Stripped thread advice please..

[Noods]

Hi..
Sadly after 4 months trying to get my DW745 Dewalt table saw fixed or replaced etc, This is still under extended warranty but they don’t answer calls or return calls and ignore e mails etc.. I’ve even requested the part from them but again, nothing..

Anyway no choice but to try and fix it myself..

It’s the blade height mechanism where the thread has stripped in the alloy housing. The m14 1.76 threaded rod still climbs the tread but it’s not enough of a thread to work without slipping under load..

I ask for your advice on how best to make a lasting repair?

Insert of some kind perhaps ? ( i’ve no experience with those )

A vertical cut along the length of the housing thread and then pinching the gap of the cut together to tighten the thread with a re tap of the original thread to the same m14 size to help.. ?

Centre of pic below shows the damaged thread..

Threaded rod below..

Many thanks ...

 

[Seadog]

I was about to say a Helicoil, but then noticed that it's a left-handed thread.

But they are available. It depends on the thread size. I would doubt that it's metric.

 

[AndersK]

If you can, drill it out and use Heli-coil or other inserts (Re-coil, V-coil etc)

 

[MetalMonkey]

You could try an inset, I would suggest something like an ez lok rather than a helicoil, as it will cope with the rod being constantly adjusted.

If there isn't enough meat your other alternatives could be things like filling it up with weld and re-tapping (probably wouldn't end well as these things are never great castings) or make a threaded bushing and press it in.
Depending on how the threaded rod works you could change it to a larger size and retap the hole.

However, if you have the clearance another option would be to make a new thread in a steel block or plate and attach it somehow in front or behind and just drill out the casting.

 

[Noods]

However, if you have the clearance another option would be to make a new thread in a steel block or plate and attach it somehow in front or behind and just drill out the casting.

That’s a good idea...

 

[Agroshield]

It is a common problem in the class of saws known as 'site saws' or 'contractor's saws'. It is known to happen in the Makita version as well.

Modern, non-woods are quite abrasive and a steel thread in a die-cast aluminium body is not a recipe for longevity.

The key to success will be the wall thickness surrounding the existing thread. If there is enough for a 16mm dia. bronze insert, held in by Loctite, the repair is easy.

If not, as stated above, you will have to create some material into which to put a thread. You will also have to pay good attention to the alignment and position of the new thread. You have the slider bar adjacent to it as a reference, so before you go removing material, make a jig so you can put the new thread in _exactly_ the same place as the old one. Be careful to make the new no higher than the old as I think the circlip on the thread touches the casting at max. blade height, so if you make it higher, you lose cut depth.

An outside alternative is to find some 12mm dia. LH threaded rod of the same pitch as the original and graft it into place of the 14mm existing. You seem to imply in your original post that the 14mm is 1.75mm pitch (that is non-standard). M12 standard pitch is 1.75mm, and is available in LH thread. That then gives you an additional 2mm in the casting for your insert. You could also change the pitch of the thread to right hand in both screw and nut (cheaper materials and tooling) - it will just make turning the blade-raising handle a little counter-intuitive.

 

[Pete.]

There's nothing wrong with the screw and the LH thread hasn't been torn out so I would say the tapped hole was too sloppy a fit to start with. It was only bearing on the thread tops and that's why it's eventually let go.

I'd make an insert, drill that out and glue the insert in it's place. It'll have thin walls but it should work all the same.

 

[Noods]

Dumb Question... Sorry..

If i’ve no nut to put the original threaded shaft to how can i tell if the original thread is metric or imperial?

I put manual callipers on it and it was a fraction below m14... i put a pitch gauge to it and it was 1.75... if that helps..

 

[Seadog]

Well, despite my early comment, that certainly does seem to be metric.

 

[Pete.]

Dumb Question... Sorry..

If i’ve no nut to put the original threaded shaft to how can i tell if the original thread is metric or imperial?

I put manual callipers on it and it was a fraction below m14... i put a pitch gauge to it and it was 1.75... if that helps..

Measure across ten thread pitches. Ten pitches would be 17.5mm. if it was 1.5 pitch it would be 15mm - easier to tell the difference than over one pitch.

1.75mm pitch works out to 14.5tpi so if it was imperial it would most likely be 14tpi, that would be 18.14mm over ten threads.

 

[Noods]

Measure across ten thread pitches. Ten pitches would be 17.5mm. if it was 1.5 pitch it would be 15mm - easier to tell the difference than over one pitch.

1.75mm pitch works out to 14.5tpi so if it was imperial it would most likely be 14tpi, that would be 18.14mm over ten threads.

Never too old to learn hey..
great i never knew that.. thanks muchly ...

 

[Noods]

Measure across ten thread pitches. Ten pitches would be 17.5mm. if it was 1.5 pitch it would be 15mm - easier to tell the difference than over one pitch.

1.75mm pitch works out to 14.5tpi so if it was imperial it would most likely be 14tpi, that would be 18.14mm over ten threads.

If i’ve done this correctly over 10 pitches this comes out at nearly 20mm or 19.75mm to be precise..

 

[RWD3M]

Then that'll be an M14 x 2.0 (LH)

 

[Noods]

Then that'll be an M14 x 2.0 (LH)

Yes that’s what i thought i’m glad you agreed with my maths..

I shall order a tap to suit then...

Thank you..

 

[Pete.]

£24 for a tap

14 X 2.0 METRIC HSS - L/H - Taps & Dies, Reamers, Milling Cutters, Tracy Tools

www.tracytools.com

I could probably single point that and save you the cost. What length does the insert need to be and is there enough room for a 16mm drill to make a hole for the sleeve?

A photo from a better angle would help.

 

[Agroshield]

I could probably single point that and save you the cost. What length does the insert need to be and is there enough room for a 16mm drill to make a hole for the sleeve?

Your reply above on gluing (maybe JB Weld) the insert in is a good idea, as you could thread it onto the screw first, which would help centralise it.

If that is the case, the hole might need to be bigger than 16mm to allow some space for the glue and for some inaccuracy in removing the old threads*. 16mm is probably the smallest practical dia. for the sleeve itself.

A small top hat on the sleeve might be good such that the pressure is against it when raising the blade. Again, JB Weld would do as a gap filler to save spot facing the bearing surface.

I think it is part 213 in the diagram here: https://www.partshopdirect.co.uk/dewalt-dw745-type-1-table-saw-spare-parts-s6695/ Part 79 is the M14 LH screw.

* the only thing you have as a reference surface is the minor dia. or tapping drill hole of a worn out thread.

 

[Noods]

Your a smashing bunch of lads.... and lassetts if there are some on here too ...

 

[Noods]

I shall take it apart in the morning and get a better picture of what we have so to speak...

One issue which worries me a bit is drilling it out as i’ve only a pillar drill which goes to 13mm unless i can get a 13mm bit with a 16mm drill head..? but i doubt the accuracy will be great..

Might be better if i pay one of you guys to make it and i send you the components to work off..

 

[Brad93]

If you can take the components off do that then it can be mounted on a mill and bored out accurately.

 

[Brad93]

A bronze nut with an odd spray of PTFE dry lube would outlast the saw