T slot bits and t track

[LinuxRandal]

I have a project to play around with. It is either going to require quite a bit of T track, or some T slots. I'd prefer the bit, due to cost, but I always see two different bits. What they don't say is what size bolt they allow to fit.

Is one for 1/4 20 and one for a 5/16 18 bolt or what is the differences? (one bolt only verses one bolt or nut)


Thanks

[eezlock]

t slot bits

Linux, they did say the size .....(1) 1/4" x 20 threads per inch (2) 5/16"x 18 threads per inch. The threads per inch is the difference in how coarse or fine the threads of the bolt or nut to be used is measued by. Twenty(20) threads per inch is a finer thread than 18 threads per inch an so on. The other measurement 1/4" or 5/16" is the diameter of the bolt/ screw. Hope this helps. eezlock

[LinuxRandal]

Linux, they did say the size .....(1) 1/4" x 20 threads per inch (2) 5/16"x 18 threads per inch. The threads per inch is the difference in how coarse or fine the threads of the bolt or nut to be used is measued by. Twenty(20) threads per inch is a finer thread than 18 threads per inch an so on. The other measurement 1/4" or 5/16" is the diameter of the bolt/ screw. Hope this helps. eezlock

I know about bolts, but some of the metal T track I've seen won't take 5/16 x 18 (unless a toilet bolt). Some T track can use regular bolts. So I am trying to avoid the t track completely and use a T slot cutter like the two that Holbren sells.

What is the difference in the T slot cutters?

[LarryG]

LR, I don't own any of these bits, but I've been looking at them. The mfr will typically supply a small diameter, large diameter, and cutter depth/height.

The small diameter would be the topmost slot, that the bolt shank slides along. The large diameter would be the semi-concealed slot that the bolt head slides along, and the cutter depth would be the height of this same slot.

I think you just have to work out what you need using these values, by comparing them to whatever bolt size and type you want to use.

EDIT: Okay, looking at the specs on Holbren's site, the leftmost of the two bits has a large dia of 1-1/16" (seems pretty wide?), a small diameter of 3/8" (would accept a 5/16" bolt; 3/8" would be tight), and then an "A" and "B" dimension. I interpret "A" as the depth of the slot the bolt head slides in -- 5/16" -- and "B" as the maximum distance from the top surface to the top of the slot cut by "A" -- 1/2".

[ragswl4]

LR, I don't own any of these bits, but I've been looking at them. The mfr will typically supply a small diameter, large diameter, and cutter depth/height.

The small diameter would be the topmost slot, that the bolt shank slides along. The large diameter would be the semi-concealed slot that the bolt head slides along, and the cutter depth would be the height of this same slot.

I think you just have to work out what you need using these values, by comparing them to whatever bolt size and type you want to use.

Exactly right. Also measure the head of the bolt from flat side to flat side, not point to point. The flat to flat size should be the same size as the larger slot or just slightly smaller so the bolt will slide in the slot. Also the height of the bolt head is critical for the bolt to slide in the slot.

The bits that I saw on Holbren.com are the whiteside bits, unless I missed others. While I am a great fan of whiteside bits and own many of them, unless you think you are going to make a huge amount of slots, you might want to look at other sites for less expensive bits. I think the t-slot router bits can be had for around $20.

You may want to shoot Holbren.com an email on the specs. They have always responded quickly with good info.

[LCHIEN]

LR, I don't own any of these bits, but I've been looking at them. The mfr will typically supply a small diameter, large diameter, and cutter depth/height.

The small diameter would be the topmost slot, that the bolt shank slides along. The large diameter would be the semi-concealed slot that the bolt head slides along, and the cutter depth would be the height of this same slot.

I think you just have to work out what you need using these values, by comparing them to whatever bolt size and type you want to use.

Unfortunately, I never see T-slot bits described with a bolt type they are to fit. So here's how you check their numbers and pick the right one:

What Larry is saying is right, the Router bit mfr gives three critical dimensions. Small diameter, Large Dia. and cutter depth (depth of the larg diameter.)

Lets say you are going to use 1/4-20 bolts, the 20 is immaterial (no. of theards per inch) but the shank is 1/4" and the hex head is 7/16th across, so you want a small diameter slightly greater than .250 and a large diameter slightly greater than 7/16 (.4375") but less than .488". (that lets the head slip in but not rotate).

For 5/16-18 bolts, the corresponding numbers are .3125 and bigger than .500" but less than .557"

The cutter height needs to be large enough to pass the height of the hex head, or at least do it in a couple of passes. These are .163" and .211", respectively for 1/4 and 5/16 hex head cap bolts.

There's a lot of undrecutting going on, some people recommend to extend the life of your bit which is weak at the thin point (base of the "T") that you first rout with a 1/4" straight bit to clear most of the groove and part of the "T" top and then the T-slot bit has much less material to remove, reducing the stress on the bit.

Most all T-Track I've seen takes 1/4" bolts, They can't take both becasue a 1/4" bolt has a .432" head that is .488 acorss the points so it will spin in a track made for 5/16" which uses heads .500 across the flats.

Most T-track fits in 3/4" dados, track for 5/16" bolts with .500 hex heads would leave only about .11" wall thickness, maybe that's why you don't see it often.

Both bits at Holbren and the three bits at MLCS are all 1" or more on the large diameter.

http://www.oldham-usa.com/DBScripts/.../tslotwall.asp
the 1204TS is the closest, but it only gives the flute length, not the large dia. height (thus making a liar out of me)

Most of the T-slot cutters are too big. You can also look at Keyhole cutters but they tend to be too small.
Its hard to find T-slot cutters to fit 1/4-20 or 5/16-18 bolts.

[LarryG]

Here is an example of the less costly bits that Rags mentioned -- and from Lee Valley, of all places. Included is a diagram that should help explain the various dimensions. MLCS has bits for about the same price, too.

Which leads to a problem. It appears that some mfrs list the two depth dimensions independently and you add them together (Whiteside/Holbren), but others give a total slot depth, and the actual slot depth that receives the bolt head is subtracted from that (Lee Valley, MLCS). So you have to be careful about what you're comparing.

[gsmittle]

I bought a T-slot bit the other day, and also in the case was a bit intended for the slots in a slotwall type arrangement.

It could be that the larger bit is meant for the slotwall and the smaller for T-slots.

I picked up the smaller, but I haven't used it yet. I'll report back when I do.

g.

[scorrpio]

Just a thought:
Regular bolt + grinder = bolt that should fit into about any T-track...

[LCHIEN]

Just a thought:
Regular bolt + grinder = bolt that should fit into about any T-track...

Good point, provided slot is smaller than the head to start with.
No amount of grinding is going to make a 1/4" hex head cap screw keep from turning in a 1/2" wide slot.

[gwyneth]

I guess the bit issue should go in the ultimate T-track reference.

The amount of needless time, energy and stress woodworkers spend on t-track specs and measurements is astounding--I bet just the members here have spent a man-year, collectively.

[LarryG]

No amount of grinding is going to make a 1/4" hex head cap screw keep from turning in a 1/2" wide slot.

This goes to why, despite the ready availability of 1/4-20 hex head bolts, I much prefer T-bolts.

A 1/4-20 hex head is 7/16" across the flats (i.e., that's the wrench size) yet only a tick more than a half inch measured across the points. That means there's a VERY fine line between a slot that just wide enough for the 7/16" head to slide freely yet still keep the ~1/2" "diameter" of the head from spinning uselessly in the slot -- especially in a soft material like MDF, which is prone to wallowing out over time.

The elongated head of a T-bolt doesn't have this problem. I also find that the rounded ends slide along the slot much more smoothly, with less catching and digging in, than do the pointed corners of a hex head.

[LCHIEN]

This goes to why, despite the ready availability of 1/4-20 hex head bolts, I much prefer T-bolts.

A 1/4-20 hex head is 7/16" across the flats (i.e., that's the wrench size) yet only a tick more than a half inch measured across the points. That means there's a VERY fine line between a slot that just wide enough for the 7/16" head to slide freely yet still keep the ~1/2" "diameter" of the head from spinning uselessly in the slot -- especially in a soft material like MDF, which is prone to wallowing out over time.

The elongated head of a T-bolt doesn't have this problem. I also find that the rounded ends slide along the slot much more smoothly, with less catching and digging in, than do the pointed corners of a hex head.

Larry, my fastener reference book says the width of a 1/4" hex head bolt across the points is .488 min to .505 max so chances are it will spin given a little push in a .5" slot (which also has tolerances.).

[cgallery]

I use these t-slot bits from Rockler:

http://www.rockler.com/product.cfm?p...ilter=t%2Dslot

Along with these t-slot bolts (also from Rockler):

http://www.rockler.com/product.cfm?p...ilter=t%2Dslot

The bit requires that I make a first pass w/ a 3/8" straight bit. Then the Rockler bit (actually made by Amana, I believe) cuts the major (5/8") diameter.

I feel like I kinda got lucky on this one as I bought the bit about four or so years ago and never used it until two years ago (I didn't have a router w/ a 1/2" collet).

When i finally could use it and had built a router table, I found all sorts of things that it worked great for.

In hindsight, I'm very happy it uses the toilet-style bolts because they have less of a tendency to spin in the slot. The elongated head works great in wood slots.

I'm also happy that I picked a system that I can buy components for at my local Rockler store. Yeah, their prices are higher than some of the stuff out there. But they're local, they have stock, and they have a nice selection of accessories.

I've built a number of projects that use t-slots and haven't wanted a metal track at all. The Rockler/Amana bit and bolts work that well.

[LinuxRandal]

Actually part of what I am doing was trying to avoid having to get the slotwall bits. I figure a T slot should be strong enough for my purposes (and changeable, like wrench racks and such for the garage wall).

I'd also like to do it on a few items instead of buying T track (and having to visit the infamous T track thread). I realize I won't be able to hold up as much weight as the slotwall bits, but I think the T slot bits would bring me more value (not just one behind a bench project).

I do like the T slot bolts, but they DO add up, so I've been trying to go with the regular bolts (mostly hold downs, feather boards, jigs, etc.)

I did learn the hard way about the Rockler track. It came through locally, at a damaged freight store, and was sold for $9.99 a tube (before a relatives discount). So we bought the last five.