Fritz and Franz runner reference

[Carl Beckett]

I am wondering what other Minimax owners did for the runner that goes into the carriage slot.

My slot is tapered, coming to an edge at the top surface. This means high loads (and wear) if a straight runner is used. At the bottom of the slot it is wider (essentially it is a 'T-slot' used for sliding hold downs through it).

Had anyone tried using the sides of the lower portion of the slot? Some pros/cons to this.

Else how do you handle the high pressure points of being a psuedo sharp edge right at the top? (where location would be ideal)

I have an idea for a somewhat complicated design to account for wear, etc. But thinking some clever person here has already solved this.

[Carl Beckett]

As reference here are a couple pics of the slot. Its anodized aluminum. The reference surface comes to a point which seems prone to wear over time (and I want to have the runner wear not the carriage).

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[Erik Loza]

Could you machine the t-slot gibs out of hardwood (with threaded inserts) or a mechanical plastic like Delrin (acetal)? Then, zero wear to the extrusion.

Erik

[Carl Beckett]

Could you machine the t-slot gibs out of hardwood (with threaded inserts) or a mechanical plastic like Delrin (acetal)? Then, zero wear to the extrusion.

Erik

Yes the current runners are Oak. But the high pressure point means they wear fast and become less snug/precise.

More often than not I have the front half pushed up against the main fence, but not always.

[Erik Loza]

Yes the current runners are Oak. But the high pressure point means they wear fast and become less snug/precise.

Then Delrin is your answer.

Erik

[Dan Friedrichs]

I use HDPE plastic strips, which are soft enough that a wood screw can "swell" them a little. So my runners have screws through their bottom, and a little turn can create enough pressure to snug up any slack. HDPE is also very easy to plane with a sharp block plane, so it's pretty easy to sneak up on just the right initial thickness.

[Jim Becker]

Mine is pretty simple...I have a "runner" that's exactly the width of the slot on the wagon minus a proverbial. It's snug but slides easy. The "fixed" piece of the F&F I put up against the outrigger fence and use the cam clamp to hold it in place. The movable portion of the fixture slides easily and securely in the slot and has a handle on top that allows for necessary hand pressure for the operation.

[Rick Potter]

I simply made mine out of oak, contoured to fit the slot, and the top of it sits slightly below the face of the slider, to allow 'squeeze' room. To accommodate the corners on the top curve of the slot, I simply used a roundover bit to ease the edge of the insert.

These are made to 'lock' jigs onto the slider, my F&F jig just has a strip on the bottom to ride in the slot.

I made half a dozen extras for future use. Some are overall thinner than others, and I plan to experiment with putting a T bolt through from the bottom to enable using a star knob at the top on some. Most are full depth, and so far I simply thread the oak for knobs, but I plan to try inserts also. Ergo, lots of extras made for experimentation.

[Kevin Jenness]

What are the cons of sizing your runners to the width at the bottom of the slot? Is there any reason not to bevel the neck of the t to match the extrusion?

[Carl Beckett]

That was what I was trying to learn from others here - what reference plane do your runners come in contact with.

I can reference the width of the slot. But its a 'sharp' point - kinda like running against a knife edge. Delrin is pretty good, it might be worth a try. But there is no getting around the concentrated stresses on the edge. UHMW is not my favorite for something like this, too soft and would yield at the contact point.

I can try to match bevel - but that is going to push it down and unless very rigid is going to lose reference (and can I get the right bevel?). The roundover is a form of this (any side loads on that angle is going to want to squeeze it down - which might be ok.

I can try to run it against the bottom of the slot - where the straight walls are. This means nothing contacts on the plane where the F&F sits, but 'overhangs' about 3/8 until the reference surface. If it is not bolted down tight any rotation deflection is going to cause error. I am leaning towards this but wondered if others have considered this same thing.

The slot on this MM is not standard size, and is not standard shape. As pointed out it was made for T nuts, not as a miter slot. A lot of MM owners out there, somebody has tackled this.

[Kevin Jenness]

I can try to run it against the bottom of the slot - where the straight walls are. This means nothing contacts on the plane where the F&F sits, but 'overhangs' about 3/8 until the reference surface. If it is not bolted down tight any rotation deflection is going to cause error. I am leaning towards this but wondered if others have considered this same thing.


I don't really see the problem there except that the t-blocks have to be slid in from the end, which is inconvenient.

This may give you the heebie-jeebies, but you could file the slot edges to be less sharp - one side at a time with a gauge block to keep the sides parallel.

No matter what reference surface you use there has to be a little slop to allow for sliding.

[Keegan Shields]

Carl, are you overthinking this?

[Jim Becker]

What are the cons of sizing your runners to the width at the bottom of the slot? Is there any reason not to bevel the neck of the t to match the extrusion?
On many of the saw wagons, the slot is a tee-slot. I wouldn't want an F&F keyed to the tee, as it were, because I like to be able to instantly lift it off the wagon without having to slide it down to the end which with the way I use the slider would also require removing the small miter bar to get the F&F past it.

I do use oak runners keyed to the tee for fixtures that need to be locked down, however.

[Kevin Jenness]

On many of the saw wagons, the slot is a tee-slot. I wouldn't want an F&F keyed to the tee, as it were, because I like to be able to instantly lift it off the wagon without having to slide it down to the end .

I agree, but at least the wider slot walls shouldn't wear the runners as much.

[Kendall Scheier]

That was what I was trying to learn from others here - what reference plane do your runners come in contact with.

I can reference the width of the slot. But its a 'sharp' point - kinda like running against a knife edge. Delrin is pretty good, it might be worth a try. But there is no getting around the concentrated stresses on the edge. UHMW is not my favorite for something like this, too soft and would yield at the contact point.

I can try to match bevel - but that is going to push it down and unless very rigid is going to lose reference (and can I get the right bevel?). The roundover is a form of this (any side loads on that angle is going to want to squeeze it down - which might be ok.

I can try to run it against the bottom of the slot - where the straight walls are. This means nothing contacts on the plane where the F&F sits, but 'overhangs' about 3/8 until the reference surface. If it is not bolted down tight any rotation deflection is going to cause error. I am leaning towards this but wondered if others have considered this same thing.

The slot on this MM is not standard size, and is not standard shape. As pointed out it was made for T nuts, not as a miter slot. A lot of MM owners out there, somebody has tackled this.


I use HDPE that is milled just enough that I can drop it in from the top without any sideways movement. I have them more than full length so that the longer contact surface increases leverage and minimizes stress. I also killed up 4 sets so that when they eventually wear I have fresh sets waiting.

If this doesn’t appeal to you McMaster Carr sells threaded t-nuts that I keep several of inside the t-track. You could have a star knob screw into these t-nuts from the top locking the fritz and frans into place and placing the pressure on the under side of the t track and on top of the sliding table.

[Carl Beckett]

Agree about wanting to drop it in and out from the top

I do have the back piece of the jig with a runner that extends about 6” to give a longer reference

And most of the time the front piece is against the main fence

So it can have some slop and still function well, but not if you want to measure off the jig or set stops precisely.

But it has worn quickly to where slop with the runner. And looking at it more closely this time I see why, the sharp edge. Aluminum. Which will wear over time if I abuse it and have a slot that isn’t uniform over the length

Doesn’t sound like other MM owners have experienced a problem. As a straight material replacement I like the Delrin approach. I have one other idea I want to try first

[Brian Holcombe]

Bearing bronze will work also.

Another option would be to install fitted bars into the slots that are bored for pins.

[Jim Becker]

I agree, but at least the wider slot walls shouldn't wear the runners as much.
I guess that someone who is constantly using the fixture could theoretically wear the aluminum slot edges with a hardwood runner, but the risk is still pretty small. Using HPDE as someone else has mentioned could mitigate that. I think the flexibility of "drop on" is worth any small risk of wear, but others might feel differently.

[Erik Loza]

I’m actually kind of surpised HDPE works for this application. Would have thought that you’d pull the threads out but maybe because I’m mostly used to eccentric clamps and not smaller jigs?

Erik

[Carl Beckett]

Another option would be to install fitted bars into the slots that are bored for pins.

I am going to try something like this.

Even if the hardwood doesnt wear the aluminum, the hardwood itself wears too quickly. UHMW and HDPE are just too soft imo (I like it for many things but not this one). If I can not come up with a clever drop in design, will just replace with delrin and see how long it lasts this time.

This slot seems like it was just never intended as a miter slot.

[Wes Grass]

It's not a miter slot. It's a t slot for clamping the the giant miter gauge (fence) the machine came with.

I'd try delrin and see how it holds up.

I made t nuts for my Felder. The main one is about 11" long and has a precision bore to locate the fence pivot. I'm going to eventually install 2 more spaced evenly so fixtures can drop on and be dead square. Need to make a fixture to get them lined up with each other.

The Felder slot is extruded. The top face is machined flat, and the undersides of the t slot are not the same height on each side. Probably some twist in it too. It took some shimming to get my insert level side to side.

Here's a pic' of a data set collected some years back. Brian Lamb put this together from dim's people submitted.471365

[Carl Beckett]

It's not a miter slot. It's a t slot for clamping the the giant miter gauge (fence) the machine came with.

I'd try delrin and see how it holds up.

I made t nuts for my Felder. The main one is about 11" long and has a precision bore to locate the fence pivot. I'm going to eventually install 2 more spaced evenly so fixtures can drop on and be dead square. Need to make a fixture to get them lined up with each other.

The Felder slot is extruded. The top face is machined flat, and the undersides of the t slot are not the same height on each side. Probably some twist in it too. It took some shimming to get my insert level side to side.

Here's a pic' of a data set collected some years back. Brian Lamb put this together from dim's people submitted.471365

Yes. Except on the minimax that dimension 'B' is about 0.050" at most. This is the location feature if used as a miter slot.

[Carl Beckett]

I went ahead an made some 'T' bars that locate on the sides at the bottom of the channel. The 'D' surface in Wes image. I just leave it in the slot and lift the F&F off it (put a small bump in it to lock together when sliding. It did tighten things up, and there is not contact on the knife edge region now. We will see how it works over time. While I was at it I made some adjustable plates to accommodate different blades. Am going to see how this behaves over time.
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(shop setup, after moving, is coming along and it has been satisfying to take care of some things.)

[Dan Friedrichs]

That's clever! I like it!