Advice on beech lamp production - CNC needed?

[Woodmonkey]

I have been asked by a friend if I could produce a smallish run (150) of these lamps in beech.

Sorry about the watermark but I think you can still get the idea.
Here's a side elevation:

In order to accept the light fitting, 3 different diameter holes need to be bored, 40mm, 60mm and then a very shallow (1.5mm) 70mm. I was thinking the 40 & 60mm holes could be drilled on the pillar drill with forster bits, but I'm scratching my head about the 70mm, this needs to be pretty accurate so that the fitting sits flush with the edge of the lamp. Any ideas? Could possibly be done on the lathe but I think it would be very time consuming to make 150 like this... I know it doesn't seem like much of a fun job but as I said it's for a friend so want to help if I can. Would a cnc be able to cut that inside profile that deep?
Thanks in advance.
WM

 

[CHJ]

Without CNC, looking at it as an engineering problem I would batch bore the holes on a vertical milling machine with pre-set boring heads, having set up suitable stops and jigging.

One or two I would do on a lathe.

Hope the lighting units are LED not Halogen.

 

[Chrispy]

you could do this with an inverted router fitted with a bearing guided rebate cutter set to give a 5mm rebate. note end bearing running on the 60mm hole.

 

[Woodmonkey]

Thanks guys. Chas, I don't have a milling machine, how does that differ from a drill press? I'm assuming they're led lights, I haven't seen them.
Crispy, that's a good idea. A quick Google doesn't come up with a 5mm rebate cutter, is it something you know exists?

 

[Spindle]

Hi

If you keep the blank section square you can fit it to a four jaw chuck in the lathe, bore the 60 and 40 mm recess' using forstner bits and turn the 70mm recess using a scraper. Remove from lathe and form light attachment holes on pillar drill, finally saw off the angled section.

If you mark the blanks to allow accurate re-fitting there's no reason not to drill all the 60mm holes followed by the 40mm ones to save bit changing.

Regards Mick

 

[Woodmonkey]

That would work too Mick, although the chuck jaws would mark the wood...

 

[CHJ]

If you go for drilling clearance holes with Forstener bits, then it would pay to start all the 60mm holes for a few mm, this will allow for 'second bite' bit alignment.
Then drill 40mm hole, you have centre location for drill bit already from 60mm bit.
Then return to complete 60mm hole using starter recess to align and a much reduced material to remove.

 

[Spindle]

Hi

Easy enough to protect the corners with short lengths of brass / aluminium angle or strips of wood, the chuck only needs to barely hold the wood all forces from the forstner bits will tend to secure the blank and the forces from scraping the recess will be minimal.

Regards Mick

 

[Spindle]

Hi

I've never tried Chas' suggestion and in view of this I would first ensure the 60mm bit stayed acceptably concentric without the benefit of it's central pilot on a couple of lamps before going ahead with the whole batch.

Regards Mick

 

[CHJ]

I drill out deep vases in stages this way to reduce cutting loads and speed things up this way to remove bulk of material and as long ad Bit has good alignment to start it does not wander significantly.

 

[Spindle]

Good info - Thanks Chas

Regards Mick

 

[Chrispy]

Crispy, that's a good idea. A quick Google doesn't come up with a 5mm rebate cutter, is it something you know exists?

yes I found one in the trend catalogue you select the right bearing to suit rebate size.

 

[Woodmonkey]

Thanks everyone good info. Can anyone recommend decent forstner bits that would handle that size of hole on end grain beech? I've heard the famag ones are good, they stock them in Rutlands in 40&60mm (surprisingly as rutlands are more often a bit more cheap and cheerful)

 

[CHJ]

.... Chas, I don't have a milling machine, how does that differ from a drill press? ....

Sorry forgot that question, just for information, milling machine and boring heads as opposed to Forstener bits in a pillar drill.
More power, speedier cutting and easier repeatable accuracy.

 

[ColeyS1]

I'd start by drilling the first hole in some 12mm ish mdf. Then measure and glue some batten onto the mdf to form the square( size of your timber) I've found even with a nice sharp bit and stops set up on a piller drill there's still movement for the point of the forstner bit to drift of with the point following the softest route. With your mdf jig you can slip it on the end of the blank and it should prevent it from drifting off.

Sent from my GT-I9300 using Tapatalk

 

[Brentingby]

For the quantity you are planning to make and the potential time investment handling the blocks repeatedly, maybe it would be worth looking into have a custom ground cutter made that could cut the stepped hole in one go. It could be run in the pillar drill or on the lathe. Even if the cutter only made the two larger holes and had a 40mm pilot, you'd reduce the number of steps required to make these.

 

[Woodmonkey]

Interesting idea, sounds expensive? Do you know a company that does that?

 

[Brentingby]

I don't but maybe someone else has experience in that line. I don't have a Forstner bit as large as the recess but maybe one could be modified by a machinist to reduce the diameter enough to cut the recess and the next larger hole?

 

[Andy RV]

Do you have a beefy pillar drill because you'll need one!?

As already mentioned by others I'd forstner the 40mm and 60mm bores then machine the 70mm on a router table by mounting the work piece on jig / base that a guide bush can follow.

 

[Woodmonkey]

Hi Andy
No I have a crappy pillar drill, but I have a beefy lathe! I've done a test piece holding with cole jaws and it worked fine, using some famag Forstner bits. I will do the narrow recess with a square scraper on the lathe as suggested by Mick I think. The 2 forstner bits cost over £100 but I priced it into the job.