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).

IMG_4358.jpgIMG_4359.jpg

[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.