T-Slots or peg holes?

Discussion about Tooling and Fixtures. End Mills, Router Bits, Hold Downs, Fixtures, Etc.
jbc
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T-Slots or peg holes?

Post by jbc » Sun Nov 08, 2015 6:09 pm

First off I don't have a great hold-down system on my SO3.
I have seen nice setups with t-slots and some with peg holes and vices.

Here are what I see (in my limited experience) are the differences in T-slot and peg board.

T-slot
More involved and more expensive than drilling holes for a peg board solution (need more tools to route slots, and or slide aluminum runners into slots $$).
Hold down clamps apply pressure downward to hold the material in place (not always but most clamp down on the material).
T-slots allow a quick way to move the holding clamps.
Clamps apply pressure down on the table but most of the force when cutting the material is coming in laterally= material shifting = wasted material / time.

Peg Board (I drilled 1/4" holes in a piece of MDF spaced 2" apart in both X and Y axis to form a grid. I put 1/4" dowels in the holes)
I'll place the dowels on all four sides of the material. The material is placed up against the dowels on two sides. I use a wedge and a small hammer to tap on the wedge between the other pegs and the material to hold the material in place. It is snug!
Here is finished job;
pegs and wedges.JPG
pegs and wedges.JPG (143.49 KiB) Viewed 3013 times


The pegs keep the material from shifting laterally. It does not help if the material gets pulled upwards but most of the force is applied from a side.

I would like to use the pegs on two sides (as shown) and then use a rockler type clamp http://www.rockler.com/auto-lock-t-track-clamp to push on the other two sides instead of wedges of course. (that clamp uses the t-slot but can be modified to work with my system)

This seems easier to make than a t-slot hold down system.
I like the holding power of the pegs and have only had an issue when pushing my machine to an extreme it couldn't quite accomplish (testing SO3 limits). Lots of chatter helped pull the material off of the bed. I pushed it to the extreme. If it didn't get pulled up off of the bed the poor quality of the edges would have made me go slower anyway so I was happy with my set up.

Can anyone who has used a peg system and then moved to and liked a t-slot system more, explain why you went through the trouble of making the t-slot board?

I am planning on having an aluminum bed made with peg holes matching the hole pattern of my local hardware store. Then I can cut a piece of the 1/8" thick peg board to fit on top of the aluminum bed as a waste board. Easy / cheap to replace while having the strength to resist the lateral forces when cutting.

Thoughts on my ramblings?
jbc
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cvoinescu
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Re: T-Slots or peg holes?

Post by cvoinescu » Mon Nov 09, 2015 3:22 am

Looks good to me, and it's indeed easy to make and economical. The only problem with lateral holding in general is that you can't leave narrow margins when you cut, because the force would bend the stock once the cut is all the way through and squeeze it around the bit. If you always leave plenty of stock around what you're cutting, this is not a problem; it's just that it's less versatile than clamps that apply pressure from the top.
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jbc
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Re: T-Slots or peg holes?

Post by jbc » Mon Nov 09, 2015 4:13 am

When clamping down from above you would need to avoid that area right? Unless you were working the edges and secured the piece through the middle.
Do you have a pic of your setup so I can better understand your approach cvoinescu?
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Re: T-Slots or peg holes?

Post by cvoinescu » Mon Nov 09, 2015 11:44 am

My approach is low-tech. I drill through the stock and screw it to the MDF wasteboard. If the part has holes, I can mill the holes first, then put screws in a couple of them, then mill the profile without the need for tabs.

But you're right, of course: if you use hold-down clamps, you need room for them, and you need to make sure the machine clears them. But a clamp needs only a few millimeters to hold, and that doesn't have to be all around the stock. You can mill a 100 mm circle out of a 110 mm square, for instance, by holding down the corners. If you can avoid through cuts near the edge of the stock, though, your method works great.

It doesn't have to be a T-slot table to use clamps. My plan was for a flat surface with threaded inserts (T-nuts, really) on a rectangular grid, but since the wood screws work so well...
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Gadgetman!
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Re: T-Slots or peg holes?

Post by Gadgetman! » Mon Nov 09, 2015 9:51 pm

Insertion nuts are nice...
But...

On my first version of my Wasteboard, I used 361 T-nuts. (19x19 grid. I have a 1000x1000 machine) It takes a while to hammer in all those nuts.
On the current version I used nuts you need to screw in. (E-nut, I think. Similar to D-nuts, but without the lip, and just plain M8 threads on the inside. No Hex-shape at the end.)
Having to thread them onto a bolt, then screw them into the wood and unscrewing the bolt... took some time.

So, yeah, I can see why T-slot is tempting. At least on larger builds.

As for wasteboard material...
I used 22mm thick plywood on my recent rebuild. That gives me somewhere between 5 and 10mm of top surface that can be flattened down 0.5mm at a time when it gets too 'chewed up'

I'm going to change over from using Steel M8 wingbolts, to Nylon M8 soon. Just in case of runaway machine.
(A good endmill is worth more than a few M8 bolts)
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Re: T-Slots or peg holes?

Post by cvoinescu » Mon Nov 09, 2015 9:58 pm

There's a market need for a CNC hammer, it seems.
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Re: T-Slots or peg holes?

Post by WillAdams » Mon Nov 09, 2015 10:15 pm

The quantity of T-nuts required for a gridded array was why I went w/ the radial Phi arrangement I ultimately settled on.

I’ve been using the nylon machine screws and they’ve worked well, and are inexpensive enough as to be used in sacrificial holding techniques.

The one change I would make is to use smaller hardware, M3 or #6-32, something which will fit Ina drill hole made by a typical size of endmill.
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Re: T-Slots or peg holes?

Post by ijv » Sat Nov 14, 2015 2:12 am

This sort of clamp looks like a good option instead of wedges.

http://www.thingiverse.com/thing:522615

jbc
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Re: T-Slots or peg holes?

Post by jbc » Sat Nov 14, 2015 3:46 pm

Thanks ijv,
I was looking for those earlier but couldn't find them.
Once I get my printer repaired and printing I'll try these.
Thanks.
Jbc
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Re: T-Slots or peg holes?

Post by jbc » Sun Nov 15, 2015 8:24 pm

WillAdams wrote:The quantity of T-nuts required for a gridded array was why I went w/ the radial Phi arrangement I ultimately settled on.
Do you have a picture Will?
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