Stripped T bolt

[Robin GrahamParticipant @robingraham42208]

[Robin GrahamParticipant @robingraham42208]

I somehow stripped the thread on one of the two T-bolts which hold the topslide on my lathe:

God knows how, I'm not a beefy bloke I and don't swing on the spanner, but it happened..

The quickest and easiest way to make a replacement given the equipment and materiaI I have to hand would be to mill, drill and tap (M10x1.5) the head of the T-nut and screw a bit of HT studding inito it. Question is – would this work? The head bit is only 5.5 mm thick, so 4 (OK ,3.67) threads engaged. I read somewhere that you only need 3 threads, but i'm not convinced!

Regards, Robin

[frank brownParticipant @frankbrown22225]

I would buy a suitable HT bolt and take an angle grinder to it.

Frank

[Chris Evans 6Participant @chrisevans6]

It is a quick and easy job to pull the cross slide off and make a correct tee bolt. Use EN24T if you have any or a Tensile bolt. The original most likely gave up from wear and tear, my lathe only has two bolts to hold the top slide on and I have added two tapped holes in the cross slide and made "L" shaped clamps to give a bit of extra security.

[Thor 🇳🇴Participant @thor]

My experience is like yours Robert, some of these bolts are made of soft material. I have made new bolts using HT bolts that I turn and mill, screwcut threads may not be as strong as rolled but I have had no problems.

Thor

[Anonymous]

When one of my topslide T-bolt threads got too worn I made a couple of new ones from EN3:

So far they've been fine. As far as I am aware the stripped bolt was original, in which case it was over 30 years old. I can't really see the need for fancy steel or HT bolts.

Andrew

[Tim StevensParticipant @timstevens64731]

I would invest in a pair of new quality nuts while you are in there, too. Some of the nuts supplied with tooling are hardly fit to throw at the dog. ie: hole too big, not square to the thread, too few turns, and never mind which grade of coke tin they were melted down from.

Regards, Tim.

[Robin GrahamParticipant @robingraham42208]

Thanks for the advice. I was hoping that someone might say that there's no need for HT, and as Andrew has said it, and I have EN3 to hand, I have made up a new pair of bolts from that. They are actually more solid than the originals which had always felt a bit squishy between 'nipping up' and tight.

Tim, the nuts are indeed rubbish, and will be replaced.

Thanks again, Robin.

[HopperParticipant @hopper]

It looks like the nut was only just on the original T bolt. I would make the new ones a few threads longer, if there is clearance space to do so.

[Jon GibbsParticipant @jongibbs59756]

I hope I'm not teaching my Grandma here but…

My old ML7 had t-bolts and nuts but I got fed up of swarf and chips getting embedded in the exposed threads and between the nut and the thread when undone and retightened. This led to the threads getting worn and stripped very quickly.

So I swapped to a t-nut and bolt from the top which naturally stays much cleaner because the exposed thread is naturally better protected.

Not sure if this is helpful

Jon

[Neil WyattModerator @neilwyatt]

It may be that the t-bolts are of a material chosen so they strip before you break a t-slot?

Neil

[Howard LewisParticipant @howardlewis46836]

Generally, I am sceptical about oriental materials. They do seem to have a bit of a blind spot over fit and concentricity of threads.

The M8 capscrews that secured my Top Slide were pretty soft and soon replaced by some decent ones, which have lasted well enough still to be in use after nearly ten years, and likely for many more.

I am more likely to be the first to fail!

The suggestion to modify a High Tensile Bolt / Setscrew is a good one, but use good quality nuts with them.

If you can make a "jury" rig to use the lathe, make a neat, and consistent, job of the new bolts by turning, rather than an angle grinder, to maximise the material in the head, (particularly thickness, you don't want it flexing when tightened, and then slackening off; that could be expensive at worst, embarrassing at least).

Howard

[Clive HartlandParticipant @clivehartland94829]

This is not about a T bolt, but T nuts, I have often wondered if they are sintered metal?

Clive

[Enough!Participant @enough]

Posted by Jon Gibbs on 20/04/2016 16:10:54:

My old ML7 had t-bolts and nuts but I got fed up of swarf and chips getting embedded in the exposed threads and between the nut and the thread when undone and retightened. This led to the threads getting worn and stripped very quickly.

So I swapped to a t-nut and bolt from the top which naturally stays much cleaner because the exposed thread is naturally better protected.

Odd coincidence, Jon.

My old ML7 came with bolts from the top and t-nuts for the top slide (it's how the Myford manual shows them). It's always been a nuisance point for me because, at some point in its life someone used a slightly too-long bolt (more likely forgot the washer) and the bolt penetrated the bottom of the t-slot damaging it.

This has always prevented the t-nut sliding freely in the slot and no (reasonable) amount of stoning has ever cured it. Since I've had both cross and top-slides stripped down for the last day or two to dowel the gibs. I just decided to make a pair of t-bolts (with more clearance) so that the penetration problem wouldn't happen again.

[Jon GibbsParticipant @jongibbs59756]

Posted by Bandersnatch on 20/04/2016 23:10:36:

Odd coincidence, Jon.

My old ML7 came with bolts from the top and t-nuts for the top slide (it's how the Myford manual shows them). It's always been a nuisance point for me because, at some point in its life someone used a slightly too-long bolt (more likely forgot the washer) and the bolt penetrated the bottom of the t-slot damaging it.

This has always prevented the t-nut sliding freely in the slot and no (reasonable) amount of stoning has ever cured it. Since I've had both cross and top-slides stripped down for the last day or two to dowel the gibs. I just decided to make a pair of t-bolts (with more clearance) so that the penetration problem wouldn't happen again.

Just shows that we're all different.

…but perhaps after you've had your t-bolts a while you might see the problem.

To be fair though it's only the inboard one that is the swarf & chip magnet and then it's worse again when it's on the headstock side. I think that the older models with red knobs and rods on the half-nuts have t-bolts and nuts, whereas the cast levers have bolts and t-nuts – see http://www.lathes.co.uk/myford-ml7/index.html

Jon

Edited By Jon Gibbs on 20/04/2016 23:43:18

[Enough!Participant @enough]

Posted by Jon Gibbs on 20/04/2016 23:35:14:

…but perhaps after you've had your t-bolts a while you might see the problem.

 

Very possible. In fact, that whole area of the top-slide circular slots gets pretty swarf-laden and on the relatively rare occasions when I loosen the bolts to rotate it (I don't do much screw-cutting or tapering) I usually vacuum out the whole thing first ….. which will hopefully clear the t-bolt threads too.

I think, based on your comments, I'll make the t-bolts like the clamping system used on the mill …. a t-nut and a stud with a deformed thread in the t-nut to preclude penetration. That way, if the studs do get fouled (!) up, I can easily swap in another piece of studding in situ.

On top of that and because of the swarf problem, I've been doodling in CAD looking at 3D-printing a pair of snap-on covers for this area. I could probably make them enclose the t-bolts as well.

 

Edited By Bandersnatch on 21/04/2016 01:05:32

[Robin GrahamParticipant @robingraham42208]

Posted by Jon Gibbs on 20/04/2016 16:10:54:

I hope I'm not teaching my Grandma here but…

My old ML7 had t-bolts and nuts but I got fed up of swarf and chips getting embedded in the exposed threads and between the nut and the thread when undone and retightened. This led to the threads getting worn and stripped very quickly.

So I swapped to a t-nut and bolt from the top which naturally stays much cleaner because the exposed thread is naturally better protected.

Not sure if this is helpful

Jon

Not teaching your granny at all Jon – I'm a rank amateur! However this had occurred to me, but there isn't enough room for a shoulder on the T nut if I stick to the M10 thread on the original, so it would just be a plate. Given that the plate can't be more than 5.5mm thick, and it's necessary to mangle the thread at the bottom to avoid the penetration problem described by Bandersnatch, it wouldn't work for this machine.

Neil, I'd like to believe that the bolts were cunningly designed to fail before the T-slot, but given that this a generic 12×36 Chinese lathe I suspect that would be overly optimistic. It's more likely they are made from recycled bottle tops I think. The design of the cross slide / topslide is actually such that the top of the X-slide T slot is (in principle) held in compression, so presumably that reduces the risk of breaking it.

I ended up jury-rigging the slide much as Howard suggested so I could turn new bolts from EN3, which seem fine so far.

Thanks for further suggestions, Robin.

 

PS – does this software allow multiple quotes? I successfully quoted Jon's post, but when I clicked on the 'quote' field on the next message, assuming it would be inserted at the cursor position in this reply, my previous typing was discarded and I had to begin anew. Which was annoying!

R

 

Edited By Robin Graham on 22/04/2016 22:09:57

[Enough!Participant @enough]

Posted by Robin Graham on 22/04/2016 22:08:30:

PS – does this software allow multiple quotes?

 

 

 

I'd have said "No" 'cause I've never been able to make it happen, but I saw a post here a few days ago where someone did it. Might have been Neil ….. but then, Neil possesses the magic wand and can do anything.

Sometimes it's better to use in-line replies which needs multiple quotes – or the ability to cleanly split a single quote.

Edited By Bandersnatch on 22/04/2016 23:16:20

[Rod NeepParticipant @rodneep80388]

To get multiple quotes: Open two windows of the same thread…..

Start your reply to one of them quoting as usual….

Now go into the second window and start a reply with the other quote, but go no further, other than highlighting and copying the quote…. then go back to your real reply and paste it in below your previous reply….. finish typing and then hit the "add posting" button. The end result is two quotes and your typing between and below them.

Finally go back to the second window and just close it without actually replying.

[Neil WyattModerator @neilwyatt]

I just cut and paste if I want more than one quote.

For what it's worth many forums do the 'discard' trick with multiple quotes.

Neil

[VicParticipant @vic]

When the monkey metal T bolts gave way on my lathe I just turned down a couple of nuts for the slot and use socket screws from above. I've found a T handle ball hex driver is quicker to use than a spanner.

[Enough!Participant @enough]

T-Bolt – erstwhile stainless-steel carriage-bolt after 5 -10 minutes on the mill (could just as easily be 5 – 10 minutes with vice and file)

T-Nut – simple turning with a couple of flats added. Or add a piece of threaded rod and turn it into a T-Bolt (locktite the thread or munge the bottom thread of the nut).

(Both for my ML-7 top-slide).

Edited By Bandersnatch on 23/04/2016 22:36:19

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