Cutting threads into seasoned oak

[Aden30mm]

I am just about to bring a new large bandsaw into my workshop. I have purchased a new machine trolley for it to sit on. I have prepared some oak sections (thickness 75mm X 45m) to fix into the base, for the machine to rest on. This is to secure the machine, spread the load of and to raise the height of the table to ease my back stress.

I would like to bore holes and tap (8mm) them to accept a bolt to secure the machine into the oak sections. Of note the tap hole will not secure into end grain, most will tap into quarter sawn board. I will also stabilise the tapped holes with CA glue, once dry run the tap down again to clean up the threads.

With the above in mind, can oak accept and allow for an 8mm thread to be cut allowing for a reasonable degree of integrity?

I would welcome some peer advice on this subject.

Kind regards

Aden30mm

(Yes stainless steel bolts will be used for securing)

 

[marcros]

could you not just use coach screws and not worry about tapping it?

 

[Aden30mm]

Marcros

No, that why I asked the question, Coach bolts would have been a solution, but not one that will work for me.

I seen some info from USA site that suggests that this is a stronger fix than normal screws.

 

[marcros]

i dont know the answer to your question, but...

if it is not suitable for tapping, you could put an insert into the oak and tap that. Ideally something that mechanically resists turning, rather than a dowel shape.

would something like http://www.specialisedfasteners.co.uk/c ... age-17.php work for you? (random search for threaded insert for timber)

 

[Dangermouse]

I should think an 8mm thread would be almost impossible to use in Oak, its too small to work. If you cant use coach bolts, have you thought of coach screws. These were used a lot in wood and are very good and strong. You would have to drill a pilot hole in oak first though.

 

[colinc]

I have tapped M6 into oak for some jig fixtures and it worked for me, but the pull out resistance would be low.

Can you not use M8 coach bolts (the round/square/cup head type) with the head recessed if necessary. The other aternative is to use Tee nuts, I just bought a load of them cheap off Ebay.

regards,

Colin

 

[Cheshirechappie]

The M8 thread is designed to be a good hold in metals. It would be too fine a thread for all but the hardest and most close-grained of woods, and would probably crumble out in oak even as it was being tapped. Threads specifically for wood are much coarser.

If at all possible, it would be more secure to drill a clearance hole right through the oak and whatever it's sitting on, and put a bolt through with the nut at top. Coachscrews would also be a good solution, and stainless ones are available (I think Screwfix do them).

 

[chipmunk]

I agree with Marcros, threaded nut inserts are the way to go. They work best in side rather than end-grain.

Axminster sell M8 insert nuts too.

HTH
Jon

 

[Spindle]

Hi

Have you considered using barrel nuts?

http://www.mossexpress.co.uk/cross-dowel-barrel-nuts

Regards Mick

 

[Aden30mm]

I would like to thank you all for your contributions to this thread (literately).

Today I made up a test block to see what stresses a threaded oak block could sustain. I cut a M10 thread through a 45mm oak block. Upon visual inspection the threads seemed well formed. I inserted a M10 bolt over the complete female threaded portion, and over a holdfast hole on my workbench, subjected the bolt to repeated blows with a 3lb hammer. Upon withdrawing the bolt no damaged to the oak threaded portion could be observed. However, I accept as Cheshirechappie indicated the threads could or would be subject to crumbling over a period of time, and machine vibration could also contribute to its demise.

I have found out that I have a gap of 20mm under the trolley, in which I should be able to lock the bolt off with a locknut, with the aid of a ratchet ring.

However with this foray into the use of tapping wood, I see many applications and agree with Colinc that the make up of jigs opens up new opportunities. I was especially surprised at the speed and accuracy of cutting the thread in wood. I may look in the future to drilling a clearance hole oversize and treating it with epoxy and then drill out the correct clearance and then tap the thread. Also, the use of other woods should produce stronger thread walls

Finally, the one issue of using threaded inserts in oak requires the use of stainless and a review on line of the cost of these item is eye watering.

Thanks again gents for your help.

Kind regards

Aden

 

[marcros]

Finally, the one issue of using threaded inserts in oak requires the use of stainless and a review on line of the cost of these item is eye watering.

Only to prevent staining- on a machine base, i would go with the cheapest!

 

[rxh]

I have found that ash, beech and yew can also be tapped using taps intended for metal bolts. Metric coarse or Whitworth threads work best. Ash can even be tapped in a hole in end grain. I made this three piece hill walking stick in ash several years ago and the threaded joints have survived many disconnections. The threaded studding is M10 (coarse) and is retained at one side by a brass rod inserted in a hole through stick and studding. The threads are kept lightly greased.