Cutting clean 85mm holes through plywood

[Johnnybach]

I want to cut 2 rows, each row having 5 holes of 85mm dia., through a piece of plywood, which may be either 9mm or 12mm thick – I haven’t decided yet.

I want the holes to be clean cut, with no tendency for the bottom layer of ply to peel away when cutting..

What would be the best tool to use and the best way of achieving this, please?

I’m not a skilled wood-worker, more of an odd-jobber, I suppose! I have a small pillar drill, and various electric and hand drills, but no cutters of anywhere near the size I need so will have to buy these, hence my question.

What I am planning to make is a number of trays (the plywood forms the bottom of each), in which I can store or carry filled flowerpots. When the pots are removed, the idea is that the trays can be easily stacked. I have the design (in my head!) but not the knowledge of how to best cut the holes! I’d be grateful for any advice, please? I hope my explanation is understandable!

 

[Spindle]

Hi

Good quality hole saw used in a pillar drill - stack the bases together with a sacrificial board on the bottom to eliminate tear out.

Regards Mick

 

[wellywood]

The only way I can think of with the tools you have to hand would be a Forstner or sawtooth drill bit. At this size (85mm) you would need to use the pillar drill and to ensure a clean entry/exit cut, drill until the bit centre point exits the underside then flip the wood and use the exit hole to centre the bit and drill the other way.

 

[Johnnybach]

Thanks both - that was quick!

Hi Mick, I'm a bit concerned about the size of the teeth on hole saws. The ones that I've seen look as though they would tear the plywood layers rather than cut. Can you buy hole saws with various tpi, as I think a fine tooth saw would be best, and, if so, can you suggest a size, please? I had thought of tightly clamping a piece of sacrificial wood underneath, so will probably go with that.

Hi wellywood, Thanks - I've seen, on the Internet, when searching for saws, etc., a Forstner bit but know nothing about them They seem to have a peculiar system of cutting "teeth", if I can call them that. Can you tell me more about them, please? Are they designed specifically for wood?

Sorry to both of you as I'm showing my ignorance, here!

 

[wellywood]

Johnny, the forstner bit was designed to cut very clean holes (originally at an oblique angle into the butt of a rifle stock, I believe). The original forstner didn't have a central tooth and so gave a clean bottom to the hole which isn't such a consideration for you as you're going right through the wood. The sawtooth bit does the same thing but has a central point for starting.
Mick's suggestion of a hole saw is also good if you put some sacrificial wood under the ply to reduce tear out and would probably be cheaper and easier to source at the size you're looking at.

 

[Master Carpenter]

Router would be the cleanest method

 

[Normancb]

An 85mm holesaw will be a lot cheaper than a Forsner, but you need to run the drill very slowly and clear the sawdust very frequently - the saw teeth are small and will choke up with dust every few revolutions, causing the saw to heat and burn.

Forstner will be cleaner and much faster but needs quite a bit of power as you destroy all the wood in the hole. Again, run slowly to avoid burning. Neither is suitable for a hand drill really - you need a pillar drill with a low speed.

The more expensive Forstner type bits are much better performers than the el-cheapo ones with TiN coatings, but they do cost and may not be worth it for a one off.

I've done that size hole in the past by making a template and routing them.

 

[Phil Pascoe]

AO blade in a good jigsaw - you might have an odd bump to take out with abrasive, but so what. I take it you're not building a piece of Chippendale. Not the best neccessarily, but maybe the cheapest and most practical?

 

[Spindle]

Hi Johnnybach

I based my response on the information given, in particular the existing tooling which you state is available. Others may have missed some details.

A hole saw will perform the task required and if fed slowly into the work, (it will need to be any way to avoid stalling the pillar drill), have little or no tear out. Worst case, you can sandwich your bases between two sacrificial boards but it shouldn't be necessary.

http://www.starrett.co.uk/shop/holesaws ... _hole_saw/

83 or 86 mm

An 85mm forstner bit will require far more drive power than is available from a basic pillar drill - it will probably also cost significantly more than your power drill!! It's a non starter unless you want to upscale your tooling.

http://www.amazon.co.uk/C10800085-Colt- ... B00IF7S1OM

The router option is good but again involves tooling you don't yet have.

Regards Mick

 

[Stu_2]

Would also recommend using a router. Perfect for this type of task. If you don't have one, now would be a good time to add to your tool collection

Doesn't need to be an expensive one. Something like a used Trend T5 would be a good start, or something of a similar size/power. You could make a very inexpensive jig from a piece of 9mm ply, and you'd achieve a much nicer result than doing battle with a hole saw, free-hand. If you wanted to be really posh, you could use a Trend CRB, but they're about £70.

Let me know if you want a pic of ply template.

Cheers
Stu

Sent from my Nexus 7 using Tapatalk

 

[Johnnybach]

Hi all,

Thanks for your suggestions! I now have a good idea what a Forstner bit is, and how to use it. I can see why it would need more power than other methods.

The hole saw sounds the best for me because I have no need to go fast – I’m not in a hurry and can take greater care – and, using one sacrificial board will solve the problem of breaking the bottom layer of ply.

I’ve never used a router so it’s all new to me! I suppose that I’d better get educated and see exactly how to use them, then I might change my mind.

I’ve only just remembered - I have a relative living close by who is brilliant at producing woodwork that I can only dream of. He has a large workshop full of all manner of woodworking tools – hand and power. He produces ornate boxes and display cabinets of all types – all different.

I suppose, I could ask him – he’d almost certainly do it for me but, rather childishly, I suppose, I’d prefer to do it myself – there’d be more self-satisfaction in doing that. I might ask him, however, to show me how to use a router.

Stru - you mentioned a pic of a ply template - I'm unsure what you mean so thanks for your offer and. if you don't mind, please, tell me more!

Thanks again, everyone. I will digest all that has been said and learn.

 

[Stu_2]

Stru - you mentioned a pic of a ply template - I'm unsure what you mean so thanks for your offer and. if you don't mind, please, tell me more!

No worries. I'll post something up later this evening.

Cheers
Stu

Sent from my Nexus 7 using Tapatalk

 

[Billy Flitch]

Johnnybach sounds like a expansive bit would do that job no problem normally the bit extends to 3" but I`ve used mine up to 3 3/4". Let the spur cut the wood before the bit starts to remove the waist drill it till the worm (that's the pointy end with the thread on it) just starts to come through the other side, turn the board around put the worm in the hole it made and let the spur cut the wood chances are it will just pop that piece straight out.

There is one on E-bay at the moment for four pounds with a brace if you don't want them after the job just put it back on E-bay, with a bit of luck it may cost you just the post.

http://www.ebay.co.uk/itm/Vintage-brace ... 4ad522a186

 

[Johnnybach]

Hi Billy Flitch,

You've solved a different problem for me! About 2 years ago, we decided to move and downsize so I had to give away many tools that I hadn't used for many years and the brace and bit had to go - I think I last used the brace out fifty years ago (that gives my age away!). In the event we moved but didn't down-size - what a pity. I couldn't remember (old-age again!) what the expansive bit was called so could never found it on the internet.

I'll certainly have a look at ebay - might even buy it - it could be the one that that I gave away!

Thanks again, Billy

 

[Benchwayze]

Just make the 'apertures' square and of appropriate size; like a milk crate. It's only for carrying pots around the garden?

 

[Stu_2]

Apologies for the delay in posting this.

Here's a pic of the ply template. I use this for cutting circular inspection panels and inserts. You would only need one pivot hole for your requirement. The large hole is for the router guide bush.

Cheers
Stu

 

[Johnnybach]

Hello Benchwayze, Cutting square holes would, surely, take more time and the pots wouldn't fit as well but thanks for the suggestion.

Anyway, apologies to all for the delay in coming back but other things demanded my attention!

Thanks for all your replies and I know what I will do now, if and when I decide to make the trays.

I went to the local Garden centre the other day, however, and there, on the side, were many plastic trays, used by the Centre, and, as far as they were concerned, scrap.

They were exactly what I was looking for though, as I said, in plastic. However, as there seems to be an unlimited amount of free, second-hand trays, doing exactly what I want, I shall put the making of my more expensive ones on the back burner.

I’m sure you’ll all understand - I like the price! Thanks for your help, though, and I assure you, it’s not wasted.

 

[Benchwayze]

Hi John.

I wasn't envisaging 'cutting' square holes. I was thinking along the lines of making a crate to fit the pots.
But I can be different at times! :lol:

Cheers

John

 

[Johnnybach]

Hi John.

I wasn't envisaging 'cutting' square holes. I was thinking along the lines of making a crate to fit the pots.
But I can be different at times! :lol:

Cheers

John

Ah! It all becomes clear, now! Sort of a milk crate, if you'll excuse the simplification. I imagined the trouble I would have had to go through in drilling four holes, one at each corner of, perhaps, ten square holes, and, then, jig-sawing, horizontally and vertically ,to join them up to remove the waste. I'm, probably, the only person who can mark out a perfectly straight line around a square piece of wood, and saw along that line, taking the utmost care ---- and produce a perfect three-dimensional curve! It has to be seen to be believed!

Thanks John! It gave me a chortle!