First project on a PM25, tee slot nuts for my vise

[WobblyHand]

Nothing earth shattering, but a first step for me. The vise that I got with the mill had gigantic tee-bolts. The bolts were much larger than the slots. The keys for the vise are too large for my 12mm slots. Fortunately PM has slipped in some tee-bolts that would fit my machine. I used them to hold down the vise.

Apparently I was 20 minutes late for ordering a tie down kit at PM that I could use directly. They still don't have the kit in stock. However, I do have a 1/2" clamp kit that I had bought for my drill press a while ago. Decided to re-purpose the kit for the mill. So first thing to do is to mill down a couple of tee slot nuts, so I can get rid of the tee bolts.

Did a poor mans tram and decided that the existing tram was good enough for doing some tee slot nuts, hey they're not big, right? Mounted the vise and trammed it to the table. Got it to about 0.0002 over the fixed vise jaw. Not terrible for a first time at it. Had a little trouble sorting out fine feed, but kind of blundered my way through that. Milled off the edges with a coarse 4 flute end mill. Didn't try to hog anything out, just took a pass of a few thousandths to get an idea of what speeds would work. The finish was pretty nice, better than I expected. Buoyed by that success, I decided to side mill the slot width. I intended to not take off any of the underside of the tee, but took a little of the black oxide off. Guess the end mill was a tad low.

Found out why there is a need for edge finders. Despite that, things came out well enough. Took a few passes at it, and eventually I had two tee slot nuts that fit my table. They are wide enough that they scraped out some of the cosmoline I missed in the corners of the tee slots. But they do move smoothly along the slots. Eventually I'll do 6 more. They won't take very long, as I've mostly figured out what to do. After the tee slot nuts are done, I'll tackle the vise keys, that looks like an interesting minor project.

May not seem like much, but I pretty pleased with this.

 

[benmychree]

For most accessory mounting on my mill tables, I prefer T bolts with heavy pattern nuts and heavy washers under them, I think they are more convenient than T nuts, studs and hex nuts.

 

[Dhal22]

Awesome, tools to make tools to work with your other tools. What do we actually need the tools for?

 

[WobblyHand]

Well, learned my first, and sadly not the last, expensive lesson. I must have machined these 2 tee slot nuts from my set. They machined easily. Cheap set, umm soft nuts. I then proceeded to try some "real" tee slot nuts that I had bought from McMaster. Yep, dulled the cobalt roughing mill. The end of the end mill is all dull now. Guess the better quality tee slot nuts are the hardened variety.

1) Would a carbide end mill cut the hardened tee slot nuts?
2) Can the cobalt roughing mill be sharpened? It's the very end that got dull, I was only trying to cut 0.0025 off.
3) How does one test the material in advance, so that one can avoid this sort of thing?

 

[T Bredehoft]

Yes, your end ill can be sharpened, look for a professional (Google) . Yes, carbide would cut it. Yes, eventually, it too would dull.

Test it with a file. if the file will cut it . so will high speed cutters, if the file wont' cut it, carbide will.

 

[darkzero]

If using studs with the t-nuts you made, it's highly recommended that you swedge the bottom of the threads. If not swedged while tightening the studs can turn & crack the the table.

I always swedge the ones I make unless they will only be used for one specific application with bolts sized to length. Here some that I just made a week ago.

Teco t-nuts & the ones I've gotten from Mcmaster are much harder than Chinese t-nuts. Was still able to machine them with carbide but the Chinese hardened t-nuts were easier to machine.

As said a general file will give you an idea but you can also use hardness files. Tsubosan hardness files are handy to have around. They also rebranded by Fowler, SPI, TTC, etc.

 

[Mitch Alsup]

Also note: Most T-slot nuts are not threaded all the way through. You want the stud to lock into the t-slot-nut and not push on the bottom of the t-slot. If the stud pushes on the bottom of the t-slot you can chip the top of the table.

 

[WobblyHand]

The t-slot nuts I've been using are not threaded all the way through. (In my reading it became obvious to my why that was a good thing.) Was trying to machine the the existing t-slot nuts to fit my slots. 1/2" t-slot nuts are 0.5 - 0.75 mm too wide. The height of the nuts is fine.

Dimension E and B need to be reduced to fit my table. C and D are ok. Just kind of miffed that my new 3/8" roughing end mill had such a short life. Oh well. I'll have a couple of carbide roughing end mills by the end of the week. Then it's back to work on this.

 

[mrproduxn]

I just got notified that my new pm 728v-t will ship out of Pittsburgh in a couple of days. And they still are sold out of the 12 mm t-nut kits. They are plentiful on ebay. Just make sure they have a good 30c+ rockwell hardness. Too important to buy softer ones. I just sold my HFT mini and let the guy take my 12 mm set. Not sure why I did that. Was hoping they would be in stock at pm by now.

 

[mikey]

I think this is a fun project but wanted to point out that one option to making t-nuts is to buy them. Northwestern Tools makes really high quality clamping kits, among other things, and their prices are reasonable for what you get. For example, you can get 20 each high quality 12mm T-nuts for about $33.00 from them. Not sure what your end mills cost but a single Niagara roughing end mill might cost what this set costs and you are likely to need those nuts down the road.

I bought a stud/T-nut clamping set from them to fit my rotary table slots and, being impressed, I wrote it up on HM. If you contact the seller, you will find him to be responsive and accommodating to us hobby guys. I even had him make a special run of clamps I wanted and got them for a really nice price. I have been impressed by Northwestern Tools and while making your own stuff is fun, sometimes its good to consider just buying what you need so you can get on with it.