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View Full Version : Reducing T-slot Bolt Shank (without a lathe)



Guncraft
01-13-2016, 07:11 PM
Hello all!

I purchased some new 5/8" t-slot bolts to hold down my Kurt vise from Fastenal. I ordered the 5/8" bolt as I have 5/8" slots in my mill table. The problem I have with the bolts is evident below - the shank is 11/16 and the threaded area is 5/8"...

http://www.practicalmachinist.com/vb/attachments/f38/159869d1452730125t-reducing-t-slot-bolt-shank-without-lathe-20160113_185902_resized.jpg

If I owned a lathe I would reduce the shank diameter a bit, however I do not own one. So, I am left to reduce the shank size another way. I could file them I guess, but that seems to be a time consuming venture. What would you do?

Thank you!

Andy

Mr-Mike
01-13-2016, 07:26 PM
If the thread diameter fits the slot (apparently does), I would mount the bolt in the mill collet (perhaps a soft collet) and a cutting tool and holder or clamp in a vise on the table (vis-a-vis a vertical lathe per se) - but I have little experience :)

Doc Nickel
01-13-2016, 08:02 PM
Easy, use the mill itself.

Hold the threaded portion of the bolt in a 5/8" collet (assuming you have such a thing) and mount a lathe tool to the mill table, using whatever blocks, clamps and baling wire you have on hand.

Then it's just a vertical lathe. Move the table in and out for depth of cut, and crank the quill down to feed.

You'll have to take light cuts, as the collet probably won't hold well on a the threads, but a few passes of .005"-.006" at a time shouldn't take too long.

Doc.

brian Rupnow
01-13-2016, 08:21 PM
You're not concerned with accuracy nor concentricity here. Haven't you got an angle grinder?

PStechPaul
01-13-2016, 08:57 PM
If your T-slots measure 5/8", the bolt should be 1/2"-13:

http://enginuitysystems.com/pix/tools/T-Bolt_Dimensions_800.png

http://enginuitysystems.com/pix/tools/T-Slot_Dimensions_800.png

The throat for a 1/2" bolt actually should be 0.562" and not 0.625", but the next larger 5/8" bolt calls for a 0.688" throat. But if the square head of your T-bolt fits the slots, maybe the throats of your table slots are undersize. You should be able to clamp the bolt heads in a vise and mill flats on the sides of the bolt to fit the slots.

Guncraft
01-13-2016, 10:25 PM
Gents,

I must say that I greatly appreciate your patience with what seems like very simple questions. I just have an odd need for as much "right" information as I can get prior to doing something. I asked the same question on Practical Machinist and one man asked if I had a sign out front of my house that said, "Dumbass Lives Here"... I would like to loosen the man's teeth, but instead I forgave him and expressed my disappointment.

Thank you all again.

Andy

Guncraft
01-13-2016, 10:27 PM
I have 1/2" hardware already. I bought a swivel base for my Kurt vise and the Kurt swivel base came with 5/8" bots to connect the vise to the base. I was just upgrading the size of the bolts that will hold the base to the table. I figured if Kurt sells the base with 5/8" hardware, maybe it was OK to upgrade the 1/2" stuff... maybe not.

Andy

Doc Nickel
01-14-2016, 01:32 AM
I asked the same question on Practical Machinist[...]

-You have to remember these are two entirely different boards. This one, as the name and magazine implies, is for home shop machinists. On the other hand, the owner of PM wants to keep that site "professional", and attract professional machinists.

Neither one is "better" than the other, it's simply two different sides of the same coin.

However, a fair number of "professional" machinists, I've found, have little tolerance of the home-shop types. In some cases it's the annoyance they they did a seven-year apprenticeship and spent years in college to get a document that officially declares them to be a Machinist, and then they see some guy with a cheap import desktop machine in his basement who also calls himself a machinist.

In other cases, it's simply the typical rivalry you'll see in any undertaking. Ford vs. Chevy, Mac vs. PC, F1 vs. NASCAR. The guy that runs a thirty-foot-long machine that has metal removal rates measured in tons per hour looks down on the guy that's just building a little brass steam engine. You see it everywhere.

Don't let it bother you. PM has quite a few helpful people (I'm one of them :D ) but like any other board- even this one- it has a few loudmouths and jerks. Don't let the jerks spoil it for you. They don't speak for everyone.

Doc.

lakeside53
01-14-2016, 01:37 AM
I have 1/2" hardware already. I bought a swivel base for my Kurt vise and the Kurt swivel base came with 5/8" bots to connect the vise to the base. I was just upgrading the size of the bolts that will hold the base to the table. I figured if Kurt sells the base with 5/8" hardware, maybe it was OK to upgrade the 1/2" stuff... maybe not.

Andy

Just mill (hey, use the mill!) two opposing SIDES of the shank, you do not need to make it "circular" - just two loose flats. I have two Kurt's on my mill with t-bolts done this way, and I believe are "factory"

martik
01-14-2016, 02:17 AM
How can one live in indiana and not own a lathe! :)

Richard P Wilson
01-14-2016, 03:32 AM
Whats wrong with a file? All you need to do is file 2 flats on the plain section so its a free fit in the sides of the slot. Does the head fit? If not, same treatment. Its done in far less than the time to set up in the mill, indeed less time than you've spent asking the question and reading the answers. It doesn't need precision machine work. Personally, I'd have bought 1/2" bolts for a 5/8" slot.

Guncraft
01-14-2016, 03:36 AM
I already have 1/2" bolts and t-nuts. The dissimilarity f 5/8 and 1/2 hardware together got to me... No other reason that a want and not a need.

Andy

Mr-Mike
01-14-2016, 09:50 AM
Just mill (hey, use the mill!) two opposing SIDES of the shank, you do not need to make it "circular" - just two loose flats. I have two Kurt's on my mill with t-bolts done this way, and I believe are "factory"


Whats wrong with a file? All you need to do is file 2 flats on the plain section so its a free fit in the sides of the slot. Does the head fit? If not, same treatment. Its done in far less than the time to set up in the mill, indeed less time than you've spent asking the question and reading the answers. It doesn't need precision machine work. Personally, I'd have bought 1/2" bolts for a 5/8" slot.

how would one tighten the bolt?

Mr-Mike
01-14-2016, 09:53 AM
Easy, use the mill itself.

Hold the threaded portion of the bolt in a 5/8" collet (assuming you have such a thing) and mount a lathe tool to the mill table, using whatever blocks, clamps and baling wire you have on hand.

Then it's just a vertical lathe. Move the table in and out for depth of cut, and crank the quill down to feed.

You'll have to take light cuts, as the collet probably won't hold well on a the threads, but a few passes of .005"-.006" at a time shouldn't take too long.

Doc.

is that not that exactly what I said? Not wanting to be offensive, nor do I care about recognition, but I feel like I am in the twilight zone... Am I missing something?

Mr-Mike
01-14-2016, 10:01 AM
how would one tighten the bolt?

Nevermind LOL.

This is good, would also prevent driving the bolt into the table.

Richard P Wilson
01-14-2016, 11:12 AM
how would one tighten the bolt?

Sorry, don't understand the question. The OP has got tee bolts, so the head of the bolt slides in the large portion of the tee slot but can't turn, nut on bolt, tighten with spanner, or am I misunderstanding?

Mr-Mike
01-14-2016, 11:29 AM
Sorry, don't understand the question. The OP has got tee bolts, so the head of the bolt slides in the large portion of the tee slot but can't turn, nut on bolt, tighten with spanner, or am I misunderstanding?

Just a lapse in logic on my part - heck I am still new to this world :) As soon as I said that I caught my error. I mean, obviously the nut turns on the bolt not vice versa, and I knew that but my t-slot gear has t-nuts, not t-bolts. Wasn't paying attention, that's all.

Mike Amick
01-14-2016, 01:59 PM
Actually I think Mr-Mike is right. If you file the flats on the shafts and they are tighter fitting than the head, you
chance buggering up the slot. In other words you want the bolt head to be the restricter for the tightening
operation rather than the shaft of the bolt.

Just saying it maybe should have been mentioned.

fifth edit .. grin : I do understand Mr-Mike was thinking the bolt turned, but his question was inadvertently valid.

Mr-Mike
01-14-2016, 03:22 PM
fifth edit .. grin : I do understand Mr-Mike was thinking the bolt turned, but his question was inadvertently valid.

Yea, I screw up in reverse a lot - which is a good thing right?

:)

Mr-Mike
01-14-2016, 03:27 PM
Actually I think Mr-Mike is right. If you file the flats on the shafts and they are tighter fitting than the head, you
chance buggering up the slot. In other words you want the bolt head to be the restricter for the tightening
operation rather than the shaft of the bolt.

Just saying it maybe should have been mentioned.

fifth edit .. grin : I do understand Mr-Mike was thinking the bolt turned, but his question was inadvertently valid.

And by the way, awesome insight! <Learn something every day> Go with turning the bolt in the mill collet.

On a similar note, I have gotten into the habit of buying T-Nuts one size up and grinding them down slightly. Fit and strength is much better, but I have a mini mill after all.

mosedawg56
01-14-2016, 07:43 PM
The previous owner of my Hardinge TM dealt with this same dilemma by making bushings that fit the 3/8-16 T-nut bolts and in the much larger bolt bosses on the vise. Of course he had a lathe though so this probably won't help in this situation. I just wanted to throw it into the discussion.

Doozer
01-14-2016, 09:18 PM
Yer' all wrong.
A bolt is a screw, until it has a nut.;)

--Doozer

outlawspeeder
01-15-2016, 12:38 AM
You are doing it wrong. You just need a larger mill.... hahaha

You should have seen the me after the wrong size for the 7B Atlas.

tmc_31
01-15-2016, 12:24 PM
Consider this type of Tee bolt. If you have other things fixtured to your mill table such as a rotary table and a say maybe a tail stock, you can fixture your vise between them without removing them first. I have found myself in this pickle on occasion.

Tim

http://i663.photobucket.com/albums/uu351/tmc_31/IMDIN261_zpssp8g5zwt.png (http://s663.photobucket.com/user/tmc_31/media/IMDIN261_zpssp8g5zwt.png.html)

Royldean
01-15-2016, 12:59 PM
Consider this type of Tee bolt. If you have other things fixtured to your mill table such as a rotary table and a say maybe a tail stock, you can fixture your vise between them without removing them first. I have found myself in this pickle on occasion.


Looks like a pain to tighten, though....

softtail
01-15-2016, 01:54 PM
File held in bench vise, bolt held in hand drill, grind away. -ST-

tmc_31
01-16-2016, 12:05 AM
Looks like a pain to tighten, though....

Not so much, the head is wide enough that it won't completely in the T-slot

tmarks11
01-16-2016, 11:33 AM
If I owned a lathe I would reduce the shank diameter a bit, however I do not own one. So, I am left to reduce the shank size another way...

Stop looking for work arounds and excuses not to own a lather, and buy one... You know you need one. :D

Black_Moons
01-16-2016, 01:50 PM
You're not concerned with accuracy nor concentricity here. Haven't you got an angle grinder?

This exactly. My friends keep asking me to mill that, lathe this.
The number of jobs they have come up with that actually need a mill/lathe and not the angle grinder, I can count on one hand.

Sure, I could use the mill/lathe for job X, but by time Iv got it secured and dialed in, I could have ground it with an angle grinder and test fitted it 10 times to make sure it fits just as perfectly as I could have gotten it with the mill/lathe.

Not to mention, sometimes its just easier to do with an angle grinder, being able to hold the part in your hand while shaping a light curve is so much easier then bolting stuff to the rotary table and dialing it in, or trying to do curves etch-a-sketch style using both feed wheels. (You can KINDA do it, if you put one axis on power feed, but good luck doing more then 1 pass with similar material removal, or a finishing pass)

Black_Moons
01-16-2016, 01:54 PM
File held in bench vise, bolt held in hand drill, grind away. -ST-

Bad idea, you'll wear out bits of the file

Better idea is bolt held in drill press, file in hand (or mini belt sander, or angle grinder). move file back and forth if using a file. Iv done this to reduce the head of SHCS to fit in countersinks for other screws.

That said, he does not need a round shank because its a T bolt in a T slot, so he can put the bolt in a vise, then just hit it with an angle grinder.

Or secure the angle grinder in a big vise with soft jaws and hold the bolt to the grinding wheel. Or use a bench grinder if hes not a cheapass like me. (Iv bought and returned at least 3 bench grinders as none of them where smooth enough to use)

lakeside53
01-16-2016, 01:58 PM
Way to much misunderstanding of the actual problem here... All the OP has to do is take off a CHORD 1/32 inch at max depth on the two opposing sides of his round oversize stem and it fits, just like mine came from the Kurt... I can see I'll have to take and post a picture! ;)

A file, angle driver or even and end mill (god forbid!) will do this in less time than it takes to read this thread.

Mr Fixit
01-16-2016, 02:17 PM
Guncraft,
Just watch out with the file idea the bolts may be hardened a bit and the file might get damaged. A bench grinder and a drill was my first thought Chuck up the bolt in the drill if it fits and give it a go. The other is a hand grinder as others have said clamp the base in the vice and grind around the shank.
Let us know what you end up doing and how it goes.

TX
Mr Fixit for the family
Chris :)

KarlH
01-28-2016, 04:53 PM
Gents,

"Dumbass Lives Here"...

Andy

During my training, there was a sign posted in almost every room that said "Don't be afraid to ask 'Dumb Questions.' They are a whole lot easier to deal with than 'Dumb Mistakes!' "

I have been asking "Dumb Questions" ever since.

Mr-Mike
01-28-2016, 05:08 PM
During my training, there was a sign posted in almost every room that said "Don't be afraid to ask 'Dumb Questions.' They are a whole lot easier to deal with than 'Dumb Mistakes!' "

I have been asking "Dumb Questions" ever since.

Ya but how many answers did you need? :D