Welding Table Hole Size Question

[Allan 888]

Hi, kinda new to steelwork and learning a lot from this forum! after a few projects fabricated on my rough garage floor I've decided my next project is a welding table. Decided to go for a 12.5mm thick 1000mm x 2000mm plate top with grid of holes plasma cut to accept clamps etc.

All the commercially available tables seem to settle on 16mm holes at 50mm centres, I'm going to go with 100mm centres as I figure that will be enough for me but the question is on hole size will a 16mm plasma cut hole let an M16 bolt through or is there not enough clearance, (all the drawings of M16 bolts have the thread diameter and bolt shank as 16mm exact). any advise very much welcome.

Thanks
Allan

 

[Robert.]

Drill a 16.5 mm hole ...doubts and problems solved .

 

[hotponyshoes]

I would be tempted to get the holes cut undersized and ream out.
You need a snug fit for the pegs to work properly and if you are using it to jig up the accuracy is kind of useful.
If doing it yourself it might be better to mag drill them in the first place.
If paying someone else it might be better to spend the extra on laser.

If sending out for cutting then you may as well get the holes done at 50mm but if you are doing it yourself any hole pattern would do, you can just drill them as you need them. Personally I would just dedicate an afternoon to it and do them all in one go. You will fill up any spare time in the future by making attachments for it!

 

[tom2207]

Drill a 16.5 mm hole ...doubts and problems solved .

drill a 15.8 hole and ream them for a pin ,, who cares about bolts , most of the time too slow.

 

[Robert.]

drill a 15.8 hole and ream them for a pin ,, who cares about bolts , most of the time too slow.

Or just tack it all down to the bench

 

[tom2207]

Or just tack it all down to the bench

you need quality mdf for that to work well though ....

 

[Ped]

Reaming a plasma cut hole is just about impossible. They're never round enough and the cut surface is very hard. You're better off just mag drilling it all from scratch.

 

[tom2207]

Reaming a plasma cut hole is just about impossible. They're never round enough and the cut surface is very hard. You're better off just mag drilling it all from scratch.

that would do ,, if you have a mag drill of course.

 

[Ped]

One day hire for a mag drill is under £40. 16mm rotabroach £15.

You might get the sheet laser cut for that price but depends where you are and who you know

 

[Sean]

I always thought the "Nominal" size of a bolt was the size of the hole it went through?
16mm hole, slightly less on the major diameter of the thread.

 

[Allan 888]

Thanks for the replies folks, I'll be getting the plate from my local steel supplier with free delivery, they have a plasma cutter so was going to get them to do the holes, I live out in the sticks so a one day hire of a magdrill would cost me an additional £30 and 4 hours in fuel and time!. its really just for home made F clamps clamps and not for really accurate dogs so will get it cut at 16mm as I suspect M16 bolts are slightly under 16mm if not I can ream the holes out (or use 5/8" bolts on the ends of the F clamps).
Cheers
Allan

 

[James1979]

I plasma cut mine. Did a tab and slot thing and cut the holes. It worked well. A mate wanted one but for his I mag drilled it 16mm at 100 centres.
Loads quicker and more accurate and as has been said you can ream them if needs be

Two things I’d say I have learnt doing mine:
1, if you’re buying accessories, do your research. A lot of the American ones use 5/8 pins not 16mm.
2, use round bar not bolts if making your own accessories. Oh and the shank on M16 coach bolts is far less than 16mm! Ask me how I know....

edit: we crossed posts, Alan, sorry!

 

[tom2207]

If you intend to use standard clamps , laser oval holes , ,, jobs done.

big enough to slot clamps in and move about to suit , have a play on a bit of ply wood , make sure vise grips work in the holes you plan too .

 

[Allan 888]

Thanks All for the comments, definitely some food for thought, I might just go down the mag drill route after all as I have more control over it.
Allan

 

[hotponyshoes]

Just make a bracket with a couple of 16mm pegs that bolts to the mag drill.

Very carefully mark out and drill the first couple of holes then use the bracket to position the rest.
You will have the job done in a couple of hours.