trouble drilling 1" hole

[ericc]

Hi. I am having trouble drilling a 1" hole in mild steel. This is a weight plate from a fitness machine, so it is just junk. It is soft enough to file, chisel, and make spiral chips, and it will be used for a swage block. The drill press is a large Jet. I am not sure of the model, but the chuck is huge and says MT-5. The drill is set for 150 RPM and the bit is new. It worked for one hole, then jams and the belt slips. Soluble coolant is being used. The hole was pre-drilled for 1/2". Is the step up too large? I have a big hand drill which should be able to handle it if rigged up as an old man. This one will not slip. I used a combination wrench to yank on the drill press tensioner, so this is bordering on abuse.

 

[John Hasler]

Hi. I am having trouble drilling a 1" hole in mild steel. This is a weight plate from a fitness machine, so it is just junk. It is soft enough to file, chisel, and make spiral chips, and it will be used for a swage block. The drill press is a large Jet. I am not sure of the model, but the chuck is huge and says MT-5. The drill is set for 150 RPM and the bit is new. It worked for one hole, then jams and the belt slips. Soluble coolant is being used. The hole was pre-drilled for 1/2". Is the step up too large? I have a big hand drill which should be able to handle it if rigged up as an old man. This one will not slip. I used a combination wrench to yank on the drill press tensioner, so this is bordering on abuse.

How large a Jet? 1" is a lot of hole. My 2HP triple-belt Avey isn't rated for that, though it will actually do it with no problem with no pre-drill. Also, that sort of junk steel can vary from one spot to another.

I'd add a 3/4" step.

 

[JimDawson]

Dull the cutting edge of the bit, like for brass drilling. Keeps the drill bit from digging in.

https://www.youtube.com/watch?v=8Ri6poVpQM8

 

[Terrywerm]

That plate might be cast iron, and you may have hit a chilled spot, which can be harder than the average drill bit.

Another thing that helps to keep the drill bit from jamming up in the hole is to make sure you have the work clamped firmly to the table, and to have the work resting on a piece of scrap wood. Additionally, when the drill starts to break through, ease up on the pressure.

Can you take a photo of the cutting edges of your drill bit and post here? At least we can possibly rule out a dull bit.

 

[ericc]

Hi. The plate was supported on two parallels, and clamped with c clamps. This gives me a chance to avoid drilling the table. I don't think that Jet drill press was all that large. It was at Techshop, so it did not have numbers. It looked like the 20" floor model, which is only rated to 5/8" drilling. This drill has no problem at all with 5/8". It seems that the drill bit is getting hung up on ridges. More solid clamping may help, or it can just go straight to the mill. For the square holes, I can just use four or so smaller holes.and mill the waste out.

The material is definitely not cast iron. It makes long spiral chips. I was able to get one 1" hole drilled, but it was iffy. 3/4" step should work fine. I'll give it a try as well.

 

[AGCB97]

I've used annular cutters in all sorts of ways, mill, DP, even handheld cordless. Drill pilot hole the size of the eject pin. If using the mill, don't use the ejector and no pre drill. 1/2" - 2" in the mill no problem.