car springs?

Forrest Addy
03-08-2011, 11:26 PM
ElNino, a gooseneck tool can be made of any steel. I've made many from plate. 1/4 square tool\ steel? I'll see if I can find a picture.

Here's one here:


but its a whopper of an OK holder used for larger machines. Maybe you can draw inspiration from its shape and proportions.

In your small shaper I think 3/4" x 3/8" width is about right. A hole and setscrew will hold the tool. IM me your eMail address and I'll send you a picture.

03-08-2011, 11:34 PM
Mr. Addy is right on here, even with a 1/4" tool bit, a good broad nose grind will use a great percentage of that width so you can feed over at least .050 per stroke. This assumes proper DOC (not much), that all roughing is already done, etc.. The smallest stroke on my G&E is .010, going all the way to .180.

03-08-2011, 11:38 PM
What do you think of the shearing tool - is this something that people use on larger machines? It doesn't hold the tool behind the face of the clapper, but it is used for finishing cuts: http://www.neme-s.org/shapers/columns/shaper_column_43.html

03-09-2011, 12:00 AM
I made this tool holder from plans on the groups.yahoo.com/metal_shapers group. There are plans posted by Art Volz (who has sadly passed away). Art had a lot of ideas and information available for people in the group page.
I also got a lot of good info from this guy (Artful Bodger) http://artfulbodger.net/docs/shaper/index.html
http://artfulbodger.net/docs/shaper/cutters/index.html and his cutter that Forrest is talking about. The tool is fantastic for finishing.
I do not think you need a gooseneck tool. The option is nice if you can find one but a tool like the one Art drew plans for works very well. The key is the tool must be as close to (or behind) the pivot point of the clapper box. The more the tool is in front of the clapper box the more chatter seem to get. Art's tool can be set facing forward or in reverse which moves the bit back closer to the pivot point of the clapper. The bit is just turned around 180d degrees. The bit in the holder is a large radius across the 1/4" bit.
I personally find that putting backrake on the tool adds to the chance of chatter in your cut. It is better to have a cleaving or shearing motion to one side. My preference, others may not agree.

I am sorry a few of the pictures are out of focus.